Silver(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(l) 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 (H-1, C-13 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 mu M, while imidazolium salts, 1-3, showed least (>200 mu M) to moderate (20.3 +/- 0.2 and 95.0 +/- 2 mu M) 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 mu M, respectively. (C) 2014 Elsevier B.V. All rights reserved.