COMPLEXATION OF A NEW MULTIDENTATE LIGAND 2-CARBOXYPHENYL)AZO]-8-HYDROXYQUINOLINE-5-SULFONIC ACID WITH NI(II), VO(IV), ZN(II), AND CD(II)

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