Electron transfer and hydrogen generation from a molecular dyad: platinum(ii) alkynyl complex anchored to [FeFe] hydrogenase subsite mimic

Abstract

A PS–Fe₂S₂ molecular dyad 1a directly anchoring a platinum(II) alkynyl complex to a Fe₂S₂ active site of a [FeFe] H₂ase mimic, and an intermolecular system of its reference complexes 1b and 2, have been successfully constructed. Time-dependence of H₂ evolution shows that PS–Fe₂S₂1a as well as complex 2 with 1b can produce H₂ in the presence of a proton source and sacrificial donor under visible light irradiation. Spectroscopic and electrochemical studies on the electron transfer event reveal that the reduced Fe^IFe⁰ species generated by the first electron transfer from the excited platinum(II) complex to the Fe₂S₂ active site in PS–Fe₂S₂1a and complex 2 with 1b is essential for photochemical H₂ evolution, while the second electron transfer from the excited platinum(II) complex to the protonated Fe^IFe⁰ species is thermodynamically unfeasible, which might be an obstacle for the relatively small amount of H₂ obtained by PS–Fe₂S₂ molecular dyads reported so far.