A series of bidendate 5,6-dimethyl benzimidazolium-based N-heterocyclic carbene (NHC) proligands and their silver complexes were synthesized. The synthetic approaches to the proligands were constrained by the methyl substituents, which impose a significant impact on the reactivity according to their sigma electron-donating abilities. The corresponding silver(I) complexes were obtained by in situ deprotonation of the NHCs and characterized by physicochemical and spectroscopic methods. In addition, a single-crystal X-ray diffraction study of complex C5 revealed its dinuclear structure. Irreversibility of redox events was observed in electrochemical studies of these complexes. In vitro anticancer studies of the azolium salts and their silver(I) complexes against human breast cancer (MDA-MB-231), colon cancer (HCT-116) and normal endothelial (EA.hy926) cells revealed that all the compounds are more cytotoxic to cancer cells than to normal cells and the complexes are more potent than their corresponding NHC proligands. Increased chain length, the presence of methyl substituents on the benzimidazole ring and aryl linker and two silver centres all enhance the biopotency of these complexes.Graphical abstractSubstituted benzimidazolium-based N-heterocyclic carbene (NHC) proligands and silver complexes are advantageous anticancer tools for medicinal chemistry.

中文翻译：

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环取代对苯并咪唑盐及其银（I）配合物合成的影响：表征、电化学研究和抗癌潜力评估

合成了一系列基于双联 5,6-二甲基苯并咪唑鎓的 N-杂环卡宾 (NHC) 前配体及其银配合物。前配体的合成方法受到甲基取代基的限制，根据它们的 sigma 给电子能力对反应性产生显着影响。通过NHCs的原位去质子化获得相应的银（I）配合物，并通过物理化学和光谱方法进行表征。此外，复合物 C5 的单晶 X 射线衍射研究揭示了其双核结构。在这些配合物的电化学研究中观察到氧化还原事件的不可逆性。唑盐及其银 (I) 络合物对人乳腺癌 (MDA-MB-231)、结肠癌 (HCT-116) 和正常内皮 (EA. hy926) 细胞显示所有化合物对癌细胞的细胞毒性比对正常细胞更强，并且复合物比其相应的 NHC 前配体更有效。增加的链长、苯并咪唑环和芳基接头上甲基取代基的存在以及两个银中心都增强了这些配合物的生物效力。图文摘要取代的苯并咪唑基 N-杂环卡宾 (NHC) 前配体和银配合物是药用的有利抗癌工具化学。