ELECTRONIC AND MAGNETIC-PROPERTIES OF BILIVERDINATE DIMETHYLESTER METAL(II) COMPOUNDS ([MII(BVDME)] (M = MNII, COII, CUII, ZNII)

Biliverdinate dimethylester metal(II) compounds, [MII(BVDME)] (M = MnII, CoII, CuII, ZnII) have been characterized by their electronic and magnetic properties. ESR parameters of cobalt and copper compounds are in agreement with a planar structure of coordinated biliverdinate dianion, and the ground state configurations of metals are respectively (xz or yz)2(yz or xz)(x2-y2)2(z2)2 and (xz)2(yz)2 (x2-y2)2(z2)2(xy). These configurations well explain the presence of a radicalic species formulated as biliverdinate dimethylester cobalt(III) radical anion, [CoIII(BVDME)]., beside the corresponding cobalt(II) compound, [CoII(BVDME)]. The preparation method or the interaction with a solvent can make variations in the amount of the radicalic form [CoIII(BVDME)].; dilution by [ZnII(BVDME)] or the presence of base donor solvent (pyridine) completely removes the interaction between Co(III) and (BVDME).. A comparison between [CoII(BVDME)] and the cobalt oxygen carriers compounds usually employed as models of the heme proteins leads to conclude that [CoII(BVDME)] does not reduce O2 to O-2, probably because the electron transfer to BVDME ligand successfully competes with that to the O2 molecule. © 1983.