title: A reversible proton relay process mediated by hydrogen-bonding interactions in [FeFe]hydrogenase modeling.
abstract: A reversible and temperature-dependent proton-relay process is demonstrated for a Fe2 complex possessing a terminal thiolate in the presence of nitrogen-based acids. The terminal sulfur site (S(t) ) of the complex forms a hydrogen-bond interaction with N,N-dimethylanilinium acid at 183 K. The Fe2 core, instead, is protonated to generate a bridging hydride at 298 K. Reversibility is observed for the tautomerization between the hydrogen-bonded pair and the Fe-hydride species. X-ray structural analysis of the hydrogen-bonded species at 193 K reveals a short N(H)⋅⋅⋅S(t) contact. Employment of pyridinium acid also results in similar behavior, with reversible proton-hydride interconversion. DFT investigation of the proton-transfer pathways indicates that the pKa value of the hydrogen-bonded species is enhanced by 3.2 pKa units when the temperature is decreased from 298 K to 183 K.
authors.affiliation: Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan).|Molecular Science and Technology Program, TIGP, Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan).|Department of Chemistry, National Tsing Hua University, Hsinchu 300 (Taiwan).
authors.forename: Kai-Ti
authors.initials: KT
authors.lastname: Chu
authors.affiliation: Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan).
authors.forename: Yu-Chiao
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan).
authors.forename: Yi-Lan
authors.initials: YL
authors.lastname: Huang
authors.affiliation: Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan).
authors.forename: Cheng-Huey
authors.initials: CH
authors.lastname: Hsu
authors.affiliation: Instrumentation Center, National Taiwan University, Taipei 106 (Taiwan).
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.affiliation: Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan). mhchiang@chem.sinica.edu.tw.|Molecular Science and Technology Program, TIGP, Institute of Chemistry, Academia Sinica, Nankang, Taipei 115 (Taiwan). mhchiang@chem.sinica.edu.tw.
authors.forename: Ming-Hsi
authors.initials: MH
authors.lastname: Chiang
keywords: S ligands; [FeFe]hydrogenase; hydrogen bonds; iron; proton transfer