Formation of Water-Soluble Pincer Silver(I)−Carbene Complexes:  A Novel Antimicrobial Agent

Abstract

Silver(I)-2,6-bis(ethanolimidazolemethyl)pyridine hydroxide (4a) and silver(I)-2,6-bis(propanolimidazolemethyl)pyridine hydroxide (4b) are water-soluble silver(I)-carbene complexes that were synthesized in high yield by reacting silver(I) oxide with N-substituted pincer ligands 3 (a = 2,6-bis(ethanolimidazoliummethyl)pyridine diiodide, b = 2,6-bis(propanolimidazoliummethylpyridine)pyridine dibromide). The X-ray crystal structure of 4a is a one-dimensional linear polymer, whereas the mass spectroscopy confirms a monomer in the gas phase. A change in the anion of 4a from a hydroxide to a hexafluorophosphate formed a silver(I)-carbene complex 4c that is dimeric in structure and insoluble in water. The bactericidal activities of the water-soluble silver(I)-carbene complexes were found to be improved over that of silver nitrate.

Beyond catalysis: N-heterocyclic carbene complexes as components for medicinal, luminescent, and functional materials applications

“…Further improvement of the bacteriostatic and antifungal activity has been achieved by encapsulating silver NHC complexes into polymers by electrospinning. 5 The modified polymer mats show bactericidal activities that are higher than the currently commercialized 1% silver sulfadiazine ointment…”

“…2). 5 Additionally, the 55 complex solutions with lower minimum inhibitory concentration (MIC) values inhibit the growth of microorganisms for a longer period than AgNO 3 . The higher activity may be rationalized by the partially covalent character of the Ag-C NHC bond, which provides enhanced stability and 60 decelerates silver dissociation.…”

Stable heteroaromatic carbenes of the benzimidazole and 1,2,4-triazole series

“…Caballero et al 17 reported a silver complex of bisimidazol-2-ylidene with a pyridine bridge; however, this complex is not polymeric. While the silver complexes described by Chen et al 44 and Melaiye et al 45 are oligomeric clusters, these complexes do not involve conjugation. Accordingly, the synthesis of stable metal complexes of polycarbenes remains a synthetic challenge.…”

BIAN N-Heterocyclic Gold Carbene Complexes induced cytotoxicity in human cancer cells via upregulating oxidative stress

“…In order to overcome these limitations, a variety of different metal containing complexes are currently being studied as potential anticancer agents. Among such compounds, the metal N-heterocyclic carbene (NHC) complexes are beginning to attract significant attention on account of their efficient drug design (Liu and Gust, 2013a) Of the various metal NHC complexes that have been prepared thus far, the silver and gold NHC complexes show considerable promise as anti-microbial and anticancer agents (Melaiye et al, 2004;Hickey et al, 2008b;Ozdemir et al, 2010;Elzatahry et al, 2012).…”