COMPLEXATION OF A NEW MULTIDENTATE LIGAND 7-[(3,5-DICHLORO-2-CARBOXYPHENYL)AZO]-8-HYDROXYQUINOLINE-5-SULFONIC ACID WITH Ni(II), VO(IV), Zn(II), AND Cd(II)

Abstract

A new title multidentate ligand (CAHQS) containing both carboxyphenylazo and 8-quinolinol fragments has been prepared for the first time. Proton dissociation processes of CAHQS and coordination selectivities of CAHQS toward VO(IV), Ni(II), Zn(II), and Cd(II) have been probed by means of electronic spectroscopy, polarography, and Raman spectroscopy of the complexes in aqueous solutions. It has been shown that the selectivity of CAHQS toward such metal ions is dependent on steric factors in the chelate ring formed, not on HSAB properties of the coordination sites in CAHQS and of such metal ions. Complexing equilibria and stability constants are also reported.