INVERSION OF AROMATICITY OF NH-TAUTOMERS OF FREE-BASE CORROLES IN THE LOWEST TRIPLET T-1-STATE

Abstract

The aromaticity in the lowest triplet T-1-state of NH-tautomers of corrole free bases with different peripheral substitution architecture was investigated using quantum chemistry methods. It was established that the dominant pi-conjugation pathways differed for the NH-tautomers although the dominant pi-conjugation pathways in the ground singlet (S-0) and excited triplet (T-1) states for each of the two tautomers were the same. The degree of aromaticity of the macrocycle in the triplet T-1-state was found to decrease distinctly as compared to the ground S-0-state. It was shown that the macrocycle of the corrole free bases in the triplet T-1-state should be considered antiaromatic. Relationships of the degree of aromaticity with the macrocycle conformation and electronic effects of peripheral substituents were discussed.