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

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.

Automated summary

The pi-conjugation pathways and degrees of aromaticity for NH-tautomers of corrole free bases were determined using quantum chemistry methods and absorption spectroscopy. The formation of pi-conjugation pathway involved different participation of atoms in the macrocycle skeleton. Conjugation pathways with 18 pi-electrons were found to be dominant. Each NH-tautomer had its own distinct pi-conjugation pathway, leading to different degrees of aromaticity. The peripheral substitution architecture of the macrocycle was found to influence the degree of aromaticity. A method for controlling the equilibrium between the NH-tautomers by designing the electron-density distribution in the macrocycle was proposed and experimentally proved.