Triphenylamine Derivatives Research Articles

Dioxaborin Compounds with Terminal Carbazole Groups: Enhancing Electron Acceptor in Organic Photovoltaics

AbstractThree donor−acceptor−donor dioxaborin compounds containing carbazoles as the terminal electron donor groups were synthesized. Their electronic and photovoltaic properties were compared with those of an analog with terminal triphenylamine groups. The HOMO and LUMO levels of the N‐phenylcarbazole derivative were 0.3 and 0.1 eV lower, respectively, than those of the triphenylamine analog. During the evaluation of organic photovoltaic characteristics, the N‐phenylcarbazole derivative exhibited a power conversion efficiency (PCE) of 2.06 % when combined with a conducting polymer (PTB7‐Th). Contrarily, the triphenylamine analog exhibited a PCE of 2.85 % when combined with a fullerene acceptor (PC61BM). The results showed that the N‐phenylcarbazole and triphenylamine derivatives functioned as electron acceptor and donor materials, respectively. The conversion from the electron donor to the acceptor was achieved via a slight change in the structure of the terminal donor groups of the dioxaborin compounds. This study will prove valuable for the development of nonfullerene acceptors.

Reversible mechanofluorochromic luminescence behaviors of triphenylamine-based compounds and their application in erasable writing

It is challenging and desirable to develop an effective molecular design strategy to tune mechanofluorochromic (MFC) activity in organic molecules. Herein, three triphenylamine (TPA) derivatives were synthesized to investigate the MFC properties. The inclusion of iminodibenzyl, diphenylamine and carbazolyl units into the molecules causes some changes in the molecular conformation and packing pattern, which can lead to the variation of MFC activities. Among three TPA derivatives, T1 exhibits excellent MFC performance upon grinding. In addition, the color change induced by grinding is revisable upon heating. In consideration of the good repeatability and sensitivity of MFC process, T1 is chosen to prepare the rewritable papers and can be achieved in inkless writing technology.

Comparative study on indolium-fluorophore conjugates as dual sensors for cyanide ion in aqueous media

Three derivatives of indolium ions containing different fluorophores - julolidine, triphenylamine and pyrene - are synthesized in excellent yields by a condensation reaction. These compounds exhibit excellent selectivity toward cyanide ion on both colorimetric and fluorescence modes. The lowest limits of detection at 0.65 µM on the colorimetric mode and 24 nM on the fluorescence mode are achieved from the triphenylamine derivative. Data from 1H NMR and mass analysis confirm that the selectivity involves the formation of adducts between cyanide and indolium derivatives. One of these compounds is used as a fluorescence sensor for quantitative analysis of cyanide ion in real water samples which shows high accuracy and precision.

The host–guest inclusion driven by host-stabilized charge transfer for construction of sequentially red-shifted mechanochromic system

Developing more extensive methods to understand the underlying structure-property relationship of mechanochromic luminescent molecules is demanding but remains challenging. Herein, the effect of host-guest interaction on the mechanochromic properties of organic molecules is illustrated. A series of pyridinium-functionalized triphenylamine derivatives show bathochromic-shifted emission upon mechanical stimulation. These derivatives bind to cucurbit[8]uril to form homoternary host-guest inclusion complexes through host-stabilized intermolecular charge transfer interactions. Remarkably, the homoternary complexes exhibit longer emission than that of free guests in the solid state (even longer than ground guests), and a further bathochromic-shifted emission is observed upon grinding. Additionally, a heteroternary complex constructed through the encapsulation of pyrene (donor) and pyridinium (acceptor) guest pair in cucurbit[8]uril also displays the mechanochromic luminescent property. This work not only discloses the effect of host-guest inclusion on the mechanochromic property of organic molecules, but also provides a principle and a facile way to design the sequentially red-shifted mechanochromic materials.

Highly Selective Fluorescent Sensors: Polyethylenimine Derivatives of Triphenylamine and Coumarin for GTP and ATP Interaction via Fluorescence Lifetime Imaging Microscopy.

Chemical derivatives of polyethylenimine (PEI) receptors with either triphenylamine (TPA) or 7-hydroxy-4-methyl-coumarin (Cou) form stable complexes with adenine and guanine nucleotides in water. The host-guest complex modulation is found to be based on noncovalent molecular interactions such as π-π stacking and hydrogen bonding, which are dependent on the aromatic moieties attached to the polyaminic (PEI) backbone. PEI-TPA acts as a chemosensor with a recognition driving force based on aggregation-induced emission (AIE), involving π-π interaction between the nucleic base and TPA. It detects GTP by a chelation enhancement quenching effect of fluorescence (CHEQ) with a measured logarithm stability constant, log β = 7.7. By varying the chemical characteristics of the fluorophore, as in the PEI-Cou system, the driving force for recognition changes from a π-π interaction to an electrostatic interaction. The coumarin derivative detects ATP with a log β value one order of magnitude higher than that for GTP, allowing for the selective recognition of the two nucleotides in a 100% aqueous solution. Furthermore, fluorescence lifetime imaging microscopy (FLIM) allows for a correlation between the selectivity of PEI-TPA toward nucleotides and the morphology of the structures formed upon ATP and GTP recognition. This study offers valuable insights into the design of receptors for the selective recognition of nucleotides in water.

Synthesis and properties of D-π-A triphenylamine derivatives with solvatochromism and bioimaging application

D-π-A type molecular structures often exhibit excellent photophysical properties due to intramolecular charge-transfer interactions. Herein, two donor-π-acceptor (D-π-A) type triphenylamine derivatives were designed and synthesized. These two compounds exhibited bright solid-state emission with orange-red fluorescence (compound 1, 620 nm) and near-infrared (NIR) fluorescence (compound 2, 650 nm). Moreover, the photophysical properties studies showed that these two compounds exhibited significant solvatochromism with different solvent polarity, indicating their effective intramolecular charge transfer. Furthermore, the two compounds showed remarkable aggregation-induced emission (AIE) effect, and compound 2 was more likely to form the aggregation state in the presence of less water. In addition, compared to compound 1, compound 2 only had a more sensitive response to high viscosity environments. These results indicate that the additional phenyl ring could be an alternative way to tune the fluorescence behaviors and provide a new strategy to design AIE-active and solvatochromism dyes. Finally, cell imaging experiments showed that these two compounds had the ability to be applied for bioimaging in living cells.

Interplay between Dual-State and Aggregation-Induced Emission with ESIPT Scaffolds Containing Triphenylamine Substituents: Experimental and Theoretical Studies.

We detail the synthesis of a series of fluorophores containing triphenylamine derivatives along with their photophysical, electrochemical, and electronic structure properties. These compounds include molecular structures derived from imino-phenol (anil) and hydroxybenzoxazole scaffolds originating from similar salicylaldehyde derivatives and display excited-state intramolecular proton transfer. We show that depending on the nature of the π-conjugated scaffold, different photophysical processes are observed: aggregation-induced emission or dual-state emission, with a modulation of the fluorescence color and redox properties. The photophysical properties are further rationalized with the help of ab initio calculations.

A multifunctional supramolecular assembly based on nor-seco-cucurbit[10]uril for sensing 4-hydroxyphthalonitrile and adsorbing eosin Y

Since phenolic pollutants and organic dyes do great harm to the environment and human health, it is necessary to explore efficient and low-cost methods to monitor and adsorb them respectively. Herein, a multivalent supramolecular assembly composed of triphenylamine derivatives (TPAN) and nor-seco-cucurbit[10]uril (ns-Q[10]) was designed and synthesized. The supramolecular assembly has a luminescent core and cationic N-methyl imidazole groups connected by alkyl chains, and triphenylamine derivatives (TPAN) can be combined with ns-Q[10] in a stoichiometric ratio of 2:3 to form a network multivalent assembly with yellow fluorescence enhancement. At the same time, this supramolecular assembly has been applied to supramolecular recognition of 4-Hydroxyphthalonitrile (4-HP) and Eosin Y (ESY), and it can also adsorb and remove ESY in aqueous solution. This shows that the multivalent supramolecular assembly shows good potential in industrial applications such as the emission of phenolic pollutants and the adsorption of organic dyes.

Achieving Tunable Organic Afterglow and UV Irradiation-Responsive Ultralong Room-Temperature Phosphorescence from Pyridine-Substituted Triphenylamine Derivatives.

Amorphous polymers with ultralong room-temperature phosphorescence (RTP) are highly promising for various applications. Particularly, polymer-based RTP materials with multiple functions such as color-tunability or stimulus-responsiveness are highly desirable for multilevel anti-counterfeiting but are rarely reported. Herein, we present a facile strategy to achieve a series of polymer-based RTP materials with ultralong lifetime, multicolor afterglow, and reversible response to UV irradiation by simply embedding pyridine-substituted triphenylamine derivatives into the polymer matrix poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA), respectively. Notably, the pyridine group with the capabilities of promoting intersystem crossing and forming hydrogen-bonding interactions is essential for triggering ultralong RTP from the doping PVA system, among which the doping film TPA-2Py@PVA exhibits excellent RTP property with an ultralong lifetime of 798.4ms and a high quantum yield of 15.2%. By further co-doping with the commercially available fluorescent dye, multicolor afterglow is obtained via phosphorescence energy transfer. While the doping PMMA system exhibits reversible photo-activated ultralong RTP properties under continuous UV irradiation. Finally, we demonstrate potential applications of these doping PVA and PMMA systems with ultralong lifetime, multicolor afterglow, and photo-activated ultralong RTP in multi-dimensional anti-counterfeiting. This article is protected by copyright. All rights reserved.

Effect of Hyper-Cross-Linking on the Electrochromic Device Properties of Cross-Linkable Carbazole–Diphenylamine Derivatives

Triphenylamine derivatives are promising organic electrochromic (EC) materials due to their easy synthesis, low oxidation potentials, high charge-carrier mobilities, electrochemical stability, coloration efficiency, and tunability of EC properties via substitution. Further, the cross-linking strategy provides an added advantage to the small-molecule-based EC devices in terms of better-quality EC films with enhanced EC properties. Herein, we discuss the EC properties of two carbazole–diphenylamine derivatives, C-Sty2 and C-Sty3, with two and three thermally cross-linkable styryl units, respectively, following a donor−π–donor (D−π–D) design, where both the carbazole moiety and cross-linking styrene groups modulate the photophysical and EC properties. Both styryl derivatives formed rigid, uniform, and transparent films with high solvent resistance and exhibited excellent thermal and electrochemical stability upon cross-linking. C-Sty3, with three cross-linkable styryl units, could form more extended cross-links, leading to hyper-cross-linked films with distinct, regular, and porous morphology compared to C-Sty2. Spectroelectrochemical studies of the films showed a color change from a transparent colorless state to an initial light-yellow color and then a final dark-blue color with a color contrast of 65% at 890 nm for C-Sty2 and 78% at 850 nm for C-Sty3. The hyper-cross-linked films of C-Sty3 demonstrated enhanced coloration efficiency (248 cm2/C), optical contrast, and open-circuit memory compared to C-Sty2. Electrochemical impedance spectroscopy analysis showed lower solution and charge-transfer resistances (Rs and Rct, respectively) for hyper-cross-linked films of C-Sty3, indicating higher conductivity and ion diffusion compared to C-Sty2. Thus, a comparison of the EC properties of two polymers with the same electroactive groups reveals the significance of hyper-cross-linking in the EC properties of these cross-linked polymers. Furthermore, the EC properties of the hyper-cross-linked D−π–D derivative, C-Sty3, were compared to those of previously reported molecules, demonstrating the importance of highly branched conducting polymers for EC applications.

Unprecedented facile approach of multiple amino-substituted triphenylamine derivatives for electrochromic devices with extremely high coloration efficiency and unexpected redox stability

Generally, the amino group is considered highly reactive and unstable. Thus, the amino derivatives would be entirely consumed by polymerization or end-capping to preserve the material stability in most research or application fields. Herein, we demonstrated that triphenylamine (TPA) with multiple para-amino substituents could reduce oxidation potential and provide extra oxidation sites while retaining their reversibility. Four para-amino-substituted TPA derivatives (TPA-1N, TPA-2N, TPA-3N, and TPA-ADM) designed and prepared in this study exhibited excellent stability under the electrochemical redox procedure, revealing more than 88% reversibility in the continuous cyclic voltammetry process up to 10,000 cycles. Among all the electrochromic devices, TPA-3N/HV performs the highest coloration efficiency (631 cm2/C), coloration speed (46.4 % s−1), and superior stability, manifesting a reversibility of 99% or 98% after 1000 cycles (switching) or 10 h (maintaining at coloring state), respectively.

Polymorphic triphenylamine derivative showing aggregation-induced emission and high-contrast mechanical force-induced blue shift

Mechanical force-induced, high-contrast blue-shift luminescent mechanochromic (MC) molecules have rarely been reported. Herein, we designed and synthesized an AIE luminogens (AIEgens) triphenylamine derivative N, N-diphenyl-4-(6-phenyl-[2,2′-bipyridin]-4-yl)aniline (DPTPA). Three different emission wavelengths from blue crystals (B-DPTPA), sky-blue crystals (S-DPTPA), and green crystals (G-DPTPA) were obtained by culturing the crystals under different crystallization conditions. All three crystal polymorphs showed high solid luminescent efficiency, each of which was sensitive to external pressure and was accompanied by significant fluorescence blue shift. Under a mechanical force, B-DPTPA shows a 12 nm blue shift, S-DPTPA fluorescence color changed from sky-blue to blue with an increase emission and G-DPTPA changed its color from green (510 nm) to sky-blue (428 nm) with an 82 nm blue shift. Such obvious color change and large blue shift were rarely been reported. Characterization of the photophysical properties, theoretical calculations, hydrostatic pressure, powder X-ray diffraction and X-ray single crystal structures showed that three crystal polymorphs of DPTPA originated from single molecules, space interactions, molecular pairs (dimers), and the blue shift of B-DPTPA, S-DPTPA, G-DPTPA were ascribed to the solid-state morphology transition from crystal to amorphous due to the destruction of space interactions and dimers. This study provides the relationship between the molecular packings and the blue shift emission of AIEgens materials under mechanical forces is understood in the molecular level.

Turn-on stimuli-responsive switch: strategies for activating a new fluorescence channel by pressure.

The stimulus-responsive smart switching of aggregation-induced emission (AIE) features has attracted considerable attention in 4D information encryption, optical sensors and biological imaging. Nevertheless, for some AIE-inactive triphenylamine (TPA) derivatives, activating the fluorescence channel of TPA remains a challenge based on their intrinsic molecular configuration. Here, we took a new design strategy for opening a new fluorescence channel and enhancing AIE efficiency for (E)-1-(((4-(diphenylamino)phenyl)imino)methyl)naphthalen-2-ol. The turn-on methodology employed is based on pressure induction. Combining ultrafast and Raman spectra with high-pressure in situ showed that activating the new fluorescence channel stemmed from restraining intramolecular twist rotation. Twisted intramolecular charge transfer (TICT) and intramolecular vibration were restricted, which induced an increase in AIE efficiency. This approach provides a new strategy for the development of stimulus-responsive smart-switch materials.

Solvent Effects on the Photoinduced [6π]-Electrocyclization Reactions of Mono-, Di-, and Trisubstituted Arylamines: Photophysical, Preparative Photochemistry, and Mechanistic Investigations

The substituent and solvent effects on the spectroscopic behavior and on the photoinduced [6π]-electrocyclization reaction of substituted triphenylamine derivatives have been investigated. Direct irradiation of triphenylamines bearing electron-donor substituents in different solvents has provided for the first time the substituted exo/endo carbazole derivatives from modest to good yields, whereas triphenylamines bearing electron-withdrawing substituents did not provide the carbazoles due to the formation of charge transfer complexes (CTCs). A corollary of the experiments purports that the photoreaction is favored with weak electron-acceptor groups in polar solvents. The lowest-frequency absorption bands of the triarylamines (π,π* electronic transitions) displayed bathochromic shifts as the solvent polarity is increased. The fluorescence emission spectra of triarylamines bearing electron-donor substituents behave as mirror images of the lowest absorption bands, showing dependence on the solvent polarity. Conversely, triarylamines bearing formyl, acetyl, and nitro groups formed CTCs behaving as good fluorescence chromophores in polar solvents. Hammett correlations on the ΔE(0,0) energies of monosubstituted amines showed a bell-shape behavior where the ρ values depended on the solvent polarity. The physical quenching of the photoreaction of triarylamines has demonstrated for the first time that the triplet excited state is univocally the photoreactive state leading to exo/endo carbazole derivatives.

Role of anchoring groups on the light harvesting and optoelectronic properties of triphenylamine derivatives: insights from theory

In the present work, DFT and time-dependent DFT calculations were performed to investigate the role of anchoring groups on the photophysical properties and reveal structure-property correlations of triphenylamine (TPA) derivatives. The selected anchoring groups are tetrazole, acrylamide, hydantoin, and rhodanine. Our results show that the different anchoring groups employed alter the planarity, intramolecular charge transfer properties, and HOMO-LUMO gap and hence influence the optoelectronic properties of the dyes. Although all molecules fulfill the basic requirements with suitable energy levels, band gap, absorption, and charge transfer properties, the dye with rhodanine acceptor (TPA4) was the most promising candidate due to its lowest HOMO-LUMO gap, red-shifted highestλmaxabsorption value, better ICT pattern, low total reorganization energy, and good electron injection properties. Overall, it is anticipated that the results of this investigation will point to new avenues for the experimental fabrication of remarkably effective metal-free organic dyes for solar cell applications.

An Ultrastable Tetrabenzonaphthalene-Linked conjugated microporous polymer functioning as a high-performance electrode for supercapacitors

BackgroundConjugated microporous polymers (CMPs) have been applied widely in several energy storage applications. Triphenylamine derivatives are good electrode materials that can be processed into SC devices because of their high charge mobilities, unique electronic properties, and high redox activity. MethodsWe prepared two novel tetrabenzonaphthalene-linked conjugated microporous polymers (TBN-pH CMPs) through [4 + 2] and [4 + 3] Schiff-base condensations of 2,7,10,15-tetra(4-formylphenyl)tetrabenzonaphthalene (TBN-PhCHO) with tetrakis(4-aminophenyl)ethene (TPE-4NH2) and tris(4-aminophenyl)amine (TPA-3NH2), respectively. Fourier transform infrared, and solid-state 13C NMR spectroscopy investigated the structures of the as-prepared CMPs. Significant FindingsThese CMPs, had large surface areas and outstanding thermal stability at temperatures of up to 400 °C, making them suitable for use as electrodes in supercapacitor (SC) systems. Indeed, the TBN-TPA CMP–based electrode had high specific capacitances (251 F g− 1 measured at 0.5 A g–1) and capacity retentions (94%, measured after 5000 cycles at 10 A g–1) when tested in three-electrode systems. We attribute the remarkable electrochemical activity and conductivity of the TBN-TPA CMP electrode to its large specific surface area (230 m2 g–1) and chemical structure featuring stacking of the benzene rings of its redox-active triphenylamine moieties.

Multi-stimuli responsive behavior of two Schiff base complexes with high contrast multicolor switching and wearable applications for rapid detection of HCl and NH3 vapor

In this work, we successfully synthesized two Schiff base (HL) complexes, ZnLCl2 (1) and [Cd2L2Cl4]·CH3CN (2), via the one-pot reaction of metal salts with 4-[bis(4-bromophenyl)amino]benzaldehyde and 3-hydroxy-2-naphthoic acid hydrazide. Complex 2 exhibits not only acidochromic properties but also NH3-induced discoloration behavior, which is rarely reported among triphenylamine derivatives or complexes. However, complex 1 shows no color change upon fuming with HCl or NH3 vapor. The experimental results show that acidochromism may be due to the decomposition of the structure by HCl vapor, while NH3-induced discoloration is mainly attributed to the phase change of 2 from crystalline to amorphous state. In addition, complexes 1 and 2 showed high-contrast mechanochromic luminescence (MCL) change from yellow to orange and green to yellow, respectively. Complexes 1 and 2 also exhibit electrochromic behavior with color change from yellow to brown. Moreover, complex 2 was successfully made into test paper for mechanical stimuli and the rapid detection of HCl and NH3 vapor. The complex 2 can be fixed on a mask coat to fabricate a 2-based wearable hazardous gas sensor, suggesting that 2 is expected to develop into the next generation wearable sensors for detection of HCl and NH3 vapor.

Nanospheres of Near-Infrared Aggregation-Induced Emission Probes to Target Mitochondria to Ablate Tumors with Reactive Oxygen Species Generation under Hypoxia

Severe aggregation-caused quenching and the lack of special organelle targeting in conventional photosensitizers (PSs) have limited their advantages in terms of their accurate spatial–temporal control and noninvasive features. Furthermore, severe tumor hypoxia equally diminished the effectiveness of treatment. Herein, a series of aggregation-induced emission (AIE) PSs with precise targeting of organelles are synthesized by simply regulating the molecular structure. The rotation of the donor in the molecule was optimized by altering the tail chain of the triphenylamine derivative, which inhibited nonradiative internal conversion and promoted intersystem crossing to facilitate the free radical generation, and the production efficiency of the type I reactive oxygen species exceeds that of the commercial indicator rose bengal (3-fold). The optimal AIE PS named BETTP can specifically target mitochondria and recognize cancer cells. Simultaneously, live/dead cell costaining assays and flow cytometry validated that BETTP nanoparticles (NPs) have the ability to efficaciously ablate cancer cells in hypoxic conditions after encapsulating BETTP into carriers as nanoparticles. In addition, BETTP NPs also manifest superior performance during near-infrared imaging-guided type I photodynamic therapy in solid tumors. Such BETTP NPs demonstrate the critical feasibility of achieving precise delivery of drugs and targeting of organelles for precise therapy in hypoxic environments, providing a reliable reference for tumor hypoxia challenges.

Side-chain engineering on triphenylamine derivative-based hole-transport materials for perovskite solar cells: Theoretical simulation and experimental exploration

The development of hole-transport materials (HTMs) is a significant approach to promote the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Here, based on the triphenylamine (TPA) derivatives and patulous TPA derivatives as side-chains, WR1 and WR2 are designed and explored by density functional theory (DFT), time-dependent DFT (TD-DFT) in combination with Marcus electron transfer theory. The calculated results show that the WR1 exhibits matching energy levels with perovskite and better hole transporting ability in comparison with these of WR2 can save as a potential HTM for PSCs applications. In order to confirm screening results of molecular design, the WR1 as HTM in PSC device reveals that the WR1-based PSC device obtained the PCE of 20.04% higher than that of the typical Spiro-OMeTAD-based device (18.84%). Moreover, the experimental results can well verify the data of theoretical simulations. The strategy of side-chain modification on TPA derivatives-based materials is a viable method to exploit new HTMs.

Construction of supramolecular dimer photosensitizers based on triphenylamine derivatives and cucurbit[8]uril for photocatalysis

We have designed and constructed supramolecular dimers between triphenylamine derivatives with AIE properties and CB[8] through host–guest interactions, which can be used as photosensitizers for photooxidation reactions of thioanisole.