Metal Complexes of Unsubstituted Corrole for Fundamental Studies
The prosthetic groups of molecules such as heme and Vitamin B12 are composed of cyclic metal-chelating tetrapyrroles known as porphyrin and corrin, respectively. In 1965, Kay and Johnson reported corroles, an 18π-electron conjugated version of the nonaromatic corrin. Despite this discovery, corrole chemistry remained quite undedeveloped until 1999 due to main challenges in the synthesis of the macrocycle. The breakthrough achieved by the Gross and Paolesse groups in synthesizing triaryl corroles through the very facile single-step condensation of pyrroles and aromatic aldehydes revolutionized the field. This achievement enabled the synthesis numerous of corrole derivatives, leading to many applications of the corresponding corroles in science and technology. The synthesis of the unsubstituted corrole (the parent corrole) still remained elusive, likely because of its large electron density turns it sensitive to light and oxidation. In 2021, the Gross group successfully synthesized the parent corrole, marking a significant milestone. Building upon this achievement, this research project focused on investigating the electronic structures of the cobalt(III) complexes of parent corrole as a function of the metal’s axial ligands. We synthesized six such complexes and subsequently conducted DFT, X-ray, UV-Visible, and NMR studies to analyze their geometric and photophysical properties.