Novel photophysical properties of gold selenide complexes:: Photogeneration of singlet oxygen by [Au18Se8(dppe)6]Br2 and near-infrared photoluminescence of [Au10Se4(dpppe)4]Br2

The photoluminescence (PL) properties of several recently synthesized ligand-stabilized polynuclear gold(I) selenide complexes were investigated. [Au18Se8(dppe)(6)]Br-2 {dppe = bis(diphenylphosphanyl) ethane}, (I) is distinguished by the bright-red long-lived PL (phosphorescence) in the solid state, photosensitization of singlet oxygen, O-1(2), in solution, and high photostability. The quantum yield of PL, phi(PL), is (7.5 +/- 0.5) x 10(-2) for the polycrystalline I at 293 K (determined using an integrating sphere) and increases up to similar to0.8 at 77 K. The quantum yield Of O-1(2) is 0.17 +/- 0.02 in O-2-saturated dichloromethane solutions. [Au10Se4(dpppe)(4)]Br-2 {dpppe = bis(diphenylphosphanyl)pentane} (II) shows a broad near-infrared PL at 880 nm in dichloromethane [(phi(PL), = (4 1) x 10(-3)], which is shifted up to similar to1020 nm in the solid II at 77 K (psi(PL) similar to 3 x 10(-3)). Although the quantum efficiency of II as a luminophor is quite moderate, it is comparable to that of organic infrared laser dyes such as Styryl-20 and IR26. A particular configuration of the Au10Se4 core appears to be crucial for the near-infrared PL: the isomeric complexes [Au10Se4(dppm)(4)]Br-2 {dppm = bis(diphenylphosphanyl) methane} (III) and [Au10Se4(depe)(4)]Cl-2 {depe = bis(diethylphosphanyl) ethane} (IV) show no significant PL.