Rational synthesis, structural characterization, theoretical studies, antibacterial activity and selective dye absorption of new silver coordination polymers generated from a flexible bis (imidazole-2-thione) ligand

Abstract

Herein, a competition between the different anions with different size, shape and coordination ability was used for the synthesis of three silver(I)-coordination polymers (Ag-CPs) was investigated. In this study, three 3D-supra-molecular coordination compounds namely, [Ag2L(NO3)2]n (1), {[Ag2L][PF6]2}n (2) and [AgLBr]n (3) (L = 1,1′-(1,5-pentadienyl)bis-(1,3-dihydro-3-methyl-1H-imidazole-2-thione)) have been synthesized and fully characterized via a single crystal X-ray diffraction, powder X-ray diffraction (PXRD), elemental analysis (CHN), FT-IR spectra and thermo gravimetric analysis (TGA). Structural analysis revealed that the counter ions have a notable impact in directing the conformation and coordination mode of ligand, but they have no effect on the structural dimension of the polymers. Furthermore, by increasing the coordination ability of the anions, the coordination geometry of the AgI centers change, from a distorted linear (for 2) to a distorted square pyramidal coordination geometry (for 1). The chains are further stabilized by the intermolecular CH⋯O and CH⋯N for 1, P–F…HC for 2, CH⋯Br and CH⋯N interactions for 3 to form a 3D non-covalent lattice network structure. In contrast to the 1 and 3, polymer 2 exhibits a large capacity and selectivity to adsorb dye from aqueous solutions. Sorption kinetic was investigated by three kinetic models. The electronic band structure and the projection densities of states (PDOS) of compounds 1 and 3 were investigated by means of DFT-D3. The results demonstrated that both compounds are non-magnetic and show a semiconducting character with a direct band gap of ~3 eV. All of the synthesized compounds, possess antibacterial activity against the selected strain of Gram- negative (Escherichiacoli, Pseudomonas aeruginosa) and Gram- positive (Staphylococcus aureus, Bacillus subtilis) bacteria.