Syntheses, structures, and optical limiting capability of tetranuclear cubane, hexanuclear prism-cage, and octanuclear double-cubane argento-selenotungstates

Treatment of [Et4N]2[WSe4] with AgX (X = Br, I) in a 1:3 ratio in DMF or DMF/CH3CN afforded tetranuclear cubane-like heteroselenometallic clusters [Et4N]3[(μ3-X)(μ3-WQSe3)(AgX)3] (X = Br, Q = Se 1; X = Br, Q = O 2; X = I, Q = Se 3). While the reaction of [Et4N]2[WSe4] with two equivalents of AgBr in DMF gave a hexanuclear cage heteroselenometallic cluster [Et4N]4[(μ3-WO0.83Se3.17)2(AgBr)4] (4). Treatment of [Et4N]2[WSe4] with three equivalents of AgCl in DMF in the presence of the bidentate phosphine ligand bis-(diphenylphosphino)-ethane (dppe) or bis-(diphenylphosphino)-propane (dppp) resulted in the isolation of octanuclear heteroselenometallic clusters [Et4N]4[{(μ3-Cl)(μ3-WSe4)Ag3Cl2}2(μ-dppe)] (5) and [Et4N]2[{(μ3-WSe4)Ag3Cl2}2(μ-dppp)2] (6) with double-cubane. All clusters are anionic and air-stable in the solid-state, and were characterized by electronic, infrared, mass and NMR spectroscopies, and their molecular structures have been also established by X-ray crystallography. The nonlinear optical properties of clusters 1–6 were examined by z-scan techniques with 7 ns pulses at 532 nm, and the optical limiting effects of clusters 1–6 were also determined for the comparison with the related argentoselenometallic clusters in this paper.

Graphical abstractA series of tetra-, hexa- and octa-nuclear anionic argento-selenotungstates have been synthesized and characterized by spectroscopy and X-ray crystallography. The nonlinear optical properties and optical limiting effects of these silver-containing heteroselenometallic clusters were also determined for the investigation of the structure–property relationship.Figure optionsDownload full-size imageDownload as PowerPoint slide