Roof‐Shaped Pyrazaboles as a Structural Motif for Bent‐Core Liquid Crystals

Cavero, Emma; Lydon, Donocadh P.; Uriel, Santiago; Fuente, M. R. de la; Serrano, José Luís; Giménez, Raquel

doi:10.1002/anie.200700820

Cited by 19 publications

(6 citation statements)

References 23 publications

(20 reference statements)

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“…[27] The four symmetrically located diffuse spots in the small-angle X-ray scattering (SAXS) region hint at the presence of short-range SmC-like ordering (cybotactic groups or clusters) [28] in the N, a type of structure reported in the literature not only near a N-SmC transition but also over wide temperature ranges, even in the absence of an underlying SmC phase, [29] and notably also for other BM. [26,30,31] At T ¼ 150 8C the center of SAXS peaks corresponds to a scattering vector q with modulus q 0 ¼ 2.05 nm À1 and tilt b ¼ 498 from the B direction. The layer spacing in the cybotactic groups, d ¼ 2p/q 0 ¼ 30.7 Å , is much smaller than www.afm-journal.de Figure 1.…”

Section: Resultsmentioning

confidence: 99%

Ferroelectric Response and Induced Biaxiality in the Nematic Phase of Bent‐Core Mesogens

Francescangeli

Stanić

Torgova

et al. 2009

Adv Funct Materials

192

170

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The still undiscovered fluid ferroelectric nematic phase is expected to exhibit a much faster and easier response to an external electric field compared to conventional ferroelectric smectic liquid crystals; therefore, the discovery of such a phase could open new avenues in electro‐optic device technology. Here, experimental evidence of a ferroelectric response to a switching electric field in a low molar mass nematic liquid crystal is reported and connected with field‐induced biaxiality. The fluid is made of bent‐core polar molecules and is nematic over a range of 120 °C. Combining repolarization current measurements, electro‐optical characterizations, X‐ray diffraction and computer simulations, ferroelectric switching is demonstrated and it is concluded that the response is due to field‐induced reorganization of polar cybotactic groups within the nematic phase. This work represents significant progress toward the realization of ferroelectric fluids that can be aligned at command with a simple electric field.

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Section: Resultsmentioning

confidence: 99%

Ferroelectric Response and Induced Biaxiality in the Nematic Phase of Bent‐Core Mesogens

Francescangeli

Stanić

Torgova

et al. 2009

Adv Funct Materials

192

170

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“…For example, tricoordinated boron compounds are Lewis acidic, isoelectronic with carbeniumions, possess π‐electron‐acceptor as well as inductive σ‐electron‐donor capacity, undergo formation of tetracoordinate borates, and conjugate adjacent π‐systems, whereas compounds containing B−N bonds are isoelectronic with the corresponding C−C analogues and display strong luminescence . With regard to thermotropic liquid crystals, most work has been devoted to borondifluoride β‐diketonates (or β‐enaminoketonates), borondipyrromethene (BODIPY) derivatives ( 1 ), and boron clusters ( 2 ) (Figure ). In diketonate and BODIPY derivatives such as 1 or subphthalocyanines, the boron atom is surrounded by a flat mesogenic π‐system, which not only contributes to the liquid crystalline self‐assembly, but also adds favorable absorption and emission characteristics.…”

Section: Introductionmentioning

confidence: 99%

Thermotropic MIDA Boronates as a Case Study for the Role of Dipolar Interactions in Liquid Crystalline Self‐Assembly

Wöhrle

Gündemir

Frey

et al. 2017

Chemistry A European J

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A series of MIDA (N-methylimino diacetic acid) boronates carrying 4-alkoxy, 3,4-bisalkoxy, or 3,4,5-trisalkoxyphenyl substituents were synthesized and their mesomorphic properties characterized by differential scanning calorimetry (DSC), polarizing optical microscopy (POM), and X-ray diffraction (XRD) techniques such as small- and wide-angle X-ray scattering (SAXS and WAXS, respectively). Most derivatives were liquid crystalline. In the case of mono- and bisalkoxy-substituted derivatives, C chains already induced smectic A (SmA) mesophases despite the bulky MIDA head group. With increasing chain length, columnar hexagonal (Col ) phases replaced SmA phases in the disubstituted series. Quantum chemical calculations on a series of MIDA boronates show that the B-N bond is a dative bond with a positive charge on the boron atom and negative charges on the nitrogen and oxygen atoms. In addition, no π-interaction between the aryl moiety and B-N bond was found, thus the mesogenic unit is electronically decoupled from the MIDA head group. These theoretical findings were supported by IR and Raman spectra as well as by asingle crystal structure analysis of 4-ethoxyphenyl MIDA boronate. Calculations of the electrostatic potential of the MIDA boronate reveal a special polarity pattern that can support the formation of a two-dimensional network and is likely to explain the liquid crystalline self-assembly. The absence of any electronic cross-talk between the MIDA head group and B-aryl or B-alkyl substituents allows the efficient tailoring of the mesophase type through variation of the substituents.

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“…The general esterification procedure was followed with 5 and 1,1,2,2-H-perfluorodecanol to give Est2.8 F as a white solid (169 mg, 65%). 5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-Heptadecafluorododecyl 4-(6-methyl-4,8-dioxo-1,3,6,2-dioxazaborocan-2-yl)benzoate (Est4.8 F )…”

Section: Organicmentioning

confidence: 99%

“…Boron-containing liquid crystals are an emerging class of soft matter materials. Particular emphasis has been put on borondipyrromethane (BODIPY) derivatives, [1][2][3][4][5][6][7][8][9][10][11][12] borondifluoride β-diketonates and β-enaminoketonates, [13][14][15][16][17][18][19] discotic borolanes, 20 and boroxines. 21,22 Boron clusters containing carboranes, closo-boranes, and closo-carbaborates give rise to polar liquid crystals relevant for molecular electronic and nonlinear optical applications.…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystalline Benzoic Acid Ester MIDA Boronates: Synthesis and Mesomorphic Properties

2020

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Two series of N-methyliminodiacetic acid (MIDA) boronates were prepared and their mesomorphic properties were investigated. MIDA-substituted benzoic acid esters were synthesized via the Mitsunobu reaction. The second series of MIDA benzyl ether derivatives was prepared via Williamson etherification and subsequent borylation. Both series exhibit smectic A (SmA) phases. In the case of MIDA boronate esters, a substitution with perfluorinated side chains led to increased transition temperatures and broadening of the SmA phases. The phase geometries of the mesophases were determined by X-ray diffraction. Quantum-chemical calculations provided further insight into the packing model.

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Roof‐Shaped Pyrazaboles as a Structural Motif for Bent‐Core Liquid Crystals

Cited by 19 publications

References 23 publications

Ferroelectric Response and Induced Biaxiality in the Nematic Phase of Bent‐Core Mesogens

Ferroelectric Response and Induced Biaxiality in the Nematic Phase of Bent‐Core Mesogens

Thermotropic MIDA Boronates as a Case Study for the Role of Dipolar Interactions in Liquid Crystalline Self‐Assembly

Liquid Crystalline Benzoic Acid Ester MIDA Boronates: Synthesis and Mesomorphic Properties

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