Selenium-<i>N</i>-heterocyclic carbene (Se-NHC) complexes with higher aromaticity inhibit microbes: synthesis, structure, and biological potential

Abstract

The synthesis of five selenium complexes bearing imidazole-based N-heterocyclic carbene ligands (Se-NHC) are reported. The adducts were characterized by elemental and spectroscopic analysis (FTIR, 1H and 13C NMR). Single-crystal XRD confirmed the structures of two Se-NHC adducts, VIII and XI. Zone of inhibition (ZOI) values of Se-NHC complexes were evaluated towards two bacterial (Bacillus thuringiensis and Escherichia coli) and one fungal strain (Candida albicans). The most active tested compound was XI with inhibition value of 24.1 ± 0.1 mm against E. coli, and it showed higher activity than Tetracycline (reference drug). Similarly, XI exhibited good inhibition potential against C. albicans (26.5 ± 0.2 mm). The hemolytic assay demonstrated that the tested compounds (VIII-XII) are non-toxic to healthy human blood; however, thrombolysis indicated that VIII-XII could be used as potential thrombolytic agents. It is concluded that Se-NHC carbene adducts having more aromatic rings at terminal nitrogens of imidazole are more effective than other tested compounds. Se-NHC compounds have more efficacy against bacterial strains than fungal strain.