Photosensitized Water Oxidation by Use of a Bioinspired Manganese Catalyst

Abstract

Manganificent potential: A dinuclear manganese catalyst contains metal centers that are coordinated by a central phenolate, with adjoining imidazole and carboxylate groups, which are all important functionalities in the natural oxygen‐evolving center. The complex catalyzes the conversion of water to oxygen in the presence of a single‐electron oxidant [Ru(bpy)3]3+ (see picture, bpy=2,2′‐bipyridine, A=acceptor).

Quantum Chemical Modeling of Homogeneous Water Oxidation Catalysis

“…Liao et al also performed aD FT investigation on the reaction mechanism of water oxidation mediated by ab ioinspired tetranuclear manganese complex, [71] which was developed by the Akermark group. [44] This complex has am ultidentatep lanar ligand for metal binding, and catalyzes water oxidation in a neutrala queous solution( phosphate buffer,p H7.2) by using [Ru(bpy) 3 ] 3 + (bpy = 2,2'-bipyridine) as as ingle-electronc hemical oxidant. Kinetic studies gave aT ON of about 25 and aT OF of 0.027 s…”

Water Oxidation Catalysts Constructed by Biorelevant First-row Metal Complexes

“…A breakthrough to overcome such limitations of manganese-based catalysts was made by ¡kermark et al in 2011. 29 They prepared a newly designed pentadentate ligand (H 5 L1) containing imidazole and carboxylate moieties and constructed the dimanganese complex, [Mn 2 II,III (H 2 L1)(OAc)(OMe)] (8, Figure 3). The significant features of this ligand scaffold are the negatively charged carboxylate groups that dramatically reduce the redox potentials of the metal center.…”

Photocatalytic Water Oxidation by a Mixed‐Valent MnIII3MnIVO3 Manganese Oxo Core that Mimics the Natural Oxygen‐Evolving Center

“…Turnover frequency (TOF) values per manganese center of up to 0.71 10 À3 s À1 were calculated: these values are significantly higher than those generally observed for bulk Mn oxides, which are on the order of 10 À5 s À1 (Tables S2 and S3). [18,19] Control experiments using an equimolar amount of Mn 2+ ions, which were introduced as MnSO 4 ·H 2 O, led to negligible O 2 production (Table S2). Moreover, the FT-IR features of the solid material that was recovered after the reaction are reminiscent of the fingerprint of pristine Mn 4 POM (Figure S10).…”

“…Mn 4 POM is the first manganese-containing POM that is catalytically active towards photo-induced water oxidation. [19] XAS spectroscopy will be used in the future to study the Mn-based manifold. Further work will be dedicated to tune the composite ligand set to lower the overpotential and increase quantum efficiency with the perspective of developing a regenerative photoelectrochemical cell.…”