title: Photochemical dihydrogen production using an analogue of the active site of [NiFe] hydrogenase.
abstract: Photoproduction of dihydrogen (H2) by a low molecular weight analogue of the active site of [NiFe] hydrogenase has been investigated by reduction of the [NiFe2] cluster, 1, by a photosensitier PS (PS = [ReCl(CO)3(bpy)] or [Ru(bpy)3][PF6]2). Reductive quenching of the (3)MLCT excited state of the photosensitizer by NEt3 or N(CH2CH2OH)3 (TEOA) generates PS(•-), and subsequent intermolecular electron transfer to 1 produces the reduced anionic form of 1. Time-resolved infrared spectroscopy (TRIR) has been used to probe the intermediates throughout the reduction of 1 and subsequent photocatalytic H2 production from [HTEOA][BF4], which was monitored by gas chromatography. Two structural isomers of the reduced form of 1 (1a(•-) and 1b(•-)) were detected by Fourier transform infrared spectroscopy (FTIR) in both CH3CN and DMF (dimethylformamide), while only 1a(•-) was detected in CH2Cl2. Structures for these intermediates are proposed from the results of density functional theory calculations and FTIR spectroscopy. 1a(•-) is assigned to a similar structure to 1 with six terminal carbonyl ligands, while calculations suggest that in 1b(•-) two of the carbonyl groups bridge the Fe centers, consistent with the peak observed at 1714 cm(-1) in the FTIR spectrum for 1b(•-) in CH3CN, assigned to a ν(CO) stretching vibration. Formation of 1a(•-) and 1b(•-) and production of H2 was studied in CH3CN, DMF, and CH2Cl2. Although the more catalytically active species (1a(•-) or 1b(•-)) could not be determined, photocatalysis was observed only in CH3CN and DMF.
authors.affiliation: School of Chemistry, University of Nottingham , Nottingham NG7 2RD, United Kingdom.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Summers
authors.forename: Joe
authors.initials: J
authors.lastname: Dawson
authors.forename: Fabio
authors.initials: F
authors.lastname: Ghiotto
authors.forename: Magnus W D
authors.initials: MW
authors.lastname: Hanson-Heine
authors.forename: Khuong Q
authors.initials: KQ
authors.lastname: Vuong
authors.forename: E Stephen
authors.initials: ES
authors.lastname: Davies
authors.forename: Xue-Z
authors.initials: XZ
authors.lastname: Sun
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Besley
authors.forename: Jonathan
authors.initials: J
authors.lastname: McMaster
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.forename: Martin
authors.initials: M
authors.lastname: Schröder
mesh_terms: D004563:Electrochemistry; D006859:Hydrogen / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*; D055668:Photochemical Processes; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D006859:Hydrogen; C043296:nickel-iron hydrogenase; D006864:Hydrogenase