New pyrimidine-based photo-switchable bent-core liquid crystals

Abstract

The first examples of liquid crystalline pyrimidine-based photo-switchable bent-core monomers incorporating azobenzene as side arms linked with terminal double bonds as polymerizable functional groups are synthesized and characterized. Polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and X-ray diffraction analysis reveal that the bent-shaped lower homologue compounds are crystalline in nature whereas higher homologue compounds display the stable enantiotropic B 6 phase. They exhibit fast photoisomerization effects in solution and relatively slow photoisomerization effects in liquid crystal cells. In solution both trans-cis and cis-trans occur at around 3 s and 200 s, respectively, whereas in solids they occur at around 10 s to 200 min. These are some of the first examples of azobenzene liquid crystals which exhibit very fast switching properties in solutions.

Effect of Molecular Interactions and Homologue Number on UV Absorption Spectra of Liquid Crystalline Alkyl Cyanobiphenyl Dimers: DFT Calculations

“…Although many works on LC absorption spectroscopy (AS) have been documented [29,30], little is known about their self-aggregation, and effect of molecular interactions. The forces lead to molecular aggregation is known as non-covalent, which consist of the dipole orientation force, the induction force, and the dispersion force.…”

Photoresponsive behavior of hydrophilic/hydrophobic-based novel azobenzene mesogens: synthesis, characterization and their application in optical storage devices

“…For azo compounds 10-30, it is necessary to study the kinetics of their cis-trans isomerisation, which was carried out thermally using UV-vis spectroscopy. 43 The experiment was carried out in the dark at room temperature of 27 C and chloroform was used as the solvent. The unimolecular thermal cis-trans isomerisation in the dark obeys eqn (2).…”

Synthesis and optical properties of the isomeric pyrimidine and carbazole derivatives: Effects of polar substituents and linking topology

“…Owing to strong aromaticity, significant p-deficiency, presence of n-p electronic states, pH sensitivity, and ability of its nitrogen atoms to take part in the chelation processes, pyrimidine, among other azaheterocycles is a desired functional moiety to be incorporated in more complex organic structures targeted for numerous applications [3]. p-Conjugated pyrimidine derivatives have been recently utilized in the fabrication of OLEDs [4], sensors [5], supramolecular assemblies [6], liquid crystals [7], and dyes for solar cells [8]. Pyrimidine ring is frequently used in pushepull structures as strong electronwithdrawing unit and together with electron-donating moieties results in intramolecular charge transfer character, which plays a key role in most of the important applications.…”