Complex formation between Pd(II) and immobilized imidazol-azo-chromotropic acid

Abstract

1,8-Dihydroxy-2-(imidazol-2-ylazo)-naphthalene-3,6-disulphonic acid (imidazol-azo-chromotropic acid - IACA) was immobilized onto the anion exchange resin Dowex I-X8,50-100 mesh. The aim of this work was to investigate the mechanism of the complex formation between Pd(II) and immobilized IACA by following the absorption spectra of the solid phase. The reaction between Pd(II) and immobilized azo-dye was followed in the acidity range from pH I to pH 7. Pd(II) and 1ACA form 1:1 complex with the absorption maximum at 650 nm. The kinetics of complex formation was followed in pH range from I to 6, as the function of Pd(II) in excess. The effective forward (k(f)) and reverse (k(b)) pH dependent rate constants for complex formation were obtained from the linear dependence of k(obs) vs. Pd(II) concentration. Bell shaped pH profile (kf vs. pH) indicated that both ligand and metal ion, were included in acidic - basic equilibrium with H+ ion.