- Coumarin substituted symmetric diaminopyridine molecules: Synthesis, mesomorphic characterizations and DFT studies
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The 2, 6-diaminopyridine was symmetrically substituted with coumarins from a lateral side of the molecules. All the molecules characterized by standard spectroscopic methods such as infrared spectroscopy, and nuclear magnetic resonance spectroscopy techniques. Mesomorphic properties are evaluated by the differential scanning calorimetry and the polarized optical microscope. The measurements show that the lower members did not favour liquid crystal formation, while higher members are exhibiting liquid crystalline, namely Nematic mesophase. The DFT computations manifest the nature of liquid crystal geometrical aspects.
- Al-Mohammed, Mohammad Hameed,Ameen, Wissam Ahmed,Mohammad, AbdulKarim-Talaq,Srinivasa, H. T.
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- Ferroelectric Liquid Crystals: Synthesis and Thermal Behavior of Optically Active, Three-Ring Schiff Bases and Salicylaldimines
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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.
- Veerabhadraswamy, Bhyranalyar N.,Rao, Doddamane S. Shankar,Yelamaggad, Channabasaveshwar V.
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supporting information
p. 1012 - 1023
(2018/04/23)
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- Optically active, three-ring calamitic liquid crystals: The occurrence of frustrated, helical and polar fluid mesophases
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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.
- Veerabhadraswamy,Rao, D. S. Shankar,Prasad, S. Krishna,Yelamaggad
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p. 2011 - 2027
(2015/03/30)
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- Stable ferroelectric liquid crystals derived from salicylaldimine-core
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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.
- Veerabhadraswamy, Bhyranalyar N.,Rao, D. S. Shankar,Yelamaggad, Channabasaveshwar V.
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p. 4539 - 4551
(2015/04/14)
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- Side-on main-chain liquid crystalline polymers prepared by acyclic diene metathesis polymerization and thiol-ene click step-growth polymerization
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In this manuscript, we design and synthesize a series of X-shaped mesogenic monomers, bearing two terminal-alkene tails. Starting from these X-shaped monomers, acyclic diene metathesis polymerization and thiol-ene polyaddition are applied for the first time to prepare two series of side-on main-chain liquid crystalline polymers (LCPs), respectively. The mesomorphic behaviors and structure-property relationships of these new polymers are studied in detail by a combination of 1H NMR, GPC, TGA, DSC, POM, and XRD experiments. It turns out that the length of alkoxy terminal chains of the embedded mesogens and the length of the spacer connecting two adjacent mesogens on the polymer backbones markedly influence the mesomorphic properties. Furthermore, a side-on main-chain liquid crystalline elastomer fiber is prepared by crosslinking the LCP using a UV-sensitive bifunctional benzophenone crosslinker. In comparison with the pure polymer fiber's monodomain alignment, the crosslinked elastomer fiber however shows nonaligned polydomain structure, probably due to the order competitions between the mixed crosslinkers, mesogens, and polymer backbones. 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1086-1098 A series of X-shaped mesogenic monomers bearing two polymerizable terminal-alkene tails are designed and synthesized. Starting from these X-shaped monomers, acyclic diene metathesis polymerization (ADMET) and thiol-ene click step-growth polymerization are applied to prepare two series of side-on main-chain liquid crystalline polymers, respectively. Copyright
- Yang, Hong,Lv, You-Jing,Lin, Bao-Ping,Zhang, Xue-Qin,Sun, Ying,Guo, Ling-Xiang
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p. 1086 - 1098
(2014/03/21)
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- IMIDAMIDE SPHINGOSINE KINASE INHIBITORS
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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.
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Page/Page column 23
(2012/09/05)
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- Development of amidine-based sphingosine kinase 1 nanomolar inhibitors and reduction of sphingosine 1-phosphate in human leukemia cells
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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.
- 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.
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supporting information; experimental part
p. 3524 - 3548
(2011/07/07)
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- A new way to access chiral liquid crystals: Organocatalyst-mediated synthesis of chiral rod-like liquid crystals
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In this article, an asymmetric organocatalytic way to prepare chiral liquid crystals from non-chiral starting materials was described. By using L-proline as the organocatalyst, several new chiral rod-like liquid crystals that are elusive with traditional methods were prepared. In addition, a series of novel enone-containing rod-like liquid crystals were also obtained as side-products. Mesomorphic properties of all new compounds were studied by Polarized Optical Microscope and Differential Scanning Calorimetry. Copyright Taylor & Francis Group, LLC.
- Wang, Li,Liu, Xiao-Jun,Huang, Ping,Gong, Qing-Ping,Li, Yong-Hong,Wang, Bi-Qin,Zhao, Ke-Qing
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scheme or table
p. 53 - 59
(2012/07/14)
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- Self-assembly of azobenzene based side-chain liquid crystalline polymer and n-alkyloxybenzoic acids
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Liquid crystalline pendant polymeric complexes have been obtained by supramolecular assembly of two mesogenic components namely, poly[4-(10- acryloyloxydecyloxy)-4'- phenylazobenzonitrile] (P10) and 4-alkyloxybenzoic acids (A7-A12). Hydrogen bond formed between carboxylic acid and cyano moiety served as molecular bridge. The polymeric complexes acquitted as undivided liquid crystalline properties exhibited stable and enantiotropic mesophases. The precursor, monomer and polymer were analysed by 1H-NMR and 13C-NMR spectroscopy. The hydrogen bonding interaction in polymer complexes (P10-A7 to P10-A12) was investigated by FT-IR spectroscopy. The thermal behaviours and textural analysis were studied by differential scanning calorimetry and polarized optical microscopy respectively. Indian Academy of Sciences.
- Gayathri, Kumarasamy,Balamurugan, Subramanian,Kannan, Palaninathan
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experimental part
p. 255 - 263
(2012/05/20)
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- Electro-optical switching studies on 1,3-phenylene based banana shaped liquid crystals
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This work deals with the study of the thermotropic liquid crystalline properties of new asymmetric bent core liquid crystals. The thermotropic properties was analyzed by polarized optical microscopy, differential scanning calorimetric analysis and variable temperature X-ray diffraction measurements. Effect of equal terminal chain with asymmetric bent core system on mesomorphic behavior was examined. The shorter methyl chain compound 10a of exhibits B 1 mesophase and higher homologs (10b and 10c) shows antiferroelectric B2 mesophases, which was studied by electro-optical measurements.
- Balamurugan,Kannan,Yadupati,Roy
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experimental part
p. 118 - 124
(2011/10/03)
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- Oxime Carbamate-Discovery of a series of novel FAAH inhibitors
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A series of novel oxime carbamates have been identified as potent inhibitors of the key regulatory enzyme of the endocannabinoid signaling system, fatty acid amide hydrolase (FAAH). In this Letter, the rationale behind the discovery and the biological evaluations of this novel class of FAAH inhibitors are presented. Both in vitro and in vivo results of selected targets are discussed, along with inhibition kinetics and molecular modeling studies.1.
- Sit,Conway, Charles M.,Xie, Kai,Bertekap, Robert,Bourin, Clotilde,Burris, Kevin D.
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supporting information; experimental part
p. 1272 - 1277
(2010/06/17)
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- Hydrogen bonding versus van der waals interactions: Competitive influence of noncovalent interactions on 2d self-assembly at the liquid-solid interface
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The structures of the self-assembled monolayers of various 4-alkoxybenzoic acids physisorbed at the liquid-solid interface were established by employing scanning tunnelling microscopy (STM). This study has been essentially undertaken to explore the competitive influence of van der Waals and hydrogen-bonding interactions on the process of two-dimensional self-assembly. These acid derivatives form hydrogen-bonded dimers as expected; however, the dimers organise themselves in the form of relatively complex lamellae. The characteristic feature of these lamellae is the presence of regular discommensurations or kinks along the lamella propagation direction. The formation of kinked lamellae is discussed in light of the registry mechanism of the alkyl chains with the underlying graphite substrate. The location of the kinks along a lamella depends on the number (odd or even) of carbon atoms in the alkyl chain. This result indicates that concerted van der Waals interactions of the alkyl chain units introduce the odd/even chain-length effect on the surface-assembled supramolecular patterns. The odd/even effects are retained even upon complexation with a hydrogen-bond acceptor. However, as the solvent is changed from 1-phenyloctane to 1-octanoic acid, the kinked lamellae as well as the odd/even effects disappear. This solvent-induced convergence of supramolecular patterns is attained by means of co-crystallisation of octanoic acid molecules in the 2D crystal lattice, which is evident from high-resolution STM images. The solvent co-adsorption phenomenon is discussed in terms of competing van der Waals and hydrogen-bonding interactions. Discontinuous but ordered: Noncovalent interactions play an exceedingly decisive role in the process of self-assembly. To gain better insight into the role of noncovalent interactions, the competitive influence of hydrogen-bonding and van der Waals interactions was explored in the monolayers formed by simple 4-alkoxybenzoic acids at the liquid-solid interface (see image). Copyright
- Mali, Kunal S.,Lava, Kathleen,Binnemans, Koen,Defeyter, Steven
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supporting information; experimental part
p. 14447 - 14458
(2011/03/21)
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- Liquid crystalline properties of unsymmetrical N-(o-hydroxybenzylidene)- N′-(4-n-alkoxybenzoyloxybenzylidene)azines: Synthesis and characterization
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A new series of mesogenic unsymmetrical azines, N-(o-hydroxybenzylidene)- N′-(4-n-alkoxybenzoyloxybenzylidene)azines, HOC6H 4CH=N-N=CHC6H4OCOC6H4O CmH2m+1 (m=7, 8, 9, 10, 11, 12, 14, and 16) have been prepared. They have been characterized by elemental analyses, FT-IR, UV-visible, 1H, and 13C NMR (Nuclear Magnetic Resonance) spectra. The mesomorphic properties of these compounds were investigated by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The azines m=7, 10, and 14 exhibit features of enantiotropic nematic (N) mesophase whereas azines m=8, 11 exhibit features of a monotropic nematic phase. The azines m=9, 12, and 16 do not exhibit mesogenic nature. Copyright Taylor & Francis Group, LLC.
- Singh, Bachcha,Pandey, Ashwini
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scheme or table
p. 148 - 158
(2010/09/05)
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- Liquid crystalline properties of 3-[4-(4′- alkoxybenzoyloxybenzylidene) amino]-1,2,4-triazines: Synthesis and characterization
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A new series of 3-[4-(4′-alkoxybenzoyloxybenzylidene)amino]-1,2,4- triazines, C3H2N3N=CHC6H 4OCOC6H4OCmH2m+1 where m=6, 7, 8, 9, 10, 11, 12, 14, and 16 have been synthesized. These compounds have been characterized by elemental analyses, FT-IR, UV-visible, 1H, and 13C NMR spectroscopy. Mesomorphic properties of these compounds were studied by differential scanning calorimetry and polarizing microscopy. The mesomorphic nature of these compounds is dependent on the alkoxy chain length. The compounds (m=6, 7) do not exhibit mesomorphism while the compounds (m=8, 9, 11, 12, 14) show a monotropic nematic mesophase in cooling cycle. The 3-[4-(4′-decyloxybenzoyloxybenzylidene)amino]-1,2,4-triazine displays an enantiotropic nematic mesophase and the hexadecyloxy compound exhibits the smectic A mesophase. Copyright Taylor & Francis Group, LLC.
- Singh, Bachcha,Pandey, Ashwini,Singh, Sachin Kumar
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experimental part
p. 127 - 137
(2010/09/05)
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- Liquid crystalline properties of 2,5-bis[4-n-alkoxybenzoyloxy-(4- benzoyloxy)]-3,6-dichloro-1,4-benzoquinones: Synthesis and characterization
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A new series of 2,5-bis[4-n-alkoxybenzoyloxy-(4-benzoyloxy)]-3,6-dichloro- 1,4-benzoquinones, C6Cl2O2(OCOC 6H4OCOC6H4OR)2, where R=CmH2m+1 and m=7, 8, 9, 10, 11, 12, 14, and 16, have been synthesized. These compounds have been characterized by elemental analyses, FT-IR, UV-visible, 1H, and 13C NMR spectra. Mesomorphic properties of these compounds were studied by differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). The mesomorphic nature of these compounds depends on the alkoxy chain length. The compounds (m=7, 8, 9, 10) exhibit a monotropic nematic mesophase in cooling cycle, while the compounds (m=11, 12, 14, and 16) show no mesogenic behavior in both heating and cooling cycles. The intermolecular interactions play a vital role in the mesogenic nature of these compounds. In higher homologues of the series the intermolecular interactions become more prominent leading to loss in mesogenic nature. Copyright Taylor & Francis Group, LLC.
- Singh, Bachcha,Pandey, Ashwini
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experimental part
p. 138 - 147
(2010/09/05)
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- Calamitic organometallic liquid crystals with terminal metal. Syntheses and liquid crystal properties of dicarbonylrhodium(I) β-diketonate complexes
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A series of novel organometallic complexes based on γ-substituted β-diketone ligands with terminal metal Rh(I) have been prepared by reaction of the ligands with [Rh(CO)2(μ-Cl)]2. The mesomorphism of the ligands and complexes has been investigated using DSC and polarizing microscope. It is found that non-mesogenic ligands with n=7, 8, 9, 10, 11 can form liquid crystalline phase by direct coordination to metal. The effect of the terminal carbon number on the mesomorphism has also been discussed.
- Wan, Wen,Guang, Wen-Jie,Zhao, Ke-Qin,Zheng, Wei-Zhong,Zhang, Liang-Fu
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p. 157 - 161
(2007/10/03)
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- Synthese de cristaux liquides nematiques a squelette rigide organometallique
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Copper, nickel and palladium complexes with N-(4-(4'-n-alkoxybenzoyloxy) salicylidene)-4-n-butylaniline and N-(4-(4'-n-hexadecyloxybenzoyloxy) salicylidene)-4-n-alkoxyaniline have been synthesized.The copper and palladium derivatives show mesomorphic properties and exhibit a nematic phase over a large temperature range.In contrast, the nickel derivatives do not show any mesomorphic behavior.The liquid-crystalline-phase transitions were determined using a differential scanning calorimeter and a polarizing microscope.All these physical characteristics are compared and discussed.
- Bayle, J.-P.,Bui, E.,Perez, F.,Courtieu, J.
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p. 532 - 536
(2007/10/02)
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- RECHERCHES SUR LES SUBSTANCES MESOGENES-VIII; PREPARATION ET PROPERTIES MESOMORPHES DE SERIES ISOMETRIQUES
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The synthesis and the mesomorphic properties of various series of isometric mesogenic compounds are described.It is confirmed that isometric mesogenic molecules may be nematogenic and/or smectogenic according to the position of the polar rigid core.
- Malthete, Jacques,Canceill, Josette,Gabard, Jacqueline,Jacques, Jean
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p. 2815 - 2821
(2007/10/02)
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- SYNTHESIS AND MESOMORPHIC PROPERTIES OF THE HOMOLOGOUS SERIES OF 4-ALKYL OR ALKOXY-4 prime -BROMO OR CYANOTOLANES.
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A homologous series of 4-alkyl or alkoxy-4 prime -bromo or cyanotolanes in which the alkyl group is C//4 yields C//1//0 and the alkoxy group is C//1 yields C//1//2, was prepared. Interphase transitions between solid, mesomorphic and isotropic phases were studied by hot stage microscopy and differential scanning calorimeter. The bromo compounds have a smectic polymorphism. Three pure products of cyano derivatives with the chains C//9H//1//9O, C//1//0H//2//1O amd C//1//0H//2//1 present an enantiotropic or monotropic reentrant nematic phase at atmospheric pressure. The reentrant phenomenon itself is discussed as well as the absence of correlation between T//N//A/T//N//I McMillan parameter and the heat of transition. A plot of the nematic isotropic transition temperatures against the number of carbon atoms in the alkoxy chain shows the usual odd even effect.
- Tinh,Pourrere,Destrade
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p. 125 - 139
(2007/10/02)
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