Complexes of Zn(II) and Cd(II) with 4-(2-pyridylazo)resorcinol sorbed on sephadex QAE: characterization and theoretical study Original Research Article

The nature of the complexes produced in the reaction between Zn(II) or Cd(II) and 4-(2-pyridylazo)resorcinol (PAR), sorbed on a Sephadex QAE anion exchanger have been studied. The visible and IR absorption spectra of the species fixed on the exchanger have been established; the stoichiometry of the complexes is 1:2 (metal:ligand). To propose a structure for the metal complexes, semi-empirical molecular orbital calculations have been performed for the dianionic form of PAR (L2−) and for its complexes ZnL2−2 and CdL2−2 by means of the SPARTAN program. The role of MOs for the ligand in possible coordination to metal ions is discussed and a distorted octahedral structure is proposed for both complexes. For comparison, Zn(HL)2·H2O and Cd(HL)2·H2O have been synthesized and characterized by the normal instrumental techniques.