The XMS-CASPT2 results conclusively showed that the ground electronic state of both the unsubstituted and substituted copper corroles is a multiconfigurational singlet S 0 exhibiting a saddle structure. Conversely, the higher-energy triplet ground state T 0 corresponds to a planar geometry, which is approximately 5 kcal/mol higher in energy than the S 0 state. It is worth noting that the unsubstituted copper corrole displays a planar T 0 geometry, while the 5,10,15-triphenyl copper corrole system exhibits reduced planarity in the triplet state.