Blue Fluorophore Research Articles

Construction of a dual “off-on” near-infrared fluorescent probe for bioimaging of HClO in rheumatoid arthritis

Hypochlorous acid (HClO) serves as a critical biomarker in inflammatory diseases such as rheumatoid arthritis (RA), and its real-time imaging is essential for understanding its biological functions. In this study, we designed and synthesized a novel probe, RHMB, which ingeniously integrates rhodamine B and methylene blue fluorophores with HClO-specific responsive moieties into a single molecular framework. Upon exposure to HClO, RHMB exhibited significant dual-channel fluorescence enhancement characterized by high sensitivity (LODs of 2.55 nM and 14.08 nM), excellent selectivity, and rapid response time (within 5 s). Notably, RHMB enabled reliable imaging of both exogenous and endogenous HClO in living cells and in zebrafish, employing a unique duplex-imaging turn-on approach that highlighted its adaptability across various biological contexts. Furthermore, RHMB effectively monitored HClO fluctuations in an RA mouse model and assessed the therapeutic efficacy of diclofenac (Dic) in alleviating RA symptoms. These findings underscore the potential of RHMB as an invaluable tool for elucidating the biological roles of HClO in various diseases.

Tuning β-Si3Al3O3N5 phosphors by Eu or Ce doping for white light-emitting diodes (wLEDs)

SiAlON-based phosphors have garnered considerable attention in the field of white lighting owing to their excellent thermal stability, and rare earth doped SiAlON-based phosphors are expected to be used in a new generation of lighting sources. In this work, Eu2+ or Ce3+ doped Si3Al3O3N5 phosphors were synthesized by high temperature solid phase method. The microstructure of the phosphors exhibited irregular grain. The two phosphors exhibit green and cyan luminescence under 365 nm excitation, which are derived from the 5d-4f transitions of Eu2+ and Ce3+, respectively. The quenching concentrations are 3 % and 4 % for Eu2+ and Ce3+doped phosphors, respectively. The fluorescence intensity of Eu2+ and Ce3+ activated SiAlON powders decreased to 50 % of the room temperature intensity at 179 °C and 170 °C, respectively. The thermal activation energy values of the two phosphors were 0.35 eV, and the coordinate configuration diagram was constructed to comprehensively analyze the thermal quenching behavior of phosphors. Finally, the two phosphors powders were mixed with red and blue fluorophore to obtain white LEDs, showing low color temperature, high color rendering, high power unsaturation and long half-life. The SiAlON-based phosphors with excellent thermal stability obtained in this work achieve different wavelengths of luminescence in the green region. The results show that the β-Si3Al3O3N5 phosphor can be used as a candidate material for high-quality green light supplement for wLEDs.

New Phenanthro[9,10-d]oxazole-Based Fluorophores with Hybridized Local and Charge-Transfer Characteristics for Highly Efficient Blue Non-Doped OLEDs with Negligible Efficiency Roll-Off.

It is vital to develop highly efficient non-doped blue organic light-emitting diodes (OLEDs) with high color purity and low-efficiency roll-off for applications in display and lighting. Herein, two blue D-A fluorophores TPA-PO and TPA-DPO are designed and synthesized, in which phenanthro[9,10-d]oxazole (PO) acts as the acceptor and triphenylamine as the donor. TPA-PO and TPA-DPO display good thermal stability and efficient luminescence efficiency in neat film. Results based on photophysical property and theoretical calculation demonstrate that TPA-PO and TPA-DPO possess the hybridized local and charge-transfer (HLCT) feature, which can utilize the triplet exciton to achieve highly efficient electroluminance (EL). The non-doped OLEDs with TPA-PO/TPA-DPO as pure emissive layer show the uniform EL emission peak at 468 nm, corresponding to CIE coordinates of (0.168, 0.187) and (0.167, 0.167), respectively. The TPA-DPO-based non-doped OLEDs provide the maximum external quantum efficiency (EQE) of 7.99 % and high exciton utility efficiency of 48.4 %~72.6 %. Moreover, the TPA-DPO-based device exhibits low-efficiency roll-off, still maintaining the EQE of 6.03 % at the high luminance of 5000 cd m-2. Those findings state clearly that PO is a promising building block of blue fluorophore with a potential HLCT feature to be applied in non-doped OLEDs.

A Breakthrough in Color‐Tunable All‐Fluorescent White OLEDs through the Cooperation Between a New Blue HLCT Fluorophore and a Long‐Wavelength TADF Emitter

AbstractIt is a vitally important and challenging task to achieve high efficiency and wide color‐tunable white organic light emitting diodes (CT‐WOLEDs) meeting the needs of various decoration and lighting applications. Here, a high‐performance single‐cell all‐fluorescent CT‐WOLED with a single‐doped single‐emissive‐layer structure has been developed employing a multi‐functional hybrid local and charge transfer (HLCT) fluorophore 2‐(4‐(9H‐carbazol‐9‐yl)−2′,5′‐difluoro‐[1,1′:4′,1′'‐terphenyl]−4‐yl)−1‐phenyl‐1H‐phenanthro[9,10‐d]imidazole (PICZ2F) as a deep‐blue emitter as well as an effective host for a yellow thermally activated delayed fluorescence emitter. The record‐breaking power efficiency of 89.50 lm W‒1 and correlated color temperature (CCT) span from 3749 to 18 279 K are achieved simultaneously, which is not only one of the state‐of‐the‐art CT‐WOLEDs reported so far, but also comparable to the best values from all‐fluorescent white devices with a single‐emissive‐layer. Moreover, by using PICZ2F as an emitter, an external quantum efficiency (EQE) of 7.10% with the Commission Internationale de lEclairage (CIE) coordinates of (0.155, 0.068) is achieved in the doped device, and a low‐efficiency roll‐off even at a high luminance of 15 000 cd m−2 (EQE15000: 5.80%) is achieved in the non‐doped device. Overall, the findings provide a promising strategy to develop simple but efficient CT‐WOLEDs.

Deep blue emitting dual state fluorescent triphenylamine-dicyclohexylurea derivative: Multi-stimuli responsive fluorescence switching and methanol/water sensing

A new deep blue emissive organic fluorophore (N-cyclohexyl-N-(cyclohexylcarbamoyl)-4-(diphenylamino)benzamide (NCDPB)) was designed and synthesized, which showed strong fluorescence both in solution and solid-state. Solid-state structural analysis of NCDPB revealed non-planar twisted molecular conformation with extended hydrogen bonding between the amide functionalities. The propeller shaped triphenylamine (TPA) and non-planar cyclohexyl unit prevented close π…π stacking and produced strong deep blue emission in the solid state (λmax = 400 nm, quantum yield (Φf) = 12.6 %). NCDPB also exhibited strong solvent polarity dependent tunable emission in solution (λmax = 402–462 nm, Φf = 1.15 (compared to quinine sulphate)). NCDPB showed reversible fluorescence switching between two fluorescence states upon mechanical crushing and heating/solvent exposure. Mechanical crushing caused red shifting of fluorescence from 400 to 447 nm and heating/solvent exposure reversed the fluorescence. Further, NCDPB also displayed off–on reversible/self-reversible fluorescence switching upon exposure to trifluoracetic acid (TFA) and NH3. The repeated fluorescence switching cycles indicated high reversibility without any significant change of fluorescence intensity. The drastically different fluorescence of NCDPB in CH3OH and EtOH was utilized to distinguish them and monitor CH3OH contamination in ethanol and benzene. It showed limit of detection (LOD) of methanol up to 0.25 % and 7 % in benzene and ethanol, respectively. The water sensitive fluorescence modulation of NCDPB in organic solvents was used to sensing water contamination in common organic solvents. Thus, integration of twisted TPA with H-bonding urea produced dual state emitting organic fluorophore with multi-responsive fluorescence switching and solvent sensing.

Reversible Photochromism for Dynamically Tuning Full‐Color Circularly Polarized Luminescence Toward Multi‐Level Anti‐Counterfeiting Application

AbstractPhotochromic circularly polarized luminescence (CPL) demonstrates broad application prospects in the field of advanced functional materials. However, the current photochromic CPL focuses predominantly on single‐band CPL adjustment, and how to achieve dynamically tunable CPL in multi‐band is still highly challenging. This work reports the success in utilizing reversible photochromism for realizing full‐color CPL emission. Photochromic flexible films are created consisting of triple components: spiropyran (SP) working as photochromic matter, polyurethane (PU) as matrix, and chiral helical polyacetylene as chiral component. Further introducing blue fluorophore 9‐anthracene carboxylic acid (ACA) in the film, blue CPL and red CPL are emitted respectively through selective absorption/transmission and circularly polarized fluorescence energy transfer (CPF‐ET). Doping the photochromic film with diverse fluorophores provides full‐color CPL emission. Adding Zn2+ further intensifies fluorescence and CPL via forming merocyanine (MC)‐Zn2+ complex. Taking advantage of the diverse fluorescence and CPL emission, anti‐counterfeiting, and secondary encryption application of the resulting photochromic CPL materials are demonstrated.

Anthracene and Pyrene Derivatives as Blue Fluorophores: Synthesis, Characterization and Photophysical Properties

Ant hracene and pyrene derivatives have been widely studied as emitting materials in optoelectronic devices due to their excellent fluorescence properties. In the present study, two novel blue fluorophores from anthracene and pyrene (PAP and PTATP) were successfully synthesized using a Suzuki-cross coupling reaction and their photophysical properties were elucidated. PTATP with an extended p-conjugation system had a fluorescence emission maximum in green-blue region at 475 nm, whereas PAP, with a shorter conjugation length, emitted pure-blue emission peak at 442 nm. The study of absorption and emission spectra in various solvents found that both compounds produced solvent-independent spectra due to their non-polar molecules. In addition, the aggregation-caused quenching phenomenon was observed, when the emission spectra were recorded in high water fraction solvent.

Design of 2-Pyridone Fluorophores for Brighter Emissions at Longer Wavelengths.

The recent discovery of blue fluorophores with high quantum yields based on pyridone structures inspired the development of new low-molecular-weight fluorophores with bright emissions at tunable wavelengths, which are highly attractive for various applications. In this study, we propose a rational design strategy for 2-pyridone-based fluorophores with bright emissions at long wavelengths. With a detailed understanding of the positional substitution effects on each carbon atom of the 2-pyridone core, we developed a bright blue fluorophore (λabs =377 nm; λem =433 nm; ϵ=13,200 M-1 cm-1 ; ϕF =88 %) through C3 -aryl and C4 -ester substitutions followed by cyclization. Furthermore, by applying the intramolecular charge transfer (ICT) principle, we invented a bright green fluorophore through C3 - and C4 -diester and C6 -aryl substitutions. The ICT fluorophore based on the pyridone structure shows large molar absorptivity (ϵ=20,100 M-1 cm-1 ), longer emission wavelength (λem =539 nm), high emission quantum yield (ϕF =74 %), and large Stokes shift (Δv=5720 cm-1 ), which are comparable to those of practical fluorescent probes.

Simultaneous Two- and Three-Photon Deep Imaging of Autofluorescence in Bacterial Communities.

The intrinsic fluorescence of bacterial samples has a proven potential for label-free bacterial characterization, monitoring bacterial metabolic functions, and as a mechanism for tracking the transport of relevant components through vesicles. The reduced scattering and axial confinement of the excitation offered by multiphoton imaging can be used to overcome some of the limitations of single-photon excitation (e.g., scattering and out-of-plane photobleaching) to the imaging of bacterial communities. In this work, we demonstrate in vivo multi-photon microscopy imaging of Streptomyces bacterial communities, based on the excitation of blue endogenous fluorophores, using an ultrafast Yb-fiber laser amplifier. Its parameters, such as the pulse energy, duration, wavelength, and repetition rate, enable in vivo multicolor imaging with a single source through the simultaneous two- and three-photon excitation of different fluorophores. Three-photon excitation at 1040 nm allows fluorophores with blue and green emission spectra to be addressed (and their corresponding ultraviolet and blue single-photon excitation wavelengths, respectively), and two-photon excitation at the same wavelength allows fluorophores with yellow, orange, or red emission spectra to be addressed (and their corresponding green, yellow, and orange single-photon excitation wavelengths). We demonstrate that three-photon excitation allows imaging over a depth range of more than 6 effective attenuation lengths to take place, corresponding to an 800 micrometer depth of imaging, in samples with a high density of fluorescent structures.

Naptha-phenanthroimidazole-based blue fluorophores (y

Organic light-emitting diodes are a promising new technology for next-generation displays and lighting applications, particularly in the quest for efficient deep blue fluorophores (y= < 0.05). Despite the receipt of several reports, it remains imperative to advance the development of a deep blue emitter that can address solubility, stability, color purity, and efficiency. Eye on these challenges, herein, four new blue phenanthroimidazole and naphthalene-based derivatives, 2-(naphthalen-1-yl)-1H-phenanthro[9,10-d]imidazole(Pq-NH-NA), 2-(naphthalen-1-yl)-1-phenyl-1H phenanthro [9,10-d]imidazole (Pq-An-NA), 2-(naphthalen-1-yl)-1-(3-(trifluoromethyl)phenyl)-1H-phenanthro[9,10-d]imidazole (Pq-mF-NA), and 2-(naphthalen-1-yl)-1-(4-(trifluoromethyl)phenyl)-1H-phenanthro[9,10-d]imidazole (Pq-pF-NA) were designed and synthesized. Further, the PI molecules were structurally characterized by spectroscopic analysis, and their thermal decomposition (Td) is found to be 203–309 °C. Substitution at the N1 position of imidazole provides a facile alternative role for photophysical and electronic properties. The PI fluorophores were further characterized in solution, thin-film, and solid where the solid results are enhanced in terms of intense color emission (x = 0.158, y = 0.037). It showed a good quantum yield of 14.28 % in solution and 19.33 % in solid, indicating that fluorinated molecules lead to better performance than the rest of them. Additionally, the InGaN LED fabricated with the fluorinated molecule Pq-pF-NA emitted 425 nm with a deep blue emission and yielding CIE color coordinates (x = 0.154, y = 0.048). The film study also revealed the deep blue emission with increasing concentration of emitter (2.5 %). The observed results apprise that the synthesized fluorophores are efficient to deep blue emitters and capable candidates for organic light-emitting diodes.

Visualizing Dipeptidyl Peptidase-IV with an Advanced Non-π-Conjugated Fluorescent Probe for Early Thyroid Disease Diagnosis.

Early detection and effective treatment of thyroid cancer are vital due to the aggressiveness and high mortality rate of the cancer. Nevertheless, the exploration of dipeptidyl peptidase-IV (DPP-IV) as a biomarker for thyroid diseases has not been widely conducted. In this study, we developed a novel non-π-conjugated near-infrared fluorescent probe, MB-DPP4, specifically designed to visualize and detect endogenous DPP-IV. Traditional DPP-IV-specific fluorescent probes rely primarily on the intramolecular charge transfer mechanism. For this reason, these probes are often hampered by high background levels that can inhibit their ability to achieve a fluorescence turn-on effect. MB-DPP4 successfully surmounts several drawbacks of traditional DPP-IV probes, boasting unique features such as exceptional selectivity, ultrahigh sensitivity (0.29 ng/mL), innovative structure, low background, and long-wavelength fluorescence. MB-DPP4 is an "off-on" chemosensor that exhibits strong fluorescence at 715 nm and releases a methylene blue (MB) fluorophore upon interacting with DPP-IV, resulting in a visible color change from colorless to blue. Given these remarkable attributes, MB-DPP4 shows great promise as a versatile tool for advancing research on biological processes and for evaluating the physiological roles of DPP-IV in living systems. Finally, we conducted a comprehensive investigation of DPP-IV expression in human serum, urine, thyroid cells, and mouse thyroid tumor models. Our findings could potentially establish a foundation for the early diagnosis and treatment of thyroid diseases.

Role of Acids in Producing Ultrabright, Dual‐Emissive Carbon Dots and their Urea/Biuret Composites with Ultralong Afterglow

AbstractSince 2015, m‐phenylenediamines (mPD) have become a popular carbon source for the synthesis of carbonized polymer dots (CPDs). However, their exact fluorescence mechanism is still obscure. To elucidate this, inorganic acids that are carbon‐free are chosen as additives for a comparative study. It is found that the green fluorescence quantum yield (nearly 80%), photostability, and reaction yield (over 90%) can be enhanced by introduction of most of inorganic acids with moderate amount. Besides, green‐blue dual emission is observed in acid‐assisted groups. UV‐vis absorption, Fourier‐transform infrared spectroscopy, and surface‐enhanced Raman scattering results indicate that the green fluorescence center is composed of quinoid rings, whereas the blue fluorophore contains benzenoid rings. Moreover, room‐temperature afterglow with lifetime up to 1.25 s is observed exclusively in acid‐assisted CPDs composites with urea/biuret. The blue chromophore is proposed to be the origin of the triplet level that induces the long afterglow. This work provides an in‐depth understanding on the macromolecular structures of CPDs derived from phenylenediamines, and contributes a new line of thought to the origin of phosphorescence in N‐doped carbon dots.

Hybrid Lead‐Free Metal Antimony Oxide Chlorides with Highly Efficient Blue Light Emissions

AbstractHerein, we report two hybrid zero‐dimensional (0D) lead‐free metal oxide halides of [PPip]Sb2Cl6O (1) ([PPip]=1‐(2‐Pyridyl)piperazine) and [PmPip]Sb2Cl6O (2) ([PmPip]=1‐(2‐Pyrimidyl)piperazine). Compounds 1 and 2 are able to exhibit narrow blue light emissions excited by UV light with photo‐luminescence quantum yields (PLQYs) of 25.49 % and 24.71 %, respectively. Through systematical characterizations, these blue light emissions can be attributed to the radiative transition in conjugated organic cations. Benefiting from the highly efficient intrinsic blue emissions, compound 2 can be used as blue fluorophor to fabricate liquid crystal display. This work provides a new to assembly blue emitter through by virtue of the optical active organic cations in hybrid materials.

White light emission from coumarin and rhodamine derivatives based on RGB multicomponent system

The mixture of red, green, and blue (RGB) organic fluorophores in a single blend is becoming more relevant to produce metal-free, low cost and color tunable white light emission. Herein we describe the combination of pure organic molecules based on the coumarin and rhodamine frameworks that generated broad or multi-band emission in both solution and solid forms. The derivatives of coumarin (CB), furocoumarin (CG) and rhodamine (CR1 and CR2) were synthesized and characterized using 1H NMR, 13C NMR, FTIR and ESI-MS spectroscopic techniques. The “closed-form” of the synthesized rhodamines have been further elucidated with the single crystal X-ray analysis. Their photophysical, thermal stability and electrochemical properties have been investigated, accompanied by DFT calculations to assess the plausible mechanism responsible for white light along with their eminent characteristics. Single mixture of ethanol-solubilized CR2:CG:CB in the ratio of 3:10:3 showed extremely pure white light fluorescence with CIE coordinates of (0.32, 0.33) when excited at 360 nm while CR1:CG:CB revealed almost pure white light (0.27, 0.32) in the ratio of 1:2:1 when excited at a much longer wavelength (λex = 395 nm). The results obtained are very encouraging in such a way that only minimal proportions of the blue and green fluorophores are required in the single mixture for a highly efficient FRET system when combined with the newly synthesized rhodamine derivatives. The ratio differences can be down to 30–42 % as compared to white light mixture with the commercial red R640. Furthermore, all of the synthesized RGB components exhibit reasonably good thermal stability with onset of decomposition above 210 °C, endowing their suitability for general applications of optoelectronic devices. The HOMO-LUMO energy band gaps from the cyclic voltammetry and geometrical optimized structures of the ground state are generally in nice agreement. White light emission was also generated when the polymer mixtures containing each RGB emitters was coated on a commercial UV-LED, demonstrating potential low cost and purely organic device set-up.

Fluoranthene-based derivatives for multimodal anti-counterfeiting and detection of nitroaromatics

Two novel fluoranthene ensembles with ethyl alcohol (FOH) and ethanethiol (FSH) functionality with distinct diagonal and ladder arrangements in the crystal lattices were developed for Latent Fingerprints (LFPs) towards analysis of explosives.

A NIR fluorescent probe for the detection of renal damage based on overrepresentation of alanine aminopeptidase enzyme.

Kidney damage generates changes at the phenotypic and genotypic levels that allow its monitoring using different biomarkers in blood, urine or serum. Among these biomarkers, kidney failure causes the urine overrepresentation of the alanine aminopeptidase (APN) enzyme. Here, we describe the design of a molecular probe (NB-ALA) based on the Nile Blue fluorophore (NB), which can detect the APN enzyme in urine by simple fluorometric measurements.

β-Galactosidase-Activatable Nile Blue-Based NIR Senoprobe for the Real-Time Detection of Cellular Senescence.

Cellular senescence is a stable cell cycle arrest in response to stress or other damage stimuli to maintain tissue homeostasis. However, the accumulation of senescent cells can lead to the progression of various senescence-related disorders. In this paper, we describe the development of a β-galactosidase-activatable near-infrared (NIR) senoprobe, NBGal, for the detection of senescent cells based on the use of the FDA-approved Nile blue (NB) fluorophore. NBGal was validated in chemotherapeutic-induced senescence cancer models in vitro using SK-Mel 103 and 4T1 cell lines. In vivo monitoring of cellular senescence was evaluated in orthotopic triple-negative breast cancer-bearing mice treated with palbociclib to induce senescence. In all cases, NBGal exhibited a selective tracking of senescent cells mainly ascribed to the overexpressed β-galactosidase enzyme responsible for hydrolyzing the NBGal probe generating the highly emissive NB fluorophore. In this way, NBGal has proven to be a qualitative, rapid, and minimally invasive probe that allows the direct detection of senescent cells in vivo.

A facile method to achieve red thermally activated delayed fluorescence emitters with EQE over 30% via molecular aspect ratio engineering

Bandgap narrowing via the incorporation of strong donor and/or acceptor units into the molecular structure is a well-known strategy for the design of the long-wavelength fluorophores. Due to the energy-gap law, achieving high emission quantum yield at long wavelength becomes a paradox. Therefore, the red fluorescence emitters with external quantum efficiency (EQE) over 30 % have rarely been reported in comparison with blue and green fluorophores. In this work, a series of the thermally activated delayed fluorescence (TADF) materials (PH-TPA, BZ-TPA and PO-TPA) featured with rigid skeleton demonstrated low non-radiative decay rates and high photoluminescent quantum efficiency. Importantly, the engineering of molecular aspect ratio of the TADF emitters led to high horizontal emitting dipole ratio, thus enhancing the device performance. As a result, organic light-emitting diodes based on PH-TPA, BZ-TPA and PO-TPA showed record-high EQEs of 33.0 % at 624 nm, 31.3 % at 634 nm and 34.9 % at 632 nm, respectively. This work provided a facile and yet effective method for the construction of efficient red TADFs via the integration of rigid emission core and the control of molecular aspect ratio.

Highly efficient deep-blue electrofluorescence with optimized excited state composition and "hot-exciton" channel

The properties of excited states of emitters play an important role in OLEDs. How to obtain balanced hybrid localized charge transfer (HLCT) state by reasonably designing molecules is still a challenge. Herein, three HLCT states D-π-A type blue fluorophores with different LE/CT hybrid degree were designed and synthesized, namely 3,6-di-tert-butyl-9-(4-(6-(4-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl)pyren-1-yl)phenyl)-9H carbazole (DTPCZPYTZ), 3,6-di-tert-butyl-9-(4-(4-(4-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl)naphthalen-1-yl)phenyl)-9H-carbazole (DTPCZNATZ) and 3,6-di-tert-butyl-9-(4''-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-[1,1':4′,1″-terphenyl]-4-yl)-9H-carbazole (DTPCZPHTZ). DTPCZPHTZ achieved quasi-equivalent hybrid local and charge-transfer (HLCT) excited state and efficient “hot-exciton” channel, the non-doped deep-blue device based on DTPCZPHTZ has an electroluminescence emission peak (λEL) of 427 nm with Commission International de L'Eclairage (CIE) of (0.157, 0.037), the maximum external quantum efficiency (EQE) is up to 5.7% and the efficiency roll-off is only 5% (under 1000 cd m−2), which is outstanding in the reported deep-blue emitters. This study proved that the quasi-equivalent hybrid HLCT state is beneficial to improving device performance.

D–π–A–π–D-type Fluorophores based on Pyridal[2,1,3]thiadiazole acceptor with hybridized local and charge-transfer excited-state for high-efficiency OLEDs

Hybridized local and charge-transfer (HLCT) excited-state fluorophores, which are characterized by high photoluminescence quantum yield (PLQY) and reverse intersystem crossing (RISC) from high-lying triplets to singlets, has emerged advantages in organic light-emitting diodes (OLEDs) application. Although blue and green HLCT fluorophores are well developed, the long wavelength ones (orange to red) are still behind. Here, based on more electron-deficient Pyridal[2,1,3]thiadiazole (PT) acceptor, a D–π–A–π–D-type HLCT emitter, namely 2CZP-PT, with orangered emission is designed and synthesized. Due to the less steric hindrance of pyridine nitrogen in PT, a small twist angle between the π bridge and acceptor on the nitrogen side is obtained, which endows the whole molecule with relative planar conformation. Thus 2CZP-PT exhibits HLCT characteristics with high PLQY (77% in THF solution and 44% in neat film), as well as energy levels arrangement favoring the RISC process from high-lying triplet levels to singlet levels. The doped devices based on 2CZP-PT reached a maximum external quantum efficiency (EQEs) of 9.57% with an electroluminescence (EL) peak at 568 nm. While the non-doped OLEDs based on 2CZP-PT emitter achieved a maximum EQEs of 1.34% with red EL peaked around 600 nm, whose efficiency roll-off is only 1.5% at 1000 cd m−2. These device performances demonstrate PT based D–π–A–π–D-type fluorophores are promising for their long-wavelength OLEDs application.