J. MATER. CHEM., 1994, 4(8),1173-1180 Examination of the Structural Features necessary for Mesophase Formation with Aroylhydrazinato-nickel(i1) and -copper(ii) Complexes Mohammed N. Abser: Martin Bellwood," Christina M. Buckley," Michael C. Holmesb and Richard W. McCabe*a a Department of Chemistry, University of Central Lancashire, Preston, UK PR7 2HE Department of Physics and Astronomy, University of Central Lancashire, Preston, UK PRI 2HE N-Methylidene complexes and a series of N-alkylidene- and N-arylalkylidene-aroylhydrazinato-nickel(i1)and -copper(ii) complexes were synthesized in high yield and their mesomorphic nature studied. Only the N-methylidene coniplexes gave mesomorphic compounds as the larger N-alkylidene or N-aralkylidene groups probably prevented mesophase formation due to increased molecular broadening effects. The nickel(i1) complexes were found to be highly stable even in the isotropic phase and generally gave wide liquid-crystalline temperature ranges.This contrasted with the very narrow temperature ranges of the copper(ii) complexes, which rapidly decomposed in or just before attaining the isotropic phase. In a previous communication' the mesomorphic nature of some N-methylidene complexes was described. In order to explore further the formation of mesophases with these complexes, other N-methylidene complexes and a series of N-alkylidene- and N-arylalkylidene-aroylhydrazinato-nickel@) and -copper@) complexes were synthesized. Aroylhydrazones 1 and their parent hydrazines 2 form stable chelates with transition metals.2 The tuberculostatic activity of these compounds has been attributed to the forma- tion of stable chelates with transition metals present in the ell.^-^ Thus it seemed that such ligands might be used to form a new family of metal-containing liquid crystals, which, in contrast to many of the currently known metallome~ogens,~ would prove to be thermally stable.0 I1 R-C-NH-N=CH-R' 0 II R-C-NH-NHZ 1 2 N-Alkylidenearoylhydrazones 1 can coordinate to a divalent metal ion either via the enolic form (as in 3) or the ketonic form (as in 4 or 5).8-1' The square-planar complexes 3 and 4 would show the greatest promise as liquid crystals as the planar portion of such molecules would more easily align side by side than the non-planar octahedral complex 5.In the current study we present only the neutral compounds of type 3, although work has begun on ionic compounds 4. 12+ II CI 3 4 5 The tendency of the ligands 1 to react with nickel@) in the enolic form 6, to give complexes 3 (M =Ni), becomes greater as the conjugating ability of the R group in the hydrazine residue increases.12 Thus, aryl substituents favour the enolic tautomer of such ligands:I3 0 OH II I R-C-NH-N< R-C=N-N< keto 7 end 6 Furthermore, the coordinating ability of the counterion to the metal determines whether the octahedral or square-planar complex is formed.2 For instance, aroylhydrazones react with nickel(i1) acetate yielding the corresponding bis(aroy1h ydrazi- nato)nickel(u) complexes 3 (M =Ni), with the deprotonation of the secondary imino hydrogen; whereas with nrckel(I1) chloride it gives dichlorobis(aroylhydrazinato)nickd(Ir) 5 (M =Ni).The octahedral dichlorobis(aroy1hydrazone) nickel(i1) 5 (M =Ni) complexes, however, can undergo dehalo- pronation with alcoholic potassium hydroxide to give the square-planar neutral complexes. With these facts in mind several types of complexes 8-1 1, with differing arrangements of substituents (mode of molecular elongation), were synthe- sized. The n-dodecyloxy group was chosen as it should be sufficiently long to allow mesophases to form. The first complex targeted as a possible metalloniesogen was bis [N-( 4'-n-dodecyloxybenzylidene) benzoylhydra zinato] nickel(I1) 8 and was synthesized by following the reactions in Scheme 1.Reaction of benzamide with hydrazine hydrate, by thc litera- ture method,14 gave the benzoyl hydrazine 13 as a white solid. A 'Williamson ether' type reaction between p-hydrox! benzal- dehyde and 1-bromododecane in the presence of sodium hydroxide in ethanol gave the p-dodecyloxybenzaldeliyde 14 as a low-melting yellow solid together with the elimination product dodec- 1-ene. The alkene by-product was readily separ- ated by distillation under reduced pressure. The benzoy l hydra-zine 13 reacted with the aldehyde 14 in refluxing ethanol to give the benzoylhydrazone 15 as a white solid. Reaction of the hydrazone 15 with nickel@) acetate, again in refluxing zthanol, afforded the complex bis [N-(4'-n-dodecyloxybenzylidc~1e)ben-zoylhydrazinato] nickel@) 8 as an orange-yellow solid Note that although 8 can exist as one of three isclmers 8, 16, 17, 'H NMR spectroscopy shows only one methylene resonance at 6 7.18.This excludes the asymmetric structure 17 which should show two such resonances. 3D molecular modelling (Chem3D plus on the Apple Macintosh1 of the remaining symmetrical structures 8 and 17 shows that 8 would be more planar and sterically less hindered than 17, which suggests that the formation of the more conjugated isomer 8 would be preferred. On these grounds we propose an (E,E)-configuration for 8. 8 was examined under a hot-stage polarising microscope but unfortunately it was found to melt at 173-174 "Cwithout forming a mesophase.Since 8 was shown to be non-mesomorphic, an attempt was made to change the mode of molecular e1ong;ition. It was thought that the molecular lengthening along the axis of J. MATER. CHEM., 1994, VOL. 4 0 0 R = n -alkyl 10 11 12 0!-NH2 i"ref lux H-EGOH t C12HsBr 13 14 reflux1 EtoH 15 Scheme 1 Synthesis of 8 J. MATER. CHEM., 1994, VOL. 4 the 'benzoyl' benzene ring, as in 9, would result in a more linear molecule and might enhance the possibility of forming a mesophase. The complex, bis [N-benzylidene( 4'-n-dodecyloxy) benzoyl- hydrazinato] nickel(I1) 9, was synthesized following the route shown in Scheme 2. Ethyl p-hydroxybenzoate reacted under reflux in ethanol with 1-bromododecane in the presence of potassium hydroxide to give ethyl p-dodecyloxybenzoate 18 (R =C12H25), as a white low-melting crystalline solid, which on treatment with hydra~ine,'~ gave the p-dodecyloxy- benzoylhydrazine 19 (R =C12H25) as a white solid.Hydrazine 19 (R =C12H25) was then converted to the hydrazone 20 (R' = C12H25) by reaction with benzaldehyde in refluxing ethanol. Subsequent reaction of the hydrazone 20 (R' =C12H25) with alcoholic nickel@) acetate gave 9 as an orange-yellow solid. Again, unfortunately when observed under the hot-stage polarising microscope 9 showed a sharp transition from crystal to isotropic liquid at 161-162 "C without forming a mesophase. As it was evident from the melting behaviour of the hydrazinatonickel(I1) complexes 8 and 9 that the elongation along either 'end' of the molecule, i.e.via the benzoyl or benzylidene rings, does not confer the proper geometric requirements for the complex to be mesomorphic, it was decided to put a long hydrocarbon chain at both the benzoyl and benzylidene ends of the system on the assumption that the molecular elongation in both directions might introduce some mesomorphic properties (possibly discotic) into the system. With this in mind we synthesized the ligand 21 from aldehyde 14 and acylhydrazine 19 (R =C12H25), which on reac- tion with nickel(I1) acetate gave the orange crystalline complex, bis [(N-(n-dodecylox y) benzylidene) (n-dodecylox y) benzoylhy-drazinato] nickel(I1) 10.21 10 was found to melt at 77-78 "C, again without forming a mesophase. The non-mesomorphic character of this com-pound was also evidenced by differential scanning calorimetric (DSC) analysis, which showed a single transition at 77.77 "C (AH=51.5 kJ mol-', AS=147 J mol-' K-') corresponding to its transition to isotropic liquid. EtO-FOOH + RBr KOH zG1 1819 Scheme 2 Synthesis of 9 1175 From a thorough re-examination of the structure of the hydrazinatonickel(11) complexes described so far, it is apparent that the presence of a phenyl or a substituted phenyl ring in the azomethine (N-N=C) moiety, considerably broadens the molecular width. Moreover, owing to the proximitv to the central dihydrazinato ring, the benzylidene phenyl riiig is not coplanar with the central hydrazinatonickel ring.rhis broadening of the molecular width and the non-coplarity of the benzylidene ring is probably the underlying reason for non-mesomorphic behaviour of the complexes 8-10. I'hus it was realised that to impart the desired mesomorphic properties to the system, the substituent at the azomethine moiety should have the smallest possible size to minimisc the molecular broadening effect. A simple methylidene group was thought to be appropriate for this purpose. Accordingly the complex bis [N-methylidene-( 4'-n-dodecyloxy) benzoylhydraz- inato]nickel(~r)11 (R =C12H25) was synthesized by reaction of nickel(i1) acetate with N-methylidene( 4'-n-dodecyloxy) ben- zoylhydrazone 22 (R =C12H25).The latter was generated in situ by reaction of n-dodecyloxybenzoylhydrazine 19 (R =C12H25) with formaldehyde. h 22 11 (R =C12H25) was an orange-yellow microcrystalline solid, obtained by the usual work-up followed by re-crystallization from dichloromethane. A notable feature of the 'H NMR spectrum of this material is the unusually large coupling constant (J= 10.9Hz) shown by the two separate methylidene proton doublets at 6 7.05 and 6.47. The other features of the 'H NMR spectrum were as expected and are fully consistent with the structure 11 (R=C12H25)-On examination under the hot-stage microscope 11 iR= C12H25) showed a crystal to smectic C transition at 126.2"C which, on further heating, melted to the isotropic liquid at 164-165°C.On cooling the sample from the isotropic liquid, the smectic phase reappeared at 164 "C, but supercoolirig to 112-1 14 "C occurred before the solid crystalline phase reformed. After having established that the N-methylidenenickel(I1) complex 11 (R =C12H2,) does indeed show mesomorphic behaviour, it was of interest to study the effects of vari'ition of the alkyl chain length and the central metal atom to see what impact such changes had on the mesophase behaviour of these complexes. We synthesized seven homologues of 11 with different alkyl chain lengths (C4, c6, C8, Cl0, C14, CZ0 and C22). These complexes were prepared by a route similar to that employed for complex 11 (R =C12H25). The complexes 11 were obtained as crystalline orange solids and they all formed mesophases. Polarising microscop! and DSC experiments (Fig.1 and Table 1)were used to determine the phase change temperatures of the complexes 11, but the complex 11 (R=C,H,) was unstable and DSC data were not obtained. The complexes 11 (R =C4H9) and (R =C6H13) showed only nematic mesophases, whilst 11 (R =C,H,,) and (R =C1,H2,) showed both nematic and smectic C mesophases. The rernain- ing complexes showed only smectic C mesophases. The mesophases were identified by a combination of polarising microscopy and X-ray diffraction studies, both in our labora- tories and at the SRS facility at Daresbury. Polarising microscopy showed characteristic 'soft' schlieren textures for the nematic phases and a sharper more clearly defined schlieren texture with the smectic C mesophases.Typical textures given 1176 1802oiI 140-120-I 4 2 6 10 14 18 22 no. of carbons in alkyl chains Fig. 1 Transition temperatures of the bis [N-methylidene-(4'-n-alkyl-oxy) benzoylhydrazinato] nickel@) complexes, 11, observed by polaris- ing microscopy: 0,K+N; 0, K,+K2; 0, K-S,; A,K2-+S,; a,Sc+N; +, N+I; 0,Sc+I Table 1 DSC data for the bis [N-methylidene( 4'-n-alkyloxy) benzoyl- hydrazinatol-nickel(11) complexes 11 R phase change T/"C AH/kJmol-' AS1 J mol-' K-l 159.12 14.71 34.03 160.74 15.28 35.22 184.42 0.38 0.83 149.21 70.61 167.18 164.54 0.31 0.72 174.60 1.65 3.70 141.41 107.33 258.91 166.79 0.93 2.12 182.34 1.27 2.78 135.22 81.64 199.92 123.48 21.22 53.50 125.47 54.04 135.57 156.71 3.30 7.67 125.32 56.61 142.07 135.32 69.85 171.00 154.80 8.03 18.77 132.40 158.00 389.58 142.33 12.14 29.21 101.20 -25.73 -68.74 123.29 127.48 321.56 130.33 6.17 15.29 106.42 -7.87 -20.72 a Transitions too close to separate.Second heating cycle. 'Cooling cycle. under the polarising microscope by the nematic and smectic phases of these compounds are shown in Plates 1 and 2. X-Ray diffraction showed the classical diffuse arcs either side of the beam for the nematic mesophases, whilst the smectic C phases showed diffuse arcs from intralamellar scattering and Bragg peaks from interlamellar (do) scattering.Selected interlayer spacings, c, for the smectic C phases of these complexes are given in Table 2. All of the complexes showed extensive supercooling, the C,, Clo and C1,complexes showed a crystal to less ordered crystal transition before the mesophase was obtained, whilst J. MATER. CHEM., 1994, VOL. 4 the Czo and C,, complexes also showed a disordered to ordered crystal transition on supercooling. When these com- plexes were cooled the less ordered crystalline phase was obtained and in the case of 11 (R=C,,H,,) only, the K2-+S, transition decreased (from 141 to 135 "C) in subsequent heat- ing cycles. The more ordered crystalline phase K, could be recovered by recrystallising the less ordered material IS2.The ordered crystalline material is probably a kinetically formed crystalline form, whilst the other is the thermodynamically more stable form.It had become evident from the melting behaviour of the benzoylhydrazinatonickel(11) complexes 8-1 0 that a substitu-ent at the azomethine moiety leads to excessive broadening of the system which eliminates the mesomorphic properties of the complexes. However, it was felt that it would be worthwhile examining a complex with a methyl substituent on the azomethine moiety, which, although it is more gluobu- lar than a phenyl ring, might be tolerated by the system without preventing mesophase formation. Thus we obtained the orange crystalline complex bis [N-ethylidene( 4'-n-dode- cyloxy) benzoylhydrazinato] nickel(r1) 12 by a similar synthetic route to that used for complexes 11, i.e.by replacing the original formaldehyde with acetaldehyde. Once again 12 was found to be formed exclusively as only one of the three possible isomers, as evidenced by its 'H NMR spectrum showing only one doublet for the ethylidene CH, protons at 6 2.28 (J= 5.6 Hz). Although the methine proton (=CgCH,) should resonate as a quartet in the 'aromatic region' (by analogy with the benzylidene deriva- tives), the methine proton signal in the complex accidentally coincides with one of the doublets for the phenyl ring protons at 6 6.7-6.8 (total integration of 6 protons). Thus the splitting pattern for the methine proton could not be seen. The rest of the 'H NMR spectrum was consistent with the expected structure.On the basis of these 'H NMR data together with 3D modelling studies as before, we again assigned the (E,E)-configuration to 12. 12 was found to melt at 153-154.5 "C, again without forming a mesophase. Several copper analogues 23 of the mesomorphic nickel(r1) complexes 11 were synthesized in order to determine the impact of the change in central metal atom on the mesophase behaviour of the system. The copper complexes 23 were obtained as brown solids by replacing nickel(r1) acetate by copper(I1) acetate in the normal synthetic route. As expected, these complexes are paramagnetic and because of this para- magnetism the 'H NMR' signals of these complexes are so distorted that they provide little information regarding the structural characterisation of the complexes.In fact, the 'H NMR spectrum of these complexes shows no signal at all around the usual aromatic region as the protons for this region are close to the paramagnetic central metal atom; however, in the upfield region there are resonance signals characteristic of a long alkoxy hydrocarbon chain, although again the signals were too broad to see the splitting pattern of these signals. 23 Observation of the CI2complex 23 (R=C12H25) under the polarising microscope showed the characteristic changes in J. MATER. CHEM., 1994. VOL. 4 Plate 1 Schlieren texture of the nematic phase of 11 (R=OC,H,,) (x5 magnification) Plate 2 Schlieren texture of the S, phase of 11 (R=OC,H,), optical texture which accompanied mesophase formation at 139-140 C.The type of mesophase formed has not yet been identified, however, as unfortunately, the complex proved to be too unstable to perform either XRD or DSC experiments on. On the hot-stage polarising microscope the complex was seen to decompose to a glassy product at ca. 147°C before entering the isotropic phase. The C,, analogue 23 (R= 138 C, on cooling from the isotropic phase (x5 magnification) C,,H,,) showed parallel behaviour, beginning at the eievated temperature range of 150-152'C. These mesogenic copper(r1) complexes have similarities in shape to the copper(rr) /J-diketonate complexes, described by Ohta et al.,16.17which showed multiple melting behaviour.Modifications of the secondary side-chain, similar to those carried out in our work, of the basic copper(1r) P-dikctonate Table 2 Selected interlayer spacing data for the smectic C phases of the bis[N-methylidene (4'-n-alkyloxy) benzoylhydrazinato] nickel (n) complexes 11 R interlayer spacing, c/A T/"C 34.0 152 39.5 144 38.6 157 37.9 163 40.0 145 40.5 150 37.0 154 44.0 140 46.2 132 51.4 122 49.4 126 49.2 128 structure have produced several series of liquid-crystalline materials. Several of these complexes give liquid-crystalline phases; i.e. discotic, nematic and in some cases smectic A and smectic C mesophases have been Many of these complexes apparently oxidise when they are heated in air, thus the thermal instability of our copper(11) complexes is not too unexpected.l9 These promising compounds need careful re-examination. In conclusion, we have found that nickel@) and copper(I1) complexes with N-methylidenearoylhydrazinato ligands are mesogens, whilst other alkylidene-and aralkylidene-substituted ligands failed to form mesophases. The nickel(r1) complexes proved to be thermally stable [except for the high-melting complex 11 (R =C,H,)] and to have fairly wide liquid-crystalline ranges, whereas the copper(11) complexes decomposed soon after entering the mesophase. Experimental General All reagents were used as purchased. Commercially obtained ethanol and methanol were used without further purification; all other solvents were dried with an appropriate drying agent and distilled under nitrogen.The 'H NMR spectra were obtained on Hitachi R1200 (60 MHz) and Bruker WM250 (250 MHz) spectrometers. The FTIR spectra were recorded using a Mattson Polaris Icon Spectrometer and the GC-MS were obtained on a Perkin-Elmer 8500 Gas Chromatograph with an ITD Ion Trap Detector. Microanalyses were carried out as a service by the University of Manchester. Melting points were found using a Gallenkamp melting-point appar- atus or a Vickers microscope fitted with crossed polarisers and a Linkam PR600 hot stage and are uncorrected. X-Ray diffraction studies were carried out using a heated pinhole camera connected to a Hiltonbrooks X-ray generator and a Digital Imaging Systems DIS 3000 area detector.Thin-layer chromatography (TLC) was carried out using Kieselgel 60 F254 (from Merck) of thickness 0.20 mm (analytical). For preparative purposes spinning plates of Kieselgel 60 G (Chromatotron) of thickness 2 mm were used. Benzoylhydrazine 13 The benzoylhydrazine 13 was synthesized by the general literature method.I4 A mixture of benzamide (12.1 g, 0.1 mol) and hydrazine hydrate (5 g, 0.1 mol) was heated under reflux in water (40 cm3) for 3 days. When the mixture was cooled to room temperature a yellow-white solid separated out and was filtered off under suction, washed with cold ethanol (20 cm3) J. MATER. CHEM., 1994, VOL. and ether (20 cm3) and finally recrystallised from boilini, ethanol to give white crystals of the pure 13 (log, 74%) mp 112°C (lit.', 112.5"C); v,,, (CH,Cl,)/cm-': 3440, 333(1 (N-H), 3000-30230 (aromatic C-H), 1670 (amide I), 1624 (amide 11), 1578 and 1500 (aromatic C=C), 1470 (s), 1290 (m) 1100 (w), 940 (m), 660 (w); 6, (CDCl,, 250 MHz): 8.05 (1 H br s, NH-NH,), 7.72-7.75 (2 H, m, C6H5), 7.25-7.52(3 H, m C,H,), 3.66 (2 H, br s, NHNH,).-4Dodecyloxybenzaldehyde 14 Sodium hydroxide (6 g, 150 mmol) was added in portions to a refluxing ethanolic solution (150 cm3) of 4-hydroxy-benzaldehyde (12 g, 98 mmol) and l-bromododecane (24 g.96.4 mmol). After a further 10 h under reflux the mixture was cooled to room temperature and neutralised to litmus with dilute hydrochloric acid, extracted with ether (5 x 30 cm3). dried over Na2S0, and the solvent removed in uucuo to give a yellow oil. Distillation under reduced pressure gave a colourless liquid at 118-120°C at ca.4 mmHg, which proved to be dodec-1-ene. The residual oil was dissolved in petroleum ether (bp 60-80 "C) and left in the refrigerator overnight when a yellow solid separated out. This solid (12 g, 42%) was filtered off under suction, using cool conditions, and dried under high vacuum. The compound melted below ca. 3OCC, 6H (CDCl,, 250 MHz): 9.86 (1 H,s, CHO), 7.82 (2 H,d, J 8.25, C6H4) 6.99 (2 H, d, J 8.25, C6H4)74.03 (2 H, d, J, 6.5, OCH,CH,), 1.77 (2 H, m, OCH,CH,CH,), 1.2-1.4 [lS H, m. OCH2CH2(C~,),CH,], 0.88 (3 H, t, J 6.5, CF,). N-(4-n-Dodecyloxy) benzylidene-N-benzoylhydrazine 15 A suspension of 13 (0.68 g, 5mmol) and 4-n-dodecyloxybenzal- dehyde (1.45 g, 5 mmol) in ethanol (25 cm3) was heated under reflux for ca.1 h. The reaction mixture was cooled to room temperature and the yellowish solid product was collected by filtration under suction. Recrystallisation from chloroform gave 15 as a white crystalline solid (1.6 g, 78%), mp 143-145 "C; vmax (CH,Cl,)/cm-': 3350, 3300 (N-H), 3020 (aromatic C-H), 2920,2860 (aliphatic C-H), 1680 (amide I), 1604 (amide 11), 15746, 1505 (aromatic C-C). bis [4-n-Dodecyloxybenzylidenebenzoylhydrazinato]nickel(II ) 8 An ethanolic solution of nickel@) acetate (0.12 g, 0.84 mmol) was added to a refluxing solution of 15 (0.4g, 1.0mmol) in ethanol (25 cm3) and heating continued for a further 30 min. After cooling the mixture to room temperature the orange- yellow solid was filtered off, washed with ethanol (50 cm3), water (100 cm3) and finally with hot methanol until the filtrate was clear.The solid was dried under suction and recrystallised from chloroform to give 8 as an orange-yellow solid from a deep orange-red solution (0.30 g, 70°h), mp 173-174 "C. (Found: C, 71.2; H, 8.4; N, 6.3%. C,,H,,,N4O4Ni requires: C, 71.5; H, 8.1; N, 6.4%), 6H (CDCl,, 250 MHz): 8.33 (4 H, d, J 8.9, C&4), 7.98 (4H, m, C6H5), 7.35, 7.49 (6 H, m, C6Hs), 7.19 (2 H, s,N=CH), 6.98 (4H, d,J 8.9, C6H4), 4.04 (4 H, t, J 6.5, OCH,), 1.7-1.8 (4 H, m, OCH,CH,CH,), 1.15-1.6 [36 H, m, ~CH,CH,(CH,),CH,],, 0.8876 H, t, J 6.5 Hz, CH,); dC (CDCl,, 250 MHz): 175.5, 161.8, 152.8, 135.0, 130.7, 130.6, 128.6, 128.0, 122.8, 114.3, 68.2, 31.2, 29.63, 29.58, 29.4, 29.3, 29.1, 26.0, 22.7, 14.1.Ethyl 4-n-Alkyloxybenzoates 18 Potassium hydroxide (10 g, 0.18 mol) was added in portions to a refluxing ethanolic solution (200cm3) of ethyl 4-hydroxybenzoate (16.6 g, 0.1 mol) and the l-bromoalkane (0.1 mol). After heating the mixture under reflux for a further J. MATER. CHEM., 1994, VOL. 4 150 min the reaction mixture was cooled to room temperature neutralised (litmus) with dilute hydrochloric acid, extracted with ether (4 x 75 cm3), dried (Na,SO,) and evaporated in vacuo. The residual mass on treatment with petroleum ether (60-80 "C) (50 cm3) gave a small amount of white solid which was filtered off.The filtrate was evaporated in U~CUOand crystallised from petroleum ether (60-80 "C)-ether (ca. 10%) to give the title compounds as white crystalline solids which were filtered offunder cold conditions as many of them melted near room temperature. The following ethyl 4-n-alkyloxybenzoates 18 were prepared by the above method. Ethyl 4-n-butyloxybenzoate 18 (R =C4H9) (15.76 g, 71 %); vmaX (Nujol)/cm-': 2959, 2932, 2872 (aliphatic C-H), 1722 (C=O), 1611, 1575, 1500 (aromatic C=C), 1454 (s), 1488 (w), 1367 (s), 1308 (w), 1275 (s), 1178 (s), 1107 (s), 1023 (s), 845 (s), 772 (s), 703 (s); 6, (CDCl,, 250 MHz): 7.96 (2 H, d, J 9, C,H4), 6.86 (2 H,d,J 9, C6H4), 4.31 (2 H,q,J 7.2, OCH,CH,), 3.95 (2 H, t, J 6.6, OCH,CH,), 1.74 (2 H, m, OCH,CB,CH,), 1.37 [5 H, m, O(CH,),(CH,)CH, and OCH,CH,], 0.95 [3 H, t, J 6.5, 0(CH2 ),Cg 3 1 Ethyl 4-n-Hexyloxybenzoate 18 (R =C6H1,) (20 g, 80%).Ethyl 4-n-Octyloxybenzoate 18 (R =C,H,,) (24.97 g, 69%). Ethyl 4-n-Decyloxybenzoate 18 (R =C,,H,,) as low-melting white solid (22 g, 72%). Ethyl 4-n-Dodecyloxybenzoate 18 (R =C12H25) (25 g, 75%). Ethyl 4-n-Tetradecyloxybenzoate18 (R =C14H29) (24.25 g, 67%); mp 35.4-36.3 "C. Ethyl 4-n-Eicosyloxybenzoate 18 (R =C20H41) (18.69 g, 42%); mp 75.4-76.2 "C. Ethyl 4-n-Docosyloxybenzoate 18 (R =C22H45) (18.4 g, 39%); mp 60.6-41 "C. 4-n-Alkyloxybenzoylhydrazines 19 The hydrazines 19 were synthesized by following a general literature method.', A mixture of 18 (3 mmol) and hydrazine hydrate (1g, 20 mmol) was heated under reflux in ethanol (20 cm3) for 24 h.On removal of the solvent in uacuo, the residual solid was washed with water and recrystallised from ethanol (short chains) or chloroform (longer chains) to give the compounds 19 as white solids. The following 4-n-alkyloxybenzoylhydrazines19 were pre- pared by the above method. 4-n-Butyloxybenzoylhydrazine19 (R =C4H9) (0.47 g, 75%), mp 91.8 "C; vmax (Nujol)/cm-': 2948, 2919, 2855, (aliphatic C-H), 1720 (C=O), 1600, 1575, 1500 (aromatic C=C), 1451 (s). 1377 (s), 1316 (w), 1277 (s), 1255 (s), 1159 (s), 1018 (s), 845 (s), 721 (s); hH (CDCl,, 250 MHz): 8.06 (2 H, d, J 8.8, C,H,), 7.3 (1H, b, overlapped by solvent peak CHCl,, NHNH,), 6.95 (2 H, d, J 8.8, C6H4), 4.05 (2 H, t, J 6.5, OCH,CH,), 3.05-3.7 (2 H, b, NHNH,), 1.82 (2H, m, OCH,CH ,CH,), 1.28, [2 H, m, OCH,CH,(CEJ,)CH,), 0.90 (3 H, t, J6.25, CH,].4-n-Hexyloxybenzoylhydrazine 19 (R =C6H13) (0.53 g, 75%); mp 97-98 "C. 4-n-Octyloxybenzoylhydrazine 19 (R =CsH17) (0.6 g, 74%), mp 73.4"C. 4'-n-Decyloxybenzoylhydrazine 19 (R =C10H21) (0.76 g, 74%); mp 93-94°C. 4-n-Dodecyloxybenzoylhydrazine 19 (R =C,,H,,) (0.8 g, 84%); mp 92-94°C. 4-n-Tetradecyloxybenzoylhydrazine19 (R =C14H29) (0.64 g, 72%); mp 854°C. 4-n-Eicosyloxybenzoylhydrazine 19 (R =C2,H,,) (0.46 g, 68%); mp 118 "C. (Found: C, 75.7; H, 10.9; N, 6.5%; C&,8N@2 requires: C, 74.95; H, 11.18; N, 6.47%). 1179 4-n-Docosyloxybenzoylhydrazine 19 (R =C22H45) (0.5 g, 72%); mp 116.4 "C.N-Benzylidene-N-( 4-n-dodecyloxy) benzoylhydrazine 20 This was synthesized using a similar method to that used for N-(4'-n-dodecyloxy)benzylidenebenzoylhydrazine 15. Reaction of 19 (R= C12H25) (0.64 g, 2 mmol) with benzal- dehyde (0.21 g, 2 mmol) in refluxing ethanol (20 cm3) gave 20 as a white solid on recrystallisation from chloroform; (0.7 g, 86%); mp 136-137 "C; v,,, (CH,Cl,)/cm-l: 3355,3300 (NH), 2920, 2845 (aliphatic C-H), 1676 (amide I), 1604, 1572, 1500 (aromatic C=C). bis [N-Benzylidene (4-n-dodecylox y)benzoylhydrazinatril-nickel(r1) 9 This complex was synthesized using a similar method to that used for 8. Treatment of 20 (0.4 g, 0.98 mmol) with nickel(r1) acetate (0.3 g, 0.8 mmol) in ethanol (25 cm3), under reflux, and with the usual work-up followed by crystallisation from dichloro- methane, gave the orange-yellow complex 9 (0.3 g, 72%); mp 161-162 "C.(Found: C, 71.2; H, 8.4; N, 6.2%. C52H70Y404Ni requires: C, 71.2; H, 8.4; N, 6.4%), v,,, (CH2C1,)/cm-2920, 2855 (aliphatic C-H), 1605, 1584, 1500 (aromatic C=C); BH (CDCI,, 250 MHz): 8.28 (4 H, m, C,H5), 7,88 (4 H, d, J 8.8, C6H4), 7.44 (6 H, m, C6H5), 7.16 (2H, s, N=CH), 6.84 (4H,d, J 8.8, C6H4), 3.96 (4H, t, J 6.5, OC€f,C%), 1.79 (4H, m, OCH,CH,CH,), 1.1-1.5 [36H, m, OCH,CH,(CH,),CH,], 0.88(6 H, t, J 6.5, CH,); 6, (CDCl,, 250MHz): 175.9, 161.6, 152.2, 132.6, 131.2, 13T1, 130.4, 128.4, 122.5, 113.9, 68.1, 31.9, 29.7, 29.6, 29.41, 29.35, 29 2, 26.0, 22.7, 14.1. N-(4-n-Dodec ylox y)benzylidene-N-( 4-n-dodecylox y)-benzoylhydrazine 21 A mixture of 19 (R =C,,H25) (0.64 g, 2 mmol) and 14 (0.5 g, 2 mmol) was heated under reflux in ethanol (20 cm3) for 1 h.On cooling the reaction mixture the solid product was separ-ated by filtration and recrystallised from chloroform to give the hydrazine 21 as a yellow-white solid (1.0 g, 92%); mp 140-141.5 "C; v,,,(CH,Cl,)/cm-l: 3358, 3308 (NH ), 2922, 2548 (aliphatic C-H), 1675 (amide), 1604, 1574, 1500 (aro- matic C=C). bis [N-(4-n-Dodecyloxy) benzy1idene)-N-( 4-n-dodecyloxy- benzoyl) hydrazinato] nickel(r1) 10 A hot ethanolic solution of nickel@) acetate (0.1 g, 0.4 mmol) was added to a refluxing ethanolic solution (25 cm3) of 16 (0.4 g, 0.74 mmol). After heating the mixture under reflux for a further hour, the reaction mixture was cooled to room temperature when a deep orange-red solid separated.The solid was filtered off under suction, washed with ethanol, water and finally with hot methanol. Recrystallisation from toluene gave the pure complex 10 as orange-red crystals (0.3 g, 72%); mp 77.7 "C (A,=41.52 J g-l). (Found: C, 73.7; H, 9.9; N, 4.4%. C76H118N406Ni requires: c, 73.5; H, 9.6; N, 4.5%); v,,, (KBr)/cm-': 2920, 2840 (aliphatic C-H), 1595, 1580, (aromatic C=C); 8, (CDCl,, 250 MHz): 8.3 (4H,d, J 8.8, C6H4), 7.89 (4 H, d, J 8.8, C6H,), 7.10 (2H, s, CEJ), 6.95 (4 H,d, J 8.8, C6H4), 6.85 (4 H, d, J 8.8, C,H,), 3.9-4.0 (8 H, m, OCH,CH,), 1.80 (8 H, m, OCH,CEJ,CH,), 1.1-1.56 [72 H, 6OCH,CH,(CH,),CH,], 0.88 (12 H, t, J 6.5); 6, (CDCl,, 250 MHz): 175.1, la.4, 161.3, J.MATER. CHEM., 1994, VOL. 4 151.7, 134.8, 130.2, 124.3, 123.0, 114.3, 113.9, 68.2, 68.1, 31.9, 29.7, 29.6, 29.4, 29.3, 29.2, 29.16, 29.0, 22.7, 14.1. bis [N-Methylidene (4-n-alkyloxy) benzoylhydrazinato] -nickel(11) complexes 11 Formaldehyde (0.094 g, 3.13 mmol; 0.27 g, 35% w/w sol.) was added to a refluxing ethanolic solution (25 cm3) of 18 (3.13 mmol) and heating was continued for ca. 20 min to complete formation of 22. Nickel(I1) acetate (0.4 g, 1.6 mmol) was then added to the reaction mixture and reflux was continued for another 20 min. The resulting orange-yellow solid was collected by filtration and washed thoroughly with ethanol, water and finally with hot methanol. Recrystallisation from hot dichloromethane gave 11 as crystalline orange- yellow solids.The following nickel(I1) complexes 11 were prepared by the above general method: bis [N-Methylidene( 4’-n-butyloxybenzoyl) hydrazinato] nickel@) 11 (R=C4Hg) (0.53 g, 68%); v,,, (Nujol)/cm-l: 3315, 3275 (N-H) 2952, 2922, 2853, (aliphatic C-H), 1648 (C=O), 1619 (amide II), 1595,1571,1507 (aromatic C=C); dH(CDCl,, 250 MHz): 7.8 (4 H, d, J 8.8, C6H4), 7.085 (2 H, d, J 10.9 one of N=CH,), 6.85 (4 H, d, J 8.8, C6H4), 6.515 (2 H, d, J 10.9, one of N=CH2), 3.98 (4 H, t, J 6.6, OCH,CH,), 1.77 [4 H, m, OCH,(CH,)CH,], 1.31 [4 H, m, O(CH,),(CH,)CH,), 0.9 (6 H, t, J3.3, CH,). bis [N-Meth ylid&e( 4’-n-hexyloxybenzoyl) hydrazinato] nickel@) 11 (R=C&13) (0.665 g, 73%); (Found: C, 60.5; H, 7.0; N, 10.1%. C28H38N404Ni Requires: C, 60.8; H, 6.9; N, 10.1%).bis [N-Methylidene( 4’-n-octyloxybenzoyl) hydrazinato] nickel@) (14, R=C8H17) (0.58 g, 62%); Found: C, 63.1; H, 7.6, N, 9.4%. C3,H4,N4O4Ni Requires: C, 63.07; H, 7.61; N, 9.19%). bis [N-Methylidene( 4-n-decyloxybenzoyl )hydrazinato] nickel@) 11 (R=C10H21)(0.85 g, 82%); (Found: C, 63.9; H, 8.2%, N, 8.4%. C36Hs4N404Ni Requires: C, 65.0; H, 8.2; N, 8.4%). bis [N -Methylidene (4’ -n -dodecyloxy) benzoylhydrazinatol- nickel(r1)11 (R =C12H25) (0.9 g, 80%); (Found: C, 65.6; H, 8.2; N, 7.7%. C40H62N404Ni Requires: C, 66.6; H, 8.7; N, 7.8%). bis [N-Methylidene (4’-n- tetradecyloxybenzoyl) hydrazinatol- nickel(r1) 11 (R =C14H29 ) (0.86 g, 69%). bis [N -Methylidene (4’ -n -eicosyloxybenzoyl) hydrazinatol- nickel(I1) 11 (R=C,,H,,) (1.08 g, 73%).bis [N -Methylidene (4’ -n -docosyloxybenzoyl) hydrazinatol- nickel(1r) 11 (R=C,,H,,) (1.07 g, 69%). bis [N-Ethylidene (4-n-dodec yloxy) benzoylhydrazinatol-nickel(11) 12 The complex 12 was synthesized by a similar method to that used for the complexes 11. Treatment of nickel(I1) acetate (0.39 g, 1.37 mmol) with a refluxing ethanolic solution (25 cm3) of 4-n-dodecyloxyben- zoylhydrazine 18 (R =C12H2s)(1g, 3.13 mmol) and acetalde- hyde (0.14 g, 3.13 mmol), followed by the usual work-up, gave an orange-yellow solid. It was recrystallised from hot dichloromethane to give the pure complex 12 as an orange- yellow microcrystalline solid (1.0 g, 86%); mp 154-154.5 “C (Found: C, 66.9; H, 8.6; N, 7.6%.C4,Hs6N4o4Ni Requires: C, 67.3; H, 8.9; N, 7.5%); dH (CDCl,, 250 MHz) 7.8 (4 H, d, J 8.3, C6H4), 6.7-6.8 (6 H,m, C6H4 and =CHCH,), 3.95 (4H,t,J 6.5, OCH,CH,), 2.28 (6 H,d,J 5.6,-=CHCH3), 1.77 (4 H, m, OCH,CH,CH,), 1.1-1.5 [36H, OCH,CH,(CH2),CH3], 0.87(6 H, t, J 6.0, CH,). bis [N-Methylidene (4-n-alkyloxy) benzoylhydrazinatol- copper(11) complexes 23 The copper(I1) complexes 23 were synthesized by a method similar to that used for the nickel(1r) complexes 11. Copper(I1) acetate (0.31 g, 1.55 mmol) was treated with a refluxing ethanolic solution of the 4-n-alklyloxybenzoylhydra-zine 19 (3.13 mmol) and formaldehyde (0.1 g, 3.3 mmol; 0.28 g of 35% w/w solution). The bro Nn-yellow solid was filtered off and washed thoroughly with water, hot ethanol and dried under suction to give the copper complex 23 as a brown solid.The following copper(I1) complexes 23 were prepared by the above general method. bis [N-Methylidem( 4-n-decyloxy )benzoylh ydrazinato] copper (11) 23 (R=C10H21)(0.83 g, 79%); mp K+L/C 150-152‘C (dec. ca. 160°C) (Found: C, 63.8; H, 8.1; N, 8.4%. C36H54N404C~ Requires: C, 64.5; H, 8.1; N, 8.4%); vmaX (KBr)/crn-l: 2915, 2844 (aliphatic CH), 1600 (hydrazinato ring C=N), 1585 (aryl C=C), 1495 (s), 1468 (m), 1412 (s), 1370 (s), 1308 (m), 1245 (s), 1212 (m), 1168 (s), 1105 (w), 1050 (w), 1025 (m), 970 (m), 960 (m), 850 (m), 820 (m), 764 (m), 720 (w), 690 (m), 664 (m). bis [N -Methylidene (4’-n -dodecyloxy) benzoylhydrazinatol- copper(I1) 23 (R=C12H25) (0.8 g, 71%); mp K-+L/C 139-140 “C (dec.ca. 147 “C); vmax (KBr)/cm-’: 2910, 2840 (aliphatic CH), 1600 (hydrazinato ring C =N), 1585 (aryl C=C), 1495 (s), 1465 (m), 1412 (s), 1370 (s), 1305 (m), 1242 (s), 1215 (m), 1172 (s), 1105 (w), 1020 (m), 1000 (w), 978 (w), 910 (m), 850 (m), 830 (w), 760 (m), 728 (w), 690 (w), 660 (m). We thank the British Technology Group for financial support, the Overseas Student Sponsorship Scheme for a studentship for M.N.A., Dr. Peter Styring at the University of Hull for carrying out some of the DSC measurements and Dr. Barry Hunt, Department of Physics and Materials, University of Lancaster for allowing us access to their DSC facilities. References 1 M. N. Abser, M.Bellwood, M. C. Holmes and R. W. McCabe. J. Chem. Soc., Chem. Commun., 1993,1062. 2 L. El Sayed and M. F. Iskander, J. Znorg. Nucl. Chem., 1971, 33,435. 3 Ng. Ph. Buu-Hoi, Ng. D. Xuong, Ng. H. Ham. F. Binon and R. Roger, J. Chem. Soc., 1953,1358. 4 T. S. Ma and T. M. Tien, Antibiotics Chemothrrapy, 1953,3,491. 5 Q. Albert, Nature (London), 1953,9, 370. 6 J. M. Price, R. R. Brown and F. C. Larson, J. Clinic.Invest., 1957, XXXVI, 1600. 7 D. W. Bruce, Inorganic Materials, eds. I>. W. Bruce and D. O’Hare, Wiley, Chichester, 1992. 8 J. M. Price, Federation Proc., 1961, 20, 223. 9 L. Sacconi, J. Am. Chem. 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