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Determination of C-13 Chemical Shift Anisotropy Tensors and Molecular Order of 4-Hexyloxybenzoic Acid

Lobo, NitinP and Prakash, M and Narasimhaswarny, T and Ramanathan, KV (2012) Determination of C-13 Chemical Shift Anisotropy Tensors and Molecular Order of 4-Hexyloxybenzoic Acid. In: JOURNAL OF PHYSICAL CHEMISTRY A, 116 (28). pp. 7508-7515.

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Official URL: http://dx.doi.org/10.1021/jp302291u

Abstract

4-Alkoxy benzoic acids belong to an important class of thermotropic liquid crystals that are structurally simple and often used as starting materials for many novel mesogens. 4-Hexyloxybenzoic acid (HBA) is a homologue of the same series and exhibits an enantiotropic nematic phase. As this molecule could serve as an ideal model compound, high resolution C-13 NMR studies of HEA in solution, solid, and liquid crystalline phases have been undertaken. In the solid state, two-dimensional separation of undistorted powder patterns by effortless recoupling (2D SUPER) experiments have been carried out to estimate the magnitude of the components of the chemical shift anisotropy (GSA) tensor of all the aromatic carbons. These values have been used subsequently for calculating the orientational order parameters in the liquid crystalline phase. The GSA values computed by density functional theory (DFT) calculations showed good agreement with the 2D SUPER values. Additionally, C-13-H-1 dipolar couplings in the nematic phase have been determined by separated local field (SLF) spectroscopy at various temperatures and were used for computing the order parameters, which compared well with those calculated by using the chemical shifts. It is anticipated that the CSA values determined for MBA would be useful for the assignment of carbon chemical shifts and for the study of order and dynamics of structurally similar novel mesogens in their nematic phases.

Item Type: Journal Article
Additional Information: Copy right for this article belongs to American Chemical Society
Department/Centre: Division of Chemical Sciences > NMR Research Centre (Formerly SIF)
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 21 Aug 2012 03:54
Last Modified: 21 Aug 2012 03:54
URI: http://eprints.iisc.ernet.in/id/eprint/44962

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