Synthesis, Characterization, Crystal Structure and Anticancer Study of Symmetrical Binuclear Bis- N -Heterocyclic Carbene Silver(I) Complexes

A series of asymmetric bis-benzimidazolium salts (1-6) and their respective dinuclear silver(I)
di-NHC complexes (7-12) were successfully synthesized and characterized (where NHC = Nheterocyclic carbene). Each asymmetric salt was prepared through a quaternization reaction with
the resulting NHC ligand being a bridging ligand to two adjacent metal ions. All synthesized
compounds were characterized by elemental analysis, FTIR, and 1H and 13C NMR. All salts and
dinuclear silver(I) di-NHC complexes were evaluated against the cervical adenocarcinoma
(HeLa) cancer cell line using MTT assays. Preliminary results indicated that all compounds
demonstrated dose-dependent cytotoxic activity, while compound 6 demonstrated moderate
cytotoxicity against non-cancerous Hs27 cells. The dinuclear silver(I) di-NHC complexes
showed significant IC50 values in the range of 2.91 – 5.97 µg/mL, compared to the standard drug,
etoposide (IC50 = 3.15 µg/mL).