Treatment of benign rectal stricture caused by repeated anal insertion by endoscopy and balloon dilation: A case report.

BACKGROUND: Benign rectal strictures can be categorized as primary (disease-related) and secondary (surgical anastomosis-related). Secondary strictures arise from surgical complications, whereas primary strictures have diverse etiologies, including various inflammatory conditions. Benign strictures are usually managed by surgery and endoscopy. We present an unusual etiology of benign rectal stricture caused by the repeated insertion of foreign objects into the rectum for sexual purposes, resulting in rectal injury and subsequent chronic inflammation. CASE SUMMARY: A 53-year-old man presented to the outpatient clinic of the Colorectal Surgery Department with symptoms of chronic constipation and bloody stools. The patient previously experienced rectal injury due to foreign object insertion for sexual purposes. Colonoscopy revealed benign circumferential narrowing of the rectum. He underwent treatment by endoscopic argon plasma coagulation and balloon dilation and follow-up as an outpatient for 4 months. A colonoscopy at the end of the follow-up period revealed no evidence of rectal stricture relapse. CONCLUSION: A history of rectal injury, followed by chronic inflammation, should be considered in patients with benign rectal strictures. Management with endoscopic argon plasma coagulation and balloon dilation can prevent the need for surgical resection of benign rectal strictures.

Repair of a giant inguinoscrotal hernia with herniation of the ileum and sigmoid colon: A case report.

BACKGROUND: Giant inguinoscrotal hernias are huge inguinal hernias that extend below the midpoint of the inner thigh in the standing posture. Giant inguinoscrotal hernias are rare in developed countries because of their better medical resources and early treatment. However, they can develop in patients who refuse surgery or ignore their condition. Intervention is inevitable because strangulation and organ perforation can occur, leading to peritonitis and sepsis. Common surgical approaches include open abdominal and inguinal approaches or a combination of both. CASE SUMMARY: We present the case of a 73-year-old man who visited our emergency department with a huge mass in his left scrotum and septic complications. Abdominal computed tomography revealed a large left inguinoscrotal hernia that contained small bowel loops and the colon. Emergency surgical intervention was performed immediately because intestinal strangulation was highly suspected. The operative repair was performed using a combination of mini-exploratory laparotomy and the inguinal approach. The incarcerated organs, which included the ileum and sigmoid colon, had relatively good intestinal perfusion without perforation or ischemic changes. They were successfully reduced into the abdomen, and bowel resection was not necessary. A tension-free prosthetic mesh was used for the hernia repair. Two weeks after the initial surgery, and with adequate antimicrobial therapy, the patient recovered and was discharged from our hospital. No evidence of hernia relapse was noted during the outpatient follow-up examination 3 mo after surgery. CONCLUSION: Emergency surgery involving combined mini-exploratory laparotomy and the inguinal approach should be performed for serious incarcerated giant inguinoscrotal hernias.

Creating Augmented Reality Holograms for Polytrauma Patients Using 3D Slicer and Holomedicine Medical Image Platform.

In traumatology physicians heavily rely on computed tomography (CT) 2D axial scans to identify and assess the patient's injuries after an accident. However, in some cases it can be difficult to rigorously evaluate the real extent of the damage considering only the bidimensional slices produced by the CT, and some life-threatening lesions can be missed. With the development of 3D holographic rendering and extended reality (XR) technology, CT images can be projected in a 3D format through head-mounted holographic displays, allowing multi-view from different angles and interactive slice intersections, thus increasing anatomical intelligibility. In this article, we explain how to import CT scans into holographic displays for 3D visualization and further compare the methodolgy with traditional bidimensional reading.

Probing Electron Excitation Characters of Carboline-Based Bis-Tridentate Ir(III) Complexes.

In this work, we report a series of bis-tridentate Ir(III) metal complexes, comprising a dianionic pyrazole-pyridine-phenyl tridentate chelate and a monoanionic chelate bearing a peripheral carbene and carboline coordination fragment that is linked to the central phenyl group. All these Ir(III) complexes were synthesized with an efficient one-pot and two-step method, and their emission hue was fine-tuned by variation of the substituent at the central coordination entity (i.e., pyridinyl and phenyl group) of each of the tridentate chelates. Their photophysical and electrochemical properties, thermal stabilities and electroluminescence performances are examined and discussed comprehensively. The doped devices based on [Ir(cbF)(phyz1)] (Cb1) and [Ir(cbB)(phyz1)] (Cb4) give a maximum external quantum efficiency (current efficiency) of 16.6% (55.2 cd/A) and 13.9% (43.8 cd/A), respectively. The relatively high electroluminescence efficiencies indicate that bis-tridentate Ir(III) complexes are promising candidates for OLED applications.

Counterion Migration Driven by Light-Induced Intramolecular Charge Transfer.

A series of D-π-A + pyridinium compounds, in which D = -NPh2 and A+ = -PyMe+ are linked by various amounts of linear phenyl spacers, were strategically designed and synthesized. Their characterization revealed the presence of excited-state intramolecular charge transfer (ESICT) that triggers a corresponding response from the counterion. In medium and strong polar solvents, the fast solvent relaxation occurring after ESICT overwhelms the counterion effect, showing typical emission solvatochromism. In weakly polar solvents, ESICT induces counteranion migration for electrostatic stabilization, the time scale of which is dependent on the radius of the counteranion, the length of the π-linker, and the viscosity of the solvent. In low-viscosity organic solvents such as toluene, counteranion migration occurs within several tens to hundreds of picoseconds, resulting in a time-dependent continuous emission that can be resolved from the spectral temporal evolution. Concrete evidence for this is provided by the chemical synthesis of a D-π-A + pyridinium-sulfur trioxide- zwitterion, where anion migration is restricted due to its internally locked ion pair. As a result, only a single emission band can be observed. These comprehensive studies prove that the ion migration process may be significant for a wide range of ESICT-type ionic fluorophores. Such an ionic movement, triggered by optically pumped ESICT of the D-π-A + dyad, is similar to the molecular machine driven by the redox reaction, but with a facile access and fast response.

Highly Emissive Dinuclear Platinum(III) Complexes.

Dinuclear Pt(III) complexes were commonly reported to have short-lived lowest-lying triplet states, resulting in extremely weak or no photoluminescence. To overcome this obstacle, a new series of dinuclear Pt(III) complexes, named Pt2a-Pt2c, were strategically designed and synthesized using donor (D)-acceptor (A)-type oxadiazole-thiol chelates as bridging ligands. These dinuclear Pt(III) complexes possess a d7-d7 electronic configuration and exhibit intense phosphorescence under ambient conditions. Among them, Pt2a exhibits orange phosphorescence maximized at 618 nm in degassed dichloromethane solution (Φp ≈ 8.2%, τp ≈ 0.10 µs) and near-infrared (NIR) emission at 749 nm (Φp ≈ 10.1% τp ≈ 0.66 µs) in the crystalline powder and at 704 nm (Φp ≈ 33.1%, τp ≈ 0.34 µs) in the spin-coated neat film. An emission blue-shifted by more than 3343 cm-1 is observed under mechanically ground crystalline Pt2a, affirming intermolecular interactions in the solid states. Time-dependent density functional theory (TD-DFT) discloses the lowest-lying electronic transition of Pt2a-Pt2c complexes to be a bridging ligand-metal-metal charge transfer (LMMCT) transition. The long-lived triplet states of these dinuclear platinum(III) complexes may find potential use in lighting. Employing Pt2a as an emitter, high-performance organic light-emitting diodes (OLEDs) were fabricated with NIR emission at 716 nm (η = 5.1%), red emission at 614 nm (η = 8.7%), and white-light emission (η = 11.6%) in nondoped, doped (in mCP), and hybrid (in CzACSF) devices, respectively.

Versatile Pt(II) Pyrazolate Complexes: Emission Tuning via Interplay of Chelate Designs and Stacking Assemblies.

Three homoleptic Pt(II) metal complexes [Pt(imPz)2] (1), [Pt(imiz)2] (2), and [Pt(imMz)2] (3) were synthesized from the treatment of Pt(DMSO)2Cl2 and functional imidazolyl pyrazole in refluxing tetrahydrofuran (THF). Alternatively, the heteroleptic Pt(II) complexes [Pt(imPz)(fppz)] (4), [Pt(imiz)(fppz)] (5), and [Pt(imMz)(fppz)] (6) were obtained from the treatment of a common intermediate [Pt(fppzH)Cl2] with a corresponding imidazolyl chelate. Pt(II) complexes 1, 2, and 5 were studied by single-crystal X-ray diffraction to reveal the corresponding packing arrangement in their crystal lattices, among which both homoleptic complexes 1 and 2 formed monomeric species, while heteroleptic 5 aligned as a dimer with a nonbonding Pt···Pt contact of 3.574 Å. Subsequent photophysical examinations showed that the homoleptic 1-3 and heteroleptic 4-6 exhibited the structured sky-blue ππ* emission and structureless light-green-emitting metal-metal-to-ligand charge transfer (MMLCT) emission in the solid state, respectively. A shortened Pt···Pt interaction of approximately 0.34-0.35 nm was confirmed in thin films of all heteroleptic Pt(II) complexes 4-6 by grazing-incidence X-ray diffraction (GIXD) analyses. Finally, Pt(II) complex 6 was employed as a dopant in the fabrication of organic light-emitting diode (OLED) devices with varied doping ratios, among which OLEDs with only 1 wt % 6 in the SimCP host exhibited a maximum external quantum efficiency (EQE) of 5.8% and CIEx,y values of 0.20, 0.31. In contrast, OLEDs using a nondoped architecture (i.e., 100% of 6 in the emitting layer (EML)) achieved a maximum EQE of 26.8%, current efficiency (CE) of 91.7 cd A-1, and power efficiency (PE) of 80.1 lm·W-1 and CIEx,y values of 0.41, 0.55, manifesting their versatility in various degrees of stacking assemblies and hence facile color-tuning capability on OLEDs.

Roles of Ancillary Chelates and Overall Charges of Bis-tridentate Ir(III) Phosphors for OLED Applications.

A series of charge-neutral bis-tridentate Ir(III) complexes (1, 3, and 4) were prepared via employing three distinctive tridentate prochelates, that is, (pzptBphFO)H2, [(phpyim)H2·(PF6)], and [(pimb)H3·(PF6)2], which possess one dianionic pzptBphFO, together with a second monoanionic tridentate chelate, namely, (pzptBphFO)H, phpyim, and pimb, respectively. Moreover, a homoleptic, charge-neutral complex 2 was obtained by methylation of chelating (pzptBphFO)H of 1 in basic media, while closely related cationic complexes 5-7 were obtained by further methylation of the remaining pyrazolate unit of previously mentioned neutral complexes 2-4, followed by anion metatheses. All of these Ir(III) metal complexes showed a broadened emission profile with an onset at ∼450 nm, a result of an enlarged ligand-centered ππ* transition gap, but with distinct efficiencies ranging from 0.8% to nearly unity. Comprehensive spectroscopic and computational approaches were executed, providing a correlation for the emission efficiencies versus energy gaps and between the metal-to-ligand charge transfer/ππ* emitting excited state and upper-lying metal-centered dd quenching state. Furthermore, Ir(III) complexes 3 and 4 were selected as dopant emitters in the fabrication of sky-blue phosphorescent organic light-emitting diodes, affording maximum external quantum efficiencies of 16.7 and 14.6% with CIEx,y coordinates of (0.214, 0.454) and (0.191, 0.404) at a current density of 102 cd/m2, respectively. Hence, this research highlights an inherent character of bis-tridentate Ir(III) complexes in achieving high phosphorescence quantum yield at the molecular level.

Near-Infrared Emission Induced by Shortened Pt-Pt Contact: Diplatinum(II) Complexes with Pyridyl Pyrimidinato Cyclometalates.

Four diplatinum(II) complexes with the formula [Pt(pypm)(µ-Fn)]2 (2, 3a-c) bearing both a pyridine-pyrimidinate chelate and formamidinate bridge, where (pypm)H and FnH stand for 5-(pyridin-2-yl)-2-(trifluoromethyl)pyrimidine and functional formamidines with various substituents of iPr (n = 1), Ph (n = 2), C6H4tBu (n = 3), and C6H4CF3 (n = 4), were synthesized en route from a mononuclear intermediate represented by [Pt(pypm)Cl(F1H)] (1). Single-crystal X-ray diffraction studies confirmed the structure of 1 and 3a comprised of an individual "Pt(pypm)" unit and two "Pt(pypm)" units with a Pt···Pt distance of 2.8845(2) Å, respectively. Therefore, in contrast to the structured emission of mononuclear 1 with the first vibronic peak wavelength at 475 nm, all other diplatinum complexes with shortened Pt···Pt separation exhibited greatly red shifted and structureless metal-metal to ligand charge transfer (MMLCT) emission that extended into the near-infrared region in solid states. Their photophysical characteristics were measured under three distinctive morphological states (i.e., crystals, sublimed powders, and vacuum-deposited thin films) by steady-state UV-vis spectroscopy, while retention of Pt···Pt interactions in deposited thin films of 2 and 3a-c was confirmed using Raman spectroscopy, demonstrating lowered Pt···Pt stretching at 80-200 cm-1. Most importantly, complexes 3a-c exhibited a gradual red shift with the trends crystals < sublimed powders < vacuum-deposited thin films, a result of increased intermolecular π-π stacking interactions and Pt···Pt interactions, while crystalline samples exhibited the highest luminescence among all three morphological states due to the fewest defects in comparison to other morphologies. Finally, 3b was selected as a nondoped emitter for the fabrication of NIR-emitting OLEDs, giving an electroluminescence peak at 767 nm and a maximum external quantum efficiency of 0.14% with negligible roll-off.

Bis-Tridentate Iridium(III) Phosphors with Very High Photostability and Fabrication of Blue-Emitting OLEDs.

Sky-blue and blue-emitting, carbazolyl functionalized, bis-tridentate Ir(III) phosphors Cz-1-Cz-3 with bright emission and short radiative lifetime are successfully synthesized in a one-pot manner. They exhibit very high photostability against UV-vis irradiation in degassed toluene, versus both green and true-blue-emitting reference compounds, i.e., fac-[Ir(ppy)3] and mer-[Ir(pmp)3]. Organic light-emitting diodes (OLEDs) based on Cz-2 exhibit maximum external quantum efficiency (EQE) of 21.6%, EQE of 15.1% at 100 cd m-2, and with CIE x,y coordinates of (0.17, 0.25). This study provides a conceptual solution to the exceedingly stable and efficient blue phosphor. It is promising that long lifespan blue OLED based on these emitters can be attained with further engineering of devices suitable for commercial application.

Probe exciplex structure of highly efficient thermally activated delayed fluorescence organic light emitting diodes.

The lack of structural information impeded the access of efficient luminescence for the exciplex type thermally activated delayed fluorescence (TADF). We report here the pump-probe Step-Scan Fourier transform infrared spectra of exciplex composed of a carbazole-based electron donor (CN-Cz2) and 1,3,5-triazine-based electron acceptor (PO-T2T) codeposited as the solid film that gives intermolecular charge transfer (CT), TADF, and record-high exciplex type cyan organic light emitting diodes (external quantum efficiency: 16%). The transient infrared spectral assignment to the CT state is unambiguous due to its distinction from the local excited state of either the donor or the acceptor chromophore. Importantly, a broad absorption band centered at ~2060 cm-1 was observed and assigned to a polaron-pair absorption. Time-resolved kinetics lead us to conclude that CT excited states relax to a ground-state intermediate with a time constant of ~3 µs, followed by a structural relaxation to the original CN-Cz2:PO-T2T configuration within ~14 µs.

Iridium(III) Complexes Bearing Tridentate Chromophoric Chelate: Phosphorescence Fine-Tuned by Phosphine and Hydride Ancillary.

Functional 2-pyrazolyl-6-phenylpyridine chelates-namely, (pzpyphBu)H2 and (pzpyphCF3)H2 and phosphines-are successfully employed in the preparation of emissive Ir(III) metal complexes, for which the reaction with phosphine such as PPh3, PPh2Me, and PPh2(CH2Ph) afford corresponding Ir(III) complexes [Ir(pzpyphBu)(PPh3)2H] (1a), [Ir(pzpyphCF3)(PPh2R)2H] (2a-2c), R = Ph, Me, CH2Ph, which also show an equatorial coordinated hydride. In contrast, treatment with 1,2-bis(diphenylphosphino)benzene (dppb) and 1,2-bis(diphenylphosphino)ethane (dppe) yields the isomeric products [Ir(pzpyphBu)(dppb)H] (3a) and [Ir(pzpyphBu)(dppe)H] (3b), for which the distinctive, axial hydride undergoes rapid chlorination, forming chlorinated complexes [Ir(pzpyphBu)(dppb)Cl] (4a) and [Ir(pzpyphBu)(dppe)Cl] (4b), respectively. On the other hand, upon extensive heating of 2c, one of its coordinated PPh2(CH2Ph) exhibits benzyl cyclometalation and hydride elimination to afford [Ir(pzpyphCF3)(PPh2R)(PPh2R')] (5c and 6c) R = CH2Ph and R' = CH2( o-C6H4) as the kinetic and thermodynamic products, respectively. Their structural, photophysical, and electrochemical properties are examined and further affirmed by the computational approaches.

Sky Blue-Emitting Iridium(III) Complexes Bearing Nonplanar Tetradentate Chromophore and Bidentate Ancillary.

Tetradentate chelates bearing tripodal arranged terpyridine and a functional pyrazole unit (i.e., L1-H and L2-H) were employed in preparation of Ir(III) complexes [Ir(L1)Cl2] (1) and [Ir(L2)Cl2] (2); subsequent chloride-to-bipyrazolate substitution gave [Ir(L1)(bipz)] (3) and [Ir(L2)(bipz)] (4). Single-crystal X-ray structural studies on 1 and 3 showed the possession of a tetradentate chelate, whereas the remaining cis-sites are occupied by either dual chlorides or the bipz chelate, respectively. Sky blue organic light-emitting diode with peak efficiencies (10.1%, 19.8 cd·A-1, and 20.4 lm·W-1) was successfully fabricated using 3 (or 4) as dopant emitter, highlighting the potential application of this class of Ir(III) phosphor.

First N-Borylated Emitters Displaying Highly Efficient Thermally Activated Delayed Fluorescence and High-Performance OLEDs.

Despite the fast boom of thermally activated delayed fluorescence (TADF) emitters bearing borane-based acceptor, so far, no TADF emitter with a direct B-N linkage between N-donor and boryl acceptor has been reported. The latter should simplify the molecular architecture and hence facilitate the synthetic design and versatility. We report here the preparation and characterization of a new series of N-borylated compounds with functional acridine donor unit; namely: ACBM, PACBM, and SACBM. Spectroscopic studies were performed to explore their photophysical properties that exhibited prominent solvatochromism and thermally activated delayed fluorescence. The time-dependent DFT calculation indicated the involvement of substantial intramolecular charge transfer character for which HOMO and LUMO are spatially separated. For compound SACBM, fabrication of green emitting OLED gave CIE chromaticity of (0.22, 0.59) and maximum external quantum efficiency, luminance efficiency and power efficiency of 19.1%, 60.9 cd/A, and 43.6 lm/W, respectively, demonstrating for the first time the highly efficient OLEDs using N-borylated TADF emitters.

Functional Pyrimidine-Based Thermally Activated Delay Fluorescence Emitters: Photophysics, Mechanochromism, and Fabrication of Organic Light-Emitting Diodes.

A new series of molecules, T1-T4, possessing thermally activated delayed fluorescence (TADF) have been strategically designed and synthesized. Molecules T1-T4 contain the dimethyl acridine as the electron donor, which is linked to either symmetrical or unsymmetrical diphenyl pyrimidine as an acceptor. In comparison to the ubiquitous triazine acceptor, the selection of pyrimidine as an acceptor has advantages of facile functionalization and less stabilized unoccupied π orbitals, so that the energy gap toward the blue region can be accessed. Together with acridine donors, the resulting donor-acceptor functional materials reveal remarkable TADF properties. In the solid state, molecules T1-T4 all exhibit intriguing mechanochromism. The crystal structures, together with spectroscopy and dynamics acquired upon application of stressing, lead us to propose two types of structural arrangement that give distinct emission properties, one with and the other without TADF. Upon fabricating organic light-emitting diodes, the T1-T4 films prepared from sublimation all exhibit dominant TADF behavior; this accounts for their high performance: an electroluminescent emission at λ=490 nm, with an external quantum efficiency of 14.2 %, can be attained when T2 is used as an emitter.

Triboluminescence and Metal Phosphor for Organic Light-Emitting Diodes: Functional Pt(II) Complexes with Both 2-Pyridylimidazol-2-ylidene and Bipyrazolate Chelates.

We report the utilization of both pyrid-2-yl-imidazolylidene and dianionic bipz chelates as constituents in syntheses of a new series of charge-neutral Pt(II) complexes 1-4, among which complex 4 revealed remarkable triboluminescence, i.e., generation of photoemission upon grinding or cracking of the solid sample. The triboluminescence is found to be sensitive to the subtle changes of the associated substituents of pyrid-2-yl-imidazolylidene chelate, as verified by the disappearance of the triboluminescence for complexes 1-3. Alternatively, the well-ordered solid packing of 3, as indicated by the grazing incidence X-ray scattering experiment, serves as an ideal emitter for the fabrication of highly efficient OLEDs, rendering high external quantum efficienciy (25.9%) and luminesce efficiency (90 cd A-1) at the practical brightness of 100 cd m-2. The rather low roll-off in efficiency (24.4%, 85 cd A-1 at high brightness of 1000 cd m-2) is attributed to the short excited-state lifetime of 3 (∼800 ns) in the solid state, which in turn is associated with the MMLCT transition character.

Highly Twisted Dianchoring D-π-A Sensitizers for Efficient Dye-Sensitized Solar Cells.

Two new organic dyes-BPDTA and BTTA-possessing dual D-π-A units have been synthesized, characterized, and employed as efficient sensitizers for dye-sensitized solar cells. The two individual D-π-A, which are based on (E)-3-(5'-(4-(bis(4-(hexyloxy)phenyl)amino)phenyl)-[2,2'-bithiophen]-5-yl)-2-cyanoacrylic acid unit (D21L6), are connected directly between phenylene or thiophene within linear π-conjugated backbone to constitute a highly twisted architecture for suppressing the dye aggregation. The new dianchoring dyes exhibited pronounced absorption profile with higher molar extinction coefficient, which is consistent with the results obtained from density functional theory (DFT) calculations. The theoretical analysis also indicated that the charge transfer transition is mainly constituted of HOMO/HOMO-1 to LUMO/LUMO+1 that were found to be located on donor and acceptor segments, respectively. Theoretical calculations give the distance between two binding sites of 19.50 Å for BPDTA and 12.04 Å for BTTA. The proximity between two anchoring units of BTTA results in superior dye loading and, hence, higher cell efficiency. The BTTA-based device yielded an optimized efficiency of 6.86%, compared to 6.61% for the BPDTA-based device, whereas the model sensitizer D21L6 only delivered an inferior performance of 5.33% under similar conditions. Our molecular design strategy thus opens up a new horizon to establish efficient dianchoring dyes.

Room temperature blue phosphorescence: a combined experimental and theoretical study on the bis-tridentate Ir(iii) metal complexes.

A series of new bis-tridentate Ir(iii) complexes (1/1b, 2/2b and 3/3b) incorporating both bis(imidazolylidene)benzene and dianionic functional pyrazolyl (or phenyl) pyridine chelates have been synthesized, among which complexes 2 and 2b exhibit intense and structural sky-blue emission in both solution and solid states. In stark contrast, 1/1b is non-emissive in solution, while 3/3b reveals highly red-shifted emission with a featureless spectral profile. This variation in photophysics is associated with the interchange of metal-chelate bonding in the selected tridentate chelate, which affects both the crystal field stabilization energy and the ππ* transition character of the resulting Ir(iii) metal complexes. In 1/1b, the stabilized metal-centered (MC) dd excited states induce a dominant radiationless channel that accounts for the lack of emission in solution. The appreciable ligand-to-ligand charge transfer (LLCT) in 3/3b rationalizes its broad and featureless emission, which is different from the dominant intraligand ππ* transition in 2/2b. The combination of experimental and theoretical approaches thus provides fundamental insight into the influence of chelates as well as the metal-chelate interaction, which is beneficial for the future design of efficient and robust Ir(iii) phosphors for OLED applications.

Bis-Tridentate Ir(III) Complexes with Nearly Unitary RGB Phosphorescence and Organic Light-Emitting Diodes with External Quantum Efficiency Exceeding 31%.

A new class of neutral bis-tridentate Ir(III) metal complexes that show nearly unitary red, green, and blue emissions in solution is prepared and employed for the fabrication of both monochrome and white-emitting organic light-emitting diodes, among which a green device gives external quantum efficiency exceeding 31%.

Pyridyl Pyrrolide Boron Complexes: The Facile Generation of Thermally Activated Delayed Fluorescence and Preparation of Organic Light-Emitting Diodes.

The electron positive boron atom usually does not contribute to the frontier orbitals for several lower-lying electronic transitions, and thus is ideal to serve as a hub for the spiro linker of light-emitting molecules, such that the electron donor (HOMO) and acceptor (LUMO) moieties can be spatially separated with orthogonal orientation. On this basis, we prepared a series of novel boron complexes bearing electron deficient pyridyl pyrrolide and electron donating phenylcarbazolyl fragments or triphenylamine. The new boron complexes show strong solvent-polarity dependent charge-transfer emission accompanied by a small, non-negligible normal emission. The slim orbital overlap between HOMO and LUMO and hence the lack of electron correlation lead to a significant reduction of the energy gap between the lowest lying singlet and triplet excited states (ΔET-S ) and thereby the generation of thermally activated delay fluorescence (TADF).