Novel Photophysical Properties of Gold Selenide Complexes:  Photogeneration of Singlet Oxygen by [Au₁₈Se₈(dppe)₆]Br₂and 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. [Au 18 Se 8 (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, 1 O 2, in solution, and high photostability. The quantum yield of PL, φ PL, is (7.5 ± 0.5) × 10 -2 for the polycrystalline I at 293 K (determined using an integrating sphere) and increases up to ∼0.8 at 77 K. The quantum yield of 1 O 2 is 0.17 ± 0.02 in O 2 -saturated dichloromethane solutions. [Au 10 Se 4 (dpppe) 4 ]Br 2 {dpppe = bis(diphenylphosphanyl)pentane} ( II ) shows a broad near-infrared PL at 880 nm in dichloromethane [φ PL = (4 ± 1) × 10 -3 ], which is shifted up to ∼1020 nm in the solid II at 77 K (φ PL ∼ 3 × 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 Au 10 Se 4 core appears to be crucial for the near-infrared PL: the “isomeric” complexes [Au 10 Se 4 (dppm) 4 ]Br 2 {dppm = bis(diphenylphosphanyl) methane} ( III ) and [Au 10 Se 4 (depe) 4 ]Cl 2 {depe = bis(diethylphosphanyl) ethane} ( IV ) show no significant PL.