60951-75-9Relevant articles and documents
Ferroelectric Liquid Crystals: Synthesis and Thermal Behavior of Optically Active, Three-Ring Schiff Bases and Salicylaldimines
Veerabhadraswamy, Bhyranalyar N.,Rao, Doddamane S. Shankar,Yelamaggad, Channabasaveshwar V.
supporting information, p. 1012 - 1023 (2018/04/23)
The chiral ferroelectric smectic C (SmC*) phase, characterized by a helical superstructure, has been well exploited in developing high-resolution microdisplays that have been effectively employed in the fabrication of a wide varieties of portable devices. Although, an overwhelming number of optically active (chiral) liquid crystals (LCs) exhibiting a SmC* phase have been designed and synthesized, the search for new systems continues so as to realize mesogens capable of meeting technical necessities and specifications for their end-use. In continuation of our research work in this direction, herein we report the design, synthesis, and thermal behavior of twenty new optically active, three-ring calamitic LCs belonging to four series. The first two series comprise five pairs of enantiomeric Schiff bases whereas the other two series are composed of five pairs of enantiomeric salicylaldimines. In each pair of optical isomers, the configuration of a chiral center in one stereoisomer is opposite to that of the analogous center in the other isomer as they are derived from (3 S)-3,7-dimethyloctyloxy and (3 R)-3,7-dimethyloctyloxy tails. To probe the structure–property correlations in each series, the length of the n-alkoxy tail situated at the other end of the mesogens has been varied from n-octyloxy to n-dodecyloxy. The measurement of optical activity of these chiral mesogens was carried out by recording their specific rotations. As expected, enantiomers rotate plane polarized light in the opposite direction but by the same magnitude. The thermal behavior of the compounds was established by using a combination of optical polarizing microscopy, differential scanning calorimetry, and powder X-ray diffraction. These complementary techniques demonstrate the existence of the expected, thermodynamically stable, chiral smectic C (SmC*) LC phase besides blue phase I/II (BPI or BPII) and chiral nematic (N*) phase. However, as noted in our previous analogous study, the vast majority of the Schiff bases show an additional metastable, unfamiliar smectic (SmX) phase just below the SmC* phase. Notably, the SmC* phase persists over the temperature range ≈80–115 °C. Two mesogens chosen each from Schiff bases and salicylaldimines were investigated for their electrical switching behavior. The study reveals the ferroelectric switching characteristics of the SmC* phase featuring the spontaneous polarization (PS) in the range 69–96 nC cm?2. The helical twist sense of the SmC* phase as well as the N* phase formed by a pair of enantiomeric Schiff bases and salicylaldimines has been established with the help of circular dichroism (CD) spectroscopic technique. As expected, the SmC* and the N* phase of a pair of enantiomers showed mirror image CD signals. Most importantly, the reversal of helical handedness from left to right and vice versa has been evidenced during the N* to SmC* phase transition, implying that the screw sense of the helical array of the N* phase and the SmC* phase of an enantiomer is opposite.
Stable ferroelectric liquid crystals derived from salicylaldimine-core
Veerabhadraswamy, Bhyranalyar N.,Rao, D. S. Shankar,Yelamaggad, Channabasaveshwar V.
, p. 4539 - 4551 (2015/04/14)
Five pairs of enantiomers derived from salicylaldimine-core have been prepared by condensing (R)- or (S)-4-(octan-2-yloxy)anilines with 4-formyl-3-hydroxyphenyl 4-(n-alkoxy)benzoates. They have been designed to probe the correlation between molecular structure and mesomorphism, and especially to provide stable mesogens having potential for applications in ferroelectric liquid crystal devices. Thus, they have been substituted with a chiral tail at one end and by n-alkoxy chains of varying length at the other terminal. A detailed study confirms an indistinguishable behavior of all ten mesogens exhibiting an enantiotropic chiral smectic C (SmC) phase besides blue phase (BP) and chiral nematic (N) phase. The SmC phase occurring over a 50-70 °C thermal width shows ferroelectric switching with spontaneous polarization (Ps) value crossing over 100 nC/cm2. Circular dichroism spectroscopic study of the mesophases confirms the chromophores of the molecules being in the macroscopic chiral (helical) environment.
Optically active, three-ring calamitic liquid crystals: The occurrence of frustrated, helical and polar fluid mesophases
Veerabhadraswamy,Rao, D. S. Shankar,Prasad, S. Krishna,Yelamaggad
, p. 2011 - 2027 (2015/03/30)
Herein, we report on the synthesis, characterization, liquid crystalline behavior and chirooptical properties of five (R)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates and their enantiomers, namely, (S)-4-{[(4-(octan-2-yloxy)phenyl)imino]methyl}phenyl 4-(n-alkoxy)benzoates. These three-ring rod-like mesogens were prepared by acid catalyzed condensation of (R)-/(S)-4-(octan-2-yloxy)anilines with 4-formylphenyl 4-(n-alkoxy)benzoates. Thus, each pair of enantiomers comprises (R)-2-octyloxy and (S)-2-octyloxy chiral tails. In order to understand the structure-property correlations, the length of the paraffinic chain incorporated at the other end has been varied from n-octyloxy to n-dodecyloxy. A detailed study carried out by means of several complimentary techniques reveals the stabilization of liquid crystal phases that hold great promise in applied sciences especially in various device applications. In particular, the occurrence of mesophases such as the blue phase-I/II (BPI or BPII) and chiral nematic (N) and chiral smectic C (SmC) phases has been evidenced unequivocally with the help of polarizing microscopy, differential scanning calorimetry, X-ray diffraction and electrical switching. Besides, the occurrence of an unknown, metastable smectic (SmX) phase below the SmC phase has been noted. This study shows that the length of the terminal tail seems to determine the thermal range of the SmC phase. The enantiotropic SmC phase exhibiting ferroelectric switching behavior occurs over 60 °C thermal range; notably, the spontaneous polarization (Ps) value crosses over 100 nC cm-2. The photophysical properties and chirooptical behavior of the mesogens have been studied with the aid of UV-vis absorption and circular dichroism (CD) spectroscopic methods, respectively; the latter technique has been especially used to ascertain the twist sense of the N and SmC phases formed by a pair of enantiomers. The reversal of the helix-sense (from right to left and vice versa) during the N-SmC phase transition has been observed for the first time.
Non-symmetric dimers comprising chalcone and cholesterol entities: An investigation on structure-property correlations
Achalkumar, Ammathnadu S.,Shankar Rao, Doddamane S.,Yelamaggad, Channnabasaveshwar V.
supporting information, p. 4235 - 4248 (2014/11/07)
Four series of new dimers formed by interlinking chalcone and cholesterol mesogenic entities through spacers of varying length and parity have been synthesized and characterized by polarizing optical microscopy, differential scanning calorimetry, X-ray diffraction and electrical switching studies. The structure of the chalcone core has been systematically modified to investigate the effect of the molecular structure on the thermal behaviour of the dimers. The study demonstrates the dramatic dependence of thermal behaviour of these dimers on the nature of the chalcone as well as the length and parity of the spacer. the Partner Organisations 2014.
3-(2-AMINO-ETHYL)-ALKYLIDENE)-THIAZOLIDINE-2,4-DIONE AND 1-(2-AMINO-ETHYL)-ALKYLIDENE-1,3-DIHYDRO-INDOL-2-ONE DERIVATIVES AS SELECTIVE SPHINGOSINE KINASE 2 INHIBITORS
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Page/Page column 27, (2013/08/28)
3-(2-amino-ethyl)-5-[3-(4-substituted-phenyl)-alkylidene)-thiazolidine-2,4-dione and l-(2-amino-ethyl)-3-alkylidene-l,3-dihydro-indol-2-one and derivatives thereof are provided for use as selective SphK2 inhibitors and for use in the treatment of human diseases, such as cancer.
IMIDAMIDE SPHINGOSINE KINASE INHIBITORS
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Page/Page column 22-23, (2012/09/05)
Imidamide (amidine) analogs that can inhibit the activity of sphingosine kinase 1 and sphingosine kinase 2 (SphK1 and SphK2) are provided. The compounds can prevent angiogenesis in tumors.
Multifunctional organic fluorescent materials derived from 9,10-distyrylanthracene with alkoxyl endgroups of various lengths
Zhang, Xiqi,Chi, Zhenguo,Xu, Bingjia,Jiang, Long,Zhang, Yi,Liu, Siwei,Xu, Jiarui,Zhou, Xie
supporting information, p. 10895 - 10897,3 (2020/09/16)
A series of remarkable multifunctional 9,10-distyrylanthracene derivatives (DSAn, n = 7-12) was synthesized. All derivatives possess typical aggregation-induced emission (AIE) property. Some of the derivatives exhibit multifunctional properties, including AIE, mechanofluorochromism, vapochromism, thermochromism, and mesomorphism, which are rarely found to exist simultaneously in a single compound.
Synthesis, characterization and fluorescent property evaluation of 1,3,5-triaryl-2-pyrazolines
Hasan, Aurangzeb,Abbas, Asghar,Akhtar, Muhammed Nadeem
experimental part, p. 7789 - 7802 (2011/11/05)
A series of 1,3,5-triaryl-2-pyrazolines was synthesized by dissolving the corresponding 4-alkoxychalcones in glacial acetic acid containing a few drops of concentrated hydrochloric acid. This step was followed by the addition of (3,4-dimethylphenyl) hydrazaine hydrochloride. Finally the target compounds were precipitated by pouring the reaction mixture onto crushed ice. The structures of the synthesized compounds were established by physicochemical and spectroscopic methods. The 1,3,5-triaryl-2-pyrazolines bearing homologous alkoxy groups were found to possess fluorescence properties in the blue region of the visible spectrum when irradiated with ultraviolet radiation. The fluorescent behavior of these compounds was studied by UV-Vis and emission spectroscopy, performed at room temperature.
Development of amidine-based sphingosine kinase 1 nanomolar inhibitors and reduction of sphingosine 1-phosphate in human leukemia cells
Kennedy, Andrew J.,Mathews, Thomas P.,Kharel, Yugesh,Field, Saundra D.,Moyer, Morgan L.,East, James E.,Houck, Joseph D.,Lynch, Kevin R.,MacDonald, Timothy L.
supporting information; experimental part, p. 3524 - 3548 (2011/07/07)
Sphingosine 1-phosphate (S1P) is a bioactive lipid that has been identified as an accelerant of cancer progression. The sphingosine kinases (SphKs) are the sole producers of S1P, and thus, SphK inhibitors may prove effective in cancer mitigation and chemosensitization. Of the two SphKs, SphK1 overexpression has been observed in a myriad of cancer cell lines and tissues and has been recognized as the presumptive target over that of the poorly characterized SphK2. Herein, we present the design and synthesis of amidine-based nanomolar SphK1 subtype-selective inhibitors. A homology model of SphK1, trained with this library of amidine inhibitors, was then used to predict the activity of additional, more potent, inhibitors. Lastly, select amidine inhibitors were validated in human leukemia U937 cells, where they significantly reduced endogenous S1P levels at nanomolar concentrations.
Synthesis and characterization of mesogenic 1,3,4-oxadiazole derivatives
Mahadeva,Umesha,Rai,Nagappa
scheme or table, p. 274 - 282 (2011/08/02)
A synthesis of homologous series of mesogenic 2-amino-5-alkkloxyphenyl-1,3, 4-oxadiazoles were prepared by the oxidative cyclisation of alkyloxybenzaldehyde semicarbozones (4) using chloramines-T (CAT) as osidate via intramolecular cycloaddition reaction. The reaction proceeds in better yield (75-85%) giving the product as solid with low melting points. The optical texture studies have been carried out using Leitz polarizing microscope to identify the liquid crystalline phases at different temperatures and it is found that the synthesized compounds exhibit nematic (N), smectic C (Sm C), smectic I (Sm I) and smectic G (Sm G) phases, sequentially at different temperatures. Copyright Taylor & Francis Group, LLC.
