Coordination Assemblies of Acetylenic Dithioether Ligands on Silver(I) Salts: Crystal Structure, Antibacterial and Cytotoxicity Activities

Coordination polymers (CPs) and metal-organic frameworks (MOFs) constitute a new class of antibacterial materials. Interest in them stems from their wide range of topology, dimensionality, and secondary building units that can be tuned by an appropriate choice of metal ions and ligands. In particular, silver-based species feature good antibacterial properties. In this study, we explored the coordination of three acetylenic dithioether RSCH₂C≡CCH₂SR [R = phenyl (L_Ph), cyclohexyl (L_Cy), or <i>tert</i>-butyl (L_<i>t</i>Bu)] ligands on several silver salts (silver tosylate, silver triflate, and silver trifluoroacetate). The crystallographic characterization evidenced the formation of a molecular macrocycle and six CPs with different dimensionalities, ranging from one to two dimensions. In most cases, they are composed of four-coordinated silver atoms in a tetrahedral environment. Their antibacterial activity was investigated against Gram-positive (<i>Staphylococcus aureus</i>) and Gram-negative (<i>Escherichia coli</i>) bacteria. All CPs present good antibacterial properties against the tested bacteria with minimal inhibitory concentrations ranging from 5 to 40 μg of Ag/mL. Interestingly, we found that these values could not be correlated to their architecture or morphology or to the amount of silver released. The cytotoxicity of these compounds was also evaluated on normal human dermal fibroblasts, and three of these CPs were found to be biocompatible.