Synthesis, crystal structure, and anticancer activity of four metallo‐supramolecular assemblies from dinuclear silver(I)‐N‐heterocyclic carbene

Abstract

Four Ag(I)-N-heterocyclic carbene (Ag-NHC) supramolecular assemblies, viz. Ag2(L1)2(PF6)2 (L1 = 2, 5-bis[1-benzenyl-2-ylidene-imidazolium-3-yl)]-pyridine) (5), Ag2(L2)2(PF6)2 (L2 = 1, 3-bis[1-benzenyl-2-ylidene-benzimidazolium-3-yl)]-benzene) (6), Ag2(L3)2(PF6)2 (L3 = 1, 4-bis[1-(quinolin-8-yl)-2-ylidene-imidazolium-3-yl)]-benzene) (9), and [Ag(L4)PF6]n (L4 = 1, 4-bis[1-benzenyl-1, 2, 4-triazolium-4-yl-5-ylidene)]-benzene) (12), were synthesized from silver oxide and the corresponding NHC ligand precursors (3, 4, 8, and 11). They were characterized by 1H NMR, 13C NMR, ESI–MS, and single-crystal X-ray diffraction (XRD) analysis. X-ray crystallography revealed that the Ag-NHC supramolecular assemblies 5, 6, and 9 are a box or square dinuclear Ag-NHC [2+2] metallo-macrocyclic supramolecular assemblies, whereas 12 functioned as a one-dimensional (1D) linear Ag-NHC polymer with the link of carbene CNHC–Ag–CNHC bonds. The structural assignments for 5 were further supported by density functional theory (DFT) calculations. The emission band of 12 has a slight blue shift as compared to the precursors NHC compound 11, owing to the metal–ligand charge transition in 1D linear Ag-NHC polymer. The in vitro cytotoxic activity observed in 5, 6, 9, and 12 against breast cancer MCF-7 cells indicates that the Ag-NHC supramolecular assembly 9 displayed the best anticancer activity in MCF-7 cells at a concentration of 5 × 10−6 mol/L. All four Ag-NHC supramolecular assemblies had significant inhibitory effects on breast cancer cell growth at a concentration of 5 × 10−5 mol/L.