Thermodynamics of chelation. I. Iron(II) and zinc(II) complexes of Pyridine-2-aldehyde-2'-pyridylhydrazone

Abstract

In dilute solution, pyridine-2-aldehyde-2'-pyridylhydrazone can behave as a diacid base or as a tridentate chelating agent. Its cationic bis complexes further undergo two stages of deprotonation. Equilibrium constants have been measured at seven temperatures from 5º to 60º and over a range of ionic strength. They have been used to derive values of enthalpies and entropies of reaction with H⁺, Fe²⁺, and Zn²⁺.