Preparation, Characterization, DFT Calculations, biological evaluations and Molecular docking studies of benzimidazolium-based N-heterocyclic carbenes and selenium-adducts

This study involves designing through DFT, synthesis, and characterization of three benzimidazolium salts (AL1-AL3) and their corresponding selenium adducts (AC1-AC3). The compounds were characterized theoretically as well as experimentally through FT-IR and ¹H & ¹³C NMR. Theoretical calculations were performed using the B3LYP/6–31 G (d, p) levels of theory to determine various optical and chemical properties of the designed molecules. The HOMO/LUMO energies and their energy gaps were also calculated to assess the structure–activity relationships. In vitro testing against the Human breast Adenocarcinoma cell line (MCF-7) was conducted using the MTT assay and 5-Fluorouracil (standard) was used for the comparison of results. The ligand AL3 showed maximum inhibitory potential (66.51 ± 0.82) even approaching the standard 5FU while the complex AC3 showed maximum viability with the least inhibition value as (21.7 ± 0.73) against MCF7 cell line. The antioxidant potential for scavenging DPPH radicals was also assessed, revealing that AL1 has the greatest potential, with a value of 62.01 ± 0.9. The interactions of the complexes with various proteins were also assessed via molecular docking studies, revealing strong binding energies and ligand affinities towards angiogenic factors such as VEGF-A, EGF, HIF, and COX-1. This suggests that the anticancer activities of the complexes AC1-AC3 may be attributed to their potent anti-angiogenic effects. Moreover, selenium-NHC adducts exhibited more significant anticancer potential as compared to their ligands. Furthermore, the antibacterial and antifungal potential of compounds AC1-AC3 was assessed. Notably, the ligand AL2 exhibited significant antibacterial activity against E. coli, as evidenced by a zone of inhibition (ZI) value of 17.5 ± 0.29 mm, whereas AL3 demonstrated the highest activity against P. multocida showing the ZOI value of 18.5 ± 0.38. Among all the synthesized compounds, AL1 displayed the most significant antifungal activity against F. avenaceum (27 ± 0.51 mm), surpassing even the standard drug gentamycin (13 ± 0.23 mm), which was tested under the same conditions. However, its corresponding Se-NHC, AC1, adduct was found to be inactive. Overall, AL3 and its corresponding Se-NHC adduct (AC3), demonstrated superior biological potential against the majority of the tested strains.