Triphenylamine Core Research Articles

Deciphering the Multifarious Charge-Transport Behaviour of Crystalline Propeller-Shaped Triphenylamine Analogues.

A collection of para-substituted propeller-shaped triphenylamine (TPA) derivatives have been computationally investigated for charge-transport characteristics exhibited by the derivatives by using the Marcus-Hush formalism. The various substituents chosen herein, with features that range from electron withdrawing to electron donating in nature, play a key role in defining the reorganisation energy and electronic coupling properties of the TPA derivatives. The TPA moiety is expected to possess weak electronic coupling on the basis of poor orbital overlap upon aggregation, owing to the restriction imposed by the propeller shape of the TPA core. However, the substituent groups attached to the TPA core can significantly dictate the crystal-packing motif of the TPA derivatives, wherein the variety of noncovalent intermolecular interactions subsequently generated drive the packing arrangement and influence electronic coupling between the neighbouring orbitals. Intermolecular interactions in the crystalline architecture of TPA derivatives were probed by using Hirshfeld and quantum theory of atoms-in-molecules techniques. Furthermore, symmetry-adapted perturbation theory analysis of the TPA analogues has revealed that a periodic arrangement of energetically stable dimers with significant electronic coupling is essential to contribute high charge-carrier mobility to the overall crystal.

Synthesis and applications of thieno[3,4-c]pyrrole-4,6-dione based linear to star-burst novel D–A conjugated oligomers for organic photovoltaics

A series of well-defined donor–acceptor (D–A) conjugated oligomers incorporating thieno[3,4-c]pyrrole-4,6-dione (TPD) acceptor and two symmetrical thiophene units as donor π-bridge along the axes of triphenyl amine core have been synthesized and explored in bulk heterojunction (BHJ) solar cells. Under illumination with AM 1.5 white light (100 mW/cm2), the performance of BHJ photovoltaic devices with an active layer of an electron-donor oligomeric material (TPATP1, TPATP2 or TPATP3) blended with an electron acceptor {[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) at various weight ratios has been investigated. The photovoltaic device containing the donor TPATP1 and the acceptor PC71BM at a 1:3 weight ratio exhibited the best efficiency of 1.87% with an open circuit voltage (Voc) of 0.86 V, short circuit current (Jsc) of 6.59 mA/cm2, and a fill factor (FF) of 33%. These results demonstrate that irrespective of conjugation length, tuning of materials with efficient donor and acceptor materials can enhance the optical, electrochemical and eventually the power conversion efficiency (PCE) values of BHJ solar cells. Furthermore oligomers containing TPD acceptor in different structural form have different unique contribution towards photovoltaic properties.

Synthesis, photophysical, theoretical and electroluminescence study of triphenylamine-imidazole based blue fluorophores for solution-processed organic light emitting diodes

The deep blue organic light emitting diodes (OLEDs) are necessary for solid-state lighting (SSL) and flat panel displays. In the practical application of OLEDs, high efficiencies and luminance with simple device structure, are highly desirable. Hence, we have designed and synthesized three blue (Donor-Acceptor) fluorophores with linear, bent and star-shaped molecular geometry by incorporating triphenylamine (TPA) as a hole transporting unit and imidazole as an electron transporting unite with electron withdrawing Ph-CF3 moiety at the N1 position of imidazole unit. The synthesized fluorophores were structurally characterized by Nuclear Magnetic Resonance Spectroscopy (NMR) and Mass spectroscopy. The linear-shaped fluorophore structurally characterized by single crystal X-ray diffraction. Photophysical, electrochemical and electronic (theoretical) properties of the synthesized fluorophores were systematically investigated. All the fluorophores are showing deep blue emission in DCM solution. The synthesized fluorophores are shown good quantum yield (Φ) in solution and solid phase. The structurally simple OLEDs devices were fabricated by using these fluorophores as emitters. All the fluorophores showed deep blue electroluminescence (EL) emission with good device efficiency. Among all the devices, based on TBIMTPA with a 5 wt % dopant concentration exhibited better performance in the series with a maximum luminance of 994 cd/m2, a current efficiency of 2.6 cd/A, a power efficiency of 1.0 lm/W and an EQE of 3.2% at brightness of 100 cd/m2. These results indicate that the introduction of imidazole-based accepter on the TPA core is a favorable design strategy towards deep blue emitters.

The photo-optical and electrochemical activity promoted by trifluoromethyl-substituted and ortho-catenated triphenylamine core in poly(ether-imide)s

A new series of five thermally and dimensionally stable aromatic poly(ether-imide)s consisting of an electron donating ortho-catenated triphenylamine (TPA) derivative bearing two trifluoromethyl groups and various electron-accepting phthalimide moieties were synthesized and thoroughly investigated. These polyimides display excellent organosolubility, unexpectedly even in ethanol, which allows their processing in environmentally friendly conditions. The twisting of the backbone structure induced by the ortho-catenated TPA core significantly affects their electronic properties. It was found that the CF3-substituted TPA moiety may facilitate dual intramolecular charge transfer (ICT) transitions, an aspect not highlighted yet for this class of polymers. In addition, we brought evidence for the occurrence of Förster excitation energy transfer (FRET) between the two ICT excited states that modulates the light emission toward the green-yellow spectral range, another novelty encountered at these polymers. The electron-withdrawing CF3 units directly graphthed on the triphenylamine core induced a fine-tuning of HOMO-LUMO energy levels, leading to low LUMO levels and energy band gaps. The novel characteristics endow the developed polymers with a wide application prospect, especially in the field of biology and opto-electronics.

Helicity Control of Triphenylamine‐Based Supramolecular Polymers: Correlation between Solvent Properties and Helicity in Supramolecular Gels

We describe the role of amide groups formed by achiral and chiral moieties to study supramolecular helicity at the molecular level and the correlation between helicity and solvent properties at the supramolecular level. Using circular dichroism (CD) spectroscopy, we observed the CD spectra of supramolecular gel 1, which comprised a triphenylamine (TPA) core, terpyridine, and alanine moieties, formed in various solvents. The strong positive CD signals of supramolecular gel 1 formed in organic solvents, such as chloroform, tetrahydrofuran (THF), and dichloromethane, which have low polarity and a low acceptor number, were observed at 350 nm, indicating right-handed helicity. In contrast, the negative CD signals of supramolecular gel 1 formed in mixed DMSO/water (5:1 v/v), methanol, ethanol, and n-propanol were obtained at 350 nm, indicating left-handed helicity. These findings suggest that the helicity of supramolecular gel 1 was strongly influenced by the solvent properties. Indeed, atomic force spectroscopy images showed the right- and left-handed helicity of supramolecular gel 1 formed in various organic solvents, which was pure helicity.

Terthiophene Functionalized Conjugated Triarm Polymers Containing Poly(fluorene-2,7-vinylene) Arms Having Different Cores-Synthesis and Their Unique Optical Properties.

Optical properties of three types of terthiophene (3T) functionalized conjugated triarm (star-shaped) polymers consisting of poly(9,9-di-n-octyl-fluorene-2,7-vinylene) (PFV) arms and different [2,4,6-tri(biphenyl)benzene (TBP), 1,3,5-tri(benzyl)benzene (TBB), and triphenylamine (TPA)] cores, prepared by combined olefin metathesis with Wittig coupling, have been studied. Relative intensities [increases in the higher vibronic bands, (0, 1) fluorescence (FL)] of the fully conjugated TPA-core polymers, TPA(PFV-3T)3, in the fluorescence (FL) spectra in tetrahydrofuran (toluene) solution were higher than those in the other triarm polymers, TBP(PFV-3T)3, TBB(PFV-3T)3, whereas no significant differences were observed in their UV–vis spectra; notable temperature dependences were not observed in the UV–vis and FL spectra (at −5, 25, and 55 °C). Remarkable differences were not observed in the spectra in these polymer thin films, whereas λmax values red-shifted due to the formation of J-type aggregates. The observation for the time-resolved study well corresponds to results for the steady-state fluorescence measurements. The observed unique emission by the star-shaped (triarm) polymer containing the TPA core would be assumed to be due to a difference in nature of the core (higher coplanarity) compared to that of the others.

Simple electron donor molecules based on triphenylamine and carbazole derivatives

Electron donating carbazole and triphenylamine derivatives are widely used in molecular electronic materials and in biological fluorescent or active probes. Novel easy-to access, highly substituted, electron-rich carbazole and triphenylamine compounds were designed, synthesized and characterized in photophysical and electrochemical experiments. These compounds, with an unusual D-π-D-π-D molecular design are based on carbazole and triphenylamine cores, thiophene conjugated linker and donor aromatic extremities. They showed excellent light-absorbing and emitting properties with high fluorescent quantum yield along with low oxidation potential and excellent electron donating properties. Computational calculations complete the experimental data, and enlighten about the redox and photophysical processes.

Electrosynthesis of redox-active and electrochromic polymer films from triphenylamine-cored star-shaped molecules end-capped with arylamine groups

Four starburst molecules with a triphenylamine (TPA) core through the amide group linked to the terminal triphenylamine or (N-phenyl)carbazole (NPC) unit, coded as T-3(NHCO-TPA), T-3(NHCO-NPC), T-3(CONH-TPA), and T-3(CONH-NPC), were synthesized and their electrochemistry and electropolymerization were investigated. The oxidation potential and the stability of the oxidized forms of the starbursts are affected by the orientation of amide linkage and the structure of terminal triarylamine unit. Robust polymeric films could be built onto ITO/glass surface by repetitive cyclic voltammetry (CV) of the T-3(NHCO-TPA) solution containing an electrolyte. The electrodeposited films exhibited reversible electrochemical processes and strong color changes upon electro-oxidation, which can be switched by potential modulation. The electrochromic behavior of the film was clearly interpreted on the basis of spectroelectrochemical studies. T-3(CONH-TPA) did not undergo electropolymerization effectively. T-3(CONH-NPC) also could electrochemically polymerize to polymer films upon repeated CV scans. However, their electrochromic switching stability is less than that of the polymer film from T-3(NHCO-TPA).

Triphenylamine-based allylidenemalononitrile chromophores: synthesis, and photophysical and second-order nonlinear optical properties

A series of NLO chromophores based on a mono-, di- or tri-substituted triphenylamine core and allylidenemalononitrile fragments has been designed.

Synthesis and Performance of Highly Stable Star-Shaped Polyaniline Electrochromic Materials with Triphenylamine Core

The molecular architecture of conducting polymers has a significant impact on their conjugated structure and electrochemical properties. We have investigated the influence of star-shaped structure on the electrochemical and electrochromic properties of polyaniline (PANI). Star-shaped PANI (SPANI) was prepared by copolymerization of aniline with triphenylamine (TPA) using an emulsion polymerization method. With addition of less than 4.0 mol.% TPA, the resulting SPANI exhibited good solubility in xylene with dodecylbenzenesulfonic acid (DBSA) as doping acid. The structure and thermal stability of the SPANI were characterized using Fourier-transform infrared spectroscopy, Raman spectroscopy, and thermogravimetric analysis, and the electrochemical behavior was analyzed by cyclic voltammetry (CV). The electrochromic properties of SPANI were tested using an electrochemical workstation combined with an ultraviolet–visible (UV–Vis) spectrometer. The results show that, with increasing TPA loading, the thermal stability of SPANI increased. With addition of 4.0 mol.% TPA, the weight loss of SPANI was 36.9% at 700°C, much lower than the value of 71.2% for PANI at the same temperature. The low oxidation potential and large enclosed area of the CV curves indicate that SPANI possesses higher electrochemical activity than PANI. Enhanced electrochromic properties including higher optical contrast and better electrochromic stability of SPANI were also obtained. SPANI with 1.6 mol.% TPA loading exhibited the highest optical contrast of 0.71, higher than the values of 0.58 for PANI, 0.66 for SPANI-0.4%, or 0.63 for SPANI-4.0%. Overdosing of TPA resulted in slow switching speed due to slow ion transport in short branched chains of star-shaped PANI electrochromic material. Long-term stability testing confirmed that all the SPANI-based devices exhibited better stability than the PANI-based device.

Thermally stable efficient hole transporting materials based on carbazole and triphenylamine core for red phosphorescent OLEDs

Abstract In this work, a series of hole transporting materials with carbazole and triphenylamine cores have been synthesized and characterized. In the carbazole's 3rd and 6th positions, two site tryphenylamine para positions are end capped with the same types of branching derivatives to compare the overall performances of constructed devices. All of our hole transporting materials showed good thermal stabilities without any crystallized features which expressed in higher decomposition temperature (Over 500 °C at 5% weight reduction). All synthesized materials revealed HOMO energy levels between −5.62 and −5.48 eV, which values are lying between HOMO energy values of anode and emission layer; as a result, it made an effective path for hole transportation. Higher lying LUMO values between −2.51 and −2.31 can block the electrons from adjacent layer to ensure the perfect recombination in the middle layer. Triphenylamine based HTMs indicated better performances than carbazole based HTMs. Further comparisons were done by using NPB as hole transporting material with the same red phosphorescent based OLED device. HTM2A based device IV was exhibited higher maximum current efficiency of 30.6 cd/A and higher maximum external quantum efficiency of 26.7% than reference NPB based device. Measured Hole mobility value of HTM2A with hole dominant device was 5.3 × 10 −4 cm 2 V −1 s −1 , which was better than NPB. Synthesized HTM2A would be a promising hole transporting material for various phosphorescent based OLEDs.

Contribution of excited state absorption to optical limiting properties in multi-branched structures

A series of multi-branched compounds D1–D3 combining a triphenylamine core with one, two or three benzylidene cyclopentylidene malononitrile branches, respectively, were synthesized. The linear photophysical property, photochemical stability, thermal stability, and nonlinear absorption under 1064nm pulsed lasers with pulse durations in both nanosecond and femtosecond regimes of D1–D3 were investigated. The results showed that the main optical limiting mechanism of D1–D3 under femtosecond pulses was two-photon absorption (2PA), but their excited state absorption (ESA) became the main contributor for their optical limiting behaviors under nanosecond pulses. Meanwhile, introducing a multi-branched structure has much stronger impact on the ESA spectrum of D3 than on its linear absorption spectrum compared with the monomer D1. The largest ESA cross-section of D3 was the main contributor to its enhancement of effective 2PA in nanosecond regime. Combining with its best thermal and photochemical stability, the three-branched compound D3 was proved as a good optical limiting material for 1064nm nanosecond pulsed lasers.

Synthesis, photophysical and electroluminescence studies of new triphenylamine-phenanthroimidazole based materials for organic light emitting diodes

In this work, two star-shaped small conjugated materials, namely tris(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl) amine (PIPTPA) and tris(4-(1-p-tolyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)amine (PITTPA) with donor-π-acceptor (D-π-A) structures, were designed and synthesized by combining three phenanthroimidazole arms into an triphenylamine core. A detailed photophysical, thermal, electrochemical and related properties were systematically studied. Furthermore, theoretical calculations (DFT and TD-DFT) were performed to get a better understanding of the electronic structures. Both the materials were found to exhibit high glass transition temperatures (~ 238°C) and high thermal stabilities with decomposition temperatures up to 298°C. OLEDs using these materials as emissive materials showed excellent device performance (7.42cdA−1, 5.77lmW−1, 4.14% at 100cdm−2) with green emission and low turn-on voltages. The results demonstrate that TPA integrated with phenthroimdazole plays an important role in the device performance.

Novel Dimethylmethylene-Bridged Triphenylamine-PDI Acceptor for Bulk-Heterojunction Organic Solar Cells.

A novel, star‐shaped electron acceptor, DMTPA‐PDI3, derived from a planar dimethylmethylene‐bridged triphenylamine core with three acetylene‐linked perylene diimide (PDI) units is developed as a nonfullerene acceptor for organic solar cells (OSCs). DMTPA‐PDI3 manifests significantly reduced intramolecular twisting, enabling sufficient system‐wide π‐electron delocalization leading to broadened spectral absorption and raised lowest unoccupied molecular orbital level. As a result, higher and more balanced hole and electron transport properties are observed. Active layers for OSCs comprising DMTPA‐PDI3 acceptor and PBT7‐Th donor exhibit suppressed intermolecular aggregation, giving rise to uniform nanophase network formation. These OSC devices have afforded respectably high power‐conversion efficiency of about 5%.

Building Block Dependent Morphology Modulation of Cage Nanoparticles and Recognition of Nitroaromatics.

Morphology of nanomaterials has a strong impact on their chemical/physical properties, and controlled synthesis of such materials with desirable morphology is a major challenge. This article presents the role of a building block in the morphology of organic cage particles. In this context, three organic cages (A3 X2 , B3 X2 , and C3 X2 ) were devised from triphenylamine-based dialdehydes (A-C) and a flexible triamine (X) by utilizing dynamic imine chemistry. All of the synthesized cages were characterized by various spectroscopic techniques, which suggested the formation of [3+2] assembled architectures. Though the cages are isostructural, structural variation in the aldehyde building blocks imparted by the incorporation of phenyl moieties into the triphenylamine core produces morphologically diverse cage particles, as indicated by SEM. The synthesized cages were found to be fluorescent; the reduced analogue of cage A3 X2 (A3 X2r ) was tested to explore its use as a chemosensor for the detection of nitroaromatic explosives. The experimental findings suggest high selectivity and sensitivity of A3 X2r towards picric acid (PA) among the various nitroaromatics tested. A theoretical investigation of fluorescence quenching suggested that formation of a ground-state charge-transfer complex with a resonance energy-transfer (RET) process could be the main reason behind such selectivity of the cage towards PA.

Ar–ArF Self‐Assembly of Star‐Shaped Second‐Order Nonlinear Optical Chromophores Achieving Large Macroscopic Nonlinearities

AbstractIn this communication, a new series of multibranched second‐order nonlinear optical (NLO) chromophores T1–T3 are prepared using triphenylamine moiety as the core to link different number of pentafluorobenzene groups modified chromophores. Upon increasing the number of branched chromophore arms attached to the triphenylamine core, the NLO coefficients (d33) can be significantly improved accordingly, due to an integrated effect of enhanced site isolation and Ar–ArF self‐assembly. As a result, the star‐shaped T3 consisting of three‐branched chromophore arms realizes an impressive d33 value, up to 191.8 pm V−1, making it an excellent potential material candidate for second‐order NLO applications.

Electrochromic Properties of Novel Selenophene and Tellurophene Derivatives Based on Carbazole and Triphenylamine Core

The 2,7- and 3,6-substituted carbazole and triphenylamine chalcogenophene (Se, Te) derivatives and their electrodeposited polymers are investigated using electrochemical and UV–vis–NIR/ESR spectroelectrochemical methods. Major differences in the case of oxidation and electropolymerization behavior between monomers and related polymers are shown. Se and Te atoms do not conjugate their lone electron pairs with the π-conjugated system and therefore only increase the contribution of the quinoid form of the chalcogenophene unit. The 2,7- substituted carbazole derivatives present stronger carbazole–chalcogenophene conjugation than 3,6-substituted derivatives. One 3,6-substituted carbazole derivative and triphenylamine derived polymers were found to have promising electrochromic properties with black electrochromism.

Star‐Shaped Phenanthroimidazole‐Triphenylamine‐Based Yellow Organic Emitter for Organic Light Emitting Diodes

AbstractIn this work, new star‐shaped conjugated organic emitter, namely tris(4‐(1‐(9,9‐diethyl‐9H‐fluoren‐2‐yl)‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenyl)amine (PIFTPA) with donor‐π‐acceptor (D‐π‐A) structure, was designed and synthesized by combining three fluoren‐phenanthroimidazole arms into a triphenylamine core and characterized using 1H, 13C NMR and mass spectrometry. The detailed photophysical, thermal, electrochemical and electroluminescence properties were systematically studied. The organic emitter exhibits high glass transition temperature (230 °C) and high thermal stability with decomposition temperature. Electrochemical analysis reveals that the emitter has distinct oxidation and reduction behaviours. Furthermore, theoretical calculations (DFT) were performed to get a better understanding of the electronic structure. The OLEDs using this emitter as emissive material showed good device performance (6.45 cd/A, 4.39 lm/W, and 3.01%) with yellow emission and a low turn‐on voltage (2.87 V). The results demonstrate that TPA integrated with phenthroimdazole plays an important role in the device performance.

Poly{tris[4-(2-Thienyl)phenyl]amine} fluorescent conjugated microporous polymer for selectively sensing picric acid

Two thiophene-based and carbazole-based conjugated microporous polymers (PTPATTh and PTPATCz) with triphenylamine core structural monomers were synthesized via straight forward anhydrous ferric chloride oxidative coupling polymerization. We first explored the fluorescent sensing performance of thienyl CMPs for picric acid (PA) and investigated comparatively the porosity and fluorescence sensing property for PA/p-nitrophenol (NP). Thanks to the propeller-like structure, high porosity, extended π-conjugation and electron-rich characteristics, the both CMPs exhibited strong fluorescent emission properties and worked as fluorescent chemosensors toward electron-deficient nitroaromatic analytes. The suspension of PTPATTh and PTPATCz given rise to the high luminescence, and showed a white and yellow emission in both THF and DOX excited under 365nm using a UV lamp, respectively. Though BET surface area values and response speed of PTPATTh (594m2g−1) are lower than that of PTPATCz (894m2g−1), PTPATTh display higher selectivity for tracing PA than PTPATCz in DOX and THF. In short, the PTPATTh may be a new kind of material for detecting PA.

High triplet energy exciton blocking materials based on triphenylamine core for organic light-emitting diodes

A series of novel high triplet energy materials have been designed and synthesized from the simple starting compounds through a simple one-step Friedel–Crafts reaction by using triphenylamine and methoxy, fluoro substituted diphenylmethanoles and triphenylmethanol as the starting materials. The synthesized compounds exhibit the ionization potentials in an interval of 5.4–5.7 eV in the solid state, the wide bang-gaps of 3.6 eV and the high triplet energies of about 3.0 eV. The photophysical properties have been confirmed by DFT. The introduction of a material with the lowest ionization potential as the high triplet energy exciton blocking thin layer of the green organic light-emitting diode doubled the quantum efficiency of the device. The best fabricated green device exhibited the maximum current, power, and external quantum efficiencies of 80.1 Cd A−1 and 31.4 Lm W−1, 23.2%, respectively. The triplet-triplet annihilation and triplet-polaron quenching effects for the devices without and with exciton blocking layer have been analyzed.