Thermodynamics of Formation of Molecular Synthetic Metalloporphyrin Complexes with Pyridine in Benzene and in Chloroform at 298.15 K

Abstract

Microcalorimetric titration was used to determine the thermodynamic characteristics (Kc, ΔH, and ΔS) for the axial coordination of pyridine by the metal complexes of synthetic porphyrins (ZnTBP, ZnTPTBP, MgTPTBP, and CuTPTBP) in benzene and in chloroform at 298.15 K. The capability of the metalloporphyrins under study to coordinate pyridine in chloroform decreases as follows: ZnTPP > ZnTBP > ZnTPTBP > MgTPTBP > CuTPTBP. The complicated course of the studied processes was shown to be determined by the electronic structure of the central metal atom, the nature of the porphyrin macrocycle, and by the specific solvation interactions of metalloporphyrin and pyridine with the solvent molecules.