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Hiremath U.S.,Center for Soft Matter Research
Tetrahedron Letters | Year: 2013

The first examples of mesogenic bis(N-salicylideneaniline)s (BSANs), wherein two lipophilic (half-disk shaped) entities are interlinked through the dihydroxydiformylbenzene core, were synthesized and characterized. In particular, three constitutional (positional) isomeric BSANs were prepared by the facile twofold condensation of 3,4,5-tris(alkoxy)anilines with 2,3-dihydroxyterephthalaldehyde, 4,6-dihydroxyisophthalaldehyde, and 2,5-dihydroxyterephthalaldehyde and their structures were established by elemental analyses, FT-IR, 1H NMR, and 13C NMR. Proton NMR experiments demonstrated their existence in enol-imine (OH) form solely. Polarizing optical microscopic, differential scanning calorimetric, and powder X-ray diffraction studies evidenced the occurrence of columnar mesomorphism in two sets of isomers. © 2013 Elsevier Ltd. All rights reserved. Source


Hiremath U.S.,Center for Soft Matter Research
Tetrahedron | Year: 2014

Two novel series of optically active dimers comprising cholesterol and biphenyl-4-yl 4-(n-alkoxy)benzoate cores interlinked though either an odd-parity/even-parity spacer have been prepared and characterized. They stabilize an extremely complex, frustrated liquid crystalline state viz., the twist grain boundary (TGB) phase with chiral smectic C structure, denoted as TGBC- phase, over a wide (50-110 °C) temperature range. Notably, the dimers with an odd-parity spacer show an additional frustrated liquid crystal phase namely, the blue phase (BP). The presence of such frustrated phases suggests that the synthesized dimers are characterized by high enantiomeric excess and strong molecular chirality. Thus, 12 new optically active, nonsymmetric dimers reported herein constitute new examples of rarely found strongly chiral, optically pure dimers showing frustrated liquid crystal phase over an adequately wide thermal range. © 2014 Elsevier Ltd. All rights reserved. Source


Varshney S.K.,Center for Soft Matter Research
Liquid Crystals | Year: 2013

Exclusive synthesis and characterisation of new dinitrohexa(alkoxy)triphenylene compounds were carried out. Nitration of 2,3,6,7,10,11-hexa(alkoxy)triphenylene with fuming nitric acid yielded 2,3,6,7,10,11-hexa(alkoxy)-1,5-dinitrotriphenylene with regioisomer 2,3,6,7,10,11-hexa(alkoxy)-1,8-dinitrotriphenylene and that of 1-chloro-2,3,6,7,10,11-hexa(alkoxy)triphenylene yielded 1-chloro-2,3,6,7,10,11-hexa(alkoxy)-5,12-dinitrotriphenylene with regioisomer 1-chloro-2,3,6,7,10,11-hexa(alkoxy)-5,9-dinitrotriphenylene. These isomers were separated by column chromatography and the molecular structures were confirmed by spectroscopic and spectrometric analyses. The liquid crystalline properties were investigated by optical polarising microscopy, differential scanning calorimetry (DSC) and X-ray analysis. The compound 2,3,6,7,10,11-hexa(butyloxy)-1,5-dinitrotriphenylene is a crystalline solid, whereas 2,3,6,7,10,11-hexa(butyloxy)-1,8-dinitrotriphenylene exhibits columnar phases. The higher homologues exhibit hexagonal columnar mesophase with a wide thermal range. Interestingly, 2,3,6,7,10,11-hexa(alkoxy)-1,8-dinitrotriphenylene has the higher clearing temperature compared to its 2,3,6,7,10,11-hexa(alkoxy)-1,5-dinitrotriphenylene isomer. Similarly, 1-chloro-2,3,6,7,10,11-hexa(alkoxy)-5,9-dinitrotriphenylene is liquid and 1-chloro-2,3,6,7,10,11-hexa(alkoxy)-5,12-dinitrotriphenylene exhibits hexagonal columnar mesophase at room temperature. © 2013 Taylor & Francis. Source


Prasad S.K.,Center for Soft Matter Research
Angewandte Chemie - International Edition | Year: 2012

Shape matters: Changes, which are brought about by irradiation, to the properties of a medium have been of immense interest not only in terms of basic science, but also for applications such as data storage media and molecular devices. In the light of a recent publication reporting a photodriven liquid to liquid crystalline transformation (see figure), an overview of similar transitions is presented. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Hiremath U.S.,Center for Soft Matter Research
Liquid Crystals | Year: 2014

Twelve new constitutional bis(N-salicylideneaniline)s (BSANs) belonging to three different series have been prepared and characterised by the two-fold reaction of alkoxyanilines with 2,3-dihydroxyterephthalaldehyde, 4,6-dihydroxyisophthalaldehyde and 2,5-dihydroxyterephthalaldehyde. Their thermal behaviour and liquid crystallinity has been established with the help of polarising optical microscope, differential scanning calorimeter (DSC) and powder X-ray diffraction (XRD). Our study reveals this behaviour as determined by the nature of central core and the number of alkoxy tails. For example, the three series of compounds prepared are either non-mesomorphic or stabilised calamitic and discotic mesophases, such as nematic/smectic C and columnar (Col) phases. These materials represent the first examples of mesogenic BSANs exhibiting mesomorphism. © 2014 © Taylor & Francis. Source

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