Nematic 2,5-disubstituted thiophenesElectronic supplementary information (ESI) available: extensive synthetic information. See http://www.rsc.org/suppdata/jm/b2/b202073b/

Abstract

A large number of new liquid crystals incorporating the 2,5-disubstituted thiophene ring have been prepared and their mesomorphic behaviour studied in order to systematically investigate the correlation between the molecular structure and mesomorphism of thiophene derivatives with different shapes, polarisability and polarity. As a consequence of these investigations we have prepared a new class of liquid crystals incorporating a 2,5-disubstituted thiophene ring and a conjugated trans-carbon-carbon double bond in the terminal chain. These novel thiophene derivatives are the first liquid crystals incorporating a 2,5-disubstituted thiophene ring to exhibit a nematic phase at room temperature. This enables the flexoelectric coefficients of a bent-shaped molecule to be measured directly and at room temperature for the first time to the authors' knowledge. Many of these new thiophenes exhibit a high birefringence and a high nematic clearing point and are of potential use as components of nematic mixtures in LCDs.

Synthesis and Mesomorphic Behavior of 3‐Alkyl‐2,5‐ bis[p‐(hexa‐2,4‐dienoyloxy)phenyl]‐Thiophene Derivatives

“…For example, the reported 2,5-diarylated thiophene nematic mesogens bearing one terminal ester alkyl (alkenyl) chain were synthesized in low yields with high melting points (110-210 ℃) which were unsuitable for application. 1 With a purpose to decreasing the melting points and increasing the yields of such kind of materails, we decided to introduce lateral alkyl chains into such molecules; also by considering the following facts: an ester group as a linkage between the central core and the terminal substituent can lead to the formation of a nematic phase of low viscosity, while the presence of a carbon-carbon double bond in a terminal chain is also conducive to mesophase formation, 6 we therefore decided to synthesize 3-alkyl-2,5-diarylated thiophene bearing two terminal diene ester chains 7 n by using Kumada and Suzuki coupling reactions as key steps (Scheme 1). The mesophase behavior of 7 n was studied by polar optical microscopy (POM).…”

“…[1][2][3][4][5] However systematic studies on the properties and application of such materials are hindered because of lacking of an efficient synthesis methology. For example, the reported 2,5-diarylated thiophene nematic mesogens bearing one terminal ester alkyl (alkenyl) chain were synthesized in low yields with high melting points (110-210 ℃) which were unsuitable for application.…”

Facile synthesis of new Pd(II) and Cu(II) based metallomesogens from ligands containing thiophene rings

“…This type of molecules can be particularly useful in the field of optics and electro-optics . The more recent developments in functional LC demanding materials for NLO applications [9,10], as active materials for OLED [11,12] or for molecular switches [13] are to be recalled.Moreover, when compared with 1,4-disubstituted benzene units, thiophene core units generally display more significant lateral dipole moment [7,8] that can contribute to an increase of dielectric anisotropy and dielectric biaxiality. The introduction of thiophene units can change considerably the polarity, polarizability and geometry of the mesogen, affecting often favorably the kind of mesophases and the phase transition temperatures as well as other properties of the molecule such as melting point and viscosity [8].…”

“…Many five membered rings with nitrogen, oxygen, sulfur, or other heteroatoms attract attention as their non planar structures afford a variety of desirable features in the so called bent-shaped or ''banana" mesogens [3,4]. Thiophene in particular has emerged as a unit worth of increasing attention, especially for its versatility in synthesis of bent core mesogens [5][6][7][8]. This type of molecules can be particularly useful in the field of optics and electro-optics .…”

Synthesis of a New Liquid Crystal, 3-Hydroxy-4-{[(6-methoxy-1,3-benzothiazol-2-yl)imino]methyl}phenyl Palmitate

“…Many kinds of heterocyclic structures, such as 1,3,4-thiadiazole [2], thiopene [3], 2,1,3-benzoxadiazole [4] and benzothiazole [5] have been introduced as core centre in liquid crystalline compounds. In this paper, we report here the synthesis of new Schiff base ester comprising benzothiazole unit, 6-methoxy-2-(2-hydroxy-4-hexadecanoyloxybenzylidenamino)benzothiazole.…”