This d-orbital has also been shown to interact with the corrole π-system by overlapping with the π b 1 orbital in the saddled geometry. Therefore, the minimal active space includes the four Gouterman orbitals and the Cu d x 2 -y 2 orbital along with the corresponding electrons, denoted (4e,5o) (Figures and). Computations with a larger active space including 14 electrons and 15 orbitals, (14e,15o), have also been performed. Specifically, the four Gouterman orbitals, the five copper 3d orbitals, the correlating copper 4d orbitals, and a