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Journal of Structural Chemistry

2009 year, number 4

INTERMOLECULAR INTERACTIONS OF TETRAPHENYL-PORPHYRIN AND ITS PYRIDINE METALLOCOMPLEXES IN THE CRYSTALLINE STATE

E. A. Malkova, N. S. Lebedeva, А. I. V'yugin
Keywords: metallotetraphenylporphyrin, molecular complexes, thermooxidative destruction, thermogravimetric analysis, kinetic characteristics
Pages: 795-801

Abstract

Crystalline solvates of synthetic tetraphenylporphyrin and its pyridinie metallocomplexes (Zn2+, Сu2+, Ni2+, Co2+, Mn3+, Fe3+) have been studied by thermogravimetric analysis. A comparative analysis of our thermochemical data and the literature XRD data was carried out for the pyridine complexes of metallotetraphenylporphyrins. It was found that the energy stability and structural characteristics of the pyridine complexes of metallotetraphenylporphyrins depended on the nature of the central metal ion. The pyridine complexes are stabilized by the direct metal−porphyrin π-dative macrocycle interaction and the increased residual positive charge on the central metal ion. The activation energies of thermal destruction of the pyridine complexes of metallotetraphenylporphyrins vary from 230 kJ·mol-1 to 330 kJ·mol-1, which is suggestive of the high kinetic stability of the complexes. For the molecular complexes under study, the limiting stage of destruction was found to be the chemical reaction itself, and the kinetic characteristics demonstrated the compensation effect, indicative of the similar mechanism of thermooxidative destruction of the pyridine complexes of metallotetraphenylporphyrins.