Thermodynamic Study of Coordination Reaction of Zinc Tetraphenylporphyrins with Substituted Imidazoles

Equilibrium constants for reactions of ZnT(p-X)PP(para-substituted zinc tetraphenylporphyrins) with ligands of the substituted imidazole in CH2Cl2 and several other solvents have been determined by visible spectral techniques, and Rose-Drago method. Electronic effects in metalloporphrins and effects of ligands, temperature and solvents were investigated. It was found that equilibrium constants for reactions of ZnT(p-X)PP with ligands follow Hammett equation. The changes of standard molar enthalpy ��rH�� m and the changes of standard molar entropy ��rS��m of the reactions were obtained from the plots of lnK ��vs. 1/T.