Quantum-chemical calculation and spectroscopic study of π-conjugation pathway in NH-tautomers of the free base corroles

Abstract

he π-conjugation pathway was identified and the degree of aromaticity for the NH-tautomers of the free base corroles was determined by quantum chemistry methods and absorption spectroscopy. Different participation of the macrocycle skeletal atoms in formation of the π-conjugation pathway was established, and it was supposed that conjugation pathway consisting of 18 π-electrons were dominating. At the same time, each of two NH-tautomers possesses its own distinct π-conjugation pathway, which provides the differences in the aromaticity degree. It was shown that architecture of the peripheral substitution of a macrocycle influences the degree of aromaticity. Method of the control over the equilibrium between two NH-tautomers was proposed and experimentally proved. It consists in the design of the electronic density distribution in macrocycle which is characteristic for one of the tautomers.