- Effects of substitution and terminal groups for liquid-crystallinity enhanced luminescence of disubstituted polyacetylenes carrying chromophoric terphenyl pendants
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Liquid-crystalline and light-emitting poly(2-alkyne)s containing terphenyl cores with hexamethyleneoxy spacers, and cyano or n-propoxy tails - [CH3C=C(CH2)6O-terphenyl-R] n -, where R=CN, CH3PA6CN, R=OCH2CH 2CH3, CH3PA6OPr, were synthesized. The effects of the substitution and terminal groups on the properties, especially the mesomorphic and optical properties of the polymers, were investigated. The disubstituted acetylene monomers (CH3A6CN, CH3A6OPr) were prepared through multistep reaction routes and were polymerized by WCl6-Ph4Sn in good yields (up to 82%). All the monomers and CH3PA6CN exhibited the enantiotropic SmA phase with a monolayer arrangement at elevated temperatures, whereas CH3PA6OPr formed a bilayer SmAd packing arrangement. Upon excitation at 330 nm, strong UV and blue emission peaks at 362 and 411 nm were observed in CH3PA6OPr and CH3PA6CN, respectively. The luminescent properties of CH3PA6CN and CH3PA6OPr have been improved by introducing the methyl substituted group, and the quantum yield of the polymer with cyano tail CH3PA6CN (Φ = 74%) was found to be higher than that of CH3PA6OPr (Φ = 60%). Compared to polyacetylene parents, both CH3PA6OPr and CH3PA6CN showed a narrower energy gap. This demonstrated that the electrical conductivities of polyacetylenes could be enhanced by attaching appropriate pendants to the conjugated polyene backbones.
- Zhou, Dan,Chen, Yiwang,Chen, Lie,Li, Fan,Nie, Huarong,Yao, Kai
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experimental part
p. 1302 - 1315
(2010/11/05)
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- Suzuki-Miyaura reaction of chloroarenes using Pd(PPh3) 4 as catalyst
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The reactivity of a number of chloroarenes was investigated and chloro-nitroarenes were found to undergo facile arylation with Pd(PPh 3)4 / [Pd(PPh3)2Cl 2/n.PPh3] as catalyst. Furthermore, 4-chlorobenzaldehyde underwent arylation under the conditions, albeit with a higher catalyst loading.
- Thiemann, Thies,Tanaka, Yasuko,Hisaindee, Soleiman,Kaabi, Maitha
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experimental part
p. 34 - 38
(2010/06/16)
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- Brominated thiophenes as precursors in the preparation of brominated and arylated anthraquinones
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Brominated anthraquinones can be synthesized directly from bromothiophenes when these are reacted with 1,4-naphthoquinones in the presence of meta-chloroperoxybenzoic acid. The bromoanthraquinones are versatile building blocks in the preparation of arylated anthraquinones and of extended π-systems with interspersed anthraquinone units.
- Thiemann, Thies,Tanaka, Yasuko,Iniesta, Jesus
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experimental part
p. 1013 - 1031
(2009/10/10)
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- Synthesis and Properties of Liquid Crystalline 4,4 -Dialkoxy-2'-Methyl-p-Terphenyls
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A new series of laterally substituted terphenyl compounds, 4,4 -dialkoxy-2'-methyl-p-terphenyls (n = 1-12), were synthesized. Their liquid crystallinities were characterized by means of polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray difraction (XRD). The influence of the length of the terminal alkoxy groups on the liquid crystalline behavior was investigated. It was found that the compounds with shorter end chains (n a smectic A mesophase is exhibited for those with longer end chains (9 = n = 12).
- Yu, Z. N.,Tu, H. L.,Wan, X. H.,Chen, X. F.,Zhou, Q. F.
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- Toward boronate ester mesogenic structures
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This article describes efforts toward the development of a new core for calamitic mesogens based upon the introduction of an extended heteroaromatic boroncontaining ring. A series of tri-catenar mesogenic boronate ester derivatives of the 2-phenyl-1,3,2-benzodioxaborole has been synthesized and characterized. The flat central core appeared to be a suitable feature for these derivatives to support anisotropic alignment. Additionally, these derivatives should possess an inherent dipole in the core. However, thermal analysis (polarized optical microscopy and differential scanning calorimetry) did not reveal any mesophases.
- Belloni, Maura,Manickam,Wang, Zehn-He,Preece, Jon A.
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- The X-ray crystal structures and computational analysis of NH...π hydrogen bonded banana-shaped carbazole derivatives and thermal analysis of higher mesogenic homologues
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The synthesis of a series of banana-shaped mesogenic structures has been carried out, in which the bend unit is formed by the 3,6-substitution of carbazole by 4-alkoxyphenyl moieties. The crystal structures of the methoxy and propyloxy derivatives are reported with an analysis of the N-H...π interactions that are observed in the crystalline state. This analysis was aided by semi-empirical molecular orbital calculations. Additionally, the thermal analysis of the complete series has been carried out in order to investigate the phase properties of these materials. The 4-nonyloxyphenyl derivative displays two melting points by DSC and normal light microscopy, but yields non-birefringent liquids. The incorporation of photorefractive molecular units, such as carbazole. into anisotropic materials may offer many advantages over conventional electrical poling of photorefractive polymers.
- Belloni, Maura,Manickam,Ashton, Peter R.,Kariuki, Benson M.,Preece, Jon A.,Spencer, Neil,Wilkie, John
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