Photocatalytic Water Oxidation by a Mixed‐Valent Mn^III₃Mn^IVO₃ Manganese Oxo Core that Mimics the Natural Oxygen‐Evolving Center

Abstract

The functional core of oxygenic photosynthesis is in charge of catalytic water oxidation by a multi-redox Mn(III)/Mn(IV) manifold that evolves through five electronic states (S(i), where i=0-4). The synthetic model system of this catalytic cycle and of its S0→S4 intermediates is the expected turning point for artificial photosynthesis. The tetramanganese-substituted tungstosilicate [Mn(III)3Mn(IV)O3(CH3COO)3(A-α-SiW9O34)](6-)(Mn4POM) offers an unprecedented mimicry of the natural system in its reduced S0 state; it features a hybrid organic-inorganic coordination sphere and is anchored on a polyoxotungstate. Evidence for its photosynthetic properties when combined with [Ru(bpy)3](2+) and S2O8(2-) is obtained by nanosecond laser flash photolysis; its S0→S1 transition within milliseconds and multiple-hole-accumulating properties were studied. Photocatalytic oxygen evolution is achieved in a buffered medium (pH 5) with a quantum efficiency of 1.7%.

Photosystem II Like Water Oxidation Mechanism in a Bioinspired Tetranuclear Manganese Complex

“…To increase the TON of the catalyst, future ligands have to be designed to avoid water attack on the ligand scaffolds and related side reactions that lead to catalyst deactivation. Interestingly, a tetranuclear Mn water oxidation catalyst has very recently been synthesized using inorganic tungstosilicate as a ligand, 45 in which the ligand modification by water attack or oxidation can be avoided. Figure S43, Supporting Information) is endergonic by 22.9 kcal mol −1 , and the barrier for O−O bond formation was found to be 24.7 kcal mol −1 , which is 2.3 kcal mol −1 higher than that from 9.…”

Away from TiO2: A critical minireview on the developing of new photocatalysts for degradation of contaminants in water

“…Large part of the few published manuscripts describes measurements that were performed in the context of studying water splitting (actually photoinduced hydrogen evolution). Examples include the use of the mixed-valence compound Mn(III) 3 Mn(IV)O 3 that mimicked a biological oxygenevolving center [83], and the study of complexes based on Keggin structures, such as [Co 4 (H 2 O) 2 (a-PW 9 O 34 ) 2 ] 10 [84]. The number of manuscripts using LFP of inorganic photocatalysts in the context of remediation of water and air is in particular small.…”

Valence state heterojunction Mn3O4/MnCO3: Photo and thermal synergistic catalyst

“…Bonchio et al found the functional core of oxygenic photosynthesis was in charge of catalytic water oxidation by a multi-redox Mn Ш /Mn IV manifold which is the expected turning point for artificial photosynthesis [5,6].…”

“…As we known, biochemical function of all life on our earth is interrelated with the valence change of manganese, especially in photosynthesis [5]. Bonchio et al found the functional core of oxygenic photosynthesis was in charge of catalytic water oxidation by a multi-redox Mn Ш /Mn IV manifold which is the expected turning point for artificial photosynthesis [5,6].…”