Synthesis and crystal structure and nonlinear optical properties of polymeric W (Mo)-Cu-S cluster

The polymeric chalcogenide [W2O2S6Cu4(NCMe)4]n (compound 1) was synthesized by the self-assembly reaction of (NH4)2(WOS3) with CuBr in MeCN in the presence of tricyclohexylphosphane (PCy3) under a purified nitrogen atmosphere using standard Schlenk techniques. It gives rise to a novel 1D polymeric compound 1 with solvent MeCN coordinated to the copper atom. This situation is unprecedented in the W(Mo)/Cu/S system. The crystals were characterized by elemental analysis, IR and single-crystal X-ray crystallography. The configuration of the polymeric compound can be viewed as a helical chain which is propagated along the crystallographic c axis. The excited state absorption and refraction of compound 1 in CH3CN solution were studied by using the Z-scan technique with laser pulses of 40 ps pulse-width at a wavelength of 532 nm. The polymeric compound possesses an optical self-focusing performance. The positive nonlinear refraction is attributed to population transitions between singlet states. Compound 1 displays a strong excited-state absorption.