title: Biomimetic model for [FeFe]-hydrogenase: asymmetrically disubstituted diiron complex with a redox-active 2,2'-bipyridyl ligand.
abstract: [FeFe]-hydrogenases feature a unique active site in which the primary catalytic unit is directly coordinated via a bridging cysteine thiolate to a secondary, redox active [4Fe4S] unit. The goal of this study was to evaluate the impact of a bidentate, redox non-innocent ligand on the electrocatalytic properties of the (μ-S(CH(2))(3)S)Fe(2)(CO)(4)L(2) family of [FeFe]-hydrogenase models as a proxy for the iron-sulfur cluster. Reaction of the redox non-innocent ligand 2,2'-bipyridyl (bpy) with (μ-S(CH(2))(3)S)Fe(2)(CO)(6) leads to substitution of two carbonyls to form the asymmetric complex (μ-S(CH(2))(3)S)Fe(2)(CO)(4)(κ(2)-bpy) which was structurally characterized by single crystal X-ray crystallography. This complex can be protonated by HBF(4)·OEt(2) to form a bridging hydride. Furthermore, electrochemical investigation shows that, at slow scan rates, the complex undergoes a two electron reduction at -2.06 V vs. Fc(+)/Fc that likely involves reduction of both the bpy ligand and the metal. Electrocatalytic reduction of protons is observed in the presence of three distinct acids of varying strengths: HBF(4)·OEt(2), AcOH, and p-TsOH. The catalytic mechanism depends on the strength of the acid.
authors.affiliation: Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ, USA.
authors.forename: Souvik
authors.initials: S
authors.lastname: Roy
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Groy
authors.forename: Anne K
authors.initials: AK
authors.lastname: Jones
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry* / Q000378:metabolism; D040761:Biomimetic Materials / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D056831:Coordination Complexes / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D018360:Crystallography, X-Ray; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010084:Oxidation-Reduction; D013056:Spectrophotometry, Ultraviolet; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D056831:Coordination Complexes; D007506:Iron-Sulfur Proteins; D008024:Ligands; D015082:2,2'-Dipyridyl; C118830:iron hydrogenase; D006864:Hydrogenase