title: Hydrophilic Quaternary Ammonium-Group-Containing [FeFe]-Hydrogenase Models: Synthesis, Structures, and Electrocatalytic Hydrogen Production.
abstract: The first quaternary ammonium-group-containing [FeFe]-hydrogenase models [(μ-PDT)Fe2(CO)4{κ2-(Ph2P)2N(CH2)2NMe2BzBr}] (2; PDT=propanedithiolate) and [(μ-PDT)Fe2(CO)4{μ-(Ph2P)2N(CH2)2NMe2BzBr}] (4) have been prepared by the quaternization of their precursors [(μ-PDT)Fe2(CO)4{κ2-(Ph2P)2N(CH2)2NMe2}] (1) and [(μ-PDT)Fe2(CO)4{μ-(Ph2P)2N(CH2)2NMe2}] (3) with benzyl bromide in high yields. Although new complexes 1-4 have been fully characterized by spectroscopic and X-ray crystallographic studies, the chelated complexes 1 and 2 converted into their bridged isomers 3 and 4 at higher temperatures, thus demonstrating that these bridged isomers are thermodynamically favorable. An electrochemical study on hydrophilic models 2 and 4 in MeCN and MeCN/H2O as solvents indicates that the reduction potentials are shifted to less-negative potentials as the water content increases. This outcome implies that both 2 and 4 are more easily reduced in the mixed MeCN/H2O solvent than in MeCN. In addition, hydrophilic models 2 and 4 act as electrocatalysts and achieve higher icat/ipvalues and turnover numbers (TONs) in MeCN/H2O as a solvent than in MeCN for the production of hydrogen from the weak acid HOAc.
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China. lcsong@nankai.edu.cn.|Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Nankai University, Tianjin, 300071, P.R. China. lcsong@nankai.edu.cn.
authors.forename: Li-Cheng
authors.initials: LC
authors.lastname: Song
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Yong-Xiang
authors.initials: YX
authors.lastname: Wang
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Xu-Kang
authors.initials: XK
authors.lastname: Xing
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Shu-Da
authors.initials: SD
authors.lastname: Ding
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Long-Duo
authors.initials: LD
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Xu-Yong
authors.initials: XY
authors.lastname: Wang
authors.affiliation: Department of Chemistry, State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin, 300071, P.R. China.
authors.forename: Hong-Tao
authors.initials: HT
authors.lastname: Zhang
keywords: electrocatalysis; hydrogen; iron; metalloenzymes; model complexes