Ionic liquid crystals with 1,2,3-triazole + tolane core and a pendant imidazolium unit: mesophases from one- to three-dimensional molecular organisation by the variation of alkoxy chains number and spacer length

Ovalle, Saul; Westphal, Eduard; Gallardo, Hugo

doi:10.1080/02678292.2018.1441461

Cited by 11 publications

(2 citation statements)

References 35 publications

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“…Further support for the assigned mesophase came from the temperature-dependent layer distances, d 001 , calculated from the (001) reflection. Their increase with rising temperature is common for smectic C phases (Figure b). − …”

Section: Resultsmentioning

confidence: 99%

Novel Luminescent Diazafluorenone Liquid Crystals

Bader

Baro

Ehni

et al. 2019

Crystal Growth & Design

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In this work, the synthesis, X-ray crystal structure analysis, studies on mesomorphism and luminescence spectroscopy of 2,7-diphenyl-4,5-diazafluorenones carrying 2, 4 or 6 peripheral alkoxy side chains of different lengths in the mesogenic unit are reported. The latter was attached to starting 2,7-dibromo-4,5-diazafluoren-9-one via Suzuki cross coupling of the respective 2-(alkoxyphenyl)-tetramethyl-1,2,3-borolane. The liquid crystalline properties were found to depend on both the number of side chains and their lengths. Derivatives with two short alkoxy chains (C6-C8) in the periphery formed nematic (N) and smectic C (SmC) mesophases while for the higher homologues only SmC mesophases were observed. Compounds carrying six alkoxy side chains with a minimum length of C8 assembled into columnar hexagonal phases. Homologues with C14 and C16 chain length displayed additionally two columnar rectangular mesophases. Four peripheral alkoxy chains, however, led to the loss of mesomorphism. Crystal structure data of a series of rod-shaped diazafluorenones helped to rationalize their liquid crystalline self-assembly and to understand geometry and thermal stability. Temperature-dependent luminescence spectra of diazafluorenone with two C12 chains revealed aggregation-induced emission (AIE) depending on the supramolecular order of the bulk phase. These studies suggested that AIE requires a lower degree of aggregation as compared to mesophase formation.

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Section: Resultsmentioning

confidence: 99%

Novel Luminescent Diazafluorenone Liquid Crystals

Bader

Baro

Ehni

et al. 2019

Crystal Growth & Design

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“…To explore and take advantage of their properties, we implant ILCs into the star-shaped molecular structure. Aware that a minimal modification in the molecular structure can have a great impact on the mesomorphic and physical properties of ILCs [17,18].…”

Section: Introductionmentioning

confidence: 99%

Star-shaped supramolecular ionic liquid crystals based on pyridinium salts

et al. 2018

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Series of novel star-shaped liquid crystals containing [1,1ʹ-biphenyl]-4,4ʹ-diyl diisonicotinate mesogens with various counterions (Br − , B-SO 3 − ,C-SO 3 − ,H 2 PO 4 − , BF 4 − ) have been synthesized and characterized, which display a nematic phase. The molecular structures of the liquid crystals, thereof consisting of rod-like mesogens linked together by different long alkyl spacers to a small disc-like core of central benzene-1,3,5-triyl triisonicotinate, have been fully characterized by 1 H NMR. Their thermal and supramolecular organization behaviours have been studied by combining polarized optical microscopy, differential scanning calorimetry and small-angle X-ray scattering. These investigations showed that the mesophase temperature range increased with increasing alkyl chain length and the clearing point decreased with increase of anion size. These star-shaped liquid crystals have a long and ordered molecular structure, the electron delocalization of the π-π stacking conjugation effect and the electrostatic attraction of ionic make them have good ferroelectric properties and ionic conductivity properties. The interest in preparing ionic liquid crystal with a nematic phase lies in the technological applications as it is well known that the nematic phase has the highest fluidity of all liquid crystalline phases and hence the possibility to align it by applying an external electric/magnetic field, commonly used in electro-optical devices.

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