Thermodynamic studies of 2-(5-bromo-2-pyridylazo)5-diethylamino)phenol 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 degreesC) 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 degrees) versus T-1 gave linear curves; the ensuing complex formation (DeltaH degrees and DeltaS degrees) values calculated from these plots. The changes in free energy for each metal-ligand system were evaluated. (C) 2001 Elsevier Science Ltd. All rights reserved.