- Highly ordered smectic structures of disc-rod luminescent liquid crystals: The role of the tolane group
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Two novel calamitic tolane luminogen-modified triphenylene-based discotic luminescent liquid-crystals (LLC) were rationally designed and synthesized to investigate the self-assembly competition between triphenylene discogens and tolane calamitic mesogens.
- Liu, Yurong,Li, Wei,Zhou, Xuan,Wong, Wai-Yeung,Yu, Zhen-Qiang
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p. 3555 - 3561
(2021/03/26)
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- Quinolines by three-component reaction: Synthesis and photophysical studies
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The synthesis of five quinolines 8-octyloxy-4-[4-(octyloxy)phenyl]quinoline and 6-alkoxy- 2-(4-alkoxyphenyl)-4-[(4-octyloxy)aryl]quinolines are described by three-component coupling reaction mediated by Lewis acid FeCl3 and Yb(OTf)3. 4-n-octyloxybenzaldehyde, anisaldehyde, 4-n-octyloxyaniline p-anisidine, and 1-ethynyl-4-heptyloxybenzene, 1-ethynyl-4-octyloxybenzene and 2-ethynyl-6-heptyloxynaphthalene are the reagents in this protocol. A Yb3+ catalyst resulted in higher yields of quinolines than Fe3+. Polarizing optical microscopy (POM) revealed that none of the quinolines were liquid crystals, even the more anisotropic. UV-Vis measurements of one of the quinolines in polar solvent show two absorption bands at 280 and 350 nm related to π,π?and n,π?transitions. No changes were observed to lower-energy absorption band (ε 4 mol L-1 cm-1) related to n,π?transition. A laser flash photolysis study for one of the quinolines relates a main transient band at 450 nm with a lifetime of 2.6 μs in ethanol, which is completely quenched in the presence of oxygen. This transient band was assigned to triplet-triplet absorption of one of the quinolines, which is semi-oxidised in the presence of phenol. Radiative rate constants have been determined along singlet and triplet excited state energies (3.39 and 3.10 eV, respectively). The chemical structure of one of the quinolines was also unequivocally confirmed by single-crystal X-ray analysis.
- Sales, Eric S.,Schneider, Juliana M. F. M.,Santos, Marcos J. L.,Bortoluzzi, Adailton J.,Cardoso, Daniel R.,Santos, Willy G.,Merlo, Aloir A.
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p. 562 - 571
(2015/03/14)
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- Synthesis of unsymmetrical aryl-ethynylated benzenes via regiocontrolled Sonogashira reaction of 1,3,5-tribromobenzene
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Sonogashira coupling of trimethylsilylacetylene with 4-alkyloxy-1-iodobenzenes gave 2-(4-(alkyloxy)phenyl)ethynyltrimethylsilanes which undergo deprotection via removal of TMS-group using tetrabutylammonium fluoride (TBAF) in THF at room temperature to af
- Dawood, Kamal M.,Hassaneen, Hamdi M.,Abdelhadi, Hyam A.,Ahmed, Mohamed S. M.,Mohamed, Mohamed A.-M.
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p. 1688 - 1695
(2015/01/08)
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- Synthesis of diphenyl-diacetylene-based nematic liquid crystals and their high birefringence properties
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We synthesized two series of diphenyl-diacetylene (DPDA)-based materials with alkoxy and alkyl tails of length m (DPDA-OCm and DPDA-Cm, respectively), and measured their nematic-phase birefringence (Δn) as a function of wavelength and temperature. We found that Δn decreases with an increase in m, possibly by a dilution effect of the low-Δn alkyl tail. Further, of the two series, Δn was found to be relatively higher in the DPDA-OCm materials, with the highest value of 0.4 obtained for DPDA-OC1 at 550 nm at 10 °C below the isotropic-to-nematic transition temperature. Further, we observed the temperature dependence for Δn, which is proportional to the order parameter (s). From extrapolation to s = 1 (the perfect orientation state), it is speculated that the DPDA-O moiety has the potential to afford a very large Δn of 0.9. The Royal Society of Chemistry 2012.
- Arakawa, Yuki,Nakajima, Shunpei,Ishige, Ryohei,Uchimura, Makoto,Kang, Sungmin,Konishi, Gen-Ichi,Watanabe, Junji
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p. 8394 - 8398
(2012/07/28)
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- Buchwald protocol applied to the synthesis of N-heterotolan liquid crystals
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A homologous series of the new N-heterotolans 8a-d were synthesized using two cross-coupling reactions mediated by copper and palladium/copper. The final compounds present the phenyl-pyridyl framework connected by the acetylene group. The evaluation of th
- Vasconcelos, Ursula B.,Schrader, Abel,Vilela, Guilherme D.,Borges, Antonio C.A.,Merlo, Aloir A.
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p. 4619 - 4626
(2008/09/20)
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- Synthesis and mesomorphic properties of some fluorinated benzoate liquid crystals
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Three series of [4-(4′-n-alkyloxyphenyl)acetylenyl]-2,6- difluorophenyl fluorinated benezoates and one series of fluorinated benzoates with 2,3,5,6-tetrafluorophenylene group and semi-perfluorocarbon chain have been synthesized. Their phase transition temperatures have been measured by texture observation in a polarizing microscope and confirmed by DSC. For the series without fluorocarbon chains, increasing the quantity of fluorosubstituents on the terminal phenyl groups decreased nematic stability (TN-I), but the breadth of the SmA phase range was increased. Lateral fluorosubstitution in the central group lowered the nematic stability (TN-I) and decreased the breadth of the SmA phase range. The series with semiperfluorocarbon chains were more likely to form SmA phases than the series with hydrogencarbon chains, and with the increasing of fluorosubstituents quantity on the terminal phenyl groups nematic and SmA stability (TN-I and TsmA-N) were both decreased.
- Yang, Yong Gang,Chen,Tang,Wen
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- Synthesis and mesomorphic properties of some fluoro-substituted benzoates
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Several series of fluoro-substituted benzoate liquid crystals have been synthesized. The results showed that the SmA phase is enhanced with the increasing of the degree of fluoro-substitution on the para- and meta-position of the terminal phenyl groups. And the molecules which have same molecular structural formula show nearly the same melting points. It is also discussed about the effect of the ester bond's direction on the mesomorphic properties.
- Yang,Tang,Gong,Wen
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p. 153 - 165
(2007/10/03)
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