Star-shaped supramolecular ionic liquid crystals based on pyridinium salts

Abstract

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.

Recent synthetic advances in pyridine-based thermotropic mesogens

“…Wang et al 44 synthesized two series of ionic liquid crystals, i.e. N-phenylpyridinium derivatives (98)(99)(100)(101)(102)(103)(104). By studying previous literature (Michels et al, 45 Zeghbib et al, 46a Kuwabara et al, 47 Kuo et al 48 ), they synthesized precursors such as N-phenyl pyridinium chloride 96 and N-(4-alkoxyphenyl)pyridinium chloride 97a-d. To substitute the chloride into different anions, they used methanol as a phase transfer medium.…”

“…Recently, Wang et al 98 synthesized a series of star-shaped mesogens comprising a [1,1 0 -biphenyl]-4,4 0 -diyl diisonicotinate moiety carrying different counter ions, such as Br À , dodecylbenzenesulphonate anion, (+)-10-camphorsulfonate anion, H 2 PO 4 À and BF 4 À . Further, these compounds exhibited nematic phase, and it was noted that the mesophase temperature range increased with increasing alkyl chain length and that the clearing point decreased with increasing anion size.…”

Chair- and V-Shaped of H-bonded Supramolecular Complexes of Azophenyl Nicotinate Derivatives; Mesomorphic and DFT Molecular Geometry Aspects

“…Those changes in the characteristics of the LCs may impact the mesomorphic behaviour as well as the essential properties for technical uses. Recently, molecular interactions due to hydrogen bonding (H-bonding) formation have received more attention in the field of liquid crystal [26][27][28][29][30]. Supramolecular H-bonding LCs (SMHBLCs) designed through noncovalent interactions of suitable H-bond donors and acceptors are concerns of our area of interest [31][32][33][34][35][36][37].…”

Synthesis and liquid crystalline properties of new triazine-basedπ-conjugated macromolecules with chiral side groups

“…extraction processes, as an electrolyte for fuel cells and dye-sensitive solar cells [18]. A large number of literature reports are available on the liquid crystalline properties of the charged materials containing anions and cations [15,19,20].…”