title: Synthesis and Photophysical Study of a [NiFe] Hydrogenase Biomimetic Compound Covalently Linked to a Re-diimine Photosensitizer.
abstract: The synthesis, photophysics, and photochemistry of a linked dyad ([Re]-[NiFe2]) containing an analogue ([NiFe2]) of the active site of [NiFe] hydrogenase, covalently bound to a Re-diimine photosensitizer ([Re]), are described. Following excitation, the mechanisms of electron transfer involving the [Re] and [NiFe2] centers and the resulting decomposition were investigated. Excitation of the [Re] center results in the population of a diimine-based metal-to-ligand charge transfer excited state. Reductive quenching by NEt3 produces the radically reduced form of [Re], [Re](-) (kq = 1.4 ± 0.1 × 10(7) M(-1) s(-1)). Once formed, [Re](-) reduces the [NiFe2] center to [NiFe2](-), and this reduction was followed using time-resolved infrared spectroscopy. The concentration dependence of the electron transfer rate constants suggests that both inter- and intramolecular electron transfer pathways are involved, and the rate constants for these processes have been estimated (kinter = 5.9 ± 0.7 × 10(8) M(-1) s(-1), kintra = 1.5 ± 0.1 × 10(5) s(-1)). For the analogous bimolecular system, only intermolecular electron transfer could be observed (kinter = 3.8 ± 0.5 × 10(9) M(-1) s(-1)). Fourier transform infrared spectroscopic studies confirms that decomposition of the dyad occurs upon prolonged photolysis, and this appears to be a major factor for the low activity of the system toward H2 production in acidic conditions.
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.|Department of Chemical and Environmental Engineering, The University of Nottingham Ningbo China , Ningbo 315100, China.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Summers
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: James A
authors.initials: JA
authors.lastname: Calladine
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Fabio
authors.initials: F
authors.lastname: Ghiotto
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Joe
authors.initials: J
authors.lastname: Dawson
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Xue-Z
authors.initials: XZ
authors.lastname: Sun
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.|Dynamic Structural Science Consortium, Research Complex at Harwell , Didcot, Oxfordshire OX11 0FA, United Kingdom.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Hamilton
authors.affiliation: Central Laser Facility, Research Complex at Harwell, Science and Technology Facilities Council, Rutherford Appleton Laboratory , Harwell Oxford, Didcot, Oxfordshire OX11 0QX, United Kingdom.
authors.forename: Michael
authors.initials: M
authors.lastname: Towrie
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: E Stephen
authors.initials: ES
authors.lastname: Davies
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.
authors.forename: Jonathan
authors.initials: J
authors.lastname: McMaster
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.|Department of Chemical and Environmental Engineering, The University of Nottingham Ningbo China , Ningbo 315100, China.
authors.forename: Michael W
authors.initials: MW
authors.lastname: George
authors.affiliation: School of Chemistry, The University of Nottingham , University Park, Nottingham NG7 2RD, United Kingdom.|School of Chemistry, University of Manchester , Manchester M13 9PL, United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Schröder
mesh_terms: D000588:Amines / Q000737:chemistry; D032701:Biomimetics; D004563:Electrochemistry; D006864:Hydrogenase / Q000138:chemical synthesis* / Q000737:chemistry; D010084:Oxidation-Reduction; D017319:Photosensitizing Agents / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000588:Amines; D017319:Photosensitizing Agents; D012211:Rhenium; C043296:nickel-iron hydrogenase; D006864:Hydrogenase