Discrete Supertetrahedral T3 InQ Clusters (Q = S, S/Se, Se, Se/Te): Ionothermal Syntheses and Tunable Optical and Photodegradation Properties

Presented are the ionothermal syntheses, characterizations, and photodegradation properties of four isostructural chalcogenidometalate compounds, namely, [Bmmim]₅[In₁₀Q₁₆Cl₃(Bim)] (Q = S (IL-InS-1), S_7.12Se_8.88 (IL-InSSe-2), Se (IL-InSe-3), Se_13.80Te_2.20 (IL-InSeTe-4); Bmmim = 1-butyl-2,3-dimethylimidazolium, Bim = 1-butyl-2-methylimidazole). According to the single-crystal X-ray diffraction analysis, the title compounds belong to the C2/c space group and feature isolated supertetrahedral T3 anionic units of [In₁₀Q₁₆Cl₃(Bim)]^5- stabilized by [Bmmim]⁺ cations. The ionic liquid not only provided the [Bmmim]⁺ as the counterions but also acted as the reactive solvent releasing [Bim] ligands that are covalently bonded to In atoms. Unlike the widely reported extended frameworks that contain T3 InS/Se as building units, IL-InSe-3 represents the first example of discrete T3 InSe clusters, and the InTe-based discrete T3 cluster (IL-InSeTe-4) was characterized for the first time. The optical absorption edges of the title compounds showed gradual red shifts along with the change of chalcogens from S, S/Se, Se, to Se/Te. As a result, their photocatalytic activities were tunable with the optical response moving from the ultraviolet (UV) to visible light region.