摘要:
J. CHEM. SOC. DALTON TRANS. 1995 1769Amphiphilic Terpyridine Complexes of Ruthenium andRhodium displaying Lyotropic MesomorphismJohn D. Holbrey,*aa Gordon J. T. Tiddyb and Duncan W. BruceYa Centre for Molecular Materials and Department of Chemistry, The University, Sheffield S3 7HF, UKDepartment of Chemistry and.Applied Chemistry, Salford University, Salford M5 4 WT, UKNew 4‘-alkyl-substituted 2,2’: 6’,2”-terpyridine (4‘R-terpy) compounds have been synthesised from4’-methyl-2,2’: 6’.2‘’-terpyridine and an appropriate 1 -bromoalkane and complexed with ruthenium andrhodium to yield new bis(terpyridine) complexes [Ru (terpy) (4’R-terpy)12+ ( R = C,H, or C,H,)and [Rh(terpy) (4’R-terpy)13+ (R = C,H,) as chloride and hexafluorophosphate salts. Thesecomplexes are amphip hilic being structurally related to surfactant tris (bi pyridi ne) rut heni um complexes.Both ruthenium and rhodium complexes with R = C,H, and chloride counter ions show lyotropicmesomorphism in water, and the ruthenium complex with R = C,H, shows mesophase formation inethylene glycol.For several years we have been looking at the synthesis andproperties of metal-containing liquid crystals.These haveprimarily been thermotropic mesogens where liquid-crystallinebehaviour is mediated by temperature. The incorporation ofa metal complex’ can be used to introduce novel physicalmodifications to the underlying properties of the mesophase(i. e. magnetism, colour, chirality, electronic properties). Morerecently we have started to look at metal-containing lyotropicliquid-crystal systems where mesomorphism is mediated byconcentration in solution.The mesogenic units are molecularaggregates comprising either micelles or columns.Metal-containing lyotropic liquid crystals have not beenwidely studied although interest in this area is growing. Notablecontributions have been made by Usol’tseva et al. with studiesof anionic phthalocyanine derivatives in water and by Praefcke,Usol’tseva and co-workers on tetrapalladium organylcomplexes which have a disc-like structure and form lyotropicmesophases in oil-continuous solutions (i.e. tetradecane). Inboth examples, lyotropic mesophases are formed throughaggregation of the disc-like molecules into short columns whichbecome ordered. These materials can show nematic andhexagonal phases, analogous to the columnar discoticmesophases shown by some thermotropic materials.This phasebehaviour is common for many dye molecules4 but is nottypical of the most common lyotropic materials, surfactants.Surfactants have an amphiphilic structure comprising ahydrophilic head and one or more hydrophobic (usuallyhydrocarbon) chains. They form micelles above the criticalmicelle concentration (c.m.c.) which interact at higherconcentrations to form lyotropic liquid-crystal phases.We have centred our effort on materials which have astructural motif similar to simple surfactants, havingsuccessfully prepared transition-metal complexes which showsurfactant-type mesomorphism in water (ie. the meso-morphism is based on the formation and ordering of micelles).The lyotropic behaviour of amphiphilic tris(2,2‘-bipyridine)-ruthenium surfactants (Fig.l), synthesised using the methoddescribed by Seddon and Y o ~ s i f , ~ ~ has been investigated.8These materials show remarkable stability compared with ourearlier examples, 5 3 6 allowing complete mesophase characteris-ation by microscopy and small-angle X-ray scatteringmeasurement^.^Sir Edward Frankland Fellow of the Royal Society of Chemistry,1 994- 1 99 5.2+R = Me, alkylR’ = alkylFig. 1 Tris(2,2’-bipyridine)ruthenium surfactantsWe have expanded the scope of these systems by the synthesisof related surfactant tris(2,2’-bipyridine)rhodium complexes,these being the first examples of cationic surfactants containingthree positive charges.Even more remarkable, the chargeis localised on a single head group. This is not possiblein conventional surfactants and illustrates the flexibility ofmetal-containing surfactants. Lyotropic mesophases wereobserved for the rhodium complexes which are similar to thosefor the ruthenium complexes but which showed instability tophotochemical decomposition when in solution and could notbe fully characterised.In order to address the aspects of stability of the complexes insolution and mesophases, and to extend the range of this work,we have looked at some related ligand systems. Here we reporton the synthesis of two new 4’-substituted 2,2‘ : 6’,2”-terpyridinederivatives (I, I1 in Scheme 1) and their complexes 1-3 witheither ruthenium and rhodium.Transition-metal complexesof terpyridine (terpy) and its derivatives (i.e. 4’-phenyl-2,2’ :6’,2”-terpyridine) have been widely investigated, lo with thetridentate, conjugated aromatic nature of the ligand leading tointeresting modifications of the electronic and photochemicalproperties of the metal centre (ie. redox potentials,absorption and emission spectra) and also showing increasedstability when compared to 2,2’-bipyridine (bipy) complexesand the potential to stabilise more than one oxidation state.Platinum terpyridine complexes have been shown to inter-calate with DNA and this behaviour has been extensivelystudied with reference to potential anticancer activity. Bis-(terpyridine)metal complexes are also intrinsically achiral i1770 J.CHEM. SOC. DALTON TRANS. 1995nRII RzCjgH39I1 R=C31H63Scheme 1 Synthesis of 4'-alkyl-2,2' : 2",6"-terpyridines. (i) Me,CO,NaH, tetrahydrofuran (thf); (ii) NH,O,CMe; ( i i i ) (CF3S0,),0; (iv)SnMe,, [PdCI,(PPh,),]; (u) (a) LiNPr',, thf, < 0 OC, (b) C18H37Br orC30H3 1 BrcnH2nt1M n m1 Rh 19 32 Ru 19 23 Ru 31 2contrast to tris(bipyridine)metal complexes which exhibit twoisomers, the A and A forms.The lyotropic mesophases formed for a surfactant depend onstructural features of the individual molecules (i.e. ratio of headgroup cross-section to hydrophobic volume and length) andhave been described by Mitchell and co-worker~.'~ Frommodels of the terpyridine and bipyridine complexes (Fig.2) itis dear that both have very similar structures, the metal co-ordination sphere containing six pyridine rings. The size of thepolar head group should not change for the terpyridinecomplexes compared to the bipyridine complexes, and wewould anticipate that a similar mesomorphic behaviour wouldbe observed (ie. formation of an micellar I, cubic phase).Synthesis2,2' : 6',2"-Terpyridine compounds alkylated at the 4' positionwere prepared from commercially available ethyl pyridine-2-carboxylate in good overall yield using a five-step synthesis (seeScheme 1). Using a combination of the methods of Potts l4 andConstable and co-workers, ethylpyridine-2-carboxylate andacetone were combined in a Claisen condensation followedby Hantzsch cyclisation of the resulting 1,2,5-triketone toyield 2,6-di-2-pyridyl-4( 1 H)-pyridone.This was convertedFig. 2 Space-filling models of (4'-substituted terpyridine)(terpyri-dine)metal (above) and bis(bipyridine)(4'-substituted 4-methylbipyri-dine)metal complexes (below)into 2,2' : 6',2"- terpyridine-4'- trifluorome thanesulfonate withtrifluoromethanesulfonic anhydride and methylated using apalladium-catalysed coupling16 with tetramethyltin, to yield4'-methyl-2,2' : 2,6'-terpyridine. The long alkyl chains werethen added by direct alkylation of the methyl group with lithiumdiisopropylamide and the corresponding 1 -bromoalkaneBr(CH,),- ,CH, under similar conditions to those used earlierfor the alkylated bipyridines. The 4'-alkylated derivatives showreduced melting points compared to the parent 4'-methylterpyri-dines, in agreement with the melting points of other 4'-functionalised terpyridine derivatives.Rhodium and ruthenium complexes of the new 4'-alkylatedterpyridine compounds with the general formula[M(te1-py)(4'R-terpy)]~+.mX- [M = Ru (m = 2) or Rh (rn =3); R = ClgH39 or C31H63; X = c1 or PF,] were preparedfrom [MCl,(terpy)].A trans-dialkyl complex, CRu(4'R-terpy),]Cl, 4 (R = C19H39) was synthesised from RuCl, andthe 4'-alkylterpyridine.Bis(terpyridine)ruthenium complexes were convenientlyprepared by reaction of [RuCl,(terpy)] and a 4'-functionalisedterpyridine in ethanol at reflux, to yield the desired product.However the reaction was considerably slower than thecorresponding reaction between cis-[RuCl,(bipy),] and abipyridine.In contrast, direct combination of [RhCl,(terpy)]with a second terpyridine failed to yield any reaction due thestrength of the bonds between the Rh3+ centre and the threeremaining chlorides. The inertness of [RhCl,(terpy)] to simplesubstitution of the chlorines by other ligands has been noted bySauvage et al. l 7 and the method described in their work hasbeen used to prepare the bis(terpyridine)rhodium complexes.Thus, [RhCl,(terpy)] was first treated with a silver salt (eitherAgNO, or AgBF,) in a weakly co-ordinating solvent (acetone isused for terpyridine complexes). The silver cation acts as both aLewis acid and chloride-ion scavenger to remove the co-ordinated chloride ions from the metal centre.In the resultingintermediate, [Rh(terpy)(solv)J3 ', the weakly co-ordinatingsolvent (solv) molecules can easily be displaced by a second,functionalised terpyridine ligand.Reaction of [RhCl,(terpy)] with the substituted 4'-alkylterpy-ridine and a silver salt yielded the nitrate or tetrafluoroboratesalt (depending on the silver salt used) which was not isolated.The crude product was dissolved in water and precipitatedas the -hexafluorophosphate salt by addition of aqueousammonium hexafluorophosphate. The hexafluorophosphateanions were readily exchanged for chloride by precipitatioJ. CHEM. SOC. DALTON TRANS. 1995 1771from dry acetone solution using LiCl to yield thebis(terpyridine)rhodium complex, [Rh(terpy)(4'R-terpy)]Cl, 3(R = C,,H,,), as a colourless powder which was extremelyhygroscopic when isolated.The complex [RuCl,(terpy)] was treated with a substitutedterpyridine using a silver salt to promote the removal ofchloride from the ruthenium complex, which allowed efficientformation of the [R~(terpy)(4'R-terpy)]~ + dication which wasobtained as the hexafluorophosphate salt.However, anionexchange to the chloride salt could not be achieved. Theaddition of LiCl to solutions of the hexafluorophosphate ortetrafluoroborate salts (from the crude reaction mixture) inacetone precipitated the metal complex with mixed counterions, [Ru(terpy)(4'R-terpy)]ClmX2 - m (X = PF,, BF, or NO,depending on the initial counter ion). The solubility of thesecomplexes was intermediate between those of the hexafluoro-phosphate and chloride salts which allowed ready formation ofthe PF, salt, but precluded subsequent efficient conversion intothe desired complex with chloride counter ions. Similarly, ion-exchange chromatography (Sephadex LH-20) yielded poorconversion into the chloride salt.The ruthenium complexes were obtained as stable, redpowders.The rhodium complex was obtained as a colourless,hygroscopic powder as the chloride salt and as a pale yellowto pale violet solid for the hexafluorophosphate salt, thecolour depending on the purity and the residual solvent inthe complex. Rhodium terpyridine complexes have beenreported to vary from colourless for chloride and perchloratesalts through yellow to red for iodide salts, as a functionof anion polarisability.This is interpreted as a decrease in inner-sphere hydration through closer covalent approach of theions lowering the energy gap for the charge-transfer process.We have found that a solution of the rhodium complexes ina highly co-ordinating solvent such as dimethyl sulfoxidechanges from colourless to yellow as the complex dissolves.Proton NMR assignments for the terpyridine complexes ofruthenium and rhodium are shown in Table 1. Spectra wereobtained in (CD,),SO (all ruthenium complexes), (CD,),CO(rhodium hexafluorophosphate salts) and CD,OD (rhodiumchloride salts). The complexes contain two, orthogonal C,symmetry axes which simplify the NMR spectra and two sets offour signals are expected for each terpyridine ligand with afurther signal for the 4-proton of the unsubstituted terpyridine.In practice, signals from the two terpyridine ligands wereindistinguishable to the limiting resolution of the NMRexperiment and the observed spectra were simplified further togive a signal (each 4 H) for each of positions 3/3", 4/4,5/5" and3'/5' of terpyridine and a signal (1 H) for the unsubstitutedterpyridine 4' position.The 6/6" signals showed a distinctupfield shift for the complexes compared to the freeterpyridines. The shielding of the nuclei was indicative of theirlocation over the central ring of the opposing terpyridine. Inspectra of the rhodium complexes hyperfine J(Rh-H) coupling( c 0.25 Hz) was observed for the protons of the terpyridinerings, especially in the 3,4, 5 positions.Proton NMR spectra in (CD,),SO were obtained forcomplexes containing ruthenium with chloride and hexafluoro-phosphate anions.The chemical shift of the signals showedno anion dependency, which has also been reportedlg forsurfactant tris(bipyridine)ruthenium complexes. Spectra takenin different solvents [(CDJ2S0, CD,OD, (CD,),CO, D,O]did show a solvent dependence.The chloride salts of the ruthenium complexes, in contrast tothe very high water solubility of the analogous bipyridinecomplexes, were only slightly soluble in water. The chloride saltof the rhodium complex was very hygroscopic in air and, unlikethe ruthenium complexes, was very soluble in water.Ruthenium and rhodium complexes as chloride salts wereinvestigated for lyotropic mesomorphism i'n water and inethylene glycol, an organic polar solvent.Table 1 Proton NMR shift assignments (J/Hz) for [M(terpy)(4'R-terpy)ln+-nX- complexes (R = C, 9H39)MX, nSolventTerminal CH,AlkylC 3 25,5"/5,,5",6,6"/6,,6",4,4"/4,,4",3,3"/3,,3','b3',5'3'b,5'bRh"'PF,, 3(CD3)2C00.88(3 H, t, J = 6.5)1.29(32 H, m)3.30(2 H, t, J = 7)7.62(4 H, 2 x dd)8.11, 8.14(4 H, 2 x d, J = 6.5)8.40, 8.44(4H,2 x dd)8.97(4 H, d, J = 7)9.13( 1 H,d, J = 7)9.18(2 H, s)9.50(2 H, d, J = 7)Rh"'c1, 3CD30D0.9(3 H, t, J = 6.5)1.30(34 H, m>2.10(2 H, t )7.78, 7.61(4 H, 2 x dd)7.88, 7.924 H , 2 x d)8.34, 8.37( 4 H , 2 x dd)8.939.0(1 H,d, J = 7)9.07(2 H, s)9.18(2 H, d, J = 7)(4 H, dd)Ru" c1, 2(CD,),SO0.83(3 H, t, J = 7)1.05-1.65, (32 H, m)2.03 (2 H, m)3.14( 2 H, t, J = 7.5)7.23, 7.27(4 H, 2 x d, J = 7)7.37(4 H, m)8.00(4 H, dd, J = 6.5)8.88(4 H, d, J = 7)8.50(1 H, dd, J = 7)9.099.14(2 H, d, J = 7.5)(2 H, s1772 J.CHEM. SOC. DALTON TRANS. 1995Lyotropic MesomorphismThe mesomorphic behaviour of the complexes in water wasinvestigated by optical microscopy using the Lawrencepenetration experiment 2o where solvent is introduced onto amicroscope slide containing surfactant. A concentrationgradient is created at the interface between neat surfactant andthe solvent and lyotropic mesophases are observed across theboundary and can be monitored with changing temperature.The ruthenium complex [Ru(terpy)(4'R-terpy)]C12 (R =C19H3,) showed mesomorphism broadly similar to that of theanalogous tris(bipyridine)ruthenium complex, exhibiting anormal micellar cubic (I1) mesophase between the solution andsolid regions.However the specific behaviour varied becauseof the difference in solubility between the two rutheniumcomplexes. In the penetration experiment the complex showedonly limited solubility in water and no mesophase formation atroom temperature or on gentle warming. A distinct increase insolubility was observed when the temperature was raised tobetween 65 and 70 "C and a viscous, isotropic cubic phase thenformed at the solid-solution interface from around 73 "C;the mesophase persisted to < 100 "C.In ethylene glycol thecomplex was soluble from room temperature, solubilityincreasing with increasing temperature up to 150 "C; however,no evidence of lyotropic mesophase formation was found.The bis(terpyridine)ruthenium complex with the longer alkylchain, [Ru(terpy)(4'R-terpy)]C12(R = C,,H,,), failed to showany mesophase formation in the penetration experiment withwater. This complex was insoluble in water until thetemperature was raised to ca. 70°C and showed only limitedsolubility between 70 and 100 "C. The reduced solubility of thiscomplex compared to both the shorter-chain analogue and thecorresponding bipyridine complex was responsible for the lackof mesophase formation in water.The penetration experimentin ethylene glycol did show a viscous, isotropic lyotropicmesophase (assigned as I, cubic) at high temperatures. Thematerial was insoluble in ethylene glycol until 82 "C at whichpoint it started to dissolve. The solubility increased withincreasing temperature and a viscous, isotropic mesophaseformed at the solution-solid interface from 96 "C. This phasegrew into the solid on increasing temperature and was stable to> 150 "C. From 136 "C the mesophase began to clear to anisotropic solution from the solution-mesophase boundary.The rhodium complex, [Rh(terpy)(4'R-terpy)]Cl, (R =C,,H39), proved to be very hygroscopic, absorbing moisturefrom the air at room temperature to yield a viscous, opticallyisotropic material from room temperature.In the penetrationexperiment this material was heated to 110 "C to remove water,then cooled to room temperature; the crystalline solid soformed was contacted with water and observed to form aviscous, isotropic mesophase from room temperature whichpersisted on heating to 100 "C. Small air-bubbles trappedwithin this phase became very angular and formed perfecthexagonal shapes. These were reminiscent of the profile alongthe long diagonal axis of a cube. The shapes of the bubblesformed in cubic mesophases have been analysed 2' and used as amethod of characterising the phase type.ConclusionUsing terpyridine derivatives, we have prepared amphiphilicruthenium and rhodium complexes that are comparable withexisting surfactant tris(bipyridine) complexes.However, thesolubility of the bis(terpyridine)ruthenium complexes withchloride counter ions is much lower than that of the relatedtris(bipyridine) complexes, so that in order to obtain asufficiently high surfactant concentration in water for micelleformation the ruthenium complex 2 must be heated to above70 "C. A cubic phase forms from 73 "C. The ruthenium complex3, which had proportionately a much higher hydrophobiccontent, showed comparably lower solubility and did not showany mesophase formation up to 100 "C, but did show a cubicphase in ethylene glycol. The much more soluble bis(terpyri-dine)rhodium complex 1 showed a cubic phase, assigned I,,from room temperature.The reduced solubility limits the range of temperature overwhich lyotropic mesophase formation is observed, but thesecomplexes do act as surfactant systems, forming the expectedcubic mesophase. The reduced solubility helps in our qualitativeunderstanding of the requirements for formation of transitionmetal-containing lyotropic liquid crystals.We have found thatthe Krafft point (minimum temperature at which micelles canform) is high ( > 70 "C) for these terpyridine complexes whereasfor the structurally very similar ruthenium tris(bipyridine)surfactants it is much lower being typically around ambienttemperature.We have also synthesised the related terpyridine complexwith two trans alkyl chains, [Ru(4'R-terpy),12+ 4 (R =C,9H39), prepared from RuCI, and 2 equivalents of the alkyl-substituted terpy.This complex, as the chloride salt, failedto show any mesophase formation, being insoluble in waterand was only sparingly soluble in glycol even at elevatedtemperatures. However it is interesting to speculate on thestructure of a possible mesophase formed from an amphiphilewith two tails and the head group placed symmetrically in thecentre of the molecule.ExperimentalMicroanalyses were performed at the University of Sheffield.All chemicals were used as received unless otherwise specified.Infrared spectra were recorded on a Perkin-Elmer 684 infraredspectrometer as KBr discs, 'H NMR spectra on a BrukerWM250 spectrometer; proton chemical shifts are quotedrelative to an internal deuterium lock. Mesomorphism wasstudied by heated-stage polarising microscopy using a ZeissLabpol microscope equipped with a Linkam TH600 hot stageand PR600 temperature controller.Synthesis of 4"- Alkyl-2,2' : 6',2"- terpyridines.- 1,5-Di-2-pyridylpentane-1,3,5-trione. To NaH (2.25 g, 80% dispersion inoil, 75 mmol) in thf (50 cm3) heated to reflux under N, wasadded a solution of ethylpyridine-2-carboxylate (10.1 cm', 75mmol) and acetone (1.8 cm3, 25 mmol) in dry thf (30 cm3),dropwise over ca. 4 h, and the reaction mixture heated for 2 hgiving an orange solution. The reaction mixture was thencooled, the solvent removed under reduced pressure and theresidue dissolved in water (200 cm3). After filtration throughCelite, the solution was neutralised by the addition of aceticacid, precipitating a fine, intense yellow powder.This wasfiltered off and crystallised from diethyl ether (yield 4.5 g, 71%).M.p. 103 "C (lit.," 103-105 "C).2,6-Di-2-pyridyl-4( 1 H)-pyridone. Ammonium acetate (4.0 g)and 2,5-di-2-pyridylpentane- 1,3,5-trione (2.0 g, 7.46 mmol)were dissolved in absolute EtOH (50 cm3) and heated to reflux.After 6 h the resultant brown solution was concentrated to ca. 8cm3 and cooled to 0 "C, precipitating the product as colourlesscrystals which were crystallised from ethanol (1.76 g, 94%).M.p. 165-166 "C (lit., 165,15 166-168 "CI6) IR (KBr) :vNH 3300J. CHEM. soc. DALTON TRANS. 1995 1773vco 1630 cm-'. 'H NMR (250 MHz, CDCl,):6 9.9 (1 H, br,NH), 8.73 [2 H , d, 3J(H6*sH6"9s" ) = 6, H6,6"], 7.87 [2 H, d,6, 3J(H3*4H3".4") = 7.5, H4.4"], 7.42 [2 H, dd, 3J-3J(H3*4H3",4" = 7.5, H3*3"] 7.77 [2 H, dd, 3J(H4*5H4"75") =(H5,4Hs".4") = 6, 3J(HS,6H5".6") = 6Hz, H5,5"] and 7-29(2 H, s, H3'*5' 1.4'-( TrzJEuoromethylsulfonyl)-2,2' : 6',2"-terpyridine.Trifluoro-methanesulfonic anhydride (600 mg, 2 mmol) was added over30 min to a stirred solution of 2,6-di-2-pyridyl-4( 1 H)-pyridone(500 mg, 2 mmol) in anhydrous pyridine ( 5 cm3) cooled to 0 "Cunder N,. The solution was allowed to warm to roomtemperature, stored for 48 h, then poured onto ice-water (50cm3) and stirred for 30 min. The pale brown precipitate wasfiltered off, washed with cold water (50 cm3) and air dried. Thesolid was dissolved in hexane (10 cm3) with warming, theinsoluble portion was filtered off and the filtrate concentratedyielding colourless crystals on cooling (0.43 g, 57%).M.p.108 "C (lit.," 108 "C). 'H NMR (250 MHz, CDCl,): 6 8.75 [2H, d, 3J(H6*5H6"*s") = 4, H6,6"], 8.60 [2 H, d, 3J(H3*4-H3"*4") = 7, H3,3"], 8.41 (2 H, S, H3's5'), 7.87 [2 H, dd,H, dd, 3J(H5,4H5".4" ) = 7, 3J(H5,6Hs"96") = 4 Hz, H'"''].3J(H4,sH4",5") = 7, 3J(H3,4H3",4" ) = 7, H4,4"] and 7.40 [24'-Methyl-2,2' : 6',2"-terpyridine. Tetramethyltin (1 cm', 7mmol), 4'-(trifluoromethylsulfonyl)-2,2' : 2",6'-terpyridine (1.9g, 5 mmol), [PdCl,(PPh,),] (100 mg) and LiCl (1 g, excess)were dissolved in dimethylformamide (100 cm3) and heated atreflux under N, for 4 h, forming a palladium mirror. The darkreaction mixture was concentrated in vucuo to a dark oil whichwas taken up in water (100 cm3) and extracted into CH,CI,(3 x 100 cm3).The organic extracts were combined and thesolvent removed under reduced pressure to give a brown gum.Purification by column chromatography (neutral alumina,pentane-ethyl acetate 9 : 1) yielded a white crystalline solid (0.67g). M.p. 101 "C (lit.,,, 97-100 "C) (Found: C, 77.3; H, 5.45; N,16.8. Ci6HI3N3 requires C, 77.7; H, 5.3; N, 17.0%). 'H NMR(250 MHz, CDCl,): 6 8.67 [2 H, d, 3J(H635H6"7s" 1 = 4,H6,6"], 8.60 [I2 H, d, 3J(H3*4H3"*4" ) = 7.5, H3v3"], 8.28 (2 H,s, H3"''), 7.84 [2 H, dd, 3J(H4,5H4",5" ) = 7, 3J(H3*4-H3"74") = 7.5, H4q4"], 7.30 [2 H, dd, 3J(Hs,4H5"74") = 7,3J(H5*6H5"*6") = 4 Hz, H5,'"] and 2.55 (3 H, s, CH,).4'-Nonadecyl-2,2' : 6',2"-terpyridine, I.To a stirred solution ofdiisopropylamine (0.36 cm3) in thf (2.5 cm3) cooled to 0°Cunder N, was added dropwise LiBu ( I .56 cm3, 1.6 mol dm-,solution in hexane) and stirred for 1 h. A solution of 4'-methyl-2,2':2",6'-terpyridine (0.6 g, 2.43 mmol) in thf ( 5 cm3) wasadded and stirred for 1 h followed by addition of a solution of I -bromooctadecane (0.81 g, 2.4 mmol) in thf (20 cm3). Thereaction mixture was stirred at 0 "C for 1 h, allowed to come toroom temperature and stirred at room temperature for 12 h.Water ( I 0 cm3) was added and the thf removed under reducedpressure, water (30 cm3) was added and the yellow precipitatefiltered off, washing with water and Et,O to give a whitepowder. Crystallisation from ethanol yielded colourless crystals(0.80 g, 66%).M.p. 78-79.5 "C (Found: C, 81.8; H, 10.1; N, 8.2.C34H49N3 requires C, 81.7; H, 9.9; N, 8.4%). 'H NMR (250MHz, CDCI,): 6 8.67 [2 H, d, 3J(H67sH6"35") = 4, H6*6"],8.63 [2 H, d, 3J(H3,4H3".4") = 7.5, H3,3"], 8.28 (2 H, S,7.5, H4*4"], 7.32 [2 H, dd, 3J(H5*4H5 *"") = 7, 3J(H5*6-H5",6" ) = 4, H5*5"], 2.77 [2 H, ty = 7.5, C,H2), 1.75(2 H, m, C,H,), 1.27 (32 H, m, alkyl) and 0.86 (3 H, t, = 7Hz, CH,).4'-Hentriacontyl-2,2' : 6',2"-terpyridine 11. This compoundwas prepared from 4'-methyl-2,2' : 6',2"-terpyridine (0.60 g, 2.43mmol) in an analogous manner to that of I and crystallised fromethanol as white microcrystals (1.53 g, 94%). M.p. 93.5-95.5 "C(Found: C, 82.7; H, 11.1; N, 5.9. C,,H,,N, requires C, 82.7; H,11 .O; N, 6.2%).'H NMR (250 MHz, CDCI,): 6 8.67 [2 H, d,7.5, H3,3"], 8.28 (2 H, s, H3"" ), 7.85 [2 H, dd, 3J(H43s-) = 7, 3J(H3,4H3".4" ) = 7.5, H4*4"], 7.32 [2 H, dd,), 7.85 [2 H, dd, 3J(H4,sH4".5") = 7,,, 3J(H3*4H3",4" ) = H3',5') = 4, H6*6"], 8.63 [2 H, d, 3J(H3*4H3"74" ) = 3J(H6,5H6",5"H4". 5"3J(H5,4H5".4" ) = 7, 3 ~ ( ~ 5 , 6 ~ 5 " . 6 " ) = 4, H5*5"], 2.77 (2 H, t,3J = 7.5, C,H,), 1.75 (2 H, m, CBH2), 1.27 (58 H, m, alkyl) and0.86 (3 H, t, 3J = 7 Hz, CH,).Synthesis of Me tal- Terp y r idin e Complexes. -T he startingcomplexes [RuCl,(terpy)] and [RhCl,(terpy)] were preparedfrom RuCI,~xH,O or RhCI,*xH,O (Johnson Matthey) and2,2' : 6',2"-terpyridine (Aldrich) by literature methods. 23To [RhCl,(terpy)] (0.25 g, 0.5 mmol) dissolved in acetone-ethanol (250 cm3, 6: 1 ratio) was added AgNO, (0.22 g, 1.5mmol, 3 equivalents) and the mixture heated to reflux under N,.After 3 h the solvent was removed under reduced pressure andthe residue dissolved in BuOH (200 cm3), filtered through Celiteand 4'-nonadecyl-2,2' : 6',2"-terpyridine (0.25 g, 0.5 mmol) wasadded.The mixture was heated at reflux under N, for 12 h,cooled and the solvent removed under reduced pressure. Theresidue was dissolved in water (ca. 200 cm3), filtered and thehexafluorophosphate salt precipitated upon careful addition ofaqueous NH,PF6 as a fine grey powder and recrystallised fromP,Rh requires C, 41.8; H, 5.3; N, 6.6%).[Rh(terpy)(4'R-terpy)]CI, 1 (R = C19H39, X = Cl). To afiltered solution of the hexafluorophosphate salt (0.617 g) inacetone (50 cm3) was added dropwise a saturated solution ofLiCl in acetone until precipitation ceased.The chloride salt wasobtained as a hygroscopic white powder, filtered off, dried inuucuo (0.40 g, 81% yield) and stored over silica gel. It is lightand moisture sensitive and was stored in the dark.[Ru(terpy)(4'R-terpy)]Cl, 2 (R = c19H39, X = CI). Thecomplex [RuCl,(terpy)] (0.25 g, 0.57 mmol) and 4'-nonadecyl-2,2': 6',2"-terpyridine (0.25 g, 0.50 mmol) in ethanol (100 cm3)were heated at reflux under N, for 24 h during which time, themixture changed to a dark red-brown. It was filtered and thefiltrate evaporated to dryness under reduced pressure.Chromatography [Sephadex LH-20, ethanol-water (3 : 1)eluent] yielded the product as the major, deep red band whichwas dried in uucuo to give a red glass (0.35 g, 73%) (Found: C,58.8; H, 7.0; C1, 7.2; N, 8.05.Hexahydrate requires C, 58.1; H,7.2; C1, 7.0; N, 8.3. Pentahydrate requires C, 59.1; H, 7.1; Cl,7.1; N, 8.45%). Samples gained weight on standing.The complex [RuCl,(terpy)] (0.25 g, 0.5 mmol) and AgBF,(0.32 g, 1.3 mmol) in acetone (100 cm3) were heated at reflux inair for 2 h to yield a dark purple mixture. The solvent wasremoved under reduced pressure and the residue dissolved inBuOH (50 cm3), filtered and 4'-nonadecyl-2,2' : 6',2"-terpyridine(0.25 g, 0.5 mmol) was added. The reaction mixture was heatedat reflux for 3 h to give a deep red solution which was cooled,the solvent removed under reduced pressure and the residueredissolved in acetonitrile, filtered and concentrated to yieldthe orange-brown tetrafluoroborate salt.The trihydrate of thehexafluorophosphate salt was prepared as an orange-red power(0.47 g, 80%) from the crude tetrafluoroborate in ethanolicsolution by precipitation with aqueous NH,PF, (Found: C,49.7; H, 5.3; N 7.0. Calc.: C, 50.0; H, 5.7; N, 7.1%).[Ru(terpy)(4'R-terpy)]C12 3 (R = C31H63y X = C1). Thecomplex [RuCl,(terpy)] (0.187 g, 0.42 mmol) and 4'-hentriacontyl-2,2' : 6',2"-terpyridine (0.124 g, 0.19 mmol) inethanol (95%, 70 cm3) were heated at reflux under N, for 24 h toyield a dark, red-brown mixture This was filtered and the filtrateevaporated to dryness under reduced pressure. Chromatogra-phy [Sephadex LH-20, ethanol-water (3 : 1) eluent] yielded theproduct as the major, deep red band which was dried in U ~ C U O togive a red glass (0.196 g, 87%) (Found: C, 61.4; H, 7.7; N, 6.6.(Hexahydrate requires C, 62.0; H, 8.2; N, 7.1%.)[Ru(4'R-terpy),]CI~03] 6 (R = C19H39).A mixtureof RuC13*3H20 (0.014 g, 5.35 x mol) and 4'-nonadecyl-2,2' : 6',2"-terpyridine (0.054 g, 1.1 x I O-, mol) in95% ethanol (50 cm3) was heated at reflux for 1 h, AgNO,(0.055 g, 6 equivalents) was added and the mixture heated for[Rh(terpy)(4'R-terpy)][PF6], 1 (R = C19Hj9, X = PF6).dry acetone (Found: C, 42.1; H, 5.5; N, 6.4.[Ru(terpy)(4'R-terpy)][PF6], 2 (R = C19H39, x = PF6)1774 J. CHEM. SOC. DALTON TRANS. 199512 h until it had changed to a dark red-brown. The mixture wascooled, filtered and the solvent removed under reduced pressureto give a dark gum which was purified by chromatography(Sephadex LH-20, absolute ethanol).The red band wascollected, the solvent removed under reduced pressure anddried in vacuo to give a red glass (0.064 g, 93%). The productwas insoluble in water and elemental analysis for chlorineindicated mixed chloride-nitrate counter ions (Found: Cl, 3.3.Calc. : 3.0%). ‘H NMR (250 MHz, CDCl,); 6 0.82 (3 H, CH,),1.1-1.6 (alkyl), 1.95 (2 H, CBH2), 3.20 (2 H, C,H2), 7.2 (4 H),7.85 (2 H), 8.75 (2 H) and 8.85 (2 H).AcknowledgementsWe thank the SERC for a postdoctoral fellowship (to J. D. H.)under the 21st Century Materials Initiative and JohnsonMatthey for generous loans of ruthenium and rhodium salts.References1 D.W. Bruce, J. Chem. Soc., Dalton Trans., 1993, 2983; A. P.Polishchuk and T. V. Timofeeva, Russ. Chem. Rev., 1993, 62, 291;D. W. Bruce, in Inorganic Materials, eds D. W. Bruce andD. O’Hare, Wiley, Chichester, 1992; P. Espinet, M. A. Esteruelas,L. A. Oro, J. L. Serrano and E. Sola, Coord. Chem. Rev., 1992, 117,21 5 ; A.-M. Giroud-Godquin and P. Maitlis, Angew. Chem., Znt. Ed.Engl., 1991,30,402.2 N. V. Usol’tseva, V. E. Maizlish, V. V. Bykova, G. A. Ananeva,G. P. Shaposhnikov and N. M. Kormilitsyn, Russ. J. Phys. Chem.,1989,63, 1610.3 M. V. Usol’tseva, K. Praefcke, D. Singer and B. Gundogan, Liq.Cryst., 1994, 16, 60 1.4 T. K. Attwood, J. E. Lydon and F. Jones, Liq. Cryst., 1986, 1,499.5 D. W. Bruce, D. A. Dunmur, P. M. Maitlis, J:M. Watkins andG. J. T. Tiddy, Liq. Cryst., 1992, 11, 127.6 D. W. Bruce, I. R. Denby, G. J. T. Tiddy and J. M. Watkins,J. Muter. Chem., 1993,3,911.7 (a) G. Sprintschnik, H. W. Sprintschnik, P. P. Kirsch and D. G.Whitten, J. Am. Chem. Soc., 1976, 98, 2337; (b) K. R. Seddon andY. Z. Yousif, Transition Met. Chem., 1986, 11,443.8 D. W. Bruce, J. D. Holbrey, A. R. Tajbakhsh and G. J. T. Tiddy,J. Muter. Chem., 1993,3, 905.9 D. W. Bruce, J. D. 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Calvert and T. J. Meyer, Znorg. Chem., 1980,Horwood, Chichester, 1991.Chem. Soc., 1976,98,6159.Faraday Trans. 2, 1976, 1522.1990, 1405.and Breach, London, 1969, part 1, p. 1.1980,45, 168.19, 1404.Received 2 I st December 1994; Paper 4/07769
ISSN:1477-9226
DOI:10.1039/DT9950001769
出版商:RSC
年代:1995
数据来源: RSC