Crystal structure, microbiological activity and theoretical studies of Ag(I) and Cu(I) coordination polymers with 1,1′-(butane-1,4-diyl)bis(3-methylimidazoline-2-thione) ligand

Reaction of 1,1′-(butane-1,4-diyl)bis(3-methylimidazoline-2-thione) (bbit) with appropriate silver(I) and copper(I) salts at room temperature leads to the formation of {[Ag(μ2-bbit)](BF4)}n (1) and {[Cu2(μ-bbit)3](PF6)2}n (2) coordination polymers. These compounds have been fully characterized by using the single crystal X-ray diffraction, XRPD, TGA, elemental analysis, infrared spectroscopy, antibacterial activity and molecular docking studies. Crystal structure of (bbit) shows that the molecule has a center of symmetry lies at the mid-point of the (CH2)4 spacer between the two imidazole-2-thione rings. In the cationic 3D structure of 1, silver atom has a distorted tetrahedral coordination geometry and each of the centrosymmetric μ2-bbit ligands with an anticonformation bridging two crystallographically related silver atoms to form a double-bridged Ag(μ2-S)2Ag core as a basic building block. Coordination mode of the bbit ligands and geometry around the metal ions in polymers 1 and 2 are different. Each of the copper atoms in 2 has a trigonal planar CuS3 environment and μ-bbit act as a bridging bidentate ligand, so that two of the CuS3 motifs are interconnected by a pair of μ-bbit ligands through the thione sulfur atoms to generate a 22-membered [Cu2(μ-bbit)2]2+ ring. The adjacent [Cu2(μ-bbit)2]2+ cores are linked by a single μ-bbit ligand to form a 1D chain structure. Additionally, the adjacent 1D chains are extended into a non-covalent 3D network structure by the intermolecular P F…H hydrogen bonds. The in vitro antibacterial studies of bbit, polymers 1 and 2 showed that, polymer 1 was able to inhibit growth of the tested bacteria, whereas the bbit ligand has a weak and polymer 2 showed no antibacterial activity against these bacteria.