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J O U R N A L O F C H E M I S T R Y Materials Feature Article Structure formation of functional sheet-shaped mesogens Dietmar Janietz* Research Group T hin Organic L ayers, Potsdam University, Kantstr. 55, D-14513, T eltow, Germany The combination of anisometric sub-units with an additional intramolecular functionality has frequently resulted in the creation of supramolecular systems not only able to form thermotropic mesophases due to their anisotropic molecular shape but also capable of structure formation resulting from their amphiphilic properties and/or from non-covalent intermolecular interactions with complementary components.This article summarizes diVerent examples of this interplay of structure formation tendencies based on functionalized sheet-like liquid crystals. The formation of thermotropic liquid crystalline phases is Mesophase structures usually formed by flat predominantly caused by an anisometric molecular shape1 sheet-shaped molecules and phase manipulation whereas amphiphilic molecules characterized by combined by doping with electron acceptors hydrophilic and lipophilic groups may exhibit lyotropic mesophases in the presence of a solvent2 or two-dimensional It was discovered in 1977 that hexa-n-alkanoyloxybenzene supramolecular assemblies at an air–water interface.3 Yet the derivatives exhibit mesophases with a columnar structure,10 shape of a single molecule is not the only structure controlling and since then a wide variety of liquid crystalline compounds factor.Form-anisotropic aggregates giving rise to mesomorphic of quite diVerent chemical structures have been prepared structure formation can also be formed by specific intermolecu- possessing a flat or nearly flat rigid core surrounded by a lar interactions between identical or diVerent individual mol- specific number of peripheral long chain alkyl substituents ecules.Such attractive interactions may, for example, arise (three to twelve). from ionic structures,4 dipole–dipole interactions,5 hydrogen Several types of mesophases formed by those sheet-like bonding6 or charge transfer eVects.7 molecules have been identified which diVer with respect to the The combination of anisometric sub-units with an additional state of order11 (Fig. 2). The mesophase exhibiting the lowest intramolecular functionality, furthermore, oVers a powerful state of order is the nematic discotic (ND) phase, well estabtool to design molecular architectures which are characterized lished, e.g.for radial multialkynylbenzene derivatives,12 in by the fact that their self-organization results from a complex which the planes of the flat molecules are oriented more or interplay and/or competition of diVerent factors and driving less parallel to each other giving rise to a preferred orientational forces of structure formation.In this way, by creating multi- order of the short molecular axis. functional chemical primary structures, a much greater scope In contrast to the common ND phase, the nematic columnar is oVered for control and manipulation of supramolecular (Ncol) phase is characterized by a columnar stacking of the assemblies than can be achieved with monofunctional molecules.However, these columns do not form two-dimenmesogens. In the case of rod-like mesogens an additional functional sub-unit can be incorporated either along or perpendicular to the main molecular axis.8 The flat molecular geometry of disclike or, more generally, sheet-like9 compounds allows two possibilities to be combined with an additional intramolecular function (Fig. 1). The functional sub-unit can be fixed at one or more positions at the periphery of the molecule via flexible spacers (A) or it can be an integrated part of the rigid central molecular core (B). This paper is concerned with examples of functionalized sheet-like systems of both general structure types A and B, given schematically in Fig. 1, which are not only able to form thermotropic mesophases due to the anisotropic molecular shape but also capable of structure formation resulting from amphiphilic properties and/or from non-covalent intermolecular interactions with complementary components, the latter giving rise to a manipulation or an induction of columnar liquid crystalline phases.However, it is far beyond the scope of the present paper to give a comprehensive overview of this topic. Fig. 1 Multifunctional supramolecular systems by intramolecular com- * E-mail: zetsche@rz.uni-potsdam.de bination of anisometric and functional molecular sub-units J. Mater. Chem., 1998, 8(2), 265–274 265n-alkanoates or hexaalkoxy(acyloxy)triphenylene derivatives, form monolayers at the air–water interface with only a low compressibility.17 It is therefore obvious that those compounds lack distinct amphiphilic properties.A powerful tool towards sheet-like molecules with more pronounced hydrophilic and hydrophobic regions consists of the asymmetrical incorporation of one or two terminal polar substituents at the periphery of an extended core via flexible spacers.In this way it might be possible to combine liquid crystalline behaviour and amphiphilic self-organization within one molecule.18 Members of three families of flat molecules 1a,b, 2a–e and 3a–d are consistent with the general structure type of amphiphilic sheet-shaped compounds given schematically in Fig. 3. Fig. 2 Typical examples of thermotropic mesophases formed by low molar mass or polymeric sheet-like molecules sional lattice structures.They display a positional short range order and an orientational long range order.13 A parallel alignment of the columns results in columnar phases with a two-dimensional lattice symmetry such as columnar hexagonal (Colh), oblique (Colob; not shown in Fig. 2) and rectangular (Colr), the latter usually arising from a tilt of the average molecular plane against the column axis.Furthermore, the molecules may be arranged in a regular ordered manner or, in the case of a liquid-like ordering, aperiodically (disordered) within each column. For example, disc-like mesogens based on the triphenylene core surrounded by six alkoxy substituents usually exhibit a hexagonal columnar ordered (Colho) phase.11,14 Organic compounds containing electron donor units can be doped with acceptor molecules and it is well-established that disc-like electron-rich systems such as triphenylenes and multialkynes form charge-transfer complexes with rather flat but non-liquid crystalline electron acceptors like 2,4,7-trinitro- fluoren-9-one (TNF).15 Donor–acceptor interaction may lead to manipulations as well as the induction of columnar mesophases.The columns are then formed by mixed stacks of the flat donor molecules and the electron acceptor. Charge-transfer (CT) interaction of hexagonal columnar phase-forming hexaalkoxytriphenylenes with TNF results in a stabilization of the already existing mesophase.15b,c Even using non-mesogenic triphenylene derivatives, doping with TNF gives rise to the induction of hexagonal columnar phases.15b Nematic discotic hexaalkynylbenzene compounds were found to exhibit CT-induced Colho liquid crystalline structures15b whereas binary mixtures of non-liquid crystalline pentakis(phenylethynyl)benzene ethers and an electron acceptor were found to form nematic-columnar (Ncol) as well as ordered hexagonal columnar (Colho) structures due to the donor–acceptor interactions.13,16 Considering the donor function as part of the rigid central molecular cores that, apart from the thermal properties of the pure compounds, give rise to control of structure formation through intermolecular CT interactions it follows that radial multiynes and triphenylenes are representatives of functional sheet-like mesogens of the general structure type B (Fig. 1). H11C5O OC5 H11 H11C5O OC5 H11 O O N N N HN NH N N N O (CH2) n X R R R R (CH2) n (CH2) n R R R R R R X X R (CH2)6 OH 1a R = C5H11 b R = (CH2)6OH 2a R = C8H17 X = CO2H n = 3 b R = C10H21 X = CO2H n = 3 c R = C8H17 X = OH n = 6 d R = C6H13 X = OH n = 4 e R = C10H21 X = OH n = 4 3a R = C5H11 X = CO2H n = 10 b R = C5H11 X = OH n = 11 c R = H X = CO2H n = 10 d R = H X = OH n = 11 R Whereas the triphenylene 1a exhibits a hexagonal columnar Low molar mass sheet-like molecules bearing ordered (Colho) phase the two-fold hydroxy terminated com- peripheral polar substituents pound 1b forms a monotropic lamellar LC phase with a well defined double-layer packing of associated pairs of discs (aris- Studies on the spreading behaviour of disc-like liquid crystals have shown that aromatic core systems fitted with a specific ing from partial overlapping of the OH-containing tails) and a local columnar intralayer ordering.19 Doping of 1b with number of equal long aliphatic chains, such as benzene-hexa- 266 J.Mater. Chem., 1998, 8(2), 265–274Fig. 4 Schematical presentation of the molecular edge-on orientation of sheet-shaped amphiphiles bearing terminal polar head groups with (a) columnar ordering parallel to the surface and (b) two-dimensional nematic-discotic (ND) like arrangement. Lateral flexible side groups are not shown, only one hydrophilic function per molecule is presented.dimensional gas phase into the compressed state.21–23 In contrast to oligomers derived from 2c22 the surface pressure–area isotherms of 2a–e show only a small hysteresis during expansion of the monolayers. In the case of sheet-like multialkynylbenzene compounds only the incorporation of terminal hydrophilic substituents (compounds 3) gives rise to amphiphilic properties.Only threedimensional crystallization was described for the radial symmetrical hexakis[(4-hexyl-phenyl)ethynyl]benzene at the air–water interface.27 The p–A isotherms of the hydroxy or Fig. 3 Peripheral attachment of a hydrophilic functional sub-unit to a carboxy terminated pentaynes 3a–d show no phase transition rigid sheet-like molecular part during compression but a direct transition to a solid condensed form.26 Attributed to the presence of only one hydrophilic terminal substituent, the collapse pressure of the pentaynes 3, TNF leads to an enantiotropic charge-transfer-induced hexagonal columnar ordered (Colho) phase.20 however, is relatively low on a pure water subphase.26 The monolayer stability can be enhanced significantly either by Unlike the phthalocyanine dicarboxylic acids 2a,b, especially designed as materials for Langmuir–Blodgett (LB) film fabri- incorporation of a second polar head group as demonstrated for tetraalkynylbenzene derivatives with two neighbouring cation,21 the two-fold hydroxy substituted compound 2c exhibits an enantiotropic columnar phase with a two-dimensional hydrophilic functions attached to the ortho positions of the central benzene ring via flexible spacers28 or by supplementary hexagonal lattice symmetry as bulk material22 whereas the phthalocyanines 2d,e form monotropic columnar phases.23 interactions of the hydrophilic head groups with counterions dissolved in the subphase.29 The pentaalkynylbenzene derivatives 3a,b bearing five lateral pentyl substituents form a nematic-discotic (ND) mesophase The two-dimensional monolayer assemblies of the edge-on oriented sheet-shaped amphiphiles 1–3 can vary from a colum- on both heating and cooling; the appropriate laterally unsubstituted compounds 3c,d are only crystalline materials.24 Charge- nar stacking parallel to the surface25,27 to a nematic–discotic (ND) like arrangement;28 the latter was proved for compounds transfer interaction of the five-fold pentyl-modified pentaynes 1a,b with TNF results in the induction of hexagonal columnar 3.The monolayer arrangements presented schematically in Fig. 4, which are quite diVerent from those of classical amphi- ordered (Colho) mesophases whereas the lateral unsubstituted penaalkynes 3c,d form a CT-induced nematic columnar (NCol) philes, may not only arise from decreasing the available area per molecule during the compression process but also arise phase in mixtures with TNF.24 This behaviour agrees well with the thermal properties of radial hexaalkynylbenzene derivatives from a spontaneous aggregation of the edge-on oriented molecules immediately after spreading resulting in condensed and pentakis(arylethynyl)phenyl ethers without a terminal polar functionality.12,13,16 It indicates that it is not the incorpor- monolayer islands which are pushed together during compression.28,30 ated polar function but the lateral substitution pattern that determines the liquid crystalline structure formation of the Successful attempts to prepare LB multilayers have been reported for members of all three series of non-classical amphi- pentaynes 3a–d.All sheet-like systems 1–3 functionalized by one or two philes 1–3 (triphenylenes 1,19,20,31 phthalocyanines 2,21–23,33 pentaynes 326,29,32).polar terminal groups form monolayers on a pure water subphase.21–23,25,26 It is a common feature that, independent It is common for all amphiphiles 1–3 that dipping of a hydrophobic substrate through the compressed monolayer of the diVerent chemical structures of the flat, sheet-like cores, the average areas per molecule in the compressed monolayers results in transfer of a monolayer each time the substrate passes the surface boundary.During first immersion the first of the compounds 1–3 are less than the area requirement for the central molecular parts lying flat on the water surface. monolayer is transferred so that the hydrophobic rigid cores face the substrate surface.A second monomolecular layer with However, the collapse areas agree quite well with an edge-on arrangement27 of the compounds 1–3 with a molecular orien- the disc-shaped cores in the opposite direction is formed on top of the first monolayer during withdrawal of the substrate tation of the plane of the rings more or less perpendicular to the water (Fig. 4). [Fig. 5(a)].The edge-on orientation of the amphiphiles at the air–water interface is preserved during the formation of the The peripheral attachment of just one or two hydroxy groups to the triphenylene core (compounds 1a,b) leads to LB films. This Y-type deposition gives rise to a bilayer packing of the molecules perpendicular to the substrate (head-to-head monolayers with higher collapse pressures compared to those of symmetrically substituted members such as hexapentyloxy- and tail-to-tail arrangement of molecular monolayers).Further structural characteristics of LB films made from triphenylene.25 The behaviour of the hydroxy substituted phthalocyanines compounds of the series 1–3 other than those mentioned above are not uniform. For example, the mesomorphic double-layer 2c–e at the air–water interface is very similar to the structurally related two-fold carboxy terminated compounds 2a,b.During structure of the two-fold hydroxy terminated triphenylene 1b is preserved during the formation of the LB multilayers with compression a sharp increase in the surface pressure–area isotherms is observed indicating a transition from the two- a columnar ordering parallel to the solid support and the J.Mater. Chem., 1998, 8(2), 265–274 267Fig. 5 Langmuir–Blodgett (LB) multilayers of sheet-shaped molecules asymmetrically incorporating hydrophilic substituents. (a) Fabrication of the LB films; (b) schematic presentation of the two-dimensional structure for the single component LB film derived from the amphiphilic pentayne 3b (refs. 26,29). periodicity of the rectangular lattice relative to the normal determined by the distance between next nearest pairs of edge- Fig. 6 Modes of structure formation of functional sheet-shaped meso- on oriented molecules.19 The bilayer spacings observed for the gens as an outcome of amphiphilic properties, anisometric molecular LB films of the phthalocyanines 2a,b are less than the calculated shape and intermolecular donor–acceptor interactions molecular dimensions that might be explained by a tilt of the planes of the molecules from the normal or by an interdigitation of chains in adjacent layers.21 The pentaynes 1a,b form Y-type bilayers with edge-on orientation of the discs.The main molecular axis of the molecules is tilted against the normal of the surface.The flexible molecular segments of neighbouring molecules are interdigitated26,29 (Fig. 5). A hexagonal layer packing perpendicular to the surface proved to be possible in the LB films of the laterally unsubstituted pentaalkynyl carboxylic acid 3c without lateral substituents.26,30 Fig. 6 illustrates the richness of supramolecular assemblies of functionalized disc-like mesogens such as 1–3 arising from the combination of a hydrophilic sub-unit with a flat hydrophobic anisometric core, the latter oVering the opportunity to be combined with an additional donor function.Functional polymers bearing disc-shaped side groups Compared with calamitic polymers, the variety of polymers incorporating disc-shaped units, predominantly based on the triphenylene core, is rather limited.Triphenylene main chain polymers are usually either non-mesomorphic or exhibit hexagonal columnar (Colho) phases.34 Attaching triphenylene groups to polysiloxane, polyacrylate, polymethacrylate or polyester backbones, respectively, gives rise to triphenylene side chain Fig. 7 Molecular architecture of functional polymers attached with polymers which, depending on the chemical nature of the main sheet-shaped side groups chain and/or the spacer length, were found to be amorphous or to form columnar mesophases with either hexagonal or rectangular lattices.35 Doping of non-mesogenic triphenylene have been described capable of forming highly ordered LB multilayers.19,20,31 polymers induces either nematic-columnar (Ncol; side chain polymers) or hexagonal columnar ordered (Colho; main chain An eVective approach towards controlling supramolecular structures at interfaces as well as in the mesomorphic bulk polymers) mesophases.36 Apart from investigations on thermal properties a few examples of polymeric triphenylene derivatives state involves the attachment of sheet-like sub-units to a 268 J.Mater. Chem., 1998, 8(2), 265–274functional hydrophilic backbone having the tendency to form associated structures via complementary hydrogen bonding.This requires the combination of anisometric structural elements with a flexible polymer chain and with an additional functional sub-unit. This concept outlined schematically in Fig. 7 was realized recently by the synthesis of oligomers characterized by the attachment of either triphenylene (4a,b) or pentaalkyne (5a,b) side groups to amino substituted 1,3,5-triazine moieties in the backbone.37 Fig. 8 Model for molecular bilayer arrangement of the triphenylene oligomers 4 in LB multilayers and in the mesomorphic bulk state; flexible lateral alkyl chains are not shown These restrictions disturb closest face-to-face intracolumnar packing and favour the interdigitation of triphenylene groups belonging to diVerent backbones.38b With the exception of the laterally unsubstituted pentayne 5b the triazine oligomers exhibit an enantiotropic mesophase in the bulk.The structure displayed by the oligomers with disc-like side groups corresponds to a smectic A like arrangement, which is highly surprising.37 The magnitude of the layer dimensions indicates that no single-layer arrangement takes place but rather a double-layer one (Fig. 8). The double-layer structure is stabilized by the formation of hydrogen bonds between the aminotriazine segments of the polymer backbone. It is thus apparent that the interactions between the backbone segments frustrate the structure preferred by the disc-like units.The molecular dimensions of the LB films and the doublelayer spacing within the mesomorphic bulk state of the triphenylene oligomer 4a are very close. This implies that the layer structure in the bulk LC state is preserved during the formation of the LB films on the solid substrate although the two mechanisms of structure formation are quite diVerent.38a Doping of the triphenylene oligomer 4b with the acceptor TNF results in the induction of a rectangular columnar (Colrd) mesophase.No such strong eVect was found for the doped compound 4a characterized by the longer spacer. The meso- OC5H11 OC5H11 O H11C5O (CH2)m O N N N NH HN (CH2)6 OC5H11 H11C5O n 4a m = 11 b m = 6 O (CH2)11 O R R R R N N N NH HN (CH2)6 5a R = C5H11 b R = H R n genic organization of mixtures from 4a and TNF remains a lamellar layer structure.Thus, the mesophase arrangements of All oligomers 4 and 5 form stable monolayers when spread the donor–acceptor complexes are a function of the spacer on the water surface.37 The collapse areas of the triphenylene connecting the triphenylene side groups with the main chain.37 oligomers 4 and of the oligomeric pentaynes 5 are close to However, the rectangular lattice spacings (4b/TNF) as well as those of the respective hydroxy- or carboxy-terminated monthe double-layer dimensions (4a/TNF) indicate that the struc- omers 1 and 3.This indicates an edge-on orientation of the ture formation of the binary mixtures result from both, inter- hydrophobic triphenylene or pentaalkyne side groups for each molecular charge-transfer interactions and intermolecular triazine oligomer 4 and 5 while the amino substituted triazine hydrogen bonding.rings serve as anchor groups at the water surface. It follows that the structures displayed by the functional The amphiphilic triphenylene 4a, furthermore, has been triazine based oligomers 4 and 5 are the result of a delicate reported to form LB films with a bilayer packing of edge-on balance of interactions which may compete with each other oriented triphenylene groups (Y-type deposition) and with (Fig. 9).interdigitation of the flat cores.38 The structural model given in Fig. 8 displays columnar in-plane packing where alternate triphenylene group belongs to a diVerent backbone and the Covalently linked donor–acceptor twin mesogens orientations of adjacent disc-shaped groups are alternating.based on flat electron-rich donor sub-units This type of columnar structure is caused by spacial restrictions imposed by exceeding the distance between chemical attach- Charge-transfer interactions of two individual molecules each incorporating either a donor or an acceptor function, in the ments of the neighbouring sheet-like cores along the backbone.J. Mater. Chem., 1998, 8(2), 265–274 269Fig. 10 Covalently linked charge transfer twin mesogens based on flat donor and acceptor sub-units spacers of diVerent length.39 Keeping the spacer length constant, structural modifications were performed at the lateral sphere of the pentayne units of compounds 7 in order to influence the magnitude of the molecules and thus the eYciency Fig. 9 Interplay of diVerent driving forces to control the structure of expected intermolecular charge transfer interactions.40 The formation of the 1,3,5-triazine based triphenylene and pentaalkyne twin molecules 8 incorporate an asymmetric carbon as an oligomers 4 and 5 additional intramolecular functionality.41 The mesophase structure of the triphenylene based CT-twin compounds 6 is characterized by an arrangement of the case of sheet-shaped triphenylene ethers or radial multialkynylmolecules in columns in such a way that mixed stacks occur.benzene derivatives as the donor molecules, give rise to a Each column is connected in one direction with two neighbour- manipulation or an induction of columnar mesophases. The ing columns chemically via the flexible spacers.The intercolum- columnar phases, then, are usually of the hexagonal or nematicnar packing has been described as possessing an orthorhombic columnar type. symmetry with ab (for compound 6a) or in case of compound However, the components need not necessarily be derived 6b as displaying either an orthorhombic lattice with tilted from separated molecules but from mesogens which incorporplanes of the discs or as a hexagonal two-dimensional ate both donor and acceptor functions into a single molecule.structure.39 Such an approach consists of a chemical linkage of a flat The donor–acceptor molecules 7 based on sheet-like penta- anisometric phase forming moiety with an acceptor functional alkynes exhibit a rectangular columnar phase with a=b and sub-unit via a flexible spacer.This concept has been realized with a high intracolumnar periodicity resulting from closely by coupling of electron-rich triphenylene (6) or pentayne (7,8) face-to-face arranged alternating donor and acceptor moieties units and electron-poor trinitrofluorenones (Fig. 10). of the molecules.41 Whereas the molecules in the columns are connected through charge-transfer interactions, the chemical linkage of the donor and acceptor sub-units facilitates the intercolumnar packing.These special features give rise to a three-dimensional order, at least in the case of compound 7a41 (Fig. 11). Thus, it is not the chemical nature of the donor molecular moieties but the linkage with an intramolecular acceptor functionality that dominates the structure formation of the charge-transfer twin mesogens 6 and 7, e.g.the formation of rectangular symmetries of intercolumnar packing instead of common hexagonal or nematic-columnar. A further approach towards control of mesomorphic structures of sheet-shaped CT-twin mesogens arises from chirality as an additional intramolecular function. Preliminary structure investigations give rise to the conclusion that the twin compounds 8 incorporating an asymmetric carbon exhibit a nematic-columnar mesophase with a helical twisting of the columns.41,42 O OC5H11 OC5H11 H11C5O OC5H11 H11C5O (CH2)6 O (CH2)2 O O N NO2 NO2 NO2 O R R R (CH2)11 O X O N O NO2 Y NO2 NO2 R R 6a n = 0 b n = 1 7a–c X = (CH2)2 Y = H R = H (7a), R = CH3 (7b) R = C5H11 (7c) 8a–c X = C*HCH3 Y = NO2 R = H (8a), R = CH3 (8b) R = C5H11 (8c) n The triphenylene based CT-twin molecules 6 are charac- Fig. 11 Structure model of the rectangular columnar mesophase of the pentayne based donor–acceptor twin mesogens 7 terized by connecting the donor and acceptor moieties via 270 J. Mater. Chem., 1998, 8(2), 265–274Functional heterocyclic azacoronands and 1,3,5- triazines Suitably substituted N-acylated macrocyclic oligoamides, e.g. 9–12, diVering in the heterocyclic ring size as well as in the number of nitrogen atoms incorporated into the saturated central cores have been found to exhibit thermotropic hexagonal columnar mesophases.43 The central cavity in the columns led to these phases being described as tubular.43a Fig. 12 Schematic presentation of the side-on arrangement of sheetlike amphiphiles with a polar central core surrounded by a certain number of hydrophobic alkyl chains Fig. 13 1,3,5-Triazines as central parts of functional sheet-shaped molecules with open-sided cores ethers, radial multiynes) as well as in the case of ‘hollow’ core systems (azacrowns) gives rise to manipulations of as well as the induction of columnar mesophases due to specific intermolecular interactions (charge-transfer complex formation, metal complex formation).However, these functionalities do not N N N N N N X R X R X R X R X R X R 9 X = CO; R = 10 X = CO; R = 11 X = CO; R = OC12H25 OC14H29 OC10H21 OC10H21 N N X R X R N N X R X R 12 X = CO; R = OC10H21 OC10H21 allow side-by-side interactions with a complementary component.In contrast to macrocyclic amides such as compounds 9–12 Such an approach may consist of ‘open-sided’ core systems alkyl-substituted azacrowns show no mesophase behaviour due having the capacity to form columnar mesophases as single to an increased conformational flexibility of the ring system. components but also enabling control of structure formation However, complexation of transition metal salts by highly by a peripheral attack of a second component to the inner flexible benzyl substituted cyclic amines bearing a certain (functional) core region (Fig. 13). number of peripheral long alkoxy chains (for example, 10 and 12; X=CH2 instead X=CO) gives rise to the induction of columnar liquid crystalline phases.44 Coordination to the metal ions (e.g. Cu2+, Ni 2+ or Co3+) imposes the desired conformational rigidity of the functional central macrocyclic rings.In this way, the sheet-like molecular geometry of azacrowns and the complex formation properties of macrocyclic ligands, leading to specific host–guest systems, can be combined.44a The polar central core of cyclic azacoronands fitted with long lipophilic hydrocarbon chains gives rise to azamacrocycles with distinct amphiphilic properties.Beside the benzoyl substituted compounds 9 and 10 certain acylated43b,45 and alkylated46 hexacyclene and cyclam derivatives have been shown to form stable monolayers at the air–water interface. The arrangement of either amine or amide derivatized azacrowns, in general, is the same at the interface.46 Within the monolayer the molecules adopt an orientation in which the hydrophilic OR OR N H N N N N RO RO N H OR OR H 13a R = C10H21 R = C12H25 R = C16H33 b c macrocycle lies flat on the water surface (side-on arrangement).In the condensed state the hydrophobic alkyl chains are Following this concept, recently the 2,4,6-triarylamino-1,3,5- triazines 13 have been prepared bearing six long peripheral oriented more or less perpendicular to the interface in a closepacked all-trans conformation (Fig. 12). alkoxy chains. The melamines 13 form enantiotropic columnar mesophases Combining a flat anisometric molecular shape with an intramolecular functionality located in the central core region although they are characterized by a lack of inherent molecular planarity.47 In the case of the heterocyclic mesogens 13a,b the in the case of ‘closed’ aromatic core systems (triphenylene J.Mater. Chem., 1998, 8(2), 265–274 271columns are arranged in a hexagonal array with an aperiodic Furthermore functional units embedded in the central cores, in certain cases, give rise to an induction of mesomorphic intracolumnar stacking of the molecules (Colhd). Further elongation of the lateral alkyl chain length results in a major properties by metal complexation of azacoronands whereas molecular recognition due to intermolecular hydrogen bonding structural change.Compound 13c exhibits the rarely observed ordered rectangular columnar (Colro) phase. allows control of the hexagonal lattice constants as well as variation of the two-dimensional lattice type of the columnar- The mesomorphic triarylmelamines are characterized by a heterocyclic 1,3,5-triazine core with a three-fold substitution phase-forming triarylmelamines (Fig. 14). with secondary amino groups promoting attractive interactions with complementary functional molecules via intermolecular hydrogen bonding (side-by-side attack). Outlook Binary mixtures of the melamine 13a with non-mesogenic The few examples discussed here may show that it is possible 3,5-dialkoxy substituted benzoic acids exhibit a hexagonal to combine molecular sub-units of a flat sheet-like anisometric columnar disordered (Colhd) phase at least at an equimolar shape with an additional intramolecular functionality in vari- ratio of the components. The intercolumnar distances are a ous ways.Functional disc-like systems can result that combine function of the length of the alkoxy groups of the acid structure forming tendencies due to amphiphilic properties and component.48 A 3,4-dialkoxy substitution pattern of the benthose arising from an anisometric molecular geometry within zoic acid gives rise to a change of the columnar mesophase one molecule. The intramolecular function, furthermore, may structure of the melamine 13a from a hexagonal to a rectanguallow control of and/or induction of supramolecular (columnar) lar lattice (Colrd) in binary mixtures with the aromatic acids.48 structures by non-covalent interactions with complementary Equimolar mixtures of the melamines 13 and 4-alkoxybenzoic components.However, those intramolecular functionalities acids exhibit a hexagonal columnar disordered (Colhd) strucpresented here usually do not facilitate reversible control of a ture.49 In the case of the melamine 13a the hexagonal lattice supramolecular assembly once obtained either in single compo- constants increase with increasing number of methylene groups nent or mixed multicomponent systems. They might therefore of the para-alkoxy substituted benzoic acid component.49 The be considered as functions of the first generation.appearance of a calamitic phase characteristic of 4-alkoxyben- Reversible control of columnar structures, such as gener- zoic acids in their pure state, due to a dimerization of the ation, manipulation and destruction, might be possible by acids, is not observed.Hence, associations with the aminotriazcombining a disc-shaped molecular part, probably already ines 13 completely frustrate the tendency of the aromatic acids incorporating a function of the first generation, with an to form dimers. additional reversibly switchable sub-unit (function of the Furthermore, the triarylmelamines 13 are characterized by second generation). a polar central heterocyclic core and long non-polar alkoxy Compounds 14 are the first representatives of CT-triple side chains.Amphiphilic properties arise from this combination molecules consisting of a sheet-like pentayne donor and a of diVerent structure elements and the triazines 13 form TNF based acceptor which are covalently linked via a rod- monolayers on the water surface. Similarly, as found for like sub-unit incorporating an azobenzene moiety (Fig. 15). amphiphilic azamacrocycles a molecular side-on arrangement The compounds exhibit a nematic mesophase at elevated is observed with the amino modified triazine ring as the most temperatures and form a glassy state at room temperature.41 hydrophilic molecular part lying flat47 (Fig. 12). It seems possible to combine here the structure formation of Thus, azamacrocycles and 1,3,5-triazines bearing long alidisc- like donor–acceptor twin mesogens with the ability of the phatic side chains are two classes of sheet-like molecules possessing both mesomorphic and amphiphilic behaviour.azo group present in the spacer to be switched by light. Fig. 14 Aspects of mesomorphic structure formation of functional azacrowns and triarylmelamines 272 J.Mater. Chem., 1998, 8(2), 265–274O R R R (CH2)11 R R O CO N N O CO (CH2)2 O N NO2 O2N O2N 14 R = H, CH3 B. Kohne, K. Praefcke, H. Ringsdorf, J. H. WendorV and R. Wu� stefeld, Adv. Mater., 1990, 2, 141; (c) M. Ebert, G. Frick, C. Baehr, J. H. WendorV, R. Wu� stefeld and H. Ringsdorf, L iq. Cryst., 1992, 11, 293. 16 K. Praefcke, D. Singer, M.Langner, B. Kohne, M. Ebert, A. Liebmann and J. H. WendorV, Mol. Cryst. L iq. Cryst., 1992, 215, 121. 17 O. Albrecht, W. Cumming, W. Kreuder, A. Laschewsky and H. Ringsdorf, Coll. Polym. Sci., 1986, 264, 659. 18 H. Ringsdorf, B. Schlarb and J. Venzmer, Angew. Chem., 1988, 100, 117. 19 O. Karthaus, H. Ringsdorf, V. V. Tsukruk and J. H. WendorV, L angmuir, 1992, 8, 2279. Fig. 15 Donor–acceptor triple mesogens incorporating an additional 20 V. V. Tsukruk, J. H. WendorV, O. Karthaus and H. Ringsdorf, calamitic functional sub-unit L angmuir, 1993, 9, 614. 21 (a) M. J. Cook, M. F. Daniel, K. J. Harrison, N. B. McKeown and A. J. Thomson, J. Chem. Soc., Chem. Commun., 1987, 1148; The author appreciates very much the colleagues and co- (b) N. B. McKeown, M. J. Cook, A.J. Thomson, K. J. Harrison, workers mentioned in the references cited here for their activi- M. F. Daniel, R. M. Richardson and S. J. Roser, T hin Solid Films, ties and contributions. Special thanks are due to K. Praefcke, 1988, 159, 469; (c) J. Cook, N. B. McKeown, J. M. Simmons, H. Ringsdorf and J. H. WendorV for many helpful discussions. A. J. Thomson, M. F. Daniel, K. J.Harrison, R. M. Richardson The Deutsche Forschungsgemeinschaft is gratefully acknowl- and S. J. Roser, J.Mater. Chem., 1991, 1, 121. 22 G. C. Bryant, M. J. Cook, C. Ruggiero, T. C. Ryan, A. J. Thorne, edged for financial support. S. D. Haslam and R.M. Richardson, T hin Solid Films, 1994, 243, 316. 23 R. H. Poynter, M. J. Cook, M. A. Chester, D. A. Slater, J. McMurdo and K. Welford, T hin Solid Films, 1994, 243, 346. References 24 D.Janietz, K. Praefcke and D. Singer, L iq. Cryst., 1993, 13, 247. 1 D. Demus, L iq. Cryst., 1989 5, 75. 25 O. Karthaus, H. Ringsdorf and C. Urban, Makromol. Chem., 2 H. Kelker and R. Hatz, Handbook of L iquid Crystals, Verlag Macromol. Symp., 1991, 46, 347. Chemie, Weinheim-Deerfield, Florida, Basel, 1980. 26 D. Janietz, D. Hofmann and J.Reiche, T hin Solid Films, 1994, 3 G. L. Gaines, Insoluble Monolayers at L iquid-Gas Interfaces, Wiley 244, 794. Interscience, New York, 1966. 27 A. Laschewsky, Adv.Mater., 1989, 101, 1606. 4 (a) J. Lindau, H. J. Ko�nig and H.-D. Do� rfler, Colloid Polym. Sci., 28 D. Janietz, R. C. Ahuja and D. Mo� bius, L angmuir, 1997, 13, 305. 1983, 261, 236; (b) M. Veber, P. Sotta, P.Davidson, A.-M. Levelut, 29 (a) J. Reiche, R. Dietel, D. Janietz, H. Lemmetyinen and C. Jallabert and H. Strzelecka, J. Phys., Paris, 1990, 51, 1283. L. Brehmer, T hin Solid Films, 1993, 226, 265; (b) A. Angelova, 5 (a) C.S.Oh, Mol. Cryst. L iq. Cryst., 1977, 42, 1; (b) W. H. deJeu, J. Reiche, R. Ionov, D. Janietz and L. Brehmer, T hin Solid Films, L. Longa and D. Demus, J. Chem.Phys., 1986, 84, 6410. 1994, 242, 289. 6 C. M. Paleos and D. Tsiourvas, Angew. Chem., 1995, 107, 1839 30 J. Reiche, D. Janietz, T. Baberka, D. Hofmann and L. Brehmer, 7 (a) K. Araya and Y. Matsunaga, Bull. Chem. Soc. Jpn., 1980, 53, Nucl. Instrum.Methods Phys. Res., Sect. B, 1995, 97, 419. 3079; (b) Y. Matsunaga, N. Kamiyama and Y. Nakayasu, Mol. 31 M. V. d. Auweraer, C. Catry, L.Feng Chi, O. Karthaus, W. Knoll, Cryst. L iq. Cryst., 1987, 147, 85; (c) N. K. Sharma, G. Pelzl, H. Ringsdorf, M. Sawodny and C. Urban, T hin Solid Films, 1992, D. Demus and W.Weissflog, Z. Phys. Chem., 1980, 261, 579. 210/211, 39. 8 (a) F. Hildebrandt, J. A. Schro� ter, C. Tschierske, R. Festag, 32 A. Jutila, D. Janietz, J. Reiche and H. Lemmetyinen, T hin Solid R. Kleppinger and J.H. WendorV, Angew. Chem., 1995, 107, 1780; Films, 1995, 268, 121. (b) J. A. Schro� ter, R. Plehnert, C. Tschierske, S. Katholy, D. Janietz, 33 For a review, see for example, (a) A. W. Snow and W. R. Barger, in F. Penacorada and L. Brehmer, L angmuir, 1997, 13, 796. Phthalocyanines: Properties and Applications, ed. C. C. LeznoV and 9 K. Praefcke and J. D. Holbrey, J. Inclusion Phenom.Mol. Recog. A. B. P. Lever, VCH Publishers, New York, 1989; (b) A. Ulman, Chem., 1996, 24, 19. An Introduction to Ultrathin Films: from L angmuir–Blodgett to 10 S. Chandrasekhar, B. K. Sadashiva and K. Suresh, Pramana, 1977, Self-Assembly, Academic Press, San Diego, 1991. 9, 471. 34 (a) W. Kreuder, H. Ringsdorf and P. Tschirner, Makromol. Chem., 11 C. Destrade, P. Foucher, H. Gasparoux, Nguyen Huu Thin, Rapid Commun., 1985, 6, 367; (b) G.Wenz,Makromol. Chem., Rapid A.M. Levelut and J. Malthete, Mol. Cryst. L iq. Cryst., 1984, 106, Commun., 1985, 6, 577. 121. 35 M. Werth and H. W. Spiess, Makromol. Chem., Rapid Commun., 12 (a) B. Kohne and K. Praefcke, Chimia, 1987, 41, 196; 1993, 14, 329. (b) K. Praefcke, B. Kohne and D. Singer, Angew. Chem., 1990, 102, 36 H.Ringsdorf, R. Wu� stefeld, E. Zerta, M. Ebert and J. H. WendorV, 200; (c) K. Praefcke, B. Kohne, D. Singer, D. Demus, G. Pelzl and Angew. Chem., 1989, 101, 934. S. Diele, L iq. Cryst., 1990, 7, 589; (d) K. Praefcke, B. Kohne, 37 D. Janietz, R. Festag, C. Schmidt and J. H. WendorV, L iq. Cryst., B. Gu�ndogan, D. Singer, D. Demus, S. Diele, G. Pelzl and 1996, 20, 459.U. Bakowsky, Mol. Cryst. L iq. Cryst., 1991, 198, 393. 38 (a) D. Janietz, R. Festag, C. Schmidt, J. H. WendorV and 13 K. Praefcke, D. Singer, B. Kohne, M. Ebert, A. Liebmann and V. V. Tsukruk, T hin Solid Films, 1996, 284–285, 289; J. H. WendorV, L iq. Cryst., 1991, 10, 147. (b) V. V. Tsukruk and D. Janietz, L angmuir, 1996, 12, 2825. 14 C. Destrade, M. C. Mondon and J. Malthe�te, J. Phys., 1979, 40, C3. 39 M. Mo� ller, V. V. Tsukruk, J. H. WendorV, H. Bengs and H. Ringsdorf, L iq. Cryst., 1992, 12, 17. 15 (a) For a review, see ref. 9; (b) H. Bengs, M. Ebert, O. Karthaus, J. Mater. Chem., 1998, 8(2), 265–274 27340 D. Janietz, Chem. Commun., 1996, 713. S. Schmidt, R. Kleppinger and J. H. WendorV, Adv. Mater., 1992, 4, 30. 41 P. Busch, C. Schmidt, A. Stracke, J. H. WendorV, D. Janietz and S. Mahlstedt, Proc. 26. Freiburger Arbeitstagung Flu�ssigristalle, 45 J. Malthe�te, D. Poupinet, R. Vilanove and J.-M. Lehn, J. Chem. Soc., Chem. Commun., 1989, 1016. 1997, P61. 42 Inductions of chiral mesophases by complexation of triphenylene 46 C. Mertesdorf, T. Plesnivy, H. Ringsduir, 1992, 8, 2531. derivatives and pentaalkynylbenzene compounds with a chiral TNF derivative: (a) M. M. Green, H. Ringsdorf, J. Wagner and 47 D. Goldmann, D. Janietz, R. Festag, C. Schmidt and J. H. WendorV, L iq. Cryst., 1996, 21, 619. R. Wu� stefeld, Angew. Chem., 1990, 102, 1525; (b) K. Praefcke, D. Singer and A. Eckert, L iq. Cryst., 1994, 16, 53. 48 D. Goldmann, R. Dietel, D. Janietz, C. Schmidt and J. H. WendorV, L iq. Cryst., 1997, in the press. 43 (a) J.-M. Lehn, J. Malthe�te and A. M. Levelut, J. Chem. Soc., Chem. Commun., 1985, 1794; (b) C. Mertesdorf and H. Ringsdorf, L iq. 49 D. Janietz, D. Goldmann, R. Dietel, C. Schmidt and J. H. WendorV, Proc. 26. Freiburger Arbeitstagung Flu�ssigkristalle, Cryst., 1989, 5, 1757; (c) G. Lattermann, L iq. Cryst., 1989, 6, 619; (d) G. Lattermann,Mol. Cryst. L iq. Cryst., 1990, 182B, 299. 1997, P60. 44 (a) A. Liebmann, C. Mertesdorf, T. Plesnivy, H. Ringsdorf and J. H. WendorV, Angew. Chem., 1991, 103, 1358; (b) G. Lattermann, Paper 7/04902A; Received 9th July, 1997 274 J. Mater. Chem., 1998, 8(2), 265–274J. Mater. Chem., 1998, 8(2), 265–2

ISSN:0959-9428    

DOI:10.1039/a704902a

出版商:RSC    

年代:1998

数据来源: RSC

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J O U R N A L O F C H E M I S T R Y Materials Communication New 1,3-oxathiane type ionic liquid crystal compounds Yuichiro Haramoto,*a Yoshiharu Akiyama,a Ryouichi Segawa,a Seiji Ujiieb and Masato Nanasawaa aDepartment of Applied Chemistry and Biotechnology, Yamanashi University, T akeda 4, Kofu 400, Japan bDepartment of Chemistry, Shimane University, Nishikawatu,Matsue 690, Japan New pyridinium type thermotropic ionic liquid crystal materials having a 1,3-oxathiane ring in the central core, Nethyl- 4-(5-alkyl-1,3-oxathian-2-yl)pyridinium bromides 8, were synthesized.These compounds exhibited a smectic A phase over a very wide range including room temperature (for example 8c: G-30 SA 21 I). There are not many reports concerning ionic thermotropic liquid crystal compounds having two rings in the central core.Some liquid crystal polymers with pyridinium side chains1 and N-alkylpyridinium halides have been reported,2–4 as have stilbazole (styrylpyridine) type metal-containing liquid crystals. 5 On the other hand, we have studied 1,3-dioxane, 1,3- oxathiane and 1,3-dithiane type new liquid crystal materials. 6–15 Ionic liquid crystal materials having these structures in the central core have not been encountered to date and their possibilities as liquid crystal materials are interesting.In the last year the first of these compounds with a 1,3-dioxane R OH OH R Br OH R Br Br R SH OH R SH SH H2N S NH2 N S O R N+ S O R N H O R¢ PBr3 + Alkali R¢Br CH3CN R = C10H21, C11H23, R¢ = C2H5, CH2CH Br– 1 2 3 5 4 4 + 6 7 H+ 7 8 CH2 structure was reported.16 We wish to report a new system of Scheme 1 pyridinium type ionic liquid crystal compounds having a 1,3- oxathiane ring in the principal structure. of a micro-melting point apparatus equipped with polarizers, a diVerential scanning calorimeter (DSC), and X-ray diVraction.Phase transition temperatures for compounds 8 are given in Table 1. S O N R R¢ + Br– 8 N-Alkyl-4(5-alkyl-1,3-oxathian-2-yl)pyridinium bromides 8 were synthesized by the route shown in Scheme 1.In the bromination of compounds 1, both mono- and di-bromides were produced. This mixture was used for the syntheses of compounds 4 and 5. The monothiol 4 and dithiol 5 were N+ S O R R¢ Br– 8 N+ O O R R¢ Br– 9 Table 1 Phase transition temperatures for compounds 8 and the separated by column chromatography, in which 4 and 5 were corresponding 1,3-dioxanes 9 eluted with diethyl ether and hexane, respectively.In the syntheses of compounds 7, both trans and cis isomers were phase transition produced which diVered at the C-5 position of the 1,3-oxathiane R R¾ temperatures/°Ca ring. Repeated recrystallizations were required to obtain only the trans isomers.In the 1H NMR spectra for compounds 7, 8a C10H21 C2H5 K 45 SA 166 I 8b C11H23 C2H5 K 50 SA 192 I the C-2 proton signals for the trans and cis isomer are at 5.75 8c C10H21 CH2CHNCH2 G -30 SA 21 I and 5.80 ppm, respectively. Therefore, removal of the cis isomer 9a C10H21 C2H5 G -24 SA 152 I can be checked by the disappearance of its peak in the 9b C11H23 C2H5 G -9 SA 181 I 1H NMR spectrum.On N-alkylation, 1H NMR signals for the 9c C10H21 CH2CHNCH2 pyridinium proton and the C-2 proton of the 1,3-oxathiane ring were shifted downfield about 0.8 and 0.45 ppm, respectively. The purity of compounds 8 was checked by 1H NMR G I SA –19 62 78 spectroscopy and elemental analyses. Good data were obtained for these compounds. To determine the existence of liquid aK: Crystal, G: Glass, SA: Smectic A, I: Isotropic.crystal phases, observation was performed using a micromelting point apparatus equipped with polarizers. Compounds 8 exhibited a liquid crystal phase, so further detailed measure- Observation of the textures indicates that these compounds exhibited a smectic A phase. To confirm this result, conoscopic ments were made. Measurement of transition temperatures and assignment of the mesophases were carried out by means figures and X-ray diVraction were measured for the phase of J.Mater. Chem., 1998, 8(2), 275–276 275compound 8a (Fig. 1). These results also support the assignment of the liquid crystal phase as smectic A. That is, a uniaxial conoscopic figure was observed, and the diVraction pattern of the typical smectic A phase was also obtained.The sharp peak in the small-angle region indicates that the layer spacing of this phase is 38.9 A ° . This value is somewhat larger than that of the corresponding 1,3-dioxane type ionic liquid crystal compound (34.3 A ° ). From the value of the layer spacing and the peculiar properties of ionic liquid crystal compounds, the molecular arrangement in the smectic A phase may be as shown in Fig. 2. In this model, cationic pyridinium ions and Fig. 1 X-Ray diVraction pattern of the smectic phase of compound 8a anionic bromide ions stabilize each other, and the long alkyl chains orient to form the smectic phase. The temperature of the isotropic to mesophase transition of compound 8c having a terminal double bond is lower than those of compounds 8a or 8b.This is the same tendency as that observed for 1,3-dioxane type compounds (Table 1). The compound having a (CH2)8CHNCH2 group instead of the C10H21 group of compound 9a also exhibited a lower isotropic to mesophase transition temperature.16 Generally, the transition temperatures of the isotropic to mesophase transition tend to be decreased by the existence of a terminal double bond in the molecule.17,18 Therefore, this eVect seems to originate in the presence of the terminal double bond.The most remarkable feature of these new ionic liquid crystal materials is that they exhibit a liquid crystal phase over a very wide range including ordinary room temperature (e.g. 8c: G -30 SA 21 I). We would like to express our gratitude to the director Dr A.B. Holmes, Dr S. C. Moratti and all the members of the Melville Laboratory, University of Cambridge, for extensive support. References 1 V. Hessel and H. Ringdorf, Makromol. Chem. Rapid Commun., 1993, 14, 707. 2 C. G. Bazuin, D. Guillon, A. Skoulion and J. F. Nicoud, L iq. Cryst., 1986, 1, 181. 3 D. N. Rodriguez, Y. Frere, P. Gramain, D. Guillon and A. Skoulios, L iq.Cryst., 1991, 9, 321. 4 D. Navarro-Rodriguez, Y. Frere and P. Gramain, Makromol. Chem., 1991, 192, 12, 2975. 5 J. P. Rourke, F. P. Fanizzi, N. J. S. Salt, D. W. Bruce, D. A. Dunmur and P. M. Maitlis, J. Chem. Soc., Chem. Commun., 1990, 229. 6 Y. Haramoto and H. Kamogawa, J. Chem. Soc., Chem. Commun., 1983, 75. 7 Y. Haramoto, A. Nobe and H. Kamogawa, Bull. Chem. Soc. Jpn., 1984, 57, 1966. 8 Y. Haramoto and H. Kamogawa, Chem. L ett., 1985, 79. 9 Y. Haramoto and H. Kamogawa, Bull. Chem. Soc. Jpn., 1985, 58, 477. 10 Y. Haramoto and H. Kamogawa, Chem. L ett., 1987, 755. 11 Y. Haramoto and H. Kamogawa, Mol. Cryst. L iq. Cryst. L ett., 1988, 5, 177. 12 Y. Haramoto and H. Kamogawa, Bull. Chem. Soc. Jpn., 1990, 63, 156. 13 Y. Haramoto, T. Hinata and H. Kamogawa, L iq. Cryst., 1992, 11, 335. 14 Y. Haramoto, S. Ujiie and H. Kamogawa, Chem. L ett., 1995, 133. 15 Y. Haramoto, M. Yin, Y. Matukawa, S. Ujiie and M. Nanasawa, L iq. Cryst., 1995, 19, 3, 319. 16 Y. Haramoto, S. Ujiie and M. Nanasawa, L iq. Cryst. Commun., 1996, 21, 923. 17 M. Schadt, R. Buchecker and L. Muller, L iq. Cryst., 1989, 5, 293. O S N O S N O S N O S N+ O S N+ O S N+ O S N+ O S N+ O S N+ + + + 38.9 Å Br– Br– Br– Br– Br– Br– Br– Br– Br– 18 R. Buchecker and M. Schadt, Mol. Cryst. L iq. Cryst., 1987, 149, Fig. 2 Molecular arrangement of the new ionic liquid crystal com- 359. pound 8 Communication 7/07622C; Received 22nd October, 1997 276 J. Mater. Chem., 1998, 8(2), 275–276

ISSN:0959-9428    

DOI:10.1039/a707622c

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Communication Calamitic smectic liquid crystalline supramolecular architecture from octaalkoxy-substituted PdII–g1-benzylideneaniline complexes Myongsoo Lee,* Yong-Sik Yoo, Moon-Gun Choi and Hong-Young Chang Department of Chemistry, Yonsei University, Sinchon 134, Seoul 120–749, Korea compounds.† Also, an X-ray crystallographic analysis performed for a model compound10 has confirmed that the Octaalkoxy substituted PdII–g1-benzylideneaniline complexes with a more disc-like shape can give rise to a calamitic smectic molecular structure appeared to be the PdII complex with g1- benylideneaniline.The mesomorphic properties of imine phase and low melting transition temperatures comparable to those of the corresponding free ligands. ligands 1, 2 and the complexes 3, 4 were studied using diVerential scanning calorimetry (DSC) and thermal optical polarized microscopy.Fig. 1 presents the DSC traces for the complexes obtained from the cooling scans. The thermal properties of the complexes are summarized and compared It is well documented that in general the number of peripheral with those of the corresponding ligands in Table 1.aliphatic chains connected to an aromatic core and the aniso- Both imine ligands exhibit only a crystalline melting and do tropic shape in metallomesogens are main factors in determin- not show liquid crystalline phase behavior. In contrast to the ing their supramolecular structure in the liquid crystalline thermal behavior of the ligands, the palladium complexes phase.1–7 Lamellar arrangements of liquid crystalline phases exhibit a liquid crystalline phase.Complex 3 with hexyloxy are formed for molecules with two to four peripheral chains, peripheral chains melts into an isotropic liquid at 91.8 °C. On whereas columnar arrangements are exhibited by metallomeso- cooling from the isotropic liquid, first bato�nnet-like growth of gens with six or more flexible aliphatic chains peripherally texture can be observed with a final development of focal conic connected to a central aromatic core.For example, dinuclear domains which are characteristic of a smectic A mesophase orthopalladated imine complexes with tetrasubstituted ali- exhibited by conventional calamitic mesogens. Thus, the phatic chains are reported to show calamitic smectic phases.8 On the other hand, the presence of four additional chains in † Supplementary material (SUP. 57325, 4 pp.) available from the the aromatic core of dinuclear orthopalladated complexes British Library. Details are available from the editorial oYce. produces a more disc-like molecular shape, thus leading to the formation of the discotic mesophase.9 This can be explained by the fact that the main factor governing the geometry of supramolecular structure in the liquid crystalline phase is the ratio of the volume occupied by the rigid core to the volume filled by the flexible peripheral substituents of the molecules.Here we report on the first examples of more disc-like octaalkoxy-substituted mononuclear PdII metallomesogens with g1-benzylideneaniline giving rise to a calamitic smectic A mesophase and low melting transition temperatures comparable to those of the corresponding free ligands in contrast to those of palladium(II ) orthometallated complexes.8 The mononuclear palladium complexes with monodentate imine ligands without orthocyclopalladation were synthesized by a ligand exchange reaction with [Pd(PhCN)2Cl2] and the corresponding imine ligands as shown in Scheme 1.The complexes were purified by column chromatography (silica gel ) using methylene chloride as eluent, and were obtained in 44–53% yields. Satisfactory analytical data were obtained for all the Fig. 1 DSC traces (10 °C min-1) recorded during the first cooling scans of 3 and 4 Table 1 Thermal transitions of the imine ligands and the Pd complexes (K, crystalline phase, SA, smectic A phase, I, isotropic phase) phase transitions/°C and corresponding enthalpy changes/kJ mol-1 compound heating cooling 1 K 84.2 (45.2) I I 71.0 (44.6) K 2 K 95.5 (90.1) I I 74.4 (90.7) K 3 K 91.8 (24.5) I I 61.2 (1.5) SA 50.3 (0.9) K RO RO N RO RO RO RO N RO RO Pd N OR OR OR OR Cl Cl Pd(PhCN)2Cl2 n-hexane R = CH3(CH2)5 1 CH3(CH2)9 2 R = CH3(CH2)5 3 CH3(CH2)9 4 4 K 79.7 (19.3) I I 64.5 (4.3) SA 55.0 (13.2) K Scheme 1 Synthesis of PdII complexes with g1-benzylideneaniline J.Mater. Chem., 1998, 8(2), 277–278 277performed on the mesophase of complex 4. The X-ray pattern of 4 exhibits two Bragg reflections in the small angle region with the ratio of positions of 152 and a diVuse scattering in the wide angle region as shown in Fig. 3. This result supports the existence of a disordered smectic mesophase. The existence of a layered smectic phase is in contrast with the normal behavior of disc-like octasubstituted metallomesogens which show a columnar type of supramolecular structure. The aromatic moieties of the imine ligands attached to a central metal will be twisted out of coplanar geometry to reduce steric repulsion.This distortion may provide a larger space for chains, and thus the peripheral chains are still not able to fill the space around the core eYciently. Consequently, the flexible chains tend to align in a preferred direction, leading to the lamellar self organization. This explains qualitatively the phase behavior of this palladium complex system.Fig. 2 Representative optical polarized micrograph (100×) of the texture exhibited by the smectic A mesophase of 4 at 64 °C on the Financial support of this work by the Non Directed Research cooling scan Fund, the Korea Research Foundation (1996) is gratefully acknowledged. We also acknowledge Mr. J. H. Im for the synthesis of a model compound and Prof. W.-C. Zin for X-ray powder diVraction experiments.References 1 Metallomesogens, ed. J. L. Serrano, VCH Publishers, Weinheim, 1996. 2 Q. M. Wang and D. W. Bruce, Angew. Chem., Int. Ed. Engl., 1997, 36, 150. 3 K. Outa, H. Akimito, T. Fujimoto and I. Yamamoto, J. Mater. Chem., 1994, 4, 61. 4 M. J. Baena, P. Espinet, M. B. Ros and J. L. Serrano, J. Mater. Chem., 1996, 6, 1291. 5 M. Ghedini, S. Morrone, O.Francescangeli and R. Bartolino, Chem. Mater., 1994, 6, 1971. 6 H. Zheng and T. M. Swager, J. Am. Chem. Soc., 1994, 116, 761. 7 S. N. Poelsma, A. H. Servante, F. P. Fanizzi and P. M. Maitlis, L iq. Cryst., 1994, 16, 675. 8 M. Ghedini, S. Licoccia, S. Armentano and R. Bartolino, Mol. Cryst. L iq. Cryst., 1984, 108, 269; M. Ghedini, S. Armentano, Fig. 3 Wide angle X-ray diVraction pattern for compound 4 at 60 °C F.Neve and S. Licoccia, J. Chem. Soc., Dalton T rans., 1988, 1565; on cooling M. Hoshino, H. Hasegawa and Y. Matsnaga, L iq. Cryst., 1991, 9, 267; J. Barbera, P. Espinet, E. Lalinde, M. Marcos and smectic A liquid crystalline phase of 3 is monotropic. Complex J. L. Serrano, L iq. Cryst., 1987, 2, 833. 4 with decyloxy peripheral chains shows similar thermal 9 K.Praefcke, D. Singer and B. Gundogan, Mol. Cryst. L iq. Cryst., 1992, 223, 181; D. Singer, A. Liebmann, K. Praefcke and behavior to 3 which exhibits a monotropic smectic A meso- J. H. WendorV, L iq. Cryst., 1993, 14, 785. phase. On heating, 4 melts into an isotropic liquid at 79.7 °C 10 We have synthesized bis[g1(N)-4-ethyloxybenzylidene-4¾-ethylox- which is an even lower melting transition temperature than yaniline]dichloropalladium(II) as a model compound in order to that of the corresponding ligand.The transition from the confirm the molecular structure by a single crystal X-ray structural isotropic liquid can be seen by the formation of a focal conic analysis. Full crystallographic details, excluding structure factors fan-like texture indicating a smectic A mesophase as shown in have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Information for Authors, Issue 1.Any request Fig. 2.11 Induction of comparable or even lower melting transto the CCDC for this material should quote the full literature ition temperatures in the complexes compared to those of the citation and the reference number 1145/75. ligands is very rare in calamitic metallosogenic systems, and 11 D. Demus and L. Richter, T extures of L iquid Crystals, Verlag is rewarding with respect to their potential processability. This Chemie, Weinheim, 1978; G. W. Gray and J. W. Goodby, Smectic is mainly due to disturbance of the crystal packing of the L iquid Crystals. T extures and Structures, Leonard Hill, Glasgow, molecules caused by the chlorine atoms which are out of the 1984. plane of the aromatic core. Communication 7/08128F; Received 11th November, 1997 Preliminary X-ray diVraction measurements have been 278 J. Mater. Chem., 1998, 8(2), 277–278

ISSN:0959-9428    

DOI:10.1039/a708128f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Communication Metal chalcogenide–organic nanostructured composites from self-assembled organic amine templates Neeraj and C. N. R. Rao* Chemistry and Physics ofMaterials Unit, Jawaharlal Nehru Center for Advanced Scientific Research, Jakkur Post, Bangalore 560 064, India hexagonal structure consistent with the XRD pattern in Fig. 1(a). The image shows the wall thickness to be ca. 2.0 nm, Hexagonal and lamellar nanostructured organic–metal chalcogenide composites have been prepared by the reaction of however, there is considerable disorder. When we employed a Cd(CH3CO2)25amine ratio of 152 metal salt aliphatic-amine nanostructured adducts with Na2S or Na2Se solution; nanostructured composites of CdS, SnS2, instead of 151, we obtained a lamellar structure as evident from the XRD pattern of an adduct with SA shown in Fig. 1(c) Sb2S3 and CdSe with long-chain aliphatic amines obtained in this manner have been characterized. with d-values of 5.0, 2.5 and 1.64 nm corresponding to the (001), (002) and (003) reflections, respectively. TG showed that the amine was completely removed at 623 K and the water removed at 393 K.The composition of the chalcogenide–SA adduct from TG gave the composition 9CdS·8SA·3.5H2O. A typical TEM image of the lamellar mesophase is shown in Braun et al.1 have recently described semiconductor–organic Fig. 2(b) which shows a well defined striped pattern with a nanostructured composites of hexagonal symmetry based on periodicity of ca. 5 nm. No change was observed on tilting the cadmium sulfide obtained by using non-ionic amphiphiles such particle perpendicular to the stripes, confirming the lamellar as poly(ethylene oxide). Such nanocomposites have been premorphology.When we employed thiourea instead of Na2S as pared by starting with diVerent cadmium salts.2 By employing the sulfiding agent, we obtained a lamellar nanostructure of hydrated polyol amphiphiles, Osenar et al.3 have obtained CdS with DA of composition 4CdS·3DA.The XRD pattern of lamellar, nanostructured cadmium sulfide. In all these prepthis adduct is shown in Fig. 1(d), with d values of 3.53, 1.74, arations, the nanostructured adduct of a cadmium salt with 1.17, 0.88 and 0.7 nm, respectively, due to (001), (002), (003), the amphiphiles was treated with H2S gas.Since the prep- (004) and (005) reflections. We also obtained excellent lamellar aration of the chalcogenide nanocomposites using amphiphiles mesophases by using long-chain thiols with Cd(CH3CO2)2. involves methods akin to those employed in the synthesis of For example, the adduct with dodecanethiol (DT) had the mesoporous metal oxides,4–6 we considered it important to composition 3Cd(CH3CO2)2·4DT. However, on heating this evolve a general method for the synthesis of mesostructured adduct we could not obtain pure CdS.semiconductor chalcogenide–organic nanostructures and characterize the materials suitably. By employing long-chain amines as the amphiphiles,7 we have prepared both hexagonal and lamellar nanostructures of CdS, SnS2, Sb2S3 and CdSe.The general procedure for the synthesis employed by us is as follows: to an aqueous solution of cadmium acetate (5 mmol) was added an alcoholic solution of the amphiphilic amine (5 mmol) and the mixture was stirred to obtain a gel. The gel was aged at ambient temperature for 18 h and dried. X-Ray diVraction (XRD) patterns of the gel indicated that nanostructured mesophases of the amine and Cd(CH3CO2)2 had indeed formed. To the gel, a concentrated aqueous solution of sodium sulfide was slowly added and the pH adjusted to 9.0–9.5.The resulting product was aged at 333 K for 18 h. The product thus obtained was washed first with water, followed by a ethanol–diethyl ether (50550) mixture and dried at 333 K. The X-ray diVraction pattern of the product was then recorded.Fig. 1(a) and (b) show the XRD patterns of the mesophases obtained with dodecylamine (DA) and stearylamine (SA), respectively. The diVraction patterns are characteristic of a hexagonal mesophase with d100 values of 4.1 and 5.5 nm, respectively, for DA and SA. EDX analysis of these products gave a Cd5S ratio of 151 (see inset of Fig. 1) showing that the sulfide had the expected composition.Thermogravimetry (TG) showed that the amine template was completely removed below 573 K while the water of hydration, if any, was removed at 393 K. TG gave the compositions of the chalcogenide amine adducts as 3CdS·DA and 7CdS·6SA·9H2O for DA and SA, Fig. 1 X-Ray diVraction patterns of (Cu-Ka radiation) CdS–amine respectively. The hexagonal nature of the CdS–amine adducts nanostructures.Hexagonal phases obtained with (a) dodecylamine and was also confirmed by recording transmission electron micro- (b) stearylamine. Lamellar phases obtained with (c) stearylamine and scope (TEM) images. The TEM image of the adduct of CdS (d) using thiourea as the sulfiding agent. Inset shows EDX of an adduct with dodecylamine. with DA shown in Fig. 2(a) suggests that the mesophase has a J.Mater. Chem., 1998, 8(2), 279–280 279Fig. 3 X-Ray diVraction patterns of metal chalcogenide–amine nanostructures: (a) SnS2–dodecylamine, (b) Sb2S3–dodecylamine, (c) CdSe– Fig. 2 TEM images of CdS–amine nanostructures: (a) hexagonal phase dodecylamine. The EDX results are shown alongside the XRD patterns. with dodecylamine, (b) lamellar phase with stearylamine Cd(CH3CO2)2–amine gel.Fig. 3(c) shows the XRD pattern of On heating the hexagonal CdS adduct with DA at 473 K the hexagonal mesophase of the CdSe–DA adduct with d for 2 h, the mesostructure collapsed, but the resulting sulfide values of 3.66, 1.9 and 1.75 nm for the (100), (110) and (200) exhibited high surface area (90 m2 g-1). We have been able to reflections, respectively.The adduct had the composition remove amine partly from the hexagonal phase of the CdS 9CdSe·4DA and the amine could be removed completely at adduct with SA by heating it slowly at 448 K for 2 h. The 573 K. We have also been able to obtain CdSe–amine nano- XRD pattern of the product showed a feature corresponding structures by employing sodium selenosulfate as a seleniding to a d100 value of ca. 5.5 nm, although somewhat weaker in agent instead of Na2Se; Na2Se however appears to be a better intensity compared to the adduct. seleniding agent. We have also been able to synthesize metal sulfide–organic amphiphile nanostructures of tin and antimony by starting References from SnCl4·2H2O and SbCl3·5H2O, respectively, and keeping the metal salt5amine ratio at 151.XRD patterns of the 1 P. V. Braun, P. Osenar and S. I. Stupp, Nature (L ondon), 1996, hexagonal mesophases of the adducts of SnS2 and Sb2S3 with 380, 325. DA are shown in Fig. 3(a) and (b), respectively, with d100 values 2 V. Tohver, P. V. Braun, M. U. Pralle and S. I. Stupp, Chem. Mater., of 3.12 and 3.57 nm. The d110 and d200 reflections are also 1997, 9, 1495. 3 P.Osenar, P. V. Braun and S. I. Stupp, Adv.Mater., 1996, 8, 1022. observed at larger angles. The composition of the sulfides was 4 J. S. Beck and J. C. Vartuli, Curr. Opinion Solid State Mater. Sci., confirmed by EDX analysis (see insets of Fig. 3). TG indicated 1996, 1, 76. the adduct compositions to be 2SnS2·3DA·H2O and 5 P. Behrens, Angew. Chem., Int. Ed. Engl., 1996, 35, 515. 5Sb2S3·7DA·H2O. TEM images showed that the adducts pos- 6 S. Ayyappan and C. N. R. Rao, Chem. Commun., 1997, 575. sessed disordered hexagonal structures. 7 P. T. Tanev and T. J. Pinnavaia, Science, 1995, 267, 365. In order to prepare CdSe–amine nanostructures, we 8 N. Ulagappan, Neeraj, B. V. N. Raju and C. N. R. Rao, Chem. Commun., 1996, 2243. employed a procedure similar to that with CdS, except that an aqueous solution of Na2Se was reacted with the Communication 7/07690H; Received 24th October, 1997 280 J. Mater. Chem., 1998, 8(2), 279–280

ISSN:0959-9428    

DOI:10.1039/a707690h

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Communication NaBi3V2O10: a new oxide ion conductor Derek C. Sinclair, Craig J.Watson, R. Alan Howie, Janet M. S. Skakle, Alison M. Coats, Caroline A. Kirk, Eric E. Lachowski and James Marr Chemistry Department, University of Aberdeen, Meston Walk, Aberdeen, UK, AB24 3UE c=5.5312(6) A ° , a=84.542(12), b=113.318(11) and c= 112.267(12)°. Table 1 shows the first thirty lines of the indexed The new phase NaBi3V2O10 is reported; it was synthesised by oxide reaction at 600 °C and is triclinic with a=7.2026(10), powder pattern.Given that the volume of an oxygen ion can be estimated as ca. 22A ° 3, the cell volume of 238.53(4) A ° 3 is in b=7.0600(9), c=5.5312(6) A ° , a=84.542(12), b=113.318(11) and c=112.267(12)°; it is an oxide ion conductor with good agreement with that expected for the proposed formula with Z=1, giving support to the suggested unit cell.In conductivity of ca. 1.5 mS cm-1 at 675 °C. addition, selected area electron diVraction (SAED) studies have also been found to be consistent the unit cell proposed by the VISSER program. DiVerential thermal analysis showed the presence of a large endotherm at 575 °C on heating which was fully reversible on Yttria-stabilised zirconia (YSZ) is commonly employed as a thermal cycling, suggesting NaBi3V2O10 undergoes a poly- solid electrolyte in many technological applications such as morphic phase transition at this temperature.Although this solid oxide fuel cells and oxygen pumps.1 Although YSZ is an has been confirmed by high temperature XRD, as yet, we have excellent solid electrolyte there remains much interest, from no information on the symmetry or crystal structure of the both a fundamental and an industrial view point, in trying to high temperature polymorph.find new oxide ion conductors2,3 which have superior electrical ac Impedance measurements on a pellet sintered at 675 °C properties compared with YSZ.Over the last eight years, there and coated with Au paste electrodes were collected on both has been considerable interest in doped Bi4+yV2-yO11-y solid heating and cooling in air between 25–675 °C. Complex solutions4,5 known by the acronym BIMEVOX, where ME impedance plane, Z*, plots consisted of a single, semi-circular corresponds to the dopant ion, owing to their high oxide ion arc and a low frequency electrode ‘spike’, as shown in Fig. 1. conductivity. During a phase diagram study of the composi- The associated capacitance of the arc was calculated to be ca. tional range of BINAVOX solid solutions6 within the 3–5 pF cm-1 using the relationship vRC=1 (where v=2pf and Na2O–Bi2O3–V2O5 ternary system, we discovered a new phase, is the angular frequency) at the arc maximum.This capacitance whose composition was determined via electron probe microanalysis (EPMA) to be NaBi3V2O10.7 Here, we report the synthesis of this new phase, a fully indexed X-ray pattern based on a primitive, triclinic cell and preliminary conductivity data Table 1 Indexed X-ray diVraction pattern for triclinic NaBi3V2O10 that suggests NaBi3V2O10 is an oxide ion conductor.with a=7.2026(10), b=7.0600(9), c=5.5312(6) A° , a=84.542(12), b= NaBi3V2O10 was prepared by conventional solid state syn- 113.318(11) and c=112.267(12), V=238.53(4) A °3. A full listing (101 lines) is available from the authors on request thesis. Bi2O3 (99.99%), V2O5 (99.6%) and Na2CO3 (99.99%) reagents were dried at 300 °C overnight and stored in a dobs dcalc h k l I/I0 D(2h) desiccator prior to use. A reaction mixture of stoichiometry NaBi3V2O10 totalling 3–4 g was weighed from the starting 6.5256 6.5199 0 1 0 15.3 -0.0119 reagents and mixed into a paste with acetone using an agate 6.1454 6.1361 1 0 0 72.4 -0.0220 mortar and pestle, dried and fired in Au foil boats.A combi- 5.6451 5.6415 -1 1 0 19.5 -0.0103 5.0719 5.0688 0 0 1 14.6 -0.0105 nation of X-ray powder diVraction (XRD) data and EPMA 4.9816 4.9773 -1 0 1 22.6 -0.0156 results showed that a single phase yellow powder could be 4.5150 4.5113 -1 1 1 9.5 -0.0162 prepared by heating the reaction mixture at 600 °C for 24 h, 4.1327 4.1332 0 -1 1 29.2 0.0025 with an intermediate regrind after 12 h.EPMA analysis showed 3.8844 3.8821 0 1 1 1.1 -0.0139 that there was no evidence of any secondary or unreacted 3.8137 3.8139 1 1 0 9.1 0.0013 phases on a micrometre scale.Quantitative EPMA analysis 3.5657 3.5659 -1 -1 1 8.7 0.0008 3.4631 3.4641 -1 2 0 6.8 0.0078 on twenty seven points of a sintered pellet determined the 3.4278 3.4293 -2 1 1 22.6 0.0109 composition to be 15.9 mol% Na2O, 33.6 mol% V2O5 and 3.3195 3.3224 1 0 1 96.7 0.0235 50.5 mol% Bi2O3 which is in good agreement with the starting 3.2867 3.2891 -2 1 0 29.2 0.0203 composition of NaBi3V2O10. 3.2479 3.2456 -2 0 1 100.0 -0.0197 On heating above ca. 700 °C, the yellow powder became 3.0836 3.0867 -1 2 1 71.1 0.0298 brown and extra reflections associated with a secondary phase 3.0650 3.0681 2 0 0 9.2 0.0300 2.8577 2.8607 -2 2 1 15.7 0.0338 appeared in the XRD patterns.The reaction mixture melted 2.8180 2.8207 -2 2 0 86.5 0.0309 at ca. 755 °C and formed a purple–brown coloured solid on 2.7531 2.7523 -1 0 2 41.8 -0.0100 cooling. XRD analysis showed the minor phase in powders 2.7041 2.7048 1 1 1 12.7 0.0090 heated above 700 °C and the major phase cooled from the 2.6775 2.6769 1 -2 1 18.6 -0.0074 melt to be a c-polymorph of the BINAVOX solid solution. 2.6268 2.6289 -1 1 2 15.9 0.0285 Detailed phase studies are currently in progress and will be 2.5671 2.5660 -2 -1 1 2.1 -0.0152 2.5326 2.5344 0 0 2 19.3 0.0266 reported elsewhere. 2.5133 2.5159 1 2 0 36.8 0.0386 The program VISSER8 was used in an attempt to index the 2.4877 2.4886 -2 0 2 5.2 0.0149 XRD pattern of NaBi3V2O10; results suggested that the most 2.4458 2.4464 2 1 0 17.5 0.0101 probable solution was a primitive triclinic cell, which was 2.3952 2.3969 -3 1 1 5.2 0.0286 refined to give a unit cell, a=7.2026(10), b=7.0600(9), J.Mater. Chem., 1998, 8(2), 281–282 281Fig. 2 Z* plots for NaBi3V2O10 in various atmospheres at 650 °C. Fig. 1 Z* plot for NaBi3V2O10 in air at 505 °C. Selected frequencies 0.3 Hz is identified by the filled symbol in N2 and air data.in filled circles are identified by the logarithm of the frequency, e.g. 2=102 Hz. value was temperature independent over the measured range and is consistent with a bulk or intra-granular response. The presence of a low frequency spike with an associated capacitance of 1–5 mF in Fig. 1 is attributable to ionic polarisation and diVusion-limited phenomena at the electrode and supports the idea that the conduction is mainly by means of ions.At higher temperatures in air, ca. 600 °C, the low frequency response consists of a broad semi-circular arc with an associated capacitance of ca. 10-5 F, consistent with a charge transfer reaction occurring at the sample/electrode interface. The resistance associated with this process can be estimated from the diameter of the low frequency semi-circular arc in Z* plots.In order to establish if the material was an oxide ion conductor the gas atmosphere at 650 °C was changed sequentially from laboratory air to flowing oxygen to flowing nitrogen before reverting to laboratory air. The oxygen partial pressure of the atmosphere had a dramatic eVect on the low frequency Fig. 3 Arrhenius plot of the bulk conductivity in air.Open and closed response, as shown in Fig. 2. On changing the atmosphere circles represent heating and cooling data, respectively. from laboratory air to flowing oxygen the resistance associated with the charge transfer process occurring at the electrode/ fully reversible on thermal cycling. As the data do not obey sample interface decreased from a value of ca. 1.25 kV to a the Arrhenius law it is diYcult to calculate any activation (constant) value of ca. 0.25 kV after ca. 1 h. In flowing N2 the energy for the bulk conduction process, however, the data resistance associated with the charge transfer process increased clearly start to approach a plateau above 600 °C. rapidly and after 1 h the low frequency response consisted of The bulk conductivity of NaBi3V2O10 is two orders of an inclined-spike at an angle of ca. 45°. Such a response is magnitude lower than that of YSZ at ca. 600 °C;1 as yet, indicative of a Warburg-like response and suggests that the however, we have only studied the parent material. It may be rate-limiting step controlling the overall impedance at low possible to enhance the conductivity of NaBi3V2O10, especially frequencies involves the diVusion of electroactive species below the phase transition temperature of 575 °C by stabilising to/from the electrode/sample interface. Given the dependence the high temperature polymorph via chemical doping, as is the of this process on oxygen partial pressure in the surrounding case with ZrO2- and BIMEVOX-based solid electrolytes.atmosphere, the diVusing species must be oxygen-based, presumably O2 molecules. This therefore indicates that We wish to thank Professor Tony West for useful discussions, NaBi3V2O10 is predominantly an O2- ion (rather than an Na+ the University of Aberdeen for a studentship (C.J.W.) and ion) conductor. EPSRC for financial support for the EPMA facility. The changes in electrode behaviour were reproducible on switching between the various atmospheres whereas the bulk resistivity was independent of oxygen partial pressure, as References shown by the high frequency, non-zero intercept in Fig. 2. 1 B. C. H. Steele, Solid State Ionics, 1984, 12, 391. Although we need to perform concentration (emf ) cell measure- 2 H. L. Tuller and A. S. Nowick, J. Electrochem.Soc., 1975, 122, 255. ments in order to prove that NaBi3V2O10 is an oxide ion 3 T. Ishihara, H. Matsuda and Y. Takita, J. Am. Chem. Soc., 1994, conductor, the impedance behaviour described above is com- 116, 3801. 4 F. Abraham, J. C. Boivin, G. Mairesse and G. Nowogrocki, Solid pelling evidence that this material is predominantly an oxide- State Ionics, 1990, 40/41, 934. ion conductor. 5 C. K. Lee, B. H. Bay and A. R. West, J.Mater. Chem., 1996, 6, 331. Bulk conductivity values were calculated from the reciprocal 6 C. J. Watson, A. Coats and D. C. Sinclair, J. Mater. Chem., 1997, of the low frequency intercept of the high frequency semi- 7, 2091. circular arc with the Z¾ axis of Z* plots and are shown in the 7 C. J.Watson, M.Sc. Thesis, University of Aberdeen, 1997. form of an Arrhenius plot, Fig. 3. There is no discontinuity in 8 J.W. Visser, J. Appl. Crystallogr., 1969, 2, 89. the Arrhenius plot around the transition temperature at ca. 575 °C, instead the data yield a sigmoidal curve which is nearly Communication 7/07760B; Received 28th October, 1997 282 J. Mater. Chem., 1998, 8(2), 281–282

ISSN:0959-9428    

DOI:10.1039/a707760b

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Communication Observation of a thermally induced spin crossover in a CdPS3 intercalate Christian N. Field, Marie-Laure Boillot* and Rene� Cle�ment* L aboratoire de Chimie Inorganique, Ba�timent 420, URA420, Universite� de Paris-Sud, 91405 Orsay, France solution of I at 110 °C for 20 h in a Pyrex ampoule sealed under vacuum. The dark red solids thus formed (IIa and IIb, Magnetic susceptibility measurements of the layered intercalate Cd1-xPS3 [FeIII(SalEen)2]2x (x=0.14) reveal that respectively) were washed with methanol until the supernatant liquor became colourless.the trapped species undergo a gradual thermally induced spin crossover. The intercalates IIa and IIb were characterised by their powder X-ray diVractograms which showed quite sharp 00l reflections corresponding to an interlayer spacing of 14.8 A° (6.5 A ° for CdPS3 and 11.5 A ° for the pre-intercalate).The diVractogram of IIb also exhibited the broadened 001 reflection of pure CdPS3. The reflections given by IIa are somewhat There has been in recent years a renewed interest in the highsharper than those of IIb, hence IIa is better crystallized. spin (HS) < low-spin (LS) crossover phenomenon exhibited Elemental analyses indicate that IIa retains 3% chloride while by transition metal complexes.1–3 Besides progress in the IIb only retains a negligible amount.On the other hand, the understanding of thermally induced spin crossovers, lightpresence of re-formed CdPS3 in IIb results in a lower complex induced spin switching has opened up perspectives in optical content.The P, S and Fe contents in IIa suggest a formula information technology.4,5 There are several reasons to investiclose to Cd0.86PS3[FeIII(SalEen)2]0.28 for the intercalate,† in gate intercalation of spin-transition complexes in layered agreement with the stoichiometry usually observed for guest systems. The environment of the active complex (solvent,2,6 species of that size.The IR spectra of IIa and IIb were almost counterion,2,7,8 intermolecular interactions,9 packing defects1) identical. They showed numerous bands slightly broader and is well known to exert a dramatic influence on the transition. weaker than those of salt I, but at essentially the same Therefore the eVect of sterically restraining host layers and wavenumbers, as well as a strong signal assignable to the u(PS3) reduced dimensionality may considerably aVect the transition.stretching modes of CdPS3, split into three components at A layered system can also be viewed as a storage medium 560, 580 and 605 cm-1. This set of characterisation data is which could provide new pathways to act on the spin states therefore consistent with the presence in IIa and IIb by irradiation of the host lattice and subsequent host to guest of nearly close-packed [FeIII(SalEen)2] cations lying in the energy transfer.10 Spin crossover in two complexes synthesized interlayer galleries.in situ in Y-zeolite cages or layered silicates have been The temperature dependence of the magnetic susceptibility reported.11–13 No evidence for intermolecular interactions x (per mole of Fe) of both intercalates, measured with a was found, but the zeolite host lattice appears to stabilize con- Quantum Design SQUID magnetometer over the range figurations that diVer from those in the usual solid state. We 4–400 K, is shown in Fig. 1 as a plot of xT versus T . These report here the thermally induced spin crossover of a results clearly demonstrate that the FeIII centres undergo a cationic [FeIII(SalEen)2]+ complex intercalated in the layered spin crossover between low-spin (LS) S=1/2 and high-spin diamagnetic CdPS3 thiophosphate.(HS) S=5/2, centered at a half-conversion temperature T1/2= The [FeIII(SalEen)2]Cl compound I, where SalEen is the 255 K. The transition is relatively smooth.No hysteresis was monoanion of the condensation product of salicylaldehyde observed when a full temperature cycle was followed. Focussing and N-ethylethylenediamine, was synthesised according to the on IIa, the experimental xT value on the low temperature procedure used for the NO3, BPh4 and PF6 analogues, using plateau (1.23–1.40 cm3 mol-1 K) is significantly higher than FeCl3·6H2O.7 The composition of I was verified by elemental that expected for the LS state of FeIII (xT#0.50 cm3 mol-1 K, analysis and IR spectroscopy. taken from I in the LS state; see below; this is ascribed to The CdPS3 layered compound14 is known to react with residual HS molecules (28%).In contrast, the crossover is solutions of certain ionic salts G+X- to give intercalation complete on the high temperature side.Comparing the two compounds of a general formula Cd1-xPS3G2x·(solvent)y .15 In intercalates, the crossover is very slightly more abrupt in IIa these compounds, charge balance is maintained by the loss of (DT 80=180 K)‡ than in IIb (DT 80=200 K), the completeness one Cd2+ ion from the intralayer region for every two G+ of the crossover is larger in IIa (HS residue at low T for ions that are inserted in the interlayer region. In the present IIb#36%), but the crossover temperatures are very similar. case, no reaction occurred upon treating CdPS3 with a meth- These features are consistent with the better crystallinity of anolic solution of I.A two-step procedure was therefore IIa, and hence the presence of fewer defects.16 The incomemployed.(i) A pre-intercalate Cd1-xPS3(Me4N)2x was prepared by treating CdPS3 (typically 200 mg) with Me4NCl (1 g) in dry methanol (20 ml ) at 20 °C for 1 day. As already seen † Analytical data for the intercalates. IIa: C, 21.12; H, 2.68; N, 4.60; Fe, 3.96; Cd, 24.96; P, 7.79; S, 23.03; Cl, 3.38. Calc. for for cobaltocenium intercalated into CdPS3, the Cd2+ ions Cd0.86PS3[Fe(salEen)2]0.28[(Me4N) (CdCl3)]0.10: C, 20.89; H, 2.57; N, extracted from CdPS3 form a sparingly soluble (Me4N) (CdCl3) 4.53; Fe, 4.16; Cd, 28.98; P, 8.22; S, 25.45; Cl, 2.78%.IIb: C, 12.09; H, diamagnetic salt.15 Extensive washing by methanol allowed 1.53; N, 2.52; Fe, 2.50; Cd, 37.40; P, 10.11; S, 30.46; Cl, 0.22. Calc. for dissolution of this impurity but caused partial decomposition Cd0.94PS3[Fe(salEen)2]0.12[(Me4N) (CdCl3)]0.01: C, 11.11; H, 1.3; N, of the pre-intercalate into CdPS3.(ii ) Two samples of the 2.37; Fe, 2.32; Cd, 37.38; P, 10.7; S, 33.14; Cl, 0.36%. above pre-intercalate, one moderately washed with methanol, ‡ DT 80 represents the temperature interval over which the spin conversion varies from 10 to 90%. the other one thoroughly, were then treated with a methanolic J.Mater. Chem., 1998, 8(2), 283–284 283in order to draw a general conclusion, the present result tells us that intercalation could be used as worthwhile strategy to pack active species, especially because it brings additional degrees of freedom. The authors are grateful to the Royal Society for a postdoctoral fellowship (to C. N. F.) under the European Science Exchange programme and to Dr Eric Rivie`re for the SQUID measurements.References 1 E.Ko� nig, G. Ritter and S. K. Kulshreshtha, Chem. Rev., 1985, 85, 219. 2 P.Gu� tlich, A. Hauser and H. Spiering, Angew. Chem., Int., Ed. Engl., 1994, 33, 2024. 3 O. Kahn,MolecularMagnetism, VCH Publishers, New York, 1993, ch. 4. Fig. 1 xT vs. T plot of [FeIII(SalEen)2]Cl ($) and of the CdPS3 4 P.Gu� tlich and A. Hauser, Coord.Chem. Rev., 1990, 97, 1. intercalates IIa (#) and IIb (6). x is expressed per mole of Fe in 5 M. L. Boillot, C. Roux, J. P. Audie`re, A. Dausse and all cases. J. Zarembowitch, Inorg. Chem., 1996, 35, 3975. 6 M. Sorai, J. Ensling, K. M. Hasselbach and P. Gu� tlich, Chem. Phys., 1977, 20, 1997. pleteness of the crossover at low temperature might also be 7 M.S. Haddad, M. W. Lynch, W. D. Federer and ascribed to Fe3+ impurities resulting from a slight decompo- D. N. Hendrickson, Inorg. Chem., 1981, 20, 123. sition of the complex, but the analytical data for Fe, C and N 8 A. M. Greenaway, C. J. O’Connor, A. Schrock and E. Sinn, Inorg. show good agreement with the expected composition Chem., 1979, 18, 2692.Fe(SalEen)2+. 9 J.-P. Martin, J. Zarembowitch A. Dworkin, The magnetic behaviour of the intercalated FeIII complex J. G. Haasnoot and F. Varret, Inorg. Chem., 1994, 33, 6325. 10 E. Lifshitz, R. Cle�ment, L. C. Yu-Hallada and A. H. Francis, should of course be compared to that of the starting chloride J. Phys. Chem. Solids, 1991, 52, 1081. I. The temperature dependence of xT measured for I is also 11 K.Mizuno and J. H. Lunsford, Inorg. Chem., 1983, 22, 3484. shown in Fig. 1. This compound undergoes a smooth but 12 Y. Umemura, Y. Minai, N. Koga and T. Tominaga, J. Chem. Soc., complete spin crossover centered at T1/2=320 K, more abrupt Chem. Commun., 1994, 893. than the intercalates (DT 80=148 K). 13 M. Nakano, S. Okuno, G. E. Matsubayashi, W.Mori and From these results, one might conclude that intercalation of M. Katada,Mol. Cryst. L iq. Cryst., 1996, 286, 83. 14 W. Klingen, R. Ott and H. Hahn, Z. Anorg. Allg. Chem., 1973, the FeIII complex does not suppress its spin crossover, but 396, 271. exerts a damping eVect. However the eVect of intercalation 15 R. Cle�ment, O. Garnier and J. Jegoudez, Inorg. Chem., 1986, 25, appears more positive if the intercalated complex is compared 1404. to other salts. Thus, [FeIII(SalEen)2]PF6 has been reported to 16 M. S. Haddad, W. D. Federer, M. W. Lynch and show a gradual spin crossover centered at T1/2=140 K only D. N. Hendrickson, Inorg. Chem., 1981, 20, 131. and the nitrate salt exhibits a very incomplete transition.7 Although other complexes and intercalates should be studied Communication 7/07887K; Received 3rd November, 1997 284 J. Mater. Chem., 1998, 8(2), 283&ndash

ISSN:0959-9428    

DOI:10.1039/a707887k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Crystal structure and physical properties of (TTM-TTP)AuI2† Tadashi Kawamoto,*a Masanobu Aragaki,a Takehiko Mori,a Yohji Misakib and Tokio Yamabeb aDepartment of Organic and Polymeric Materials, T okyo Institute of T echnology, O-okayama, T okyo 152, Japan bDivision of Molecular Engineering, Graduate School of Engineering, Kyoto University, Yoshida, Kyoto 606–01, Japan Crystal structure analysis of new organic conductors (TTM-TTP)AuI2 and (TTM-TTP)AuBr2, where TTM-TTP is 2,5-bis[4,5- bis(methylthio)-1,3-dithiol-2-ylidene]-1,3,4,6-tetrathiapentalene, has been carried out. The donor to anion ratio is 151 and the donors form highly one-dimensional columns. These materials, however, show dimerization of the donor molecules along the stacking direction.Therefore the energy gap appears at the Fermi level, and these salts become band insulators. The observed temperature dependence of the conductivity is semiconducting, but the room-temperature conductivity is comparatively high, 10–40 S cm-1. Many bis-fused TTF donors, denoted TTP donors, have been Experimental synthesized and many radical-cation salts have been obtained.TTM-TTP was prepared as described in ref. 8. Crystals of the Most of the radical-cation salts of TTP series donors show linear anions were grown by electrochemical oxidation in THF metallic behavior down to liquid-He temperature and they are in the presence of the donor and the tetrabutylammonium quasi-two-dimensional conductors.1–3 Among many salts of salts of the corresponding anions under a constant current of TTP series donors, only (DTEDT)3Au(CN)2 shows supercon- 1 mA at 28°C.These conditions were the same as the case of ductivity below 4 K at ambient pressure.4 The radical-cation (TTM-TTP)I3. In the case of AuI2- and AuBr2-, single salts of TTM-TTP (see below), however, are quasi-one-dimencrystals were obtained. These crystals were in the form of sional conductors.5,6 Although most of the TTM-TTP salts elongated black thin plates with typical dimensions, are semiconductors below room temperature, (TTM-TTP)I3 2.0×0.14×0.08 mm.Their crystal structures were determined shows metallic behavior and a metal–insulator transition at by the X-ray single crystal structure analysis.‡ 160 K.6 It is surprising that an organic conductor with a half- All measurements were made on a Rigaku Raxis II area filled band, in other words with 151 composition, shows detector with graphite monochromated Mo-Ka radiation. The metallic conductivity, because in general 151 salts are insulators structure was solved by the direct method (SHELX86) and on account of the on-site Coulomb repulsion.Recently we was refined by the full-matrix least-squares procedure.9 Neutral have observed paramagnetic behavior which is fitted with the atom scattering factors were taken from ref. 10. Anisotropic one-dimensional Heisenberg model from room temperature to thermal parameters were adopted for all non-hydrogen atoms. 2 K, without showing any anomaly at the metal–insulator From the result of the X-ray crystal structure analysis, the transition temperature.So the low-temperature phase is attrielectronic structure was calculated on the basis of the extended buted to the Mott insulator.7 Such a perfect separation of the Hu� ckel method.11 spin and charge degrees of freedom has been predicted by the Electrical resistivity was measured by the four-probe method Luttinger liquid theory in the half-filling case.Although the using low-frequency ac current (usually 10 mA). metal–insulator transition temperature is lowered under pressure, the shift is so small that the transition still remains at 90 K even at 11.5 kbar. Results Crystal structures Crystallographic data are listed in Table 1. The lattice constants show that the AuI2- and the AuBr2- salts are isostructual.Although the structure analyses were carried out for both salts, the data of the AuBr2- salt are not very good owing to its S S S S S S S S H3CS H3CS SCH3 SCH3 TTM-TTP poor crystal quality. Then we will concentrate on the results of the AuI2- salt. The atomic numbering scheme is shown in Fig. 1(a). The In order to apply chemical pressure by the use of shorter length of the c axis of the AuI2- salt is almost twice as long anions, preparation of the linear-anion salts other than I3- as that of the I3- salt, indicating that the donor molecules has been attempted.In this paper, crystal structure, energy form a dimer along the stacking direction. The I3- salt has band structure, and transport properties of (TTM-TTP)AuI2 only one donor molecule in a unit cell, but one unit cell and (TTM-TTP)AuBr2 will be shown and discussed in comcontains two donor molecules in the present compounds.In parison with (TTM-TTP)I3. (TTM-TTP)I3 the donor molecule is located on an inversion ‡ Full crystallographic details, excluding structure factors, have been deposited at the Cambridge Crystallographic Data Centre (CCDC). * kawamoto@o.cc.titech.ac.jp † Presented at the 58th Okazaki Conference, Recent Development See Information for Authors, J.Mater. Chem., 1996, Issue 1. Any request to the CCDC for this material should quote the full literature and Future Prospects of Molecular Based Conductors, Okazaki, Japan, 7–9 March 1997. citation and the reference number 1145/56. J. Mater. Chem., 1998, 8(2), 285–288 285Table 1 Crystallographic data terminal methylthio groups [Fig. 1(b)]. The terminal CMS bonds also extend basically in the molecular plane except for (TTM-TTP)AuI2 (TTM-TTP)AuBr2 C(13); the deviation of C(13) from the least-squares plane is 1.16 A° . In the present donor, the terminal carbons of the chemical formula C14H12S12AuI2 C14H12S12AuBr2 neutral molecule are reported to be out of the molecular formula weight 1015.876 921.876 shape black plate black plate plane.8 In contrast, in (TTM-TTP)I3 with +1 charge the crystal system triclinic triclinic molecular structure is flat.6 Therefore the flat molecular strucspace group P19 P19 ture of the present salt is consistent with the expected +1 a/A ° 12.745(6) 12.49(5) charge.b/A ° 13.641(6) 13.39(4) Intramolecular bond lengths (averaged so as to have hypo- c/A ° 9.410(8) 9.41(4) thetical mmm symmetry) are listed in Table 2.Although the a/° 107.39(6) 107.3(3) b/° 104.54(8) 104.2(4) changes of the bond lengths, when the donor is oxidized from c/° 100.08(4) 100.2(2) neutral to +1, are comparable to the estimated standard V /A° 3 1454(2) 1402(12) deviations of the bond lengths, particularly in such cases as Z 2 2 the present compound that contains heavy atoms like Au and Dc/g cm-3 2.320 2.184 I, comparing the bond lengths after averaging under the mmm l/A ° 0.71070 0.71070 symmetry, we can make an approximate estimate of the degree temperature/K 298 298 m(Mo-Ka)/cm-1 79.86 89.24 of charge transfer, as exemplified in ref. 13. In comparison with R 0.071 0.100 the neutral TTM-TTP, most CNC bonds become longer, and Rw a 0.097 0.119 most CMS bonds become shorter.This is consistent with the reflections used 2237 1256 symmetry of the HOMO, which has nodes on all CMS bonds. The bond lengths in (TTM-TTP)AuI2 are very close to those aw=1/s(I)2. in (TTM-TTP)I3. This also demonstrates that the donor molecule of this salt has +1 charge. The diVerences of the bond lengths between D0 and D+ are, however, as small as 0.01–0.03 A ° ; these values are about half of the corresponding changes in the TTF series, 0.02–0.07 A° .12 This is reasonable because the HOMO of the TTM-TTP molecule spreads on the larger molecule as pointed out in ref. 6. The donor molecules are stacked along the c axis [Fig. 2(b)]. Fig. 3 shows the overlap modes in the stack. Because the donor molecules dimerize along the stacking direction, there are two overlap modes.Both modes are ring-over-bond type. In one overlap mode denoted c1 in this stack [Fig. 2(b) and Fig. 3(a)], the slip distance along the molecular long axis is 1.6 A ° , which corresponds to about half of the length of a 1,3-dithiole ring. The interplanar distance of the c1 mode i3.46 A ° , where the plane of the donor molecule is defined by the bis-fused TTF part, but the CH3S parts are excluded.The other overlap mode denoted c2 [Fig. 2(b) and Fig. 3(b)] is the same as the uniform overlapping mode in (TTM-TTP)I3; the slip along the molecular long direction of c2 is 4.8 A ° , which corresponds to one and a half 1,3-dithiole rings. The interplanar distance of c2 is 3.48 A ° .This is slightly larger than that of the c1 mode. These Fig. 1 (a) ORTEP drawing and atomic numbering scheme of the donor stacking overlap modes have many SMS contacts shorter than molecule of (TTM-TTP)AuI2 and (b) side view of the molecule of the van der Waals distance. (TTM-TTP)AuI2 center.6 In the AuI2- salt, however, the donor molecule is Energy band structures located on a general position.A unit cell contains two AuI2- Calculated intermolecular overlap integrals of the HOMO are anions on general equivalent positions [Fig. 2(a)]. In (TTMlisted in Table 3. The diVerence between c1 and c2 designates TTP)I3 there are short I I contacts of 4.235(1) A ° , while in the degree of dimerization along the stack. The ratio of c1 to the present compound the closest I I distances are 4.566(6) c2 is about 352, therefore the dimerization is not so strong.and 5.102(4) A ° . Since these values are larger than the van der The intrastack overlaps are 200 times as large as those of Waals distance of I-, 4.2 A ° , we can regard the anions as interstack overlaps. Along [1190], the donor molecules cannot discrete AuI2-. No anion deficiency was found from the approach close to each other because of the steric hindrance structure analysis; therefore this complex has exact 151 of the terminal methyl groups.So the side-by-side interaction composition. along the molecular short axis is very small. This situation has The donor molecule is almost planar; the deviations from the least-squares plane are less than 0.2 A° except for the a close resemblance to (TTM-TTP)I3.Therefore the electronic Table 2 Intramolecular bond lengths (A ° ) of TTM-TTP averaged by assuming mmm symmetry S(5)MC(7) S(5)MC(6) S(3)MC(5) S(3)–C(3) S(6)MC(8) S(6)MC(6) S(4)MC(5) S(4)MC(4) S(7)MC(7) S(7)MC(9) C(5)MC(6) S(9)MC(10) S(9)MC(11) C(3)MC(4) salt C(7)MC(8) S(8)MC(8) S(8)MC(9) C(9)MC(10) S(10)MC(10) S(10)MC(12) C(11)MC(12) neutral 1.346(7) 1.743(4) 1.764(4) 1.348(6) 1.752(4) 1.754(4) 1.339(4) I3 1.362(9) 1.732(9) 1.748(6) 1.38(1) 1.737(8) 1.752(8) 1.351(9) AuI2 1.37(4) 1.73(3) 1.76(3) 1.38(3) 1.74(3) 1.75(3) 1.33(4) 286 J.Mater. Chem., 1998, 8(2), 285–288Fig. 2 Crystal structure of (TTM-TTP)AuI2. (a) Projection onto the ab plane, (b) view along the molecular short axis, and (c) view along the molecular long axis.Table 3 Intermolecular overlap integrals, S (×103) of the HOMO of (TTM-TTP)AuI2 c1 27.4 c2 19.1 p1 -0.07 p2 -0.01 p3 0.19 q1 -0.17 q2 -0.03 q3 -0.10 q4 -0.05 structures of the present materials are regarded as highly onedimensional. Fig. 4 shows the energy band structure calculated on the basis of the extended Hu� ckel orbital calculation and the tightbinding method. Because a unit cell contains two donor molecules, there are two energy bands. This is diVerent from (TTM-TTP)I3.As a result of the 151 composition, the band is half-filled like the I3- salt. The energy gap, however, exists at the Fermi level, and thus no Fermi surface exists. This band structure predicts that the present salts are band insulators. Transport properties The conductivity at room temperature is about 10 and 40 S cm-1 for the AuI2- and AuBr2- salts, respectively.These conductivities are much lower than that of (TTM-TTP)I3.6 These values are, however, comparatively high for a band Fig. 3 Overlap modes of intrastack interactions in (TTM-TTP)AuI2 insulator with a dimerized structure. Fig. 5 shows the tempera- J. Mater. Chem., 1998, 8(2), 285–288 287Discussion The AuI2- and AuBr2- salts of TTM-TTP were obtained by the electrochemical crystal growth method similarly to (TTMTTP) I3.These salts have the same 151 composition as the I3- salt. These salts, however, have the dimerization of the donor molecules along the stacking direction. Therefore the energy gap appears at the Fermi level, and these salts become insulators.The observed conducting behaviors agree with this expectation from the crystal structure. The application of chemical pressure, namely the use of shorter anions, induces dimerization. In contrast, a naive prediction suggests that a uniform structure is generally more Fig. 4 Tight-binding energy band structure of (TTM-TTP)AuI2 calcupreferable under pressure, as most Peierls transitions are lated from the overlap of the HOMO obtained on the basis of the suppressed under pressure. Although the AuI2- anion (9.4 A ° ) extended Hu� ckel molecular orbital calculation is shorter than the I3- anion (10.1 A ° ),14 the lattice volume of the AuI2- salt is larger than twice that of the I3- salt.On the other hand the lattice constant c of the AuI2- salt is signifi- cantly shorter than twice that of the I3- salt.In these salts the linear anions are placed almost parallel to the intermolecular vector between the centers of dimerized molecules, and so are slightly inclined from the stacking direction. Therefore it is considered that the shrinkage of the linear anion makes crystal packing with a uniform stacking similar to the I3- salt impossible, and gives rise to the change of the stacking pattern, resulting in the dimerization.As a result the AuI2- salt becomes a band insulator. The lattice volume, however, increases owing to the change of the stacking pattern. Thus we cannot use shorter anions as a source of chemical pressure in the present case. The dimerization of the present compounds can be regarded as ‘chemically induced’ Peierls instability.One of the greatest mysteries in (TTM-TTP)I3 is the absence of the Peierls trans- Fig. 5 Temperature dependence of electrical resistance of (TTMition. Here we have encountered such an instability entirely TTP)AuI2 and (TTM-TTP)AuBr2 unexpectedly. References 1 Y. Misaki, H. Fujiwara, T. Yamabe, T. Mori, H. Mori and S. Tanaka, Chem. L ett., 1994, 1653. 2 T. Mori, Y. Misaki, H. Fujiwara and T. Yamabe, Bull. Chem. Soc. Jpn., 1994, 67, 2685. 3 T. Mori, T. Kawamoto, Y. Misaki, K. Kawakami, H. Fujiwara, T. Yamabe, H. Mori and S. Tanaka, Mol. Cryst. L iq. Cryst., 1996, 284, 271. 4 Y. Misaki, N. Higuchi, H. Fujiwara, T. Yamabe, T. Mori, H. Mori and S. Tanaka, Angew. Chem., Int. Ed. Engl., 1995, 34, 1222. 5 Y. Misaki, H. Nishikawa, T.Yamabe, T. Mori, H. Mori and S. Tanaka, Synth.Met., 1995, 70, 1153. 6 T. Mori, H. Inokuchi, Y. Misaki, T. Yamabe, H. Mori and S. Tanaka, Bull. Chem. Soc. Jpn., 1994, 67, 661. 7 T. Mori, T. Kawamoto, J. Yamaura, T. Enoki, Y. Misaki, Fig. 6 Temperature dependence of thermoelectric power of (TTMT. Yamabe, H. Mori and S. Tanaka, Phys. Rev. L ett., 1997, 79, TTP)AuI2 and (TTM-TTP)AuBr2 1702. 8 Y. Misaki, H. Nishikawa, K. Kawakami, S. Koyanagi, T. Yamabe ture dependence of electrical resistance of (TTM-TTP)AuI2 and M. Shiro, Chem. L ett., 1992, 2321. and (TTM-TTP)AuBr2 at ambient pressure. These salts were 9 G. M. Sheldrick, Crystallographic Computing 3, Oxford University semiconductors below room temperature. From the incli- Press, Oxford, 1985, pp. 175–189. 10 D.T. Cromer and J. T. Waber, International T ables for X-Ray nations of the straight lines in this figure, the activation energies Crystallography, Kynoch Press, Birmingham, 1974, vol. 4, are extracted to be 0.03 eV for the AuI2- salt, and 0.07 eV for Table 2.2 A. the AuBr2- salt. This semiconducting behavior is in agreement 11 T. Mori, A. Kobayashi, Y. Sasaki, H. Kobayashi, G. Saito and with the energy band calculation. H. Inokuchi, Bull. Chem. Soc. Jpn., 1984, 57, 627. Thermoelectric power (Seebeck coeYcient) of the AuI2- and 12 H. Kobayashi, R. Kato, T. Mori, A. Kobayashi, Y. Sasaki, AuBr2- salts were measured as shown in Fig. 6. The sign of G. Saito, T. Enoki and H. Inokuchi, Mol. Cryst. L iq. Cryst., 1984, 107, 33. the thermopower is negative in both salts. This means that the 13 P. M. Chaikin, R. L. Greene Etemad and E. Engler, Phys. Rev. mobility of electrons is higher than that of holes. The value of B., 1976, 13, 1627. |Q| is proportional to 1/T as the temperature decreases, as 14 J. M. Williams, J. R. Ferraro, R. J. Thorn, K. D. Carlson, U. Geiser, expected in a semiconductor.13 From Fig. 6 activation energies H. H. Wang, A. M. Kini and M.-H. Whangbo, Organic are estimated to be 0.08 eV for the AuI2- salt, and 0.05 eV for Superconductors (Including Fullerenes): Synthesis, Structure, the AuBr2- salt. Properties, and T heory, Prentice Hall, NJ, 1992. Paper 7/03200E; Received 9th May, 1997 288 J. Mater. Chem., 1998, 8(2), 285–288

ISSN:0959-9428    

DOI:10.1039/a703200e

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Azulene-substituted TTF derivatives† Hiroshi M. Yamamoto, Jun-Ichi Yamaura and Reizo Kato* Institute for Solid State Physics, T he University of T okyo, RoppongiMinato-ku, T okyo 106, Japan In order to examine Little’s model for organic superconductors, several azulene-substituted TTF derivatives were synthesized. Measurements of the oxidation potentials using cyclic voltammetry (CV) provide their donor abilities.The molecular structure of AET (azulenoethylenedithiotetrathiafulvalene) was determined by X-ray analysis. Cation radical salts of synthesized donors with BF4-, ClO4-, PF6-, AsF6- and [Pt(dmit)2]n- (dmit=C3S52-=2-thioxo-1,3-dithiole-4,5-dithiolate) were prepared by galvanostatic electrolyses. Temperature-dependent electrical resistances indicate that these salts are all semiconductive.The crystal structure of (AET)2[Pt(dmit)2] was determined by X-ray analysis and its electronic structure is discussed. Organic molecular conductors have been the subject of considerable interest in physics and chemistry because of their stimulating properties such as their charge density wave,1 field induced spin density wave,2 spin-Peierls transition3 and superconductivity. 4 In order to reach the superconducting state, a finite value of the density of state should be maintained and thus the metal–insulator transition should be suppressed down to low temperature. Considering that the low-dimensional nature of the system induces a metal–insulator transition, one can understand that an increase of dimensionality of the electronic structure is the current focus in developing molecular superconductors.This strategy has led to the preparation of many molecular conducting materials that exhibit various types of Fermi surfaces.5 Some of these materials such as BEDT–TTF [bis(ethylenedithio)tetrathiafulvalene] salts show superconducting behaviour.6 It is obvious, however, that the properties of superconductivity, for example the critical temperature (Tc), are governed not only by the geometry of the Fermi surface but also by many other factors.7 Little has pointed out that the Tc of organic superconductors can rise to room temperature via a special mechanism.8 Fig. 1 illustrates his model, a polyacetylene chain substituted by cyanine dye. First, conduction electrons excite the positive charge of the side chains to approach close to the chain backbone. Second, the positive charge attracts another electron and thus provides an attractive force for electrons.Finally, this attractive force brings about the superconductivity. R R R R R N N Et N N Et N N Et R = + – – Therefore, an oscillation of positive charge on the side chain Fig. 1 Illustration of Little’s model for high-temperature supertakes the place of the phonon in the BCS theory.9 In other conductivity words, the conventional electron–phonon interaction mechanism is replaced by an electron–exiton mechanism, based on TTF derivatives. We selected the TTF moiety as a conduction electronic polarization eVects. path, and the azulene ring as a source of oscillating dipole.The high Tc in Little’s calculation is achieved because the Our choice of azulene was based on the following. (i ) Because mass of the electron is much smaller than that of nuclei which azulene consists of five- and seven-membered rings, the 6p can be regarded as an extension of the isotope eVect on the Tc aromatic stabilization eVect on each ring gives rise to a charge of superconductivity.We can, therefore, make use of the separation in the ground state10 [Fig. 2(a)]. Azulene therefore electronic polarization component of permeability instead of has a significant dipole moment with the negative charge on the ionic part. Electronic polarization has a higher energy than the five-membered ring in the ground state11 (1.08 Debye). In ionic polarization so Tc calculated using Little’s theory should addition, since the coeYcients of its LUMO have a tendency be higher than the conventional one.to gather on the seven-membered ring [Fig. 2(b)], azulene in Little’s polymer has not yet been prepared due to synthetic the excited state has a dipole moment in the opposite direc- diYculties, although we still consider the theory very attractive.tion12 (-0.42 Debye). Thus the excitation of an electron on We, therefore, planned to substitute an array of organic radicals an azulene ring will change the electric environment of the for the polyacetylene in order to make his proposal syntheticonduction carriers on the TTF moiety. (ii ) Excitation of an cally accessible. To this end, we designed azulene-substituted electron from the HOMO to the LUMO requires little energy (1.8 eV) because the excitation reduces the mutual repulsion between electrons.10 This small excitation energy enables the † Presented at the 58th Okazaki Conference, Recent Development conduction carriers on the TTF moiety to utilize the azulene and Future Prospects of Molecular Based Conductors, Okazaki, Japan, 7–9 March 1997.ring as a source of the oscillating dipole. J. Mater. Chem., 1998, 8(2), 289–294 289Table 1 Cyclic voltammetric data for new donors donor E1/Va E2/Va DE/V=E2-E1 BEDT TTF 0.12 0.43 0.31 5a 0.17 0.49 0.32 5b 0.15 0.44 0.29 5c 0.16b 0.47b 0.34 5d 0.24b 0.53b 0.29 HOMO LUMO ( a ) (b ) 5e 0.44c 0.84c 0.40 Fig. 2 (a) Charge separation in the azulene ring at its ground state; 5f 0.24c 0.63c 0.39 (b) schematic representation of the coeYcients of the azulene HOMO and LUMO aVs.Ag/AgNO3 , benzonitrile, 22 °C, Pt working and counter electrodes. bQuasi-reversible. cIrreversible (E1 and E2 values were determined by diVerential pulse polarography). The azulene ring attached to the TTF moiety can thus act as an oscillating dipole. The interaction between conduction carriers on the TTF and the oscillating dipole on the azulene probably owing to undesired reaction at the azulene ring.Donor 5a (AET) and 5b show oxidation potentials similar to ring should make carriers attractive to each other leading to superconductivity. With this in mind, we have examined those of BEDT–TTF, in spite of the introduction of the electron-withdrawing azulene ring.This result ensures the azulene-substituted TTF derivatives and this article describes the syntheses, electrochemistry, visible absorption, X-ray analy- donor ability of these donors. The substitution of selenium for outer sulfur (5c) does not aVect the potentials significantly, but sis and MO calculations of such TTF derivatives as well as the electrical properties and X-ray analysis of their cation replacement of inner sulfur (5d) positively shifts both E1 and E2 values.The high E1 and E2 values for 5e can be attributed radical salts. to the electron-withdrawing character of the thiadiazole ring. The molecular structure of AET was determined by single Results and Discussion crystal X-ray analysis (Fig. 3, Tables 2, 3). The CMC bond lengths in the azulene ring are almost equal (about 1.4 A ° ).This Synthesis and properties of neutral donors suggests that the aromaticity of the ring is retained even if the The synthetic route is presented in Scheme 1. 5,6- Dichloroazulene 1 is converted to trithiocarbonate 3 by the nucleophilic attack of potassium sulfide and subsequent intramolecular ring closure in potassium trithiocarbonate 2.Azulene-substituted TTF derivatives 5a–5f were synthesized by the cross-coupling reactions of units 4a–4f with azulenecontaining unit 3 using neat triethyl phosphite. The symmetrical donor, diazuleno–TTF, was also synthesized by the same method, but it was not characterized in detail because it is a mixture of cis and trans forms. The yields of coupling reactions were moderate except for the low yield of 5e.Replacement of the thioketone in the unit 4e with the ketone did not improve the reaction yield. This low yield was due to the decomposition of the thiadiazole ring. The electrochemical properties of donors 5a–5f have been studied by cyclic voltammetry (CV) and the results are listed in Table 1, along with the data for BEDT–TTF as a reference Fig. 3 (a) Side view of the AET; (b) top view of the AET; (c) crystal compound. Some of the observed redox peaks were irreversible packing of the AET Table 2 Crystallographic data for AET and (AET)2[Pt(dmit)2] AET (AET)2[Pt(dmit)2] empirical formula C16H10S6 C38H20PtS22 formula mass 394.61 1376.99 colour & shape dark brown brownish black plate block crystal system monoclinic monoclinic space group P21/n P21/n a/A° 19.104(4) 11.619(3) b/A ° 13.057(3) 30.222(4) c/A ° 6.515(2) 6.547(1) b (°) 93.16(2) 97.62(2) V /A ° 3 1622.5(6) 2278.7(7) Z 4 2 total no.of observed 4224 5218 reflections no. of unique data 2123 3640 with I3s(I) no. of variables 239 288 R; Rw 0.046; 0.032 0.042; 0.044 maximum peak in 0.35e 1.49e final diV. map/A ° 3 minimum peak in -0.39e -1.88e Cl Cl S S S S S X X X X Y R R R R Cl S S–K+ S K2S, CS2 1 3 (30%) 5a – f 4a – f P(OEt)3 H2O–DMF, 60 °C 2 a X = S, Y = O, R–R = SCH2CH2S 44% b X = S, Y = O, R–R = SCH2S 49% c X = S, Y = O, R–R = SeCH2CH2Se 34% d X = Se, Y = O, R–R = SCH2CH2S 38% e X = S, Y = S, R–R = 5% f X = S, Y = O, R = I 17% NSN final diV.map/A° 3 Scheme 1 290 J. Mater. Chem., 1998, 8(2), 289–294Table 3 Selected bond lengths (d/A° ) for (AET)2[Pt(dmit)2] AET Pt(dmit) C(1)MC(2) 1.303(9) PtMS(7) 2.270(2) S(1)MC(1) 1.763(6) PtMS(8) 2.273(2) S(2)MC(1) 1.759(7) S(7)MC(17) 1.716(6) S(1)MC(5) 1.742(7) S(8)MC(18) 1.694(7) S(2)MC(6) 1.780(7) C(17)MC(18) 1.366(8) S(3)MC(2) 1.749(7) S(9)MC(17) 1.735(6) S(4)MC(2) 1.759(6) S(10)MC(18) 1.746(6) S(3)MC(3) 1.751(7) S(9)MC(19) 1.737(7) S(4)MC(4) 1.751(7) S(10)MC(19) 1.726(7) C(3)MC(4) 1.339(9) S(11)MC(19) 1.640(7) Table 4 Resistivity of cation radical salts donor (D) anion (A) D5A rrt/V cm Ea/meV S S S S S S S S S S S S S ( a ) (b ) (c ) 5a BF4- — 0.6 45 Fig. 5 Schematic representation of the coeYcients of the AET for ClO4- — 0.3 52 (a) next-HOMO, (b) HOMO and (c) LUMO PF6- 251a 0.4 50 AsF6- 251a 2 62 Although this situation would reduce the dipole oscillating Pt(dmit)2- 251 10b 120 eVect of the azulene moiety, it is still possible that the excitation 40c 120 5c PF6- 251a 3 63 of an electron from the HOMO or the next-HOMO to the 5d PF6- 251a 1 23 LUMO causes a change of electric potential at the TTF moiety 5f PF6- 351a 10 67 and thus an attractive interaction between conduction electrons. aDetermined by EPMA measurement.bMeasured along the a axis. cMeasured along the c axis. Properties of cation radical salts Cation radical salts of new donors were prepared by galvano- ring is attached to the TTF moiety.13 This fact is also supported static oxidation with various kinds of counter anions such as by the absorption in the visible region, which is characteristic BF4-, ClO4-, PF6-, AsF6- and [Pt(dmit)2]n-.All these salts of the azulene ring14 (Fig. 4). The CNC bond lengths as well show rather small resistivities but are semiconductive above as the CMS bond lengths in the TTF moiety show normal room temperature with small activation energies (Table 4). values compared to those in the known neutral TTF Since the quality of the crystals is not so good in general, derivatives.15 The molecular plane bends slightly at S(3) and X-ray structural analysis was performed only for S(4), which is the same with the molecular structure of the (AET)2[Pt(dmit)2].Crystal data are summarized in Table 2. neutral BEDT–TTF.15 There is a positional disorder in the The unit cell contains two mixed columns which are crystallo- terminal ethylenedithio fragment as reflected by the elongated graphically equivalent (Fig. 6). In each column, a repeating thermal ellipsoid for C(7) and C(8) as well as slightly larger unit consists of two AET molecules and one Pt(dmit)2 mol- atomic displacement parameters (Beq=5.19 and 4.58, respectecule. The two AET molecules are interrelated by the inversion ively) of S(5) and S(6). AET molecules are dimerized and the centre and the Pt(dmit)2 molecule is located on the inversion molecules in the dimer are interrelated by the inversion centre centre.The AET molecule is almost planar and there is no as shown in Fig. 3(c). No S,S contact shorter than the sum positional disorder at the terminal ethylene group. Interplanar of the van der Waals radii (3.60 A ° ) is observed among the distances are 3.4 A ° between AET molecules and 3.7 A ° between donor molecules.AET and Pt(dmit)2 molecules. Short intermolecular S,S The molecular orbitals of AET have been calculated by a distances are observed only between AET molecules arranged semiempirical method (MOPAC: PM3 hamiltonian) using the in a side-by-side fashion (Fig. 7). coordinates of neutral AET obtained by X-ray analysis (Fig. 5). The bond lengths in the TTF moiety are known to be The coeYcients of the LUMO are distributed on the azulene sensitive to the formal charge, and oxidation of TTF should moiety, and its electronic structure is approximately the same result in an increase of the central CNC bond length.16 The as that of the simple azulene [cf. Fig. 2(b)]. On the other hand, central C(1)MC(2) bond length of AET is slightly shorter than the coeYcients of the HOMO and the next-HOMO are that of the neutral AET, and other bond lengths within the distributed on both azulene and TTF moieties, presumably TTF moiety are almost the same as those in the neutral one because their energy levels are very close to each other.(Table 3). This means that the AET molecule is nearly neutral in this crystal.As for the formal charge of [Pt(dmit)2]n-, it is diYcult to discuss a diVerence of the formal charge from its PtMS bond lengths,17 although a diVerence of the oxidation state from n=2 to n=0 is expected to result in a decrease of Fig. 4 Visible spectrum of (a) AET and (b) 5,6-dichloroazulene Fig. 6 Crystal packing in (AET)2[Pt(dmit)2] J. Mater. Chem., 1998, 8(2), 289–294 291Fig. 7 (a) Overlapping mode of donor molecules; (b) side-by-side contacts between donor molecules in the (AET)2[Pt(dmit)2] crystal Fig. 9 Band dispersion of (AET)2[Pt(dmit)2] calculated by the tightbinding method. The level of the AET HOMO is the origin of energy. be noted that the ordinary mixed-stack system is a semiconductor, even if there is enough charge transfer.If the transverse interactions are enhanced, however, the system can achieve a metallic band structure.19 Indeed, when small DE values are adopted, our system exhibits a Fermi surface. Therefore, it would be possible to obtain a metallic system by the choice of an appropriate acceptor. Conclusion Fig. 8 Molecular arrangement viewed along the b axis We have proposed that Little’s high-temperature superconductivity theory can be applied to molecular conductors.The this bond length. The PtMS bond lengths (about 2.27 A° ) are azulene moiety of the donor AET retains the electronic struc- shorter than those in TTF[Pt(dmit)2]3 (about 2.30 A ° ),18 ture of the simple azulene, although partial mixing of the which suggests that the Pt(dmit)2 molecule in our crystal is azulene HOMO and the TTF HOMO was suggested by approximately neutral.semiempirical MO calculations. At present, unfortunately, Intermolecular overlap integrals among frontier orbitals cation radical salts of the donors are all semiconductive. The [HOMO for AET and LUMO for Pt(dmit)2] illustrated in crystal and electronic structures of (AET)2[Pt(dmit)2] suggest Fig. 8 are shown in Table 5.One unknown band parameter is one condition for the metallic state. Research towards the the energy diVerence (DE) between the LUMO and HOMO. achievement of the metallic state is in progress. Considering that the amount of charge transfer from AET to Pt(dmit)2 is small and the system is a semiconductor with a band gap (Eg) of 0.24 eV [Eg is twice as large as the activation Experimental energy (Ea=0.12 eV)], the DE value is estimated to be about 0.3 eV so that Eg is consistent with the resistivity measurement.All reactions were carried out under an Ar atmosphere. 5,6- It has been assumed that the transfer integral (t) is proportional Dichloroazulene20 and units 4a–4f21–24 were synthesized to the overlap integral (S), t=eS (e=-10 eV, e is a constant according to the methods described in the literature. with the order of the orbital energies of the HOMO and LUMO).The band structure was calculated based on the Azuleno[5,6-d]-[1,3]-dithiole-2-thione 3 tight-binding approximation and is displayed in Fig. 9. The highest-lying (mainly) LUMO band is separated far from the A dimethylformamide (DMF) (300 ml) solution of 5,6-di- (mainly) HOMO bands.Since the degree of the band filling is chloroazulene (10.10 g, 51.3 mmol) was added dropwise into 2/3, the system is a semiconductor with an energy gap. In this an aqueous solution (30 ml ) of potassium sulfide (8.51 g, case, the large DE value (and thus small charge transfer) is one 77.2 mmol) at room temp. After 15 min, carbon disulfide of the main causes of the semiconductive behaviour.It should (50 ml ) was also added and the reaction mixture was stirred at 60 °C for 16 h. The resultant mixture was poured into Table 5 Intermolecular overlap integrals (S) of frontier orbitals in benzene (1 l ), and filtered through Celite. This benzene solution (AET)2[Pt(dmit)2] was washed with water (500, 300, 300 ml), and dried with MgSO4. The solvent was removed under reduced pressure, S/10-3 and the silica gel column chromatography with carbon disulfide as eluent gave pure 3 (3.57 g, 30%) as green fibres.Mp a1 -5.41 a2 -4.54 151–154 °C (decomp.) (Calc. for C11H6S3: C, 56.37; H, 2.58. c1 -0.079 Found: C, 56.29; H, 2.77%); (HRMS: Calc. 233.9632. Found c2 -1.31 233.9603); dH (CDCl3–CS2) 7.13 (1H, d, J 10.2), 7.35 (1H, d, p -0.62 J 4.0), 7.42 (1H, d, J 3.7), 7.86 (1H, t, J 3.8), 8.13 (1H, d, q -1.02 J 10.6), 8.20 (1H, s) (J values in Hz throughout). 292 J. Mater. Chem., 1998, 8(2), 289–294Table 6 Semiempirical parameters for Slater-type atomic orbitals Synthesis of donors 5a–5f: general procedure A triethyl phosphite (5 ml) solution of 3 (1 mmol) and unit S C H Pt 4a–4f was heated to 100 °C for 30 min.It was cooled to room 3s 3p 2s 2p 1s 6s 6p 5da temp., methanol (30 ml ) was added and the reaction mixture filtered through a glass filter. The brown solid obtained was f1 2.12 1.83 1.63 1.63 1.30 2.55 2.55 6.01(0.633) purified by silica gel chromatography with carbon disulfide as z2 2.70(0.551) eluent to aVord pure 5a–5f. -Ip/eV 1.47 0.79 1.57 0.84 1.0 0.67 0.40 0.93 aTwo Slater exponents were used for the 5d functions.Each is followed 2-(Azuleno[5,6-d][1,3]dithiol-2-ylidene)-5,6-dihydro-1,3-diin parentheses by the coeYcient in the double zeta expansion. thiolo[4,5-b][1,4]dithiine 5a. 44%, mp>300 °C (Calc. for C16H10S6: C, 48.69; H, 2.55. Found: C, 48.69; H, 2.73%) Electrical resistivity measurements (HRMS: Calc. 393.9107. Found 393.9127); dH (CDCl3–CS2) 3.27 (4H, d, J 1.3), 6.97 (1H, d, J 9.9), 7.14 (1H, d, J 4.3), 7.21 The direct current resistivity measurements were performed (1H), 7.70 (1H, t, J 3.8), 7.93 (1H, d, J 10.2), 8.04 (1H, s).with the standard four-probe method. Gold leads (15 mm diameter) were attached to the crystal with carbon paste. 2-(Azuleno[5,6-d][1,3]dithiol-2-ylidene)-1,3-dithiolo[4,5-d]- [1,3]dithiole 5b. 49%, mp>300 °C (Calc. for C15H8S6: C, 47.33; Crystal structure analysis H, 2.73. Found: C, 47.08; H, 2.28%) (HRMS: Calc. 379.8950. Found 379.8940); dH (CDCl3–CS2) 4.95 (2H, s), 6.97 (1H, d, J X-Ray diVraction data for AET were collected on a MAC 10.2), 7.14 (1H, d, J 4.3), 7.22 (1H), 7.69 (1H, t, J 3.8), 7.94 Science automatic four-circle diVractometer (MXC18) with (1H, d, J 10.2), 8.02 (1H, s).graphite-monochromated Mo-Ka radiation up to 2h=60°. The intensities were corrected for Lorenz and polarization eVects. 2-(Azuleno[5,6-d][1,3]dithiol-2-ylidene)-5,6-dihydro-1,3-di- The data for (AET)2[Pt(dmit)2] were collected on a MAC thiolo[4,5-b][1,4]diselenine 5c. 34%, mp 286–289 °C (decomp.) Science Weissenberg-type imaging plate system (DIP320S). (Calc.for C16H10S4Se2: C, 39.34; H, 2.06. Found: C, 39.19; The cell constants were refined by the four-circle diVractometer H, 2.19%); dH (CDCl3–CS2) 3.35 (4H, s), 6.96 (1H, d, J 10.2), with monochromated Mo-Ka radiation up to 2h=60°. 7.11 (1H, d, J 4.0), 7.20 (1H, d, J 3.6), 7.66 (1H, t, J 3.8), 7.92 The structures were solved by direct methods and refined (1H, d, J 9.5), 8.00 (1H, s).using full-matrix least-squares analysis using reflections with I3s(I). An analytical absorption correction was carried out 2-(Azuleno[5,6-d][1,3]dithiolo-2-ylidene)-5,6-dihydro-1,3- for AET. Anisotropic atomic displacement parameters were diselenolo[4,5-b][1,4]dithiine 5d. 38%, mp 225–228 °C used for non-hydrogen atoms. All calculations were performed (decomp.) (Calc. for C16H10 S4Se2: C, 39.34; H, 2.06.Found: using TEXSAN the crystallographic software package from C, 39.18; H, 2.16%); dH (CDCl3–CS2) 3.30 (4H, s), 6.95 (1H, Molecular Structure Co. d, J 10.3), 7.14 (1H, d, J 3.8), 7.23 (1H), 7.69 (1H, t, J 4.0), 7.94 (1H, d, J 9.6), 8.00 (1H, s). MO calculations The molecular orbital calculation was performed using 4-(Azuleno[5,6-d][1,3]dithiol-2-ylidene)-[1,3]dithiolo[4,5- MOPAC93 included in CHEM3D from Cambridge Science c][1,2,5]thiadiazole 5e. 5%, mp 268–272 °C (decomp.) (Calc. Co. The calculation was carried out with the option C.I.=4. for C14H6N2S5: C, 46.38; N, 7.73; H, 1.67. Found: C, 46.64; In order to calculate intermolecular overlap integrals, the N, 7.45; H, 1.96%) (HRMS: Calc. 361.9135. Found 361.9148); HOMO obtained from the extended Hu�ckel MO calculation dH (CDCl3–CS2) 7.02 (1H, d, J 10.2), 7.19 (1H, d, J 3.7), 7.27 was used.The calculation was carried out with the use of (1H, d, J 3.3), 7.73 (1H, t, J 3.6), 7.99 (1H, d, J 10.2), 8.06 semiempirical parameters for Slater-type atomic orbitals25 (1H, s). (Table 6). 2-(4,5-Diiodo-1,3-dithiol-2-ylidene)azuleno[5,6-d][1,3]- The authors are grateful to Takeda Chemical Industry Co.dithiole 5f. 17%, mp>300 °C (Calc. for C14H6I2S4: C, 30.23; Ltd. for the supply of 3,3,4,4-tetrachlorothiophene 1,1-dioxide H, 1.09. Found: C, 30.15; H, 1.16%); dH (CDCl3–CS2) 6.96 as a starting material for 5,6-dichloroazulene. (1H, d, J 10.3), 7.13 (1H, d, J 3.3), 7.20 (1H), 7.68 (1H, t, J 4.0), 7.93 (1H, d, J 10.9), 7.99 (1H, s). References Cyclic voltammetry measurements 1 K.Kagoshima, H. Anzai, K. Kajimura and T. Ishiguro, J. Phys. The cyclic voltammetry experiments were all performed under Soc. Jpn., 1975, 39, 1143; F. Denoyer, F. Come`s, A. F. Garito and argon atmosphere at room temp. A solution of tetra(n-butyl )- A. J. Heeger, Phys. Rev. L ett., 1975, 35, 445. ammonium perchlorate–benzonitrile (0.1 M), Pt working and 2 J.F. Kwak, J. E. Schirber, R. L. Greene and E. M. Engler, Phys. Rev. L ett., 1981, 46, 1296. auxiliary electrodes were used. Potentials were referenced vs. 3 J. W. Bray, H. R. Hart, Jr., L. V. Interrante, I. S. Jacobs, Ag/0.01 M AgNO3. Sweep rate was 100 mV s-1 in every J. S. Kasper, G. D.Watkins, S. H.Wei and J. C. Bonner, Phys. Rev. experiment. L ett., 1975, 35, 744. 4 D.Jerome, A. Mazaud, M. Ribault and K. Bechgaard, J. Phys. Preparations of cation radical salts L ett. (Paris), 1980, 41, 95. 5 J. Wosnitza, Fermi Surfaces of L ow-Dimensional Organic Metals Cation radical salts of 5a–5f were obtained by galvanostatic and Superconductors, Springer Tracts in Modern Physics vol. 134, oxidation of a solution containing the donor (ca. 8 mg) and Springer, Berlin, 1996. the corresponding supporting electrolyte (35–70 mg) as tetra(n- 6 J.M.Williams, J. R. Ferraro, R. J. Thorn, K. D. Carlson, U. Geiser, H. H. Wang, A. M. Kini and M. H. Whangbo, Organic butyl)ammonium salts in 1,1,2-trichloroethane (20 ml, contain- Superconductors (Including Fullerenes): Synthesis, Structure, ing 5% of ethanol as stabilizing reagent) under an argon Properties and T heory, Prentice Hall, Englewood CliVs, NJ, 1992.atmosphere at 20 °C. An H-shaped cell and platinum wire 7 Organic Superconductivity, ed. V. Z. Kresin and W. A. Little, electrodes (1 mm diameter) were employed and a constant Plenum Press, New York, 1990. current (0.5 mA) was applied for 1–4 weeks. Crystals formed 8 W. A.ittle, Phys. Rev., 1964, 134, A1416. in the anode compartment were collected and washed with 9 J.Bardeen, L. N. Cooper and J. R. SchrieVer, Phys. Rev., 1957, 108, 1175. acetone and n-hexane. J. Mater. Chem., 1998, 8(2), 289–294 29310 D. M. Lemal and G. D. Goldman, J. Chem. Educ., 1988, 65, 923. 18 M. Bousseau, L. Valade, J. P. Legros, P. Cassoux, M. Garbauskas and L. V. Interrante, J. Am. Chem. Soc., 1986, 108, 1908. 11 G. W. Wheland and D. E. Mann, J. Chem. Phys., 1949, 17, 264; 19 H. Kobayashi, R. Kato, A. Kobayashi and Y. Sasaki, Chem. L ett., A. G. Anderson and B. M. Steckler, J. Am. Chem. Soc., 1959, 1985, 191. 81, 4941. 20 S. E. Reiter, L. C. Dunn and K. N. Houk, J. Am. Chem. Soc., 1977, 12 R. M. Hochstrasser and L. J. Noe, J. Chem. Phys., 1969, 50, 1684. 99, 4199. 13 J. M. Robertson, H. M. M. Shearer, G. A. Sim and D. G. Watson, 21 N. Svensrup and J. Becher, Synthesis, 1995, 215. Acta Crystallogr., 1962, 15, 1. 22 R. Kato, H. Kobayashi and A. Kobayashi, Synth. Met., 1991, 14 J. Brunken, Chem. Ber., 1960, 93, 2572; E. W. Thulstrup, P. L. Case 41–43, 2093. and J. Michl, Chem. Phys., 1974, 6, 410. 23 A. E. Underhill, I. Hawkins, S. Edge, S. B. Wilkes, K. S. Varma, 15 H. Kobayashi, A. Kobayashi, Y. Sasaki and G. Saito, Bull. Chem. A. Kobayashi and H. Kobayashi, Synth.Met., 1993, 55–57, 1914. Soc. Jpn., 1986, 59, 301. 24 T. Imakubo, PhD Thesis, University of Tokyo, 1996. 16 H. Kobayashi, A. Kobayashi, Y. Sasaki, G. Saito and H. Inokuchi, 25 R. H. Summerville and R. HoVmann, J. Am. Chem. Soc., 1976, Chem. L ett., 1984, 183. 98, 7240. 17 L. Valade, J. P. Legros, M. Bousseau, P. Cassoux, M. Garbauskas and L. V. Interrante, J. Chem. Soc., Dalton T rans., 1985, 783; G. N. Schrauzer, Acc. Chem. Res., 1969, 2, 72. Paper 7/03737F; Received 29th May, 1997 294 J. Mater. Chem., 1998, 8(2), 289–294

ISSN:0959-9428    

DOI:10.1039/a703737f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials X-Ray crystal structure, magnetic and electric properties of TTF trimer-based salts of FeCl4-, [TTF7(FeCl4)2]† Masanori Umeya, Satoshi Kawata, Hiroyuki Matsuzaka, Susumu Kitagawa,* Hiroyuki Nishikawa, Koichi Kikuchi and Isao Ikemoto Department of Chemistry, T okyoMetropolitan University,Minami-Ohsawa, Hachiouji, T okyo, 192–03, Japan A new TTF trimer-based charge transfer salt, TTF7(FeCl4)2, has been synthesized and characterized. It belongs to the monoclinic space group C2/m, M=1812.75, a=28.433(5), b=16.524(3), c=16.981(3) A ° , b=121.17(2)°, V=6826(2) A ° 3 and Z=4.The crystal structure shows the two types of layers O and I; the layer O is composed of two sets of TTF trimers orthogonal to each other, providing a two-dimensional interacting network of TTF molecules, while the layer I consists of TTF molecules and FeCl4 anions.The FeCl4 anions can interact magnetically with the TTF molecules in both the layers O and I because of the short S,Cl distance. Single-crystal temperature-dependent conductivity measurements show that this material is a semiconductor with a roomtemperature conductivity of 0.055 S cm-1 and a thermal activation energy of 0.15 eV.The temperature dependence of magnetic susceptibilities indicates antiferromagnetic behavior based on FeCl4- anions and radical cations. Two EPR signals were observed for the microcrystals; the broader signal aVorded a large temperature dependence of the g value ranging from 2.15 (292 K) to 1.86 (5 K). The development of metallic molecular crystals of charge- the crystal structures is associated with counteranions. In order to design new materials composed of transfer salts has attracted considerable interest of solid-state chemists because of the remarkable variety of crystal structures inorganic–organic substructures, it is important to investigate the relationship between counter-anions and the crystal struc- and physical properties.1 Among these synthetic eVorts one of the most exciting challenges is to prepare a new molecular tures well characterized by X-ray crystallography. Here, we report the synthesis, structure and properties of a new charged compound with interplay of magnetic and conducting properties.It is useful to take advantage of the ability of the state compound derived from [(FeCl4)2(m-C2O4)]4- and TTF, which consists of two layers constituted by TTF trimer units conduction electrons of a molecular metal to couple localized magnetic moments via an indirect exchange mechanism.In and FeCl4-/TTF units. molecular materials it is possible to build a hybrid material formed by a conducting part (typically, a TTF derivative) and Experimental by a magnetic part (typically, an inorganic d-transition metal complex).BEDT-TTF is such a candidate having various All operations were carried out under an atmosphere of packing structures (a, b, h, and so on), and often aVording a nitrogen by using standard Schlenk-tube techniques. Solvents metallic phase. Very recently, transition metal-based hybrid were purified by conventional methods and distilled under compounds of BEDT-TTF have been synthesized.2–9 Among nitrogen prior to use.these compounds (BEDT-TTF)4(H2O)[Fe(C2O4)3] C6H5CN3 is the first molecule-based magnetic superconductor with Synthesis of TTF7(FeCl4)2 BEDT-TTF layers alternating with inorganic layers of para- To a solution of 0.04 mmol (30 mg) of (H2trien)2[(FeCl4)2 magnetic tris(oxalato)iron(III ) anions.Another TTF derivative- (m-C2O4)] 2H2O17(H2trien=triethylenediammonium) in 10 ml based compound, (BETS)2FeCl4 [BETS=bis(ethylenedithio)- of methanol was added a solution of 0.64 mmol (75 mg) of tetraselenafulvalene], has shown unusual magnetic behavior TTF in 10 ml of acetone. The reaction mixture was stirred for associated with an interaction between the BETS molecule several minutes and then stood at room temperature for 4 and the FeCl4 anion.10 In these hybrid compounds, the packing weeks. Black needles and prisms were collected by filtration structure and charge state of the organic cations greatly depend and easily separated by hand (yield: 20%).Analysis: found C, on the combination of the organic cation and transition metal 27.69; H, 2.58; requires C, 27.63; H, 1.55%.complex anion, influencing the magnetic interaction between the transition metal complex anions via the organic cations. X-Ray data collection and structure determination Therefore, it is important to explore crystal structures relevant to this interaction by changing both organic cations and/or A prism crystal was glued on the top of a glass fiber.The transition metal complex anions. The packing modes of TTF structure at 243 K was determined by using the 2928 signifi- salts reported are one-dimensional (1-D) stacking,11,12 discrete cant reflections (|Fo|>3s|Fo|), which were collected on a dimer structure,12,13 and two-dimensional (2-D) structure,14–16 Weissenberg-type Rigaku X-Ray imaging plate system (Rwhich consists of TTF trimers.The charge state of TTF AXIS 4). The structure was solved by direct methods (Rigaku molecule in these TTF trimers is +2/3. The conductor anions TEXSAN crystallographic software package of Molecular of d-transition metal complexes found in these TTF salts are Structure Corporation). Full-matrix least-squares refinements CoCl42-, MnCl42- and ZnCl42-.15 Accordingly, the variety of were carried out with anisotropic thermal parameters for all non-hydrogen atoms.All the hydrogen atoms were located in a diVerence Fourier map and introduced as fixed contributors † Presented at the 58th Okazaki Conference, Recent Development in the final stage of the refinement. Residuals at convergence and Future Prospects of Molecular Based Conductors, Okazaki, Japan, 7–9 March 1997.are quoted on |F|. J. Mater. Chem., 1998, 8(2), 295–300 295Table 1 Crystallographic data for TTF7(FeCl4)2 Table 4 Comparison of FeMCl bond distances and ClMFeMCl angles in FeCl4- chemical formula C42H28Cl8Fe2S28 formula mass 1812.75 compound FeMCl/A ° ClMFeMCl/degrees space group C2/m (no. 12) a/A ° 28.433(5) TTF7(FeCl4)2 2.290–2.326 103.3–120.1 (BEDT-TTF)2FeCl4 a 2.174–2.186 107.7–110.2 b/A ° 16.524(3) c/A ° 16.981(3) (l-BETS)2FeCl4 b 2.166–2.178 107.1–113.5 (k-BETS)2FeCl4 b 2.174–2.193 107.7–112.7 b/degrees 121.17(2) V /A ° 3 6826(2) Z 4 aRef. 4. bRef. 10. Dc/g cm-3 1.78 F(000) 3664.00 T /K 243 with a modulation frequency of 100 kHz and modulation l(Mo-Ka)/A ° 0.71069 amplitude of 0.5 mT, throughout. m(Mo-Ka)/cm-1 16.3 The magnetic susceptibility data were recorded over the 2hmax/degrees 51.4 Ra 0.041 temperature range 2–300 K at 0.1 T with a SQUID suscepto- Rw b 0.051 meter (Quantum Design, San Diego, CA) interfaced with an goodness of fit 1.504 HP computer system.All the data were corrected for diamagnetism which were calculated from Pascal’s tables. aR=.||Fo|-|Fc||/.|Fo|. bRw=[.w(|Fo|-|Fc|)2/.wFo2]D.Laser Raman spectra were recorded with Ar+ ion excitation (514.5 nm) using a Jasco R-600 spectrometer. A 90° scattering Table 2 Central CNC and CMS bond distances (A ° ) of TTF molecules geometry was employed. A–G typea ra rb rc rd re Results and Discussion A 1.36(2) 1.756(6) 1.756(6) 1.756(6) 1.756(6) Crystal structure B 1.36(2) 1.751(7) 1.751(7) 1.751(7) 1.751(7) The packing system of TTF7(FeCl4)2 is similar to that of the C 1.33(1) 1.754(9) 1.742(8) 1.750(9) 1.739(10) D 1.33(2) 1.71(1) 1.73(1) 1.74(1) 1.76(1) TTF14(MCl4)4 series.15 The TTF molecules and FeCl4 anions E 1.35(2) 1.752(8) 1.752(8) 1.734(8) 1.734(8) are shown in Fig. 1 with the labeling scheme. The crystal F 1.34(2) 1.732(8) 1.732(8) 1.739(8) 1.739(8) structure consists of alternating TTF trimer layers (type O) G 1.33(2) 1.755(7) 1.755(7) 1.757(7) 1.757(7) and FeCl4-/TTF layers (type I), both of which are parallel to the bc plane.The molecular arrangements of the two types of aThe labels A–G correspond to those of TTF molecules in Fig. 2(a) the layers are shown in Fig. 2(a) and (b). The side-view (down and (b). the b-axis) of these layers is shown in Fig. 2(c). The type I layer contains two crystallographically independent TTF molecules [labeled A and B in Fig. 2(a)] and one independent FeCl4 anion. The formal composition of the type I layer is TTFATTFB(FeCl4)4. The A- and B-type TTF molecules sit S S S S ra rb rc rd re parallel to the bc plane. On the other hand, the layer O contains five crystallographically independent TTF molecules Table 3 Bond distances (A ° ) and angles (degrees) for FeCl4- denoted C, D, E, F and G in Fig. 2(b), which form the two groups of trimers, (1) and (2), orthogonal to each other. Fe(1)MCl(1) 2.290(3) Cl(1)MFe(1)MCl(2) 105.9(1) The formal composition of the layer O is thus Fe(1)MCl(2) 2.326(3) Cl(1)MFe(1)MCl(4) 105.9(1) Fe(1)MCl(3) 2.311(3) Cl(1)MFe(1)MCl(3) 117.5(1) TTFCTTFETTFFTTFG(TTFD)2. Fe(1)MCl(4) 2.308(3) Cl(2)MFe(1)MCl(4) 120.1(1) The central CNC and CMS bond distances (r) for TTF Cl(2)MFe(1)MCl(3) 103.3(1) molecules (A–G) are listed in Table 2.Generally oxidized Cl(3)MFe(1)MCl(4) 105.0(1) TTFn+ (0<n<1) molecules have the CNC distance ranging from 1.31 to 1.40 A ° .11,13,18 The observed distances ra in Table 2 fall within the range of 1.33–1.36 A ° indicative of a TTFn+ A summary of the crystallographic data, anisotropic param- (0<n<1) state.The ra values for TTFA and TTFB in layer I eters, and selected bond distances and angles are listed in show the longest distance of 1.36 A ° , implying a TTF+ state. Tables 1–3, respectively. On the other hand, those for TTFC–G in layer O are close to Full crystallographic details, excluding structure factors, each other, making the oxidation state assignment for each have been deposited at the Cambridge Crystallographic Data TTF molecule diYcult.Thus, the charged state of each Centre (CCDC). See Information for Authors, J. Mater. Chem., layer is considered as [(TTFA) (TTFB) (FeCl4)4]2- and 1998, Issue 1. Any request to the CCDC for this material [(TTFC) (TTFE) (TTFF) (TTFG) (TTFD)2]+, respectively.The should quote the full literature citation and the reference average charge state of TTFC–G is +1/6. number 1145/59. The S,S distances in trimers (1) and (2) [linkages (iii) and (iv) in Fig. 2(b)] are 3.4–3.5 A ° , which correspond well to those Physical measurements observed in usual one-dimensional (1-D) columns of TTF salts.11,12 Moreover, the S,S distances between the trimers The resistivity of the samples was measured by the conventional four-probe method in the temperature range 80–300 K.Four are also short enough [3.63–3.93 A ° ; linkage (vi) and (vii) in Fig. 2(b)] to give rise to an interacting network, resulting in 15 mm diameter gold wires bonded to the crystal with carbon conducting paint were used as current and voltage terminals.two-dimensional sheets. Most charge transfer TTF salts synthesized so far have either 1-D columns11,12 or discrete dimer EPR spectra were recorded at X-band frequency with a JEOL RE-3X spectrometer operating at 9.1 GHz over the structures.12,13 The present compound has a new structure type of TTF trimer-based layers. On the other hand, the S,S temperature range 5–300 K.Resonance frequency was measured on an Anritsu MF76A microwave frequency counter. distance of 5.163 A ° [linkage (ii) in Fig. 2(a)] indicates the absence of interaction between TTFA and TTFB in layer I. Magnetic fields were calibrated by an Echo Electronics EFM- 2000AX NMR field meter. The EPR spectra were recorded The bond distances and angles of FeCl4- in Table 3 indicates 296 J.Mater. Chem., 1998, 8(2), 295–300Fig. 1 Thermal ellipsoid drawings (50% probability) and numbering schemes for the seven crystallographically independent TTF molecules and FeCl4-in TTF7(FeCl4)2 [*Symmetry: x, -y, z; **symmetry: -x, y, -z; ¾symmetry: -x, -y, -z] a distorted tetrahedral geometry. As shown in Table 4, the and one unpaired electron per TTF radical, indicative of the presence of antiferromagnetic interactions between TTF rad- deviation from tetrahedral is greater than those of the related charge transfer salts such as (BEDT-TTF)2FeCl4,4 icals and Fe ions.This is in contrast to the magnetic properties of (BEDT-TTF)2FeCl4,4 whose magnetic moment is attributed (l-BETS)2FeCl410 and (k-BETS)2FeCl4.10 The intriguing feature of this structure is the short S,Cl to inorganic FeCl4- anions.distances between the FeCl4- anion and the TTF molecules. The interlayer S,Cl distance is 3.38 A ° , which is shorter than Spectroscopic properties the sum of the van der Waals radius of S and Cl atoms The temperature dependence of the Raman bands is shown in (3.65 A ° ). The intralayer S,Cl distances [ linkage (i) in Fig. 5. Three Raman bands at ca. 1500 cm-1 (1515, 1483, Fig. 2(a)] are 3.649–4.198 A ° . On the other hand, an interesting 1421 cm-1 ), which are assigned to the central CNC stretching magnetic interaction between the FeCl4- anion and the BETS in the TTF molecule, were observed at 300 K. In the solid molecule was previously observed in (k-BETS)2FeCl4,10 the state, the n3 mode of the central CNC stretching occurs at S,Cl distance of which was 3.54 A ° , and one in (BEDT- 1512 cm-1 for TTF0 and is seen at 1416 cm-1 in TTF+.21 On TTF)2FeCl4 was 3.55 A ° .The S,Cl distance of TTF7(FeCl4)2, this basis, the Raman band at 1421 cm-1 is assigned to the 3.38 A ° , is even shorter than in these compounds. These short TTF molecules A and B with +1 state, while the Raman S,Cl distances are associated with a magnetic interaction bands at 1515 and 1483 cm-1 are assigned to the neutral TTF between the p-spin of TTF radical cations and d-spin of and partially oxidized TTFn+(0<n<1) for TTF molecules FeCl4- anions.C–G. On the other hand, a new band (1446 cm-1 ), which corresponds to the broad band (1200–1700 cm-1) at 300 K, Physical properties appeared at 72 K, suggesting the localization of charged states of TTF molecules by cooling.Four-probe dc transport measurements on TTF7(FeCl4)2 reveal semiconducting behavior from 80 to 300 K with a room The EPR spectrum of a polycrystalline sample in Fig. 6 consists of two types of signals [a sharp one (a) and a broad temperature conductivity sRT of 0.055 S cm-1 (Fig. 3). The activation energy varies smoothly from 0.15 eV at 300 K to one (b)] in the entire temperature range (5–300 K).However the temperature dependence of the g values and their linewidths 0.08 eV at 80 K, smaller at room temperature than, and comparable to, that of TTF7(MCl4)2 (M=Co, Mn, Zn, Cd) are completely diVerent indicating that the signals arise from diVerent radical cations or magnetic anions in the crystal. 15,19,20 and (BEDT-TTF)2FeCl4.4 The jump in the resistivity at ca. 280 K is probably due to cracking in the crystal. Signal (a) is much sharper than signal (b) and has no hyperfine structure. The mean g value, 2.007, which is attributed to a The magnetic susceptibility was measured over the temperatures range 2–300 K (Fig. 4). xmT decreases at lower tempera- TTF radical, is unchanged upon decreasing the temperature (Fig. 7). The lineshape is isotropic at 292 K whereas it shows ture and x follows the Curie–Weiss law with a Weiss constant of -2.3 K and Curie constant of 0.23 emu K mol-1. The anisotropy at lower temperatures: an axial-symmetry pattern is observed above 50 K, while a rhombic pattern is observed magnetic moment at 300 K (5.81 mB) is much smaller than that expected on the basis of five unpaired electrons per Fe atom below 50 K.These features suggest that signal (a) arises from J. Mater. Chem., 1998, 8(2), 295–300 297Fig. 2 (a) Projection of the FeCl4-/TTF layers (type I) along the a-axis. The dashed lines with the number indicate the short contact of S,Cl and S,S pairs. The distances are as follows: (i ) 3.649–4.198 A ° , (ii) 5.163 A ° .(b) Projection of the TTF trimer layers (type O) along the a-axis. The dashed lines with the number indicate short S,S contacts. The distances are as follows: (iii) 3.474 A ° , (iv) 3.476 A ° , (v) 3.714 A ° , (vi) 3.830–3.932 A ° , (vii) 3.633–3.680 A ° . (c) Projection of the TTF trimer layers (type O) and FeCl4-/TTF layers (type I) along the b-axis.Fig. 3 Temperature-dependent resistivity of a single crystal of (TTF)7(FeCl4)2 Fig. 4 xmT vs. T plot for (TTF)7(FeCl4)2 298 J. Mater. Chem., 1998, 8(2), 295–300Fig. 7 Temperature dependence of the g-values of the two EPR signals of (TTF)7(FeCl4)2. Black triangles and circles indicate the g-values of the type (a) and (b) signals, respectively, in Fig. 6. Fig. 5 Temperature dependence of Raman spectra of (TTF)7(FeCl4)2 TTF(CoCl4)x (x#0.25).20 The spin density of signal (b) is about ten times larger than that of signal (a) over the temperature range of 77–292 K.Consequently, signal (b) is associated with the two FeIII (S=5/2+5/2) and one TTF radical (S=1/2) in TTF7(FeCl4)2. Conclusions A TTF-based charge transfer salt, TTF7(FeCl4)2, has been synthesized from the binuclear unit [(FeIIICl4)2(m-C2O4)]4-, and is structurally characterized. The characteristic features are that TTF7(FeCl4)2 is composed of three spin species, FeCl4-, TTFA,B and a TTF trimer.TTFC–G molecules in type O layer have the charge state of 0 to +1. The d-spins in FeCl4 anions and p-spins of TTF cation radicals, which sit close to each other, coexist in layer I.The crystal structure also reveals the occurrence of interlayer interactions of FeCl4 anions and p-spins of TTF cation radicals. Finally, a temperature dependence of the g-values in the EPR signals is observed, characteristic of an interaction between the p-spin of TTF radicals and d-spin of FeCl4- anions. This work was supported by a Grant-in Aid for Scientific Research, the Ministry of Education, Science, Sports and Culture, Japan, and Nissan Foundation for the Promotion of Science.References 1 M. Metzger, P. Day and G. C. Papavassiliou, L ower-Dimensional Systems andMolecular Electronics, Plenum Press, New York, 1990. 2 P. Day, M. Kurmoo, T. Mallah, I. R. Marsden, R. H. Friend, F. L. Pratt, W. Hayes, D. Chasseau, J. Gaultier, G. Bravic and Fig. 6 Temperature dependence of EPR spectra of (TTF)7(FeCl4)2. L. Ducasse, J. Am. Chem. Soc., 1992, 114, 10 722. Type (a) and (b) indicate sharp and broad signals. 3 M. Kurmoo, A. W. Graham, P. Day, S. J. Coles, M. B. Hursthouse, J. L. Caulfield, J. Singleton, F. L. Pratt, W. Hayes, L. Ducasse and P. Guionneau, J. Am. Chem. Soc., 1995, 117, 12 209. TTF+ radicals displaying an exchange-coupled interaction.On 4 T. Mallah, C. Hollis, S. Bott, M. Kurmoo and P. Day, J. Chem. the other hand, an apparent temperature dependence is Soc., Dalton T rans., 1990, 859. observed for the signal (b). In TTF7(FeCl4)2 the g value shifts 5 T. Mori, Solid State Phys., 1991, 26, 1. from 2.15 at 292 K to 1.86 at 5 K and the peak-to-peak 6 C. J. Gomez-Garcia, L. Ouahab, C. Gimenez-Saiz, S.Triki, linewidth decreases with temperature (Fig. 7). The g value of E. Coronado and P. Delhaes, Angew. Chem., Int. Ed. Engl., 1994, signal (b) is larger than that for powdered [Et4N]FeCl4 (g= 33, 223. 7 C. J. Kepert, M. Kurmoo and P. Day, Inorg. Chem., 1997, 36, 1128. 2.025) at high temperatures and smaller than that for the free 8 C. J. Kepert, M. Kurmoo, M. R. Truter and P.Day, J. Chem. Soc., electron (g=2.0023) at low temperatures, associated with the Dalton T rans., 1997, 607. deviation from tetrahedral geometry of FeCl4-, thus implying 9 C. J. Kepert, M. Kurmoo and P. Day, J.Mater. Chem., 1997, 7, 221. an interaction between spins on FeIII ions and TTF radicals. 10 H. Kobayashi, H. Tomita, T. Naito, A. Kobayashi, F. Sakai, This unusual behavior in the EPR parameters was not T.Watanabe and P.Cassoux, J. Am. Chem. Soc., 1996, 118, 371. observed for (BEDT-TTF)2FeCl4,4 (BETS)2FeCl4,10 11 L. Ouahab, M. Bencharif, A. Mhanni, D. Pelloquin, J.-F. Halet, O. Pena, J. Padiou and D. Grandiean, Chem. Mater., 1992, 4, 666. TTF(MnCl3)x (x#0.75), TTF(MnCl4)x (x#0.25), or J. Mater. Chem., 1998, 8(2), 295–300 29912 B. A. Scott, S. J. L. Placa, J. B. Torrance, B. D. Silverman and 18 M. Bousseau, L. Valade, J.-P. Legros, P. Cassoux, M. Garbauskas B. Welber, J. Am. Chem. Soc., 1977, 28, 6631. and L. V. Interrante, J. Am. Chem. Soc., 1986, 108, 1908. 13 R. C. Teitelbaum, T. J. Marks and C. K. Johnson, J. Am. Chem. 19 C. Garrigou-Lagrange, S. A. Rozanski, M. Kumoo and F. L. Pratt, Soc., 1980, 23, 2986. Solid State Commun., 1988, 67, 481. 14 G. Matsubayashi, K. Ueyama and T. Tanaka, J. Chem. Soc., 20 M. Lequan, R. M. Lequan, C. Hauw, J. Gaultier, G. Maceno and Dalton T rans., 1985, 465. P. Delhaes, Synth.Met., 1987, 19, 409. 15 G. Maceno, Ch. Garrigou-Lagrange, M. Lequan, R. M. Lequan, 21 A. R. Siedle, T. F. Candela, A. G. Finnegan, R. P. V. Duyne, J. Gaultier, F. Bechtel, G. Bravic and P. Delhaes, Synth.Met., 1988, T. Cape and G. F. Kokoszka, Inorg. Chem., 1981, 20, 2635. 27, B57. 16 K. Kondo, G. Matsubayashi, T. Tanaka, H. Yoshioka and K. Nakatsu, J. Chem. Soc., Dalton T rans., 1984, 379. 17 M. Feist, S. Troyanov and E. Kemnitz, Inorg. Chem., 1996, 35, 3067. Paper 7/03770H; Received 30th May, 1997 300 J. Mater. Chem., 1998, 8(2), 295–300

ISSN:0959-9428    

DOI:10.1039/a703770h

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

J O U R N A L O F C H E M I S T R Y Materials Preparation and characterization of metal complexes with an extended TTF dithiolato ligand, bis(propylenedithiotetrathiafulvalenedithiolato)-nickelate and -cuprate† Mieko Kumasaki, Hisashi Tanaka and Akiko Kobayashi* Department of Chemistry, Faculty of Science, T he University of T okyo, Hongo, Bunkyo-ku, T okyo 113, Japan Novel monoanionic nickel and dianionic copper complexes with the extended TTF dithiolato ligand, propylenedithiotetrathiafulvalenedithiolate [ptdt2-=(S8C9H6)2-], have been synthesized. Characterization of monoanionic tetraphenylphosphonium and tetramethylammonium salts of Ni(ptdt)2- and the dianionic tetraphenylphosphonium salt of Cu(ptdt)22- have been performed, using cyclic voltammetry, electrical resistivity measurements, magnetic susceptibility measurements and X-ray crystal structure determination.The geometries around the Ni atoms are almost square planar. In both Ni complexes, one of the extended ligands of Ni(ptdt)2- is overlapping with that of the adjacent anion separated by about half of the unit of the molecule, forming a one-dimensional chain. The adjacent chains are connected by transverse short S,S contacts.Cu(ptdt)22- has a distorted tetrahedral geometry around the Cu atom and the dihedral angle between the planes of the dithiolato ligand is 54.2 °. The crystal structures of Ni(ptdt)2- and Cu(ptdt)22- complexes show the possibility of novel 2D or 3D intermolecular contacts through ptdt ligands. The complex [Me4N][Ni(ptdt)2]·Me2CO is a semiconductor with a room temperature conductivity of 1.4×10-3 S cm-1 and activation energy of 9.9×10-2 eV.In recent investigations of molecular conductors and supercon- metal complexes with elongated p-ligands will provide new types of molecular conducting systems. Here, we report the ductors, there is increasing interest in molecules with extended p-conjugation frameworks.1 This is because such molecules preparation of a new ligand, propylenedithiotetrathiafulvalenedithiolate (C9H6S82-, ptdt2-) and the crystal structures of a can stabilize multi-cation states and increase intermolecular interactions.Furthermore metal complexes with extended p precursor of the ligand ptdt(CH2CH2CN)2, the tetraphenylphosphonium salt of a square-planar Ni complex, (Ph4P)- ligands are expected to open a new field of molecular conductors owing to the variety of central metal atoms and possible [Ni(ptdt)2]·1.4Me2CO 1, the tetramethylammonium salt of the Ni complex, (Me4N)[Ni (ptdt)2]Me2CO 2 and a tetrahedral modifications of the extended p-conjugation ligands.However, only a few conducting metal complexes with elongated dithi- Cu complex, (Ph4P)2[Cu(ptdt)2]·1.2Me2CO 3.olene-type ligands have been prepared. Recently, Narvor et al. have reported the synthesis, structure Experimental and conductive properties of nickel complexes of tetrathiafulva- Synthesis and crystal growth lenedithiolate, which exhibited a fairly high conductivity in the neutral state.2 However bulky terminal SR (R=alkyl) groups Reagent-grade tetrahydrofuran was purified and distilled over sticking out from the molecular plane might prevent close sodium–benzophenone prior to use. Methanol was refluxed intermolecular S,S contacts.Nakano et al. have prepared over Mg and distilled; other solvents and chemicals were used metal complexes of ethylenedithiotetrathiafulvalenedithiolate as received. Schlenk techniques were used in carrying out (C8H4S82-, etdt2-).3 The etdt metal complexes, however, have manipulations under argon atmosphere.NMR spectra were poor solubility as is often the case for molecules with extended measured on a JEOL JNM-EX 270 Model spectrometer. p-conjugation, which is unfavorable for obtaining good single Cyclic voltammetry data were recorded by BAS CV-60W. The crystals. Thus a crystal structure of an M(etdt)2 compound ptdt2- ligand was synthesized as shown in Scheme 1.has not been reported. Therefore, an improvement of the Initially, we used p-acetoxybenzyl as the protecting group solubility seems to be necessary for further development. in cross-coupling to synthesize the unsymmetrical precursor of In order to increase solubility, we prepared a new ligand ptdt2-.Gemmell et al.4 and Misaki et al.5 reported that their which incorporates an additional methylene group into etdt2-. unsymmetrical TTF derivatives were obtained in high yields One of the important requirements for constituent molecules using this protecting group. In our case, however, the crossof the molecular conductors is good planarity of the molecules. coupling method gave more than five products and our target However in metal complexes with tetrathiafulvalenedithiolate, molecule was obtained in only 4.6% yield.We then used the planarity of the whole molecule may be not so important. cyanoethyl as the protecting group, and succeeded in obtaining The long ligand will be preferably favorable for increasing 7 in high yield. overlapping between the molecules. Each of the two tetrathiafulvalene moieties joined to the central transition metal atom Preparation of 4,5-propylenedithio-1,3-dithiole-2-thione 4.will be able to produce S,S networks even if the metal (Et4N)2[Zn(dmit)2] (43 g) was dissolved in 200ml of acetocomplex molecule has a twisted conformation. Thus transition nitrile and 26 g of 1,3-dibromopropane was added and the solution stirred for 2 d at room temperature.The resulting orange precipitate was filtered oV and to the residue dichloro- † Presented at the 58th Okazaki Conference, Recent Development and methane was added and the solution was filtered. Activated Future Prospects of Molecular Based Conductors, Okazaki, Japan, 7–9 March 1997. charcoal (0.2 g) was added to the filtrate and the solution was J. Mater.Chem., 1998, 8(2), 301–307 301S S S S S S Zn S S S S [Et4N]2[Zn(dmit)2] S S S S S 4 Br Br CH3CN [(C2H5)4N]2 [Et4N]2[Zn(dmit)2] NC Br CH3CN S S S S CN CN S 5 S S S S CN CN O 6 Hg(OAc)2–CHCl3 AcOH S S S S CN CN 7 S S S S 4 + 6 P(OEt)3 S S S–NMe4 + S–NMe4 + S S S S NMe4OH MeOH S S S S S S S S S S S S S S S S M S S S S S S S S S S S S S S S S M M2+ (NMe4) x 8 M = Ni 9 M = Cu 1 M = Ni 3 M = Cu cation exchange (PPh4)m(solvent) n Scheme 1 refluxed for 30 min. The solution was filtered and ethanol was to -20 °C.Orange yellow needle crystals were obtained. Yield 3.1 g. (60.5% based on 6) (Found: C, 37.48; H, 2.95; N, 5.84; S, added. Yellow crystals were obtained from this solution at -20 °C. Yield 19.6g. {68.7% based on (Et4N)2[Zn(dmit)2]}. 53.30. C15H14N2S8 requires C, 37.63; H, 2.95; N, 5.85; S, 53.58%). 1H NMR(270 MHz, CDCl3, ref.TMS) dH: 3.08 (4H, t, J= 7.1Hz), 2.76–2.69 (8H, m), 2.41 (2H, m). Preparation of 4,5-bis(2-cyanoethylthio)-1,3-dithiole-2-thione 5. (Et4N)2[Zn(dmit)2] (10 g) was dissolved in 80 ml of acetonitrile and 7 g of 3-bromopropionitrile was added to the Preparation of 8. The following procedures were performed under an argon atmosphere. To 101 mg of 7 in a 300 ml flask solution and was refluxed for 1 h. The solution was filtered oV and then concentrated.After adding 125 ml of dichloro- was added 22 ml of THF and the solution was cooled to -78 °C using a dry-ice bath. The tetramethylammonium salts methane, the solution was washed three times with water. Then the solution was dried with magnesium sulfate.After were obtained by deprotection with 0.2 ml of Me4NOH followed by addition of 20 ml of a methanol solution containing removing the drying agent, ethanol was added at -20 °C. Brown yellow needle crystals were obtained. Yield 5.6 g. 5 mg of NiCl2·6H2O. This solution was stirred overnight and then gradually warmed to room temperature. The obtained {66.1% based on (Et4N)2[Zn(dmit)2]}.precipitate was filtered oV and dried in vacuo (1 mmHg) and obtained as a brown powder. 4,5-Bis(2-cyanoethylthio)-1,3-dithiole-2-one 6. To 4.8 g of 5 and 12.1 g of Hg(CH3COO)2 in a 300 ml flask were added 160 ml of chroloform–acetic acid (351). The solution was Preparation of 9. The following procedures were performed under an argon atmosphere.To 101 mg of 7 in a 300 ml flask stirred at room temperature overnight. A white precipitate was obtained and filtered oV using Celite. The filtered solution was was added 22 ml of THF. The solution was then cooled to -78 °C using a dry-ice bath. The tetramethylammonium salts washed with water, saturated NaHCO3 aqueous solution, water and dried with Na2SO4. After removing the drying was prepared by deprotection with 0.2 ml of Me4NOH followed by addition of a 20 ml methanol solution of 5 mg of agent, the filtrate was concentrated and ethanol was added at -20 °C.Milky white crystals were obtained. Yield 3.7 g. CuCl2·2H2O at -78 °C. This solution was stirred overnight and the reaction mixture was warmed gradually to room (83.7% based on 5). temperature. The obtained green precipitate was filtered oV and dried at 1 mmHg pressure. 2,3-Bis (2-cyanoethylthio)-6,7-propylenedithiotetrathiafulvalene 7.To 4.4 g of 4 and 3.0 g of 6 in a 200 ml flask under an argon atmosphere was added freshly distilled P(OC2H5)3 Preparation of 1 and 2. Compound 8 and tetraphenylphosphonium bromide were placed in separate compartments of (130 ml) under flushing argon.The reaction mixture was then raised to 110 °C. After reaction for 1 h, the red solution was an H-cell under argon. Acetone was poured into the H-cell which was left to stand undisturbed. After 10 days, red plate cooled to room temperature and a precipitate was obtained at -20 °C. The precipitate was dissolved into dichloromethane and crystals of 1 were obtained. Crystals of 2 were obtained unexpectedly in the procedure of the electrocrystallization 7 was isolated by dichloromethane silica gel column chromatography.The solution was concentrated, ethanol added and cooled using a current of 0.1 mA in an H-shaped cell with platinum 302 J. Mater. Chem., 1998, 8(2), 301–307electrodes under an argon atmosphere. The crystals were the non-hydrogen atoms and refinement was by full-matrix least-squares methods.The calculated positions of hydrogen obtained using 10 mg of 8 and tetramethylammonium bromide and then adding 20 ml of acetone. Black block crystals were atoms [d(C–H)=0.95 A ° ] were included in the final calculation except for the solvent molecules. The populations of the solvent collected from the bottom of the H-cell after 3 weeks. molecules are refined initially and fixed in the final calculation.Atomic scattering factors were taken from ref. 6. The absolute Preparation of 3. Compound 9 and tetraphenylphosphonium bromide were placed in separate compartments of an H-cell configuration of the crystal structure of 7 could not be determined owing to an insuYcient number of Friedel pair reflec- under argon.Acetone was poured into the H-cell which was left to stand undisturbed. After 10 days green plate crystals tions. All calculations were performed using the teXsan crystallographic software package of the Molecular Structure were obtained. Corporation.7 Full crystallographic details excluding structure factors have been deposited at the Cambridge Crystallographic Cyclic voltammetry Data Centre (CCDC).See Information for Authors, J. Mater. Cyclic voltammetry (CV) of (Me4N)2[Cu(ptdt)2] 9 and Chem., 1998, Issue I. Any request to the CCDC for this material (Me4N)[Ni (ptdt)2] 8 were carried out in acetonitrile using should quote the full literature citation and the reference (Bu4N)ClO4 as supporting electrolyte at 100 mV s-1 over the number 1145/54.potential range -1.8 to +2.0 V. The working and counter electrode were platinum and the reference electrode was Magnetic susceptibility Ag/Ag+. (Me4N)2[Cu(ptdt)2] and (Me4N)[Ni(ptdt)2] showed qualitatively similar features, but the latter’s peak intensities The magnetic susceptibility was measured at a field of 2 T decreased on repeated scanning due to the formation of an from 300 to 2 K using a Quantum Design MPMS SQUID insoluble film of the neutral 151 salt on the electrode.magnetometer. (Me4N)2[Cu(ptdt)2] showed one reduction process at-0.73 V vs. SCE and two oxidation process at -0.08 and +1.15 V vs. Electrical resistivity SCE, while (Me4N)[Ni (ptdt)2] showed peaks at-0.45,-0.15, Resistivities were measured by a conventional four-probe and +1.20 V.The CV data of these compounds indicate that method using gold wire (0.02 mm) with gold paint as a contact the peak at -0.08 V of the Cu complex appears to correspond in the temperature range 300–77 K. to the process Cu(ptdt)22-�Cu(ptdt)2- and the peak at -0.45 V of the Ni complex corresponds to the process Ni(ptdt)22-�Ni(ptdt)2-; Ni (ptdt)22- is readily oxidized to Results and Discussion Ni(ptdt)2-.Crystal structures Crystal structure determination 2,3-Bis (2-cyanoethylthio)-6,7-propylenedithiotetrathiafulvalene5ptdt( CH2CH2CN)2 7. The ptdt(CH2CH2CN)2 molecule is Intensity data were measured on Rigaku AFC-7R, AFC-5R or AFC-6S automated four-circle diVractometers using graphite shown in Fig. 1(a) and selected bond lengths are listed in Table 2. Atoms S(1), S(2), S(3), S(4), C(1) and C(2) lie in a good plane monochromated Mo-Ka radiation at 23 °C.Empirical absorption corrections were performed. The experimental details and A while atoms S(3), S(4), S(5), S(6), S(7), S(8), C(3), C(4), C(5) and C(6) including a tetrathiafulvalene group form a fairly crystal data are listed in Table 1. The structure were solved by direct methods.Anisotropic temperature factors were used for good plane B. Atoms S(7), S(8), C(5), C(6), C(7), C(8) and Table 1 Crystal and experimental data (Me4N)[Ni(ptdt)2]·Me2CO (Ph4P)[Ni(ptdt)2]·1.4Me2CO (Ph4P)2[Cu(ptdt)2]·1.2Me2CO ptdt(CH2CH2CN)2 formula C25H30S16NNiO C47.40H44.60S16PNiO1.40 C69.60H59.20S16CuP2O1.20 C15H14N2S8 crystal color, habit black, block red, plate green, block orange, needle crystal system triclinic monoclinic monoclinic monoclinic formula mass 932.18 1190.53 1553.29 478.77 a/A ° 12.799(1) 28.567(3) 21.420(6) 9.96(3) b/A° 13.306(1) 8.289(6) 11.826(4) 6.707(9) c/A ° 12.539(2) 25.295(6) 29.18(1) 15.08(5) a/degrees 91.172(9) b/degrees 108.421(7) 108.08(1) 91.20(3) 101.0(2) c/degrees 109.482(6) V/A ° 3 1890.9(4) 5694(3) 7390(3) 988(3) space group P19 C2/c P2/c P21 Z 2 4 4 2 Dx/g cm-3 1.637 1.389 1.396 1.608 dimensions/mm 0.30×0.20×0.20 0.30×0.20×0.20 0.20×0.30×0.10 0.30×0.10×0.60 radiation Mo-Ka Mo-Ka Mo-Ka Mo-Ka diVractometer AFC 5R AFC 7R AFC 5R AFC 6S m/cm-1 14.21 9.93 8.34 9.05 2hmax/degrees 55.0 55.0 55.0 55.3 total reflections 9230 7155 18 277 2619 reflections used 8693 7007 17 814 2483 parameters refined 397 288 790 226 scan technique v–2h v v v–2h scan width 1.57+0.30tanh 0.73+0.30tanh 0.73+0.30tanh 1.10+0.30tanh v scan speed 12 16 16 8.0 (degrees min-1) R, Rw 0.039, 0.034 0.060, 0.058 0.065, 0.055 0.035, 0.036 final shift/error 0.67 0.59 0.06 0.06 residual d/e A° -3 0.34 0.77 0.38 0.24 J.Mater. Chem., 1998, 8(2), 301–307 303Fig. 2 (a) ORTEP drawing of the monoanion Ni(ptdt)2- showing the atom labelling at the 50% probability level.(b) Side view of Ni(ptdt)2- in (Ph4P)[Ni(ptdt)2]·1.4Me2CO. Table 3 Selected bond lengths (A ° ) and angles (degrees) for (Ph4P)[Ni(ptdt)2]·1.4Me2CO Ni(1)MS(1) 2.154(1) S(6)MC(6) 1.752(7) Ni(1)MS(2) 2.167(2) S(7)MC(5) 1.736(7) S(1)MC(1) 1.735(7) S(7)MC(7) 1.809(8) S(2)MC(2) 1.707(6) S(8)MC(6) 1.739(8) S(3)MC(1) 1.765(6) S(8)MC(9) 1.783(8) S(3)MC(3) 1.757(7) C(1)MC(2) 1.345(9) S(4)MC(2) 1.762(7) C(3)MC(4) 1.323(8) S(4)MC(3) 1.773(7) C(5)MC(6) 1.36(1) S(5)MC(4) 1.755(7) C(7)MC(8) 1.49(1) S(5)MC(5) 1.757(7) C(8)MC(9) 1.54(1) S(6)MC(4) 1.765(7) Fig. 1 (a) ORTEP drawing8 of ptdt(CH2CH2CN)2 showing the atom labelling at the 50% probability level. (b) Side view of S(1)MNi(1)MS(1) 180.00 S(1)MNi(1)MS(2) 87.07(7) ptdt(CH2CH2CN)2.S(1)MNi(1)MS(2) 92.93(7) S(1)MNi(1)MS(2) 92.93(7) S(1)MNi(1)MS(2) 87.07(7) S(2)MNi(1)MS(2) 180.00 Table 2 Selected bond lengths (A° ) for ptdt(CH2CH2CN)2 S(1)MC(1) 1.752(6) S(7)MC(5) 1.738(6) and angles of Ni(ptdt)2- are similar to those of the analogous S(2)MC(2) 1.761(6) S(7)MC(7) 1.821(8) compound in which propylene groups are substituted for the S(3)MC(1) 1.751(6) S(8)MC(6) 1.75 two methyl groups [2.172(5), 2.160(7) A ° and 93.3(2), 86.7(2) °, S(3)MC(3) 1.744(6) S(8)MC(9) 1.847(9) respectively].2 The central C(3)MC(4) bond length is S(4)MC(2) 1.753(6) C(1)MC(2) 1.328(8) 1.323(8) A ° , which is shorter than that in 7.The seven-mem- S(4)MC(3) 1.771(6) C(3)MC(4) 1.342(7) bered heteroring is flexible and those in ptdt(CH2CH2CN)2 1 S(5)MC(4) 1.743(6) C(5)MC(6) 1.310(8) S(5)MC(5) 1.752(6) C(7)MC(8) 1.46(1) and Ni(ptdt)2- 2 bend at S(7) and S(8) in the opposite S(6)MC(4) 1.752(6) C(8)MC(9) 1.50(1) direction.The crystal structure of 1 [Fig. 3(a)] showed that S(6)MC(6) 1.766(6) one of the ligands of Ni(ptdt)2- is overlapping with that of the adjacent anion separated by the translation 1/2a-1/2b, forming a one-dimensional chain along [110].The overlapping C(9) form a seven-membered heteroring. This seven-membered mode of Ni(ptdt)2- is shown in Fig. 3(b), which shows that ring adopts a chair conformation and is tilted from plane B. The central C(3)MC(4) bond length is 1.342(7) A ° , which is similar to that of the CNC bond length in neutral bis(propylenedithio)- tetrathiafulvalene [1.341(4) A ° ].9 The C(1)MC(2) and C(5)M C(6) distances are 1.328(8) and 1.310(8) A ° , respectively, which are shorter than the central C(3)MC(4). Fig. 1(b) shows that C(7), C(8) and C(9) show the largest deviation from plane A, of 4.06, 4.27 and 3.91 A ° , respectively. The dihedral angle of planes A and B is 21.25 °. (Ph4P)[Ni(ptdt)2]·1.4Me2CO 1. The Ni(ptdt)2- anion is shown in Fig. 2(a) and selected bond lengths and angles are shown in Table 3.The Ni(ptdt)2- anion is located on an inversion center. Atoms Ni(1), C(1), C(2), S(1), S(2), S(3) and S(4) lie on a common plane A while the terminal propylenic group is bent. The mean deviation of the atoms from the least-squares plane is ca. 0.03 A° . Atoms S(7) and S(8) show the largest deviation from the plane at 2.062 and 1.998 A ° .The planarity of the molecule is better than the neutral ptdt(CH2CH2CN)2 molecule [Fig. 2(b)]. Atoms S(5), S(6), S(7), S(8), C(5) and C(6) form a plane B with the dihedral angle between planes A and B being 30.13 °. The square-planar Ni complex shows NiMS distances of 2.154(2) and 2.167(2) A ° Fig. 3(a) Crystal structure of (Ph4P)[Ni(ptdt)2]·1.4Me2CO. (b) Overlapping mode of Ni(ptdt)2- in (Ph4P)[Ni(ptdt)2]·1.4Me2CO.and SMNiMS angles of 92.93(7) and 87.07(7) °. The distances 304 J. Mater. Chem., 1998, 8(2), 301–307Table 4 Selected bond lengths (A° ) and angles (degrees) the Ni(ptdt)2- anion is deviated along the short axis of the for (Me4N)[Ni(ptdt)2]·Me2CO molecule. The interplanar distance is ca. 3.25 A ° on average. The shortest Ni,Ni distance is 14.87 A ° while the shortest Ni(1)MS(1) 2.163(1) S(11)MC(12) 1.763(4) intermolecular S,S contact is 3.320(3) A° [S(1),S(7)], corre- Ni(1)MS(2) 2.172(1) S(12)MC(11) 1.748(4) sponding to the transverse S,S short contact with the neigh- Ni(1)MS(9) 2.174(1) S(12)MC(12) 1.767(4) Ni(1)MS(10) 2.164(1) S(13)MC(13) 1.758(4) bouring chain.Along the c-axis, however, no interaction is S(1)MC(1) 1.712(4) S(13)MC(14) 1.756(4) expected because the large tetraphenylphosphonium cations S(2)MC(2) 1.717(4) S(14)MC(13) 1.745(4) prevent the overlap of anions in this direction.The acetone of S(3)MC(1) 1.763(4) S(14)MC(15) 1.748(4) crystallization shows slight evidence of disorder with one of S(3)MC(3) 1.761(4) S(15)MC(14) 1.753(4) the CMC bond lengths being a little shorter than the other S(4)MC(2) 1.767(4) S(15)MC(16) 1.815(5) [CMC=1.28(2), CNO 1.17(1), CMC 1.57(2) A ° ] and the S(4)MC(3) 1.755(4) S(16)MC(15) 1.747(4) S(5)MC(4) 1.760(4) S(16)MC(18) 1.808(5) angles deviate from 120 ° [134 (1), 112 (1), 104 (1)°]. The S(5)MC(5) 1.765(4) C(1)MC(2) 1.358(5) population of the acetone molecule was determined by least- S(6)MC(4) 1.753(4) C(3)MC(4) 1.352(5) squares refinement as 0.7.The stereoview of anion arrangement S(6)MC(6) 1.765(4) C(5)MC(6) 1.341(5) of (Ph4P)[Ni(ptdt)2]·1.4Me2CO is shown in Fig. 4. S(7)MC(5) 1.739(4) C(7)MC(8) 1.511(6) S(7)MC(7) 1.816(5) C(8)MC(9) 1.519(6) (Me4N)[Ni(ptdt)2]·Me2CO 2. The Ni(ptdt)2- anion is S(8)MC(6) 1.740(4) C(10)MC(11) 1.361(5) S(8)MC(9) 1.806(4) C(12)MC(13) 1.332(5) shown in Fig. 5 and selected bond lengths and angles are listed S(9)MC(10) 1.715(4) C(14)MC(15) 1.343(5) in Table 4.Atoms Ni(1), C(1), C(2), S(1), S(2), S(3), S(4), S(10)MC(11) 1.711(4) C(16)MC(17) 1.515(6) C(10), C(11), S(9), S(10), S(11) and S(12) are in a common S(11)MC(10) 1.759(4) C(17)MC(18) 1.519(7) plane and the terminal propylenic group is bent. The mean S(1)MNi(1)MS(2) 93.11(4) S(2)MNi(1)MS(9) 88.72(4) deviation of atoms from the least-squares plane is ca. 0.07 A ° . S(1)MNi(1)MS(9) 175.84(6) S(2)MNi(1)MS(10) 176.43(6) Atoms S(7), S(8) S(15) and S(16) show the largest deviation S(1)MNi(1)MS(10) 85.52(4) S(9)MNi(1)MS(10) 92.86(4) from the plane at 1.309, 1.390, 1.202 and 1.512 A ° , respectively. Thus the planarity of the molecule is fairly high. The almost square-planar Ni complex shows NiMS distance of 2.163(1), crystal structure of 2 is shown in Fig. 6(a). Fig. 6(b) shows that 2.172(1), 2.174(1) and 2.164(1) A° while the SMNiMS angles one of the ligands of Ni(ptdt)2- is overlapping with that of an within the five-membered ring are 93.11(4) and 92.86(4) ° the adjacent anion separated by about half of the unit of the remainder are 85.52(4) and 88.72(4) °, respectively.The molecule, forming a one-dimensional chain along [101]. The dihedral angle between the planes S(1)NiS(2) and S(3)NiS(4) overlapping mode of Ni(ptdt)2- is ring-over-bond type and is 4.86 °. The central CNC bond lengths, C(3)MC(4) and the interplanar distance is 3.30 A ° . The overlap in the anion C(12)MC(13) are 1.352(5) and 1.332(5) A ° , respectively. The chain of 2 is larger than that in 1.The shortest intermolecular S,S distance is 3.525(2) A ° [S(7),S(15)], shown in Fig. 6(a) as dotted lines. Along the [011] direction, the shortest transverse S,S and Ni,Ni distances are 3.559(2) A ° [S(8),S(13)] and 6.562(1) A° , respectively. The characteristic feature of stacking is short S,S contacts between the neighbouring chains along the [201] direction, which was not observed for 1 owing to the large tetraphenylphosphonium cation.The interaction is expected because the small tetramethylammonium cation does not prevent contacts of the anions in this direction. The acetone of crystallization is not disordered. Fig. 4 Stereoview of the crystal structure of (Ph4P)- [Ni(ptdt)2]·1.4Me2CO. Fig. 6 (a) Crystal structure of (Me4N)[Ni(ptdt)2]·Me2CO.(b) Fig. 5 ORTEP drawing of the monoanion Ni(ptdt)2- showing the atom labelling at the 50% probability level Overlapping mode of Ni(ptdt)2- in (Me4N)[Ni(ptdt)2]·Me2CO. J. Mater. Chem., 1998, 8(2), 301–307 305(Ph4P)2[Cu(ptdt)2]·1.2Me2CO 3. The Cu(ptdt)22- anion is shown in Fig. 7 and selected bond lengths and angles are listed in Table 5. The terminal propylenic group of Cu(ptdt)22- is bent as found for the Ni complex.A distorted tetrahedral geometry is observed around the Cu atom with CuMS distances of 2.279(4), 2.273(4), 2.282(4) and 2.265(4) A ° and SMCuMS angles of 93.6(1), 93.2(1), 140.3(2) and 142.0(2) °. The dihedral angle between the planes S(1)CuS(2) and S(9)CuS(10) is 54.2 °. The central CNC bond lengths C(3)MC(4) and C(12)MC(13) are 1.35(1) and 1.35(2) A ° , respectively.The geometry around the Cu atom is almost the same as in [epy]2[Cu(dmit)2] (epy=N-ethylpyridinium; dmit=4,5-dimercapto-1,3-dithiole- 2-thione).10 In this case the dihedral angle is 57.3 °. The crystal structure is shown in Fig. 8 and the schematic stacking pattern of 3 is shown in Fig. 9. The anions form a one-dimensional chain along the c-direction with both ligands, which overlap in ring-over-bond type with those of adjacent anions.The interplanar distance is ca. 3.39A ° and the Cu,Cu distance is 14.78 A ° . The shortest intermolecular S,S distance is 3.582(7) A ° [S(16),S(16)], which correspond to short transverse contacts between adjacent chains. The large tetraphenylphosphonium cations prevent overlapping along the b direction.The pconjugated systems of the ptdt ligand are large enough to form conduction pathways in the crystal. In the case of [epy]2[Cu(dmit)2], owing to the small size of the ligand, the stacking of Cu(dmit)2 is only via one side of the ligand, which prevents formation of a good conduction pathway. The next step for the development of new types of molecular conductors may be oxidation of the complexes.Magnetic susceptibilities The temperature dependence of the magnetic susceptibility of (Me4N)2[Cu(ptdt)2] within the temperature range 2–300 K Fig. 8 (a) Crystal structure of (Ph4P)2[Cu(ptdt)2]·1.2Me2CO. (b) Stereoview of (Ph4P)2[Cu(ptdt)2]·1.2Me2CO. Fig. 7 ORTEP drawing of the dianion Cu(ptdt)22- showing the atom labelling at the 50% probability level Table 5 Selected bond lengths (A° ) and angles (degrees) for (Ph4P)2[Cu(ptdt)2]·1.2Me2CO Cu(1)MS(1) 2.279(4) S(11)MC(12) 1.74(1) Cu(1)MS(2) 2.273(4) S(12)MC(11) 1.78(1) Cu(1)MS(9) 2.282(4) S(12)MC(12) 1.74(1) Cu(1)MS(10) 2.265(4) S(13)MC(13) 1.77(1) S(1)MC(1) 1.73(1) S(13)MC(14) 1.79(1) Fig. 9 Schematic molecular arrangement and overlapping mode of S(2)MC(2) 1.74(1) S(14)MC(13) 1.76(1) (Ph4P)2[Cu(ptdt)2]·1.2Me2CO S(3)MC(1) 1.77(1) S(14)MC(15) 1.74(1) S(3)MC(3) 1.76(1) S(15)MC(14) 1.75(1) S(4)MC(2) 1.75(1) S(15)MC(16) 1.81(1) S(4)MC(3) 1.75(1) S(16)MC(15) 1.72(1) obeys Curie behavior, indicating non-interacting spins for S(5)MC(4) 1.73(1) S(16)MC(18) 1.78(1) (Me4N)2[Cu(ptdt)2].The diamagnetic component of the mag- S(5)MC(5) 1.75(1) C(1)MC(2) 1.34(2) netic susceptibility was estimated by use of Pascal law to be S(6)MC(4) 1.76(1) C(3)MC(4) 1.35(1) S(6)MC(6) 1.76(1) C(5)MC(6) 1.35(2) -4.9×10-4 emu mol-1.11 The room temperature magnetic S(7)MC(5) 1.76(1) C(7)MC(8) 1.50(2) susceptibility of 9.8×10-4 emu mol-1 suggests 0.8 spins per S(7)MC(7) 1.81(2) C(8)MC(9) 1.48(2) molecule, which is consistent with the presence of Cu2+.S(8)MC(6) 1.72(1) C(10)MC(11) 1.34(2) S(8)MC(9) 1.84(1) C(12)MC(13) 1.35(2) Electrical resistivities S(9)MC(10) 1.74(1) C(14)MC(15) 1.35(2) S(10)MC(11) 1.72(1) C(17)MC(18) 1.53(2) The temperature dependence of the resistivity of S(11)MC(10) 1.76(1) C(16)MC(17) 1.51(2) (Me4N)[Ni (ptdt)2]·Me2CO was measured by usual four-probe S(1)MCu(1)MS(2) 93.6(1) S(2)MCu(1)MS(9) 142.0(2) method and was semiconducting (Fig. 10). The room tempera- S(1)MCu(1)MS(9) 101.6(1) S(2)MCu(1)MS(10) 96.9(1) ture conductivity is 1.4×10-3 S cm-1 and the activation S(1)MCu(1)MS(10) 140.3(2) S(9)MCu(1)MS(10) 93.2(1) energy is 9.9×10-2 eV. 306 J. Mater. Chem., 1998, 8(2), 301–307A. Sato for her help in magnetic susceptibility measurements. This work was partly supported by Grant-in Aid for Fundamental Research on ‘New Series of BETS Superconductors with Mixed Halide Gallium Anions’.References 1 Y. Misaki, H. Nishikawa, K. Kawakami, S. Koyanagi, T. Yamabe and M. Shiro, Chem. L ett., 1992, 2321. 2 N. L. Narvor, N. Robertson, T. Weyland, J. D. Kilburn, A. E. Underhill, M. Webster, N. Svenstrup and J. Becker, Chem. Commun., 1996, 1363; N. L. Narvor, N. Robertson, E. Wallace, J.D. Kilburn, A. E. Underhill, P. N. Bartlett and M. Webster, J. Chem. Soc., Dalton. T rans., 1996, 823. 3 M. Nakano, A. Kuroda, T. Maikawa and G. Matsubayashi, Mol. Cryst. L iq. Cryst., 1996, 284, 301. 4 C. Gemmell, G. C. Janairo, J. D. Kilburn, H. Ueck and A. E. Underhill, J. Chem. Soc., Perkin T rans., 1995, 2715. Fig. 10 Temperature dependence of the electrical resistivity of 5 Y.Misaki, H. Nishikawa, K. Kawakami, S. Koyanagi, T. Yamabe (Me4N)[Ni(ptdt)2]·Me2CO and M. Shiro, Chem. L ett., 1992, 2321. 6 International Tables for X-Ray Crystallography, Kynoch Press, Birmingham 1974, vol. IV. 7 TeXsan: Crystal Structure Analysis Package, Molecular Structure Corporation, version 1. 7–2a, 1995. Conclusion 8 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge National Laboratory; Oak Ridge, TN, 1976. Two inevitable requirements for the design of the good conduc- 9 L.C. Porter, A. M. Kini and J. M. Williams, Acta Crystallogr., tors are: (1) the formation of conduction pathway and (2) the Sect. C, 1987, 43, 998. formation of charge carriers. As for requirement (1), the crystal 10 G. Matsubayashi, K. Takahashi and T. Takano, J. Chem.Soc., structures of 1, 2 and 3 show possibility of novel 2D or 3D Dalton T rans., 1988, 967. intermolecular contacts through ptdt ligands in place of ‘span- 11 L andolt-Bo�rnstein Zahlenwerte und Funktionen aus ning overlapping’ of the Ni(dmit)2 complexes, which is the only Naturwissenschaften und T echnik, Neue Serie II/11, Springer- Verlag, 1981. unique example of a 2D molecular arrangement of conducting 12 A. Kobayashi, T. Naito and H. Kobayashi, Phys. Rev. B., 1995, transition metal complexes.12–15 Moreover, a new molecular 51, 3198. conductor with p–d interactions will be expected if a magnetic 13 R. Kato, H. Kobayashi, H. Kim, Y. Sasaki, T. Mori and H. transition metal atom is incorporated.16 In order to meet Inokuchi, Chem. L ett., 1988, 865. requirement (2), further experiments are required. Very recently 14 A. Kobayashi and H. Kobayashi, Molecular Metals and black crystals of fairly conducting neutral Ni(ptdt)2 have been Superconductors Based on T ransition Metal Complexes, in Handbook of Organic ConductiveMolecules and Polymers, ed. H. S. obtained by electrocrystallization with a room temperature Nalwa, John Wiley & Sons, Ltd., 1997, vol 1, p. 276. conductivity of 2.1 S cm-1 and an activation energy of 0.11 eV. 15 A. Kobayashi, A. Sato, T. Naito and H. Kobayashi, Mol. Cryst. The conductivity is significantly higher than values normally L iq. Cryst., 1996, 284, 85. observed for other neutral complexes such as dithiolenes 16 H. Kobayashi, A. Miyamoto, R. Kato, F. Saka, A. Kobayashi, (<10-3 S cm-1) or TTF dithiolenes (<10-1 S cm-1).2 Y. Yamakita, Y. Furukawa, M. Tasumi and T. Watanabe, Phys. Rev. B: Condens.Matter, 1993, 47, 3500. We thank Mr. H. Fujiwara and Miss E. Arai of the Institute for Molecular Science for their valuable discussions and Miss Paper 7/04518B; Received 26th June, 1997 J. Mater. Chem., 1998, 8(2), 301–307 3

ISSN:0959-9428    

DOI:10.1039/a704518b

出版商:RSC    

年代:1998

数据来源: RSC