Jahn–Teller triplet excited state structures and spectra of zinc complexes of porphyrin and phthalocyanine: A density functional theory study

Abstract

Density functional theory (DFT) electronic structure calculations were carried out to predict the triplet Jahn–Teller distorted structures and energetics for zinc complexes of porphyrin (ZnP), tetraazaporphyrin, tetrabenzoporphyrin, and phthalocyanine. The D4h square planar structures in the ground state are found to distort along the b1g mode leading to the D2h rectangle structures in the lowest triplet state. Time-dependent DFT calculations were also carried out to interpret the observed triplet–triplet spectra and to quantify the effects of meso-tetraaza substitutions and tetrabenzo annulations on ZnP. The computed triplet–triplet excitation energies and oscillator strengths are in good agreement with experiment. The effects of meso-tetraaza substitutions and tetrabenzo annulations on the triplet excited state structures and spectra are discussed in detail.