A novel antibacterial benzimidazolium hexachlorotellurate hybrid compound: Experimental-theoretical characterization

Abstract

Inspired by the antibacterial properties of recent hybrid materials containing hexahalogenotellurate anions, a novel hybrid compound, formulated as (C7H7N2)2TeCl6.(H2O)2 (T3), was synthesized by slow evaporation from a mixture of tellurium dioxide and HCl added to a benzimidazole solution at room temperature. T3 was fully characterized using various methods such as X-ray diffraction (SC-XRD & XRPD), Fourier-transform infrared spectroscopy (FT-IR), ultraviolet–visible spectroscopy (UV–Vis), Mass spectroscopy (MS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The single crystal X-ray analysis showed that T3 crystallizes in the monoclinicP21/m space group with good reliability factor and that its crystal structure is organized by an alternation of hexachlorotellurate octahedral polyhedra {TeCl6} and benzimidazolium planes {C7H7N2} joined together through hydrogen bonds that ensure the cohesion and the overall stability. Exhaustive vibrational and optical studies of T3 were performed through infrared absorption at room temperature and UV–vis spectroscopies, respectively. In the ultraviolet area T3 has three absorption signals corresponding to charge transfers in the organic part, between the organic and inorganic moieties, and in the inorganic complex, as computationally confirmed. Theoretical calculations also reveal a HOMO-LUMO gap of 3.95 eV, large enough as to indicate stability against intramolecular electron excitation. Thermogravimetric data of the thermal decomposition of T3 were also analysed revealing that the weight loss occurs in three stages. An isoconversional method was used for computing the activation energy and its variation along the thermal decomposition. Finally, and as a main feature of T3, antibacterial activity against Escherichia coli and Staphylococcus aureus stains has been tested and confirmed after incubation for 24 h at 37 °C of T3 diluted at different concentrations (0.5–2 mg/ml) in ethanol or dimethyl sulfoxide (DMSO).