Kinetics of complex formation of 5,10,15,20-tetraphenylporphyrin and 2,3,7,8,12,13,17,18-octaethylporphyrin with iron valinate, guaninate, and adeninate

Abstract

The complex formation of 5,10,15,20-tetraethyl-porphyrin and 2,3,7,8,12,13,17,18-octaethylporphyrin with iron(III) valinate and iron(II) guaninate and adeninate in DMSO was studied by spectrophotometry. Kinetic parameters were estimated and a possible reaction mechanism was proposed. The nature of the macrocyclic ligand and salt were shown to affect the reaction kinetics. The complex formation was found to be hindered by shielding of the iron cation by the nitrogenous base and amino acid fragments. Quantum-chemical calculations by the PM3 method were used to obtain geometric characteristics of the reagents and reaction products. The calculation results showed that the formation of iron porphyrinates is accompanied by a decrease of planarity and an enhancement of steric strains in the complexes.