IMIDAZOLATE-BRIDGED COPPER(II) COMPLEXES WITH INFINITE ZIGZAG-CHAIN AND TETRANUCLEAR STRUCTURES FORMED BY DEPROTONATION AND SELF-ASSEMBLY

A method of molecular design of self-assembling metal complexes has been established. The copper(II) complex with a quadridentate ligand [Cu(HL2)]ClO4 undergoes deprotonation of the imidazole proton under basic conditions to give an imidazolate-bridged polymeric compound [(CuL2)infinity], where H2L2 = N-3-ethoxysalicylidene-N'-imidazol-4-ylmethylenecyclohexane-1,2-diamine. The latter compound crystallizes in the monoclinic space group P2(1)/a with a = 15.515(5), b = 9.338(5), c = 12.660(2) angstrom, beta = 95.33(2)-degrees, and Z = 4, R = 0.078 for 1721 reflections. It has an infinite zigzag-chain structure and the variable-temperature magnetic data are well reproduced using the Ising model based on H = -2SIGMAJ(ij)S(i)S(j) with a J value of -1.8 cm-1. The complex [Cu(HL3)Cl]ClO4 with a tridentate ligand gives an imidazolate-bridged tetranuclear complex [(CuL3)4] [ClO4]4 on deprotonation at the imidazole nitrogen, where HL3 = N-imidazol-4-ylmethylene-N',N'-dimethylpropane-1,3-diamine. The latter compound crystallizes in the triclinic space group P1BAR with a = 1 5.216(6), b = 15.592(5), c = 1 5.1 02(5) angstrom, alpha = 104.98(3)-degrees, beta = 108.44(3)-degrees, gamma = 61.12(2)-degrees, Z = 2, and R = 0.096 for 6931 reflections. The structure consists of a cyclic tetranuclear molecule in which each imidazolate nitrogen atom co-ordinates axially to the copper(II) ion of the adjacent unit. Variable-temperature magnetic data are well reproduced using the Heisenberg model based on H = -2J(S1.S2 + S2.S3 + S3.S4 + S4.S1) with J = -60.0 cm-1.