New 2,2'‐Substituted 6,6'‐Dimethylbiphenyl Derivatives Inducing Strong Helical Twisting Power in Liquid Crystals

Abstract

New optically active tetra‐ortho‐substituted biphenyl chiral dopants for nematic liquid crystals are described. It was shown, with respect to our previous results, that biphenyl chiral dopants bearing only mesogenic residues on their 2,2'‐positions and without any substituents on their 4,4'‐positions gave rise to very high twisting powers in nematic liquid crystals. This powerful and unconventional chiral dopant molecular architecture allowed the design of new tetra‐ortho‐substituted biphenyl derivatives, easier to prepare in optically active form. This simplification of the molecular architecture still affords chiral dopants for nematic liquid crystals with large helical twisting powers and allows more economical large‐scale preparation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Evaluation of chiral dopants for LCD applications

“…It can be seen that Ia, Ic, IIf, and IVg do not suffer from UV and blue wavelength exposure under our test conditions. Contrary to expectation, 13 the same applies to the binaphthalene Va. By contrast, by using a mixture of TADDOls a strong bathochrome shift of the selective reflection wavelength occurred.…”

“…The former tend to undesirable chromatographic effects during the filling process of thin-layer displays perceptible by the appearance of irregularly colored front regions. Obviously, dopants bearing overcrowded or polar molecular structures around the chiral centers such as TADDOLs 13 are predestined for selective surface adsorption. Cholesteric solutions prepared using the dopants I, II, and IV did not show any chromatographic separation in ITO glass cells.…”

Direct enantioseparation of axially chiral 1,1′-biaryl-2,2′-diols using amidine-based resolving agents

“…13 C NMR (100 MHz, CDCl 3 ): d (ppm) 168. 8,160.3,157.9,135.4,133.9,129.2,128.9,127.6,126.2,125.5,119.3,105.7,55.4,41.3,19.9,17.7. IR (KBr): n (cm À1 ) 3449, 3332,3196,3060,2962,2936,2841,1744,1627,1505,1486,1464,1439,1418,1392,1371,1266,1227,1173,1119,1027,1010,957,927,885,855,814.…”

“…13 C NMR (100 MHz, CDCl 3 ): d (ppm) 174. 8,147.0,146.0,134.5,127.0,124.1,124.0,46.8,45.6,38.2,38.1,37.3,33.5,29.9,25.3,24.0,20.5,19.0,16.8. IR (KBr): n (cm À1 ) 3345, 2958,2869,1634,1577,1497,1459,1382,1363,1201,1171,822 (Rac)-6,6 0 -dibromo-1,1 0 -bi-2-naphthol (1b) 27 Rac-1,1 0 -bi-2-naphthol (1a) (1.00 g, 3.49 mmol) was dissolved in dry CH 2 Cl 2 (40 mL) under a nitrogen atmosphere.…”

Mechanisms of Chiral Transfer in Optically Active Dopant – Nematic Liquid Crystal Systems

“…В результате многочисленных исследований было установлено, что допанты с конформационной хиральностью циклов, как правило, демон-стрируют более высокую НТР, и в последнее время большинство работ в этой области было связано с синтезом и изучением допантов именно этой группы. Среди таких соединений заметное место занимают атропоизомерызамещенные бифенилы [37,38] и бинафтилы [39] (схема 1). Допанты, представленные на схеме, демонстрируют значения НТР 20-60 μm -1 в зависимости от природы заместителей и нематического ЖК.…”