Dual-Responsive Near-Infrared BODIPY-Based Fluorescent Probe for the Detection of F- and HClO in Organisms.

Fluoride anions (F-) play a crucial role in human physiological processes. However, excessive intake of F- would affect oxygen metabolism and promote the generation of oxygen-free radicals. Hence, it is essential to develop a precise and efficient fluorescent probe for visualizing F--induced oxidative stress. In this work, we developed the first bifunctional BODIPY-based fluorescent probe dfBDP with p-tert-butyldimethylsilanolate benzyl thioether as the sensing site for the detection of F- and HClO via two distinct reactions, the self-immolative removal and the thioether oxidation, which generate the sensing products with two nonoverlap fluorescence bands: 800-1200 and 500-750 nm, respectively. The probe dfBDP displays rapid response, high specificity, and sensitivity for the detection of F- (LOD, 316.2 nM) and HClO (LOD, 33.9 nM) in vitro. Cellular imaging reveals a correlation between F--induced oxidative stress and the upregulation of HClO. Finally, probe dfBDP was employed to detect F- and HClO in mice under the stimulation of F-. The experimental results display that the level of HClO elevates in the liver of mice.

Visible-light-promoted difluoroamidated oxindole synthesis via electron donor-acceptor complexes.

A method involving a metal-free visible-light-promoted synthesis was developed for the construction of difluoroalkylated oxindoles with N-phenylacrylamides and bromodifluoroacetamides as starting materials in the presence of N,N,N',N'-tetramethylethylenediamine (TMEDA). Twenty-four examples of the photochemical reaction were successfully performed, with good yields (44-99%) and excellent substrate adaptability. Mechanistic studies showed that the visible-light-promoted reaction involved a radical addition to N-phenylacrylamide, intramolecular cyclization, dehydrogenation, and rearomatization. The difluoroacetamide radical was produced as a result of electron transfer to bromodifluoroacetamides from the electron donor TMEDA in their electron-donor-acceptor (EDA) complexes under visible light irradiation. This protocol is a promising photochemical method due to its advantages of mild conditions, simple operation, wide substrate scope and high yields. And the obtained products may have great potential in the field of medicine.

Bifunctional Fluorescent Probes for the Detection of Mustard Gas and Phosgene.

Mustard gas [sulfur mustard (SM)] and phosgene are the most frequently used chemical warfare agents (CWAs), which pose a serious threat to human health and national security, and their rapid and accurate detection is essential to respond to terrorist attacks and industrial accidents. Herein, we developed a fluorescent probe with o-hydroxythioketone as two sensing sites, AQso, which can detect and distinguish mustard gas and phosgene. The dual-sensing-site probe AQso reacts with mustard gas to form a cyclic product with high sensitivity [limit of detection (LOD) = 70 nM] and is highly selective to SM over phosgene, SM analogues, active alkylhalides, acylhalides, and nerve agent mimics, in ethanol solutions. When encountering phosgene, AQso rapidly converts to cyclic carbonate, which is sensitive (LOD = 14 nM) and highly selective. Their sensing mechanisms of AQso to mustard gas and phosgene were well demonstrated by separation and characterization of the sensing products. Furthermore, a facile test strip with the probe was prepared to distinguish 2-chloroethyl ethyl sulfide (CEES) and phosgene in the gas phase by different fluorescence colors and response rates. Not using the complicated instrument, the qualitative and quantitative detection of CEES or phosgene can be achieved only by measuring the red-green-blue (RGB) channel intensity of the test strip after being exposed to CEES or phosgene gas by the smartphone with an RGB color application.

Visible Light-Driven Decarboxylative Alkylation of Aldehydes via Electron Donor-Acceptor Complexes of Active Esters.

There are some synthesis methods from widely available aldehydes to the corresponding ketones, however, they involved in multistep reactions with Grignard's reagents or transition metal catalysts. In this paper, we have developed photocatalyst-free and visible light-driven decarboxylative alkylation of pyridinaldehydes. The photochemical reactions are initiated via photoinduced single electron transfer from triethylamine to N-hydroxyphthalimide esters in electron donor-acceptor complexes. This photochemical method can achieve to translate 15 pyridinaldehydes and 11 2-quinolinaldehydes to the corresponding ketones. Furthermore, this strategy can also achieve two other transformations, disulfanes to aryl sulfides and a styrene sulfone to the alkyl-substituted alkene.

Sensitive and Visual Detection of Phosgene by a TICT-Based BODIPY Dye with 8-(o-Hydroxy)aniline as the Active Site.

Phosgene and its substitutes (diphosgene and triphosgene) are widely utilized as chemical industrial materials and chemical warfare agents and pose a threat to public health and environmental safety due to their extreme toxicity. Research efforts have been directed to develop selective and sensitive detection methods for phosgene and its substitutes. In this paper, we have prepared two BODIPY-based fluorescent probes, o-Pah and o-Pha, which are two isomers with different active sites, ortho-aminohydroxy (3',4' or 4',3') phenyls at meso position of BODIPY, and compared their sensing performance toward triphosgene. The probe with o-(4'-amino-3'-hydroxyl), o-Pha, exhibits better sensing performance over the o-(3'-amino-4'-hydroxyl), o-Pah, for instance, a lower limit of detection (LOD) (0.34 nm vs. 1.2 nm), and more rapid response (10 s vs. 200 s). Furthermore, based on the above comparative studies, a red-fluorescence probe o-Phae has been constructed through extending 3,5-conjugation of o-Pha. The probe o-Phae displays rapid response (60 s), high sensitivity to triphosgene (LOD=0.88 nm), and high selectivity for triphosgene over relevant analytes including nitric oxide. Finally, a facile test strip for phosgene was fabricated by immobilizing o-Phae in a polyethylene oxide membrane for sensitive (<2 ppm) and selective detection of phosgene in the gas phase.

Rapid and Effective Reaction of 2-Methylpyridin-N-oxides with Triphosgene via a [3,3]-Sigmatropic Rearrangement: Mechanism and Applications.

A facile and effective synthesis of 2-chloromethylpyridines was developed by a one-pot reaction of 2-alkylpyridin-N-oxides and triphosgene at room temperature. As starting materials, N-oxides of 2-alkylpyridine derivatives, including 2-alkylpyridines, 2-methyl quinolines, and phenanthroline, can react rapidly with triphosgene in the presence of triethylamine, affording 2-chloromethylpyridines in good to excellent yields (52-95%). Using the 2-methylquinoline substrate for the mechanistic study, it has been well demonstrated that the chlorination reaction undergoes a [3,3]-sigmatropic rearrangement, which can be observed as a reversible process by monitoring the intermediates. Moreover, the chlorination reaction can be used to construct a rapid and sensitive fluorescent probe for the detection of phosgene.

Visible-Light-Mediated Alkylation of Thiophenols via Electron Donor-Acceptor Complexes Formed between Two Reactants.

A metal-free, photocatalyst-free, photochemical system was developed for the direct alkylation of thiophenols via electron donor-acceptor (EDA) complexes (KEDA = 145 M-1) between two reactants, N-hydroxyphthalimide esters as acceptors and thiophenol anions as donors, in the presence of a tertiary amine. The EDA complexes in the reaction system have a broad range of visible-light absorption (400-650 nm) and can trigger the reaction effectively under sunlight.

Regioselective benzoyloxylative dearomatization of naphthols by benzoyl peroxide under catalyst-free conditions.

A direct regioselective benzoyloxylative dearomatization of both α- and ß-naphthols by benzoyl peroxide under an air atmosphere, and radical inhibitor- and catalyst-free conditions at room temperature is described. The methodology provides a new efficient strategy for the construction of α-ketol derivatives bearing an oxo-quaternary carbon center from naphthols with good to excellent yields.

Fluorescent Chemosensor for Dual-Channel Discrimination between Phosgene and Triphosgene.

As highly toxic and accessible chemical reagents, phosgene and triphosgene have become a serious threat to public safety. So, it is highly desirable to develop facile methods to detect and recognize them. In this article, a novel fluorescent chemosensor, Phos-4, has been constructed with 1,8-naphthalimide as the fluorophore and 2-(2-aminophenyl)imidazol as the recognition sites for discrimination between phosgene and triphosgene in a dual-channel mode for the first time. Owing to the difference in electrophilicity between chlorocarbonyl and trichloromethoxycarbonyl, the sensing reaction of Phos-4 with phosgene undergoes two carbamylations to afford a cyclic product with green fluorescence, and only one carbamylation occurs for triphosgene to form a noncyclic product with blue fluorescence. The sensor Phos-4 exhibits high sensitivity (the limit of detection, 3.2 nM, for phosgene, and 1.9 nM, for triphosgene) and high selectivity in solutions. Furthermore, facile test papers containing Phos-4-embedded nanofibrous membrane have been fabricated by the electrospinning technology. The test papers can provide visual and selective detection of phosgene with a lower limit of detection (42 ppb) and a faster response (≤10 s) in the gas phase over those in solutions. The test paper with Phos-4 is promising to be a practical detection tool of gaseous phosgene.

Sensitive and Selective Detection of Phosgene, Diphosgene, and Triphosgene by a 3,4-Diaminonaphthalimide in Solutions and the Gas Phase.

Phosgene and its substitutes, diphosgene and triphosgene, are highly toxic and widely used chemicals, so it is necessary to investigate their reactivity and develop facile, sensitive, and specific methods for detecting them. In this work, we have developed a new 1,8-naphthalimide-based fluorescent chemosensor, Phos-2, which exhibits high sensitivity (detection limits: 0.2-0.7 nm), high selectivity to phosgene and its substitutes over nitric oxide (NO), various acyl chlorides, and nerve agent mimics in solutions. Based on investigation of the reaction kinetics of Phos-2 with phosgene and its substitutes, a two-step sensing mechanism was clarified. The second-order rate constants (k2 ) of Phos-2 reveal that the relative rate constants of phosgene, diphosgene, and triphosgene are 40:4:1. Moreover, a Phos-2 test paper has been fabricated as a low-cost, sensitive (≈5 ppm from observation by the naked eye or 0.1 ppm from a measurement), and efficient method for visual detection of a low concentration of phosgene in the gas phase.

BODIPY-Based Fluorescent Sensor for the Recognization of Phosgene in Solutions and in Gas Phase.

As a highly toxic and widely used chemical, phosgene has become a serious threat to humankind and public security because of its potential use by terrorists and unexpected release during industrial accidents. For this reason, it is an urgent need to develop facile, fast, and selective detection methods of phosgene. In this Article, we have constructed a highly selective fluorescent sensor o-Pab for phosgene with a BODIPY unit as a fluorophore and o-phenylenediamine as a reactive site. The sensor o-Pab exhibits rapid response (∼15 s) in both colorimetric and turn-on fluorescence modes, high selectivity for phosgene over nerve agent mimics and various acyl chlorides and a low detection limit (2.7 nM) in solutions. In contrast to most undistinguishable sensors reported, o-Pab can react with phosgene but not with its substitutes, triphosgene and biphosgene. The excellent discrimination of o-Pab has been demonstrated to be due to the difference in highly reactive and bifunctional phosgene relative to its substitutes. Furthermore, a facile testing paper has been fabricated with poly(ethylene oxide) immobilizing o-Pab on a filter paper for real-time selective monitoring of phosgene in gaseous phase.

Selective and Real-Time Detection of Nitric Oxide by a Two-Photon Fluorescent Probe in Live Cells and Tissue Slices.

Nitric oxide (NO) is an important signaling molecule involved in many physiological and pathological processes. To understand these NO-mediated processes, it is a key to develop rapid and specific detection methods for NO. In the past 2 decades, numerous excellent fluorescent probes for NO have been designed; however, it still remains limitations such as slow response, low selectivity, and short excitation wavelength (<600 nm). In this Article, a two-photon fluorescent probe, NO-QA5, has been developed with 3-dimethylaminophenyl linking at the 6-position of 5-aminoquinoline as both the active site and prefluorophore for detection of NO. The nonfluorescent NO-QA5 can fast react with NO via a diazonium intermediate to generate two azoic regioisomers, one of which exhibits intramolecular charge transfer (ICT) emission, and two-photon absorption behavior (Î´Φ = 57 GM), giving a turn-on fluorescence rapid response. The sensing reaction is pH-insensitive in the range of 6-11 and highly selective and well sensitive (LOD = 15 nM), possible undergoing the same intermediate diazonium with the reaction under diazotization condition (NaNO2/HCl). Also, as a nitrite fluorescent probe NO-QA5 exhibits highly sensitive (LOD = 7 nM). Therefore, NO-QA5 can serve as a dual functional fluorescent probe for NO and NO2-. Furthermore, NO-QA5 as a specific imaging agent has been demonstrated by achieving both exogenous and endogenous detections of NO in living cells under both one- and two-photon excitation and high resolution in tissue slices under two-photon excitation.

The Structure-property Relationships of D-π-A BODIPY Dyes for Dye-sensitized Solar Cells.

BODIPY dyes have attracted considerable attention as potential photosensitizers in dye-sensitized solar cells (DSSCs) owing to their excellent optical properties and facile structural modification. This account focuses on recent advances in the molecular design of D-π-A BODIPY dyes for applications in DSSCs. Special attention has been paid to the structure-property relationships of D-π-A BODIPY dyes for DSSCs. The developmental process in the modified position at the BODIPY core with a donor/acceptor is described. The devices based on 2,6-modified BODIPY dyes exhibit better photovoltaic performance over other modified BODIPY dyes. Meanwhile, the research reveals the correlation of molecular structures (various donor chromophores, extended units, molecular frameworks, and long alkyl groups) with their photophysical and electrochemical properties and relates it to their performance in DSSCs. The structure-property relationships give valuable information and guidelines for designing new D-π-A BODIPY dyes for DSSCs.

Acid-Activatable Michael-Type Fluorescent Probes for Thiols and for Labeling Lysosomes in Live Cells.

A Michael addition is usually taken as a base-catalyzed reaction. Most fluorescent probes have been designed to detect thiols in slightly alkaline solutions (pH 7-9). The sensing reactions of almost all Michael-type fluorescent probes for thiols are faster in a high pH solution than in a low pH solution. In this work, we synthesized a series of 7-substituted 2-(quinolin-2-ylmethylene)malonic acids (QMAs, substituents: NEt2, OH, H, Cl, or NO2) and their ethyl esters (QMEs) as Michael-type fluorescent probes for thiols. The sensing reactions of QMAs and QMEs occur in distinct pH ranges, pH < 7 for QMAs and pH > 7 for QMEs. On the basis of experimental and theoretic studies, we have clarified the distinct pH effects on the sensing reactivity between QMAs and QMEs and demonstrated that two QMAs (NEt2, OH) are highly sensitive and selective fluorescent probes for thiols in acidic solutions (pH < 7) and promising dyes that can label lysosomes in live cells.

Ratiometric two-photon fluorescent probes for mitochondrial hydrogen sulfide in living cells.

Hydrogen sulfide (H2S) is an important signaling molecule with diverse biological roles. Various fluorescent probes for H2S with biological application have been developed. However, two-photon ratiometric imaging of mitochondrial H2S is scarce. In this paper, we report two ratiometric two-photon probes, AcHS-1 and AcHS-2, which employ 4-amino-1,8-naphthalimide as the fluorophore and 4-azidobenzyl carbamate as the H2S response site. These probes exhibit high selectivity toward H2S over biothiols and other reactive species, low detection limits of 50-85 nM, low cytotoxicity, and high stability under physiological conditions. Furthermore, through cell imaging with one-photon and two-photon microscopy, MCF-7 cells incubated with two probes show a marked change in emission color from blue to green in response to H2S. Cell images costraining with a mitochondrial dye reveal that AcHS-2 is a mitochondria-specific two-photon probe for H2S. These results show that AcHS-2 may find useful applications in biological research such as tracking mitochondrial H2S in living biological specimens.

Regioselectivity and competition of the Paternò-Büchi reaction and triplet-triplet energy transfer between triplet benzophenones and pyrimidines: control by triplet energy levels.

The photochemical reaction of a pyrimidine and a ketone occurs either as a Paternò-Büchi (PB) reaction or as energy transfer (ET) from the triplet ketone to the pyrimidine. It is rare for the two types of reactions to occur concurrently, and their competitive mechanism remains unknown. In this work, two classes of products, regioisomeric oxetane(s) (2, 3) from a PB reaction and three isomeric dimers of 5-fluoro-1,3-dimethyl uracil (FDMU) (4-6) from a photosensitized dimerization of FDMU, are obtained through the UV irradiation of FDMU with various benzophenones (BPs). The ratio of the two products (oxetanes to dimers) reveals that the two competitive reactions depend strongly on the triplet energy levels (ET ) of the BPs. The BPs with higher ET values lead to higher proportions of dimers, whereas those with lower ET values give higher proportions of oxetane(s), with the generation of just two regioisomeric oxetanes for the BP with the lowest ET of the eight BPs investigated. The ratio of the two oxetanes (2:3) decreases with the BP ET value. The competitive mechanism for the two types of photochemical reactions is demonstrated through quenching experiments and investigation of temperature effects. Kinetic analysis shows that the rate constants of the two [2+2] photocycloadditions are comparable. Furthermore, in combination with the results of previous studies, we have gained insight into the dependence of the photochemical type and the regioselectivity in the PB reaction on the triplet energy gaps (ΔE) between the pyrimidines and ketones. For ketones with higher ET values than the pyrimidines, the photochemical reaction is a photosensitized dimerization of the pyrimidine. In the opposite case, a PB reaction occurs, and the lower the ET of the ketones, the lower the ratio of oxetanes (2:3). When the ET of values of the ketones are close to those of the pyrimidines, the two reactions occur concurrently, and the higher the ET of the ketones, the higher the proportion of the dimers. The ratio of oxetanes (2:3) decreases with the ET value of the BPs.

[The design and baseline characteristics of a phase III study to evaluate the efficacy and safety of alogliptin versus placebo in type 2 diabetes mellitus in Mainland China].

OBJECTIVE: To assess the design and the Mainland China subgroup baseline characteristics of the study to evaluate the efficacy and safety of alogliptin versus placebo in subjects with type 2 diabetes (T2DM) as monotherapy, add-on to metformin or add-on to pioglitazone. METHODS: This was a multi-center, randomized, double-blind, placebo-controlled, 16-week study comparing alogliptin (ALO, 25 mg, 1/d) versus placebo (PLA) as monotherapy (A), add-on to metformin (B) or add-on to pioglitazone ± metformin (C). The T2DM subjects with glycosylated hemoglobin A1c(HbA1c) between 7% and 10% and aged between 18 years and 75 years were enrolled and randomized to the alogliptin group and the placebo group in 1: 1 ratio with 16 weeks treatment. All patients were followed up every 4 weeks. The safety endpoints consisted of the incidence of hypoglycemia and other adverse events. RESULTS: A total of 491 patients were enrolled in the Mainland China subgroup of the study (181 in group A, 186 in group B and 124 in group C). In each treatment group, the baseline characteristics including age, gender, body mass index, diabetes duration, HbA1c, fasting plasma glucose, body weight, daily dosage of metformin and daily dosage of pioglitazone were all well balanced. CONCLUSION: The demographic data, medical history, glycemic profile and treatment regimen at baseline in Mainland China subgroup are well balanced. The result of this study will provide the clinical evidence for the use of alogliptin in Chinese T2DM patients.

(E)-2-Meth-oxy-9-(2-meth-oxy-9H-xanthen-9-yl-idene)-9H-xanthene.

The title compound, C28H20O4, was synthesized by a bimolecular Zn-HCl reduction in glacial acetic acid using the meth-oxy-substituted xanthone as a starting material. The crystal structure shows that the 2,2'-meth-oxy-bixanthenyl-idene unit is an E-type conformation anti-folded conformer. The mol-ecule lies on an inversion center. The meth-oxy group is almost coplanar with the attached benzene ring, with a C-O-C-C torsion angle of 179.38 (14)°.

A fluorescent probe generating in situ the reactive species for rapid and selective detection of mustard gas.

Sulfur mustard (SM) is an important chemical warfare agent (CWA) and has been used frequently in various conflicts. It is important to develop a facile, rapid, sensitive and selective detection method for SM. In this work, we constructed a novel fluorescent probe PCS capable of generating active sensing species for rapid and selective detection of SM and its simulant CEES (2-chloroethyl ethyl sulfide). PCS exhibits excellent chemical and photostability and can generate reactive species in situ for rapid (within 90 s, at 60 °C) and selective detection of SM and CEES in solution with high sensitivity (∼nM level). Moreover, PCS could enable the detection of mustards in situ. A test strip with PCS and KOH was prepared and realized the sensitive and selective detection of CEES in the gas phase. In addition, the PCS probe can realize facile and rapid detection of CEES-contaminated surfaces by spraying its sensing system (ethanol solution containing PCS and KOH). The sensing mechanism was well demonstrated through the separation and characterization of the sensing product.

A BODIPY-based fluorescent probe for simultaneous detection of H2O2 and viscosity during the pyroptosis process.

A dual functional BODIPY fluorescent probe was developed for simultaneous detection of H2O2 and viscosity, by collecting fluorescence from 800-1100 nm and 550-750 nm, respectively. Bioimaging based on the probe shows that H2O2 accumulates and cytoplasmic viscosity increases during the palmitic acid (PA)-induced pyroptosis process.