ilver(I)-N-heterocyclic carbene complexes of nitrile-functionalized imidazol-2-ylidene ligands as anticancer agents

Reactions of symmetrically and non-symmetrically substituted nitrile-functionalized imidazolium salts (1–3) with silver(I) oxide in methanol at room temperature afforded complexes (4–6) of the type [NHC-Ag-NHC]PF6, (NHC: imidazol-2-ylidene). All reported compounds have been characterized by spectral (1H, 13C NMR and FTIR) and elemental analysis. The structure of bis-imidazolium salt 3 and silver complex 4 was unambiguously elucidated by the single-crystal X-ray diffraction method. The effect of substitutions on the anticancer activity of compounds 1–6 has been investigated by in vitro cytotoxicity studies against human colorectal (HCT 116) cancer cell line, using the MTT assay method. All three silver complexes (4–6) displayed promising anticancer activity with IC50 values of 6.0 ± 0.2, 14.0 ± 0.6 and 4.0 ± 0.2 μM, while imidazolium salts, 1–3, showed least (> 200 μM) to moderate (20.3 ± 0.2 and 95.0 ± 2 μM) anticancer potential, respectively. Bis-imidazolium salt 3 and binuclear complex 6 displayed good activity against human breast (MCF-7) cancer line with IC50 values of 82.4 ± 2.5 and 0.9 ± 0.4 μM, respectively.