Features of Formation of Mixed-Ligand Complexes of Aluminum Tetraphenylporphine

摘要

Formation of extra complexes of aluminum tetraphenylporphine was studied by spectrophotometric titration. The effect of the nature of nature of acido ligands on the stability of mixed-ligand complexes of aluminum tetraphenylporphine was determined. The stability constant (log K_(st)) of sterically unstrained complexes (Cl)Al(L)TPP and (OH)Al(L)TPP increases linearly with increasing basicity of the extra ligand (log K_(BH~+)); in the case of sterically distorted complexes (OAc)Al(L)TPP and (Acac)Al(L)TPP changes in log K_(st) and log K_(BH~+) vary in the same direction. The geometries and energy characteristics of six-coordinate complexes of aluminum porphyrins were calculated quantum-chemically. The calculated enthalpies and Gibbs energies of formation of the complexes are consistent with the experiment. The possibility of the bidentate coordination of acetate and acetylacetonate in the porphyrin extra complexes was proved.