Studies on Heterodinuclear Metal Complexes

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(1) Phenol-based dinucleating macrocycles, derived from the 2 : 1 : 1 condensation of 2,6-diformyl-4-methylphenol, H_2N-(CH_2)_m-NH_2(m=2,3) and H_2N-(CH_2)_n-NH_2(n=3,4), formed heterodinuclear Ni(II)Mn(II), Cu(II)Mn(II), Ni(II)Co(II), Cu(II)Co(II) and Cu(II)Ni(II) complexes whose molecular structures were determined by X-ray chrystallography and physicochemical properties were examined. Cryomagnetic studies revealed antiferromagnetic interaction in the complexes except for Ni(II)Mn(II) and Ni(II)Co(II). All the complexes were stable in solution and form unusual oxidation-state complexes such as Ni(I)Co(II), Ni(I)Co(I), etc. The Cu(II)Ni(II) complex showed a very strong antiferromagnetic interaction to exist as the spin-doublet ground state at liquid nitrogen temperature. ESR study for the S_T=1/2 state showed a spin-delocalization over the CuNi core.(2) A Co(II)Pb(II) complex of a related macrocycle, having two dissimilar metal-binding sites of the N_2O_2 and N_2O_3 donor sets sharing two phenolic oxygens, was prepared. It acts as a reversible dioxygen-carrier in solid state owing to a neighboring effect of the Pb(II) ion.(3) Phenol-based dinucleating macrocycles, with two dissimilar N(amine)_2O_2 and N(imine)_2O_2 metal-binding sites sharing two phenolic oxygens, were prepared and a series of Cu(II)M(II)(M=Mn, Co, Ni, Cu, Zn) complexes were derived. CV for the complexes showed a considerable stabilization on electrode and formation of unusual oxidation-state compounds like Cu(I)Mn(II) etc.