MAGNETIC-PROPERTIES OF DIAMINOGLYOXIME COMPLEXES WITH A SLIPPED-STACKSTRUCTURE MINO-4-HYDROXY-1,4-DIAZABUTA-1,3-DIEN-1-OLATO)M-II (M=CO, NI, AND CU)

The magnetic properties of the divalent metal complexes [ML2(HL)] (M = Co-II, Ni-II, and Cu-II; HL = 2,3-diamino-1,4-diazabuta-1,3-diene-1,4 -diol, i.e., diaminoglyoxime) with a slipped-stack structure were exam ined. The magnetic susceptibilities and the electron spin resonance sp ectra indicate that [CoL2(HL)] exhibits a ferromagnetic interaction al ong the stack chain, the strength of which is estimated to be 13.5 K, while [CuL2(HL)] is paramagnetic and [NiL2(HL)] is diamagnetic. The ma gnetic behaviors of the [ML2(HL)] complexes can be predicted precisely by comparing the spin splittings of the partially occupied molecular orbitals of the monomer complexes ML2 and the dimer complexes 2ML(2) w hich are equivalent in structure to the relevant moieties in the real stack chains, based on molecular calculations using the DV-X alpha met hod. The modes of the differential spin densities for the dimers 2ML(2 ) strongly suggest that the principal mechanism of superexchange on [C oL2(HL)] may operate through strong interaction of the 3d(zx) orbitals of Co atoms with the 2p(z) orbitals of two apical N atoms which form the pi(z)-type systems of the adjacent complex molecules along the sta ck chain.