NHC–Silver(I) Complexes as Chemical Nucleases; Synthesis,Crystal Structures,and Antibacterial Studies

A series of N‐heterocyclic carbene (NHC) precursors, 1‐methoxylethyl‐3‐allylimidazolium hexafluorophosphate ( 1 ), 1‐ethyl‐3‐allylimidazolium hexafluorophosphate ( 2 ), and 1‐pentyl‐3‐allylimidazolium hexafluorophosphate ( 3 ) were synthesized. These salts were treated with Ag₂O to afford their corresponding mononuclear Ag(I)‐NHC complexes, namely 1‐methoxylethyl‐3‐allylimidazolium silver(I) hexafluorophosphate ( 4 ), 1‐ethyl‐3‐allylimidazolium silver(I) hexafluorophosphate ( 5 ), and 1‐pentyl‐3‐allylimidazolium silver(I) hexafluorophosphate ( 6 ), respectively. These compounds were characterized by physicochemical and spectroscopy techniques. Compounds 4 and 5 were structurally characterized by single crystal X‐ray diffraction, and their stability in solution was investigated and found to be acceptable for the antibacterial studies. These new NHC precursors and their respective Ag–NHC complexes were screened for their antibacterial activities against Staphylococcus aureus (ATCC 12600) and Escherichia coli (ATCC 25922). Compounds 1–3 showed no inhibition, whereas 4–6 inhibited the growth of these bacteria. The nuclease activities of the reported compounds against plasmid DNA and RNA were assessed by gel electrophoresis, and the results indicate that complexes 5 and 6 can degrade both DNA and RNA in the absence of an oxidant.     

Benzimidazole‐based silver(I)–N‐heterocyclic carbene complexes as anti‐bacterials: synthesis,crystal structures and nucleic acids interaction studies

A series of new benzimidazolium salts as N‐heterocyclic carbene (NHC) precursors has been synthesized. Reactions of these salts with Ag₂O with varying metal‐to‐salt ratio facilitate the formation of a series of new binuclear and mononuclear Ag(I)–NHC complexes. All compounds were characterized using physicochemical and spectroscopic techniques. Single‐crystal X‐ray diffraction study reveals a binuclear structure for one of the complexes and a mononuclear one for two others. These complexes exist as cationic Ag(I)–NHC complexes with the chelation of carbene carbons to the silver centre in an almost linear manner. The compounds were screened for their anti‐bacterial activities against Staphylococcus aureus (ATCC 12600) as a Gram‐positive bacterium and Escherichia coli (ATCC 25922) as a Gram‐negative bacterium. The results show that both bacteria appear markedly inhibited. Furthermore, the results suggest the possibility of steric variation as a modulation of the anti‐bacterial activities. The nuclease activities of the compounds were assessed using gel electrophoresis and the results indicate that these complexes can cleave or degrade DNA and RNA via a non‐oxidative mechanism. Copyright © 2014 John Wiley & Sons, Ltd.     

Dinuclear silver(I)-N-heterocyclic carbene complexes of N-allyl substituted (benz)imidazol-2-ylidenes with pyridine spacers: synthesis,crystal structures,nuclease and antibacterial studies

Transition Metal Chemistry - The synthesis, structures and antibacterial studies of silver complexes of N-heterocyclic carbene (NHC) ligands are reported. The NHC precursors,...