New pyridine based liquid crystalline esters with different terminal chains

Synthesis and characterization of new pyridine-based chiral calamitic liquid crystals

“…The DSC traces displays two endotherms upon heating associated to a Cr 1 -Cr 2 -Iso phase sequence and two exotherms upon cooling associated to the phase sequence Iso-(SmA)-Cr 1 . On the contrary, the methyl picolinate ester 4, which was previously reported, 24 exhibits enantiotropic smectic A mesophase. The mesophase of both simple pyridine-based methyl esters 4 and 5 carrying a ndodecyloxy chain is characterized by the typical fan-shaped texture (see Fig.…”

“…25 4-Dodecyloxybenzen boronic acid 26 (1) was synthesized starting from 1-bromo-4dodecyloxybenzen 26 by using previously reported procedure. 24,26 Methyl 5-bromopyridine-2carboxylate (2) and methyl 6-chloropyridine-3-carboxylate (3) were commercially purchased. 0.5 mmol 4-Dodecyloxybenzene boronic acid (1), 0.5 mmol the initial halogenated derivatives (2, 3, 6a,b, 8a,b and 9a,b) and 0.022 mmol Pd(PPh 3 ) 4 were dissolved in 10 mL of 1,2-dimethoxyethane under argon atmosphere.…”

“…Table 1 Mesophase, phase transition temperatures (°C) and the corresponding transition enthalpies (ΔH kJ/mol) a of the compounds 4 24 The DSC thermograms of compound 7a carrying a (S)-2-methylbutyloxy end chain shows three endotherms for a phase transition sequence of crystal (Cr)-chiral smectic C* (SmC*)smectic A (SmA) -isotropic phase (Iso) and three exotherms for the reverse phase transition sequence (Table 1, Fig. 1).…”

“…22,23 Recently, we reported the compounds that the internal phenyl ring of the biphenyl system replaced with a 3-pyridyl ring to generate functional materials with an interesting mesogenic behavior. 24 Herein, we report the synthesis and the mesomorphic properties of novel chiral calamitic mesogens, consisting of n-dodecyloxyphenyl substituted pyridine carboxylate core linked to one or two benzene rings through ester linkers. Into the other terminal, a flexible (S)-2-methylbutyloxy or (S)-3,7-dimethyloctyloxy chiral chain was introduced to focus on the effect of molecular chirality on mesophases of pyridine-based calamitic molecules.…”

Pyridine-based chiral smectogens: effects of polar end groups on liquid crystal properties

“…[40,41] Additionally, compound 7b, which has a (S)-3,7-dimethyloctyloxy chiral moiety and a chloro polar head, shows richer mesomorphism and mesophase stability as compared with the mesomorphic behavior observed for pyridine-based calamitic esters carrying same chiral moiety. [42] On the other hand, it can be said that the use of a longer terminal alkyl chain in the members with three aromatic rings clearly allows to stabilize the formation SmA phase over larger temperature range in comparison of the introduction of shorter branched chain such as (S)-2-methylbutoxy group at the terminal. One point should be mentioned here that longer terminal chains reduce the melting point by providing mobility and flexibility in the structure and this case allows designing mesogens with desired properties for many applications.…”