Electronic Structure of Manganese Corroles Revisited: X-ray Structures, Optical and X-ray Absorption Spectroscopies, and Electrochemistry as Probes of Ligand Noninnocence

Presented herein is a detailed multitechnique investigation of ligand noninnocence in S = 3/2 manganese corrole derivatives at the formal MnIV oxidation state. The Soret maxima of Mn[TpXPC]Cl (TpXPC = meso-tris(p-X-phenyl)corrole, where X = CF3, H, Me, and OMe) were found to red-shift over a range of 37 nm with increasing electron-donating character of X. For Mn[TpXPC]Ph, in contrast, the complex Soret envelopes were found to be largely independent of X. These observations suggested a noninnocent corrole•2–-like ligand for the MnCl complexes and an innocent corrole3– ligand for the MnPh complexes. Single-crystal X-ray structures of three Mn[TpXPC]Cl complexes revealed skeletal bond-length alternations indicative of a noninnocent corrole, while no such alternation was observed for Mn[TpOMePC]Ph. B3LYP density functional theory (DFT) calculations on Mn[TPC]Cl yielded strong spatial separation of the α and β spin densities, consistent with an antiferromagnetically coupled MnIII-corrole•2– description. By com...