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.

Near-infrared Fluorescent Probes with Long-acting Cyclic Monitoring and Effectively Eliminating Peroxynitrite.

Two through-bond energy transfer fluorescent probes with a dihydroxyl naphthyl-pyrenyl conjugated system were synthesized for long-acting cyclic monitoring and eliminating peroxynitrite (ONOO- ). The probes exhibit large Stokes shifts (230 or 280 nm) and the fluorescence at 620 or 652 nm rapidly change in response to continuously variable concentrations of ONOO- under physiological conditions. The probes show good reversibility and can rapidly monitor the concentration changes of ONOO- in real time. In addition, with the additions of the probes, the decomposition of ONOO- is greatly accelerated. Therefore, the probes can effectively eliminate the excess ONOO- as well as sensing it. The biological studies showed that the probes can effectively and reversibly eliminate both exogenous and endogenous ONOO- in-situ as well as sensing its changes in cells, which can help to maintain the normal physiological concentration of ONOO- in organisms. This is the first system that a probe achieves multifunction including real-time detection, long-acting cyclic monitoring and in-situ elimination, thereby maintaining a normal physiological balance for ONOO- .

AIE fluorescent probe based on tetraphenylethylene and morpholine-thiourea structures for detection of HClO.

As an important signal molecule in the living body, hypochlorous acid (HClO) participates in various physiological processes. However, excessive hypochlorous acid will cause some oxidative damage. The organic aggregation-induced emission luminogens (AIEgens) based on tetraphenylethylene (TPE) structures have recently become research hotspots as fluorescent probe materials. In this paper, a kind of water-soluble fluorescent probe TPE-M based on TPE and morpholine-thiourea structures were designed and synthesized for the detection of HClO. Due to the introduction of morpholine structures, the TPE-M showed excellent water solubility. The fluorescence properties of the TPE-M were strongly affected by the polarity of the solvent. Besides, the cation-anion and reactive oxygen species recognition experiments indicated that the fluorescent probe TPE-M displayed a single recognition characteristic for HClO because of the existence of thiourea structures. The limit of detection for HClO was calculated to be 0.25 µM. The particle size distribution measurement under the water phase revealed that the particle size of the TPE-M was mainly centered at 150 nm. The recognition mechanism of HClO by the probe TPE-M was proposed and explained by mass spectra and Gaussian calculation. Furthermore, a cell imaging experiment proved that the TPE-M probe successfully detected HClO in Hela cells.

Quinoline-based fluorescent probe for the detection and monitoring of hypochlorous acid in a rheumatoid arthritis model.

The development of effective bioanalytical methods for the visualization of hypochlorous acid (HOCl) in situ in rheumatoid arthritis (RA) directly contributes to better understanding the roles of HOCl in this disease. In this work, a new quinoline-based fluorescence probe (HQ) has been developed for the detection and visualization of a HOCl-mediated inflammatory response in a RA model. HQ possesses a donor-π-acceptor (D-π-A) structure that was designed by conjugating p-hydroxybenzaldehyde (electron donor) and 1-ethyl-4-methylquinolinium iodide (electron acceptor) through a C[double bond, length as m-dash]C double bond. In the presence of HOCl, oxidation of phenol to benzoquinone led to the red-shift (93 nm) of the adsorption and intense quenching of the fluorescence emission. The proposed response reaction mechanism was verified by high performance liquid chromatography (HPLC) and high-resolution mass spectroscopy (HRMS) titration analysis. The remarkable color changes of the HQ solution from pale yellow to pink enabled the application of HQ-stained chromatography plates for the "naked-eye" detection of HOCl in real-world water samples. HQ featured high selectivity and sensitivity (6.5 nM), fast response time (<25 s) to HOCl, reliability at different pH (3.0 to 11.5) and low cytotoxicity. HQ's application in biological systems was then demonstrated by the monitoring of HOCl-mediated treatment response to RA. This work thus provided a new tool for the detection and imaging of HOCl in inflammatory disorders.

Development of a new water-soluble fluorescence probe for hypochlorous acid detection in drinking water.

Responsive small-molecule fluorescence probe specific for target analyte detection is an emerging technology for food safety and quality analysis. In this work, we report a new water soluble small-molecule fluorescence probe (PG) for the detection of hypochlorous acid (HOCl) in drinking water samples. Probe PG was developed by coupling of a glucosamine into 10-methyl-10H-phenothiazine fluorophore with a HOCl-responsive C=N bond. The thioether is another recognition site that can be oxidized to be sulfoxide in water. Due to the specific reactions triggered by HOCl, probe PG's absorption band is blue shifted from 388 to 340 nm, and fluorescence at 488 nm is more than 55-fold enhanced. Probe PG features high fluorescence stability in PBS buffer with varied pH, fast response and high selectivity to HOCl. The application of the probe PG for HOCl detection in real-world samples is demonstrated by HOCl detection in drinking water, including tap water, purified water, and spring water samples. The recoveries of this method for HOCl detection in drinking water are in the range of 99.17-102.3%. This work thus provides a new method for HOCl detection in drinking water with high precision and accuracy.

Phthalide-containing poly(ether-imide)s based thermal rearrangement membranes for gas separation application.

The diamine monomer 3,3-bis[4-(3-hydroxy-4-amino-phenoxy)phenyl]phthalide (BHAPPP) was firstly synthesized by the nucleophilic substitution of 5-fluoro-2-nitrophenol and phenolphthalein, followed by a reduction reaction. A series of phthalide-containing poly(ether imide)s (PEI) were then prepared through the polycondensation of BHAPPP with six kinds of dianhydrides, including 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-biphenyl tetracarboxylic dianhydride (BPDA), 4,4'-oxydiphthalic dianhydride (ODPA), 1,2,3,4-cyclobutane tetracarboxylic dianhydride (CBDA) and pyromellitic dianhydride (PMDA), as well as thermal imidization. After further thermal treatment, the corresponding thermal rearrangement (TR) membranes were obtained. Due to the existence of the phthalide lactone ring, the PEIs probably underwent TR and crosslinking simultaneously. With the increase of thermal treatment temperature, the mechanical properties of the TR membranes dramatically decreased, but the gas separation properties obviously increased. When the PEIs were treated at 450 °C for 1 h, the CO2, H2, O2, N2 and CH4 permeability of TR(BHAPPP-6FDA) reached 258.5, 190.5, 38.35, 4.25 and 2.15 Barrers, respectively. Meanwhile, the CO2/CH4 selectivity of 120.2 sharply exceeded the 2008 Robeson limit, and O2/N2 selectivity was 9.02, close to the 2015 upper limit. Therefore, the TR membranes derived from phthalide-containing PEIs exhibit superior gas separation performance, andare expected to be applied in the field of gas separation.

A Silyl Ether Based Fluorescent Probe for Rapid Monitoring of Endogenous Peroxynitrite Concentration and Imaging in Living Cells through Multicolor Emission.

The peroxynitrite ion (ONOO- ) has important roles in many biological processes. We have developed a multicolor ONOO- -sensing probe (SiONNOH) that undergoes deprotonation and desilylation processes, which result in several changes in the emission wavelengths. In response to different concentrations of ONOO- , the probe exhibits fluorescence changes from pink (595 nm at 2 eq. ONOO- ) to green (540 nm at 6 eq. ONOO- ) via orange (3 eq. ONOO- ) and yellow (4 eq. ONOO- ) under physiological conditions until no fluorescence signal is observed after ONOO- is completely eliminated by lipoic acid. The probe shows the high selectivity for ONOO- and the limit of detection is calculated to be 1.27 µM. Moreover, the probe shows the capacity to monitor the concentration ranges of ONOO- through multicolor fluorescence in living cells, which will greatly facilitate the rapid detection of ONOO- concentration ranges by the naked eye under a UV light without any precision instrumentation.

A General Strategy for Through-Bond Energy Transfer Fluorescence Probes Combining Intramolecular Charge Transfer: A Silyl Ether System for Endogenous Peroxynitrite Sensing.

A general strategy is reported for developing through-bond energy transfer (TBET) fluorescence probes by combining intramolecular charge transfer (ICT). The strategy uses a coplanar donor-π-bridge-acceptor system (SiOPh-PyOH) without spirolactam. The off-on switch of TBET and ICT is controlled by coplanar structure changes in the sensing process instead of spirolactam ring-opening in traditional TBET probes. DFT calculations showed that the energy and charge transfers from SiOPh to PyOH are prohibited. Since the SiOPh has no fluorescence, the probe SiOPh-PyOH shows fluorescence properties similar to that of pyrene. After sensing ONOO- , the silyl ether is removed and the probe changes into - OPh-PyO- . Electron-donating ICT from OPh to PyO- induces a large redshift of emission to 594 nm (179 nm shift). TBET from OPh to PyO- ensures the probe exhibits a large pseudo-Stokes shift of 213 nm. Furthermore, the probe was successfully used in endogenous ONOO- detection. This study offers a new strategy for the construction of TBET probes emitting in the red region without spirolactam ring-opening, a new ONOO- sensing system using silyl ether as a reaction site, and a method for the deprotection of silyl ethers with ONOOH under mild conditions.

Efficient separation determination of protopanaxatriol ginsenosides Rg1, Re, Rf, Rh1, Rg2 by HPLC.

An efficient and flexible protocol was developed for simultaneous detection of the ginsenosides Rg1, Re, Rf, Rh1, and Rg2 in ginseng extract. In the analysis of white ginseng that contains no ginsenoside Rf, separation of the remaining ginsenosides was achieved within just 10 min under isocratic chromatographic conditions. For the analysis of red ginseng that contains ginsenoside Rf as a characteristic constituent, the gradient elution conditions were optimized. The method is based on high-pressure liquid chromatography employing a Shiseido UG 80 Capcell Pak NH2(4.6 mm I.D. × 250 mm, 5 µm)column and isocratic elution using acetonitrile (A) and water(B) in a ratio of 76: 24 (v/v), The optimal gradient elution conditions are as follows: 0-3 min, 89% A, 3-25 min, 89-84% A, 25-30 min, 84-82% A, 30-35 min, 82-76% A, then returning to 89% solvent A in 5 min. The flow rate was 0.80 mL min-1. The column temperature was set at 25℃ and the detection wavelength was at 203 nm. The working concentration ranges for ginsenoside Re, Rh1, Rg2, Rg1, and Rf were 0.23-1450.0 mg• L-1, 0.05-1130.0 mg• L-1, 0.11-687.0 mg• L-1, 0.051-1325 mg• L-1, and 0.55-800.0 mg• L-1, respectively. The method was validated for linearity, precision, and accuracy. And the further confirmation of five ginsenosides was conducted by QTOF-MS. Analysis of raw extracts of ginseng, white ginseng, and red ginseng for the five components showed satisfactory recovery.

Regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates for the synthesis of indolyl diketones.

A highly regioselective N-1 and C-2 diacylation of 3-substituted indoles with arylglyoxal hydrates to afford N-1 and C-2 indolyl diketones in moderate to good yields is described. Notably, the control of regioselectivity is achieved by small changes in the Cu catalyst, additive and solvent. Importantly, the intermediates for N-1 and C-2 diacylation were detected and two plausible pathways were also proposed.

Copper-catalyzed synthesis of indolyl diketones via C-H oxidation/diacylation of indoles with arylglyoxal hydrates.

An expedient protocol for Cu-catalyzed C-H oxidation/diacylation of indoles with arylglyoxal hydrates to construct indolyl diketones is developed. This methodology exhibits the synthetic utility of the synthesis of an indole-alkaloid 1,2-di(1H-indol-3-yl)ethane-1,2-dione and offers a straightforward means to produce different indolyl nitrogen-containing heterocycles such as indolyl quinoxaline, indolyl hydantoin and indolyl imidazole in high yields. Preliminary mechanistic studies indicate that two proposed pathways are involved in this process.

Visualization of Fluoride Ions In Vivo Using a Gadolinium(III)-Coumarin Complex-Based Fluorescence/MRI Dual-Modal Probe.

A new Gadolinium(III)-coumarin complex, DO3A-Gd-CA, was designed and prepared as a dual-modal probe for simultaneous fluorescence and relaxivity responses to fluoride ions (F-) in aqueous media and mice. DO3A-Gd-CA was designed by using Gd(III) center as an MRI signal output unit and fluoride binding site, and the 4-(diethylamino)-coumarin-3-carboxylic acid (CA) as a fluorescence reporter. Upon the addition of fluoride ions to the solution of DO3A-Gd-CA, the liberation of the coordinated CA ligand led to a 5.7-fold fluorescence enhancement and a 75% increase in the longitudinal relaxivity (r1). The fluorescent detection limit for fluoride ions was determined to be 8 µM based on a 3σ/slope. The desirable features of the proposed DO3A-Gd-CA, such as high sensitivity and specificity, reliability at physiological pH and low cytotoxicity enable its application in visualization of fluoride ion in mice. The successful in vivo imaging indicates that DO3A-Gd-CA could be potentially used in biomedical diagnosis fields.

Copper-catalyzed decarboxylative C3-acylation of free (N-H) indoles with α-oxocarboxylic acids.

An efficient Cu-catalyzed decarboxylative C3-acylation of free (N-H) indoles using α-oxocarboxylic acids as acylating agents has been developed. This method was compatible with a variety of functional groups and provided an attractive alternative access to 3-acylindoles in moderate to high yields.

Synthesis, photophysical, electrochemical and electroluminescent properties of a novel iridium(III) complex based on 2-phenylbenzo[d]oxazole derivative.

A new phosphorescent iridium (III) complex based on 2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole as main ligand, i.e. bis(2-(4-tert-butylphenyl)-5-methylbenzo[d]oxazole-N,C(2'))iridium(acetylacetonate) [(tmbo)2Ir(acac)], was synthesized for organic light-emitting diodes (OLEDs), and its photophysical, electrochemical and electroluminescent properties were investigated. The complex displayed strong phosphorescence emission, high decomposition temperature, short phosphorescent lifetime and reversible redox electrochemical behavior. The OLEDs based on (tmbo)2Ir(acac) as dopant emitter exhibited maximum luminance efficiency of 26.1cdA(-1) and high luminance of 16,445 cd m(-2). Interestingly, highly doped device based on (tmbo)2Ir(acac) showed high efficiency with negligible roll-off under a wide range of driving current density, which was mainly attributed to the effect of bulky steric hindrance of multi-methyl groups on this complex and its short phosphorescent lifetime.

3-(4-Meth-oxy-phen-yl)pyrido[2,3-b]pyrazine.

In the title mol-ecule, C(14)H(11)N(3)O, the benzene ring is twisted by 14.0 (2)° from the plane through the fused ring system. In the crystal, π-π inter-actions [centroid-centroid distances = 3.609 (1), 3.639 (1) and 3.735 (1) Å] form stacks of mol-ecules propagating along the b axis. The crystal packing is further stabilized by weak inter-molecular C-H⋯O and C-H⋯N hydrogen bonds.

4-[4,5-Bis(pyridin-2-yl)-1H-imidazol-2-yl]phenol monohydrate.

In the title hydrate, C(19)H(14)N(4)O·H(2)O, the dihedral angle between the two pyridine rings is 38.0 (2)°. The dihedral angle between the imidazole and benzene rings is 25.3 (2)°. The crystal structure is stabilized by inter-molecular O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds.

Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated.

An expeditious aqueous Suzuki-Miyaura method for the substituted aryl heterocyclics.

Palladium-catalyzed cross-coupling reactions utilizing aryl halides have become a widely used strategy for the formation of new carbon-carbon bonds and in particular for the synthesis of biaryls. The replacement of expensive, toxic, and flammable organic solvents by water is highly desirable for reducing costs and for developing environmentally benign synthetic reactions that facilitate catalyst recycling. Herein, we report an efficient Suzuki-Miyaura cross-coupling reaction using a variety of heterocyclic halides in neat water. Employing air- and moisture-stable palladium-phosphinous acid catalyst [(t-Bu)2P(OH)]2PdCl2(POPd) allows formation of substituted aryl heterocyclics in moderate to high yields. The organic cosolvents are not required. The feasibility of catalyst recycling has also been demonstrated.

cis-Bis[2-(1,3-benzothia-zol-2-yl)-1-(4-fluoro-phen-yl)ethen-yl](pentane-2,4-dionato-κO,O')iridium(III).

In the title compound, [Ir(C(15)H(9)FNS)(2)(C(5)H(7)O(2))], the Ir atom is hexa-coordinated by three chelating ligands, with two cyclo-metalated 2-(1,3-benzothia-zol-2-yl)-1-(4-fluoro-phen-yl)ethenyl ligands showing N,C-bidentate coordination and an O,O'-bidenate pentane-2,4-dionate anion, thereby forming a distorted octa-hedral enviroment.