Density Functional Theory Study of Meso-Tetra-Substituted Porphyrins: 3-Pyridyl Substitution for Phenyl

Abstract

In the present work, the geometry, electronic structure, and infrared spectra (IR) of meso-tetra-substituted porphyrin have been investigated theoretically. The optimization of geometries and electronic structure calculations of meso-tetraphenylporphyrin (TPP) and meso-tetra(3-pyridyl)porphyrin (T₃PyP) are performed on the basis of density functional theory. The substitution of pyridyl for phenyl in meso-tetra-substituted porphyrins can result into the reduction of molecular size, including the molecular diameter, as well as the size of the central ring of porphin. It has also been found that the molecular orbital energies of T₃PyP are smaller than the counterparts of TPP whereas there is almost no change in the HOMO–LOMO gap. Additionally, the infrared spectrum of TPP and T₃PyP has been compared in order to determine whether there is a red shift or a blue shift.