title: Protonation of [FeFe]-hydrogenase sub-site analogues: revealing mechanism using FTIR stopped-flow techniques.
abstract: The formation of transient metal hydride(s) at the metallo-sulfur active sites of [FeFe]-hydrogenase is implicated in both hydrogen evolution and uptake reactions. Stopped-flow spectroscopic techniques can provide insight into the reactivity patterns of model {2Fe2S} sub-sites towards protons, and this information contributes to understanding the nature of the biological systems. In this study we have focussed on the influence of the nature of the bridging dithiolate ligand in influencing the kinetics and activation energy parameters for protonation in synthetic sub-sites including Fe2{micro-[S(CH2)(n)S]}(CO)4(PMe3)2 [n = 2, ethane-1,2-dithiolate (edt) or n = 3, propane-1,3-dithiolate (pdt)], Fe2[(micro-SCH2)2NH](CO)4(PMe3)2 and (NEt4)2{Fe2[(micro-SCH2)2NH](CO)4(CN)2}. Notably we find that (i) the presence of a nitrogen in the dithiolate bridge does not accelerate metal-metal bond protonation, and that (ii) immobilisation of (NEt4)2[Fe2(micro-pdt)(CO)4(CN)2] in a polymer matrix stabilises otherwise short-lifetime protonation products.
authors.affiliation: Energy Materials Laboratory, School of Chemistry, University of East Anglia, Norwich NR4 7TJ, United Kingdom.
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Wright
authors.forename: Lee
authors.initials: L
authors.lastname: Webster
authors.forename: Ausra
authors.initials: A
authors.lastname: Jablonskyte
authors.forename: Pei Meng
authors.initials: PM
authors.lastname: Woi
authors.forename: Saad K
authors.initials: SK
authors.lastname: Ibrahim
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Pickett
mesh_terms: D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008958:Models, Molecular; D011522:Protons; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*
chemical_list: D007506:Iron-Sulfur Proteins; D011522:Protons; C118830:iron hydrogenase; D006864:Hydrogenase