Design, synthesis, characterization, and biological activities of novel Ag(I)-NHC complexes based on 1,3-dioxane ligand

Herein, a series of new Ag(I)-NHC complexes containing 1,3-dioxane group were synthesized by the direct reaction of Ag₂O and benzimidazolium salts in light-free conditions. All Ag(I)-NHC complexes were spectrally characterized using ¹H, ¹³C NMR, FT-IR, LC-MS, and elemental analysis. Additionally, the structures of compounds 1a and 1e were elucidated by the single X-ray diffraction techniques. Further, the synthesized Ag(I)-NHC complexes were evaluated for cytotoxicity study on the L-929 cells and the anticancer activity against the HCT 116 and MCF-7 cancer cell lines. Notably, 1a showed significant anticancer activity against HCT 116 with an IC₅₀ of 6.37 ± 0.92 μg/mL compared to cisplatin (IC₅₀ = 36.75 ± 1.76 μg/mL). 1c (IC₅₀ = 3.21 ± 1.96 μg/mL) and 1e (IC₅₀ = 3.72 ± 1.12 μg/mL) exhibited significant anticancer activity against MCF-7 cells and was similar to cisplatin (IC₅₀ = 32.17 ± 2.85 μg/mL). Meanwhile, 1a and 1e displayed the highest selectivity index. Most importantly, the cell viability test showed that 1e induced neglectable cytotoxicity (IC₅₀ = 36.38 ± 2.27 μg/mL) toward L-929 and was similar to cisplatin (IC₅₀ = 36.11 ± 2.09 μg/mL). The anticancer activities of Ag(I)-NHC complexes vary depending on the substituent group of the silver complex and the cell line type. Moreover, the inhibitory mechanism of 1e was not dependent on caspase-associated apoptosis initiated by the lysosomal-mitochondrial pathway. Taken together, we conclude that this work provides a simple and rapid protocol for the synthesis of Ag(I)-NHC complexes and the featured Ag(I)-NHC complexes have an anticancer drug potential for biomedical applications.