Synthesis and Photophysical Study of a [NiFe] Hydrogenase Biomimetic Compound Covalently Linked to a Re-diimine Photosensitizer

Peter A. Summers, James A. Calladine, Fabio Ghiotto, Joe Dawson, Xue Z. Sun, Michelle L. Hamilton, Michael Towrie, E. Stephen Davies, Jonathan McMaster, Michael W. George, Martin Schröder

Research output: Journal PublicationReview articlepeer-review

16 Citations (Scopus)

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 × 107 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 × 108 M-1 s-1, kintra = 1.5 ± 0.1 × 105 s-1). For the analogous bimolecular system, only intermolecular electron transfer could be observed (kinter = 3.8 ± 0.5 × 109 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.

Original languageEnglish
Pages (from-to)527-536
Number of pages10
JournalInorganic Chemistry
Volume55
Issue number2
DOIs
Publication statusPublished - 19 Jan 2016

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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