CATALYTIC INFLUENCE OF PYRIDINE ON COMPLEX-FORMING ABILITY OF OCTA(m-THREEFLUOROMETHYLPHENYL)PORPHYRAZINE AND HEXA(m-THREEFLUOROMETHYLPHENYL)BENZOPORPHYRASINE WITH ZINC ACETATE IN BENZENE

Abstract

The complexation of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-three-fluoromethylphenyl)benzoporphyrazine with zinc acetate in the pyridine-benzene system was studied. It was preliminary established that the electron absorption spectrum of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrazine in benzene contains a split Q-line in the visible spectrum, which is typical for the D2h symmetry of the π-chromophore of the molecule. The kinetically controlled reaction of formation of the zinc complex with the studied porphyrazines is observed only at a pyridine concentration in benzene of more than 0.09 mol/l. The reaction proceeds in the concentration range from 0.09 to 0.25 mol / l in benzene. Complexation is accompanied by an increase in the molecule symmetry from D2h to D4h, which indicates the formation of a zinc complex with octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine. It was found that the complexation is observed in a fairly narrow range of concentrations of pyridine in benzene, which made it impossible to determine the reaction order on the base. Considering the pronounced proton acceptor ability of the studied porphyrazines, a possible scheme of the mechanism includes the initial stage of the acid-base interaction of the macrocyclic molecule with pyridine to form the H-complex, followed by the entry of the zinc cation into the coordination region of the porphyrazine macrocycle. It was found that the rate of complexation of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine with zinc acetate increases with an increase in the concentration of pyridine in benzene at sufficiently low values of the activation energy of the process. This is due not only to the electron-acceptor influence of the nitrogen meso-atoms and substituents in the pyrrole rings of porphyrazine, which increase the polarity of the NH-bonds, but also to the proton-acceptor ability of pyridine, which supports the removal of NH-groups protons from the macrocycle region. It was found that benzo-substitution in octa(m-threefluoromethylphenyl)porphyrazine does not affect the rate and activation parameters of zinc complex formation, which indicates a close protonisation of intra-cyclic NH-bonds of porphyrazine molecules.Forcitation:Osipova G.V., Petrov O.A. Catalytic influence of pyridine on complex-forming ability of octa(m-threefluoromethylphenyl)porphyrazine and hexa(m-threefluoromethylphenyl)benzoporphyrasine with zinc acetate in benzene. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 31-36