with fully internally contracted (FIC) analytical gradients as implemented in the bagel program package. Geometries of the two copper corrole complexes were optimized for the ground singlet (S 0 ), and the lowest energy triplet (T 0 ) state. The first excited singlet state (S 1 ) was also computed for bare copper corrole. The cc-pVTZ basis set was used for Cu and N atoms, while cc-pVDZ was used for C and H. Density fitting is used in all calculations with the def2-TZVPP JKFIT basis set. The reference wavefunctions were determined using an active space including four electrons and five orbitals (4e,5o), (see section on the active space for a discussion of active space choice). Calculations for both the singlet and triplet states include state-averaging over two states (i.e., SA2-CASSCF and SA2-RASSCF).