title: Synthesis and structural characterization of silver(I), aluminium(III) and cobalt(II) complexes with 4-isopropyltropolone (hinokitiol) showing noteworthy biological activities. Action of silver(I)-oxygen bonding complexes on the antimicrobial activities.
abstract: Through two unequivalent oxygen donor atoms of the hinokitiol (Hhino; C10H12O2; 4-isopropyltropolone) ligand that showed noteworthy biological activities, the dimeric, silver(I)-oxygen bonding complex [Ag(hino)]2 1, the monomeric aluminium(III) complex [Al(hino)3].0.5H2O 4 and the cobalt(II) complex "[Co(hino)2]2.H2O" 6 were synthesized and characterized with elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR and solution (1H and 13C) NMR spectroscopy. The crystal structure of 1 was determined by Rietveld analysis based on X-ray powder diffraction (XPD) data and those of [Al(hino)3].MeOH 4a and [Co(hino)2(EtOH)]2 6a, being obtained as yellow block crystals and red platelet crystals, respectively, by crystallization of 4 and 6, were determined by single-crystal X-ray analysis. The antimicrobial activities of 1, 4 and 6, evaluated with minimum inhibitory concentration (MIC; microg ml(-1)), were compared with those of other metal complexes (M=Na, Li, Cs, Ca, V, Zn) with the hino- ligand. The antimicrobial activities observed in the alkali-metal salts strongly suggested that they were attributed to the effect of the anionic hino- species. The antimicrobial activities of 1 were significantly enhanced, whereas those of other metal complexes were suppressed, compared with those of the neutral Hhino and anionic hino- molecules. The antimicrobial activities observed in 1 were comparable with those of other recently found silver(I)-oxygen bonding complexes, the ligands of which had no activity. Thus, it is proposed that the antimicrobial activities of the silver(I)-oxygen bonding complexes are due to a direct interaction or complexation of the silver(I) ion with biological ligands such as protein, enzyme and membrane, and the coordinating ligands of the silver(I) complexes play the role of a carrier of the silver(I) ion to the biological system.
authors.affiliation: Department of Materials Science, Faculty of Science, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan. nomiya@chem.kanagawa-u.ac.jp
authors.forename: Kenji
authors.initials: K
authors.lastname: Nomiya
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshizawa
authors.forename: Ken
authors.initials: K
authors.lastname: Tsukagoshi
authors.forename: Noriko Chikaraishi
authors.initials: NC
authors.lastname: Kasuga
authors.forename: Shoko
authors.initials: S
authors.lastname: Hirakawa
authors.forename: Jun
authors.initials: J
authors.lastname: Watanabe
mesh_terms: D000535:Aluminum / Q000737:chemistry; D000890:Anti-Infective Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D003035:Cobalt / Q000737:chemistry; D018360:Crystallography, X-Ray; D008670:Metals / Q000737:chemistry*; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D015394:Molecular Structure; D039821:Monoterpenes / Q000737:chemistry* / Q000494:pharmacology; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D010100:Oxygen / Q000737:chemistry; D012834:Silver / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D014334:Tropolone / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000494:pharmacology
chemical_list: D000890:Anti-Infective Agents; D008670:Metals; D039821:Monoterpenes; D009942:Organometallic Compounds; D003035:Cobalt; D012834:Silver; D014334:Tropolone; D000535:Aluminum; D010100:Oxygen; C009479:beta-thujaplicin