Kinetic and equilibrium studies of the acid dissociation of the zinc(II) complexes of N,N' -dialkyl-1, 10-phenanthroline-2,9-dimethanamine ligands

Abstract

The complexation property and the acid dissociation kinetics of the zinc(II) complexes of N,N' -dialkyl-1, 10-phenanthroline-2,9-dimethanamine ligands have been studied using <i>p</i>H-metric and a stopped-flow spectrophotometer. In 3.3×10^-3 ~1.2×10^-2 mol dm^-3 HCl (<i>I</i>=0.5 mol dm^-3, HCl + NaCl), the dissociation rate follows the law <i>k</i>_obs<i>= kK'</i>[H⁺].<i> </i>The acid

dissociation can be rationalized in terms of four-step kinetic process involving two rapid pre-equilibrium protonations and rate-determining cleavage of the Zn(II)-N(phenanthroline) bond. Steric effects on the stability of complexes and on the kinetic process have also been discussed.