EPR investigation of two Cu(II) complexes with low symmetry

The results of the solvent effects on the Cu(II)-bis(8-hydroxyquinolinate) (Cu(8HQ) 2 ) and Cu(II)-bis (monothiodibenzoylmethanate) (Cu(DBMS) 2 ) complexes obtained by EPR spectroscopy are presented. Assuming the D 2h symmetry with d x 2 -y 2 orbital as ground state for paramagnetic electron, all the MO coefficients for the metal-ligand bonds are estimated by using Buluggiu formalism. A strong anisotropy of the covalence degree in the ground state Ψ Ag(x2-y2) of both investigated compound, Cu(8HQ) 2 and Cu(DBMS) 2 was evidenced (α' 2 /α" 2 ? ≥ 2). Both in plane σ and Π bonds are more covalent in the case of Cu(DBMS) 2 compound than in Cu(8HQ) 2 . The out-of-plane Π bonds have practically an ionic character in the fist compound with some differences between Cu-O and Cu-N bonds. The ionic character of these Π bonds is diminished in the case of Cu(DBMS) 2 and Cu-S bond is more covalent than Cu-O.