Synthesis, crystal structure and third-order nonlinear optical (NLO) properties of a novel tetranuclear organometallic cluster [(η5–C5Me5)WS3Au]2

Abstract

Reactions of [PPh₄][(η⁵–C₅Me₅)WS₃] with equimolar AuI in MeCN gave rise to the title compound [(η⁵–C₅Me₅)WS₃Au]₂ (1) in high yield. Compound 1 crystallizes in the monoclinic space group P2₁/a with cell dimensions: a = 17.123(4), b = 9.373(3), c = 18.019(4) Å, β = 107.43(2)°, V = 2759.2(13) ų and Z = 4. The molecular structure of 1 contains a W₂Au₂ core in which two Au atoms are linked by two (η⁵–C₅Me₅)WS₃ moieties. The nonlinear optical (NLO) properties of 1 were studied by 35 ps and 12 ns laser pulses. The third-order nonlinear susceptibility χ^(3),, the nonlinear absorption, and optical limiting response are measured by degenerate four-wave mixing (DFWM), the Z-scan technique, and the transmission technique, respectively. The experimental data are theoretically fitted, and the mechanism for the third-order optical nonlinearities and the optical limiting properties are discussed, and the absorption cross sections of the ground state and the excited states are evaluated by a rate equation model.