ESR STUDY OF SOME SOLVENT EFFECTS OF THE CU(II)-ASPIRINATE COMPLEX

Powder ESR spectra of the [Cu-2(Asp)(4)](H2O)(2) complex show the existence of Cu(II) acetate like dimers characterized by a strong antiferromagnetic exchange interaction (J = -288 cm(-1)). In pyridine-dimethylformamide solutions the monomeric species prevail. Two different monomeric species, the Cu(DMF)(4) of planar-distorted tetrahedral (T-d) symmetry and the Cu(Asp)2(DMF2) 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)(2) and Cu(Asp)(2)(Py)(2), the last species having a CuN2O2 chromophore in a trans square-planar arrangement. In pyridine Cu(II)-aspirinate solution only the Cu(Py)(4) monomeric species of CuN4 chromophore was evidenced.