Design, Synthesis, and Antibacterial Assessment of Silver(I)-Based Coordination Polymers with Variable Counterions and Unprecedented Structures by the Tuning Spacer Length and Binding Mode of Flexible Bis(imidazole-2-thiones) Ligands

An investigation of the impact of alkyl spacerlength of theflexible ligands and influence of shape andcoordination ability of the counterions has been done on aseries offive silver(I)-bis(imidazole-2-thione) coordinationpolymers. Thefive compounds, namely, [Ag2L4(NO3)2]n,{[AgL4]2[CF3SO3]2}n,[Ag2L6(CF3SO3)2]n,[Ag2L6(NO3)-(ClO4)]n, and [Ag2L6Br2]n(L4= 1,1′-(butane-1,4-diyl)bis(3-methylimidazoline-2-thione) andL6= 1,1′-(hexane-1,4-diyl)-bis(3-methylimidazoline-2-thione) have been characterized byelemental analysis, IR spectra, thermogravimetric analysis(TGA), powder X-ray diffraction, and single crystal X-raydiffraction. In the title polymers, theL4andL6ligands exhibitunprecedented coordination modes, and the Ag(I) centersadopt a range of coordination geometries. The single crystal structural analysis of the title compounds shows that polymers basedon theL4ligand predominately adopt AgS4core structure which does not appear in the polymers containingL6ligand. The TGAexperimental data reveal that these compounds start to decompose in the temperature range of 240−341°C. All of thesynthesized compounds, in particular, polymer2, possess antibacterial activity against the selected strain of Gram-negative(Escherichia coli,Pseudomonas aeruginosa) and Gram-positive (Staphylococcus aureus,Bacillus subtilis) bacteria.