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- Title
Experimental and Theoretical Study of Photochemical Hydrogen Evolution Catalyzed by Paddlewheel‐Type Dirhodium Complexes with Electron Withdrawing Carboxylate Ligands.
- Authors
Kataoka, Yusuke; Yano, Natsumi; Kohara, Yoshihiro; Tsuji, Takeshi; Inoue, Satoshi; Kawamoto, Tatsuya
- Abstract
The photochemical hydrogen evolution capabilities of paddlewheel‐type dirhodium complexes with electron withdrawing carboxylates, [Rh2(O2CR)4(H2O)2] (R=CF3 and CCl3 for [2(H2O)2] and [3(H2O)2], respectively), were investigated and compared with that of [Rh2(O2CCH3)4(H2O)2], ([1(H2O)2]), which is the most effective hydrogen evolution catalyst (HEC) among rhodium complexes developed to date. Artificial photosynthesis (AP) systems with [2(H2O)2] or [3(H2O)2], [Ir(ppy)2(bpy)](PF6), and TEA showed highly efficient hydrogen evolution activities; the turnover numbers (TON) of hydrogen evolution per Rh by the AP systems with [2(H2O)2] and [3(H2O)2] after 12 h of photo‐irradiation were 3334 and 3138, respectively. Experimental analyses and density functional theory (DFT) calculations afforded valuable insight into the hydrogen evolution mechanism of paddlewheel‐type dirhodium complexes; (i) hydrogen evolution activities of the AP systems with [2(H2O)2] and [3(H2O)2] were slightly lower than that of the AP system with [1(H2O)2] despite one‐electron reduction potentials of [2(H2O)2] and [3(H2O)2] lie on the anode side than that of [1(H2O)2], and (ii) two different pathways exist during the early stages in the photochemical hydrogen evolution by [2(H2O)2] and [3(H2O)2]. Moreover, the relative free‐energy diagrams estimated by DFT calculations clarified the energy profiles of the mechanism including the rate‐determining steps of the hydrogen evolution by [1(H2O)2]−[3(H2O)2].
- Subjects
CARBOXYLATES; HYDROGEN evolution reactions; ARTIFICIAL photosynthesis; DENSITY functional theory; TURNOVER frequency (Catalysis); LIGANDS (Chemistry); HYDROGEN
- Publication
ChemCatChem, 2019, Vol 11, Issue 24, p6218
- ISSN
1867-3880
- Publication type
Article
- DOI
10.1002/cctc.201901534