INVERSION OF AROMATICITY OF NH-TAUTOMERS OF FREE-BASE CORROLES IN THE LOWEST TRIPLET T1-STATE

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.

Automated summary

This study investigates the aromaticity in the lowest triplet T-1-state of NH-tautomers of corrole free bases with different peripheral substitution architecture using quantum chemistry methods. It is found that although the dominant pi-conjugation pathways in the ground singlet (S-0) and excited triplet (T-1) states are the same for each of the two tautomers, the dominant pi-conjugation pathways differ for the NH-tautomers. The degree of aromaticity of the macrocycle in the triplet T-1-state decreases significantly compared to the ground S-0-state, indicating an antiaromatic behavior. The relationship between the degree of aromaticity, macrocycle conformation, and electronic effects of peripheral substituents is discussed.