QUANTUM-CHEMICAL CALCULATION AND SPECTROSCOPIC STUDY OF pi-CONJUGATION PATHWAY IN NH-TAUTOMERS OF CORROLE FREE BASES

Abstract

The pi-conjugation pathways were identtfied and the degrees of aromaticity for NH-tautomers of corrole free bases were determined by quantum chemistry methods and absorption spectroscopy. The macrocycle skeletal atoms participated differently in the formation of the pi-conjugation pathway. It was supposed that conjugation pathways consisting of 18 pi-electrons were dominant. At the same time, each of two NH-tautomers possessed its own distinct pi-conjugation pathway, which caused their degrees of aromaticity to differ. It was shown that the peripheral substitution architecture of the macrocycle influenced the degree of aromaticity. A method for controlling the equilibrium between the two NH-tautomers that consisted of designing the electron-density distribution in the macrocycle that was characteristic of one of the tautomers was proposed and proved experimentally.