Dioxygen bound cobalt corroles

Abstract

Two cobalt–dioxygen adducts, [CoH₈]–O₂ and [CoCl₈]–O₂, chelated by electron-rich and electron-poor corroles, respectively, were isolated in solution. Characterization by resonance Raman (rR) and EPR spectroscopy, together with DFT analyses, point towards (corrole) cobalt(III)–O₂˙⁻ structures in both cases. The most significant insight was obtained from the Co–O and O–O stretching frequencies, which revealed that the Co–O bond in [CoH₈]–O₂ is somewhat stronger than in [CoCl₈]–O₂ and its O–O is weaker, but also that the differences are truly minute (8–10 cm⁻¹ for the O–O stretch). These conclusions are vital regarding the various applications that rely on efficient reduction of molecular oxygen. In particular, these kinds of cobalt complexes are perfectly suited for serving as electrocatalysts that may be tuned to operate at minimal overpotential without losing almost anything in terms of activity.