Synthesis, crystal structure and third-order nonlinear optical properties of a hexanuclear cluster [WOS3Cu2(4-tBuPy)2]2 (4-tBuPy = 4-tert-butylpyridine)

Reaction of (NH4)2[WOS3] with 2 equiv. of CuI in 4-tert-butylpyridine (4-tBuPy) and methanol afforded a hexanuclear neutral cluster [WOS3Cu2(4-tBuPy)2]2. This compound was characterized by elementary analysis, IR, UV–vis, 1H NMR, thermogravimetric analysis, and its crystal structure was determined by X-ray single crystal diffraction. The compound contains a hexagonal prismatic cage structure in which two butterfly-shaped [WOS3Cu2(4-tBuPy)2] cluster fragments are interlinked through four CuS bonds. The nonlinear optical properties were studied with a 30 ps pulsed laser at 532 nm. The compound exhibited strong nonlinear absorption effect with α2 = 2.5 × 10−10 mW−1, χ(3) = 8.5 × 10−14 esu, and γ = 4.8 × 10−30 esu.