Copper corroles: the question of noninnocence.

In this paper, the results are presented from a comparative study of the electronic and geometric structure of copper correles by means of either density functional theory (DFT, using both pure and hybrid functionals) and multiconfigurational ab initio methods, starting from either a complete active space (CASSCF) or restricted active space (RASSCF) reference wave function and including dynamic correlation by means of second-order perturbation theory (CASPT2/RASPT2). DFT geometry optimizations were performed for the lowest singlet and triplet states of copper corrole, both unsubstituted and meso-substituted with three phenyl groups. The effect of saddling on the electronic structure was investigated by comparing the results obtained for planar (C2v) and saddled (C2) structures. With DFT, the origin of the saddling distortion is found to be dependent on the applied functional: covalent Cu 3d−corrole π interactions with pure functionals (BP86, OLYP), antiferromagnetic exchange coupling between an electron i...