There is intense activity in the area of photoinduced water reduction to H2 using systems consisting of a chromophore, sacrificial reductant and catalyst. In some cases the chromophore and catalyst are covalently linked, as in complexes with a Ru(II) diimine chromophore and Rh(III) or Pt(II) catalyst.1,2 The Pt(II) catalysts often consist of coordination environments involving a bidentate or tridentate imine ligand and one or two monodentate ligands. There are also Pt(II) complexes that are visible light absorbing chromophores with lifetimes of hundreds or nanoseconds (or longer) with similar coordination environments. For example, [(tpy)Pt(II)OH]+ absorbs in the visible and has an excited state lifetime of 700 ns in CH3CN and reacts with electron donors in solution, but decomposes when reduced photochemically by sacrificial electron donors. Recently we have been exploring the photoredox reactivity of [(N^C^N)Pt(II)Cl] complexes in nonaqueous solvents. These complexes are strongly luminescent with high quantum yields and long excited state lifetimes and have been proposed as chromophores for OLEDs. Little work has been done on light induced redox reactions of these systems. In this presentation we will discuss the synthesis, photophysical behavior and photoredox reactivity of [(diPhNCN)PtCl] and [(diDMAPhNCN)PtCl] (diPhNCN = 1,5-(4-phenyl-pyrid-2-yl)benzene; diDMAPhNCN = 1,5-(4-(p-dimethylaminophenyl)-pyrid-2-yl)benzene) in DMF solution. The complexes differ in that [(diPhNCN)PtCl] has a metal-to-ligand charge transfer (MLCT) excited state while that of the diDMAPhNCN complex is an intra-ligand charge transfer (ILCT) state. Both complexes react with weak reductants upon photoexcitation and use of sacrificial reductants such as triethylamine results in generation of hydrogen from solutions containing water. Addition of mercury does not affect hydrogen production. Thus, the complexes serve as chromophores and catalysts. Mechanistic details are addressed by laser flash photolysis, electrocatalysis studies and spectroelectrochemistry. (1) Arachchige, S. M.; Brewer, K. J.; John Wiley & Sons Ltd.: 2010, p 143-171. (2) Ozawa, H.; Haga, M.; Sakai, K. J. Am. Chem. Soc. 2006, 128, 4926-4927.

Photoredox reactions of Pt(II) o-metalated bis-pyridylbenzene complexes: Photoreduction and H2 generation in chromophore-sacrificial donor systems

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.