Exploring redox properties of a 3D Co-based framework with bis(triarylamine) terphenyl as a redox-active linker.

A 3D Co-based metal-organic framework has been prepared, which contains a bis(triarylamine) with terphenyl units as a redox-active linker. Manipulation of the redox events via the electrochemical method confirmed that charge hopping is dominant within the 3D framework. Investigation of the in situ spectroelectrochemical properties within the structure leads to the formation of mono and dual radical cations obtained reversibly in two-steps due to the presence of two redox-active sites.

Quantum Dot-Vitrimer Composites: An Approach for Reprocessable, Self-Healable, and Sustainable Luminescent Materials.

Quantum dots (QDs) are of great concern in many fields. However, they suffer from high toxicity and may lead to environmental pollution. We report the development of a QD-vitrimer composite with reprocessable, self-healable, and sustainable properties. Our QD-vitrimer composite reveals fine transparency and highly uniform QDs distribution without significant aggregation. The photoluminescence quantum yield (PLQY) is basically about four times higher than the commercial QD films. The QD-vitrimer composites can be recycled at least three times without any significant loss in structure and luminescence efficiency. A prototype light-emitting diode device is fabricated to demonstrate the promising potential of QD-vitrimer composites in real application. This research sheds light on developing environmentally friendly luminescent materials and opens up an avenue for designing advanced nanomaterials-vitrimer composites.

ortho-Lithiation driven one-pot synthesis of quinazolines via [2 + 2 + 2] cascade annulation of halofluorobenzenes with nitriles.

A one-pot synthesis of 2,4-disubstituted quinazoline derivatives from halofluorobenzenes with nitriles was reported, via sequential nucleophilic addition and SNAr reaction. The advantages of the present approach are transition metal free, easy to operate, and all the starting materials are commercially available.

Conductivity and photoconductivity in a two-dimensional zinc bis(triarylamine) coordination polymer.

We report the synthesis and characterization of a 2D semiconductive and photoconductive coordination polymer. [Zn(TPPB)(Cl2)]·H2O (1) (TPPB = N 1,N 1,N 4,N 4-tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine) consists of a TPPB redox-active linker with bis(triarylamine) as the core. It consists of two redox sites connected with a benzene ring as a bridge. Thus, this forms an extended conjugation pathway when the TPPB ligand is coordinated with the Zn2+ metal ions. The single crystal conductivity measurement revealed conductivity of 1 to be in the range of 0.83 to 1.9 S cm-1. Band structure analysis predicted that 1 is a semiconductor from the delocalization of electronic transport in the network. The computational calculations show the difference in charge distribution between holes and electrons, which led to spatial separation. This implies a long charge carrier lifetime as indicated by lifetime measurement. Incorporating a bis(triarylamine)-based redox-active linker could lead to a new semiconductive scaffold material with photocatalytic applications.

Sustainable Synthesis of Cyclic Carbonates from Terminal Epoxides by a Highly Efficient CaI2/1,3-Bis[tris(hydroxymethyl)-methylamino]-propane Catalyst.

The nonstopping increment of atmospheric carbon dioxide (CO2) concentration keeps harming the environment and human life. The traditional concept of carbon capture and storage (CCS) is no longer sufficient and has already been corrected to carbon capture, utilization, and storage (CCUS). CCUS involves significant CO2 utilization, such as cyclic carbonate formation, for its cost effectiveness, less toxicity, and abundant C1 synthon in organic synthesis. However, the high thermodynamic and kinetic stability of CO2 limits its applications. Herein, we report a mild, efficient, and practical catalyst based on abundant, nontoxic CaI2 in conjunction with biocompatible ligand 1,3-bis[tris(hydroxymethyl)-methylamino]-propane (BTP) for CO2 fixation under atmospheric pressure with terminal epoxides to give the cyclic carbonates. The Job plot detected the 1:1 Ca2+/BTP binding stoichiometry. Furthermore, formation of a single crystal of the 1:1 Ca2+/BTP complex was confirmed by single-crystal X-ray crystallography. The bis(cyclic carbonate) products exhibit potentials for components in the non-isocyanate polyurethanes (NIPUs) process. Notably, this protocol shows attractive recyclability and reusability.

Reversible Electroactive Behavior in a Zn-Based Metal-Organic Framework via Mild Oxidation Potential.

This work describes the synthesis and characterization of a Zn-based metal-organic framework, [Zn2(TTPA)(SDB)2·(DMF)(H2O)]n (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, SDB = 4,4'-sulfonyldibenzoate). A newly designed strategy with a redox-active linker, TTPA, and mediated by a V-shaped carboxylic linker with Zn2+ metal ions resulted in an electroactive framework. The V-shaped carboxylic linker with Zn2+ metal ions forms linear struts interlinked by two of the side-arms of the TTPA ligands to form a square grid network. The interior of the grid is enough to accommodate the third side-arm of the TTPA ligands, acting as a confinement grid that provides steric protection when triarylamine radical cations were generated. In addition, modular packing of axially aligned TTPA ligand facilitates charge propagation. Optical switching studies confirmed that 1 is electrochemically reversible up to 48 cycles at a potential of 0.9 V vs Fc/Fc+. Framework 1 remained robust after annealing at 180 °C for 20 h as corroborated by the PXRD. These studies confirm the importance of crystal engineering design, where electron transfer is possible in a two-ligand approach.

Bistriazoles with a Biphenyl Core Derivative as an Electron-Favorable Bipolar Host of Efficient Blue Phosphorescent Organic Light-Emitting Diodes.

High-quality host materials are indispensable for the construction in the emitting layer of efficient organic light-emitting diodes (OLEDs), especially in a guest and host system. The good carrier transport and energy transfer between the host and emitters are out of necessity. In this work, a wide bandgap and bipolar organic compound, 2,2'-bis(4,5-diphenyl-(1,2,4)-triazol-3-yl)biphenyl (BTBP), conjugating two electron-transporting triazole moieties on a hole-transporting biphenyl core, was synthesized and characterized. The wide bandgap of 4.0 eV makes the promise in efficient energy transfer between the host and various color emitters to apply as the universal host, especially for blue emitters. The close electron and hole mobilities perform the same order of 10-5 cm2·V-1·s-1, identified as bipolar behavior and benefited for carrier balance at low bias. Although carrier transportation belongs to bipolar behavior at a low electrical field, the electron mobility is much faster than the hole one at a high electrical field and belongs to electron-transporting behavior. Employing the BTBP as the host matrix mixed with a phosphor dopant, iridium(III)bis[4,6-di-fluorophenyl-pyridinato-N,C2]picolinate, a high-efficiency sky-blue phosphorescent organic light-emitting diode (OLED) was achieved with a maximum current efficiency of 65.9 cd/A, maximum power efficiency of 62.8 lm/W, and maximum external quantum efficiency of 30.2%.

One-Pot CuI/DBU-Catalyzed Carboxylative Cyclization toward Oxazolidinones Using Recyclable Molecular Sieves as Efficient Promoters for Fixation of CO2 in Water Medium.

An efficient one-pot synthesis of oxazolidinones was developed through CuI/DBU/MS joint system-catalyzed carboxylative cyclization of arylacetylene, arylaldehyde, and arylamine in water medium under a 1 atm carbon dioxide (CO2) atmosphere. The 4 Šmolecular sieves (MSs) were added to improve CO2 capture and facilitate carboxylation to give the products in high yields. The CuI/DBU/MS system is robust and highly effective for the reactions with different substrates, and some target products were obtained in an excellent yield of ∼96%, with no side products in the final step.

An Electroactive Zinc-based Metal-Organic Framework: Bifunctional Fluorescent Quenching Behavior and Direct Observation of Nitrobenzene.

This work reports on the facile synthesis, characterization, and electroactivity of a zinc-based [Zn3(TTPA)2(DHTP)3]·2DMF (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, DHTP = dihydroxylterepthate) metal-organic framework, which has multifunctional properties due to its electroactive framework, permanent porosity, robust structure, and fluorescent nature. Topology analyses indicate that 1 contains a 3,4,4-c net. Sorption studies indicate that 1 is a suitable adsorbent for CO2 with a capacity of 10.2 wt % at 298 K; the capacity increased to 16.7 wt % at a lower temperature, 273 K. The incorporation of the redox-active TTPA ligand as an electron donor renders 1 to be an electroactive framework. The generation of radical cations from the chemical oxidation of 1 resulted in fluorescent quenching. The combination of porosity, fluorescence, and electroactivity in one entity suggests that 1 could serve as a sensing material for the detection of nitrobenzene. Exposing nitrobenzene to 1 quenches the fluorescent via host-guest interactions. The detection site of nitrobenzene in framework 1 was confirmed by single-crystal X-ray diffraction, [Zn3(TTPA)2(DHTP)3]·(H2O)(DMF)(2NB) or 1 ⊂ NB. In addition, the inclusion of nitrobenzene into the framework 1 stabilized the disordered molecules via strong hydrogen bonding. These findings indicate that versatile MOFs with multifunctional properties can be realized via a systematic design.

Spectroelectrochemical studies of the redox active tris[4-(triazol-1-yl)phenyl]amine linker and redox state manipulation of Mn(ii)/Cu(ii) coordination frameworks.

This work describes the successful incorporation of a redox active linker, tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine (TTPA) into Mn(ii)/Cu(ii) based coordination frameworks. Solution state in situ spectroelectrochemistry of EPR and UV/Vis/NIR of the TTPA ligand were measured to gain a deeper understanding of the charge delocalization of the triphenylamine backbone. The assignments of the absorption bands for the radical cations in UV/Vis/NIR spectroelectrochemistry were supported by DFT calculations. For Mn(ii)/Cu(ii) based coordination frameworks, solid state electrochemical and in situ spectroelectrochemical methods were applied to elucidate the accessible redox states and the optical properties of the frameworks. The findings provide a basic comprehension of the interconversion of different redox states and how an electroactive framework can be potentially used in applications of electrochromic and optical devices.

Carrier Transport and Recombination Mechanism in Blue Phosphorescent Organic Light-Emitting Diode with Hosts Consisting of Cabazole- and Triazole-Moiety.

In this study, we demonstrated a blue phosphorescent organic light-emitting diode (BPOLED) based on a host with two carbazole and one trizole (2CbzTAZ) moiety, 9,9'-(2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-1,3-phenylene)bis(9H-carbazole), that exhibits bipolar transport characteristics. Compared with the devices with a carbazole host (N,N'-dicarbazolyl-3,5-benzene, (mCP)), triazole host (3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, (TAZ)), or a physical mixture of mCP:TAZ, which exhibit hole, electron, and bipolar transport characteristics, respectively, the BPOLED with the bipolar 2CbzTAZ host exhibited the lowest driving voltage (6.55 V at 10 mA/cm2), the highest efficiencies (maximum current efficiency of 52.25 cd/A and external quantum efficiency of 23.89%), and the lowest efficiency roll-off, when doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) as blue phosphor. From analyses of light leakage of the emission spectra of electroluminescence, transient electroluminescence, and partially doped OLEDs, it was found that the recombination zone was well confined inside the emitting layer and the recombination rate was most efficient in a 2CbzTAZ-based OLED. For the other cases using mCP, TAZ, and mCP:TAZ as hosts, electrons and holes transported with different routes that resulted in carrier accumulation on different organic molecules and lowered the recombination rate.

Simple Molecular-Engineering Approach for Enhancing Orientation and Outcoupling Efficiency of Thermally Activated Delayed Fluorescent Emitters without Red-Shifting Emission.

The inclusion of a tetraphenylbenzene (4Ph) unit in thermally activated delayed fluorescence emitters is demonstrated as a novel strategy for greatly enhancing the horizontally oriented alignment of the emitters without shifting the emission spectrum to longer wavelengths. Doping of blue-emitting 4PhOXDDMAC or greenish-blue-emitting 4PhOXDPXZ into o-DiCbzBz host layers yielded much higher degrees of horizontally oriented alignment for the emitter (up to 92%) compared to those when the 4Ph unit was excluded (69 and 75%, respectively). The enhanced alignment results in high outcoupling efficiencies of 24 and 35% in organic light-emitting diodes based on 4PhOXDDMAC and 4PhOXDPXZ, respectively, and boosts the external quantum efficiencies to values (8.8 and 29.2%, respectively) that are higher than what would be expected for randomly oriented emitters (outcoupling efficiency of 20%). These enhancements are achieved while avoiding the redshift that often occurs using the common strategy of increasing molecular length and, thereby, conjugation, to increase orientation.

Construction of Highly Efficient Carbazol-9-yl-Substituted Benzimidazole Bipolar Hosts for Blue Phosphorescent Light-Emitting Diodes: Isomer and Device Performance Relationships.

Four isomers of carbazol-9-yl-substituted 1,2-diphenylbenzimidazole at 7, 6, 5, and 4 positions, named as 1-CbzBiz, 2-CbzBiz, 3-CbzBiz, and 4-CbzBiz, respectively, have been synthesized. Instead of having an identical molecular weight, the CbzBiz's have their glass transition temperatures ( Tg) spanning a large range from 53 to 90 °C. Their Tg and melting point ( Tm) basically obey the Boyer-Kauzmann rule ( Tg = g· Tm with g ≈ 0.7) on the absolute temperature scale (in kelvins). However, while 1-CbzBiz and 4-CbzBiz demonstrate a small g value of 0.66, which is significantly smaller than other common organic glass molecules, 3-CbzBiz shows an unexpectedly high g value of 0.73, implying higher intermolecular interactions in the glass. These CbzBiz's are suitable hosts for bis[2-(4,6-difluorophenyl)pyridinato- C2, N](picolinato)iridium(III) (FIrpic) in phosphorescence organic light-emitting diodes (PhOLEDs). The optimized PhOLED of indium tin oxide/4,4'-cyclohexylidenebis[ N, N-bis(4-methylphenyl)benzenamine]/4Cbz/4-CbzBiz-FIrpic(15%)/diphenylbis(4-(pyridin-3-yl)phenyl)silane/LiF-Al shows a maximum brightness of 18 760 cd/m2, a current efficiency of 64.1 cd/A, and the external quantum efficiency of 30.9%.

Efficient Triplet-Triplet Annihilation Upconversion in an Electroluminescence Device with a Fluorescent Sensitizer and a Triplet-Diffusion Singlet-Blocking Layer.

Solid-state triplet-triplet annihilation upconversion (TTAUC) blue emission in an electroluminescence device (i.e., an organic light-emitting diode (OLED)) is demonstrated. A conventional green fluorophore, tris-(8-hydroxyquinoline)aluminum (Alq3 ), is employed as the sensitizer that generates 75% triplet under electrical pumping for the blue triplet-triplet annihilation emitter, 9,10-bis(2'-naphthyl) anthracene (ADN), with the heterojunction bilayer structure. The operation lifetime is elongated both for ADN blue (4.1x) and Alq3 green (34.8%) emission due to efficient use of excitons and separation of recombination and emission zone. To reduce the singlet quenching (SQ) of blue TTAUC signal by the Alq3 sensitizer with lower bandgap, 1-(2,5-dimethyl-4-(1-pyrenyl)phenyl)pyrene (DMPPP) is inserted between the Alq3 and ADN as a triplet-diffusion-and-singlet-blocking layer. DMPPP exhibits triplet energy close to Alq3 and higher than ADN, as well as higher singlet energy than both Alq3 and ADN. It allows triplet diffusion from Alq3 to ADN, but blocks the SQ of the blue TTAUC signal by Alq3 . 86.1% intrinsic efficiency of TTAUC is demonstrated in this trilayer (Alq3 /DMPPP/ADN) OLED.

A Co(ii) framework derived from a tris(4-(triazol-1-yl)phenyl)amine redox-active linker: an electrochemical and magnetic study.

A new 3D coordination polymer {[Co2(µ-OH2)(TTPA)(DTDN)2·DMF]·H2O}n (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, DTDN = 6,6'-dithiodinicotinate) was synthesised and characterised. The redox properties of this framework were elucidated by solid state electrochemical and spectroelectrochemical data. This is the first investigation of the redox behaviour of TTPA in coordination polymers. Furthermore, the incorporation of a paramagnetic Co(ii) metal ion into the framework caused 1 to show spin-flop behaviour as the result of a field-induced magnetic transition. The incorporation of two flexible ligands and Co(ii) metal ions represents a feasible approach for the advancement of multifunctional materials.

Modeling of carrier transport in organic light emitting diode with random dopant effects by two-dimensional simulation.

To model the carrier transport in organic light-emitting diodes (OLEDs) with random dopant effects in the emitting layer, two-dimensional simulation was used. By including the Gaussian shape density of states and field-dependent mobility in the Poisson and drift-diffusion solver, the carrier transport, trapping in the dopant state, and radiative recombination were accurately modeled. To examine the model, the current-voltage characteristics of organic light-emitting devices were compared. The host material in the emitting layer was 2,2-bis(1-phenyl-1H-benzo[d]imidazol-2-yl)biphenyl (BImBP), which was doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) at various concentrations. By including the random doping model, the trend of mobility was altered and the radiative efficiency fitted experimental values well.

Cost-effectiveness of an influenza vaccination program offering intramuscular and intradermal vaccines versus intramuscular vaccine alone for elderly.

BACKGROUND: Intradermal (ID) injection is an alternative route for influenza vaccine administration in elderly with potential improvement of vaccine coverage. This study aimed to investigate the cost-effectiveness of an influenza vaccination program offering ID vaccine to elderly who had declined intramuscular (IM) vaccine from the perspective of Hong Kong public healthcare provider. METHODS: A decision analytic model was used to simulate outcomes of two programs: IM vaccine alone (IM program), and IM or ID vaccine (IM/ID program) in a hypothetic cohort of elderly aged 65 years. Outcome measures included influenza-related direct medical cost, infection rate, mortality rate, quality-adjusted life years (QALYs) loss, and incremental cost per QALY saved (ICER). Model inputs were derived from literature. Sensitivity analyses evaluated the impact of uncertainty of model variables. RESULTS: In base-case analysis, the IM/ID program was more costly (USD52.82 versus USD47.59 per individual to whom vaccine was offered) with lower influenza infection rate (8.71% versus 9.65%), mortality rate (0.021% versus 0.024%) and QALYs loss (0.00336 versus 0.00372) than the IM program. ICER of IM/ID program was USD14,528 per QALY saved. One-way sensitivity analysis found ICER of IM/ID program to exceed willingness-to-pay threshold (USD39,933) when probability of influenza infection in unvaccinated elderly decreased from 10.6% to 5.4%. In 10,000 Monte Carlo simulations of elderly populations of Hong Kong, the IM/ID program was the preferred option in 94.7% of time. CONCLUSIONS: An influenza vaccination program offering ID vaccine to elderly who had declined IM vaccine appears to be a highly cost-effective option.

Orthogonally Substituted Benzimidazole-Carbazole Benzene As Universal Hosts for Phosphorescent Organic Light-Emitting Diodes.

The novel ambipolar hosts of o-CbzBz and o-DiCbzBz contain carbazole and benzimidazole through an ortho-connection. The orthogonal conformations cause the triplet state to be confined at the carbazole units to secure efficient energy transfer. The phosphorescent organic light-emitting diodes (PhOLEDs) show a high current efficiency, power efficiency, and low efficiency roll-off. o-DiCbzBz can be used as a host for sky-blue, green, and orange-red PhOLEDs, giving 57.5, 78.4, and 60.3 cd/A, respectively.

Pyrrolo-[3,2-b]pyrroles for Photochromic Analysis of Halocarbons.

Dramatic photochromic-change of 2,5-bis(triphenylamine)-substituted N,N'-diphenylpyrrolo-[3,2-b]pyrrole (1) with halocarbons provides an effective route for halocarbon analysis with the naked eye. The visual detection range can reach as low as 10(-4) ∼ 10(-5) M (1-10 ppm) in CH3CN. This method can also be applied for detection of CHCl3 in water. Fabrication of a disposable paper test cartridge along with using a camera flash as the light source allows on-site halocarbon detection in seconds. Quantitative analysis for CHCl3 and CH2Cl2 have also been demonstrated.

Design, synthesis, photophysical and electrochemical properties of 2-(4,5-diphenyl-1-p-aryl-1H-imidazol-2-yl)phenol-based boron complexes.

New hybrid organic-inorganic boron compounds using an imidazole core have been readily synthesized by a two-step procedure from commercially available simple starting materials. All boron compounds were fully characterized by multinuclear NMR spectroscopy, LC-MS, thermogravimetric analysis, cyclic voltammetry and single crystal X-ray diffraction analysis (for & ). The photoluminescence measurements of revealed distinct emission peak maxima located at 378, 379 and 387 nm, respectively. Electroluminescent devices fabricated using these boron compounds () suggest that the boron compounds are capable of transporting electrons. A maximum brightness of 6450 cd m(-2) at 12.5 V was realized when compound was used as an electron-transporting material.