pH-metric and spectrometric study of oxovanadium(IV) complexes with glycylalanine and imidazoles

The equilibria in the systems VO2++A+B (A=glycylalanine, B = imidazole, 2-methylimidazole and 2-ethylimidazole) have been studied at 25degreesC and I = 0.1 M NaClO4 medium by a combination of pH-potentiometric and spectroscopic methods (epr and visible absorption). Formation constants of different binary and ternary complexes were evaluated using the SCOGS computer programme. The formation constant of ternary complexes follows the following order with respect to different imidazoles: 2-methylimidazolegreater than or equal to2-ethylimidazole>imidazole. The trends have been explained in the fight of the electronic and molecular structures. (C) 2003 Elsevier Science B.V. All rights reserved.