A Non-Traceless Molecular Pseudotensor for a Description of the HTP

Kuball, H.‐G.; Türk, Oliver; Kiesewalter, I.; Dorr, Elmar

doi:10.1080/10587250008023177

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…For example, the molecular shape is expected to have a strong contribution to the helical twisting power for molecules that possess at least two rigid planar fragments in a twisted configuration. As an example one can refer to chiral biaryls that are widely used as chiral dopants with high helical twisting power [27][28][29]. Moreover, steric interaction between such dopants and non-chiral molecules of the nematic solvent may result in a chirality transfer into the solvent [27].…”

Section: Chiral Dispersion Intermolecular Interactionsmentioning

confidence: 98%

“…In thermotropic nematic liquid crystals chirality of the molecular shape is important in some particular cases. For example, some chiral dopant molecules possess two or more rigid planar fragments in a chiral configuration [16,27,29]. In this case chiral molecular shape is very important and may even determine the chirality transfer into a nonchiral solvent due to short-range steric correlations [16].…”

Section: Introductionmentioning

confidence: 99%

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Helical twisting power and circular dichroism in nematic liquid crystals doped with chiral molecules

Osipov

Kuball

2001

The European Physical Journal E

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Explicit expressions for the helical twisting power of a chiral dopant in the nematic phase have been obtained in the mean field approximation taking into account chiral dispersion intermolecular interactions. The results of the theory enable one to explain a correlation between the signs of helical twisting power and circular dichroism of selected electronic transitions which have recently been established experimentally for some mono- and bis-aminoantroquinones. Helical twisting power is proportional to the pseudoscalar parameter that specifies the chirality of the dopant molecule in terms of its dipole and quadrupole matrix elements. This expression is simplified for a special class of molecules in which chirality is induced by a perturbing achiral group into an achiral skeleton. In this case both helical twisting power and circular dichroism are approximately proportional to some simple pseudoscalar functions that specify the location of the achiral perturbing group with respect to the symmetry planes of the unperturbed achiral skeleton. Simple sector rules have been proposed to determine the sign change of the helical twisting power associated with the change of location of the perturbing group

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Section: Chiral Dispersion Intermolecular Interactionsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Helical twisting power and circular dichroism in nematic liquid crystals doped with chiral molecules

Osipov

Kuball

2001

The European Physical Journal E

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“…MM calculations indicated that, in the nonbridged binaphthyl derivative ( R )- 2 , the stability of the cisoid and transoid conformations is almost equal. In the bridged binaphthyl derivative ( R )- 3 , the cisoid conformation is the stable one . Such a difference between the nonbridged and bridged binaphthyl derivatives may cause opposite screw directions of the N*-LCs, though they have the same configuration.…”

Section: Control Of the Helical Sensementioning

confidence: 99%

Helical Polyacetylene: Asymmetric Polymerization in a Chiral Liquid-Crystal Field

2009

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with expertise in functional conjugated polymers. His research interests have involved electrically conducting polymers and liquidcrystalline, luminescent, and photoresponsive conjugated polymers, with works focused on the synthesis of helical polyacetylene in the chiral nematic liquid-crystal field. He has also been engaged in development of liquid-crystalline aromatic conjugated polymers with linearly and circularly polarized optoelectronic properties. He graduated from the

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“…For example, the R -binaphthyl derivative of the cisoid conformation (0° < θ < 90°) and that of transoid conformation (90° < θ < 180°) have ( M )- and ( P )-helicity, respectively, as described in Figure . The binaphthyl derivatives of ( M )- and ( P )-helicity induce N*-LCs with left-handed (counterclockwise) and right-handed (clockwise) screw senses (helical senses), respectively, despite having the same ( R ) configuration, when they are added as chiral dopants into N-LCs . For example, a nonbridged structure of the binaphthyl derivative exhibits a transoid conformation, and a bridged structure exhibits a cisoid conformation, in which the two oxygen atoms at the 2,2′-positions of the binaphthyl rings are linked with an alkyl spacer.…”

Section: Introductionmentioning

confidence: 99%

“…Dynamic photoswitching of the chiral structure and the chiroptical properties in a chiral nematic LC (N*-LC) by means of external light is useful not only for the development of molecular devices and optical data storage systems − but also for the construction of an asymmetric reaction field that enables the synthesis of helical polymers. − The chiral dopants employed here are either chiral-center-containing compounds or axially chiral compounds. Axially chiral binaphthyl derivatives are feasible for controlling the helical sense and strength of the N*-LC, especially when their molecular structures have been chemically modified, such as by the introduction of long alkyl groups or mesogenic substituents onto the naphthyl rings …”

Section: Introductionmentioning

confidence: 99%

Dynamic Photoswitching of Helical Inversion in Liquid Crystals Containing Photoresponsive Axially Chiral Dopants

et al. 2012

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Chirality switching is intriguing for the dynamic control of the electronic and optical properties in nanoscale materials. The ability to photochemically switch the chirality in liquid crystals (LCs) is especially attractive given their potential applications in electro-optic displays, optical data storage, and the asymmetric synthesis of organic molecules and polymers. Here, we present a dynamic photoswitching of the helical inversion in chiral nematic LCs (N*-LCs) that contain photoresponsive axially chiral dopants. Novel photoresponsive chiral dithienylethene derivatives bearing two axially chiral binaphthyl moieties are synthesized. The dihedral angle of the binaphthyl rings changes via the photoisomerization between the open and closed forms of the dithienylethene moiety. The N*-LCs induced by the dithienylethene derivatives that are used as chiral dopants exhibit reversible photoswitching behaviors, including a helical inversion in the N*-LC and a phase transition between the N*-LC and the nematic LC. The present compounds are the first chiral dopants that induce a helical inversion in N*-LC via the photoisomerization between open and closed forms of the dithienylethene moiety.

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A Non-Traceless Molecular Pseudotensor for a Description of the HTP

Cited by 8 publications

References 8 publications

Helical twisting power and circular dichroism in nematic liquid crystals doped with chiral molecules

Helical twisting power and circular dichroism in nematic liquid crystals doped with chiral molecules

Helical Polyacetylene: Asymmetric Polymerization in a Chiral Liquid-Crystal Field

Dynamic Photoswitching of Helical Inversion in Liquid Crystals Containing Photoresponsive Axially Chiral Dopants

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