Crystal structures and nonlinear optical properties of new clusters [MOS3Cu3(PPh3)3{S2P(OCH2Ph)2}] (M=Mo, W)

Two new isostructural O,O′-dialkyl dithiophosphate-containing sulfido clusters, MOS3Cu3(PPh3)3{S2P(OCH2Ph)2}] (M=Mo (1); M=W (2)), were synthesized through reaction of [NH4[MOS3] with [CuS2P(OCH2Ph)2]. They possess an incomplete cubane-like structure, in which the dithiophosphate ligand adopts a triply bridging role, employing one sulfur atom to bind to one Cu atom and the other to two Cu atoms. High third-order nonlinear optical properties of the two clusters were observed, and Z-scan data measured with 532 nm nanosecond laser pulses showed effective third-order optical nonlinearities α2=0.78×10−10 and 1.16×10−10 m W−1, and n2=−7.8×10−18 and 4.0×10−18 m2 W−1, respectively, for DMF solution of compound 1 and DMF solution of 2. These two clusters exhibit large optical limiting performance with limiting threshold values of 220 mJ cm−2 for 1 and 600 mJ cm−2 for 2.