Self‐organizing n‐type hexaazatrinaphthylenes (HATNAs) with various bay‐located side chains have been synthesized. The HATNA derivatives are able to form long‐range molecular columns with self‐directed growth directions. In particular, alkyl‐substituted HATNAs showed in‐plane molecular columns with axes parallel to substrates, whereas the columnar orientation of the HATNAs with alkylethynyl or alkylthio groups strongly depended on the length of the introduced side chains. Interestingly, the derivative with octylthio chains exhibited out‐of‐plane molecular columns, in which electron mobility of up to 10?3 cm2 V?1 s?1 was determined through the time‐of‐flight technique, highlighting the fact that such molecular columns based on bay‐substituted HATNAs are promising n‐type semiconductors for device applications. 相似文献
Columnar liquid‐crystalline (LC) truxene derivatives containing branched flexible alkyl chains have been designed and synthesized. The dicyanomethylene and dithiafulvene substituents have been introduced into the π‐conjugated truxene framework to tune their electronic and redox properties as well as the molecular assembled structures. The π‐conjugated cores of dicyanomethylene‐ and dithiafulvene‐appended truxenes adopt bowl‐shaped conformations, giving rise to a large intrinsic dipole moment perpendicular to the aromatic framework. These molecules form stable columnar LC structures through intermolecular dipole–dipole interactions. The redox properties of LC truxene derivatives have been examined by cyclic voltammetry. The dicyanomethylene‐appended truxene shows the reversible four‐step electrochemical reductions, whereas the dithiafulvene‐appended truxene undergoes three‐step oxidations. 相似文献
By using aryl‐amination chemistry, a series of rodlike 1‐phenyl‐1H‐imidazole‐based liquid crystals (LCs) and related imidazolium‐based ionic liquid crystals (ILCs) has been prepared. The number and length of the C‐terminal chains (at the noncharged end of the rodlike core) and the length of the N‐terminal chain (on the imidazolium unit in the ILCs) were modified and the influence of these structural parameters on the mode of self‐assembly in LC phases was investigated by polarizing microscopy, differential scanning calorimetry, and X‐ray diffraction. For the single‐chain imidazole derivatives nematic phases (N) and bilayer SmA2 phases were found, but upon increasing the number of alkyl chains the LC phases were lost. For the related imidazolium salts LC phases were preserved upon increasing the number and length of the C‐terminal chains and in this series it leads to the phase sequence SmA–columnar (Col)–micellar cubic (CubI/Pm3n). Elongation of the N‐terminal chain gives the reversed sequence. Short N‐terminal chains prefer an end‐to‐end packing of the mesogens in which these chains are separated from the C‐terminal chains. Elongation of the N‐terminal chain leads to a mixing of N‐ and C‐terminal chains, which is accompanied by complete intercalation of the aromatic cores. In the smectic phases this gives rise to a transition from bilayer (SmA2) to monolayer smectic (SmA) phases. For the columnar and cubic phases the segregated end‐to‐end packing leads to core–shell aggregates. In this case, elongation of the N‐terminal chains distorts core–shell formation and removes CubI and Col phases in favor of single‐layer SmA phases. Hence, by tailoring the length of the N‐terminal chain, a crossover from taper‐shaped to polycatenar LC tectons was achieved, which provides a powerful tool for control of self‐assembly in ILCs. 相似文献
We have designed and synthesised a series of modular, mesogenic complexes based on anthracene‐2,6‐disulfonate and trialkoxybenzyl‐functionalised imidazolium cations. Each complex contains a central, rigid, dianionic anthracene core and two flexible monocations bearing paraffin chains anchored on imidazolium rings. Anthracene‐2,6‐disulfonate can be crystallised with various simple alkylammonium ions and, in the case of +N(CH3)2(C16H33)2, a crystal structure determination has shown that the long paraffinic chains are intercalated between the anthracene moieties. The dianion forms columnar mesophases with trialkoxybenzylimidazolium cations, as identified by polarising optical microscopy and X‐ray scattering measurements. Differential scanning calorimetry studies confirmed mesomorphic behaviour from room temperature to about 200 °C for alkyl chains containing 8, 12 and 16 carbon atoms. The strong luminescence of anthracene is maintained in the mesophase and fluorescence measurements confirmed the presence of J aggregates in all cases. The new functional materials described herein provide an easy access to stable and luminescent mesomorphic materials engineered by an ionic self‐assembly process. 相似文献
A series of modular mesogenic salts based on the combination of anionic 4,4‐difluoro‐4‐bora‐3a,4a‐diaza‐s‐indacene (F‐BODIPY) 2,6‐disulfonate dyes and trialkoxybenzyl‐functionalised imidazolium cations has been designed and synthesised. Each salt contains a rigid dianionic BODIPY core associated with two imidazolium cations functionalised by 1,2,3‐trialkoxybenzyl (alkyl=n‐C8, n‐C12 or n‐C16) units or, in one case, with imidazolium cations functionalised by a trialkylgallate (3,4,5‐trialkoxybenzoate) unit in which the 3,5‐dialkyl groups are terminated with a polymerisable acrylate entity. All these compounds were highly fluorescent in solution with quantum yields ranging from 54 to 62 %. In the solid state, the width of the emission band observed at around 650 nm is a clear signature of aggregation. With the trialkoxybenzylimidazolium cations, polarised optical microscopy (POM) and X‐ray scattering experiments showed that columnar mesophases were formed. Differential scanning calorimetry (DSC) studies confirmed the mesomorphic behaviour from room temperature to about 130 °C for salts with alkyl chains containing 8, 12 and 16 carbon atoms. The strong luminescence of the BODIPY unit was maintained in the mesophase and fluorescence measurements confirmed the presence of J aggregates in all cases. The salt containing the gallate‐functionalised imidazolium cations showed no mesomorphism but the acrylate terminal units could be used to engender photoinitiated polymerisation thereby allowing the material to be immobilised on glass plates. The polymerisation process was followed by FTIR spectroscopy and the fixed and patterned films were highly fluorescent with a solid‐state emission close to that of the complex in the solid state. 相似文献
Herein, we report for the first time that nematic liquid‐crystalline environments drive the reversible self‐aggregation of an enantiopure β‐pentapeptide into oligomers with a well‐defined structure. The peptide contains four (1S,2S)‐2‐aminocyclopentane carboxylic acid (ACPC) residues and the paramagnetic β‐amino acid (3R,4R)‐4‐amino‐1‐oxyl‐2,2,5,5‐tetramethylpyrrolidine‐3‐carboxylic acid (POAC). The structure of the oligomers was investigated by electron paramagnetic resonance (EPR) spectroscopy, which allowed us to obtain the intermonomer distance distribution in the aggregates as a function of peptide concentration in two nematic liquid crystals, E7 and ZLI‐4792. The aggregates were modeled on the basis of the EPR data, and their orientation and order in the nematic phase were studied by the surface tensor method. 相似文献
A star‐shaped tris(triazolyl)triazine is shown to establish hydrogen‐bond interactions with polycatenar benzoic acids. The formation of hydrogen‐bonded triazine/acid complexes has been demonstrated both in solution and in bulk by different techniques. The complexes, mainly formed by nonmesogenic components, all show enantiotropic hexagonal columnar mesomorphism, which relies on the formation of hydrogen‐bond complexes in a triazine/acid ratio of 1:3. This approach combines the straightforward synthesis of a nonmesomorphic triazine core by click chemistry, and the preparation of a supramolecular complex, providing a much more convenient route than covalent synthesis to modify the periphery of triazine discotics and thus to modulate their functionality. 相似文献
Fullerene‐based liquid crystalline materials have both the excellent optical and electrical properties of fullerene and the self‐organization and external‐field‐responsive properties of liquid crystals (LCs). Herein, we demonstrate a new family of thermotropic [60]fullerene supramolecular LCs with hierarchical structures. The [60]fullerene dyads undergo self‐organization driven by π–π interactions to form triple‐layer two‐dimensional (2D) fullerene crystals sandwiched between layers of alkyl chains. The lamellar packing of 2D crystals gives rise to the formation of supramolecular LCs. This design strategy should be applicable to other molecules and lead to an enlarged family of 2D crystals and supramolecular liquid crystals. 相似文献
We have synthesized a series of triarylamine‐cored molecules equipped with an adjacent amide moiety and dendritic peripheral tails in a variety of modes. We show by 1H NMR and UV/Vis spectroscopy that their supramolecular self‐assembly can be promoted in solution upon light stimulation and radical initiation. In addition, we have probed their molecular arrangements and mesomorphic properties in the bulk by integrated studies on their film state by using differential scanning calorimetry (DSC), variable‐temperature polarizing optical microscopy (VT‐POM), variable‐temperature X‐ray diffraction (VT‐XRD), and atomic force microscopy (AFM). Differences in the number and the disposition of the peripheral tails significantly affect their mesomorphic properties associated with their lamellar‐ or columnar‐packed nanostructures, which are based on segregated stacks of the triphenylamine cores and the lipophilic/lipophobic periphery. Such structural tuning is of interest for implementation of these soft self‐assemblies as electroactive materials from solution to mesophases. 相似文献
Polymerizable vinylimidazolium ionic liquids (ILs) that contain mesogenic coumarin and biphenyl units, respectively, have been synthesized. The N‐alkylation of N‐vinylimidazole with bromoalkylated mesogenic units 7‐(6‐bromohexyloxy)coumarin ( 1 ) and 4,4′‐bis(6‐bromohexyloxy)biphenyl ( 2 ) was then carried out. The thermal behavior of the obtained ILs 3 and 4 was investigated by differential scanning calorimetry and polarizing optical microscopy. These measurements showed that the attached mesogenic units induce the self‐assembly of ILs and, therefore, the occurrence of liquid crystalline phases. Subsequently, the ionic liquid crystals (ILCs) 3 and 4 were polymerized by a free‐radical mechanism.
A series of ionic associates based on the platinum(II) chelate of 5‐sulfo‐8‐quinolinol, [Pt(qS)2]2?, and ammonium‐based amphiphiles is described. At variance with the prototypical neutral complex Pt(q)2 (q=8‐quinolinol), these dianionic fluorophores, functionalized at the periphery with sulfonate groups, can be associated by the ionic self‐assembly approach with various ammonium cations, such as (H2 n+1Cn)2Me2N+ (n=12, 16, 18) or complex ammonium cations carrying three Cn carbon chains (n=12, 14, 16) and an additional amide group. Investigations of their luminescence properties in solution, in the solid state, and, when possible, in thin films revealed that the phosphorescence properties in condensed phases are directly correlated to intermolecular interactions between the luminescent [Pt(qS)2]2? centers. Of particular interest is also the formation of a columnar liquid‐crystalline phase around room temperature (between ?25 and +180 °C), as well as the very good film‐forming ability of some of these fluorophores from organic solvents. 相似文献
Surface‐supported liquid crystals (LCs) that exhibit orientational and thus optical responses upon exposure to ppb concentrations of Cl2 gas are reported. Computations identified Mn cations as candidate surface binding sites that undergo redox‐triggered changes in the strength of binding to nitrogen‐based LCs upon exposure to Cl2 gas. Guided by these predictions, μm‐thick films of nitrile‐ or pyridine‐containing LCs were prepared on surfaces decorated with Mn2+ binding sites as perchlorate salts. Following exposure to Cl2, formation of Mn4+ (in the form of MnO2 microparticles) was confirmed and an accompanying change in the orientation and optical appearance of the supported LC films was measured. In unoptimized systems, the LC orientational transitions provided the sensitivity and response times needed for monitoring human exposure to Cl2 gas. The response was also selective to Cl2 over other oxidizing agents such as air or NO2 and other chemical targets such as organophosphonates. 相似文献
A divergent approach was used for the synthesis of dendritic structures based on a cyclotriphosphazene core with 12 or 24 hydroxyl groups, by starting from [N3P3(OC6H4OH‐4)6] and using an acetal‐protected 2,2‐di(hydroxymethyl)propionic anhydride as the acylating agent. Hydroxyl groups in these first‐ and second‐generation dendrimers, G1‐(OH)12 or G2‐(OH)24 , were then condensed in turn with mono‐ or polycatenar pro‐mesogenic acids to study their ability to promote self‐assembly into liquid crystalline structures. Reactions were monitored by using 31P{1H} and 1H NMR spectroscopy and the chemical structure of the resulting materials was confirmed by using different spectroscopic techniques and mass spectrometry (MALDI‐TOF MS). The results were in accordance with monodisperse, fully functionalised cyclotriphosphazene dendrimers. Thermal and liquid crystalline properties were studied by using optical microscopy, differential scanning calorimetry and X‐ray diffraction. The dendrimer with 12 4‐pentylbiphenyl mesogenic units gives rise to columnar rectangular organisation, whereas the one with 24 pentylbiphenyl units does not exhibit mesomorphic behaviour. In the case of materials that contain polycatenar pro‐mesogenic units with two aromatic rings ( A4 vs. A5 ), the incorporation of a short flexible spacer connected to the periphery of the dendron (acid A5 ) was needed to achieve mesomorphic organisation. In this case, both dendrimer generations G1 A5 and G2 A5 exhibit a hexagonal columnar mesophase. 相似文献
Three truxene derivatives functionalized with alkyl chains, either attached directly or distanced by linking phenyl or ethynyl groups, self‐assemble in solution and induce the gelation of different solvents in spite of not being endowed with groups able to establish strong directional interactions. A 1H NMR study points to face‐to‐face alternating π‐stacked motifs at the origin of nucleation. Solvents play an important role in modulating the aggregation of these derivatives giving rise to fibrous or spherical superstructures. Analysis of the influence of different solvents on the morphology of the aggregates provides a better understanding of the various stages of the hierarchical self‐assembly. The way in which alkyl chains are attached to the central core also strongly affects the self‐assembling properties and gelation ability of this series. Phenyl spacers present the highest association constants in solution and give rise to gelation in a broader range of solvents. This behavior has been rationalized by means of 1H NMR spectroscopy, X‐ray powder diffraction, SEM, and photophysical measurements. Interestingly, it was found that these compounds in the gel state exhibit unusual emission properties most likely arising from the formation of excimers, which evidences that π–π interactions also occur in the excited state. 相似文献