Homogeneous Photocatalytic Water Oxidation with a Dinuclear CoIII–Pyridylmethylamine Complex

Tomoya Ishizuka†, Atsuko Watanabe†, Hiroaki Kotani†, Dachao Hong†, Kenta Satonaka†, Tohru Wada‡, Yoshihito Shiota§, Kazunari Yoshizawa§⊥, Kazuaki Ohara¶, Kentaro Yamaguchi¶, Satoshi Kato∥, Shunichi Fukuzumi*∥⧫∞, and Takahiko Kojima*†

† Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8571, Japan

‡ Department of Chemistry, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 171-8501, Japan

§ Institute for Materials Chemistry and Engineering, Kyushu University, Motooka, Nishi-ku, Fukuoka 819-0395, Japan

⊥ Elements Strategy Initiative for Catalysts & Batteries, Kyoto University, Nishi-ku, Kyoto 615-8520, Japan

¶ Faculty of Pharmaceutical Science at Kagawa Campus, Tokushima Bunri University, 1314-1 Shido, Sanuki, Kagawa 769-2193, Japan

∥ Department of Material and Life Science, Graduate School of Engineering, Osaka University, and ALCA, Japan Science and Technology Agency, Suita, Osaka 565-0871, Japan

⧫ Faculty of Science and Technology, Meijo University, ALCA and SENTAN, Japan Science and Technology Agency (JST), Tempaku, Nagoya, Aichi 468-8502, Japan

∞ Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Korea

Inorg. Chem., Article ASAP

DOI: 10.1021/acs.inorgchem.5b02336

Publication Date (Web): January 21, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/10.1021/acs.inorgchem.5b02336

Abstract

A bis-hydroxo-bridged dinuclear CoIII-pyridylmethylamine complex (1) was synthesized and the crystal structure was determined by X-ray crystallography. Complex 1 acts as a homogeneous catalyst for visible-light-driven water oxidation by persulfate (S2O82–) as an oxidant with [RuII(bpy)3]2+ (bpy = 2,2′-bipyridine) as a photosensitizer affording a high quantum yield (44%) with a large turnover number (TON = 742) for O2 formation without forming catalytically active Co-oxide (CoOx) nanoparticles. In the water-oxidation process, complex 1 undergoes proton-coupled electron-transfer (PCET) oxidation as a rate-determining step to form a putative dinuclear bis-μ-oxyl CoIII complex (2), which has been suggested by DFT calculations. Catalytic water oxidation by 1 using [RuIII(bpy)3]3+ as an oxidant in a H216O and H218O mixture was examined to reveal an intramolecular O–O bond formation in the two-electron-oxidized bis-μ-oxyl intermediate, prior to the O2 evolution.

They report about Co(III)-pyridylmethylamine complex which has high catalytic activity for water oxidation under photoirradiation.
Although there are few examples showing sufficient stability under photoirradiation, this complex keep catalytic ability in reaction.
By isotope-labeling experiments using 18O, intramolecular, no intermolecular O-O bond formation is occurred.