Triphenylene Molecules Research Articles

First principle studies on triphenylene-hexathiol-based metal-organic framework for hydrogen storage application

We have studied the hydrogen storage capability of the recently synthesized triphenylene-hexathiol based metal-organic framework (MOF) with Fe and Cu metal atoms by using density functional theory and Ab Initio Molecular Dynamics (AIMD) simulations. We found that up to 12 hydrogen molecules were spontaneously adsorbed on the six Fe atoms of the MOF (FeMOF) with adsorption energy of −0.18 eV per H2 molecule, whereas only six H2 molecules were adsorbed on the six Cu atoms of the MOF (CuMOF) with an adsorption energy of −0.17 eV per H2 molecule. Hydrogen molecules were adsorbed on the Fe atom in the FeMOF surface by Kubas interaction. It is observed that the H2 storage capacity of FeMOF did not change due to the substitution of electron donating group, OCH3 on triphenylene molecules. The charge transfer from H2 molecules to the MOF through metal atoms has been confirmed through the density of states and Bader charge analysis. The gravimetric weight percentage of the FeMOF is found to be 1 wt% at room temperature and 1 atm pressure which is considerably higher than that of the studied CuMOF (0.5 wt%). Further, the AIMD results confirmed the structural stability of the studied MOFs. Therefore, the studied FeMOF surface is a suitable material for efficient and reversible hydrogen storage application.

Poly-triphenylene membrane: A multifunctional two-dimensional porous carbon framework with ultra-high carrier mobilities and potassium ion storage capacity

The development of multifunctional two-dimensional (2D) carbon-based materials with novel, excellent properties and high performance is a challenge. By using density functional theory methods, a novel 2D planar and porous carbon material 2D-C18H6, which is a poly-triphenylene membrane composed of triphenylene molecules, is systematically investigated. The computational results confirm that the 2D-C18H6 structure has good lattice dynamics stability and high thermal stability. 2D-C18H6 displays great gas separation ability with high selectivity and high diffusive flux of He and H2 from other gas molecules, due to its dense pores of proper size in the structure. It is a semiconductor with a direct band gap of 2.36 eV and ultra-high carrier mobilities along both a and b directions, up to 7.6 × 104 cm2V−1s−1. The adsorption and migration of K atoms on 2D-C18H6 monolayer indicate it exhibits ultra-high theoretical specific capacity of 1449 mAh·g−1, low voltage of 0.285–0.024 V and low migration barrier of 0.125 eV. Possessing various excellent properties, 2D-C18H6 monolayer has potential applications in electronic device semiconductors, potassium ion battery anode materials, photocatalytic hydrogen evolution materials and gas separation membranes.

Host-Guest Doping in Flexible Organic Crystals for Room-Temperature Phosphorescence.

Organic single crystals (OSCs) with excellent flexibility and unique optical properties are of great importance due to their broad applicability in optical/optoelectronic devices and sensors. Nevertheless, fabricating flexible OSCs with room-temperature phosphorescence (RTP) remains a great challenge. Herein, we propose a host-guest doping strategy to achieve both RTP and flexibility of OSCs. The single-stranded crystal is highly bendable upon external force application and can immediately return to its original straight shape after removal of the stress, impressively emitting bright deep-red phosphorescence. The theoretical and experimental results demonstrate that the bright RTP arises from Förster resonance energy transfer (FRET) from the triphenylene molecules to the dopants. This strategy is both conceptually and synthetically simple and offers a universal approach for the preparation of flexible OSCs with RTP.

Host–Guest Doping in Flexible Organic Crystals for Room‐Temperature Phosphorescence

AbstractOrganic single crystals (OSCs) with excellent flexibility and unique optical properties are of great importance due to their broad applicability in optical/optoelectronic devices and sensors. Nevertheless, fabricating flexible OSCs with room‐temperature phosphorescence (RTP) remains a great challenge. Herein, we propose a host–guest doping strategy to achieve both RTP and flexibility of OSCs. The single‐stranded crystal is highly bendable upon external force application and can immediately return to its original straight shape after removal of the stress, impressively emitting bright deep‐red phosphorescence. The theoretical and experimental results demonstrate that the bright RTP arises from Förster resonance energy transfer (FRET) from the triphenylene molecules to the dopants. This strategy is both conceptually and synthetically simple and offers a universal approach for the preparation of flexible OSCs with RTP.

Segregated Array Tailoring Charge-Transfer Degree of Organic Cocrystal for the Efficient Near-Infrared Emission beyond 760nm.

Harvesting the narrow bandgap excitons of charge-transfer (CT) complexes for the achievement of near-infrared (NIR) emission has attracted intensive attention for its fundamental importance and practical application. Herein, the triphenylene (TP)-2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4 TCNQ) CT organic complex is designed and fabricated via the supramolecular self-assembly process, which demonstrates the NIR emission with a maximum peak of 770nm and a photoluminescence quantum yield (PLQY) of 5.4%. The segregated stacking mode of TP-F4 TCNQ CT complex based on the multiple types of intermolecular interaction has a low CT degree of 0.00103 and a small counter pitch angle of 40° between F4 TCNQ and TP molecules, which breaks the forbidden electronic transitions of CT state, resulting in the effective NIR emission. Acting as the promising candidates for the active optical waveguide in the NIR region beyond 760nm, the self-assembled TP-F4 TCNQ single-crystalline organic microwires display an ultralow optical-loss coefficient of 0.060dBµm-1 . This work holds considerable insights for the exploration of novel NIR-emissive organic materials via an universal "cocrystal engineering" strategy.

Некоторые особенности спектра и кинетики фосфоресценции трифенилена в бромбензоле при 77 К

The spectrum and kinetics of triphenylene phosphorescence under monochromatic and broadband excitation in bromobenzene at 77 K were studied. It was found that the intensity distribution in the phosphorescence spectrum depends on the spectral composition of the exciting light. In the transition from excitation by monochromatic radiation of a nitrogen laser ($\lambda_{ex} = 337$ nm) to broadband excitation by a high-pressure xenon lamp with a filter of 313 nm, a 0--0 band gain is observed relative to the most intense vibronic band of a half-symmetric oscillation ($\nu =1605$ cm$^{-1})$. In this case, a broadening of the 0--0 band and a shift of its maximum to the short-wave region by 1.8 nm are observed. The decay of triphenylene phosphorescence under these conditions is two-exponential with characteristic decay times $\tau_{1} = 0.40$ s and $\tau_{2} = 0.13$ s. The contribution of the component damping with $\tau_{1}$ to the total intensity increases with the allocation of the short-wave section of the 0--0 band. The contribution of the component damping with $\tau_{2}$ increases with the allocation of the long-wave portion of the 0-0 band. An increase in the contribution of the component with $\tau_{2}$ is also observed with monochromatic laser excitation in comparison with broadband excitation. Based on these results, it was concluded that there are two spatially separated emission centers with different probabilities of deactivation of triplet excitations of triphenylene molecules. The interpretation of the results is based on the generally accepted literature provisions that halogen atoms (chlorine, bromine, iodine) increase the probability of spin forbidden and symmetry transitions in highly symmetric molecules such as triphenylene (symmetry type D$_{3h})$ and coronene (symmetry type D$_{6h})$. Based on a comparison of changes in the relative intensity of the 0-0 band of centers with $\tau_{1}$ and $\tau_{2}$, it was concluded that external heavy atoms (bromine) to a greater extent enhance the symmetry-forbidden transitions of centers with $\tau_{1}$ than with $\tau_{2}$. The faster attenuation of the phosphorescence of centers with $\tau_{2}$ than of centers with $\tau_{1}$ is due to a greater degree to an increase in their triplet - singlet transition forbidden along the spin.

New non-conventional lithocholic acid derivatives: synthesis and characterisations for mesogenic properties

ABSTRACT The synthesis and characterisations of bulky lithocholic acid derivatives of triphenylene, pyrene, cholesterol and other rod-shaped molecules are described. All compounds are non-mesogenic, except azo-based compound that shows monotonically Smectic A mesophase. The new chemical structures were characterised by IR, 1H-nuclear magnetic resonance and microelemental analysis techniques. Thermal investigations and mesophase characterisations for all the compounds were carried out by the combination of differential scanning calorimetry, polarised optical microscope and X-ray analysis. The effects of various terminal cores connecting to middle lithocholic acid on liquid crystal properties with its structurally related compounds were discussed.

Triphenylene adsorption on Cu(111) and relevant graphene self-assembly**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFB0503100) and the National Natural Science Foundation of China (Grant No. 11790313).

Investigations on adsorption behavior of triphenylene (TP) and subsequent graphene self-assembly on Cu(111) were carried out mainly by using scanning tunneling microscopy (STM). At monolayer coverage, TP molecules formed a long-range ordered adsorption structure on Cu(111) with an uniform orientation. Graphene self-assembly on the Cu(111) substrate with TP molecules as precursor was achieved by annealing the sample, and a large-scale graphene overlayer was successfully captured after the sample annealing up to 1000 K. Three different Moiré patterns generated from relative rotational disorders between the graphene overlayer and the Cu(111) substrate were observed, one with 4° rotation between the graphene overlayer and the Cu(111) substrate with a periodicity of 2.93 nm, another with 7° rotation and 2.15 nm of the size of the Moiré supercell, and the third with 10° rotation with a periodicity of 1.35 nm.

Adsorption behavior of triphenylene on Ru(0001) investigated by scanning tunneling microscopy**Project supported by the National Key Research and Development Program of China (Grant No. 2017YFB0503100) and the National Natural Science Foundation of China (Grant No. 11790313).

As a representative of small aromatic molecules, triphenylene (TP) has markedly high carrier mobility and is an ideal precursor for building graphene nanostructures. We mainly investigated the adsorption behavior of TP molecules on Ru(0001) by using scanning tunneling microscopy (STM). In submonolayer regime, TP molecules are randomly dispersed on Ru(0001) and the TP overlayer can be thoroughly dehydrogenated and converted into graphene islands at 700 K. Due to weak interaction between TP molecules and graphene, the grooves formed among graphene islands have confinement effect on TP molecules. TP adopts a flat-lying adsorption mode and has two adsorption configurations with the 3-fold molecular axis aligned almost parallel or antiparallel to the 00] direction of the substrate. At TP coverages of 0.6 monolayer (ML) and 0.8 ML, the orientational distributions of the two adsorption configurations are equal. At about 1.0 ML, we find the coexistence of locally ordered and disordered phases. The ordered phase includes two sets of different superstructures with the symmetries of and p(4×4), respectively. The adsorption behavior of TP on Ru(0001) can be attributed to the delicate balance between molecule–substrate and molecule–molecule interactions.

Subsurface-Controlled Angular Rotation: Triphenylene Molecules on Au(111) Substrates

Molecular self-assembly can be used for the bottom-up fabrication of nanoscale electronic devices. For this, polycyclic aromatic hydrocarbons are particularly suited due to their extended π-system. Besides, these compounds can serve as precursors for fabricating graphene-like material. To design future electronic devices it is essential to be able to reproducibly predict the structure formation of these molecules after adsorption on solid surfaces. Here we studied the self-assembly of triphenylene molecules on a reconstructed Au(111) substrate in the submonolayer regime by scanning tunneling microscopy. Only two different orientations of the planar adsorbed molecules are observed. At intermediate coverages self-assembly is mainly determined by repulsive molecule–molecule interactions, leading to a one-to-one ratio of molecular orientations. At 1.0 monolayer coverage, however, a reorientation into close-packed domains occurs, which significantly shifts the ratio of molecular orientations. It is found that ...

Alignment of Palladium Complexes into Columnar Liquid Crystals Driven by Peripheral Triphenylene Substituents

A new triphenylene-imine (ImH) and its ortho-palladated complexes (μ-X)2[Pd2Im2] (X = CH3COO(-), Cl(-), Br(-)), (μ-Cl)(μ-SCnH2n+1)[Pd2Im2] (n = 6, 12), [PdIm(acac)] [PdIm Cl(CNC6H4OC12H25)], [PdImCl(CNC6H3(OC12H25)2)], and [PdImCl(CNC6H2(OC12H25)3)] have been prepared. The free imine ligand is not a liquid crystal, but most ortho-metalated dinuclear palladium complexes and the mononuclear trialkoxyphenyl isocyanide derivative display columnar mesophases at temperatures close to ambient. For the dimeric complexes the mesophase obtained is always columnar rectangular (Colr), with an uncommon structure: the dimeric triphenylene-Pd complex-triphenylene molecules give rise to a triple-column stacking consisting of two columns of stacked triphenylene groups connected to a central column formed by stacking of two ortho-palladated dimeric moieties. For the trialkoxyphenyl isocyanide derivative a related polymer-like arrangement of columns alternating stacking of triphenylenes with stacking of two ortho-palladated dimeric moieties is found. The mesophase structure is columnar oblique (Colob). The free imine and all palladium complexes exhibit fluorescence at room temperature in dichloromethane solution, associated with the triphenylene core.

Dynamics of Discotic Fluoroalkylated Triphenylene Molecules Studied by Proton NMR Relaxometry

The Larmor frequency and temperature dependence of the proton nuclear magnetic resonance (NMR) spin-lattice relaxation time was measured in the isotropic and columnar phases of both chain-end fluorinated triphenylene disk-like and fully hydrogenated molecules. In the columnar phase, the results are interpreted in terms of the collective motions, due to the deformations of the columns, and individual molecular translational self-diffusion displacements and rotations/reorientacions. In the isotropic phase, local molecular motions and order fluctuations as a pretransitional effect were considered. The activation energies of the molecular motions of the partially fluorinated molecule were found to be higher than those corresponding to the hydrocarbon homologue. Our findings show a clear difference in the relaxation dispersion between the two liquid crystals homologues. In particular it is observed that the columnar undulations have a much stronger contribution to the relaxation rate in the low frequency regime in the case of the fully hydrogenated triphenylene. The effect of fluorination of the pheripheral chain enhances the columnar mesophase's stability.

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.

Donor/acceptor complex of triphenylene and trinitrotoluene on Au(111): a scanning tunneling microscopy study

The co-adsorption of trinitrotoluene (TNT), a typical π-electron acceptor, and triphenylene (TP), a typical π-electron donor, on a Au(111) surface was investigated by in situ Electrochemical Scanning Tunneling Microscopy (ECSTM). DFT calculations proved that parallelly stacked and well-overlapped TP and TNT molecules can form Donor-Acceptor dyads through intermolecular π-π charge transfer, which agree well with the experimental results in the present work.

Theoretical modeling of influence of the structural disorder on the charge carrier mobility in triphenylene stacks

The tight-binding Hamiltonian is used to describe the charge carrier transport in a stack of triphenylene molecules. The influence of different levels of structural disorder on the on-stack charge carrier mobility is discussed. Structural disorder simulation considers three geometrical parameters: the distance between molecular planes, the twist angle around molecule symmetry axis, and the lateral slide in the direction perpendicular to the stack axis. The calculated values of the charge carrier mobility are compared with experimental data.

Coadsorption‐Induced Reconstruction of Supramolecular Assembly Characteristics

A host supramolecular structure consisting of bis-(2,2':6',2"-terpyridine)-4'-oxyhexadecane (BT-O-C16) is shown to respond to coadsorbed molecules in dramatic ways, as observed by scanning tunneling microscopy (STM) on a highly oriented pyrolytic graphite (HOPG) surface under ambient conditions. Interestingly, the lattice parameter of the triphenylene-filled complex differs significantly from that of the coronene-filled one, although the triphenylene and coronene molecules are nearly the same size. The STM study and density functional theory calculations reveal that intermolecular hydrogen-bond interactions play an essential role in forming the assembly structures. The different electronic properties of coronene and triphenylene molecules are responsible for the difference in lattice parameters and consequently for the difference in filling behaviors in the coronene/BT-O-C16 and triphenylene/BT-O-C16 binary systems.

Core charge distribution and self assembly of columnar phases: the case of triphenylenes and azatriphenylenes

BackgroundThe relation betweeen the structure of discotic molecules and columnar properties, a crucial point for the realization of new advanced materials, is still largely unknown. A paradigmatic case is that hexa-alkyl-thio substituted triphenylenes present mesogenic behavior while the corresponding azatriphenylenes, similar in shape and chemical structure, but with a different core charge distribution, do not form any liquid crystalline mesophase. This study is aimed at investigating, with the help of computer simulations techniques, the effects on phase behaviour of changes of the charge distribution in the discotic core.ResultsWe described the shape and the pair, dispersive and electrostatic, interactions of hexa alkyl triphenylenes by uniaxial Gay-Berne discs with embedded point charges. Gay-Berne parameters were deduced by fitting the dispersive energies obtained from an atomistic molecular dynamics simulation of a small sample of hexa-octyl-thio triphenylene molecules in columnar phase, while a genetic algorithm was used to get a minimal set of point charges that properly reproduces the ab anitio electrostatic potential. We performed Monte Carlo simulations of three molecular models: the pure Gay-Berne disc, used as a reference, the Gay-Berne disc with hexa-thio triphenylene point charges, the Gay-Berne disc with hexa-thio azatriphenylene point charges. The phase diagram of the pure model evidences a rich polymorphism, with isotropic, columnar and crystalline phases at low pressure, and the appearance of nematic phase at higher pressure.ConclusionWe found that the intermolecular electrostatic potential among the cores is fundamental in sta-bilizing/destabilizing columnar phases; in particular the triphenylene charge distribution stabilizes the columnar structure, while the azatriphenylene distribution suppresses its formation in favor of the nematic phase. We believe the present model could be successfully employed as the basis for coarse-grained level simulations of a wider class of triphenylene derivatives.

Self‐assembly of liquid crystalline triphenylene–oligo(ethylene oxide)–triphenylene molecules and their complexes with lithium triflate

Mesomorphic dimeric molecules consisting of discotic triphenylene rigid units and flexible ethylene oxide spacers have been prepared. The liquid crystalline behaviour is greatly dependent on the length of the ethylene oxide chains. The miscibility and phase behaviour have been examined for mixtures of the materials with lithium triflate.

The stability of columns comprising alternating triphenylene and hexaphenyltriphenylene molecules: variations in the structure of the hexaphenyltriphenylene component

Previous investigations of complementary polytopic interaction (CPI) columnar mesophases, in which the columns are built up of alternating hexaalkoxytriphenylene (HAT) and hexaphenyltriphenylene (PTP) molecules, concentrated mainly on the effect of variations in the structure of the HAT component. This investigation is concerned with the effect of variations in the structure of the PTP component and, in particular, variations in the position of an alkoxy side chain in the phenyl ring. Stable columnar mesophases are obtained when a hexyloxy substituent is placed in the meta‐ or para‐position but not in the ortho‐position. In the case of the meta‐ and para‐substituted systems, the two‐component CPI columnar phases are stable over a considerably larger temperature range than the one‐component HAT systems. The evidence suggests that unfavourable PTP/PTP stacking is as much a driving force for the formation of these mixed stacks as is favourable PTP/HAT stacking, but both need to be explained in terms of the sum of atomically dispersed van der Waals and coulombic interactions. On cooling from the isotropic into the Colh phase, the columnar phase based on a 1:1 mixture of hexakis(hexyloxy)tripenylene and the meta‐hexyloxy‐substituted PTP gives an unusual texture consisting of ‘viking‐axe’‐shaped structures.

Spacer Length Controlled Oblique-Columnar to Lamello-Columnar Mesophase Transition in Liquid Crystalline DNA−Discotic Cationic Lipid Complexes

Asymmetric triphenylene imidazolium salts with spacer lengths of C5, C8, and C11 were successfully synthesized. DNA complexation with these cationic discotic lipids was achieved by mixing DNA and triphenylene imidazolium salts in aqueous solutions. The molecular composition of the complexes in the bulk was quantitatively determined using Fourier transform infrared (FTIR) spectroscopy; the ratio of negative phosphate groups to positive imidazolium salt ranged from 1.4 to 2.0 for different discotic cationic lipids. The columnar liquid crystalline morphology was characterized by polarized light microscopy, X-ray diffraction (XRD), and transmission electron microscopy. When the spacer length of the triphenylene imidazolium salts increased from C5 to C8 and C11, a morphological transition from an oblique-columnar (Colo) phase to lamello-columnar (ColL) phases was observed. From detailed XRD results, the face-to-face interdisk spacing in a triphenylene column (0.35 nm) was similar to the period of hydrogen-bonded pairs in DNA (0.34 nm), suggesting a 1:1 complexation between the phosphate group and the imidazolium salt. The higher phosphate/imidazolium salt ratio (1.4−2.0) determined by FTIR suggested that the DNA chains were partially complexed due to rapid precipitation of the complexes upon mixing the two components in aqueous solutions. The columnar stacking of the triphenylene discotic molecules destroyed the helical conformation in the double-strand DNA, as evidenced by a circular dichroism study. When the semirigid DNA molecules were replaced with flexible total RNA, columnar liquid crystalline self-assembly of the triphenylene molecules in the complexes disappeared, and only a lamellar morphology with random discotic triphenylenes sandwiched between neighboring RNA layers was observed.