title: Synthesis, structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands.
abstract: Twelve zinc(II) complexes with thiosemicarbazone and semicarbazone ligands were prepared and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FT-IR and 1H and 13C NMR spectroscopy. Seven three-dimensional structures of zinc(II) complexes were determined by single-crystal X-ray analysis. Their antimicrobial activities were evaluated by MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 5- and 6-coordinate zinc(II) complexes with a tridentate thiosemicarbazone ligand (Hatsc), ([Zn(atsc)(OAc)](n) 1, [Zn(Hatsc)(2)](NO(3))(2).0.3H(2)O 2, [ZnCl(2)(Hatsc)] 3 and [Zn(SO(4))(Hatsc)(H(2)O)].H(2)O 4 [Hatsc=2-acetylpyridine(thiosemicarbazone)]), showed antimicrobial activities against test organisms, which were different from those of free ligands or the starting zinc(II) compounds. Especially, complex 2 showed effective activities against P. aeruginosa, C. albicans and moderate activities against S. cerevisiae and two molds. These facts are in contrast to the results that the 5- or 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridine-4N-morpholinethiosemicarbazone, ([Zn(mtsc)(2)].0.2EtOH 5, the previously reported catena-poly [Zn(mtsc)-mu-(OAc-O,O')](n) and [Zn(NO(3))(2)(Hmtsc)] [Hmtsc=2-acetylpyridine (4N-morpholyl thiosemicarbazone)]), showed no activities against the test microorganisms. The 5- and 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridinesemicarbazone, ([Zn(OAc)(2)(Hasc)] 6 and [Zn(Hasc)(2)](NO(3))(2) 7 [Hasc=2-acetylpyridine(semicarbazone)]), showed no antimicrobial activities against bacteria, yeasts and molds. Complex [ZnCl(2)(Hasc)] 8, which was isostructural to complex 3, showed modest activity against Gram-positive bacterium, B. subtilis. The 1:1 complexes of zinc(II) with pentadentate thiosemicarbazone ligands, ([Zn(dmtsc)](n) 9 and [Zn(datsc)](n) 10 [H(2)dmtsc=2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone) and H(2)datsc=2,6-diacetylpyridine bis(thiosemicarbazone)]), did not inhibit the growth of the test organisms. On the contrary, 7-coordinate zinc(II) complexes with one pentadentate semicarbazone ligand and two water molecules, ([Zn(H(2)dasc)(H(2)O)(2)](OAc)(2).5.3H(2)O 11 and [Zn(H(2)dasc)(H(2)O)(2)](NO(3))(2).H(2)O 12 [H(2)dasc=2,6-diacetylpyridine bis(semicarbazone)]), showed modest to moderate activities against bacteria. Based on the X-ray structures, the structure-activity correlation for the antimicrobial activities was elucidated. The zinc(II) complexes with 4N-substituted ligands showed no antimicrobial activities. In contrast to the previously reported nickel(II) complexes, properties of the ligands such as the ability to form hydrogen bonding with a counter anion or hydrated water molecules or the less bulkiness of the 4N moiety would be a more important factor for antimicrobial activities than the coordination number of the metal ion for the zinc(II) complexes.
authors.affiliation: Department of Materials Science, Faculty of Science, Kanagawa University, Hiratsuka, 259-1293, Kanagawa, Japan.
authors.forename: Noriko Chikaraishi
authors.initials: NC
authors.lastname: Kasuga
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Sekino
authors.forename: Motoki
authors.initials: M
authors.lastname: Ishikawa
authors.forename: Ayano
authors.initials: A
authors.lastname: Honda
authors.forename: Masaki
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Saori
authors.initials: S
authors.lastname: Nakano
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Shimada
authors.forename: Chisa
authors.initials: C
authors.lastname: Koumo
authors.forename: Kenji
authors.initials: K
authors.lastname: Nomiya
mesh_terms: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D001419:Bacteria / Q000187:drug effects; D018360:Crystallography, X-Ray; D008024:Ligands; D008826:Microbial Sensitivity Tests; D003904:Mitosporic Fungi / Q000187:drug effects; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D012664:Semicarbazones / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship; D013882:Thiosemicarbazones / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D015003:Yeasts / Q000187:drug effects; D015032:Zinc / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D000890:Anti-Infective Agents; D008024:Ligands; D009942:Organometallic Compounds; D012664:Semicarbazones; D013882:Thiosemicarbazones; D015032:Zinc