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Now showing items 17 - 18 of 18

  • Synthesis and structural characterization of new oxovanadium(IV) complexes derived from azo-5-pyrazolone with prospective medical importance

    Bagdatli, Emine   Altuntas, Eylem   Sayin, Ulku  

    Four novel o-hydroxy substituted aryl-(m H, -Cl, Br, CH3) azo-5-pyrazolone compounds (2a-d, respectively) were synthesized as azo-group containing ligands by diazotization of aryl amines then coupled with 1-(4-chlorophenyl)-3-isopropyl-1H-pyrazol-5(4H)-one (1) and the structures were confirmed by FTIR, UV-Visible, GC-MS or ESI-LCMS and NMR spectroscopic techniques. As a result, the first synthesis of azo-5-pyrazolone based oxovanadium(IV) complexes (3a d) was achieved by interaction of 2a d with half equivalent of vanadyl sulphate pentahydrate in a methanolic medium with moderate to high yields (67, 74, 60, 71 for 3a d, respectively). The resulting complexes were characterized using FTIR, UV-Visible, ESI-LCMS and EPR spectroscopic techniques as well as with thermogravimetric (TG/DTG) analysis. They have the composition [VO(L)(2)]center dot H2O; (3a c) or [VO(L)(2)]center dot CH3OH; (3d) where LH is an azo-5-pyrazolone compound as the ligand (2a d). The electronic spectra of the complexes are typical of oxovanadium(IV) complexes showing a low intensity band near 500 nm. Spectroscopic results have shown that azo-5-pyrazolone compounds have acted bidendate and the coordination sites are hydroxyl-substituent on the-azo phenyl-aromatic ring and the pyrazolone carbonyl-moiety. The thermal data confirm that the complexes have methanol (3a c) or water (3d) molecule outside the coordination sphere and the complexes show similar thermogravimetric decomposition fragments which are consistent with the proposed structures. A distorted octahedral geometry has been proposed for these complexes mainly with EPR and the other spectral techniques. (C) 2016 Elsevier B.V. All rights reserved.
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  • EPR investigation of gamma irradiated single crystal guaifenesin:A combined experimental and computational study

    Tasdemir, Halil Ugur   Sayin, Ulku   Turkkan, Ercan   Ozmen, Ayhan  

    Gamma irradiated single crystal of Guaifenesin (Glyceryl Guaiacolate), an important expectorant drug, were investigated with Electron Paramagnetic Resonance (EPR) spectroscopy between 123 and 333 K temperature at different orientations in the magnetic field. Considering the chemical structure and the experimental spectra of the gamma irradiated single crystal of guaifenesin sample, we assumed that alkoxy or alkyl-type paramagnetic species may be produced by irradiation. Depending on this assumption, eight possible alkoxy and alkyl-type radicals were modeled and EPR parameters of these modeled radicals were calculated using the B3LYP/6-311+ +G(d,p)-level of density functional theory (DFT). Theoretically calculated values of alkyl-type modeled radical(R3) are in good agreement with experimentally determined EPR parameters of single crystal. Furthermore, simulation spectra which are obtained by using the thepretical initial values are well matched with the experimental spectra. It was determined that a stable C alpha H2 alpha C beta H beta C gamma H2 gamma (R3) alkyl radical was produced in the host crystal as a result of gamma irradiation. (C) 2015 Elsevier Ltd. All rights reserved.
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