A polypyridyl Co(ii) complex-based water reduction catalyst with double H2 evolution sites. Issue 24 (10th November 2016)

• Record Type: Journal Article
• Authors: Wang, Junfei; Li, Chao; Zhou, Qianxiong; Wang, Weibo; Hou, Yuanjun; Zhang, Baowen; Wang, Xuesong
• Is Part Of: Catalysis science & technology. Volume 6:Issue 24(2016)
• Page Start: 8482
• Page End: 8489
• Publication Date: 2016-11-10
• Subjects: Catalysis -- Periodicals; 541.395
• DOI: 10.1039/c6cy01897a
• Languages: English
• ISSNs: 2044-4753

Abstract

Abstract : The unique coordination mode of Cl-TMPA and the double H2 evolution sites of [Co(Cl-TMPA)Cl2 ] provide a new strategy to design more effective WRCs. Abstract : A series of Co(ii ) complexes, Co(X-TMPA)Cl2 (X-TMPA = 1-(6-substituted-pyridin-2-yl)- N, N -bis(pyridin-2-ylmethyl)methane amine, X = Cl (1 ), Br (2 ), H (3 ), and CH3 (4 )), were synthesized and fully characterized. The crystal structures of2 and4 show that TMPA and CH3 -TMPA coordinate to the Co(ii ) center as tetradentate ligands, while Br-TMPA coordinates as a tridentate ligand, leaving the Br-substituted pyridyl group in the second coordination sphere. All of the complexes are efficient photocatalytic H2 evolution catalysts in CH3 CN/H2 O (9/1) using [Ir(ppy)2 (dtbpy)]Cl (ppy = 2-phenylpyridine, dtbpy = 4, 4′-di- tert -butyl-2, 2′-bipyridine) as the photosensitizer (PS) and triethylamine (TEA) as the sacrificial electron donor. During 6 h irradiation, the turnover numbers (TONs) of1 and2 reached 20 000, remarkably higher than those of3 and4 . These high photocatalytic activities may be attributed to the pendent Cl/Br-substituted pyridyl group, which serves as a proton and electron relay to facilitate proton reduction at the Co center. Interestingly and importantly, it was found that the Cl-substituted pyridyl group of1 may catalyze H2 evolution itself by electrocatalytic proton reduction reactions, endowing1 with double catalytic sites for proton reduction. The unique coordination mode of Cl/Br-TMPA and the double catalytic H2 evolution sites of1 provide a new strategy to design more effective WRCs.