Thermodynamic Studies of 2-(5 Cu(II), Co(II), Ni(II) and Zn(II) Complexes

Abstract

The metal-ligand mole ratios and the stability constants of the Cu(II), Co(II), Ni(II) and Zn(II) complexes at 2-(5- bromo-2-pyridylazo)-5-diethylamino)phenol were determined using a spectrophotometric method at different temperatures (20, 30, 40 and 50±0.1 °C) and ionic strengths (0.05, 0.1 and 0.2) in 30% (v/v) aqueous ethanol. Plots of thermodynamic stability constants at zero ionic strength (In K°) versus T-1 gave linear curves; the ensuing complex formation (ΔH° and ΔS°) values calculated from these plots. The changes in free energy for each metal-ligand system were evaluated. © 2001 Elsevier Science Ltd. All rights reserved.