Thione tautomer of mono-cyclohexyl-substituted bismuthiol: Synthesis and structure elucidation, characteristic vibrations, thermal behavior, and biological activity

Abstract

A new derivative of 2-cyclohexyl-substituted bismuthiol was synthesized via a sequential one-pot procedure in ethanol under reflux conditions. After many trials, the long colorless needle-like crystals could be isolated, suitable for X-ray crystallography. The chemical structure of the new bismuthiol derivative was characterized by spectroscopic techniques. The characteristic vibrations for differentiation of thiol-thione tautomers were defined regarding the comparative FTIR study of bismuthiol and two of its derivatives viz mono- and bis-cyclohexyl-substituted bismuthiol. The presence of a hyper-conjugative interaction between the S–H and π bond of C=N was indicated. In addition, the existence of C=S and C–N–H for the new product was demonstrated through single crystal XRD analysis, which supports thiol or thione tautomer determination using IR spectra. The TGA/DTA and DSC profiles of bismuthiol and mono- and bis-cyclohexyl-substituted bismuthiol were studied to determine the influence of hydrogen bonding, packing, and symmetric and unsymmetric structure on the transition phases and thermal stability. Finally, the biological activity of bismuthiol and bis- and mono-cyclohexyl-substituted bismuthiols were screened in silico by SwissADME tool and in vitro against the gram-negative (Escherichia coli ATCC 25,922) and gram-positive (Staphylococcus aureus ATCC 25,923) bacterial species.