J O U R N A L O F C H E M I S T R Y Materials Formation of columnar arrangements in copper(II ) complexes of 2-phenylazomethinopyridine derivatives Chung K. Lai,* Kuo-Wen Wang and Raymond Lin Department of Chemistry, National Central University, Chung-Li, Taiwan, ROC Received 7th August 1998, Accepted 20th August 1998 The synthesis and mesomorphic properties of a homologous series of 2-(3¾,4¾,5¾-trialkoxyphenyl )- azomethinopyridines and their copper(II) complexes are reported.Liquid crystalline properties of the copper(II) complexes were studied by DSC analysis and polarized optical microscopy. The results indicated that copper complexes with six sidechains (3) exhibited columnar phases, whereas copper(II ) complexes with two or four sidechains (1 and 2) formed only crystalline phases.The structures of the mesophases for copper(II ) complexes 3 were characterized and confirmed as disordered hexagonal columnar phases (Colhd) by powder X-ray diVraction. Relatively high clearing points and the short range of mesophase temperature for the copper complexes were attributed to a relatively strong interaction of pyridyl core–core groups within the columns. The EPR spectra measured at various temperatures were also examined.prepared 3,4,5-trialkoxybenzoic acid chlorides in dried pyri- Introduction dine. These pyridine-based ligands obtained were white and Generation of various geometries and molecular shapes by obtained in a yield of 86–90%, and are highly soluble in incorporation of metal centers into organic moieties has been organic solvents. The ligands were characterized by 1H and widely applied to produce metallomesogenic structures.1,2 13C NMR spectroscopy.Three characteristic peaks at d 5.64, Transition metal coordination compounds are the largest 6.75 and 10.19 were assigned to olefinic methine-H (–CHLC–), category among this type of metallomesogenic materials owing aldehyde-H (–CHLN–) and imine-H (–CLN–H), and correct to their well known chemistry and rich structural diversity.structures were also supported by characteristic 13C NMR Columnar arrangements3–5 can be generated by use of comp- peaks at ca. 189.63 and 153.73 assigned to keto C–O and C–N lementary shapes of various molecules; disc-like,3,4 half disc- groups. Copper(II) complexes were obtained by the reaction like5 or tapered molecules, and of those, disc-like molecular of 2-phenylazomethinopyridines with copper(II) perchlorate structures are often formed by symmetric bonds with coordi- hexahydrate in refluxing THF–methanol.Reactions with copnation metal centers. Ligands used in this group were mostly per(II) acetate or copper(II) chloride with or without a base of various derivatives;1a such as b-diketones, salicylaldehydes, (for example KOH) resulted in recovery of intact ligands.salicylaldimines, enaminoketones, aroylhydrazine and pyr- Recrystallization twice from THF–methanol gave pure yellow– roles. Metal complexes thus prepared often produced disc-like greenish solids. Copper (d9) compounds which are paramagshaped molecules, and usually exhibited hexagonal or/and netic display only broad alkoxy signals in 1H and 13C NMR rectangular columnar phases.These so-called metal-containing spectra. Elemental analysis data in Table 1 also confirmed the liquid crystals are highly promising potential candidates in purity and identity of the complexes. electro-magnetic applications. In addition, the metal centers incorporated are also found to play an important role in the Mesomorphic properties resulting mesomorphic properties and physical properties.Liquid crystalline behavior for these copper(II ) complexes was Selective incorporation of diVerent metal centers with a specific studied and characterized by DSC analysis and polarized ligand often results in completely opposite mesomorphic optical microscopy.The formation of mesophases was found properties. While a detailed explanation based on the structural to be sensitive to the numbers of sidechains and the carbon and electronic configuration of metal centers on the mesolength of the sidechains, as often observed in columnar phases. morphic properties has been extensively discussed, a precise Copper complexes with six sidechains (3) exhibited columnar prediction of phase behavior has not yet been feasible.Here, phases, whereas copper(II) complexes with two (1) or four we report the preparation, characterization and mesomorphic sidechains (2) formed only crystalline phases. The phase- properties of a new series of copper complexes derived transition temperatures and enthalpies of all copper complexes from 2-(3,4,5-trialkoxyphenyl )azomethinopyridine structures, 1–3 are given in Table 2.For complexes 3, only when the which exhibit disordered hexagonal columnar phases. carbon chain lengths (n) were 16, (i.e. n=16 and n=18) was liquid crystallinity observed. The DSC analysis of copper Results and discussion complexes 3 showed typical columnar phase transitions of crystal-to-columnar-to-isotropic (K�Col�I ).Additional Synthesis crystal-to-crystal (K1�K2) transitions were also observed for complexes with lower carbon chain lengths (i.e. n=10, 12, 14). The synthetic route used to prepare substituted 2-phenylazomethinopyridine derivatives and their copper(II ) complexes is Upon heating, copper complexes melt into liquid crystalline phases with an optical texture of columnar superstructures as shown in Scheme 1.Methyl 3,4,5-trialkoxybenzoates and 3,4,5- trialkoxybenzoic acids were synthesized by literature pro- is often observed for disc-shaped molecules, and the textures observed showed highly characteristic birefrigence.4 A typical cedures,4 and 3,4,5-trialkoxybenzoic acid chlorides were obtained from the reaction of 3,4,5-trialkoxybenzoic acids and larger enthalpy (10.6–20.7 kJ mol-1) for the crystal-to-liquid crystal transition at lower temperatures (161–177 °C) and thionyl chloride in dried tetrahydrofuran. The 2-(3,4,5-trialkoxyphenyl )azomethinopyridine derivatives were synthesized a relatively lower enthalpy (0.84–1.60 kJ mol-1) for the liquid crystal-to-isotropic transition at higher temperatures by a condensation reaction of 2-aminopyridine with freshly J.Mater. Chem., 1998, 8(11), 2379–2383 2379Scheme 1Reagents and conditions: i, KOH (2.0 equiv.), refluxing in THF–H2O (1051), 12–24 h, 92–96%; ii, SOCl2 (2.0 equiv.), refluxing in dried THF, 4 h; iii, 1-aminopyridine (1.0 equiv.), refluxing in dried pyridine at 0 °C, then warming up and stirring at room temp., 16 h, 86–90%; iv, Cu(ClO4)2·H2O, refluxing in THF–EtOH, 2 h, 76–82%.Table 1 Elemental analysis data (%) of copper(II) complexes 1–3a liquid-like correlations between the rigid cores occurred at wider angle regions of 5.21 A° . Two other weaker characteristic Compound C H N diVractions4 corresponding to Miller indices (110) and (200), respectively, with a d-spacing ratio of (1/3)1/2 and (1/4)1/2 3 n=12 74.01 (73.73) 10.53 (10.44) 3.54 (3.58) were however not observed.The absence of distinct peaks at 14 75.02 (74.89) 10.93 (10.82) 3.24 (3.23) 16 75.99 (75.84) 11.36 (11.14) 3.02 (2.95) higher angle was consistent with DSC analysis of a relatively 18 76.71 (76.63) 11.45 (11.40) 2.75 (2.71) lower enthalpy for the columnar-to-isotropic transition, indica- 2 18 75.55 (75.27) 10.68 (10.66) 3.72 (3.66) tive of a highly disordered mesophase; i.e.there is no long- 1 18 72.64 (72.43) 9.22 (9.12) 5.67 (5.63) range order along the columns. aRequired values in parentheses. In most metallomesogens reported, the formation of liquid crystals is found to be controlled or determined by the magnitude of the intermolecular interaction forces1a which (179–180 °C) were observed.This relatively low value of the hold the metallomesogenic structures together. When they are transition enthalpy indicated that the mesophases were highly either too weak or too strong, a liquid crystalline phase is not disordered. The temperature range of columnar mesophases observed. Compared with other similar cII ) complexes for the copper complexes is slightly sensitive to the carbon with six sidechains, one feature noted for copper complexes 3 number of sidechains.At the crystal-to-columnar transition is that only derivatives with longer chains (n=16 and 18) the flexible side chains undergo disordering but the central exhibited columnar phases and derivatives with shorter chains core remains stacked in columns, however, the core unstacked (n=10, 12, 14) formed crystalline phases.Meanwhile they at the columnar-to-isotropic transition. have a relatively short range (4.0–18 °C) of mesophase tem- When cooled from their isotropic phases, the liquid crystal- peratures. An increased electron density due to the presence line complexes displayed optical textures, shown in Fig. 1, of lone pair electrons on the nitrogen atoms appears to increase which were a mixture of pseudo focal-conics and mosaic the intermolecular interaction between the stacking molecules, regions with linear birefrigent defects, suggesting hexagonal and this increasing force causes an increase in molecular columnar structures.The possibility of rectangular phases was packing or regularity within the columns. Therefore, longer also easily excluded owing to the absence of mosaic textures chains or/and more chains were critically needed to induce the with prominent wedge-shaped defect patterns.To further mesophase, and only a short temperature range of the confirm the structure of the mesophases, we performed a mesophase was observed. powder XRD diVraction experiment. The copper complex 3 (n=18) displayed a diVraction pattern of a two-dimensional EPR studies hexagonal lattice with an intense peak at 2h=43.61° at 175 °C.This diVraction corresponded to an intercolumnar distance (a X-Band EPR spectra of the copper complex 3 (n=16) measured at diVerent temperatures are shown in Fig. 2. The parameter of the hexagonal lattice) of 50.34 A° . However, 2380 J. Mater. Chem., 1998, 8(11), 2379–2383Table 2 Phase behaviora of copper(II) complexes 1–3 78.7 (17.4) 196.7 (19.4) 3 n=12 K1 K2 I ,bbb) ,bbb) 71.5 (16.5) 176.2 (15.8) 88.3 (25.8) 185.0 (22.3) 14 K1 K2 I ,bbb) ,bbb) 82.4 (30.1) 172.7 (19.4) 87.7 (29.1) 176.8 (19.4) 179.1 (1.22) 16 K1 K2 Colhd I ,bbb) ,bbb) ,bbb) 83.3 (26.8) 159.8 (20.7) 173.4 (1.60) 94.3 (21.6) 161.2 (10.6) 179.6 (0.90) 18 K1 K2 Colhd I ,bbb) ,bbb) ,bbb) 88.3 (27.2) 137.9 (12.0) 172.4 (0.84) 84.3 (30.8) 240.2 2 18 K1 K2 Id ,bbb) ,bbb) 77.7 (33.0) 216.2 94.3 (21.6) 294.5 1 18 K1 K2 Id ,bbb) ,bbb) 88.3 (27.2) 269.2 an is the number of carbons in the alkoxy chain.K1,K2=crystal phases; Colhd=columnar hexagonal disordered phase; I=isotropic; Id= isotropic with decomposition. The transition temperatures (°C) and enthalpies (in parentheses, kJ mol) were determined by DSC at a scan rate of 5.0 °Cmin-1.Fig. 2 EPR spectra of copper complex 3 (n=16) measured at: (a) room temperature of as-prepared sample, (b) 459 K; isotropic phase, (c) 438 K; columnar phase, (d) 370 K; crystalline phase, (e) cooling back to room temperature. Fig. 1 Optica l textures (100×) exhibited by complex 3 (n=16).Colhd cooling to 165 °C [Fig. 2(c)] corresponding to the mesophase, phase at 170 °C (top: thick sample) and at 165 °C (bottom: showed signals with clear hyperfine lines in the low-field region, thin sample). with three signals being observable and resolved. As the temperature was further reduced to 97 °C [Fig. 2(d)] and 25 °C [Fig. 2(e)], similar signals were observed. The slight change of top spectrum in Fig. 2(a) was for the as-prepared sample measured at room temperature, and consisted of two features, these signals with temperature was probably due to a preferred molecular orientation or arrangement at diVerent tempera- one barely observable shoulder at low field and a high-field signal. When the sample was heated to the clearing point at tures. Mesogenic copper complexes of bidentate SchiV bases have been extensively6 studied by EPR spectroscopy.In most 186 °C the signal width [Fig. 2(b)] became broader and unsymmetric with increased intensity. However, the spectrum on derivatives broad and unsymmetric signals at diVerent tem- J. Mater. Chem., 1998, 8(11), 2379–2383 2381peratures were observed, and the absence of the hyperfine 31.74, 51.43, 67.95, 113.83(C2,6), 122.16(C1), 131.32(C3,5), 162.77(C4), 166.53(CLO).structures was generally attributed to the strong exchange interaction among the paramagnetic copper centers. 3,4,5-Tridodecyloxybenzoic acid (general procedure for 3,4,5- trialkoxylbenzoic acids) Conclusion A mixture of methyl 3,4,5-tridodecyloxy benzoate (5.0 g, Systematic studies on a homologous series of compounds have 0.07 mol) and KOH (0.56 g, 0.10 mol) was refluxed in 100 ml allowed for a better understanding of the relationship between of THF–H2O (654, v/v) for 24 h and the solution extracted the molecular structures and mesomorphic properties.twice with dichloromethane (100 ml ). The CH2Cl2 layer was Mesomorphic data obtained in this work suggested that the collected and dried over MgSO4.The solution was concenmesophases might be thermodynamically destabilized due to trated to give a white solid, which was recrystallized from the presence of nitrogen electron lone pairs. Strong molecular THF–MeOH or acetone. Yield 92%. 1H NMR (CDCl3): d interactions in the mesophase could be partially overcome 0.86(t, CH3, 9H), 1.14–1.83(m, CH2, 60H), 4.00(t, OCH2, with surrounding by more or/and longer flexible chains. 6H), 7.26(s, C6H2, 2H). 13C NMR (CDCl3): d 14.00, 22.70, 26.22, 29.43, 29.77, 30.04, 31.95, 68.88, 73.36, 107.97, 126.00, 141.96, 152.57, 172.02. Experimental All chemicals were reagent grade from Aldrich and used 3,4-Ditetradecyloxybenzoic acid without further purification. THF was dried over sodium Yield 94%. 1H NMR (CDCl3): d 0.92 (t, CH3, 6H), 1.31(m, benzophenone ketyl, and pyridine was predried over KOH CH2, 44H), 1.83(m, CH2, 2H), 4.07(t, 4H, OCH2, 4H), pellets for prolonged periods and followed by fresh distillation 6.89(d, C6H3, 1H), 7.53(s, C6H3, 1H), 7.58(d, C6H3, 1H).from BaO before use. 1H and 13C NMR spectra were measured 13C NMR (CDCl3): d 13.91, 22.53, 25.90, 25.73, 29.14, 29.21, on a Bruker DRS-200 spectrometer in CDCl3 using TMS as 29.25, 29.41, 29.44, 29.49, 29.52, 29.58, 30.19, 31.77, 31.79, an internal standard.IR spectra were recorded on a Bio-Rad 69.00, 73.35, 116.4, 121.2, 148.0, 152.7, 172.0. FTS-155 instrument using polystyrene as a standard. DSC thermograms were obtained on a Perkin-Elmer DSC-7 instru- 4-Octadecanoxybenzoic acid ment and calibrated with a pure indium sample.All phase behaviors were determined at a scan rate of 10.0 °C min-1 White solid, yield 85%. 1H NMR (CDCl3): d 0.86(t, 3H, unless otherwise noted. Optical polarized microscopy was CH3), 1.23–1.83(m, CH2, 32H), 3.93(t, 2H, OCH2), 6.98(d, carried out on Nikkon MICROPHOT-FXA instrument with 2H, C6H4), 8.02(d, 2H, C6H4). 13C NMR (CDCl3): d 14.03, a Mettler FP90/FP82HT hot stage system.X-Ray powder 22.61, 25.91, 29.04, 29.29, 29.61, 31.85, 68.71, 114.09, 126.03, diVraction (XRD) studies were conducted on an INEL MPD- 129.69, 162.33, 171.82. diVractometer with a 2.0 kW Cu-Ka X-ray source equipped with an INEL CPS-120 position sensitive detector and a 3,4,5-Tridecyloxybenzoic acid chloride (general procedure for variable temperature capillary furnace with an accuracy of the synthesis of 3,4,5-trialkoxybenzoic acid chlorides) ±0.10 °C in the vicinity of the capillary tube (80 mm 3,4,5-Tridecyloxybenzoic acid (5.0 g, 0.0085 mol) dissolved in long×0.01 mm thick from Charles Supper Co).The detector dried THF (100 ml ) was added dropwise to a THF solution was calibrated using mica and silicon standards. EPR measureof fresh SOCl2 (1.24 ml, 0.017 mol ) at ice-bath temperature ments were taken with a EMX Bruker spectrometer in X-band under N2 atmosphere.The mixture was stirred, and gently and powder samples were placed into quartz tubes of 2.0 mm warmed to room temperature. The mixture was allowed to diameter. Methyl 3,4,5-trialkoxybenzoate esters, methyl 4- reflux for 4 h. The solution was concentrated to remove THF alkoxybenzoate esters and ethyl 3,4-dialkoxybenzoate esters and excess SOCl2. The milky paste was redissolved in 100 ml were prepared by literature procedures. of dried THF, and then the solution concentrated.This process was repeated several times to remove any residual SOCl2 Methyl 3,4,5-tridodecyloxybenzoate which would aVect the following reactions.The white solid thus obtained was directly used for the next reaction without White solid, yield 90%. 1H NMR (CDCl3): d 0.86(t, CH3, any further purification or recrystallization. 9H), 1.26–1.84(m, CH2, 60H), 3.88(s, OCH3, 3H), 4.03(t, OCH2, 6H), 7.25(s, C6H2, 2H). 13C NMR (CDCl3): d 14.18, 22.75, 26.14, 29.36, 29.45, 29.62, 29.71, 29.75, 29.39, 30.39, 3,4,5-Trioctadecanoxy-N-pyridin-2-ylbenzamide (general 32.00, 52.13, 69.22, 75.53, 105.02(C2,6), 124.69(C1), procedure for the synthesis of N-pyridin-2-ylbenzamide 142.01(C3,5), 152.83(C4), 166.89(CLO).derivatives) Freshly prepared 3,4,5-trioctadecanoxybenzoic acid chloride Ethyl 3,4-ditetradecyloxybenzoate (5.0 g, 5.29 mmol) was dissolved in dried pyridine (50 ml ) under nitrogen atmosphere, and to this solution 2-aminopyrid- White solid, yield 87%. 1H NMR (CDCl3): d 0.87(t, CH3, ine (0.50 g, 5.29 mmol) in pyridine (20 ml ) was added slowly 6H), 1.24–1.83(m, CH2, 51H), 3.97(t, J=8.19 Hz, OCH2, at room temperature.The mixture was stirred for 8 h, and 4H), 4.28(q, OCH2, 2H), 6.80(d, J=8.44 Hz, C6H3, 1H), then gently refluxed for 3 h. The solution was concentrated to 7.47(s, C6H3, 1H), 7.57(d, J=6.42 Hz, C6H3, 1H). 13C NMR half its volume, and left in a freezer overnight. The resulting (CDCl3): d 13.91, 14.21, 22.51, 25.84, 28.93, 29.21, 31.74, white solid was filtered oV, and recrystallized from THF– 60.48, 68.84, 69.13, 111.7(C6), 114.2(C2), 122.6(C5), methanol. Yield 65%. 1H NMR (CDCl3): d 0.85(t, CH3, 9H), 123.2(C1), 148.3(C4), 152.9(C3), 166.3(CLO). 1.14–1.83(m, CH2, 96H), 4.01(t, OCH2, 6H), 7.06(dd, C5H4N, 1H), 7.12(s, C6H2, 2H), 7.75(dd, C5H4N, 1H), Methyl 4-octadecanoxybenzoate 8.26(d, C5H4N, 1H), 8.38(d, C5H4N, 1H), 8.81(s, NH, 1H). 13C NMR (CDCl3): d 14.10, 22.06, 22.68, 29.36, 29.71, 30.32, White solid, yield 95%. 1H NMR (CDCl3): d 0.82(t, J=6.73 Hz, CH3, 3H), 1.24–1.84 (m, CH2, 32H), 3.82(s, 31.92, 69.35, 73.54, 105.77, 114.13, 119.83, 128.89, 138.53, 141.77, 147.77, 151.65, 153.23, 165.48. IR (thin film): 3488, OCH3, 3H), 3.93(t, J=7.31 Hz, OCH2, 2H), 6.84(d, J= 8.82 Hz, C6H4, 2H), 7.97(d, J=8.82 Hz, C6H4, 2H). 3413, 2929, 2842, 1655, 1636, 1619, 1578, 1566, 1538, 1504, 1470, 1431, 1383, 1343, 1309, 1219, 1125, 987, 776 cm-1. 13C NMR(CDCl3): d 14.04, 22.57, 25.93, 29.00, 29.14, 2382 J. Mater. Chem., 1998, 8(11), 2379–23833,4-Dioctadecanoxy-N-pyridin-2-yl-benzamide Anal.Calc. for C60H90N4O4Cu: C, 72.43; H, 9.12; N, 5.63. Found: C, 72.64; H, 9.22; N, 5.67%. White solid, yield 65.5%. 1H NMR (CDCl3): d 0.85(t, CH3, 6H), 1.23–1.81(m, CH2, 64H), 4.01(t, OCH2, 4H), 6.87(d, C6H3, 1H), 7.08(dd, C5H4N, 1H), 7.43(s, C6H3, 1H), 7.47(d, Acknowledgments C6H3, 1H), 7.74(dd, C5H4N, 1H), 8.27(d, C5H4N, 1H), We thank the National Science Council of Taiwan, ROC for 8.39(d, C5H4N, 1H), 8.81 (s, NH, 1H). 13C NMR (CDCl3): funding (NSC-88-2113-M-008-009) in generous support of d 13.93, 22.52, 25.84, 29.03, 29.23, 29.55, 31.76, 69.14, 102.02, this work. 112.54, 114.09, 119.04, 120.15, 126.25, 138.30, 147.43, 148.91, 151.75, 152.47, 165.28. References 4-Octadecanoxy-N-pyridin-2-ylbenzamide 1 (a) J.L. Serrano, in Metallomesogens; Synthesis, Properties, and White solid, yield 62%. 1H NMR (CDCl3): d 0.80(t, CH3, Applications, VCH, New York, 1996; (b) D. W. Bruce and 3H), 0.94–1.79(m, CH2, 32H), 3.91(t, OCH2, 2H), 6.91(d, D. O’Hare, Inorganic Materials, John Wiley & Sons, 1992, C6H4, 2H), 7.07(dd, C5H4N, 1H), 7.75(dd, C5H4N, 1H), pp. 407–490. 7.74(d, C6H4, 2H), 8.28(d, C5H4N, 1H), 8.39(d, C5H4N, 1H), 2 S.A. Hudson and P. M. Maitlis, Chem. Rev., 1993, 93, 861; 8.81(s, NH, 1H). 13C NMR (CDCl3): d 14.03, 22.61, 25.91, P. Espinet, M. A. Esteruelas, L. A. Oro, J. L. Serrano and E. Sola, Coord. Chem. Rev., 1992, 117, 215; P. Maitlis and A. M. Giroud- 29.04, 29.29, 29.61, 31.85, 68.17, 114.32, 112.08, 119.44, 126.03, Godquin, Angew. Chem., Int. Ed.Engl., 1991, 30, 375. 129.21, 138.44, 147.36, 151.87, 162.34, 165.35. 3 (a) C. Destrade, P. Foucher, H. Gasparoux, H. T. Nguyen, A. M. Levelut and J. Malthete, Mol. Cryst. Liq. Cryst., 1984, 106, Bis[3,4,5-trioctadecanoxy-N-pyridin-2-ylbenzamide]copper(II ) 121; (b) S. Chandrasekhar and G. S. Ranganath, Rep. Prog. Phys., (general procedure for the synthesis of copper complexes of N- 1990, 53, 57.pyridin-2-ylbenzamide derivatives) 4 (a) C. K. Lai, C. H. Tsai and Y. S. Pang, J. Mater. Chem., 1998, 8, 1355; (b) C. K. Lai, C. H. Chang and C. H. Tsai, J. Mater. Chem., 3,4,5-Trioctadecanoxy-N-pyridin-2-ylbenzamide (0.20 g, 1998, 8, 599; (c) C. K. Lai, F. G. Chen, Y. J. Ku, C. H. Tsai and 0.023 mmol) dissolved in THF (5.0 ml ) was added to a R. Lin, J. Chem.Soc., Dalton Trans., 1997, 4683; (d) C. K. Lai and solution of copper(II) perchlorate hexahydrate (0.042 g, F. J. Lin, J. Chem. Soc., Dalton Trans., 1997, 17; (e) C. K. Lai, M. Y. Lu and F. J. Lin, Liq. Cryst., 1997, 23, 313; ( f ) H. Zheng, 0.0115 mmol) in methanol (10 ml ). Upon addition a light C. K. Lai and T. M. Swager, Chem. Mater., 1995, 7, 2067; green solid started to suspend in solution, and the solution (g) C.K. Lai, A. G. Serrete and T. M. Swager, J. Am. Chem. Soc., was gently refluxed for 2 h. The green solid was filtered oV, 1992, 114, 7948. collected and recrystallized from CH2Cl2–MeOH. Yield 82%. 5 (a) S. T. Trzaska and T. M. Swager, Chem. Mater., 1998, 10, 438; IR (thin film): 2929, 2848, 1624, 1577, 1529, 1503, 1469, 1429, (b) H. Zheng, C.K. Lai and T. M. Swager, Chem. Mater., 1994, 6, 1341, 1240, 1119, 1051, 783, 729, 628 cm-1. Anal. Calc. for 101; (c) J. Barbera�, C. Cativiela, J. L. Serrano and M. M. Zurbano, C132H234N4O8Cu: C, 76.63; H, 11.40; N, 2.71. Found: C, Adv. Mater., 1991, 3, 602; (d) H. Zheng, C. K. Lai and T. M. Swager, Chem. Mater., 1994, 6, 101; (e) A. G. Serrette, C. K. Lai 76.71; H, 11.45; N, 2.75%. and T. M. Swager, Chem.Mater., 1994, 6, 2252. 6 (a) P. J. Alonso, M. Marcos, J. I. Martý�nez, V. M. Orera, Bis[3,4-dioctadecanoxy-N-pyridin-2-ylbenzamide]copper(II ) M. L. Sanjua�n and J. L. Serrano, Liq. Cryst., 1993, 13, 585; (b) M. P. Eastman, M. Horng, B. Freiha and K. W. Shew, Liq. Green solid, yield 87%. IR (thin film): 2929, 2862, 1664, 1637, Cryst., 1987, 2, 223; (c) M. Ghedini, S. Morrone, D. Gatteschi and 1570, 1516, 1483, 1119, 1055, 781, 728, 631 cm-1. Anal. Calc. C. Zanchini, Chem. Mater., 1991, 3, 752; (d) N. Hoshino, for C96H162N4O6Cu: C, 75.27; H, 10.66; N, 3.66. Found: C, A. Kodama, T. Shibuya, Y. Matsunaga and S. Miyajima, Inorg. 75.55; H, 10.68; N, 3.72%. Chem., 1991, 30, 3091; (e) E. Campillos, M. Marcos, J. L. Serrano, J. Barbera�, P. L. Alonso and J. I. Martý�nez, Chem. Mater., 1993, Bis[4-octadecanoxy-N-pyridin-2-ylbenzamide]copper(II ) 5, 1518. Green solid, yield 78%. IR (thin film): 2922, 2862, 1617, 1604, 1516, 1475, 1355, 1268, 1240, 1180, 1093, 1066, 783, 622 cm-1. Paper 8/06268D J. Mater. Chem., 1998, 8(11), 2379&ndash