Large third-order optical nonlinearity of two cubane-like clusters containing oxotrithiometalate anions and silver: Synthesis, characterization, reactivity, and NLO properties-structure correlation

Using low heating temperature solid-state reactions and self-assembly reactions, two new candidates [Et₄N]₃[MOS₃(μ₃-I)(AgI)₃ ] (M = Mo, 1; W, 2) for nonlinear optical (NLO) materials have been synthesized and characterized crystallographically as tetranuclear cubane-like heterothiometallic clusters. Their optical nonlinearities were measured by the Z-scan technique with an 8 ns pulsed laser at 532 nm. These two isomorphous clusters both exhibit strong NLO absorptive abilities [α₂ = 1.0 × 10^-9 m W^-1 (1), 1.2 × 10^-9 m W^-1 (2)] and effective self-focusing performance [n₂ = 8.8 × 10^-17 m² W^-1 (1), 4.5 × 10^-17 m² W^-1 (2)]. The optical limiting (OL) investigation demonstrates that these two clusters show large OL effects. The NLO properties of tetranuclear Ag-containing cubane-like clusters with oxotrithiometalate anions are reported here for the first time and the third-order NLO properties and OL effects suggest that clusters 1 and 2 are promising candidates for NLO applications. A comparison of the NLO effect among clusters with the same C_3v symmetry has been made in order to further understand and explore the function-structure relationships of these heterothiometallic clusters.