Electron spin resonance and magnetic studies on some copper(II) azobarbituric and azothiobarbituric acid complexes

Abstract: Electron spin resonance and magnetic susceptibility on some copper(II) complexes prepared from phenylazobarbituric and phenylazothiobarbituric acid compounds containing 2,5-dichloro and 2,5-dimethyl groups were discussed. The thio complexes exist in dimer–monomer mixture. The corresponding copper(II) complexes of the oxygen homologous failed to exhibit association. Singlet–triplet separation values equal to -321 and -263cm-1 for the 2,5-dimethyl and 2,5-dichloro complexes, respectively, of the thio series. An empirical measure of the amount of tetrahedral deformation based on the values of g||/A|| assigned the square-planar geometry of the dimethyl-oxygen complex while the other complexes are with tetrahedral planar geometries. The effect of temperature on the ESR data was discussed. The diamagnetic properties of the complexes derived from 2,5-dichloro and 2,5-dimethyl thiobarbituric acid suggested the formation of Cu(I) compelxes. [Copyright &y& Elsevier]