The Cover Feature shows a virtual factory in which the properties of cobalt corroles can be modulated by appropriate choice of the apical ligands and corrole substituents, which in turn determine the ligand field splitting of the cobalt 3d orbitals and the ease of oxidation of the corrole. Weak axial ligands and electron-donating substituents favour an open-shell singlet ground state while strong axial ligands and electron-withdrawing substituents favour a closed-shell singlet. Density functional and wavefunction theories allow rationalization and prediction of the electronic structure of these complexes. More information can be found in the Research Article by N. I. Neuman.

DFT calculations predict for many cobalt(III) corroles a broken-symmetry open-shell ground state, while CASSCF provides a more nuanced description where the weights of different closed- and open-shell configurations can be obtained. The S−T gap depends on the ligand field produced by the apical ligands and the ease of oxidation of the corroles.

Abstract

Cobalt(III) corroles are the most commonly studied types of metallocorroles, yet the details of their electronic structure, ground spin states and place of redox events are not always straightforward. Corroles are redox active, potentially non-innocent ligands, and it has been found through various experimental and computational techniques, that the innocent or non-innocent behavior is modulated by the apical ligands bound to the cobalt center. In this work, we aim to analyze the effect of corrole substituents and number and type of apical ligands on the electronic structure of cobalt corroles through density functional and wavefunction theories, and to determine the relative energies between closed- and open-shell states. We further perform preliminary analyses on the place of electron abstraction upon oxidation and on the effect of the corrole and apical ligands on the cobalt ligand field splittings. We find that both ligand field and electron-donating or withdrawing effects determine the relative energies of open-shell and closed shell singlet states.