DICOPPER(II) COMPLEXES OF NOVEL POLYFUNCTIONAL PYRIDAZINES - CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF BIS[MU-PYRIDAZINE-3,6-DICARBALDEHYDE DIOXIMATO(1-)-KAPPA-N1,N'-N2,N'']-BIS[AQUA(PERCHLORATO-KAPPA-O)COPPER(II)]

Two novel pyridazine ligands with 3,6-CR = NOH (R = H, H2L1; Ph, H2L2) oxime side chains were synthesised. The related copper(II) dinuclear complexes [Cu2(HL1)2(ClO4)2(H2O)2] 1 and [Cu2(HL2)2-(ClO4)2(MeOH)n] 2 were obtained subsequently. The crystal structure of 1 was determined: space group P2(1)/n, a = 12.031(6), b = 9.517(4), c = 9.973(5) angstrom, beta = 100.16(4)-degrees and Z = 2. The copper(II) ions of the binuclear unit are bridged by the two diazine fragments of the two essentially planar tetradentate ligands with the oxime nitrogen atoms completing the equatorial co-ordination. Two intra-complex hydrogen bridges link the terminal oximato moieties to give dinucleating macrocyclic complexes. In complexes 1 and 2 the copper(II) is in a classical 4 + 2 environment. The magnetic properties of those compounds revealed a spin-singlet ground state in each case. The singlet-triplet energy gaps were found to be -536(2) for 1 and -545(4) cm-1 for 2. The low-lying states of the complexes are discussed in relation to the nearly planar structure of the macrocyclic complexes.