Dipole Moments in Organic Chemistry

Минкин, Владимир И.; Osipov, O. A.; Жданов, Ю А

doi:10.1007/978-1-4684-1770-8

Cited by 337 publications

(175 citation statements)

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“…That is not the case with the other studied liquid crystals. For example, the components of the electric dipole moment for 8OCFPB in the ground state are equal to 6.45 D (µ l ) and 1.3 D (µ t ), in accordance with the vector addition model [21][22][23]. As a result, the angle between the vector of the dipole moment and the long axis of this molecule is about 12 • .…”

Section: Dielectric Relaxationsupporting

confidence: 52%

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

et al. 2011

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Dielectric relaxation study of nematogenic 4-n-alkyl-4 -cyanobiphenyls (nCB, n = 5, 6), 4-(trans-4 -n-alkylcyclohexyl)isothiocyanatobenzenes (nCHBT, n = 6, 8), 4-cyanophenyl-4 -n-alkylbenzoates (nCPB, n = 6, 8), 4-cyano-3-fluorophenyl-4 -n-octyloxybenzoate (8OCFPB), and 4-cyanophenyl-4 -n-octyloxy-3 -fluorobenzoate (8OCPFB) was performed in the frequency range from 50 kHz to 100 MHz in the nematic and isotropic phases. The static permittivity and the relaxation process related to the rotation of molecules around their short axis was analyzed. For some of these liquid crystals anomalous temperature dependence of static permittivity in the pretransitional region of the isotropic phase was observed. Based on the Meier-Saupe-Martin model of molecular diffusion in nematics, the orientational order parameter P 2 was determined from dielectric relaxation times and retardation factor. The values of P 2 calculated from the dielectric relaxation data were compared with the results obtained from measurements of polarized electronic absorption. Correlations between the magnitude of the dielectric pretransitional effect and the orientational order in the nematic phase were discussed.

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Section: Dielectric Relaxationsupporting

confidence: 52%

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

et al. 2011

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“…In particular, aromatic ester-based mesogens could achieve a stable nematic phase through strong intermolecular dipoledipole interactions between carbonyl groups of adjacent molecules, an effect that increases with the strength of the molecular interaction (32,33). In our system, we expect strong dipole-dipole interactions between carbonyl groups (dipole moment μ = 2.4D) (34) that are evenly distributed along the molecule and a more polar nitro group (μ = 4.01D) (34) in the middle of the molecule. Because each nitro group bonds randomly to one of the four sites from the adjacent LC molecule, crystallization is suppressed, as seen in analogous systems (30,33,35), leading to a highly stable nematic phase (SI Appendix, Fig.…”

Section: Resultsmentioning

confidence: 91%

Direct mapping of local director field of nematic liquid crystals at the nanoscale

Xia

Serra

Kamien

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Liquid crystals (LCs), owing to their anisotropy in molecular ordering, are of wide interest in both the display industry and soft matter as a route to more sophisticated optical objects, to direct phase separation, and to facilitate colloidal assemblies. However, it remains challenging to directly probe the molecular-scale organization of nonglassy nematic LC molecules without altering the LC directors. We design and synthesize a new type of nematic liquid crystal monomer (LCM) system with strong dipole-dipole interactions, resulting in a stable nematic phase and strong homeotropic anchoring on silica surfaces. Upon photopolymerization, the director field can be faithfully "locked," allowing for direct visualization of the LC director field and defect structures by scanning electron microscopy (SEM) in real space with 100-nm resolution. Using this technique, we study the nematic textures in more complex LC/colloidal systems and calculate the extrapolation length of the LCM.nematic liquid crystal polymers | dipole-dipole interactions | topological defects | photo-cross-linking | nanoscale imaging

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“…This is the route which we followed in the experiments reported in this paper: the ground-state dipole moment was additionally calculated from the results of measurements of static electric permittivity, following the procedure described in Ref. [3].…”

Section: The Solvatochromic Effectmentioning

confidence: 99%

“…Consequently, a complete description of the electronic properties of the molecules requires the knowledge of the ground-and excited-state dipole moments, as well as of the polarizabilities (linear and of the higher orders). While the parameters characterizing the ground state of the molecule are in many cases readily available (e.g., the ground-state dipole moment can be easily determined from standard dielectric measurements [3]), those of excited states have been scarcely known. Among several existing methods allowing one to obtain such information, the simplest (although not the mo8t reliable) one is that making use of the solvatochromic effect (e.g.…”

Section: Introductionmentioning

confidence: 99%

Solvatochromic Effect in a Benzimidazole-Based Betaine: Determination of the Dipole Moments and Second-Order Hyperpolarizability

et al. 1995

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Results of measurements of the solvent-dependent shift of the low-energy absorption band solvatochromic effect in a benzimidazole-based betaine are reported in the paper. Measurements of absorption spectra in several solvents of different polarities were performed. The solvatochromic shift of the low-lying absorption band was found to exceed 3000 cm -1 ; the results obtained were then employed to calculate the ground-and excited-state dipole moment of the molecule. The spectroscopic measurements were supplemented by measurements of the ground-state dipole moment. A remarkable change in the charge distribution was found to occur upon the electronic excitation: both the experimental results and the calculations indicate that the ground-state dipole moment is close to 13 D, whereas in the excited state it amounts to ca. 3 D. The second-order hyperpolarizability of the molecule was calculated from the measurements; its off-resonance value amounts to ca. 20 x 10 -40 m4 /V (4.8 x 10 -30 esu), depending on the solvent used.

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Dipole Moments in Organic Chemistry

Cited by 337 publications

References 0 publications

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

Prenematic Self-Assembling of Mesogenic Molecules in Isotropic Liquid and Orientational Order in Nematic Phase

Direct mapping of local director field of nematic liquid crystals at the nanoscale

Solvatochromic Effect in a Benzimidazole-Based Betaine: Determination of the Dipole Moments and Second-Order Hyperpolarizability

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