J O U R N A L O F C H E M I S T R Y Materials Preparation, characterization and mesomorphic properties of nickel and copper complexes derived from N,N¾-bis[3-(3¾,4¾- dialkoxyphenyl )-3-oxopropenyl]ethylenediamine Chung K. Lai,* Yung-Shyen Pang and Chun-Hsien Tsai Department of Chemistry, National Central University, Chung-Li, Taiwan, ROC Received 14th May 1998, Accepted 24th September 1998 The preparation, characterization and mesomorphic properties of copper and nickel complexes derived from N,N¾- bis[3-(3¾,4¾-dialkoxyphenyl )-3-oxopropenyl ]ethylenediamine are reported.Liquid crystalline behavior for these structurally similar complexes was found to be strongly dependent both on the number of sidechains and metal centers incorporated. Nickel complexes with four or six alkoxy sidechains exhibited columnar phases.However, nickel complexes with two alkoxy sidechains and all copper complexes regardless the numbers of the sidechains were not liquid crystalline. The structure of the mesophases was confirmed as columnar hexagonal (Colh) by powder XRD diVraction. The data that the copper complexes have slightly lower isotropic temperatures than the analogous nickel complexes suggested that the lack of liquid crystallinity for the copper complexes may be attributed to weaker molecular interactions.The results also indicated that nickel complexes with four sidechains showed a wider range of mesophase temperature than complexes with six sidechains. molecular layers is extremely critical in the formation of Introduction columnar phases since the induction of the mesophase is Numerous metallomesogenic compounds with unique mainly controlled by a delicate balance of intermolecular geometries and molecular shapes have been generated by interactions.incorporation1 of a metal center or metal centers into organic Herein we report the preparation, characterization and moieties. In general the geometry of the complex is often mesomorphic properties of three series of copper and nickel determined by the metal center incorporated and the organic complex analogues derived from N,N¾-bis[3-(3¾,4¾-dialkoxychelating ligand, and it can vary from square-planar to tetra- phenyl )-3-oxopropenyl ]ethylenediamine.Of these, nickel comhedral structures for complexes2 with coordination numbers plexes 2 and 3 exhibited columnar hexagonal phases, and of four.Square-planar (i.e. Cu2+, Ni2 +, Pd2 +, Pt2 +, Zn2 +) copper complexes were not liquid crystalline. and square-pyramidal geometries (FeCl2+, VO2 +) generally give rise to liquid crystals, whereas tetrahedral geometries are often not mesomorphic. Some of these materials have been Results and discussion extensively studied as potential candidates in terms of appli- Synthesis cations and all the related physical properties may originate from the rich electronic configuration of the metal centers.The synthetic pathways to copper and nickel complexes 1, 2 Incorporation of a metal center can often induce the and 3 are summarized in Scheme 1. The preparation of 4- formation of mesophases by a non-mesogenic organic ligand, alkoxylacetophenones, 3,4-dialkoxyacetophenones and 3,4,5- and this diVerentiation in mesomorphic properties is generally trialkoxyacetophenones were via literature procedures.4 The attributed to the change of molecular shape and/or intermol- sodium salts of alkoxylphenyl-3-oxo-3-phenylpropionaldehyde ecular interaction.On the other hand the mesomorphic derivatives were obtained by the Claisen formylation5 reaction properties may be totally lost upon incorporation of a metal of the appropriate acetophenone, ethyl formate and sodium ion.metal dispersed in diethyl ether. The isolation of the neutral In previous studies3 we demonstrated the formation of forms of alkoxylphenyl-3-oxo-3-phenylpropionaldehydes was mesophases by use of a b-enaminoketonate framework as the not attempted owing to their relatively low thermal stability.core group in which the better planar core based on b- The ethylenediamine SchiV bases; N,N¾-bis[3-(3¾,4¾-dialkoxyenaminoketonato instead of b-diketonato structures was phenyl )-3-oxopropenyl ]ethylenediamines were obtained as applied to induce the mesophases. The separation between light yellow solids by reaction of the freshly prepared sodium salts with ethylenediamine in refluxing dried dichloromethane in high yields.The reaction9 of SchiV bases with copper(II ) acetate monohydrate or nickel(II) acetate tetrahydrate in refluxing THF–methanol produced the complexes. Recrystallization twice from ethyl acetate or THF–methanol gave yellow solids for the nickel complexes and green–gray solids for copper complexes.These SchiV base derivatives were characterized by 1H and 13C NMR spectroscopy. SchiV bases can potentially exist possibly in three diVerent keto–enol tautomeric6 forms; A, B and C (Fig. 1). The 1H NMR data in CDCl3, e.g., for 5 (n= 16) showed three characteristic peaks at d 5.64, 6.75 and 10.19, assigned to olefinic methine H (KCHLCK), aldehyde H (KCHLNK) and imine H (KCLNHK).In addition, the preference for the tautomeric A structure was also indicated by two O N RO X Y O N OR X Y H H M = Cu, Ni; R = (CH2) nH 1 X = Y = H 2 X = OR; Y = H 3 X = Y = OR M J. Mater. Chem., 1998, 8, 2605–2610 2605O O ONa RO OR X RO Y RO OH N RO X Y O HN RO X Y OH O RO OR RO OMe O RO OR RO O RO O HO O OR RO OR RO O N RO X Y O N RO X Y 4 X = Y = H 5 X = OR; Y = H 6 X = Y = OR b d g c e e e M = Cu, Ni 1 X = Y = H 2 X = OR; Y = H 3 X = Y = OR M f a Scheme 1 Reagents and conditions: a, KOH (2.0 equiv.), refluxing in THF–H2O (9/1), 12 h; b, CH3Li (1.1 equiv.), stirred in dried THF at 0 °C; then at RT, 12 h.c, CH3COCl (1.1 equiv.), AlCl3 (3.0 equiv.), stirred in CH2Cl2 at 0 °C, then at RT, 8 h; d, RBr (1.1 equiv.), K2CO3 (3.0 equiv.), refluxing in Me2CO, 18 h; e, ethyl formate (4.5 equiv.), Na (3.0 equiv.), stirred in Et2O at RT, 8 h; f, NH2(CH2)2NH2 (0.55 equiv.), CH3CO2H (3 drops), refluxing in CH2Cl2, 12 h; g, M(OAc)2 (1.1 equiv.); MLCu, Ni, refluxing in THF–CH3OH, 12 h.characterteristic peaks at d 189.63 and 153.73 in the 13C NMR spectrum. Copper (d9) compounds, which are paramagnetic, displayed only broad alkoxy signals in the 1H and 13C NMR spectra.However, the nickel complexes showed sharp signals, also indicating the diamagnetic configuration. Elemental analysis confirmed the purity of the complexes. Mesomorphic properties The liquid crystalline behavior for the metal complexes was studied by thermal analysis (DSC) and polarized optical microscopy.Nickel complexes exhibited columnar phases while copper complexes formed crystalline phases. Phase transitions and thermodynamic data for these metal complexes were summarized in Table 1. The nickel complexes 2 and 3 with four and six alkoxy sidechains exhibited enantiotropic liquid crystalline behavior, whereas complexes 1 with two sidechains were not liquid crystalline.This dependence of sidechain density has been commonly observed in other columnar phases.4a–c,7c Two transitions of crystal-to-columnar (KACol ) and columnar-to-isotropic (ColAI ) were typically observed in all nickel derivatives. The molecular shapes of these metal complex are roughly halfdisc, and the correlated columnar mesophases are formed by shape eVects and dative interaction between neighboring complexes.Two molecules rotated by 180° are stacked in an antiparallel organization7 within columns. O HN O HN H H OH N OH N H H OH N O HN H H H H H H H H keto (A) enol (B) keto-enol (C) DSC data showed that the crystal-to-mesophase transitions, Fig. 1 Three structures of keto-enol tautomeric forms for enaminoketone derivatives. for example, for nickel complexes 2, were observed in the 2606 J.Mater. Chem., 1998, 8, 2605–2610Table 1 Phase behaviora of metal complexes, 1, 2 and 3 n 1 Ni 8 K I ,bbb) 108.6 (40.0) 65.3 (41.3) 16 K I ,bbb) 113.5 (85.8) 98.0 (85.3) Cu 8 K I ,bbb) 105.3 (30.4) 54.1 (31.4) 16 K I ,bbb) 100.1 (73.9) 85.6 (88.1) 2 Ni 10 K I ,bbb) 110.0 (20.4) 105.7 (20.9) 12 K Colh I ,bbb) 57.7 (2.84) 54.4 (2.64) ,bbb) 108.5 (13.4) 105.9 (13.4) 14 K Colh I ,bbb) 62.9 (6.00) 58.8 (6.03) ,bbb) 105.6 (12.0) 100.1 (11.5) 16 K Colh I ,bbb) 66.8 (5.90) 59.3 (6.50) ,bbb) 100.5 (5.83) 88.9 (6.40) 18 K Colh I ,bbb) 73.4 (14.9) 63.5 (7.25) ,bbb) 102.1 (7.49) 93.1 (7.60) Cu 10 K I ,bbb) 93.9 (40.0) 60.1 (45.6) Fig. 2 Bar graph showing the phase behavior of the nickel complexes (2 and 3); n is the carbon number of the sidechains. 12 K I ,bbb) 89.6 (36.9) 75.7 (57.2) sidechains, and only a crystal-to-isotropic (KAI ) transition 16 K I ,bbb) 88.9 (34.1) 74.0 (34.0) was observed. Such drastic change in mesomorphic properties due to incorporation of diVerent metals has also been observed 3 Ni 14 K Colh I in other systems,1a and can be due to many factors. The lack ,bbb) 70.1 (3.55) 56.7 (3.71) ,bbb) 75.7 (5.45) 66.7 (5.16) of liquid crystallinity is generally believed to be attributed to 16 K Colh I weaker interaction between the copper complexes, and this ,bbb) 64.5 (1.60) 50.3 (1.54) ,bbb) 70.6 (2.13) 62.5 (2.90) suggestion was indicated by the fact that the clearing temperatures of the copper complexes were slightly lower than their Cu 14 K I ,bbb) 71.0 (16.5) 61.3 (16.5) nickel analogues.However, ca. 2–3 times larger enthalpies were observed for the crystal-to-isotropic transitions in the 16 K I copper relative to the nickel complexes. ,bbb) 44.8 (14.5) <20.0 Copper and nickel complexes of similar structures derived from imineketone derivatives with six alkoxy sidechains an Represents the number of carbons in the alkoxy chain. K=crystal phase; Colh=columnar hexagonal phase; I=isotropic.The transition reported by Swager’s group7b were found to form hexagonal temperatures (°C) and enthalpies (in parenthesis, kJ mol) are disordered columnar phases. Detailed comparison of DSC determined by DSC at a scan rate of 10.0 °Cmin-1. data for these two types of metal complexes showed that all imineketone-derived complexes had higher isotropic points and much larger enthalpies (2–4 times) of the crystal-toisotropic transitions than iminealdehyde-derived homologues.temperature range 58.0–73.0 °C on heating with the magnitude of transition enthalpies ranging from 2.84 to 14.9 kJ mol-1, These observations were rationalized in that the molecular interactions in columnar arrangements for imineketone- and isotropic points were all in the range 109.0–101.0 °C with a relatively large enthalpy (5.83–13.4 kJ mol-1).The relatively derived complexes should be much better or/and stronger owing to the presence of terminal methyl groups. On the large enthalpies indicated that the mesophases were in a highly ordered state.8 Similar thermal data were observed for nickel other hand molecular interactions in iminealdehyde-derived complexes are much weaker than in imineketone-derived com- complexes 3.Increasing the carbon length in the alkoxy sidechains decreased the clearing temperature, mainly due to plexes,9 and only little energy was needed to overcome such a small energy barrier as to pass into the liquid phase upon the greater dispersive forces associated with the longer alkoxy chains.The dependence of mesophase formation on the side- heating. These results also indicated that complexes without terminal tetrahedral methyl groups in iminealdehyde-derived chain density was also studied. Increasing the sidechain numbers of the nickel complexes from four (2) to six (3) increased materials preferred to form ordered hexagonal phases (Colho) over hexagonal disordered phases (Colhd) in imineketone- the melting temperatures and decreased the clearing temperatures. On the other hand the temperature range of the meso- derived complexes. The core–core distance was 3.68 A° (2, M= Cu, n=12), which is close to stacking distance in imineketone- phase was decreased from 28.7–51.0 °C for 2 to 5.6–6.1 °C for 3, as shown in Fig. 2. These complexes have clearing tempera- derived complexes (3.60 A° ).7b The assignment of a columnar hexagonal phase was tures relatively lower than most metallomesogenic complexes.Under a polarized optical microscope on very slow cooling confirmed by X-ray powder diVraction data. A summary of the diVraction peaks and lattice constants for the nickel from the isotropic point a mosaic texture was observed for a thin layer of samples between two glass plates, whereas, complexes 2 and 3 is given in Table 2. For example, as shown in Fig. 3, nickel complex 2 (n=12) displays a diVraction textures more like focal-conic with a large area of uniform homeotropic alignment was observed with thicker samples. pattern of a two-dimensional hexagonal lattice with one intense peak and two weak peaks at 35.09, 20.34 and 17.49 A° at 80 °C.Surprisingly, none of the copper complexes displayed any mesomorphic properties regardless of the numbers of the This type of diVraction pattern is characteristic of a hexagonal J. Mater. Chem., 1998, 8, 2605–2610 2607Table 2 Variable-temperature XRD diVraction data for nickel(II) for many disordered Colh systems. The temperature depencomplexes 2 and 3 dence of the lattice parameters in liquid crystals was also studied.We found that the low-angle reflection generally Lattice d-Spacing/ shifted to lower d-spacing at lower temperatures (i.e. d= spacing/ A° Miller 40.51 A° at 80 °C and d=41.01 A° at 104 °C for complex 2; n= Complex Mesophase A° obs. (calc.) indices 12). The hexagonal lattices are also well correlated with n increasing side chain lengths. 2 12 Colh 80 °C 40.51 35.09 (35.09) (100) 20.34 (20.26) (110) 17.49 (17.54) (200) Conclusion 4.47 (br) We have prepared three series of copper and nickel complexes 3.68 derived from N,N¾-bis[3-(3¾,4¾-dialkoxyphenyl )-3-oxoprop- Colh 104 °C 41.01 35.52 (35.52) (100) 20.55 (20.51) (110) enyl ]ethylenediamine.Liquid crystalline behavior was found 17.97 (17.76) (200) to be controlled by sidechain density and/or metal centres 4.53 (br) incorporated.Nickel complexes with four or six sidechains 3.54 exhibited columnar hexagonal phases, and complexes with 14 Colh 90 °C 42.78 37.05 (37.05) (100) four sidechains showed a much wider range of mesophase 21.83 (21.39) (110) than complexes with six sidechains. However, nickel complexes 18.64 (18.52) (200) 4.78 (br) with two sidechains and all copper complexes, regardless of 16 Colh 80 °C 49.32 42.71 (42.71) (100) the number of sidechains, were non-mesomorphic.This diVer- 24.57 (24.66) (110) ence might be attributed to the greater degree of molecular 21.23 (21.35) (200) interaction in nickel than in copper complexes. 4.63 (br) 3.89 18 Colh 57 °C 49.16 42.57 (42.57) (100) Experimental 24.80 (24.58) (110) 21.39 (21.29) (200) All chemicals and solvents were reagent grade from Aldrich 17.53 Chemical Co.and used without further purification. The 4.27 (br) solvents were dried by standard techniques. 1H and 13C NMR 3.96 spectra were measured on a Bruker DRS-200. DSC thermo- 3 14 Colh 60 °C 44.14 38.25 (38.25) (100) graphs were carried out on a Perkin-Elmer DSC-7 and cali- 19.16 (19.13) (200) 16.40 brated with a pure indium sample.All phase behaviors are 4.59 (br) determined at a scan rate of 10.0 °Cmin-1. Optical polarized 3.32 microscopy was carried out on Nikkon MICROPHOT-FXA 16 Colh 57 °C 46.57 40.33 (40.33) (100) with aMettler FP90/FP82HT hot stage system. X-Ray powder 23.30 (23.28) (110) diVraction (XRD) studies were performed on an INEL MPD- 20.25 (20.16) (200) diVractometer with a 2.0 kW Cu-Ka X-ray source equipped 4.45 (br) 3.70 with an INEL CPS-120 position sensitive detector and a variable temperature capillary furnace with an accuracy of ±0.10 °C in the vicinity of the capillary tube.The detector was calibrated using mica and silicon standards. The powder samples were charged in Lindemann capillary tubes (80 mm long and 0.01 mm thickness) from Charles Supper Co.with a inner diameter of 0.10 or 0.15 mm. The sample was heated above the isotropic temperature and allowed to stay at that temperature for 10 min. The sample was then cooled at a rate of 5.0 °Cmin-1 to the appropriate temperature and the diVraction data collected. Elemental analyses for carbon, hydrogen, and nitrogen were conducted on a Heraeus CHNO- Rapid elemental analyzer, and the results are listed in Table 3.The compounds of 1,2-dialkoxybenzenes, 4-alkoxyacetophenones, 3,4-dialkoxyacetophenones, methyl 3,4,5-trialkoxybenzoate esters, 3,4,5-trialkoxybenzoic acids and 3,4,5- trialkoxyacetophenones were prepared according to literature procedures.5,7 4-Hexadecyloxyacetophenone White crystals, yield 85%. 1H NMR (CDCl3): d 0.83(t, CH3, Fig. 3 Powder X-ray diVraction pattern of the columnar hexagonal 3H), 1.24–1.81(m, CH2, 28H), 2.45(s, COCH3, 3H), 3.93(t, phase (Colh) at 80°C for nickel complexes 2 (n=12). OCH2, 2H), 6.84(d, C6H4, 2H), 7.84(d, C6H4, 2H). 13C NMR (CDCl3): d 13.97, 22.56, 25.87, 26.07, 29.00, 29.25, columnar (Colh) phase with a d-spacing ratio of 1, (1/3)1/2 29.45, 31.76, 68.10(OCH2), 113.98(C3, C5), 129.99(C2, C6), and (1/4)1/2, corresponding to Miller indices (100), (110) and 130.39(C1), 163.01(C4), 196.37(CLO). (200), respectively.This corresponds to an intercolumnar distance (a parameter of the hexagonal lattice) of 40.51 A° . 1,2-Dihexadecyloxybenzene An additional weak halo peak at medium angle (d-spacing#4.47 A° ) was observed for most complexes.The White crystals, yield 92%. 1H NMR (CDCl3): d 0.83(t, CH3, 6H), 1.24–1.86(m, CH2, 56H), 3.94(t, OCH2, 4H), 6.86(s, presence of a distinct peak at ca. 3.68 A°indicated a relatively ordered mesophase which is consistent with DSC analysis of C6H4, 4H). 13C NMR (CDCl3): d 14.10, 22.68, 26.05, 29.36, 29.44, 29.70, 30.89, 31.92, 69.28, 114.13(C3, C6), 120.98(C4, large enthalpies for the columnar-to-isotropic transition.This peak reflects a more regular period within the columns than C5), 149.24(C1, C2). 2608 J. Mater. Chem., 1998, 8, 2605–2610Table 3 Elemental analysisa of metal complexes mixture turned clear and slightly acidic (pH paper). Ethylenediamine (0.15 g, 0.0025 mol) was added and the mix- Complex n C (%) H (%) ture was gently refluxed for 24 h.The solution was concentrated to give the crude product as a brown solid. Yellow 1 Cu 8 67.66 (67.74) 7.93 (7.89) needles were obtained after recrystallization from dichloro- 16 72.10 (72.39) 9.42 (9.58) Ni 8 68.28 (68.26) 8.00 (7.76) methane–methanol (253). Yield 78.0%, mp 98.0 °C. 1H NMR 16 72.58 (72.80) 9.65 (9.63) (CDCl3): d 0.85(t, CH3, 12H), 1.13–1.42(m, CH2, 104H), 2 Cu 10 71.72 (71.57) 9.87 (9.81) 1.80(t, CH2, 8H), 3.37(m, CNCH2, 4H), 3.98(t, OCH2, 4H), 12 72.92 (72.98) 9.93 (10.27) 4.00(t, OCH2, 4H), 5.64(d, COCH, 2H), 6.75(m, CHN, 2H), 14 74.08 (74.13) 10.76 (10.64) 6.83(d, C6H3, 2H), 7.36(d, C6H3, 2H), 7.45(s, C6H3, 16 75.18 (75.09) 10.92 (10.95) 2H), 10.19(m, CNH, 2H). 13C NMR (CDCl3): d 14.09, 22.67, 18 76.17 (75.90) 11.24 (11.22) Ni 10 71.72 (71.91) 9.87 (9.86) 26.00, 29.14, 29.35, 29.69, 31.91, 50.21(NCH2), 69.03(OCH2), 12 73.38 (73.29) 10.17 (10.31) 69.16(OCH2), 90.84(CHL), 112.03(C5¾), 112.17(C2¾), 14 74.57 (74.42) 10.78 (10.68) 120.78(C6¾), 132.25(C1¾), 148.72(C3¾), 151.91(C4¾), 16 75.15 (75.36) 10.96 (10.99) 153.73(CLN), 189.63(CLO).IR (thin film): 1636, 1590, 1545, 18 76.24 (76.16) 11.30 (11.25) 1516, 1464, 1374, 1335, 1269, 1219 cm-1. 3 Cu 14 75.57 (75.42) 11.54 (11.32) 16 76.27 (76.36) 11.58 (11.60) N,N¾-Bis[3-(4¾-hexadecanoxyphenyl )-3-oxopropenyl]ethyl- Ni 14 75.86 (75.65) 11.69 (11.35) 16 76.66 (76.57) 11.69 (11.63) enediamine. Light yellow solid, yield 84%, mp 172.0 °C. 1H NMR (CDCl3): d 0.85(t, CH3, 6H), 1.13–1.40(m, CH2, 52H), aCalculated values in parenthesis. 1.75(t, CH2, 8H), 3.34(m, CNCH2, 4H), 3.94(t, OCH2, 4H), 5.61(d, COCH, 2H), 6.72(m, CHN, 2H), 6.83(d, C6H4, 4H), 7.77(d, C6H4, 4H), 10.23(m, CNH, 2H). 13C NMR (CDCl3): 3,4-Dihexadecyloxyacetophenone d 14.05, 22.59, 25.94, 29.16, 29.27, 31.74, 50.12(NCH2), White crystals, yield 85%. 1H NMR (CDCl3): d 0.83(t, CH3, 68.03(OCH2), 90.71(CHL), 113.89(C3¾), 129.00(C2¾), 6H), 1.24–1.84(m, CH2, 56H), 2.52(s, CH3, 3H), 3.99(t, 131.89(C1¾), 153.76(C4¾), 161.63(CLN), 189.53(CLO).OCH2, 4H), 6.82(d, C6H3, 1H), 7.68(d, C6H3, 1H), 7.54(s, C6H3, 1H). 13C NMR (CDCl3): d 13.97, 22.56, 25.87, 26.07, N,N¾-Bis[3-(3¾,4¾,5¾-trihexadecyloxyphenyl )-3-oxopropenyl]- 29.00, 29.25, 29.45, 31.76, 68.10(OCH2), 111.49(C5), ethylenediamine. Light yellow solid, yield 80%, mp 49.0 °C. 1H 112.32(C2), 123.14(C6), 130.40(C1), 148.78(C3), 153.48(C4), NMR (CDCl3): d 0.85(t, CH3, 18H), 1.12–1.42(m, CH2, 197.73(CLO). 156H), 1.74(t, CH2, 12H), 3.39(m, CNCH2, 4H), 3.96(t, OCH2, 12H), 5.61(d, COCH, 2H), 6.77(m, CHN, 2H), 7.06(s, Methyl 3,4,5-trihexadecyloxybenzoate ester C6H4, 4H), 10.25(m, CNH, 2H). 13C NMR (CDCl3): d 14.10, 22.68, 26.09, 29.37, 29.71, 30.32, 31.91, 50.18(NCH2), White solid, yield 92%. 1H NMR (CDCl3): d 0.84(t, CH3, 69.15(OCH2), 73.46(OCH2), 91.02(LCH), 105.80(C2¾, C6¾), 9H), 1.26–1.80(m, CH2, 84H), 3.86(s, OCH3, 3H), 3.97(t, 134.37(C1¾), 141.15(C4¾), 152.82(C3¾, C5¾), 154.04(CLN), OCH2, 6H), 7.25(s, C6H2, 2H). 13C NMR (CDCl3): d 14.16, 189.80(CLO). 22.77, 26.14, 29.35, 29.45, 29.62, 29.72, 29.75, 29.81, 30.41, 32.01, 52.11, 69.22(OCH2), 75.50(OCH2), 108.03(C2, C6), Copper complexes of N,N¾-bis[3-(3¾,4¾-dihexadecanoxyphenyl )- 124.68(C1), 142.43(C4), 152.80(C3, C5), 166.91(COO). 3-oxopropenyl]ethylenediamine (general procedures for the copper complexes) 3,4,5-Trihexadecyloxybenzoic acid N,N¾-Bis[3-(3¾,4¾-dihexadecanoxyphenyl )-3-oxopropenyl ]- White solid, yield 83%. 1H NMR (CDCl3): d 0.83(t, CH3, ethylenediamine (0.50 g, 0.40 mmol) dissolved in dichloro- 9H), 1.24–1.84(m, CH2, 84H), 3.97(t, OCH2, 6H), 7.29(s, methane (5.0 ml ) was added to a hot methanol solution of C6H2, 2H). 13C NMR (CDCl3): d 14.10, 22.69, 26.09, 29.38, copper(II) acetate monohydrate (0.038 g, 0.20 mmol). Upon 29.72, 30.34, 31.93, 69.17(OCH2), 73.54(OCH2), 108.54(C2, addition a light brown solid began to appear, and the solution C6), 123.66(C1), 143.08(C4), 152.83(C3,C5), 171.87(COO).was gently refluxed for 6 h. The light brown solid was filtered oV, and recrystallized from dichloromethane–methanol to give 3,4,5-Trihexadecyloxyacetophenone a grey–green solid. Yield 72%. IR (thin film):1621, 1599, 1578, White solid, yield 82%. 1H NMR (CDCl3): d 0.82(t, CH3, 1495, 1466, 1437, 1401, 1383, 1327, 1271, 1231, 1202 cm-1. 9H), 1.24–1.86(m, CH2, 84H), 2.52(s, COCH3, 3H), 3.96(t, Anal. Calc. for C84H146O6N2Cu: C, 75.09; H, 10.95. Found: OCH2, 6H), 7.15(t, C6H2, 2H). 13C NMR (CDCl3): d 14.05, C, 75.18; H, 10.92%. 22.65, 26.1, 26.05, 26.30, 29.35, 29.69, 30.31, 31.68, 31.90, 69.29(OCH2), 73.47(OCH2), 107.11(C2, C6), 132.06(C1), Nickel complexes of N,N¾-bis[3-(3¾,4¾-dihexadecanoxyphenyl )- 3-oxopropenyl]ethylenediamine (general procedures for the 142.94(C4), 152.87(C3, C5), 196.92(CLO).nickel complexes) General procedures for the synthesis of SchiV bases N,N¾-Bis[3-(3¾,4¾-dihexadecanoxyphenyl )-3-oxopropenyl ]- ethylenediamine (0.50 g, 0.40 mmol) dissolved in dichloro- N,N¾-Bis[3-(3¾,4¾-dihexadecanoxyphenyl )-3-oxopropenyl]- ethylenediamine. A mixture of freshly cut sodium (0.34 g, methane (5.0 ml ) was added to a hot methanol solution of nickel(II ) acetate tetrahydrate (0.049 g, 0.20 mmol), and the 0.015 mol) suspended in dry diethyl ether (25.0 ml ) and 3,4- dihexadecyloxyacetophenone (3.0 g, 0.005 mol) was stirred for solution gently refluxed for 4 h.The solution was concentrated to dryness to give a brown solids. A yellow solid was obtained 0.5 h.Ethyl formate (1.85 g, 0.025 mol) was slowly added to the solution at room temperature and the mixture allowed to after recrystallization from ethyl acetate. Yield 73%. 1H NMR (CDCl3): d 0.88(t, CH3, 12H), 1.27–1.49(m, CH2, 104H), stir at room temperature under an N2 atmosphere for 18 h. The pale orange cloudy solution was carefully quenched with 1.84(m, CH2, 8H), 3.18(m, CNCH2, 4H), 4.00(t, OCH2, 4H), 5.63(d, COCH, 2H), 6.83(m, CHN, C6H3, 4H), 7.39(m, methanol to remove any excess sodium.The solution was concentrated to give a yellow solid, which was redissolved in C6H3, 4H). 13C NMR (CDCl3): d 14.07, 22.66, 26.03, 26.10, 29.25, 29.34, 29.35, 29.43, 29.51, 29.62, 29.65, 29.68, 29.71, dichloromethane (ca. 20.0 ml ). Then acetic acid was added slowly to neutralize the solution, and at this point the cloudy 31.90, 57.92, 69.03, 69.31, 92.02, 112.48, 112.62, 119.88, 130.33, J.Mater. Chem., 1998, 8, 2605–2610 2609C. K. Lai and T. M. Swager, Chem. Mater., 1994, 6, 2252; 148.42, 150.82, 156.14, 172.29. IR (thin film):1603, 1580, 1536, (e) C. K. Lai, C. H. Tsai and Y. S. Pang. J. Mater. Chem., 1998, 1511, 1493, 1443, 1381, 1362, 1329, 1273, 1241, 1206, 1164, 8, 1355. 1136 cm-1. Anal. Calc. for C84H146O6N2Ni: C, 75.36; H, 5 (a) W. Pyzuk, E. Go�recka and A. Krwczynski, Liq. Cryst., 1992, 10.99. Found: C, 75.15; H, 10.96%. 11, 797; (b) W. Pyzuk, E. Go�recka, A. Krwczynski and J. Przedmojski, Liq. Cryst., 1993, 14, 773; (c) E. Go� recka, W. Pyzuk, A. Krwczynski and J. Przedmojski, Liq. Cryst., 1993, Acknowledgements 14, 1837. 6 W. Pyzuk, A. Krowczynski and E. Go�recka, Liq. Cryst., 1991, We thank the National Science Council of Taiwan, ROC for 10, 593. funding (NSC-87–2113-M008–007) in generous support of 7 (a) S. T. Trzaska and T. M. Swager, Chem. Mater., 1998, 10, 438; this work. (b) H. Zheng, C. K. Lai and T. M. Swager, Chem. Mater., 1994, 6, 101; (c) C. K. Lai, A. G. Serrette and T.M. Swager, J. Am. Chem. Soc., 1992, 114, 7948. References 8 (a) K. E. Treacher, G. J. Clarkson and N. B. Mckeown, Liq. Cryst., 1995, 19, 887; (b) Chung K. Lai, Min-Yi Lu and Fun-Jane 1 (a) J. L. Serrano, in Metallomesogens; Synthesis, Properties, and Lin, Liq. Cryst., 1997, 23, 313; (c) A. Takada, N. I. T. Fukuda and Applications, VCH, New York, 1996; (b) D.W. Bruce and T. 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