title: Syntheses, electronic structures, and EPR/UV-vis-NIR spectroelectrochemistry of nickel(II), copper(II), and zinc(II) complexes with a tetradentate ligand based on S-methylisothiosemicarbazide.
abstract: Template condensation of 3,5-di-tert-butyl-2-hydroxybenzaldehyde S-methylisothiosemicarbazone with pentane-2,4-dione and triethyl orthoformate at elevated temperatures resulted in metal complexes of the type M(II)L, where M = Ni and Cu and H(2)L = a novel tetradentate ligand. These complexes are relevant to the active site of the copper enzymes galactose oxidase and glyoxal oxidase. Demetalation of Ni(II)L with gaseous hydrogen chloride in chloroform afforded the metal-free ligand H(2)L. Then by the reaction of H(2)L with Zn(CH(3)COO)(2)·2H(2)O in a 1:1 molar ratio in 1:2 chloroform/methanol, the complex Zn(II)L(CH(3)OH) was prepared. The three metal complexes and the prepared ligand were characterized by spectroscopic methods (IR, UV-vis, and NMR spectroscopy), X-ray crystallography, and DFT calculations. Electrochemically generated one-electron oxidized metal complexes [NiL](+), [CuL](+), and [ZnL(CH(3)OH)](+) and the metal-free ligand cation radical [H(2)L](+•) were studied by EPR/UV-vis-NIR and DFT calculations. These studies demonstrated the interaction between the metal ion and the phenoxyl radical.
authors.affiliation: Institute of Inorganic Chemistry, University of Vienna, Vienna, Austria. vladimir.arion@univie.ac.at
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Arion
authors.forename: Peter
authors.initials: P
authors.lastname: Rapta
authors.forename: Joshua
authors.initials: J
authors.lastname: Telser
authors.forename: Sergiu S
authors.initials: SS
authors.lastname: Shova
authors.forename: Martin
authors.initials: M
authors.lastname: Breza
authors.forename: Karol
authors.initials: K
authors.lastname: Luspai
authors.forename: Jozef
authors.initials: J
authors.lastname: Kozisek
mesh_terms: D003300:Copper / Q000737:chemistry*; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D008024:Ligands; D008968:Molecular Conformation; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared; D013237:Stereoisomerism; D013882:Thiosemicarbazones / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D013882:Thiosemicarbazones; D003300:Copper; D009532:Nickel; D015032:Zinc