Structural Insights into AgBi(SC₁₂H₂₅)₄ Mixed-Metal n-Alkanethiolate: Heterometallic Thiolate Bridging and...

Long-chain metal n-alkanethiolates (MTs) are inorganic-organic hybrid materials, characterized by a metal-sulfur inorganic central plane sandwiched between hydrocarbon bilayers. Though MTs are known for over a century now, their crystal structures are conclusively established only recently. Mixed-metal thiolates (MMTs) are structurally similar to MTs and contain heterometals in the inorganic plane. With a very limited number of MMTs explored to date, their structures remain completely unknown. Here we report the synthesis and structural elucidation of a mixed-metal thiolate, AgBi(SC₁₂H₂₅)₄, providing direct insight into heterometal arrangement by combining X-ray absorption fine structure spectroscopy and density functional theory calculations. The results establish that the AgBi MMT contains discrete molecular units like [RS-Ag-SR-Bi(SR)₂] containing both Ag and Bi metals with an intramolecular heterometallic μ₂-thiolate bridging. The units further share strong intermolecular Ag···Bi metallophilic interactions at a very short distance of 2.72 Å, playing a crucial role in the self-assembly. Intermolecular metal-to-metal charge transfer occurring both directly and via the thiolate bridge gives rise to the absorption maxima observed in the UV-Vis spectrum. The intermolecular interactions predominantly arise from the thiolate group (RS^-) of one unit interacting with the Ag⁺ and Bi³⁺ centers of the adjacent units, in addition to the Ag···Bi metallophilic interaction.