Structural and Spectroscopic Characterization of Reaction Intermediates Involved in a Dinuclear Co-Hbpp Water Oxidation Catalyst

Gimbert-Suriñach, C.; Moonshiram, D.; Francàs, L.; Planas, N.; Bernales, V.; Bozoglian, F.; Guda, A.; Mognon, L.; López, I.;Asmaul Hoque, M.; Gagliardi, L.; Cramer, C. J.; Llobet, A.
J. Am. Chem. Soc. 2016, 138, 15291 (doi:10.1021/jacs.6b08532).

An end-on superoxido complex with formula {[Co^III(OH₂)(trpy)][Co^III(OO•)(trpy)](μ-bpp)}⁴⁺, 3⁴⁺, (bpp^– is bis-2-pyridyl-3,5-pyrazolate; trpy is 2,2';6':2"-terpyridine) has been characterized by resonance Raman, electron paramagnetic resonance and x-ray absorption spectroscopies. These results together with on-line mass spectrometry experiments using ¹⁷O and ¹⁸O isotopically labeled compounds prove that this compound is a key intermediate of the water oxidation reaction catalyzed by the peroxido bridging complex {[Co^III(trpy)]₂(μ-bpp)(μ-OO)}³⁺, 1³⁺. Density Functional Theory calculations agree and complement the experimental data, and offer a complete description of the transition states and intermediates involved in the catalytic cycle.