Synthesis, crystal structure and third-order optical nonlinearity of a 'flywheel'-shaped cluster, [MoS4Cu3(dppm)(3)][BF4]center dot 2H(2)O

The title compound [MoS4Cu3(dppm)(3)][BF4]]. 2H(2)O (dppm = Ph2PCH2PPh2) wa s synthesized for nonlinear optical studies by the reaction of (Et4N)(2)MoS 4 and [Cu-2(dppm)(2)(MeCN)(4)][BF4](2) in CH3CN solution. Single-crystal X- ray analysis revealed that three copper atoms and the MoS42- form a distort ed 'flywheel' array with W-Cu separations of 2.7754(14), 2.792(2) and 2.820 (2) Angstrom. The third-order nonlinear optical properties were investigat ed by a Z-scan technique with 7 ns laser pulses at 532 nm. It was observed that the nonlinear absorption is very small, but it has considerable third- order large nonlinear refractive index. (C) 2000 Elsevier Science Ltd. All rights reserved.