Determination of orientational order parameters in liquid crystals from temperature-dependent 13C NMR experiments

Hagemeyer, Alfred; Tarroni, Riccardo; Zannoni, Claudio

doi:10.1039/ft9949003433

Cited by 12 publications

(23 citation statements)

References 29 publications

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“…This assumption was implicitly taken in all our previous works, [26][27][28] and some recent studies 20,58 have confirmed its applicability. This is in general quite a strong assumption, but in the present case it can be safely invoked since the rotational isomerism around bonds does not radically change the elongated rodlike shape of the molecules.…”

Section: ϫDd ͑4͒supporting

confidence: 59%

“…26, where we also discuss the precautions taken to avoid rf heating. 26, where we also discuss the precautions taken to avoid rf heating.…”

Section: A Experimentsmentioning

confidence: 99%

“…In a previous study, 20 we have tested the use of computed chemical shieldings as input data for the determination of the orientational behavior of some rigid organic molecule dissolved in a thermotropic liquid crystal, whose order parameters are known from 2 D-NMR results. [26][27][28] Moreover, an analysis of the dependence on the magnetic properties from the molecular structure has been performed. We focus our attention to an homologous series of ␣, -diphenylpolyenes dissolved in the thermotropic liquid crystal ZLI-1167.…”

Section: Introductionmentioning

confidence: 99%

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Order parameters of α,ω-diphenylpolyenes in a nematic liquid crystal from an integrated computational and C13 NMR spectroscopic approach

Benzi

Barone

Tarroni

et al. 2006

The Journal of Chemical Physics

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The orientational order parameters and conformational behavior of five relatively large rodlike molecules, biphenyl, trans-stilbene, 1,3-diphenyl-butadiene, 1,3,5-diphenyl-hexatriene, and 1,3,5,7-diphenyl-octatetraene, dissolved in the thermotropic liquid crystal ZLI-1167, have been studied using an integrated approach combining (13)C NMR measurements and quantum mechanical computations of carbon chemical shift tensors. Besides biphenyl, the phenyl moiety of all structures has been found to have a high rotational mobility in the temperature range of the present experiments. The rank-two order parameter in the nematic phase is found to increase steadily from the shortest to the longest term of the series at any temperature within the nematic range. The molecular biaxiality order parameter is found to be small and essentially constant with temperature, giving further support to the common assumption of effective uniaxiality for these probes.

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Section: ϫDd ͑4͒supporting

confidence: 59%

“…26, where we also discuss the precautions taken to avoid rf heating. 26, where we also discuss the precautions taken to avoid rf heating.…”

Section: A Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Order parameters of α,ω-diphenylpolyenes in a nematic liquid crystal from an integrated computational and C13 NMR spectroscopic approach

Benzi

Barone

Tarroni

et al. 2006

The Journal of Chemical Physics

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“…11,12 An alternative method has been developed to determine ordering matrices from natural abundance 13 C-NMR measurements. In particular, from temperature dependent nuclear magnetic resonance ͑NMR͒ measurements, the solute Saupe matrix can be determined provided that the molecule contains a sufficient number of independent sites.…”

Section: Introductionmentioning

confidence: 99%

“…These are simply related to the elements of the Saupe matrix. To this purpose, the components T 2n MOL ͑j͒ of the tensor have to be known; what is generally done 11,13 is to use experimental data obtained in the crystalline phase 18 of the compound under investigation or of a similar compound, and to assume that T is a sufficiently local and environment insensitive property. Such an assumption, together with the temperature independence of magnetic tensors, is usually exploited in analyzing experimental data, i.e., the measured shifts T aniso ͑j͒ − T iso ͑j͒, to extract orientational order parameters.…”

Section: Introductionmentioning

confidence: 99%

Quantum-mechanical studies of NMR properties of solutes in liquid crystals: A new strategy to determine orientational order parameters

Pavanello

Mennucci

Ferrarini

2005

The Journal of Chemical Physics

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We present a quantum-mechanical method to calculate the tensorial NMR magnetic properties of molecules in liquid crystals. The method exploits a density functional description for the solute and the integral equation formalism version of the polarizable continuum model to include the effects of the dielectric anisotropy of the solvent on the wave function of the solute molecule and on its response to an applied magnetic field. Taking into account the dependence of the calculated molecular tensors on the solute orientation, we have derived the necessary expressions to relate such tensors to the spectral observables. These equations are then used to determine order parameters by calculating the nuclear shieldings of various solutes in the nematic ZLI-1167. Comparisons with experimental data of the same parameters are finally presented.

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Ab initio model to predict NMR shielding tensors for solutes in liquid crystals

Mennucci

Cammi

2003

Int J of Quantum Chemistry

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We present a model for the ab initio calculation of the nuclear magnetic shielding tensors for molecules in liquid crystalline solvents. The electrostatic interactions between the solute and the anisotropic solvent are described within the integral equation formalism (IEF) framework and the shielding tensors are calculated at the density functional theory linked to the gauge invariant atomic orbital (GIAO) approach. The IEF-GIAO approach is tested on the calculation of the shielding tensors for the different nuclei of CH 3 CN and C 6 H 5 NO 2 in positive and negative anisotropic solvents.

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Determination of orientational order parameters in liquid crystals from temperature-dependent 13C NMR experiments

Cited by 12 publications

References 29 publications

Order parameters of α,ω-diphenylpolyenes in a nematic liquid crystal from an integrated computational and C13 NMR spectroscopic approach

Order parameters of α,ω-diphenylpolyenes in a nematic liquid crystal from an integrated computational and C13 NMR spectroscopic approach

Quantum-mechanical studies of NMR properties of solutes in liquid crystals: A new strategy to determine orientational order parameters

Ab initio model to predict NMR shielding tensors for solutes in liquid crystals

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