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Orientational Order of Two Fluoro- and Isothiocyanate-Substituted Nematogens by Combination of 13C NMR Spectroscopy and DFT Calculations
journal contribution
posted on 2014-03-27, 00:00 authored by Lucia Calucci, Elisa Carignani, Marco Geppi, Sara Macchi, Benedetta Mennucci, Stanislaw UrbanOrientational
order properties of two nematogens containing a fluoro-
and isothiocyanate-substituted biphenyl moiety have been investigated
by means of 13C NMR spectroscopy. 13C NMR spectra
acquired on static samples under high-power 1H-decoupling
allowed both 13C chemical shift anisotropies and 13C–19F couplings to be measured. These data were
used to determine the local principal order parameter and biaxiality
for the different rigid fragments of the molecules. To this aim, advanced
DFT methods for the calculation of geometrical parameters and chemical
shift tensors were used. The orientational order parameters obtained
by NMR have been critically compared with those obtained by dielectric
spectroscopy. Trends of order parameters with temperature have been
analyzed in terms of both mean field theory and the empirical Haller
equation.
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dielectric spectroscopy13 C chemical shift anisotropiesisothiocyanate-substituted biphenyl moiety13 C NMR spectra13 C NMR Spectroscopy1 H-decouplingDFT methodsorder parametersDFT Calculations Orientational order propertiesfield theoryOrientational OrderHaller equationorientational order parametersorder parameterIsothiocyanate-Substituted Nematogens13 C NMR spectroscopychemical shift tensors
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