Browsing by Author "Eckert, J"

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    Hydrogen bond dynamics, conformational flexibility and polymorphism in antipsychotics
    (Australian Institute of Physics, 2017-02-03) Pereira, JEM; Eckert, J; Yu, DH; Mole, RA; Bordallo, HN
    This work is related to the investigation of three different antipsychotics, one of each generation: aripiprazole (C23H27Cl2N3O2), haloperidol (C21H23ClFNO2) and quetiapine hemifumarate (C23H27N3O4S) using a combination of Inelastic Neutron Scattering (INS) and Density Functional Theory (DFT). These substances were selected because their crystalline structure and the concerns related to their polymorphism are somehow known. We report on data obtained using the direct geometry spectrometer PELICAN, located at the Australian Centre for Neutron Scattering (ACNS, formerly the Bragg Institute) at the Australian Nuclear Research and Technology Organisation (ANSTO). Polymorphic transformations and purity of the samples were determined by calorimetric studies, while their structures were verified by X-rays diffraction. Furthermore, the origin of each of the observed modes is supported by theoretical data provided by Density Functional Theory calculations (DFT).
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    Hydrogen bond dynamics, conformational flexibility and polymorphism in antipsychotics
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Pereira, JEM; Eckert, J; Yu, DH; Mole, RA; Bordallo, HN
    This work is related to the investigation of three different antipsychotics, one of each generation: aripiprazole (C23H27Cl2N3O2), haloperidol (C21H23ClFNO2) and quetiapine hemifumarate (C23H27N3O4S) using a combination of Inelastic Neutron Scattering (INS) and Density Functional Theory (DFT). These substances were selected because their crystalline structure and the concerns related to their polymorphism are somehow known [1]. We report on data obtained using the direct geometry spectrometer PELICAN, located at the Australian Centre for Neutron Scattering (ACNS, formerly the Bragg Institute) at the Australian Nuclear Research and Technology Organisation (ANSTO). Polymorphic transformations and purity of the samples were determined by calorimetric studies, while their structures were verified by X-rays diffraction. Furthermore, the origin of each of the observed modes is supported by theoretical data provided by Density Functional Theory calculations (DFT).
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    Methyl dynamics flattens barrier to proton transfer in crystalline tetraacetylethane
    (American Chemical Society, 2012-03-08) Kearley, GJ; Stare, J; Kutteh, R; Daemen, LL; Hartl, MA; Eckert, J
    We analyze the interplay between proton transfer in the hydrogen-bond bridge, O center dot center dot center dot H center dot center dot center dot O, and lattice dynamics in the model system tetraacetylethane (TAB) (CH(3)CO)(2)CH=CH(COCH(3))(2) using density functional theory. Lattice dynamics calculations and molecular dynamics simulations are validated against neutron scattering data. Hindrance to the cooperative reorientation of neighboring methyl groups at low temperatures gives a preferred O atom for the bridging proton. The amplitude of methyl torsions becomes larger with increasing temperature, so that the free-energy minimum for the proton becomes flat over 0.2 angstrom. For the isolated molecule, however, we show an almost temperature-independent symmetric double-well potential persists. This difference arises from the much higher barriers to methyl torsion in the crystal that make the region of torsional phase space that is most crucial for symmetrization poorly accessible. Consequently, the proton-transfer potential remains asymmetric though flat at the base, even at room temperature in the solid. © 2012, American Chemical Society.