title: Further Investigation of a Nickel-Based Homogeneous Water Oxidation Catalyst with Two cis Labile Sites.
abstract: The reaction of N,N'-dimethyl-N,N'-bis(pyridin-2-ylmethyl)-1,2-diaminoethane ligand (L) with Ni(ClO4)2 ⋅6 H2O generated a complex of [NiL(H2O)2](ClO4)2 (1) with two cis labile sites occupied by two coordinated H2O molecules, which can homogeneously electrocatalyze water oxidation in pH 6.5 acetate (OAc(-)) buffer at room temperature. The catalytic mechanism was studied by electrochemical experiments and density functional theory calculations to elucidate the following steps: (a) one of two water molecules in 1 is exchanged by OAc(-) to generate [NiL(H2O)(OAc)](+) when dissolved in OAc(-) buffer, (b) Ni(II) is directly oxidized to Ni(IV) and OAc(-) is replaced with OH(-) to form [Ni(IV) L(OH)2 ](2+), and (c) a peroxide intermediate is formed through the intramolecular O-O coupling in the presence of OAc(-), which undergoes further oxidation to release O2.
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, 510275, China.
authors.forename: Gang-Yi
authors.initials: GY
authors.lastname: Luo
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, 510275, China.
authors.forename: Hai-Hua
authors.initials: HH
authors.lastname: Huang
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, 510275, China.
authors.forename: Jia-Wei
authors.initials: JW
authors.lastname: Wang
authors.affiliation: MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry and Chemical Engineering, Sun Yat-Sen University, Guangzhou, 510275, China. lutongbu@mail.sysu.edu.cn.
authors.forename: Tong-Bu
authors.initials: TB
authors.lastname: Lu
mesh_terms: D002384:Catalysis; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D014867:Water / Q000737:chemistry*
chemical_list: D014867:Water; D009532:Nickel
keywords: cis labile sites; electrocatalysis; homogeneous; nickel complex; water oxidation catalyst