Using the occupation numbers from RASSCF(36e,34o) reported in Figure , the EBO between the ligand π b 1 orbital and the d x 2 -y 2 orbital is 0.435. This corresponds to 56.5% radical character in the unfunctionalized copper corrole, consistent with previous studies and supporting the assignment of the complex as neither purely Cu(II) or Cu(III). For the triphenyl copper corrole, the EBO is 0.465 corresponding to 53.5% radical character.