Synthesis, structures, and properties of BCOD- and benzo-fused cobalt corroles

Herein, we report the synthesis of cobalt-coordinated β-β’ bicyclo[2.2.2]octadiene-fused corrole 1-Co and benzo-fused 2-Co with axial PPh 3 ligands. The structures and properties of 1-Co and 2-Co are fully studied via single-crystal X-ray diffraction, UV-Vis spectroscopy, cyclic voltammograms, and density functional theory calculations. The benzo-fusion of 2-Co leads to a reduced energy gap and distinct coordination, photophysical, and redox properties. Compared to 1-Co, 2-Co exhibits increased bond-length alternation, red-shifted UV-vis absorption bands, and decreased aromaticity. For 2-Co, the axial PPh 3 dissociates during both oxidation and reduction processes, but for 1-Co, the dissociation occurs only during reduction. The theoretical calculations further predict a low-lying open-shell singlet state for 2-Co. This study advances the functionalization strategy of cobalt corroles for a broader range of potential applications.