Reversible Visible-Light Photooxidation of an Oxomanganese Water-Oxidation Catalyst Covalently Anchored to TiO2 Nanoparticles

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• 作者：Gonghu Li ; Eduardo M. Sproviero ; William R. McNamara ; Robert C. Snoeberger ; III ; Robert H. Crabtree ; Gary W. Brudvig ; Victor S. Batista
• 刊名：Journal of Physical Chemistry B
• 出版年：2010
• 出版时间：November 18, 2010
• 年：2010
• 卷：114
• 期：45
• 页码：14214-14222
• 全文大小：330K
• 年卷期：v.114,no.45(November 18, 2010)
• ISSN：1520-5207

文摘

Several polynuclear transition-metal complexes, including our own dinuclear di-μ-oxo manganese compound [H₂O(terpy)Mn^III(μ-O)₂Mn^IV(terpy)H₂O](NO₃)₃ (1, terpy = 2,2′:6′,2′′-terpyridine), have been reported to be homogeneous catalysts for water oxidation. This paper reports the covalent attachment of 1 onto nanoparticulate TiO₂ surfaces using a robust chromophoric linker L. L, a phenylterpy ligand attached to a 3-phenyl-acetylacetonate anchoring moiety via an amide bond, absorbs visible light and leads to photoinduced interfacial electron transfer into the TiO₂ conduction band. We characterize the electronic and structural properties of the 1−L−TiO₂ assemblies by using a combination of methods, including computational modeling and UV−visible, IR, and EPR spectroscopies. We show that the Mn(III,IV) state of 1 can be reversibly advanced to the Mn(IV,IV) state by visible-light photoexcitation of 1−L−TiO₂ nanoparticles (NPs) and recombines back to the Mn(III,IV) state in the dark, in the absence of electron scavengers. Our findings also indicate that a high degree of crystallinity of the TiO₂ NPs is essential for promoting photooxidation of the adsorbates by photoinduced charge separation when the TiO₂ NPs serve as electron acceptors in artificial photosynthetic assemblies. The reported results are particularly relevant to the development of photocatalytic devices for oxidation chemistry based on inexpensive materials (e.g., TiO₂ and Mn complexes) that are robust under aqueous and oxidative conditions.