Skeleton atomic effect on nonlinear optical properties of linear trinuclear heteroselenometallic compounds with univalent coinage metals

Treatment of [NEt4](2)[WSe4] with 2 equiv. of [M(PPh3)(2)(NO3)] (M = Cu or Ag) in CH2Cl2 gave the trinuclear cupro- or argento-selenotungstate compoun ds [(WSe4)(MPPh3){M(PPh3)(2)}] (M = Cu 1, Ag 2). In compounds 1 and 2, the [WSe4](2-) anion is bonded to [M(PPh3)](+) and [M(PPh3)(2)](+) fragments, r esulting in trigonal and tetrahedral coordination geometries around M. Trea tment of [NEt4](2)[WSe4] with [Au(PPh3)Cl] in a 1 : 2 molar ratio afforded the trinuclear auroselenotungstate compound [WSe4(AuPPh3)(2)] 3. For compou nd 3, the two equivalent [Au(PPh3)](+) fragments bind to the [WSe4](2-) sym metrically, and the geometry around the two Au atoms is distorted trigonal planar. Compounds 1-3 are air and optically stable. Their nonlinear optical absorption and refraction along with the optical limiting effects were det ermined under the same conditions. By comparison of nonlinear optical prope rties of the three compounds, a skeleton atomic effect on the nonlinear opt ical properties for heteroselenometallic cluster compounds was outlined. Co mpound 3 exhibits both large nonlinear optical absorption and refraction (s elf-focusing). The Ag-containing heteroselenometallic compound 2 may be con sidered as a good candidate for an optical limiting material.