Orientational order of two fluoro- and isothiocyanate-substituted nematogens by combination of 13C NMR spectroscopy and DFT calculations.

Orientational order properties of two nematogens containing a fluoro- and isothiocyanate-substituted biphenyl moiety have been investigated by means of (13)C NMR spectroscopy. (13)C NMR spectra acquired on static samples under high-power (1)H-decoupling allowed both (13)C chemical shift anisotropies and (13)C-(19)F 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.

[1]  M. K. Das,et al.  Dielectric and visco-elastic properties of laterally fluorinated liquid crystal single compounds and their mixture , 2012 .

[2]  B. Mennucci,et al.  Integrated NMR and computational study of push-pull NLO probes: interplay of solvent and structural effects. , 2011, The journal of physical chemistry. A.

[3]  R. Dabrowski,et al.  Orientational order of fluorinated mesogens containing the 1,3,2-dioxaborinane ring: a multidisciplinary approach. , 2009, The journal of physical chemistry. B.

[4]  R. Dabrowski,et al.  Mesomorphic and dielectric properties of fluorosubstituted isothiocyanates with different bridging groups , 2009 .

[5]  R. Dabrowski,et al.  Dielectric properties of ten three-ring LC fluorosubstituted isothiocyanates with different mesogenic cores , 2009 .

[6]  R. Dabrowski,et al.  Orientational order of difluorinated liquid crystals: a comparative 13C-NMR, Optical, and dielectric study in nematic and smectic B phases. , 2008, The journal of physical chemistry. B.

[7]  D. Truhlar,et al.  The M06 suite of density functionals for main group thermochemistry, thermochemical kinetics, noncovalent interactions, excited states, and transition elements: two new functionals and systematic testing of four M06-class functionals and 12 other functionals , 2008 .

[8]  Michael Hird,et al.  Fluorinated liquid crystals--properties and applications. , 2007, Chemical Society reviews.

[9]  R. Dabrowski,et al.  Orientational order properties in fluorinated liquid crystals from an optical, dielectric, and 13C NMR combined approach , 2007 .

[10]  J. Tomasi,et al.  Quantum mechanical continuum solvation models. , 2005, Chemical reviews.

[11]  Stanisław Urban,et al.  Nematic order parameter as determined from dielectric relaxation data and other methods , 2003 .

[12]  B. Fung.  13C NMR studies of liquid crystals , 2002 .

[13]  D. L. Bryce,et al.  Spin -spin coupling tensors as determined by experiment and computational chemistry , 2002 .

[14]  J. Jokisaari,et al.  Indirect Fluorine Coupling Anisotropies in p-Difluorobenzene: Implications to Orientation and Structure Determination of Fluorinated Liquid Crystals , 1999 .

[15]  Jacopo Tomasi,et al.  Evaluation of Solvent Effects in Isotropic and Anisotropic Dielectrics and in Ionic Solutions with a Unified Integral Equation Method: Theoretical Bases, Computational Implementation, and Numerical Applications , 1997 .

[16]  Jacopo Tomasi,et al.  A new integral equation formalism for the polarizable continuum model: Theoretical background and applications to isotropic and anisotropic dielectrics , 1997 .

[17]  D. Sandström,et al.  Structure and Molecular Ordering of a Nematic Liquid Crystal Studied by Natural-Abundance Double-Quantum 13C NMR , 1996 .

[18]  T. Keith,et al.  A comparison of models for calculating nuclear magnetic resonance shielding tensors , 1996 .

[19]  M. Magnuson,et al.  Orientational ordering of liquid crystals containing a difluoro-substituted phenyl ring , 1995 .

[20]  M. Magnuson,et al.  Determination of order parameters from carbon–fluorine dipolar coupling , 1994 .

[21]  A. Becke.  Density-functional thermochemistry. III. The role of exact exchange , 1993 .

[22]  M. J. Bradshaw,et al.  The determination of the order parameters of nematic liquid crystals by mean field extrapolation , 1983 .

[23]  C. Tschierske.  Fluorinated liquid crystals: design of soft nanostructures and increased complexity of self-assembly by perfluorinated segments. , 2012, Topics in current chemistry.

[24]  B. Fung,et al.  An improved broadband decoupling sequence for liquid crystals and solids. , 2000, Journal of magnetic resonance.

[25]  A. Lesage,et al.  THE STRUCTURE, CONFORMATION AND ORIENTATIONAL ORDER OF FLUORINATED LIQUID CRYSTALS DETERMINED FROM CARBON-13 NMR SPECTROSCOPY , 1999 .

[26]  I. Haller.  Thermodynamic and static properties of liquid crystals , 1975 .