Azomethine-H as a Highly Selective Fluorescent Probe for Fe3+ Detection in 100％ Aqueous Solution and Its Application in Living Cell Imaging

A simple assay for the detection of Fe³⁺ in water by means of fluorescence spectroscopy was developed based on a commercially available reagent, Azomethine-H(A-H), allowing sensing trace levels of Fe³⁺ with high selectivity over other cations. A significant fluorescence quenching of A-H at 424 nm was found after its binding with Fe³⁺ in 100% aqueous solution at pH=7.0, while other physiologically relevant metal ions posed little interference. The fluorescence responses can be well described by the modified Stern-Volmer equation. A good linear relationship(R²=0.9904) was observed up to 1.6×10^-5 mol/L Fe³⁺ ions. The detection limit, calculated via the 3σ IUPAC(international union of pure and applied chemistry) criteria, was 1.95×10^-7 mol/L. Moreover, the colorimetric and fluorescent response of A-H to Fe³⁺ can be conveniently detected by the naked eye, providing a facile method for visual detection of Fe³⁺. The proposed method was used to determine Fe³⁺ in water samples. Moreover, inverted fluorescence microscopy imaging using human umbilical vein endothelial cells shows that A-H can be used as an effective fluorescent probe for detecting Fe³⁺ in living cells.     

A Selective and Sensitive Fluorescence Probe for Se(Ⅳ) Based on Fluorescence Quenching of Gatifloxacin

A novel high selective and sensitive fluorescence probe termed gatifloxacin was discovered based on fluorescence "on-off" phenomenon in the presence of Se(Ⅳ). In the Tris-HCl/acetonitrile(3:7, volume ratio, Tris-HCl 0.05 mol/L, pH=7.3) sys-tem, the fluorescence intensity of gatifloxacin was linearly decreased with the concentration increase of Se(Ⅳ) in a range of 1.0×10^-5-5.0×10^-5 mol/L with a correlation coefficient of 0.9979(R²=0.9958) and in a range of 5.0×10^-5-1.0×10^-4 mol/L with a correlation coefficient of 0.9973(R²=0.9946). The detection limit of Se(Ⅳ) was 1.70×10^-6 mol/L.     

Development of an Organic Dye-Conjugated β-Diketonate-Europium Complex Luminescence Probe for Discrimination and Detection of Intracellular Biothiols

Small molecular biothiols, cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play important roles in organisms, and their concentration levels are indicative of some human diseases. Herein we report an organic dye-conjugated β-diketonate-Eu³⁺ complex, [Eu(NBD-keto)₃(DPBT)] (NBD-keto: 7-nitro-2,1,3-benzoxadiazole (NBD)-conjugated to 1,1,1,2,2-pentafluoro-5-phenyl-3,5-pentanedionate through a “O” ether bond; DPBT: 2-(N,N-diethylanilin-4-yl)-4,6-bis(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine), which acts as a unique luminescent probe for detecting and discriminating biothiols. [Eu(NBD-keto)₃(DPBT)] itself is not luminescent due to intramolecular interactions between NBD and β-diketonate-Eu³⁺ moieties. Upon reaction with biothiols, the β-diketonate-Eu³⁺ complex [Eu(keto)₃(DPBT)] is generated, which emits long-lived red emission at 610 nm. Meanwhile, three biothiol-substituted NBD derivatives that exhibit different luminescence behaviors, green emissive (short-lived) NBD-NR (R=Cys or Hcy) at 540 nm and non-luminescent NBD-SR (R=GSH), are also generated. These luminescence response behaviors allow time-gated and steady-state luminescence modes to be combined for detecting total biothiols and discriminating GSH and Cys/Hcy. Using this probe, the quantitative detection and discrimination of GSH and Cys/Hcy in lysis solutions of HeLa cells were realized, which revealed the potential of the probe for biomedical applications.     

Silica Supported Perchloric Acid:A Convenient and Environmentally Friendly Catalyst for the One-pot Multicomponent Synthesis of β-Acetamido Ketones

A modified Dakin‐West one‐pot, four‐component condensation of an aryl aldehyde, aryl ketone, acetyl chloride and acetonitrile in the presence of silica supported perchloric acid as an active, inexpensive, recoverable and recyclable catalyst is reported for the synthesis of β‐acetamido ketones under mechanical stirring and ultrasonic irradiation conditions. This system has advantages of short reaction times, good to excellent yields and the ability to carry out the large scale reactions. The use of ultrasound increases the rate of reactions compared with reactions at reflux conditions.     

Is There an Entrance Complex for the F+NH3 Reaction?

Challenges associated with the theoretical and experimental kinetics of the F+NH₃→HF+NH₂ reaction suggest the need for a more‐precise potential surface. We have investigated the reactants and the products of the reaction, as well as the transition state and two complexes, with rather rigorous ab initio methods. The F????NH₃ complex existing in the entrance valley is predicted to lie 13.7 kcal mol^?1 below the reactants. A small classical barrier of 2.0 kcal mol^?1 separates this entrance well from products HF+NH₂. These results explain the observation by Persky of unprecedented inverse temperature dependence for the F+NH₃ rate constants. The strong hydrogen‐bonded complex FH????NH₂ exists in the exit valley, and with a binding energy of 9.9 kcal mol^?1 relative to separated products. The vibrational frequencies of all stationary points are predicted with the CCSD(T)/aug‐cc‐pVQZ method.     

Preparation and Characterization of A New Dinuclear Ruthenium Complex with BDPX Ligand and Its Catalytic Hydrogenation Reactions for Cinnamaldehyde

Introduction Recently, dinuclear Ru complexes containing chelating bidentate phosphines (either chiral or non-chiral) have attracted more and more attention owing to their effective ability for catalytic hydrogenation of olefins and carbonyl groups under mild conditions. A great number of dinuclear Ru complexes with bidentate phosphines have been obtained.1-10 In 1985 Ikariya et al.1 prepared a chiral binuclear ruthenium complex [Ru2Cl4(BINAP)2]NEt3 by the reaction of (S)-BINAP with [R…     

Molecular Recognition of Immobilized Supramolecular Complex of Ironporphyrin and β-CD Polymer as an Analogue for Peroxidase

The immobilized supramolecular inclusion complex of FeTPPS4 and -CD polymer was applied as a mimesis of peroxidase, and its molecular recognition for twenty substrates was studied. As the space structure;CD interior cavities, high selectivity was obtained by immobilized mimetic enzyme. p-Chlorophenic acid was identified as an optimal substrate in the system tested.     

A green-emitting α-substituted β-diketonate Tb3+ phosphor for ultraviolet LED-based solid-state lighting

The α-substituted β-diketonate [Ln(3Cl-acac)₃(H₂O)₂] [Ln = Tb, Gd] complexes (with 3Cl-acac^– being 3-chloro-2,4-pentanedionate) were characterized by elemental analysis, infrared, ultraviolet (UV)-visible and photoluminescence spectroscopies. For comparison purposes regarding photoluminescence, the well-known [Tb(acac)₃(H₂O)₂] complex was also synthesized. By considering the phosphorescence spectra of [Gd(3Cl-acac)₃(H₂O)₂], the effect of chloride replacement of hydrogen on the triplet state energy of the 3Cl-acac ligand was revealed. To support the interpretation and rationalization of the experimental results, Time-dependent DFT calculations were performed on Tb(3Cl-acac)₃(H₂O)₂. Additionally, the possibility of Tb(3Cl-acac)₃(H₂O)₂ to be used as potential green-emitting phosphor material for solid-sate light emitting diodes was evaluated. A prototype was successfully fabricated coating a near-UV LED (370 nm) with the Tb(3Cl-acac)₃(H₂O)₂ complex.     

A Cobalt(III)−Hydroxo Complex Bearing a Pentadentate Amidate Ligand as an Electrocatalyst for Water Oxidation

A Co(III)−hydroxo complex, [Co^III(dpaq)OH]ClO₄ ( 1-OH ) bearing a pentadentate ligand, H-dpaq, (H-dpaq=(2-[bis(pyridin-2-ylmethyl)]amino-N-quinolin-8-yl-acetamidate]) catalyses water oxidation in mildly alkaline medium (pH 8.0) at a potential of 1.4 V_NHE with an average Turn-Over-Frequency (TOF_max) of 2.8×10⁴ s⁻¹ and faradaic efficiency of 88 %. Post-electrolysis characterization of the electrode rules out the formation of any heterogeneous electroactive species. Electrochemical results and theoretical calculations confirm the occurrence of both metal and ligand centered PCET processes during anodic scanning. The resulting formally Co(V)−oxo/oxyl intermediate undergoes water nucleophilic attack to install the O−O bond. The role of axial ligand in water oxidation by Co(III)−dpaq system has been examined by comparing the reactivity of the Co-hydroxide complex ( 1-OH ) with that of its chloride-ligated counterpart, [Co^III(dpaq)Cl]Cl ( 1-Cl ). The results confirm the ability of the Co-dpaq complexes to bind water/or water derived ligands over chloride or non-aqueous solvents. The interplay of ligand redox non-innocence and σ-donating ability of the N5-carboxamido ligand helps to store oxidizing equivalents and triggers O−O bond formation.     

A Novel Electrogenerated Chemiluminescence Reaction Scheme Using Core-Shell LuminoI-Based SiO2 Nanoparticles as a Regulator and Its Analytical Application

A novel core-shell luminol-based SiO2 nanoparticle While these nanoparticles were used as electrogenerated was synthesized by two step micro-emulsion method. chemiluminescence （ECL） reagent, the electrochemical （EC） reaction as well as the subsequent chemiluminescence （CL） reaction not only could be separated spatially, but also presented high efficiency for analytical purpose. In this case, the core-shell luminol-based SiO2 nanoparticles offered more potential to avoid the contradiction between the EC and the CL reaction conditions. A new ECL method based on the nanoparticle was developed, and isoniazid was selected as a model analyte to illustrate the characteristics of this new ECL method. Under the selected conditions, the proposed ECL response to isoniazid concentration was linear in the range of 1.0 ×10^-10 to 1.0 × 10^-6 g/mL with 2 × 10^-11g/mL detection limit.     

Interaction between Cationic Surfactants and Bromopyrogallol Red as well as Its Application for the Sensitive and Selective Determination of Mo in Mo/W Binary Mixtures

IntroductionltiswellknownthatWofteninterfereswiththespectrophotometricdeterminationofMo'.Althoughthisproblemwascircumventedbymeansofvariouschemometricmethodsorbydiversespectrophotornetrictechniquessuchasmu1ti-wave1ength=.extraction',derivative'.etc..yetthesetechniqueswererathercompllcatedorandtime-consumingandthefeaturesofsimpllcityandrapidityofspectrophotometrycou1dhardlybehighllghted.lnaddition,someoftheabovetechniqueswereoftenaccompaniedb},a1ossofsensitivity'.Basedonthestudyontheinteraction…     

A New Fluorescence Method for the Measurement of Intracellular Free Rare Earth Ions： Fura－2 as an Indicator

ＡＮｅｗＦｌｕｏｒｅｓｃｅｎｃｅＭｅｔｈｏｄｆｏｒｔｈｅＭｅａｓｕｒｅｍｅｎｔｏｆＩｎｔｒａｃｅｌｌｕｌａｒＦｒｅｅＲａｒｅＥａｒｔｈＩｏｎｓ,Ｆｕｒａ－２ａｓａｎＩｎｄｉｃａｔｏｒＡＮｅｗＦｌｕｏｒｅｓｃｅｎｃｅＭｅｔｈｏｄｆｏｒｔｈｅＭｅａｓｕｒ?..     

Acenaphtho[1,2-d][1,2,3]triazole and Its Kuratowski Complex: A π-Extended Tecton for Supramolecular and Coordinative Self-Assembly

π-Extended acenaphtho[1,2-d][1,2,3]triazoles, the unsubstituted Anta-H and its di-tert-butyl derivative Dibanta-H, as well as 5,6,7,8-tetrahydro-1H-naphtho[2,3-d][1,2,3]triazole Cybta-H were obtained in concise syntheses. In the solid state, Dibanta-H forms an unprecedented hydrogen-bonded cyclic tetrad, stabilized by dispersion interactions of the bulky tBu substituents, whereas a cyclic triad was found in the crystal structure of Anta-H. These cyclic assemblies form infinite slipped stacks in the crystals. Evidence for analogous hydrogen-bonded self-assembly in solution was provided by low-temperature NMR spectroscopy and computational analyses. Kuratowski-type pentanuclear complexes [Zn₅Cl₄(Dibanta)₆] and [Zn₅Cl₄(Cybta)₆] were prepared from the respective triazoles. In the Dibanta complexes, the π-aromatic surfaces of the ligands extend from the edges of the tetrahedral Zn₅ core, yielding an enlarged structure with significant internal molecular free volume and red-shifted fluorescence.     

Solid-State Synthesis of SnO2–Zn2SnO4 Nanocomposite and Its Application for Electrochemical Detection of Cabergoline as Dopamine Receptor Antagonists

Russian Journal of Electrochemistry - In the present work, the synthesis of SnO2–Zn2SnO4 nanocomposite was fulfilled according to solid-state technique followed by calcination. The...     

A “turn-on” and label-free fluorescent assay for the rapid detection of exonuclease III activity based on Tb3+-induced G-quadruplex conjugates

A “turn-on” and label-free fluorescent assay for the specific, rapid, and sensitive detection of 3′?→?5′ exonuclease III activity is reported in this study. The assay is based on the Tb³⁺-promoted G-quadruplex, which lead to the enhancement of Tb³⁺ fluorescence due to the energy transfer from guanines. The proposed assay is highly simple, rapid, and cost-effective, and does not require sophisticated experimental techniques such as gel-based equipment or radioactive labels. It can be used for the rapid detection of exonuclease III activity with a detection limit of 0.8 U and a RSD (n?=?6) <5 %. Notably, no dye was covalently conjugated to the DNA strands, which offers the advantages of low-cost and being interference-free.     

Bromoperoxidases and functional enzyme mimics as catalysts for oxidative bromination—A sustainable synthetic approach

The discovery of enzymes that utilize hydrogen peroxide to oxidize bromide under physiological conditions provided a strong stimulus to the field of oxidative bromination. A synthetically useful enzyme, to catalyze the oxidation of bromide, for bromofunctionalization of donor-substituted arenes in solutions of hydrogen peroxide and sodium bromide, is a vanadate(V)-dependent bromoperoxidase from the brown alga Ascophyllum nodosum. This enzyme operates in homogeneous solutions of buffered aqueous tert-butanol (pH 6.2), or, to simplify repetitive use, in a two-phase system after immobilization onto magnetic beads. Synthesis of cyclic bromohydrin ethers (tetrahydrofurans and tetrahydropyrans) and vicinal dibromides from unsaturated hydrocarbons, on the other hand, occurs more effectively in polar aprotic solvents. Under such conditions the more lipophilic tert-butyl hydroperoxide serves as oxidant, which is activated by oxovanadium(V) complexes (functional bromoperoxidase mimics). Protons and bromide ions, which are consumed for in situ generation of bromine, are supplied in organic solution by fragmentation of 3-bromopropionic acids. The structure-reactivity data obtained from oxidations catalyzed by bromoperoxidases and functional enzyme mimics pose a valuable guideline for predicting selectivity in biomimetic synthesis of organobromines from terpenes, acetogenins, and pyrrole alkaloids.     

Ph3P+CF2CO2− as an F− and :CF2 source for trifluoromethylthiolation of alkyl halides

Trifluoromethylthiolation of alkyl halides using Ph₃P⁺CF₂CO₂^- as a fluoride and difluorocarbene source is described. Even though the process involved a cleavage of a C-F bond and the formation of R-S, S C and C-F bonds, the reactions occurred rapidly and were completed within 10 min.     

A dual chemosensor for Cu2+ and Fe3+ based on π-extend tetrathiafulvalene derivative

A new dual chemosensor (TTF-PBA) for Fe³⁺ and Cu²⁺ in different signal pathways was designed and synthesized. The absorption spectrum, fluorescence spectrum and cyclic voltammograms changed in the presence of Cu²⁺ and Fe³⁺. The optical color changed within 5 s from yellow to orange upon the addition of Cu²⁺, and it changed to dark yellow when Fe³⁺ existed. The cyclic voltammogram of Cu²⁺/TTF-PBA changed from E_ox = 0.50 V, E_red = 0.32 V to E_ox = 0.64 V, E_red = 0.80 V (vs Ag/AgCl) upon the addition of 2.0 equiv. Cu²⁺. As for Fe³⁺/TTF-PBA, its oxidation wave disappeared, and its reduction wave appeared at E_red = ?0.59 V (vs Ag/AgCl) upon the addition of 4.0 equv. Fe³⁺. The sensor displayed high selectivity for Cu²⁺ and Fe³⁺ over other ions including Pb²⁺, Zn²⁺, Ni²⁺, Ag⁺, Cr³⁺, Mn²⁺, Al³⁺, Co²⁺, Pd²⁺, Hg²⁺, Fe^2+, Cd²⁺, Ce³⁺, Bi³⁺ and Au³⁺, the detection limits for Cu²⁺ and Fe³⁺ ion reached as low as 5.33 × 10^?7 mol/L and 5.34 × 10^?7 mol/L, respectively. Furthermore, when Fe³⁺ existed, Cu²⁺ can be detected sequentially by the sensor through the absorption spectrum and the color change observed by naked-eyes.