title: Synthesis, characterization, and structure-activity relationship of the antimicrobial activities of dinuclear N-heterocyclic carbene (NHC)-silver(I) complexes.
abstract: The three dinuclear silver(I) complexes of N-heterocyclic carbene (NHC) ligands, [Ag2(L-1a)](PF6)2·2CH3CN (Ag-1a), [Ag2(L-2)2](PF6)2·H2O (Ag-2), and [Ag2(L-4)2](PF6)2·2CH3CN (Ag-4), were synthesized by reactions of Ag2O with the corresponding PF6-salt of the NHC precursors indicated as H4L-1(PF6)4, H2L-2(PF6)2, and H2L-4(PF6)2. H4L-1(PF6)4, which is the precursor of ligand L-1, was formed as mixed crystals of two geometric isomers, i.e., H4L-1a(PF6)4(major) and H4L-1b(PF6)4(minor), each of which was not isolated as single species. Ag2O reacted with the mixed isomers of H4L-1(PF6)4to give a single, pure crystalline silver(I) complex Ag-1a with one isomer (L-1a) as the major product. The molecular structures of the precursors and their silver(I) complexes were determined by X-ray crystallography. A mononuclear NHC-silver(I) complex (Ag-3) was prepared by the reaction of Ag2O with the precursor HL-3Cl. The silver(I) complexes and NHC precursors prepared here were characterized by CHN elemental analysis, FTIR, Thermogravimetry/Differential thermal analysis, X-ray crystallography and solution (1H and13C) NMR spectroscopy. Organometallic silver(I) complexes Ag-1a, Ag-2, and Ag-4 were dinuclear C-Ag-C bonding complexes, whereas Ag-3 was a mononuclear C-Ag-Cl bonding complex. These complexes are highly soluble in organic solvents such as acetone, acetonitrile, and dimethyl sulfoxide, and light-stable in the solid-state and in solution over one year. The antimicrobial activities of four silver(I) complexes and their NHC precursors against selected bacteria, yeasts, and molds in water-suspension systems were evaluated via the minimum inhibitory concentration; the activities were strongly dependent on the molecular structures of the dinuclear silver(I) complexes, which suggests a structure-activity relationship.
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Sakamoto
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Soichiro
authors.initials: S
authors.lastname: Morozumi
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Yanagawa
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Mizuki
authors.initials: M
authors.lastname: Toyama
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Takayama
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan.
authors.forename: Noriko Chikaraishi
authors.initials: NC
authors.lastname: Kasuga
authors.affiliation: Department of Chemistry, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan. Electronic address: nomiya@kanagawa-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Nomiya
mesh_terms: D000890:Anti-Infective Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D001419:Bacteria / Q000254:growth & development*; D018360:Crystallography, X-Ray; D005658:Fungi / Q000254:growth & development*; D009682:Magnetic Resonance Spectroscopy; D008697:Methane / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D015394:Molecular Structure; D012834:Silver / Q000737:chemistry / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; C030011:carbene; D012834:Silver; D008697:Methane
keywords: Antimicrobial activities; Dinuclear silver(I) complexes; Molecular structures; N-heterocyclic carbene (NHC) ligands; Structure-activity relationship