A new series of shape‐persistent imine‐bridged macrocycles were synthesized based on dynamic covalent chemistry. The macrocycles had an alternating sequence of dibenzothiophene and N,N′‐bis(salicylidene)‐ethylenediamine (salen) tethering branched alkyl chains. The macrocycles and tetranuclear metallomacrocycles bearing long and branched alkyl chains exhibited thermotropic columnar liquid‐crystalline phases over a wide temperature range and the metallomacrocycles greatly depended on the characteristics of the coordinated metal ions. The metal‐free macrocycle showed a liquid‐crystalline phase with a lamellar structure and poor birefringence. In sharp contrast, the macrocyclic Ni complex showed a columnar oblique liquid‐crystalline phase, whereas the Pd and Cu complexes showed columnar liquid‐crystalline phases with a lamellar structure. The macroscopic organization and thermal properties of the corresponding liquid‐crystalline metallomacrocycles were significantly dependent on the subtle structural differences among the planar macrocycles, which were revealed by single‐crystal X‐ray crystallographic analysis of the macrocycles with shorter alkyl chains. 相似文献
Anisotropic physical gels of liquid crystals are obtained by the formation of non‐covalently‐bonded networks through self‐organization of low molecular weight compounds in nematic solvents. They exhibit thermoreversible transitions between isotropic liquid and isotropic gel, and between isotropic gel and liquid‐crystalline gel, whose temperatures are dependent on the components. Electro‐optic properties of liquid‐crystalline gels are examined with twisted nematic cells. A nematic liquid crystal in a gel structure can respond to electric fields twice faster than a single liquid‐crystalline component. 相似文献
A series of unsymmetrical naphthalene imide derivatives ( 1a , 1b , 2 , 3 , 4 , 5 ) with high electron affinity was synthesized and used in n‐channel organic field‐effect transistors (OFETs). They have very good solubility in common organic solvents and good thermal stability up to 320 °C. Their photophysical, electrochemical, and thermal properties were investigated in detail. They showed low‐lying LUMO energy levels from ?3.90 to ?4.15 eV owing to a strong electron‐withdrawing character. Solution‐processed thin‐film OFETs based on 1a , 1b , 2 , 3 , 4 were measured in both N2 and air. They all showed n‐type FET behavior. The liquid‐crystalline compounds 1a , 1b , and 3 showed good performance owing to the self‐healing properties of the film in the liquid‐crystal phase. Compound 3 has an electron mobility of up to 0.016 cm2 V?1 s?1 and current on/off ratios of 104–105. 相似文献
Chiral polycatenar 1H‐pyrazoles self‐assemble to form columnar mesophases that are stable at room temperature. X‐ray diffraction and CD studies in the mesophase indicate a supramolecular helical organization consisting of stacked H‐bonded dimers. The liquid‐crystalline compounds reported are 3,5‐bis(dialkoxyphenyl)‐1H‐pyrazoles that incorporate two or four dihydrocitronellyl chiral tails. It can be observed that the grafting of these branched chiral substituents onto the 3,5‐diphenyl‐1H‐pyrazole core has a beneficial role in inducing mesomorphism, because isomeric linear‐chain compounds are not liquid crystalline; this is not the usual scheme of behavior. Furthermore, the molecular chirality is transferred to the columnar mesophase, because preferential helical arrangements are observed. Films of the compounds are luminescent at room temperature and constitute an example of the self‐organization of nondiscoid units into columnar liquid‐crystalline assemblies in which the functional molecular unit transfers its properties to a hierarchically built superstructure. 相似文献
We report how the placement of nucleobase units, thymine, or N6‐(4‐methoxybenzoyl)adenine, onto the ends of a mesogenic core, bis‐4‐alkoxy‐substituted bis(phenylethynyl)benzene, affects the properties of these materials. We show that addition of these bulky polar groups significantly reduces the range of liquid‐crystalline behavior of these compounds. However, mixing two complementary nucleobase‐containing AA‐ and BB‐type monomer units together does result in the formation of stable, thermotropic liquid‐crystalline (LC) phases. Hydrogen bonding is shown to play an important role in the formation of these LC phases, consistent with the formation of oligomeric or polymeric hydrogen‐bonded aggregates. X‐ray analyses of these mixed materials are consistent with the formation of smectic C phases. 相似文献
Novel cis‐ and trans‐2‐(p‐bromophenyl)‐5‐methylthiazolidin‐4‐ones, S,N‐containing heterocyclic compounds, were provided in a cis‐stereocomplementary and trans‐stereocomplementary synthetic manner. cis‐Selective cyclo‐condensation proceeded between 2‐sulfanylpropanoic acid (thiolactic acid) and an imine derived from 4‐bromobenzaldehyde and methylamine, whereas Ti(OiPr)4 and Ti(OiBu)4‐promoted trans‐selective cyclo‐condensation proceeded between benzyl 2‐sulfanylpropanoate and the imine. The obtained cis‐ and trans ‐ 2‐(p‐bromophenyl)‐5‐methylthiazolidin‐4‐ones were successfully converted to 2‐(3‐furyl)phenyl derivatives and bis(pinacolato)diborane derivatives utilizing Suzuki–Miyaura and Miyaura–Ishiyama cross‐coupling reactions, respectively, in an umpolung manner. 相似文献
Imine‐bridged rotaxanes are a new type of rotaxane in which the axle and macrocyclic ring are connected by imine bonds. We have previously reported that in imine‐bridged rotaxane 5 , the shuttling motion of the macrocycle could be controlled by changing the temperature. In this study, we investigated how the axle and macrocycle structures affect the construction of the imine‐bridged rotaxane as well as the dynamic equilibrium between imine‐bridged rotaxane 5 and [2]rotaxane 7 by using various combinations of axles ( 1 A , B ), macrocycles ( 2 a – e ), and side‐stations (XYL and TEG). In the threading process, the flexibility of the macrocycle and the substituent groups at the para position of the aniline moieties affect the preparation of the threaded imines. The size of the imine‐bridging station and the macrocyclic tether affects the hydrolysis of the imine bonds under acidic conditions. 相似文献
A solvent‐free method that uses headspace solid‐phase microextraction and gas chromatography with flame ionization detection is proposed for the determination of lignin‐derived phenols in sediments. The extraction and derivatization conditions for the simultaneous analysis of acetosyringone, acetovanillone, syringaldehyde, vanillin, ferulic acid, syringic acid, vanillic acid, p‐hydroxybenzoic acid, and p‐coumaric acid were optimized using a central composite design. After optimization, the best results were obtained with the following conditions: exposure of the polyacrylate fiber to the headspace with 60 μL of N ,O‐bis(trimethylsilyl)trifluoroacetamide as a derivatizing agent for 15 min and then extraction in the headspace of 100 mg of sediment (previously spiked with lignin‐derived phenols) for 35 min. The accuracy of the method was estimated based on recovery tests at two concentration levels and by comparison with a high‐performance liquid chromatography method reported in the literature. Based on the t‐test with a confidence level of 95%, no statistical differences were observed. The detection and quantification limits for the target compounds varied according to their characteristics: values at the microgram per gram level for nonacid compounds and milligram per gram level for phenolic acids, due to the lower volatility of the derivatives. 相似文献
The hydroxyphenyl chiral ketone, (S)‐ 3 , reacts with D ‐amino acids bearing hydrophobic side chains exclusively over the L ‐amino acids in a two‐phase liquid–liquid extraction, and thus acts as a highly stereoselective extractant. Calculations for the energy‐minimized structures for the imine diastereomers and the comparison of the selectivities with other phenyl ketones, (S)‐ 4 and (S)‐ 5 , demonstrate that the hydrogen bond between the carboxylate group and the phenolic hydroxyl group contributes to the remarkable enantioselectivities. The multiple hydrogen bonds present in the imine of (S)‐ 3 reinforce the rigidity, and results in the difference between the stabilities of the imine diastereomers. The imine could be hydrolyzed in methanolic HCl solution, and the extraction of the evaporated residues revived the organic layer of (S)‐ 3 , which could enter into a new extractive cycle and leaves the D ‐amino acid with enantiomeric excess (ee) values of over 97 % in the aqueous layer. 相似文献
In order to find new antimalarial drugs, an exploration about the chemical properties of the starting compounds 3‐amino‐6‐chloro‐4‐phenyl‐1H‐quinolin‐2‐one ( 1 ) and 3‐amino‐4‐methyl‐1H‐quinolin‐2‐one ( 2 ) was developed. Acylation with acyl chloride, sulfonyl chloride and acetic anhydride were carried out. Despite a previous report [2], when acetyl chloride or acetic anhydride were assayed on 1 , only the diacetyl derivative 7 was obtained. When this compound was heated at reflux temperature in a mixture of acetic acid and acetic anhydride, it was transformed in the oxazoloquinoline 8 . Further reactions of the acyl derivatives with diazomethane afforded 1‐methylated compounds. Compound 2 gave the imine 16 by condensation with 4‐nitrobenzaldehyde. 相似文献
Nanoporous thin films with pore size of sub‐10 nm are fabricated using an acid‐cleavable block copolymer (BCP), a benzoic imine junction between poly(ethylene oxide) (PEO) and poly(methacrylate) (PMAAz) bearing an azobenzene side chain (denoted as PEO‐bei‐PMAAz) as the precursor. After a thermal annealing, the block copolymers are self‐assembled to form highly ordered PEO cylinders within a PMAAz matrix normal to the film, even in the case of low BCP molecular weight due to the existing of the liquid crystalline (LC) azobenzene rigid segment. Thus, PMAAz thin films with pore size of ≈7 nm and density of ≈1012 cm−2 are obtained after removal of the PEO minor phase by breaking the benzoic imine junction under mild acidic conditions. This work enriches the nanoporous polymer films from BCP precursors and introduces the LC property as a functionality which can further enhance the mechanical properties of the films and broaden their applications.