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Oleg N Antzutkin - One of the best experts on this subject based on the ideXlab platform.
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a pyridine adduct of bis di iso butyldithiocarbamato s s cadmium ii multinuclear 13c 15n 113cd cp mas nmr spectroscopy crystal and molecular structure and thermal behaviour
Inorganica Chimica Acta, 2011Co-Authors: T. A. Rodina, A V Ivanov, A V Gerasimenko, M A Ivanov, A S Zaeva, Tatyana S Philippova, Oleg N AntzutkinAbstract:Abstract Crystalline bis(N,N-di-iso-butyldithiocarbamato-S,S′)(pyridine)cadmium(II) – adduct 1 was prepared and studied by means of multinuclear 13C, 15N, 113Cd CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA). In molecular structure 1, the cadmium atom coordinates with four sulphur atoms and one nitrogen atom of pyridine, forming a coordination polyhedron [CdS4N], whose geometry is an almost ideal tetragonal pyramidal (C4v). The coordinated py molecule is in the apical position, while two structurally non-equivalent di-iso-butyldithiocarbamate ligands, playing the same terminal S,S′-chelating function, define the basal plane. To characterise additionally the structural state of the cadmium atom in this fivefold coordination, 113Cd Chemical Shift anisotropy (CSA) parameters, δaniso and η, were calculated from experimental MAS NMR spectra that revealed an almost axially symmetric 113Cd Chemical Shift Tensor. From a combination of TG and DSC measurements taken under an argon atmosphere, we found that the mass of adduct 1 is lost in two steps involving initial desorption of coordinated py molecules with subsequent thermal destruction of liberated cadmium(II) di-iso-butyldithiocarbamate, with yellow-orange, fine-powdered solid CdS as the final product.
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a pyridine adduct of bis di iso butyldithiocarbamato s s cadmium ii multinuclear 13c 15n 113cd cp mas nmr spectroscopy crystal and molecular structure and thermal behaviour
Inorganica Chimica Acta, 2011Co-Authors: T. A. Rodina, A V Ivanov, A V Gerasimenko, M A Ivanov, A S Zaeva, Tatyana S Philippova, Oleg N AntzutkinAbstract:Crystalline bis(N, N-di-iso-butyldithiocarbamato-S,S')(pyridine)cadmium(II) - adduct 1 was prepared and studied by means of multinuclear (13)C, (15)N, (113)Cd CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA). In molecular structure 1, the cadmium atom coordinates with four sulphur atoms and one nitrogen atom of pyridine, forming a coordination polyhedron [CdS(4)N], whose geometry is an almost ideal tetragonal pyramidal (C(4v)). The coordinated py molecule is in the apical position, while two structurally non-equivalent di-iso-butyldithiocarbamate ligands, playing the same terminal S,S'-chelating function, define the basal plane. To characterise additionally the structural state of the cadmium atom in this fivefold coordination, (113)Cd Chemical Shift anisotropy (CSA) parameters, delta(aniso) and eta, were calculated from experimental MAS NMR spectra that revealed an almost axially symmetric (113)Cd Chemical Shift Tensor. From a combination of TG and DSC measurements taken under an argon atmosphere, we found that the mass of adduct 1 is lost in two steps involving initial desorption of coordinated py molecules with subsequent thermal destruction of liberated cadmium(II) di-iso-butyldithiocarbamate, with yellow-orange, fine-powdered solid CdS as the final product. (C) 2011 Elsevier B.V. All rights reserved.
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synthesis structure and 13c and 31p cp mas nmr of the tetraphenylantimony v di iso propyl phosphorodithioate complex sb c6h5 4 s2p o iso c3h7 2 and its solvated form sb c6h5 4 s2p o iso c3h7 2 1 2c6h6 an example of the monodentate coordination of dithio ligands
Russian Journal of Inorganic Chemistry, 2009Co-Authors: M A Ivanov, A V Ivanov, A V Gerasimenko, V V Sharutin, Oleg N AntzutkinAbstract:The crystalline tetraphenylantimony(V) O,O′-di-iso-propyl phosphorodithioate complex [Sb(C6H5)4{S2P(O-i-C3H7)2}](I) and its solvated form [Sb(C6H5)4{S2P(O-i-C3H7)2}] · 1/2C6H6(II) were synthesized. Solid compounds I and II were studied by MAS NMR (13C, 31P). The 31P NMR Chemical Shift anisotropy 31P δaniso = (δ zz − δiso) and asymmetry parameter η = (δ yy − δ xx )/(δ zz − δiso) were calculated using χ 2 plots constructed on the basis of the 31P MAS NMR data. The O,O′-di-iso-propyl phosphorodithioate ligands in both complexes are characterized by predominantly the axially symmetric 31P Chemical Shift Tensor (for the case δ zz < δ xx ≈ δ yy ) with close values of anisotropy parameters (δaniso and η), which reflects their identical S-monodentate structural function. X-ray crystallography showed that II has a trigonal-bipyramidal molecular structure with the uncommon monodentate coordination of the Dtph ligands through an S atom in an axial position of the trigonal bipyramid and the benzene molecule in the outer sphere.
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synthesis structural and multinuclear natural abundance 13c 31p 195pt cp mas nmr studies of crystalline o o dialkyldithiophosphate platinum ii complexes
Russian Journal of Coordination Chemistry, 2008Co-Authors: A V Ivanov, A V Gerasimenko, M A Ivanov, I A Lutsenko, Oleg N AntzutkinAbstract:Platinum(II) O,O′-dicyclohexyl dithiophosphate [Pt{S2P(O-cyclo-C6H11)2}2] (I) and platinum(II) O,O′-diisopropyl dithiophosphate [Pt{S2P(O-iso-C3H7)2}2] (II) complexes were obtained and studied by solidstate 13C, 31P, and 195Pt CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular structure I were found to be coordinated by platinum in S,S′-bidentate fashion to form the planar chromophore [PtS4] (single-crystal X-ray diffraction data). For complex II, a new α-form (α-II) was obtained and identified by 31P MAS NMR spectroscopy. The 31P Chemical Shift anisotropy δaniso and the asymmetry parameter η of the 31P Chemical Shift Tensor were calculated from the whole MAS spectra.
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solid state nmr and exafs spectroscopic characterization of polycrystalline copper i o o dialkyldithiophosphate cluster compounds formation of copper i o o diisobutyldithiophosphate compounds on the surface of synthetic chalcocite
Chemistry: A European Journal, 2006Co-Authors: Daniela Rusanova, Willis Forsling, Kevin J Pike, Ingmar Persson, John V Hanna, Ray Dupree, Oleg N AntzutkinAbstract:A number of polycrystalline copper(I) O,O'-dialkyldithiophosphate cluster compounds with Cu-4, Cu-6, and Cu-8 cores were synthesized and characterized by using extended X-ray absorption fine-structure (EXAFS) spectroscopy. The structural relationship of these compounds is discussed. The polycrystalline copper(i) O,O'-diisobutyldithiophosphate cluster compounds, [Cu-8{S2P(OiBu)(2),}(6)(S)] and [CU6{S2P(OiBU)(2)}(6)], were also characterized by using P-31 CP/MAS NMR (CP = cross polarization, MAS = magic-angle spinning) and static Cu-65 NMR spectroscopies (at different magnetic fields) and powder X-ray diffraction (XRD) analysis. Comparative analyses of the P-31 Chemical-Shift Tensor, and the Cu-65 Chemical Shift and quadrupolar-splitting parameters, estimated from the experimental NMR spectra of the polycrystalline copper(I) cluster compounds, are presented. The adsorption mechanism of the potassium O,O'-diisobutyldithiophosphate collector, K[S2P(OiBu)(2)], at the surface of synthetic chalcocite (Cu2S) was studied by means of solid-state P-31 CP/MAS NMR spectroscopy and scanning electron microscopy (SEM). P-31 NMR resonance lines from collector-treated chalcocite surfaces were assigned to a mixture of [Cu-8{S2P(OiBu)(2)}(6)(S)] and [Cu-6- {S2P(OiBu)(2)}(6)] compounds.
Mei Hong - One of the best experts on this subject based on the ideXlab platform.
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cα Chemical Shift Tensors in helical peptides by dipolar modulated Chemical Shift recoupling nmr
Journal of Biomolecular NMR, 2002Co-Authors: Xiaolan Yao, Satoru Yamaguchi, Mei HongAbstract:The Cα Chemical Shift Tensors of proteins contain information on the backbone conformation. We have determined the magnitude and orientation of the Cα Chemical Shift Tensors of two peptides with α-helical torsion angles: the Ala residue in G*AL (φ=−65.7°, ψ=−40°), and the Val residue in GG*V (φ=−81.5°, ψ=−50.7°). The magnitude of the Tensors was determined from quasi-static powder patterns recoupled under magic-angle spinning, while the orientation of the Tensors was extracted from Cα–Hα and Cα–N dipolar modulated powder patterns. The helical Ala Cα Chemical Shift Tensor has a span of 36 ppm and an asymmetry parameter of 0.89. Its σ11 axis is 116° ± 5° from the Cα–Hα bond while the σ22 axis is 40° ± 5° from the Cα–N bond. The Val Tensor has an anisotropic span of 25 ppm and an asymmetry parameter of 0.33, both much smaller than the values for β-sheet Val found recently (Yao and Hong, 2002). The Val σ33 axis is tilted by 115° ± 5° from the Cα–Hα bond and 98° ± 5° from the Cα–N bond. These represent the first completely experimentally determined Cα Chemical Shift Tensors of helical peptides. Using an icosahedral representation, we compared the experimental Chemical Shift Tensors with quantum Chemical calculations and found overall good agreement. These solid-state Chemical Shift Tensors confirm the observation from cross-correlated relaxation experiments that the projection of the Cα Chemical Shift Tensor onto the Cα–Hα bond is much smaller in α-helices than in β-sheets.
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determination of calpha Chemical Shift Tensor orientation in peptides by dipolar modulated Chemical Shift recoupling nmr spectroscopy
Journal of the American Chemical Society, 2002Co-Authors: Xiaolan Yao, Mei HongAbstract:We present a new method for determining the orientation of Chemical Shift Tensors in polycrystalline solids with site resolution and demonstrate its application to the determination of the Calpha Chemical Shift Tensor orientation in a model peptide with beta-sheet torsion angles. The Tensor orientation is obtained under magic angle spinning by modulating a recoupled Chemical Shift anisotropy (CSA) pattern with various dipolar couplings. These dipolar-modulated Chemical Shift patterns constitute the indirect dimension of a 2D spectrum and are resolved according to the isotropic Chemical Shifts of different sites in the direct dimension. These dipolar-modulated CSA spectra are equivalent to the projection of a 2D static separated-local-field spectrum onto its Chemical Shift dimension, except that its dipolar dimension is multiplied with a modulation function. Both (13)C-(1)H and (13)C-(15)N dipolar couplings can modulate the CSA spectra of the Calpha site in an amino acid and yield the relative orientations of the Chemical Shift principal axes to the C-H and C-N bonds. We demonstrate the C-H and C-N modulated CSA experiments on methylmalonic acid and N-tBoc-glycine, respectively. The MAS results agree well with the results of the 2D separated-local-field spectra, thus confirming the validity of this MAS dipolar-modulation approach. Using this technique, we measured the Val Calpha Tensor orientation in N-acetylvaline, which has beta-sheet torsion angles. The sigma(11) axis is oriented at 158 degrees (or 22 degrees) from the C-H bond, while the sigma(22) axis is tilted by 144 degrees (or 36 degrees) from the C-N bond. Both the orientations and the magnitude of this Chemical Shift Tensor are in excellent agreement with quantum Chemical calculations.
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determination of the peptide torsion angle φ by15n Chemical Shift and13cα 1hαdipolar Tensor correlation in solid state mas nmr
Journal of Magnetic Resonance, 1998Co-Authors: Mei Hong, John D GrossAbstract:Abstract We demonstrate a dipolar-Chemical Shift correlation technique for sign-sensitive determination of the torsion angle φ in solid peptides and proteins under magic-angle spinning. The indirect dimension of the experiment is obtained by separate but synchronous evolution of the magnetization under the 15 N Chemical Shift and the C-H dipolar coupling. The resulting sum and difference spectrum of the two frequencies, with more than ten independent sidebands, depends strongly on the relative orientation of the 15 N Chemical Shift Tensor and the C α -H α bond. This relative orientation reflects the C(O) i−1 -N-C α -C(O) i torsion angle. The technique can distinguish φ angles over the full range of 360° when the amide 15 N Chemical Shift Tensor does not possess reflection symmetry with respect to the peptide plane. Thus it complements our previous HNCH experiment, in which two mirror-symmetric conformers of the H N -N bond relative to the C α -H α bond around the N-C α axis cannot be distinguished.
A V Ivanov - One of the best experts on this subject based on the ideXlab platform.
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a pyridine adduct of bis di iso butyldithiocarbamato s s cadmium ii multinuclear 13c 15n 113cd cp mas nmr spectroscopy crystal and molecular structure and thermal behaviour
Inorganica Chimica Acta, 2011Co-Authors: T. A. Rodina, A V Ivanov, A V Gerasimenko, M A Ivanov, A S Zaeva, Tatyana S Philippova, Oleg N AntzutkinAbstract:Abstract Crystalline bis(N,N-di-iso-butyldithiocarbamato-S,S′)(pyridine)cadmium(II) – adduct 1 was prepared and studied by means of multinuclear 13C, 15N, 113Cd CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA). In molecular structure 1, the cadmium atom coordinates with four sulphur atoms and one nitrogen atom of pyridine, forming a coordination polyhedron [CdS4N], whose geometry is an almost ideal tetragonal pyramidal (C4v). The coordinated py molecule is in the apical position, while two structurally non-equivalent di-iso-butyldithiocarbamate ligands, playing the same terminal S,S′-chelating function, define the basal plane. To characterise additionally the structural state of the cadmium atom in this fivefold coordination, 113Cd Chemical Shift anisotropy (CSA) parameters, δaniso and η, were calculated from experimental MAS NMR spectra that revealed an almost axially symmetric 113Cd Chemical Shift Tensor. From a combination of TG and DSC measurements taken under an argon atmosphere, we found that the mass of adduct 1 is lost in two steps involving initial desorption of coordinated py molecules with subsequent thermal destruction of liberated cadmium(II) di-iso-butyldithiocarbamate, with yellow-orange, fine-powdered solid CdS as the final product.
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a pyridine adduct of bis di iso butyldithiocarbamato s s cadmium ii multinuclear 13c 15n 113cd cp mas nmr spectroscopy crystal and molecular structure and thermal behaviour
Inorganica Chimica Acta, 2011Co-Authors: T. A. Rodina, A V Ivanov, A V Gerasimenko, M A Ivanov, A S Zaeva, Tatyana S Philippova, Oleg N AntzutkinAbstract:Crystalline bis(N, N-di-iso-butyldithiocarbamato-S,S')(pyridine)cadmium(II) - adduct 1 was prepared and studied by means of multinuclear (13)C, (15)N, (113)Cd CP/MAS NMR spectroscopy, single-crystal X-ray diffraction and simultaneous thermal analysis (STA). In molecular structure 1, the cadmium atom coordinates with four sulphur atoms and one nitrogen atom of pyridine, forming a coordination polyhedron [CdS(4)N], whose geometry is an almost ideal tetragonal pyramidal (C(4v)). The coordinated py molecule is in the apical position, while two structurally non-equivalent di-iso-butyldithiocarbamate ligands, playing the same terminal S,S'-chelating function, define the basal plane. To characterise additionally the structural state of the cadmium atom in this fivefold coordination, (113)Cd Chemical Shift anisotropy (CSA) parameters, delta(aniso) and eta, were calculated from experimental MAS NMR spectra that revealed an almost axially symmetric (113)Cd Chemical Shift Tensor. From a combination of TG and DSC measurements taken under an argon atmosphere, we found that the mass of adduct 1 is lost in two steps involving initial desorption of coordinated py molecules with subsequent thermal destruction of liberated cadmium(II) di-iso-butyldithiocarbamate, with yellow-orange, fine-powdered solid CdS as the final product. (C) 2011 Elsevier B.V. All rights reserved.
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polymeric thallium i o o diisopropyl dithiophosphate tl s2p o iso c3h7 2 n synthesis structure and 13c and 31p cp mas nmr spectra
Russian Journal of Coordination Chemistry, 2009Co-Authors: A V Ivanov, A V Gerasimenko, V A Konfederatov, Annacarin LarssonAbstract:The crystalline polymeric thallium(I) O,O′-diisopropyl dithiophosphate [Tl{S2P(O-iso-C3H7)2}] n (I) was obtained and examined by solid-state 13C and 31P CP/MAS NMR spectroscopy. Diagrams of the χ2 statistic were constructed from the complete 31P MAS NMR spectra and used to calculate the 31P Chemical Shift anisotropy (δaniso = (δ zz − δiso)) and the asymmetry parameter (η = (δ yy − δ xx )/(δ zz − δiso)). The 31P Chemical Shift Tensor has a nearly axial symmetry (η = 0.22, δ zz < δ yy ≈ δ xx ). The MAS NMR spectral patterns correspond to the negative sign of δaniso (δ zz < δ yy < δ xx ), which indicates bridging or chelating-bridging coordination of the dithiophosphate ligands (Dtph). X-ray diffraction analysis revealed a polymeric structure of compound I. The polymer chain consists of alternating mononuclear [Tl{S2P(O-iso-C3H7)2}] molecules with opposite spatial orientations. The Dtph ligands are coordinated in a mixed, chelating-μ3-bridging fashion. The shape of the 31P NMR signal was interpreted in terms of the 31P-203,205Tl coupling pattern proposed from crystallographic data.
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synthesis structure and 13c and 31p cp mas nmr of the tetraphenylantimony v di iso propyl phosphorodithioate complex sb c6h5 4 s2p o iso c3h7 2 and its solvated form sb c6h5 4 s2p o iso c3h7 2 1 2c6h6 an example of the monodentate coordination of dithio ligands
Russian Journal of Inorganic Chemistry, 2009Co-Authors: M A Ivanov, A V Ivanov, A V Gerasimenko, V V Sharutin, Oleg N AntzutkinAbstract:The crystalline tetraphenylantimony(V) O,O′-di-iso-propyl phosphorodithioate complex [Sb(C6H5)4{S2P(O-i-C3H7)2}](I) and its solvated form [Sb(C6H5)4{S2P(O-i-C3H7)2}] · 1/2C6H6(II) were synthesized. Solid compounds I and II were studied by MAS NMR (13C, 31P). The 31P NMR Chemical Shift anisotropy 31P δaniso = (δ zz − δiso) and asymmetry parameter η = (δ yy − δ xx )/(δ zz − δiso) were calculated using χ 2 plots constructed on the basis of the 31P MAS NMR data. The O,O′-di-iso-propyl phosphorodithioate ligands in both complexes are characterized by predominantly the axially symmetric 31P Chemical Shift Tensor (for the case δ zz < δ xx ≈ δ yy ) with close values of anisotropy parameters (δaniso and η), which reflects their identical S-monodentate structural function. X-ray crystallography showed that II has a trigonal-bipyramidal molecular structure with the uncommon monodentate coordination of the Dtph ligands through an S atom in an axial position of the trigonal bipyramid and the benzene molecule in the outer sphere.
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synthesis structural and multinuclear natural abundance 13c 31p 195pt cp mas nmr studies of crystalline o o dialkyldithiophosphate platinum ii complexes
Russian Journal of Coordination Chemistry, 2008Co-Authors: A V Ivanov, A V Gerasimenko, M A Ivanov, I A Lutsenko, Oleg N AntzutkinAbstract:Platinum(II) O,O′-dicyclohexyl dithiophosphate [Pt{S2P(O-cyclo-C6H11)2}2] (I) and platinum(II) O,O′-diisopropyl dithiophosphate [Pt{S2P(O-iso-C3H7)2}2] (II) complexes were obtained and studied by solidstate 13C, 31P, and 195Pt CP/MAS NMR spectroscopy. The dithiophosphate (Dtph) ligands in molecular structure I were found to be coordinated by platinum in S,S′-bidentate fashion to form the planar chromophore [PtS4] (single-crystal X-ray diffraction data). For complex II, a new α-form (α-II) was obtained and identified by 31P MAS NMR spectroscopy. The 31P Chemical Shift anisotropy δaniso and the asymmetry parameter η of the 31P Chemical Shift Tensor were calculated from the whole MAS spectra.
David M Grant - One of the best experts on this subject based on the ideXlab platform.
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13c nmr Chemical Shifts of the triclinic and monoclinic crystal forms of valinomycin
Journal of Biomolecular NMR, 2004Co-Authors: Tsunenori Kameda, Gary Mcgeorge, Anita M. Orendt, David M GrantAbstract:Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state 13C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic Chemical Shifts between the two spectra. For the triclinic form, the carbon Chemical Shift Tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic Chemical Shift, δiso, for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, δ22. Additionally it was found that the smallest Shift component, δ33, for the L-lactic acid (L-Lac) and D-α-hydroxyisovaleric acid (D-Hyi) Cα-O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the δ33 component that governs the behavior of δiso in these alpha carbons.
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carbonates thiocarbonates and the corresponding monoalkyl derivatives iii the 13c Chemical Shift Tensors in potassium carbonate bicarbonate and related monomethyl derivatives
Solid State Nuclear Magnetic Resonance, 2002Co-Authors: Dirk Stueber, Julio C. Facelli, Anita M. Orendt, Robert W Parry, David M GrantAbstract:The principal values of the 13C Chemical Shift Tensors in potassium carbonate (K2CO3), trithiocarbonate (K2CS3), bicarbonate (KHCO3), methylcarbonate (KO2COCH3), S-methyl-monothiocarbonate (KO2CSCH3), O-methyl-monothiocarbonate (KOSCOCH3), S-methyl-dithiocarbonate (KOSCSCH3), and O-methyl-dithiocarbonate (KS2COCH3), were measured in solid-state nuclear magnetic resonance experiments. Chemical Shift Tensor calculations on the corresponding isolated anions were used to assign the Chemical Shift Tensor orientations in the molecular frames of all anions. The correlation between experimental and calculated principal values improves significantly when the calculations are performed on isolated anions with proton-optimized X-ray geometries rather than on isolated anions with fully optimized geometries. Further considerable improvement in the correlation is achieved by utilizing the embedded ion method, which was recently developed to include electrostatic crystal potentials in Chemical Shift Tensor calculations on ionic compounds. Similarities and differences in the Chemical Shift Tensor orientations and principal values of the trigonal sp2 carbon atoms in the carbonate and thiocarbonate anions are compared with those known for condensed polyaromatic hydrocarbons.
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investigation of the structural conformation of biphenyl by solid state 13c nmr and quantum Chemical nmr Shift calculations
Journal of Physical Chemistry A, 2001Co-Authors: Dewey H Barich, David M Grant, Ronald J Pugmire, Robbie J IuliucciAbstract:The principal values of the 13C Chemical-Shift Tensor (CST) for biphenyl have been determined with the FIREMAT experiment. The internal dihedral angle between the benzene rings in biphenyl is estimated to fall between 10 and 20° on the basis of quantum mechanical calculations of the CST principal values. A composite model of motion in the system, with contributions both from internal jumping between enantiomeric structures and from overall molecular librations, yields the smallest variance between predicted and measured values for an internal twist angle of 15° between the rings and a mean libration angle of ±12° from the most favored molecular orientation. The composite model is clearly preferred to a motionless model (with >98% probability) and is also preferred over either of the isolated contributing dynamics, i.e., only libration or only internal jumping.
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A theoretical study of the acetate 13C Chemical Shift Tensor in cadmium acetate dihydrate
Chemical Physics Letters, 1999Co-Authors: Anita M. Orendt, Julio C. Facelli, David M GrantAbstract:Abstract Theoretical calculations of the 13 C Chemical shielding Tensor were completed on different fragments of the crystal structure of cadmium acetate dihydrate using the GIAO method. The calculations show the need for including intermolecular interactions in order to reproduce the experimental 13 C Chemical Shift Tensors of charged species. When a large enough fragment of the crystal is included in the calculation, the RMS difference between the experimental and the theoretical Chemical Shift Tensor is 7 ppm, in comparison to differences of 64–20 ppm for calculations on isolated acetate anions and on cadmium acetate with and without waters of hydration. This RMS difference of 7 ppm is comparable to that obtained by calculations on neutral organic molecules, completed using similar computational approaches but without the inclusion of any intermolecular interactions.
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solid state 13c Chemical Shift Tensors in terpenes part i spectroscopic methods and Chemical Shift structure correlations in caryophyllene oxide
Magnetic Resonance in Chemistry, 1998Co-Authors: James K Harper, Gary Mcgeorge, David M GrantAbstract:Principal values of the 13C Chemical Shift Tensor were obtained for the 15 carbons of solid caryophyllene oxide using an improved PHORMAT NMR analysis. The improvements include TIGER processing and improved proton decoupling. TIGER is an alternative to Fourier methods and shortens 2D data collection by incorporating information from a high-resolution isotropic 1D FID to allow accurate processing of even severely truncated 2D evolution FIDs. In caryophyllene oxide, data collection required less than 1 day, giving significant time savings over comparable 2D Fourier methods. Experimental principal values were assigned with high statistical confidence to specific carbons by comparing them with corresponding calculated values. Correctly assigned values were used to evaluate five different Tensor calculation methods. For caryophyllene oxide, the B3PW91 method gave the best correlation with experimental principal values with an RMS error of 2.3 ppm. Refinement of x-ray positions for hydrogens was shown to improve the calculated RMS error by a factor of >2. Calculated Tensors can be used to provide principal value orientations in the three methyl groups of caryophyllene oxide. One of the perpendicular component, δ⊥, is found to exhibit the largest Shift variation and dominates the methyl Shifts. Sterically unfavorable non-bonded interactions between proximate hydrogens are shown to correlate with this large upfield Shift in the δ⊥ component. © 1998 John Wiley & Sons, Ltd.
Anne S. Ulrich - One of the best experts on this subject based on the ideXlab platform.
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spectral assignments and anisotropy data of cellulose i α 13c nmr Chemical Shift data of cellulose iα determined by inadequate and rai techniques applied to uniformly 13c labeled bacterial celluloses of different gluconacetobacter xylinus strains
Magnetic Resonance in Chemistry, 2008Co-Authors: Stephanie Hesseertelt, Raiker Witter, Anne S. Ulrich, Tetsuo Kondo, Thomas HeinzeAbstract:Solid-state 13C-NMR spectroscopy was used to characterize native cellulose pellicles from two strains of Gluconacetobacter xylinus (ATCC 53582, ATCC 23769), which had been statically cultivated in Hestrin–Schramm (HS) medium containing fully 13C-labeled β-D-glucose-U-13C6 as the sole source of carbon. For both samples, the 13C-NMR Chemical Shifts were completely assigned for each 13C-labeled site of cellulose Iα with the aid of 2D refocused INADEQUATE NMR. To determine the principal Chemical Shift Tensor components, a pulse sequence based on the recoupling of anisotropy information (RAI) was applied at 10 kHz MAS. The detailed 13C Tensors of cellulose Iα from different bacterial celluloses are thus available now for the first time, and these results have been compared with previously published data of nonenriched material and with theoretical predictions. Copyright © 2008 John Wiley & Sons, Ltd.
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Spectral assignments and anisotropy data of cellulose I?α: 13C-NMR Chemical Shift data of cellulose Iα determined by INADEQUATE and RAI techniques applied to uniformly 13C-labeled bacterial celluloses of different Gluconacetobacter xylinus strains
Magnetic resonance in chemistry : MRC, 2008Co-Authors: Stephanie Hesse-ertelt, Raiker Witter, Anne S. Ulrich, Tetsuo Kondo, Thomas HeinzeAbstract:Solid-state (13)C-NMR spectroscopy was used to characterize native cellulose pellicles from two strains of Gluconacetobacter xylinus (ATCC 53582, ATCC 23769), which had been statically cultivated in Hestrin-Schramm (HS) medium containing fully (13)C-labeled beta-D-glucose-U-(13)C(6) as the sole source of carbon. For both samples, the (13)C-NMR Chemical Shifts were completely assigned for each (13)C-labeled site of cellulose I(alpha) with the aid of 2D refocused INADEQUATE NMR. To determine the principal Chemical Shift Tensor components, a pulse sequence based on the recoupling of anisotropy information (RAI) was applied at 10 kHz MAS. The detailed (13)C Tensors of cellulose I(alpha) from different bacterial celluloses are thus available now for the first time, and these results have been compared with previously published data of nonenriched material and with theoretical predictions.
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13c Chemical Shift constrained crystal structure refinement of cellulose iα and its verification by nmr anisotropy experiments
Macromolecules, 2006Co-Authors: Raiker Witter, Tetsuo Kondo, Ulrich Sternberg, Stephanie Hesse, Frankth Koch, Anne S. UlrichAbstract:The solid-state NMR assignments of the 13C resonances of bacterial cellulose Iα were reinvestigated by INADEQUATE experiments on uniformly 13C-enriched samples from Acetobacter xylinum. Additionally, we determined the principal Chemical Shift Tensor components of each 13C labeled site from a 2D iso-aniso RAI (recoupling of anisotropy information) spectrum acquired at magic angle spinning speed of 10 kHz. On the basis of these NMR data, the crystal structure of cellulose Iα was refined using the 13C Chemical Shifts for target functions. Starting off with coordinates derived from neutron scattering, our molecular dynamics simulations yielded four ensembles of 200 structures, two ensembles for hydrogen bond scheme A and B and two ensembles for different Chemical Shift assignments I and II, giving 800 structures in total. These were subsequently geometry-optimized with the given isotropic Chemical Shift constraints applying crystallographic boundary conditions, to identify a structure for every ensemble that ...
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nmr Chemical Shift powder pattern recoupling at high spinning speed and theoretical Tensor evaluation applied to silk fibroin
Journal of the American Chemical Society, 2006Co-Authors: Raiker Witter, Ulrich Sternberg, Anne S. UlrichAbstract:The NMR pulse sequence RAI (recoupling of anisotropy information) has been improved to obtain powder patterns at high MAS spinning speeds. The 2D iso-aniso experiment displays the static Chemical Shift spectra on the indirect dimension and the MAS spectra on the direct dimension; hence overlapping Chemical Shift Tensor patterns can be well resolved. This efficient technique is applicable to compounds containing 13C sp3 (Cα, Cβ) and sp2 (CO) sites with higher Chemical Shift (CS) anisotropy (CSA), and the reliability of the method was tested here on the 13C Chemical Shift Tensors of polycrystalline glycine, alanine, and serine. Subsequently, the same experiment was applied to the native silk protein fibroin from Bombyx mori, which consists mainly of these three amino acids. Molecular dynamics (MD) simulations of the silk II crystal structure of Takahashi et al. (Takahashi et al. Int. J. Biol. Macromol. 1999, 24, 127−138) were carried out to study the influence of motions on the Chemical Shift Tensors. The 1...