Crystal structures and mesomorphic properties of Schiff base homologs and derivatives, and magnetic properties of their dimeric and dinuclear copper(II) complexes

Three N2O4 Schiff. base homologs, H(2)L1 (n = 8), H(2)L3 ((n = 9), and H(2)L4 (n = 10) were obtained from the reactions of 2-HOC6H4CHO with H2N(CH2)(8-10)NH2, while a derivative of H(2)L1, namely, H(2)L2, was obtained from the reaction of 3,5-X-2-2-HOC6H2CHO (X = tert-butyl) with H2N(CH2)(8)NH2. The Schiff bases H(2)L2 (triclinic; P-1), H(2)L3 (monoclinic; C2/c), and H(2)L4 (monoclinic; P21/c) were single crystals with low melting temperatures (less than 100 degrees C). The homologs exhibited mesomorphisms, while the derivative was not mesomorphic and did not reform crystals from its melt. Copper(II) complexes of H(2)L1, H(2)L2 and H(2)L4 were dimeric, while that of H(2)L3 was dinuclear with chelating CH3COO ligand. These complexes were paramagnetic with insignificant interactions between the copper(II) atoms and have high decomposition temperatures (T-dec = 268-304 degrees C). Their melting temperatures (T-melt = 138.9-190.2 degrees C) were higher than the corresponding Schiff bases, but they were not mesomorphic.