Synthesis, characterization and antimicrobial activities of sodium salt of L-histidinatoargentate(I) derived from the pH 11 solution

As the silver(I) complex with solely coordinated by histidine (H2his) ligand, three types of complexes have been reported as different states in the solid state and in aqueous solution; water-soluble, chiral neutral complexes ∞{[Ag(L-Hhis)]2} (L-1) and ∞{[Ag(D-Hhis)]2} (D-1), water-insoluble, chiral helical polymers ∞[Ag(L-Hhis)] (L-2) and ∞[Ag(D-Hhis)] (D-2), water-insoluble, achiral polymer ∞[Ag2(D-Hhis)(L-Hhis)] (DL-3). These complexes, obtained from neutral, aqueous solutions of Ag2O and H2his, have shown effective antimicrobial activities against selected bacteria, yeasts and molds. In addition, it should be noted that these complexes are not toxic to humans. In this work, we report the preparation, characterization via elemental analysis, TG/DTA, FT-IR, ESI-MS, powder X-ray diffraction (PXD), solid state 13C NMR, solution 1H NMR, X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and antimicrobial activities of the fourth type of silver complex, i.e., sodium salt of anionic silver(I) complex with dianionic histidine, ∞{Na[Ag3(L-his)2]·nH2O} (L-4) (n = 1–5), formed in the pH 11 solution.

Graphical abstractNovel anionic silver(I) complex with solely coordinated by dianion of histidine, a sodium salt of L-histidinatoargentate(I) (L-4), was prepared by a reaction of Ag2O with L-histidine (L-H2his) in water at pH 11. ESI-MS and elemental analysis showed that the composition and formula of L-4 was ∞{Na[Ag3(L-his)2]·nH2O} (n = 1–5). Complex L-4 inhibited growth of four bacteria, two yeasts and a mold.Figure optionsDownload full-size imageDownload as PowerPoint slide