Abstract

Complexes of nicotinic acid hydrazide [NAH] with M (II) sulphates (M = Fe, and Cu) have been synthesized and characterized by elemental analysis, conductance, magnetic susceptibility and electronic spectral studies. The infrared data suggest that the ligand act as neutral bidentate donors ligating through the carbonyl O and the azomethine N. The magnetic and spectra data indicate a distorted octahedral geometry in all the complexes. Thetemperature effect showed that the reaction rate increased slightly with increase in temperature. The plot of the natural logarithm of the concentration of complexes obtained over time (sec) showed that the reaction had a pseudo first order kinetics. The activation entropy obtained from plots of ln(kobs/T) vs. 1/T of the complexes were -327.314 and -320.347, J.K-1.mol-1 for [Cu(NAH)2]SO4.3H2O and [Fe(NAH)2]SO4.3H2O, respectively agreeing with an associative mechanism of reaction. The activation enthalpy for [Cu(NAH)2]SO4.3H2O and [Fe(NAH)2]SO4.3H2O were -2.403 and -2.619, respectively. The negative enthalpies were an indication that the reaction was rather exothermic. The activation energies Ea for [Cu(NAH)2]SO4.3H2O and [Fe(NAH)2]SO4.3H2O were -107.361 and -105.038 kJmol-1 at 328 K. The lower Ea is an indication that the complexes required lower energy before it crossed over to the product formation state at lower temperature.