Design Considerations for a System for Photocatalytic Hydrogen Production from Water Employing Mixed-Metal Photochemical Molecular Devices for Photoinitiated Electron Collection

Supramolecular complexes coupling Ru(II) or Os(II) polyazine light absorbers through bridging ligands to Rh(III) or Ir(III) allow the study of factors impacting photoinitiated electron collection and multielectron water reduction to produce hydrogen. The [{(bpy)2Ru(dpb)}2IrCl2](PF6)5 system represents the first photoinitiated electron collector in a molecular system (bpy = 2,2′-bipyridine, dpb = 2,3-bis(2-pyridyl)benzoquinoxaline). The [{(bpy)2Ru(dpp)}2RhCl2](PF6)5 system represents the first photoinitiated electron collector that affords photochemical hydrogen production from water in the presence of an electron donor, N,N-dimethylaniline (dpp = 2,3-bis(2-pyridyl)pyrazine). The complexes [{(bpy)2Ru(dpp)}2RhCl2](PF6)5, [{(bpy)2Ru(dpp)}2RhBr2](PF6)5, [{(phen)2Ru(dpp)}2RhCl2](PF6)5, [{(bpy)2Os(dpp)}2RhCl2](PF6)5, [{(tpy)RuCl(dpp)}2RhCl2](PF6)3, [{(tpy)OsCl(dpp)}2RhCl2](PF6)3, and [{(bpy)2Ru(dpb)}2IrCl2](PF6)5 are herein evaluated with respect to their functioning as hydrogen photocatalysts (tpy = 2,2′:6′,2′...