Structural Insights into AgBi(SC ₁₂ H ₂₅ ) ₄ Mixed-Metal n -Alkanethiolate: Heterometallic Thiolate Bridging and Metallophilic Interaction-Directed Self-Assembly

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(SC 12 H 25 ) 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 μ 2 –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 Bi 3+ centers of the adjacent units, in addition to the Ag···Bi metallophilic interaction.