Complexes of zinc 5,15-di(ortho-methoxyphenyl)octaalkylporphyrinate with nitrogen-containing bases

Abstract

The formation of molecular complexes of zinc 5,15-di(ortho-methoxyphenyl)-2,8,12,18-tetramethyl-3,7,13,17-tetrabutylporphyrinate (ZnP) with nitrogen-containing bases L (L is imidazole, 2-methylimidazole, pyridine, 3,5-dimethylpyrazole, or dimethylformamide) in benzene is studied by spectrophotometry and computer simulation. The nature of an additional molecular ligand affects the stability of the macrocyclic complex (L)ZnP. The stability constant of this complex increases linearly with an increase in the basicity of the extra ligand and is proportional to the shift of the main absorption bands in the electronic spectra (Q(0–1), B (Soret band)). The molecular structures of zinc porphyrinate and its extra complexes are optimized by the PM3 quantum-chemical method. Their geometric and energy parameters are calculated. Correlations between the calculated energies of interaction of the central metal atom with the nitrogen atom of the extra ligand and the stability of (L)ZnP are found. The dependence of the zinc-extra ligand bond strength on the basicity of the additional molecular ligand is determined on the basis of the experimental and calculated data. The coordination properties of the compound under study are found to be affected by steric strains.