Synthesis and Characterization of a Cobalt(III) Corrole with an S-Bound DMSO Ligand

Abstract

We have synthesized a low-spin Co(III) complex of 5,15-bis(4-nitrophenyl)-10-(2-methylcarboxyphenyl)corrole with an S-bound dimethylsulfoxide (DMSO) ligand (1DMSO) and determined the coordination mode through X-ray diffraction for the first time. UV-vis-NIR spectral data show that the DMSO ligand does not dissociate in MeCN solution, and EPR results indicate that the first oxidation is ligand centered and suggest that not only DMSO remains bound but a second apical ligand, possibly MeCN, binds to the cobalt center. Multiconfigurational wavefunction electronic structure methods (CASSCF/NEVPT2) allowed us to determine that in the neutral complex the corrole behaves as an innocent trianionic ligand and that the σ-donor effect of the S atom determines the low-spin configuration by raising the energy of the Co 3dz2 orbital. While DFT calculations predict a ground open-shell singlet for both S-bound and O-bound DMSO variants, CASSCF/NEVPT2 calculations predict a closed-shell singlet ground state in both cases. These calculations reproduce considerably well the UV-vis-NIR spectrum of 1DMSO in solution, validating the closed-shell singlet description.