Low-Energy States of Manganese–Oxo Corrole and Corrolazine: Multiconfiguration Reference ab Initio Calculations
journal contributionposted on 02.04.2012, 00:00 by Hailiang Zhao, Kristine Pierloot, Ernie H. G. Langner, Jannie C. Swarts, Jeanet Conradie, Abhik Ghosh
Manganese(V)–oxo corrole and corrolazine have been studied with ab initio multiconfiguration reference methods (CASPT2 and RASPT2) and large atomic natural orbital (ANO) basis sets. The calculations confirm the expected singlet dδ2 ground states for both complexes and rule out excited states within 0.5 eV of the ground states. The lowest excited states are a pair of Mn(V) triplet states with dδ1dπ1 configurations 0.5–0.75 eV above the ground state. Manganese(IV)–oxo macrocycle radical states are much higher in energy, ≥1.0 eV relative to the ground state. The macrocyclic ligands in the ground states of the complexes are thus unambiguously ‘innocent’. The approximate similarity of the spin state energetics of the corrole and corrolazine complexes suggests that the latter macrocycle on its own does not afford any special stabilization for the MnVO center. The remarkable stability of an MnVO octaarylcorrolazine thus appears to be ascribable to the steric protection afforded by the β-aryl groups.