Triphenylene Research Articles

Crafting Near‐Infrared Photonics via the Programmable Assembly of Organic Heterostructures at Multiscale Level

AbstractOrganic single crystals with near‐infrared (NIR) emission demonstrate their excellent optical communications from well photonic confinement and low optical waveguide loss, which are considered as competitive candidates toward advanced optoelectronics. However, the increasingly diverse and sophisticated application demands result in the complicated design of NIR devices, which is hardly realized solely by the intrinsic properties of individual crystals. Herein, a programmable assembly strategy is presented to fabricate organic heterostructures. Triphenylene (TP), pyrene (Py) and 7,7,8,8‐tetracyanoquinodimethane (TCNQ) are primary selected to prepared organic cocrystals with narrow band gap and near‐infrared emission. Importantly, the charge‐transfer alloy with tunable emission from 700 nm to 850 nm and branched heterostructures with multichannel characteristics are prepared from these organic cocrystals by following the growth kinetics process at molecular level and lattice matching principle at structural level, respectively. Theses prepared heterostructures exhibit optical logic operation capabilities, which can serve as optical modulators. This work provides new insights into the manufacturing of organic NIR heterostructures applied in advanced optoelectronics.

Organic electronic applications and charge transport mechanism in novel discotic liquid crystals

ABSTRACTTriphenylene-based pentaalkynylbenzene dyads and naphthophenanthridine derivativediscotic mesogens have been proven a backbone-like utility for modern optoelectronic applications. Herein, we present the charge transport and organic electronic applications of naphthophenanthridine derivatives and a dimer composed of pentaalkynylbenzene (PA) and triphenylene (TP) discotic liquid crystals (DLCs). Naphthophenanthridine derivatives exhibit a hexagonal columnar (Colh) phase; whereas, triphenylene-pentaalkynylbenzene dyads show a columnar centred rectangular (Colr) phase and transform into Colh phase on doping the pure compounds with an electron-acceptor 2,4,7-trinitrofluorenone (TNF) in a 2:1 TNF/compound ratio. The ambipolar charge transport behaviour of the compounds mentioned above has been investigated by the time-of-flight technique. Naphthophenanthridine derivative renders an ambipolar charge transport, showing temperature-independent electron and hole mobility of the order of 3 × 10−4 cm2/Vs; whereas, TP-PA dimer yields an ambipolar charge carrier mobility of order 10−3 cm2/Vs. The phenazine-fused triphenylene DLC shows unipolar hole mobility of the order of 10−4 cm2/Vs; whereas, hydrogen-bonded Hpz-C9-TP DLCs exhibit ambipolar charge mobility of the order of 10−2 cm2/Vs. The high ambipolar charge carrier mobility in the investigated DLC compounds makes them suitable for fabricating organic semiconducting electronic devices.

Multiplex SERS detection of polycyclic aromatic hydrocarbon (PAH) pollutants in water samples using gold nanostars and machine learning analysis.

Polycyclic aromatic hydrocarbons (PAHs) have attracted a lot of environmental concern because of their carcinogenic and mutagenic properties, and the fact they can easily contaminate natural resources such as drinking water and river water. This study presents a simple and sensitive point-of-care SERS detection of PAHs combined with machine learning algorithms to predict the PAH content more precisely and accurately in real-life samples such as drinking water and river water. We first synthesized multibranched sharp-spiked surfactant-free gold nanostars (GNSs) that can generate strong surface-enhanced Raman scattering (SERS) signals, which were further coated with cetyltrimethylammonium bromide (CTAB) for long-term stability of the GNSs as well as to trap PAHs. We utilized CTAB-capped GNSs for solution-based 'mix and detect' SERS sensing of various PAHs including pyrene (PY), nitro-pyrene (NP), anthracene (ANT), benzo[a]pyrene (BAP), and triphenylene (TP) spiked in drinking water and river water using a portable Raman module. Very low limits of detection (LOD) were achieved in the nanomolar range for the PAHs investigated. More importantly, the detected SERS signal was reproducible for over 90 days after synthesis. Furthermore, we analyzed the SERS data using artificial intelligence (AI) with machine learning algorithms based on the convolutional neural network (CNN) model in order to discriminate the PAHs in samples more precisely and accurately. Using a CNN classification model, we achieved a high prediction accuracy of 90% in the nanomolar detection range and an f1 score (harmonic mean of precision and recall) of 94%, and using a CNN regression model, achieved an RMSEconc = 1.07 × 10-1 μM. Overall, our SERS platform can be effectively and efficiently used for the accurate detection of PAHs in real-life samples, thus opening up a new, sensitive, selective, and practical approach for point-of-need SERS diagnosis of small molecules in complex practical environments.

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.

A DFT study on M3O (M = Li & Na) doped triphenylene and its amino-, hydroxy- and thiol-functionalized quantum dots for triggering remarkable nonlinear optical properties and ultra-deep transparency in ultraviolet region

Motivated by the excellent geometric and electronic properties of recently reported triphenylene (TP), for the first time, we studied the nonlinear optical responses of superalkalis (Li3O and Na3O) doped triphenylene and amino (HATP), hydroxy (HHTP) and thiol (HTTP) functionalized quantum dots by using density functional theory. The geometric stabilities of eight reported complexes are measured through the interaction energies at ωB97XD/6-31+G(d,p) level of theory. Our results reveal that Li3[email protected] and Na3[email protected] complexes are highly stable with the interaction energies of −60.36 and −57.26 kcal/mol, respectively. The HOMO-LUMO energy gaps of TP, HATP, HHTP and HTTP are significantly varied upon complexation with M3O which is evident by the strong charge transfer from excess electron donor superalkalis (M3O) to the surfaces. However, the π back donation is more pronounced in M3[email protected] complexes, revealed by the negative value of CHELPG charge transfer on M3O. Due to the donation and back donation of charges between M3O and HATP, the significantly high first static hyperpolarizability (βo) and its projection to dipole moment (βvec) are computed for M3[email protected] complexes. The βo of Li3[email protected] and Na3[email protected] complexes are 3 × 104 au. The βo of Na3[email protected] complex is surprisingly high (1 × 105 au) which is justified by the two-level model. Moreover, the NLO responses of co-doped Li3O/Na3O and mixed functional groups TP-quantum dots are also computed. Among them, the maximum βo (5 × 104) is observed for the Na3[email protected] complex. Finally, the TD-DFT calculations reveal that the reported complexes show excellent transparency in the ultraviolet region especially M3[email protected] and Na3[email protected] complexes.

Atmospheric Occurrence of Particle-associated Nitrotriphenylenes via Gas-phase Radical-initiated Reactions Observed in South Osaka, Japan

Nitrotriphenylenes (NTPs), which include the highly mutagenic isomer 2-nitrotriphenylene (2-NTP), have been detected in airborne particles. From a public hygienic point of view, it is necessary to study the environmental occurrence of NTPs in detail. In this study, concentrations of five nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) including NTPs in airborne particles and of nitrogen oxides (NOx; NO+NO2) and carbon monoxide (CO), at a location in South Osaka, Japan, were measured at 3 h intervals. It was found that the diurnal variations in the concentrations of 1-nitropyrene (1-NP), NOx, and CO were similar, being high early in the morning and late in the evening. This finding indicates that the occurrence of 1-NP is affected significantly by primary emissions, particularly by automotive emissions. The concentration change in 1-nitrotriphenylene was similar to that of 2-nitropyrene produced by an atmospheric OH radicalinitiated reaction. On the contrary, the variations in the concentrations of 2-nitrofluoranthene (2-NF) and 2-NTP were significantly different from those of the other nitro-PAHs, i.e., their concentrations increased during the nighttime, suggesting that neither 2-NF nor 2-NTP was emitted from the primary sources, but were formed via the NO3 radicalinitiated nitration of the parent fluoranthene and triphenylene (TP) in the atmosphere. Based on the ambient concentration of 2-NTP and the reported rate constant for the reaction of TP with NO3 radicals, the yield of 2-NTP from the gas-phase NO3 radical-initiated reaction of TP was estimated to be 23%.

Triphenylene and tetracene based porous sheet: Stability and electronic properties

Inspired by the experimental advances in synthesizing triphenylene (TP)-graphdiyne monolayer and tetracene (T), we use TP as node and T as linker to construct a porous 2D TP-T sheet. By using density functional theory, we find that the TP-T sheet is stable and exhibits a direct band gap of 2.1 eV, which can be tuned in the range of 0.55–2.08 eV through various techniques including uniaxial strain, doping with B, N, P, Si, Ge atoms, substituting hydrogens with fluorine atoms at different positions, and stacking the sheet in different configurations. Especially, the B-, P-, and Ge-doped TP-T sheets show a narrow band gap of 1.58, 1.53, and 1.08 eV, respectively. Moreover, fluorine-substituted sheets are significantly more stable than the hydrogen-bonded TP-T sheet, and the band gap changes with F-content and configuration, exhibiting flexibility in tuning the stability and properties.

Star-shaped oligomers with truxenone centre and triphenylene branches: mesomorphism, optical and electronic properties

ABSTRACT Three star-shaped oligomers with an electron-deficient truxenone (TrO) as the central core and three electron-rich triphenylenes (TP) as the peripheral arms were prepared, in which the triphenylenes groups are, respectively, connected to the central truxenone core at 2, 7 and 12 positions through a highly flexible O(CH2)nO (n = 6,8,10) polymethylene chain. All these triphenylene-armed oligomers TrO[O(CH2)nOTP]3 (n = 6,8,10) exhibit liquid crystalline over broad mesophase ranges including room temperature. Oligomer TrO[O(CH2)6OTP]3 exhibit a rectangular columnar mesophase, while others with the linkage longer show a hexagonal columnar mesophase. This modulation of phase behaviours was demonstrated to be generated by steric perturbations introduced between the three decyloxy substituents in central truxenone core and the linkages with different lengths, which cause the disturbance of the intracolumnar structure and influence the degree of ordering in columnar phases. No new electronic absorption except for the usual bands of the individual truxenone or triphenylene part was observed in dichloromethane solution of TrO[O(CH2)6OTP]3 . However, two new emission peaks emerged and the intensity and position of the emission peaks were found to exhibit pronounced changes upon concentration variation, which can be attributed to the formation of intermolecular excimers.

Effect of grafting density on the self-assembly of side-chain discotic liquid crystalline polymers with triphenylene discogens.

The self-assembly of triphenylene (TP)-based side-chain discotic liquid crystalline polymers (SDLCPs) with different grafting densities was investigated by using the dissipative particle dynamics (DPD) method. We explored the coupling effect between the main chain and the side-chain TP discogens with various length alkyl tails, and how the rigidity of the main chain, grafting density and spacer lengths affect the self-assembled morphologies of SDLCPs. By changing the above factors, we have obtained nine phases. It is deduced that a moderate grafting density, a polymer backbone with sufficient length and alkyl tails with medium length ensure SDLCPs form ordered columnar mesophases. It is worth noting that double columnar phases (Colne-Col and Colh-Col) were obtained with high grafting densities and sufficiently long backbones. All these results provide an effective basis and helpful guidance for the in-depth research of such kinds of fascinating organic semiconducting materials, SDLCPs, from the perspective of grafting density.

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.

Charge‐Transport Properties of F6TNAP‐Based Charge‐Transfer Cocrystals

AbstractThe crystal structures of the charge‐transfer (CT) cocrystals formed by the π‐electron acceptor 1,3,4,5,7,8‐hexafluoro‐11,11,12,12‐tetracyanonaphtho‐2,6‐quinodimethane (F6TNAP) with the planar π‐electron‐donor molecules triphenylene (TP), benzo[b]benzo[4,5]thieno[2,3‐d]thiophene (BTBT), benzo[1,2‐b:4,5‐b′]dithiophene (BDT), pyrene (PY), anthracene (ANT), and carbazole (CBZ) have been determined using single‐crystal X‐ray diffraction (SCXRD), along with those of two polymorphs of F6TNAP. All six cocrystals exhibit 1:1 donor/acceptor stoichiometry and adopt mixed‐stacking motifs. Cocrystals based on BTBT and CBZ π‐electron donor molecules exhibit brickwork packing, while the other four CT cocrystals show herringbone‐type crystal packing. Infrared spectroscopy, molecular geometries determined by SCXRD, and electronic structure calculations indicate that the extent of ground‐state CT in each cocrystal is small. Density functional theory calculations predict large conduction bandwidths and, consequently, low effective masses for electrons for all six CT cocrystals, while the TP‐, BDT‐, and PY‐based cocrystals are also predicted to have large valence bandwidths and low effective masses for holes. Charge‐carrier mobility values are obtained from space‐charge limited current (SCLC) measurements and field‐effect transistor measurements, with values exceeding 1 cm2 V−1 s1 being estimated from SCLC measurements for BTBT:F6TNAP and CBZ:F6TNAP cocrystals.

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...

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.

Fluorination-Induced Evolution of Columnar Packing in Fluorous Triphenylenes and Benzotriphenylenes.

Use of D3h -symmetrical triphenylene (TRPH) as a substrate for high-temperature radical reactions with C4 F8 I2 under varying conditions resulted in the introduction of four types of fluorinated substituents: ω-C4 F8 H, c-C4 F8 , c-C4 F4 , and c-C4 HF3 . In contrast to the previous work on direct (poly)substitutions with RF groups in polycyclic aromatic hydrocarbons (PAHs), in this work regiospecificity, selectivity, and high yield were achieved for TRPH(C4 F8 ) and TRPH(C4 F8 )3 . New single-crystal structural data for seven compounds combined with literature crystallographic data allowed for the first detailed and precise analysis of the effects of fluorous substituent types, their number, and their position(s) on the TRPH core on the solid-state packing, and more specifically, the degree of π-π overlap between neighboring molecules, which is linked to charge transport properties. Comparison of isostructural partially fluorinated benzotriphenylenes, 2,3-TRPH(C4 F4 ) and 2,3-TRPH(C4 HF3 ), revealed an unexpectedly large (30 %) drop of π-π overlap, when only one fluorine atom was replaced with the hydrogen atom in a C4 F4 moiety. Theoretical and potentially practical implications of this work may include further testing and elaboration of computational methods describing solid-state interactions and predictions of transport properties of organic semiconductors, and further advances in the molecular design of high-performing TRPH-based organic materials and supramolecular architectures for organic optoelectronics.

Ultralong Organic Phosphorescence in the Solid State: The Case of Triphenylene Cocrystals with Halo- and Dihalo-penta/tetrafluorobenzene

The polycyclic aromatic hydrocarbon (PAH) triphenylene (TP) has been reacted with halo-pentafluorobenzene (XF5, X = Br, I) and 1,4-dihalo-tetrafluorobenzene (X2F4, X = Br, I) to yield the corresponding cocrystals TP·BrF5, TP·Br2F4, TP·IF5, and TP·I2F4 form I. These materials have been synthesized by dissolving TP into an excess of liquid or molten coformer, and single crystals have been grown via seeding chloroform solutions. They have been fully characterized by a combination of techniques including X-ray diffraction, Raman spectroscopy, and luminescence spectroscopy in the solid state. TP·I2F4 form I was found to undergo a single-crystal to single-crystal (SCSC) polymorphic phase transition induced by temperature (when cooled down to 100 K) leading to the new form TP·I2F4 form II, which is transformed back into the first structure when brought again at RT. This behavior was confirmed also by Raman spectroscopy. Upon cocrystallization and as a result of the external heavy atom effect, all crystalline mat...

Electrical and electrochemical properties of triphenylene based lithium solvated electron solutions

Conductivity and open circuit potentials of lithium solvated electron solutions (Li SESs) based on triphenylene (TRI) in tetrahydrofuran (THF) were studied. It was found that those solutions with Li:TRI ratio >0.5 demonstrate much higher conductivity comparing to naphthalene based Li SES of same concentration, which can be related to TRI π-stacking properties. Based on the values of open circuit voltage in a half-cell, the values of entropy and enthalpy change were calculated for the Li:TRI ratios of 2:1 and 4:1. The value of ΔS for Li4.0 (TRI) (THF)123 is higher than the one for naphthalene based Li SES with Li:PAH ratio = 1:1. The obtained values are much higher than those for solid state electrodes used in lithium ion batteries. Based on quantum chemical modeling of lithium-triphenylene interactions, it was shown that the unusually high values of conductivity could be related to the formation of a dimeric conductive complex.

An Iron-Based Catalyst with Multiple Active Components Synergetically Improved Electrochemical Performance for Oxygen Reduction Reaction

Lack of highly active and stable non-precious metal catalysts (NPMCs) as an alternative to Pt for oxygen reduction reaction (ORR) in the application of zinc-air batteries and proton-exchange membrane fuel cells (PEMFCs) significantly hinders the commercialization of these energy devices. Herein, we synthesize a new type of catalyst composed of nitrogen-coordinated and carbon-embedded metal (Fe-N/Fe3C/Fe/C) by pyrolyzing a precursor at 800 °C under argon atmosphere, and the precursor is obtained by heating a mixture of the tri (dipyrido [3,2-a:2′,3′-c] phenazinyl) phenylene and FeSO4 at 160 °C in a Teflon-lined stainless autoclave. The resultant Fe-N/Fe3C/Fe/C-800 exhibits the highest activity for the ORR with onset and half-wave potentials of 1.00 and 0.82 V in 0.1 M KOH, respectively. Furthermore, it also shows a potential ORR activity in 0.1 M HClO4, which is promising for the application in commercial PEMFCs. Most importantly, Fe-N/Fe3C/Fe/C-800 exhibits a comparable electrochemical performance to Pt/C for the application in zinc-air battery. The specific capacity approaches 700 mAh·g−1, and the maximum power density is also comparable to that of Pt/C at the current density of 200 mA·cm−2. The work opens up a simple strategy to prepare ORR electrocatalyts for zinc-air battery and PEMFCs.

Density Functional Theory Modeling of Solid-State Nuclear Magnetic Resonances for Polycyclic Aromatic Hydrocarbons

We acknowledge funding from C. Madrid (Grant S2013/MIT-2753), MINECO (Grants MAT2014-54231, MAT2016-78625-C2-2P, MAT2016-78362-C4-2-R, and FIS2015-6422-C2-1-P), EU (Grant ERC-2013-SYG-610256 NANOCOSMOS), Generalitat Valenciana (Grant PROMETEO/2017/139); the University of Alicante and computing resources from CTI-CSIC.

Impact of C–H···X (X = F, N) and π–π Interactions on Tuning the Degree of Charge Transfer in F6TNAP-Based Organic Binary Compound Single Crystals

Single crystals of four new charge transfer compounds, triphenylene (TP)-1,3,4,5,7,8-hexafluorotetracyanonaphthoquinodimethane (F6TNAP), pyrene-F6TNAP, phenanthrene (PA)-F6TNAP, and naphtho[1,2-b:5,6-b’]dithiophene (NDT)-F6TNAP, with needle-like morphologies and dark color were grown by chemical vapor transport. The influence of C–H···X (X = F, N) interactions as well π–π interactions on the degree of charge transfer (DCT) in these compounds was investigated. The results indicate that the DCT is proportional to the interplanar D–A distance along the π–π interaction direction in TP-F6TNAP, pyrene-F6TNAP, and PA-F6TNAP single crystals. With the decreasing of the D–A interplanar distance from 3.3560 A of TP-F6TNAP to 3.3254 A of PA-F6TNAP, the DCT is significantly increased from 0.03 ± 0.02 of TP-F6TNAP to 0.26 ± 0.03 of PA-F6TNAP, showing the strong relationship between π–π interactions and the DCT. In addition to π–π interactions, a stronger C–H···F interaction (C–H···F bond length: 2.3689 A) is observed i...

A chemically-responsive bis-acridinium receptor

The recognition and the chemical-response properties of a bis-acridinium triphenylene receptor were investigated.