Formation of water-soluble pincer silver(I)-carbene complexes: A novel antimicrobial agent

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.