The effect of a thiophene ring in the outer position on mesomorphic properties of the bent-shaped liquid crystals

Abstract

Novel bent-shaped compounds with the naphthalene central core possessing an outer thiophene unit in the lengthening arm were synthesized. Mesomorphic behaviour of new materials was studied using optical polarising microscopy, DSC, and electrooptic methods. The structures of mesophases were identified by X-ray diffraction and the structural parameters established. In the case of the thiophene unit in one molecular arm (the phenyl in the opposite arm) we succeeded in obtaining mesogenic properties for all types of lateral substitutions on the central naphthalene core. All non-substituted compounds and materials with the central core substituted by CH 3 or Cl exhibited the B 2 phase. The B 7 phase has been observed for all compounds with CN-substituted central core. Materials with the thiophene unit in both lengthening arms were not liquid crystalline except for the CN-substituted compound exhibiting the B 7 phase. Mesomorphic properties of compounds with the thiophene are compared with those detected on analogous materials with the phenyl ring.

Rational design of diketopyrrolopyrrole-based oligomers with deep HOMO level and tunable liquid crystal behavior by modulating the sequence and strength of the donor moiety

“…The possible reason is that introduction of the thiophene unit between the DPP and difluorobenzothiadiazole leads to a further bend in the molecular structure, which could change the molecular assembly and mesomorphic properties in the solid state. [54][55][56][57] These results can direct us to design and synthesise materials with liquid crystal properties by modulating the sequence of building blocks.…”

A two-state model for the modulated B7 liquid crystalline phase exhibited by bent-core molecules

“…The actual structure that a given compound adopts depends on detailed molecular features, like the flexibility of the core, the location and orientation of dipolar groups, etc. It seems that a fairly large fraction of the B 7 LCs formed by BC compounds exhibit oblique lattices [12,28,[30][31][32], as the number of possible ways of generating such structures is larger.…”

Synthesis and Characterization of Some Boomerang Imine‐Ester Mesogenic Materials Based on Thiophene Unit

“…This type of heterocyclic mesogens is considered as liquid crystalline materials that could be located between the classical linear rod-like mesogens (1,4-disubstituted benzene) and bent-like mesogens (1,3-disubstituted benzene). [14] Therefore, 2,5-disubstituted thiophene derivatives usually described as boomerang molecules due to curvature their chemical structures resulted from the presence an exocyclic bend angle within the thiophene ring (CÀ S-C � 148°) [15][16][17] , Scheme 1. Moreover, the compounds derived from thiophene unit are less backed structures than their analogues derived from 1,4-phenylene causing to decrease in their melting points.…”