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| Max-Planck Forschungsberichte (laufend) |
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Forschungsbericht 200511-106
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Aus den Highlights 11/2005:
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Determining the geometry of hydrogen bonds in solids with picometer accuracy by quantum chemical calculations and NMR spectroscopy
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The structure of multiply hydrogen-bonded systems is determined with picometer accuracy by a combined solid-state NMR and quantum-chemical approach. On the experimental side, advanced H-1-N-15 dipolar recoupling NMR techniques are capable of providing proton-nitrogen distances of up to about 250 pm with on accuracy level of 1 pm for short distances (i.e., around 100 pm) and +/- 5 pm for longer ones (i.e., 180 to 250 pm). The experiments were performed under fast magic-angle spinning, which ensures sufficient dipolar decoupling and spectral resolution of the H-1 resonance lines. On the quantum-chemical side, the structures of the hydrogen-bonded systems were computationally optimised, yielding complete sets of nitrogen-proton and proton-proton distances, which ore essential for correctly interpreting the experimental NMR data. In this way, nitrogen-proton distances were determined with picometer accuracy, so that vibrational overaging effects on dipole-dipole couplings need to be considered. The obtained structures were finally confirmed by the complete agreement of computed and experimental H-1 and N-15 chemical shifts. This demonstrates that solid-state NMR and quantum-chemical methods ideally complement each other and, in a combined manner, represent a powerful approach for reliable, high-precision structure determination whenever scattering techniques are inapplicable.
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Autoren
Schulz-Dobrick M. Metzroth T. Spiess HW. Gauss J. Schnell I.
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Titel
Determining the geometry of hydrogen bonds in solids with picometer accuracy by quantum chemical calculations and NMR spectroscopy
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Quelle
Chemphyschem. 6(2):315-327, 2005 Feb.
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ISSN
1439-4235
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KeyWords Plus
Angle-spinning nmr, Nuclear-magnetic-resonance, Echo double-resonance, Heteronuclear dipolar interactions, Gaussian-basis sets, Rotating solids, Direct scf, Ab-initio, Atoms li, Fast-mas.
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Forschungsgebiet
Chemie
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Art der Ver�fentlichung
Article
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Institution
Schnell I Max Planck Inst Polymer Res Postfach 3148 D-55021 Mainz Germany Max Planck Inst Polymer Res D-55021 Mainz Germany Univ Mainz, Inst Phys Chem D-6500 Mainz Germany
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ISI Accession Number
899QK-0018
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