Triphenylene Units Research Articles

Porous Nanographenes, Graphene Nanoribbons, and Nanoporous Graphene Selectively Synthesized from the Same Molecular Precursor.

We demonstrate a family of molecular precursors based on 7,10-dibromo-triphenylenes that can selectively produce different varieties of atomically precise porous graphene nanomaterials through the use of different synthetic environments. Upon Yamamoto polymerization of these molecules in solution, the free rotations of the triphenylene units around the C-C bonds result in the formation of cyclotrimers in high yields. In contrast, in on-surface polymerization of the same molecules on Au(111) these rotations are impeded, and the coupling proceeds toward the formation of long polymer chains. These chains can then be converted to porous graphene nanoribbons (pGNRs) by annealing. Correspondingly, the solution-synthesized cyclotrimers can also be deposited onto Au(111) and converted into porous nanographenes (pNGs) via thermal treatment. Thus, both processes start with the same molecular precursor and end with a porous graphene nanomaterial on Au(111), but the type of product, pNG or pGNR, depends on the specific coupling approach. We also produced extended nanoporous graphenes (NPGs) through the lateral fusion of highly aligned pGNRs on Au(111) that were grown at high coverage. The pNGs can also be synthesized directly in solution by Scholl oxidative cyclodehydrogenation of cyclotrimers. We demonstrate the generality of this approach by synthesizing two varieties of 7,10-dibromo-triphenylenes that selectively produced six nanoporous products with different dimensionalities. The basic 7,10-dibromo-triphenylene monomer is amenable to structural modifications, potentially providing access to many new porous graphene nanomaterials. We show that by constructing different porous structures from the same building blocks, it is possible to tune the energy band gap in a wide range.

Dynamic change of molecular conformation generating a variation of liquid crystalline phases for triphenylene mesogens with peripheral alkoxyazobenzenes

ABSTRACT A triphenylene mesogen which possesses six dodecyloxyazobenzene units at the periphery linked by propylene-ether chain (2-C12-3) was synthesised and its mesomorphic phase transition behaviour was investigated. It was found that 2-C12-3 exhibits six mesophases including one monotropic phase. The calamitic-discotic bi-mesomorphic phase transition was also observed. As cooling the compound at the temperature of iso phase, SmA phase comes up and further cooling gives Col ob phase. In comparison to the corresponding ester-linked derivative (1-C12-3), which shows only two mesophases (SmA and Colr), the linkage part connecting triphenylene unit and the peripheral alkoxyazobenzenes significantly affect the molecular ordering in mesophase, though the bi-mesomorphic property is maintained in the case of dedecyloxy chains.

Columnar liquid crystalline triphenylene-bis(dithiolene)nickel complexes. Soft photothermal materials

This work reports new soft photothermal materials based on mesomorphic nickel bis(dithiolene) complexes bearing pentakis(dodecyloxy)triphenylene units, in which the triphenylene core and the metal complex are linked through alkyl connectors.

Thermal homeotropic self-alignment on a single substrate of new series of discotic nematic triphenylene-based main-chain polyesters

We present the synthesis, characterization, and study of Liquid Crystal properties of a new series of polyesters containing 2,7-di-functionalized triphenylene units in the main chain, whose distinctive feature is that the carboxyl moiety is distant from the aromatic core. Several molecular aspects, such as the distance between the carboxylic group to the core, the length of the connector, and the orientation of the carboxyls were analyzed. In addition, we have investigated the influence of these molecular parameters on the thermal self-alignment of the polymers on different substrates. We have found a simple method to obtain a monodomain homeotropic orientation of these polyesters on a single substrate.

Uniform Colloidal Polymer Rods by Stabilizer-Assisted Liquid-Crystallization-Driven Self-Assembly.

The synthesis of anisotropic colloidal building blocks is essential for their self-assembly into hierarchical materials. Here, a highly efficient stabilizer-assisted liquid-crystallization-driven self-assembly (SA-LCDSA) strategy was developed to achieve monodisperse colloidal polymer rods. This strategy does not require the use of block copolymers, but only homopolymers or random copolymers. The resulting rods have tunable size and aspect ratios, as well as well-defined columnar liquid crystal structures. The integrated triphenylene units enable the rods to exhibit unusual photo-induced fluorescence enhancement and accompanying irradiation memory effect, which, as demonstrated, are attractive for information encryption/decryption of paper documents. In particular, unwanted document decryption during delivery can be examined by fluorescence kinetics. This SA-LCDSA-based approach can be extended to synthesize other functional particles with desired π-molecular units.

Uniform Colloidal Polymer Rods by Stabilizer‐Assisted Liquid‐Crystallization‐Driven Self‐Assembly

AbstractThe synthesis of anisotropic colloidal building blocks is essential for their self‐assembly into hierarchical materials. Here, a highly efficient stabilizer‐assisted liquid‐crystallization‐driven self‐assembly (SA‐LCDSA) strategy was developed to achieve monodisperse colloidal polymer rods. This strategy does not require the use of block copolymers, but only homopolymers or random copolymers. The resulting rods have tunable size and aspect ratios, as well as well‐defined columnar liquid crystal structures. The integrated triphenylene units enable the rods to exhibit unusual photo‐induced fluorescence enhancement and accompanying irradiation memory effect, which, as demonstrated, are attractive for information encryption/decryption of paper documents. In particular, unwanted document decryption during delivery can be examined by fluorescence kinetics. This SA‐LCDSA‐based approach can be extended to synthesize other functional particles with desired π‐molecular units.

Triphenylene-ethylammonium tetrachlorometallate salts: multicolumnar mesophases, thermochromism and Langmuir films

This study reports mesomorphic triphenylene-ethylammonium salts containing [MCl4]2− (M = Cu, Ni, Co, Mn) as counterion. The [NiCl4]2− group leads to combine mesomorphism, paramagnetism and thermochromism in the system.

Redox Ladder of Ni3 Complexes with Closed‐Shell, Mono‐, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs

AbstractWe report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11‐hexaoxytriphenylene (HOTP), [(Me3TPANi)3(HOTP)](BF4)n (Me3TPA=N,N,N‐tris[(6‐methyl‐2‐pyridyl)methyl]amine) (n=2, 3, 4 for complexes 1, 2, 3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from −4, to −3, and −2 in 1, 2, and 3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed‐shell configurations for HOTP in 1, 2, and 3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal‐organic frameworks such as Ni9HOTP4, these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

Redox Ladder of Ni3 Complexes with Closed-Shell, Mono-, and Diradical Triphenylene Units: Molecular Models for Conductive 2D MOFs.

We report the isolation and characterization of a series of trinickel complexes with 2,3,6,7,10,11-hexaoxytriphenylene (HOTP), [(Me3 TPANi)3 (HOTP)](BF4 )n (Me3 TPA=N,N,N-tris[(6-methyl-2-pyridyl)methyl]amine) (n=2, 3, 4 for complexes 1, 2, 3). These complexes comprise a redox ladder whereby the HOTP core displays increasingly quinoidal character as its formal oxidation state changes from -4, to -3, and -2 in 1, 2, and 3, respectively. No formal oxidation state changes occur on Ni, allowing the isolation of singlet diradical, monoradical, and closed-shell configurations for HOTP in 1, 2, and 3, respectively, with a concomitant decrease in the spin coupling strength upon oxidation. Because the three complexes can be considered models of the smallest building blocks of 2D conductive metal-organic frameworks such as Ni9 HOTP4 , these results serve as possible inspiration for the construction of extended materials with targeted electric and magnetic properties.

Azatriphenylene-based D-A-D-typed hole-transporting materials for perovskite solar cells with tunable energy levels and high mobility

Computational study on relationship between molecular structure and property of small molecule hole-transporting materials (HTMs) is an efficient pathway to acquire potential HTMs for perovskite solar cells (PSCs). Herein, by conjugating the acceptor groups of electron-deficient diazatriphenylene (DAT), tetraazatriphenylene (TAT) and hexaazatriphenylene (HAT), and p-methoxy-substituted triphenylamine (MeOTPA) electron-donors, six novel donor–acceptor-donor (D-A-D) typed HTMs (SM11 ~ SM16) are designed. Furthermore, three thiophene-substituted acceptors (SM17 ~ SM19) are also investigated. The influences of acceptor moiety on the performance of HTMs are studied by carrying out theoretical chemical calculations. Compared with the reported HTM with triphenylene unit (TPH-T), the new tailored HTMs (SM11 ~ SM19) exhibit more negative highest occupied molecular orbital (HOMO) energy levels and slightly red-shifted light absorption due to the increased electron-deficient property of acceptor group and linked positions with the MeOTPA-donor. Meanwhile, our results show that the small torsion angle between the acceptor and the donor is beneficial to promote the hole transport in HTMs, and the thiophene units on acceptor may also be helpful to enhance the charge mobility of HTMs. In addition, the large charge transfer amounts and small exciton binding energies are found for designed HTMs, which will be favorable to facilitate the electron-hole separation in HTMs. The stability of HTMs may be decreased based on the calculated results of electrostatic surface potential and absolute hardness. We hope this work could highlight the potential of azatriphenylene acceptor-based D-A-D typed HTMs for efficient PSCs.

Piperazine-based two-dimensional covalent organic framework for high performance anodic lithium storage

The controllably spatial and chemical structures and abundantly elemental reserves of covalent organic frameworks (COFs) endow them the potential of being applied in next generation of electrochemical lithium-ions storage with high performances. Here, a piperazine-based two-dimensional covalent organic framework (PTDCOF) is designed and synthesized. PTDCOF is constructed by triphenylene units through irreversible piperazine linkages to afford the regular in-plane pores sized ~11 Å. PTDCOF is charactered with few-layered features, which is crystalized through eclipsed (AA) and staggered (AB) stacking modes together. And the synthesized framework exhibits excellent stability upon harsh chemical environments. As the active material of anodic lithium storage, the guest-eliminated product derived by PTDCOF demonstrates remarkable lithiation (1644.3 mAh g − 1 capacity contribution at 0.1 A g − 1), rate and cycling performances. The abundant active sites lead to a high and reversible lithium loading of at least 14 lithium atoms per triphenylene unit (Li14(C18N3H9)). Such product presents superior anodic lithiation capability comparing with previously reported carbonaceous materials. This study provides a possible and attractive path for hunting the high performances of lithium or other metal ions storage systems.

Triphenylene-fluorescein-triphenylene trimers: novel columnar liquid crystals with solid fluorescence

ABSTRACT This paper reported the first triphenylene-fluorescein-triphenylene trimers (3a and 3b), which exhibited stable hexagonal columnar mesophase and good fluorescence in comparison with the similar triphenylene-fluorescein dimers. The trimers 3a and 3b bridged by -C3H6- and -C6H12- group were conveniently prepared in yields of 67% and 73%. They exhibited the stable hexagonal columnar mesophase, high fluorescence quantum yields, and the large Stokes shifts due to the influence of two triphenylene units. The highest fluorescence quantum yield attained 0.91 for 3b and the largest Stokes shift reached 105 nm for 3a. This work revealed that trimers were a good strategy to construct novel columnar liquid crystals with stable columnar mesophase and high fluorescence.

Synthesis and Optical Properties of Triphenylene-Based Donor-Donor and Donor-Acceptor Conjugated Polymers: A Comparative Study

Two new conjugated polymers (P1 and P2), containing a bithiophene donor unit coupled with either a triphenylene donor unit or an imide-functionalized triphenylene acceptor unit in the backbone, have been synthesized, structurally characterized, and comparatively studied by using 1H NMR, FT-IR, gel permeation chromatography, differential scanning calorimetry, cyclic voltammetry, ultraviolet-visible absorption, and fluorescence spectroscopy. Both polymers are amorphous in nature and thermally stable up to 450°C. The inclusion of the imide functionalization in the triphenylene unit significantly lowered the lowest unoccupied molecular orbital energy level and thus the bandgap of the donor-acceptor polymer P2 over the donor-donor polymer P1. P1 and P2 show very different optical properties in hexane and other solvents. P1 shows a broad emission in hexane but vibronically structured emissions in other solvents; in contrast, P2 exhibits a vibronically resolved emission in hexane, while exhibiting redshifted, broad, and featureless emissions in other solvents. P1 takes a random coil conformation in good solvents like p-xylene, benzene, toluene, anisole, chloroform, THF, and o-dichlorobenzene, whereas in hexane, it may adopt a helical folding conformation. In the poor solvent DMSO, interchain aggregates dominate. P2, on the other hand, adopts a random coil conformation in hexane but possibly the helical folding conformation in other good solvents. The opposite conformations of the two polymers may be responsible for their opposite solvent-dependent fluorescence properties. By virtue of the very different fluorescence properties of these two polymers in nonpolar solvents such as hexane and in polar solvents, the potential of using the polymers to detect the trace amount of ethanol content that is added to gasoline has been revealed with high sensitivity.

Constituent Isomerism-Induced Quasicrystal and Frank–Kasper σ Superlattices Based on Nanosized Shape Amphiphiles

Naturally, subtle variations in the chemical structures of constituent molecules may significantly affect their multiscale spatial arrangements, properties, and functions. Deceptively simple spheri...

Mesomorphic properties of linear and branched new triphenylene‐based poly(ester‐ether)s

AbstractA series of main chain discotic liquid crystal polymers, synthesized following a new approach based on the incorporation of triphenylene units in both comonomers, show ordered columnar mesophases in a very wide thermal range, including room temperature. The introduction of branching points based on the same kind of triphenylene units increases their thermal range and gives rise to glassy low‐temperature phases. Room temperature extrusion of these polymers yields fibers with molecules oriented perpendicular to the mechanical stress, and an orientational order parameter close to 0.5, which slightly increases for branched polymers.

Two-dimensional extended π-conjugated triphenylene-core covalent organic polymer

A covalent organic polymer with embedded triphenylene units was synthesized by Glaser–Hay cross-coupling, showing outstanding performance for lithium storage.

Novel fluorescent liquid crystals: synthesis, mesomorphism and fluorescence of triphenylene-Bodipy derivatives based on 1,3,5-triazine core

ABSTRACTThe novel triphenylene-Bodipy derivatives 6 and 7 based on 1,3,5-triazine core were designed and synthesised by introducing BODIPY unit and triphenylene units sequentially onto cyanuric chloride. The Bodipy derivative 6 with one triphenylene unit was a nematic liquid crystal but the derivative 7 with two triphenylene units was a hexagonal columnar liquid crystal. The investigation on photophysical properties suggested that both of them exhibited excellent fluorescence with high fluorescence quantum yields and the Stokes shifts were larger than their Bodipy precursors. This research presented a good example of design and synthesis of columnar Bodipy liquid crystal with high fluorescence and large Stokes shift.

Bowl liquid crystal based on cyclotriveratrylene derivatives with multiple triphenylene units: The influences of the numbers of triphenylene units on mesomorphic behaviors

Series of novel CTV derivatives with one, two and three triphenylene units were designed and synthesized via click reaction in 72–84% yields. The influences of the numbers of triphenylene units on mesomorphic behaviors were investigated. The results suggested that one triphenylene unit could not counteract the rigidity of CTV skeleton, resulting in no mesophase for CTV derivative 6 with one triphenylene unit. The strong induction of more triphenylene units leaded to the mesophase for CTV derivative 7 with two triphenylene units and 8 with three triphenylene units. The more triphenylene units decreased the phase transition temperatures. The XRD analysis suggested that compound 8 possessed higher ordered hexagonal columnar mesophase than compound 7, implying that the more triphenylene units were favorable for improving the structural symmetry and produced the ordered columnar stacking. Compound 8 was the first example of high ordered hexagonal columnar liquid crystalline molecule based on CTV skeleton.

Dibenzohexacene: Stabilization Through Additional Clar Sextets.

Triphenylene units stabilize hexacenes as dibenzohexacenes. The hexacenes formed by a statistical Yamamoto coupling of dibromobenzene with dibromo-TIPS-pentacene or, alternatively, Stille coupling with dimethyldibenzostannole. UV/Vis spectroscopy and quantum chemical calculations show that despite the double benzannulation, the species have hexacene-type character, as evidenced by their redshifted absorption characteristics. The charge carrier mobility of dibenzohexacene 1 a was determined up to 0.2 cm2 /(Vs).

Synthesis and mesomorphic properties of calix[4]resorcinarene–triphenylene oligomers

ABSTRACTBy controlling the mol ratios of reactants, novel calix[4]resorcinarene–triphenylene monomer, dimer and tetramer were designed and synthesised in yields of 50–60% via Click chemistry. Their structures were characterised by NMR and MS. Their liquid crystalline behaviours were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction analysis. The more triphenylene units on calix[4]resorcinarene resulted in the wider temperature scopes of mesophase and higher phase transition temperatures. The monomer 6 and dimer 7 showed the mixed columnar mesophase with hexagonal columnar structure and disordered lamellar columnar structure, and compound 8 possessed only disordered lamellar columnar mesophase. These research results suggest that calix[4]resorcinarene was a good platform to construct columnar liquid crystal and the mesomorphic properties were greatly influenced by the substituted numbers of mesogen units on calix skeleton.