Synthesis and mesomorphism of diacetylene-bridged triphenylene discotic liquid crystal dimers

Connecting two discotic mesogens via a spacer not only stabilizes the columnar mesophase but also leads to the formation of glass columnar phase, and therefore improves the physical properties of discotic liquid crystals as organic semiconductor. Here, we report the synthesis of eight diacetylene-bridged triphenylene discotic liquid crystal dimers, [C18H6(OCnH2n+1)4(OMe)O2C-C8H16-C≡≡ C-]2, 3(n), (n = 4-8), [C18H6(OC6H13)5O2C-C8H16-C≡≡ C-]2, 6 and [C18H6(OC6H13)5O-(CH2)m-C≡≡ C-]2, 8(m), (m = 1, 3) by Eglinto...     

含有长烷氧链混合醚-酯类苯并菲盘状液晶的合成及其介晶性研究

本文合成了含有不同柔链的对称和非对称苯并菲盘状液晶:sym-C18H6(OC11H23)3(O2CR)3和asym-C18H6(OC11H23)3(O2CR)3,R=(CH2OC2H5),CH2OC3H7,CH2OC4H9,CH2OC5H11,C3H7,C4H9,C5H11,C6H13,C7H15。通过偏光显微镜(POM)和差视扫描量热法(DSC)对它们的热致液晶性性进行了研究,结果显示:非对称性化合物比它们相应的对称性化合物有更高的熔点和清亮点。对于同一系列的化合物G18H6(OC11H23)3(OOCR)3,随取代基R的增长,其熔点下降,清高点反而升高。无论对称和非对称苯并菲衍生物G18H6(OC11H23)3(O2CR)3,(R=CH2OC2H5,CH2OC3H7,CH2OC4H9,CH2OC5H11),与有同样软链长度的苯并菲衍生物G18H6(OC11H23)3(O2CR)3,(R=C4H9,CK5H11,C6H13,C7H15)相比较,大都有更高的熔点和清亮点。另外,有足够长度软链的苯并菲衍生物在室温下就显示介晶相。     

含有长烷氧链混合醚一酯类苯并菲盘状液晶的合成及其介晶性研究

本文合成了含有不同柔链的对称和非对称苯并菲盘状液晶：sym-C18H6（OC11H23），（02CR）3和nsym-C18H6（OCIIH23）3（02CR）3，R=（CH20C2H5），CH20C3H7，CH20C4H9，CH20C5H11,C3H7，C4H9，C5Hll,C6H13，C7H15。通过偏光显微镜（POM）和差视扫描量热法（DSC）对它们的热致液晶性性进行了研究，结果显示：非对称性化合物比它们相应的对称性化合物有更高的熔点和清亮点。对于同一系列的化合物G18H6（OC11H23），（OOCR）3随取代基R的增长，其熔点下降，清高点反而升高。无论对称和非对称苯并菲衍生物G18H6（OC18H23）3（02CR）3，（R=CH20C2H5，CH20C3H7，CH20C4H9，CH20C5H11），与有同样软链长度的苯并菲衍生物G18H5（OC11H23）3（O2CR）3，（R=C4H9，CK5H11,C6H13C，H15）相比较，大都有更高的熔点和清亮点。另外，有足够长度软链的苯并菲衍生物在室温下就显示介晶相。     

Synthesis and mesomorphism of mixed ether-ester tail triphenylene discotic liquid crystals with long alkyloxy peripheral chains

Symmetrical and asymmetrical triphenylene discotic liquid crystals with two kinds of different peripheral chains, sym-TP(OC₁₁H₂₃)₃(O₂CR)₃ and asym-TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁, C₃H₇, C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅) were synthesized. Their thermotropic liquid crystalline properties were studied by polarizing optical microscopy (POM) and differential scanning calorimetry (DSC). The results showed that the asymmetrical compounds had higher melting and clearing points than that of their corresponding symmetrical compounds. For the same series of compounds, TP(OC₁₁H₂₃)₃(O₂CR)₃, their melting points decrease and clearing points increase gradually with the lengthening of ester chains. Most of the β-oxygen containing esters of triphenylene derivatives, TP (OC₁₁H₂₃)₃(O₂CR)₃, (R=CH₂OC₂H₅, CH₂OC₃H₇, CH₂OC₄H₉, CH₂OC₅H₁₁), symmetrically or asymmetrically attached on triphenylene cores, have higher melting and clearing points than those of triphenylene derivatives, TP(OC₁₁H₂₃)₃(O₂CR)₃, (R=C₄H₉, C₅H₁₁, C₆H₁₃, C₇H₁₅), with the same length of peripheral chains. The triphenylene derivatives with longer peripheral chains have shown mesophase at room temperature. __________ Translated from Chemical Research and Application, 2007, 19(10) (in Chinese)     

官能化苯并菲盘状液晶的合成及不饱柔链对介晶性的影响

合成了12个含不饱和软链的苯并菲盘状液晶化合物,C18H6（OC5H11）6-x（OR）x（x=1,2,3）,R=-C3H6CH=CH2（a）,-C3H6C≡CH（b）,-C2H4OCH=CH2（c）.化合物结构通过核磁共振氢谱和高分辨质谱表征.化合物热致液晶性通过偏光显微镜（POM）,差视扫描热量法（DSC）,和X射线衍射（XRD）进行了研究.结果显示目标化合物呈现有序的六方柱状介晶相.端炔基链化合物b系列熔点最高.乙烯氧基柔链化合物c系列有最高的清亮点和最宽的介晶性温度范围,且随着不饱和醚链数的增多,清亮点明显升高.对称苯并菲化合物sym-C18H6（OC5H11）3（OR）3比不对称化合物asym-C18H6（OC5H11）3（OR）3具有更高的熔点和清亮点.乙烯氧基柔链可极化的偶极相互作用对液晶稳定性有较大贡献.     

Drastic enhancement of discotic mesomorphism induced by fluorination of the peripheral phenyl groups in triphenylene mesogens

Four derivatives of hexakis(4-alkoxybenzoyloxy)triphenylene, for which peripheral phenylene groups are fluorinated at the inner and the outer positions were studied for their mesomorphic behaviour to reveal that the alteration of fluorinated positions in the phenyl rings leads to a drastic change of the mesomorphism involving the thermal stability.     

Synthesis,complexation, and mesomorphism of novel calixarene-linked discotic triphenylene based on click chemistry

The novel calixarene-linked discotic triphenylene 5a and 5b were synthesized in good yields via click chemistry. Structural and conformational characterization of new compounds had been achieved by NMR, MS, and elemental analysis. Their liquid crystalline behaviors before and after complexation were studied by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction. The neat compounds 5a and 5b showed mesophase but the complexes of 5a and 5b with metallic salts exhibited no liquid crystal behaviors.     

Molecular parameters and mesomorphism of discotic polysubstituted benzene derivatives

The previously developed approach to prediction of columnar and nematic mesophases for compounds with disc-shaped molecules was applied to low-molecular-weight polysubstituted benzene derivatives. The molecular parameters were calculated for 39 new compounds: derivatives of 1,3,5-tri(4-hydroxybenzoyloxy)benzene, 1,3,5-tri(4-cyclohexylbenzoyloxy)benzene, 1,3,5-tri(4-hydroxyphenylcarboxy)benzene, 1,2,3-tri(4-cyclohexylbenzoyloxy)benzene, etc. The prediction results were checked by the synthesis of certain compounds from the test sample and examination of their mesomorphic behavior. The prediction of the mesomorphism is negative for only three of the 39 compounds considered. The majority of the molecules under consideration tend to form columnar supramolecular packings, and the capability to form a nematic phase is predicted for only eight compounds. For a number of structures, the capability and incapability to form a nematic phase are equally probable. Synthesis and examination of the mesomorphic behavior of seven repesentatives of the series considered showed good agreement with the prediction results. 1,3,5-Tri(4-heptyloxybenzoyloxy)benzene, 1,3,5-tri(4-cyclohexylbenzoyloxy)benzene, 1,3,5-tri(4-nonyloxyphenylcarboxy)-benzene, and 1,2,3-tri(4-cyclohexylbenzoyloxy)benzene pass into the liquid crystal state forming mainly columnar supramolecular packings. 1,3,5-Tri(4-octyloxybenzoyloxy)benzene and 1,3,5-tri(4-nonyloxybenzoyloxy)benzene melt at 55 and 48°C, respectively, without forming a mesophase, which is also well consistent with the prediction results.     

Synthesis and study of heptasubstituted triphenylenes with chiral fragments and predictable type of mesomorphism

The forecasting of columnar and chiral mesomorphism was done for the new series of triphenylene derivatives. The mesomorphic properties of the two heptasubstituted triphenylenes containing chiral fragments were studied. The prediction results agreed well with the experimental data. Anilides of 1-amino-2,3,6,7,10,11-hexa(heptyloxy)triphenylene with abietic and dihydrocholic acids were found to exhibit the enantiotropic columnar dimesomorphism and to display the chiral columnar mesophases in the low-temperature range. The anilides obtained possess a lower thermal stability and extended interval of the mesophase existence than the initial amine.     

Synthesis and characterization of naphthalene-substituted triphenylene discotic liquid crystals

A series of naphthalene-substituted triphenylene liquid crystals (LCs), viz. triphenylene-2,3,6,7,10,11-hexayl hexakis(6-alkenyloxy-2-naphthoate)s (HTPnN compounds) were synthesized and characterized. Alkenyloxy groups containing three to eleven carbon atoms were used as peripheral spacers in these liquid crystals. The discotic liquid crystals synthesized trap one to three water molecules depending on the length of their peripheral spacers. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction measurements confirm both nematic (N_d) and rectangular disordered columnar (Col_rd) phases for most of the synthesized discotic LCs. The clearing temperatures of these discotic LCs increase with increasing peripheral spacer length. A hybrid aligned HTP9N sample was investigated to evaluate its optical performance. Retardation values of this hybrid sample decrease with increasing wavelength and increase with increasing measuring angle.     

Novel NLO-phores with proaromatic donor and acceptor groups

[reaction: see text] Novel D-pi-A NLO-phores based on the 1,3-dithiol-2-ylidene donor and the thiobarbituric acceptor moieties have been prepared. Modification of the length and rigidity of the pi-spacer allows the first systematic study of the second-order nonlinear optical properties of doubly proaromatic merocyanines. The pi-electron donor efficiency of the 1,3-dithiol-2-ylidene group is superior to that of the tetrathiafulvalenyl group.     

Synthesis and characterization of novel imidazolium-based ionic discotic liquid crystals with a triphenylene moiety

Two novel triphenylene-tethered imidazolium salts were synthesized either by the quaternization of 1-methylimidazole with an ω-bromo-substituted triphenylene or by the quaternization of a triphenylene-substituted imidazole with methyl iodide. Their chemical structures were determined by ¹H NMR, ¹³C NMR, IR, UV spectroscopy and elemental analysis. The thermotropic liquid crystalline properties of these salts were investigated by polarizing optical microscopy and differential scanning calorimetry. These triphenylene-based imidazolium salts with bromide or iodide as counterion show columnar mesophase properties over a wide temperature range.     

Molecular structure and mesomorphism in the series of discotic esters derived from benzene,triazine, biphenyl,and triphenylene

New mesogenic discotic triazine-based esters were synthesized and shown to form a low-temperature monotropic columnar mesophase. Using as examples the newly synthesized compounds and previously prepared discotic esters on the basis of benzene, biphenyl, and triphenylene, the effects of the nature and size of the central fragment and the number, position, length, and rigidity of peripheral substituents therein on the mesomorphic properties (in particular, the ability to form columnar and nematic mesophases) were examined. The main structural factors stabilizing columnar and nematic mesophases were revealed. Nematic mesomorphism was shown to be favored by increased size of the central fragment of the discogen molecule and by the presence of cyclohexane fragments in peripheral substituents.     

Zwitterion from a cyclopropane with geminal donor and acceptor groups

2,2-Dimethoxy-3,3-dicyanospiro[cyclopropane-1,9'-[9H]fluorene] reacted fast with methanol to afford 9-trimethoxymethyl-9-dicyanomethyl-9H-fluorene. Reaction with benzaldehydes also gave products of cyclopropane ring opening. Strong electron-donor p-substituents or a strong attractor enhanced the rate. Ring opening of the cyclopropane to a zwitterion that recloses or reacts with an aryl aldehyde, to form either a CO or a CC bond first, can explain the result. The former mode of closure is sensitive to p-substituents because they are directly conjugated to the positive charge at the benzylic carbon of the former aldehyde. The latter mode is sensitive to the ground-state electrophilicity of the carbonyl carbon of the former aldehyde. Thus, reaction of the cyclopropane with p-substituted aldehydes is accelerated by either electron-donor or -acceptor substituents. [reaction: see text].     

Synthesis,structure, and discotic mesomorphism of the new series of copper carboxylates

The synthesis, structure, and mesomorphism of a new series of copper carboxylates are described. The influence of periphery of the chelate node on the appearance of discophase is studied. A stacked hexagonal structure of copper erucate is proved. The effect of restructuring of the chelate node in this compound after its isothermic exposure, causing the loss of mesomorphism is revealed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1256–1260, July, 1995.     

Synthesis and mesomorphism of 1,3-benzenedicarboxylic acid derivatives

4-Methoxy-l,3-benzenedicarboxylic acid esters and 4-(4-hexyloxybenzoylamino)phenyl 1,3-benzenedicarboxylate, each containing five aromatic rings, were synthesized. The influence of the structure of the synthesized banana-like compounds on their mesogenic activity was examined.     

Synthesis of ferrocene derivatives exhibiting low-temperature mesomorphism

Novel ferrocenomesogens exhibiting low-temperature mesomorphism have been synthesised from 4-ferrocenylphenol and n-alkoxy naphthoic acid intermediates (n = 4 to 16). The phase behaviour has been investigated in detail by polarising optical microscopy and differential scanning calorimetry.     

Synthesis,structure, photophysical,and electrochemical properties of donor–acceptor ferrocenyl derivatives

A series of donor–acceptor compounds 2–6 have been synthesized, via Knoevenagel condensation reaction (using conventional method, as well as microwave method). The ferrocene unit acts as a donor, conjugated phenyl–acetylene linker act as a π-electron relay unit, and malononitrile, cyanoacetic acid, and indanone groups act as acceptor. The electronic absorption spectra displayed a broad intramolecular charge transfer (CT) band in the visible region (450–650 nm). The electrochemical studies suggest considerable donor–acceptor interaction. The single crystal X-ray structure of 2, and 3 are reported, the structure reveals that 2 is nearly planar compared to 3. The supramolecular structure of 2 exhibits intramolecular C–H–π, and C–H–N interaction, which leads to formation of 2D network, whereas compound 3 shows head to tail dimer formation through C–H–π, and π–π interaction.     

含氟链不对称苯并菲盘状液晶的合成及疏氟效应对介晶性的影响

盘状液晶分子中引入氟代烃链并利用疏氟效应（fluorophobic effect）能有效稳定分子的柱状堆积;低对称性的盘状分子有较低的熔点和宽的介晶相温度范围．基于此,本文设计并合成了一系列半氟酯链的不对称苯并菲化合物C18H6（OCnH2n＋1）4（OCH3）（O2CC2H4C6F13）（1）,及相对应的不含氟化合物C18H6（OCnH2n＋1）4（OCH3）（O2CC8H17）（2）,n=4—8．化合物结构通过核磁和质谱表征．介晶性通过差示扫描量热法和偏光显微镜进行了研究．结果显示：化合物均为柱状互变热致液晶．含氟链化合物1a—1e与相对应的化合物2a-2e比较,有更高的熔点和清亮点．合成的多数化合物为室温液晶．