Discotic Triphenylene Research Articles

Triphenylene Discotic Pd(II) Metallomesogens Based on Triazole Ligands Derived from the Click Reaction

Triphenylene Discotic Pd(II) Metallomesogens Based on Triazole Ligands Derived from the Click Reaction

Triphenylene discotic liquid crystals: biphenyls, synthesis, and the search for nematic systems

ABSTRACT The development of the cyanobiphenyls for display applications was one of the most important technological advances of the 20th century. Here, we present a personal account of how advances in biphenyl science (synthesis and application) influenced the development of discotic liquid crystals. We focus on those based on triphenylene, the most widely studied discotic core. The search for nematic discotics proved to be challenging with relatively few early examples being reported. In examples of symmetrically hexasubstituted triphenylenes, a ring of peripheral aryl ester or alkynylaryl substituents provides effective steric blocking to columnar assembly – the face-to-face molecular arrangement that is observed in the majority of triphenylene discotics. The synthetic challenges associated with early triphenylene synthesis have now been largely overcome. Efficient oxidative trimerisation of dialkoxybenzenes gave direct access to materials with high purity and at scale. The intermediates can be manipulated through deprotection and elaboration, a pathway that allowed synthesis of lyotropic (Nc) systems among others. The combination of modern cross-coupling chemistry with oxidative processes has proved versatile, leading to synthesis of unsymmetrical monomeric and dimeric systems. Dimeric systems linked by rigid bridges have been identified as a separate class of materials that show strong tendency for nematic mesophase formation.

Ab-initio and molecular dynamics simulation of a discotic liquid crystal in ionic solution

ABSTRACT The Physico-chemical, electro-optical and spectroscopic properties of 2,3,6,7,10,11-hexakispentyloxytriphenylene (HPTP) discotic liquid crystal (DLC) have been investigated in gas and NaCl solution using B3LYP/6-311++G(d,p) and M06-2X/6-311++G(d,p) methods. Both the computational techniques yield enhanced values of electro-optical and global reactivity descriptor parameters of HPTP LC molecule in NaCl solution. Neither of the techniques reveal a red or blue shift in the absorption spectra of the LC molecule. The electron localised function (ELF) and frontier molecular orbitals have been examined. Both in gas and solvation medium, electronic circular dichroism (ECD) spectra evidence significant optical activity of the discotic LC molecule. The range-separated hybrid functional such as LC-BLYP/LC-TDDFT formalism has also been used for estimating electronic property and excitation energy of the triphenylene LC molecule; and results obtained by LC-BLYP, B3LYP, and M06-2X computations have been juxtaposed for an extensive comparison. Furthermore, molecular dynamics simulation elucidates that stability and interaction ability of HPTP LC molecule are improved in the ionic (NaCl) solution. These findings provide a new framework for understanding the structural characteristics, and electro-optical, electronic, and dynamical behaviour of discotic triphenylene analogue in ionic solution.

Functionalized Triphenylene Discotic Molecules: Synthesis and Mesomorphic Characterizations

AbstractWe report the synthesis and characterization of two sets of triphenylene derived discotic molecules with phenol, aldehyde and acid functional groups. In the first set, triphenylene moiety was tethered with benzene derivatives via an ester linkage, while in the second set via an ether linkage with increased aromatic conjugation. All the molecules have triphenylene disc at one end and with benzene, biphenyl and terphenyl cores at the other end connected via flexible methylene spacers. The chemical structures of the novel compounds were confirmed by IR, NMR spectroscopy and CHN analysis methods. Thermal and liquid crystal texture properties were determined using differential scanning calorimetry, polarized optical microscope and X‐ray diffraction studies. Amongst all the novel compounds, only the terphenyl derivative displayed mesomorphism. However, their charge transfer complexes with trinitrofluorenone (TNF) an electron acceptor exhibited columnar mesophases.

Impact of a chiral supramolecular nanostructure on the mechanical and electrical performances of triphenylene-based discotic physical gels.

Discotic π-conjugated supramolecular assemblies, especially with chiral supramolecular nanostructures, have been attracting growing research interest due to their significant optoelectronic properties and the possibilities of their applications in the new generation of organic semiconductors. However, the impact of supramolecular chirality on their mechanical and electrical performances remains poorly understood. Herein, a series of optically active supramolecular gels were formed from achiral triphenylene derivatives by introducing limonene as the chiral source. Owing to the well-ordered supramolecular packing, the homochiral supramolecular gels exhibited greater mechanical strength and higher conductivity, compared to heterochiral architectures. The impact of supramolecular packing in homochiral or heterochiral assemblies on their resulting mechanical and electrical performances was investigated in detail, which might be of great fundamental value for the rational design of chiral π-conjugated supramolecular nanostructures for applications in chiral optoelectronics.

Significantly Enhanced Thermotropic Liquid Crystalline Columnar Mesophases in Stereoregular Polymethylenes with Discotic Triphenylene Side Groups

Side-chain discotic liquid crystalline polymers (SDLCPs) with discotic (disclike) mesogens (discogens) attached as side groups through flexible spacers constitute a class of fascinating organic polymer semiconducting materials. While so far almost all reported SDLCPs belong to conventional C2 polymers based on polymerization of vinyl monomers, limiting their structure diversities, substitution density, and efficiency promotion. In this article we present the synthesis of a series of syndiotactic polymethylene SDLCPs of Pm(TPn) with discotic triphenylene (TP) side groups of variant peripheral alkoxy substituents (n = 6, 4, 10) and different length alkyl spacers (m = 3, 4, 6, 8, 10, 12) through an indirect two-step rhodium-complex-catalyzed C1 carbene polymerization pathway. The thermal properties and ordered organization structures of the precursor polymers and polymethylene SDLCPs have been systematically investigated with differential scanning calorimetry (DSC) and polarized optical microscopy (POM), esp...

Chiral crystal-like droplets displaying unidirectional rotational sliding.

The self-assembly of organic molecules into supramolecular materials with structural ordering beyond the nanometre scale is challenging. Here, we report the spontaneous self-assembly of a chiral discotic triphenylene derivative into millimetre-sized droplets. The structure of the droplets is characterized by high positional and orientational ordering and a three-dimensional integrity similar to that of single crystals. Notwithstanding, these assemblies slide when placed on a vertical substrate demonstrating their fluid nature. X-ray imaging shows that during the sliding process the internal crystal-like structure is maintained and that the droplets undergo clockwise or counterclockwise unidirectional rotation, depending on the chirality of their molecular components. Rheological measurements suggest that this rotational behaviour might result from the distinct yield stress between the (R)- and (S)-enantiomers. Overall, our findings demonstrate that molecular chirality can determine the movement direction of a supramolecular structure, thus expanding the fundamental understanding of the structure and dynamics of soft materials.

Novel Annulated Triphenylene Discotic Liquid Crystals Generated by Pictet‐Spengler Cyclization

AbstractTriphenylenes have been frontrunner in discotic liquid crystalline materials since their discovery. They possess great richness of mesomorphism in them. Chemists have been exploring this potential quite often by some substitutions in the core or periphery of the triphenylene molecule. In this current report, we extended the triphenylene ring system by fusing with nitrogen and studied their mesomorphic and optical properties. Four new compounds are prepared using Pictet‐Spengler cyclization of hexaalkoxytriphenylene‐1‐amine with various aldehydes. All the new compounds are well characterized using spectral and elemental analysis. Their mesomorphic properties are evaluated using polarizing optical microscopy, differential scanning calorimetry and X‐ray diffractometry. These derivatives showed columnar hexagonal phase with great promise for further studies.

Использование молекулярных параметров в прогнозировании мезоморфизма звездообразных дискотических производных трифенилена

Использование молекулярных параметров в прогнозировании мезоморфизма звездообразных дискотических производных трифенилена

Incorporation of liquid crystalline triphenylene derivative in bulk heterojunction solar cell with molybdenum oxide as buffer layer for improved efficiency

ABSTRACTWe report efficient bulk heterojunction solar cells fabricated by inserting a discotic triphenylene derivative into poly (3-hexylthiophene): [6, 6]- phenyl-C61-butyric acid methyl ester. A layer of molybdenum oxide was inserted between anode and active layer. Power conversion efficiency of 2.0% was achieved for these photovoltaic solar cells containing self-organised discotic liquid crystals in the active layer under one sun condition. The influence of varying the thickness of liquid crystal layer and annealing on these solar cells was also studied. Post annealing the bulk heterojunction devices with discotic liquid crystal layer of thickness 20 nm in them yielded an open circuit voltage of 0.41 V, short circuit current density of 17.0 mA cm−2, a Fill factor of 0.35 and power conversion efficiency of 2.5%.

ChemInform Abstract: Synthesis, Complexation, and Mesomorphism of Novel Calixarene‐Linked Discotic Triphenylene Based on Click Chemistry.

Abstract 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.

Supramolecular transformation from ordered columnar to disordered columnar to tetragonal micellar structures in clicked dodeca-alkylated discotic triphenylene liquid crystals

We prepared three discotic liquid crystals (DLCs) based on a triphenylene (TP) disc functionalized with twelve alkyl peripheries. The synthesis of the discogens was performed by a click reaction using Cu(OAc)2 as the catalyst, with six triazolyl groups connecting the TP core with twelve alkyl chains. According to thermal data from differential scanning calorimetry (DSC), discogen , which has the shortest hexyl peripheries, exhibited two LC phases, and and , with decyl and tetradecyl peripheries, respectively, displayed three LC phases as a function of the temperature. Structural analyses using small- and wide-angle X-ray scattering (SAXS and WAXS) techniques revealed ordered and disordered hexagonal columnar LC phases in all the discogens. On the other hand, an unconventional micellar phase with P42/mnm symmetry consisting of thirty micelles was found only in and , when the temperature increased. The thermally induced transformation from the columnar to the micellar phase can be explained by increased chain entropy at higher temperatures. The complex micellar packing in the noncubic phase is attributed to the softness of the DLC micelles because the micellar corona consists of flexible alkyl chains. The discogen design concept in this study (i.e., the introduction of multibranched alkyl peripheries to the discotic mesogens via click chemistry) resulted in unconventional columnar-to-micellar transformation in conventional TP DLCs.

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.

Synthesis of Triphenylene Discotic Liquid Crystals Possessing Nine Alkyl Chains: Influence of Molecular Symmetry and Chain Length on Mesomorphism

A series of new triphenylene discotic liquid crystals has been synthesized by a straightway and the influence of molecular symmetry and chain length on the mesomorphism investigated. The symmetrical compounds 1, 3,7,11-trimethoxytriphenylene-2,6,10-triyl tris(3,4,5-tris(alkyloxy)benzoate), with alkyl chain lengths of C7, C8, C10, and C12, and the unsymmetrical compounds 2 were studied by using polarized optical microscopy (POM), differential scanning calorimetry (DSC) and by wide-angle X-ray diffraction (XRD). The results showed that the symmetrical compounds 1a (C7) and 1b (C8) exhibit a plastic columnar mesophase, whereas the other compounds display a hexagonal columnar mesophase over a wide temperature range. All symmetrical compounds 1 display higher isotropization temperatures than that of the unsymmetrical 2. The clearing points are lowered as the alkyl chain lengthened.

Mono-Disperse Triphenylene Discotic Liquid Crystal Oligomers Synthesized by Click Chemistry

Mono-Disperse Triphenylene Discotic Liquid Crystal Oligomers Synthesized by Click Chemistry

Discotic Triphenylene Twins Linked through Thiophene Bridges: Controlling Nematic Behavior in an Intriguing Class of Functional Organic Materials

Substituted triphenylenes and similar discotic molecules have a strong tendency toward columnar organization. Nematic mesophases are much less commonly observed in discotic systems. We have demonstrated a general strategy whereby discotic triphenylenes can be twinned to form stable, boardlike materials that display only nematic mesophases. The dominant structural feature that leads to nematic behavior is an enforced void region in the center of the macrocycle that results from bridging through the triphenylene 3,6-positions. This precludes simple columnar assembly because it would lead to free space through the center of each stack. Selection of appropriate bridging units allows materials to be designed which combine molecular features, such as the optoelectronic properties of electron-rich triphenylenes and conjugated thiophene units, with the processability, self-healing, and alignment features inherent in nematic mesophases. In addition, communication across twinned structures can lead to additional enhancement of optoelectronic behavior. This is particularly apparent in fully conjugated, planar twin 12 which is formally expected to have some antiaromatic character. This character is manifested in its spectral properties, and particularly noteworthy is its strong, Stokes shifted emission at around 500 nm.

Competition and Promotion between Two Different Liquid-Crystalline Building Blocks: Mesogen-Jacketed Liquid-Crystalline Polymers and Triphenylene Discotic Liquid Crystals

Mesogen-jacketed liquid-crystalline polymers (MJLCPs) containing two triphenylene (Tp) units in the side chains, denoted as PPnV (n = 3 or 6, which is the number of the methylene units between the terephthalate core and Tp moieties in the side chains), were synthesized through conventional free radical polymerization, and the phase behaviors of these new combined main-chain/side-chain liquid-crystalline (LC) polymers were investigated. The chemical structures of the monomers were confirmed by elemental analysis, high-resolution mass spectrometry, and 1H/13C NMR. The molecular characterizations of the polymers were performed with 1H NMR, gel permeation chromatography, and thermogravimetric analysis. LC behaviors of the polymers were investigated by differential scanning calorimetry (DSC), polarized light microscopy, and wide-angle X-ray diffraction (WAXD). Both polymers exhibit excellent thermal stabilities. DSC and WAXD results indicate that covalently incorporating Tp discotic liquid crystals has a treme...

Controlling Orientation Direction of Discotic Columns Assembled in Microtrenches

Microtrenches have been produced on the surface of a glass substrate using conventional photolithography technique. When subsequently deposited on the micro-patterned substrate, discotic triphenylene molecules are found to assemble into columns with orientational ordering. Homogeneous alignment of the discotic columns has been produced on the substrate with parallel microtrenches. The orientational direction of the discotic columns can be controlled using a set of controlling microtrenches. By properly modifying the topological structures of the controlling microtrenches we are able to tune the discotic columns assembled in the primary trenches to align either parellel or perpendicular to the walls of the trenches.

Synthesis and liquid crystal properties of triphenylene liquid crystals bearing polymerisable acrylate and methacrylate groups

The synthesis and liquid crystalline properties of some new triphenylene discotics bearing pendant acrylate groups are described. Mesophase behaviour is found to be sensitive to the number and position of substituents, the linking chain length, and to change between acrylate and methacrylate termini. Investigation of the isomerically pure triphenylene acrylate and methacrylate derivatives showed that the molecular symmetry also has a modest effect on mesophase behaviour. Unsurprisingly columnar phases are formed only when all substituent chains are of comparable length and methacrylates are far superior to simple acrylate termini, probably due to favourable space filling in the mesophase.

Synthesis of Calixarene‐Linked Discotic Triphenylene

AbstractThe syntheses of new macrocyclic molecules containing calixarene and discotic triphenylene units in good yields are reported. Structural and conformational characterization of these new compounds was achieved by UV/Vis, FTIR, and NMR spectroscopy; mass spectrometry; and elemental analysis. The liquid‐crystalline behavior was studied by polarizing optical microscopy, differential scanning calorimetry, and X‐ray diffraction. The symmetrical calix[4]arene‐linked triphenylene dimer with a C10 chain (2b) exhibited the liquid‐crystalline behavior of a calixarene bowlic column with two triphenylene units as ancillary lateral columns.