ESR study of some solvent effects of the Cu(II)-aspirinate complex

Abstract

Powder ESR spectra of the [Cu2(Asp)4](H20)z complex show the existence of Cu(II) aeetate like dimers characterized by a strong antiferromagnetic exchange interaction (J =-288 cm l), In pyridine-dimethylformamide solutiotas the monomeric species prevait. Two different monomeric species, the Cu(DMF)4 of planar-distorted tetrahedral (Td) symmetry and the Cu(Asp)2(DMF) 2 with elongated tetrahedral-octahedral symmetry were evidenced in DMF solution adsorbed on NaY zeolite. In 40 % Py + 60 % DMF solution two monomeric species were also identified. These are Cu(Asp)2(DMF)z and Cu(AsP)2(Py)2, the last species having a CuN202 chromophore in a trans squareplanar arrangement. In py¡ Cu(lI)-aspirinate solution only the Cu(Py)4 monomeric species of CuN 4 chromophore was evidenced.