Silver selective electrodes using ionophores functionalized with thioether‒amide‒amine

New poly(vinylchloride) (PVC) based liquid membrane sensors are reported containing neutral macrocyclic carrier as potential ionophores for sensing silver ions. Three macrocycles (L₁, L₂ and L₃) possessing two thioether, two amide and one secondary amine unit have been used in new PVC membrane-based sensor. At wide pH range of 4.5 to 8.0, these sensors exhibit linear responses in the concentration range of 1 × 10^–4 to 0.1 M and detection limit 6 × 10^–5 M for L₁ and 1 × 10^–4 M for L₂ and L₃ respectively with pseudo-Nernstian slopes between 43?46 mV/decade for all the three sensors. These sensors have short response time (<15 s) and long life time as these sensors do not show any considerable divergence in their performance over a period of four months. These sensors exhibit good selectivity for Ag⁺ over wide variety of interfering ions like alkali, alkaline earth, transition and some heavy metal ions. These proposed sensors could be used successfully as indicator electrodes in the potentiometric determination of Ag⁺ ions and also to determine anions like Cl^–, Br^–, I^–, S2^–, SCN^– and CN^–. Potentiometric titrations for halide ions in a mixture using these sensors and new titration method for the determination of detection limits are reported.     

Complexation of neurotransmitters ‒ dopamine,serotonin and melatonin ‒ with a DTPA-based cyclophane of high rigidity: 1H NMR shift and line-broadening

The ¹H NMR signals of the titled neurotransmitters undergo up-field shift accompanied by line-broadening in NMR titration with the DTPA-based cyclophane at pD 7.3; the cyclophane consists of a 4,4′-bis(1,1′-biphenyl-4,4′-dihydroxy)dianiline unit cyclised by a DTPA (diethylenetriaminepentaacetate) group through two amide linkages. Changes in chemical shifts of dopamine indicate the formation of a 1:1 complex with the formation constant K₁ 400 M^?1; the complex of serotonin is likely to form a 2:1 host?guest complex with β₂ ≈ 10⁵ M^?2; melatonin does not form a complex with definite stoichiometry. The primary binding forces in the dopamine and serotonin complexes are electrostatic interaction between cationic neurotransmitter and anionic cyclophane molecules, and the resulting ionic pairs are stabilised by encapsulation. The electrostatic interaction is weakened by electrolytes; in 0.1 M Trizma buffer, dopamine does not yield a definite complex, and serotonin forms a 1:1 complex with K₁ 80 M^?1. Extreme line-broadening of neurotransmitter signals suggests that the molecular motion of the guest molecule is slowed in the complex by interactions with the receptor molecule whose internal molecular motion is quenched partially. The high rigidity of the cyclophane enhances intermolecular interaction in the hydrophobic regions to prolong the lifetime of the complex.     

Isa‒NHC‒catalyzed intermolecular Stetter reaction of aromatic aldehydes with maleimides: An efficient access to 3‒aroylsuccinimides

An intermolecular Stetter reaction of aromatic aldehydes with maleimides has been developed using thiazolylidene salt derived Isa?NHC as an efficient organocatalyst. The synthesized Stetter products “3?aroylsuccinimides” are important building blocks for the synthesis of natural products and bioactive compounds. The reaction conditions are mild, and various substituents on aromatic aldehyde and maleimide nitrogen were tolerated.     

Synthesis of Organophosphorus Compounds with ‒P˭P≡ and ‒P˭S˭ Units

Abstract

The lithium phosphide tetrahydrofurane complexes 1 react with phosphinic acid chlorides (2) to yield diphosphenes (4), possessing a tri- and a quinquevalent phosphorus atom; the diphosphane oxides 3 are regarded to be intermediate steps of the transformation.     

Applicability of anthracite filtration‒micro electrolysis‒sand filtration for the treatment of surface waters containing high turbidity

The effect of combined filtration efficiency on the performance of anthracite filtration?micro electrolysis?sand filtration (AMS) was investigated. Impact of different operating parameters, such as iron?carbon ratio of micro electrolytic units, filtration velocity of AMS, were studied. It was found that when iron?carbon ratio was 6: 4, the AMS’s average turbidity removal rate was 96.75% at the filtration velocity of 3 m h^?1. The results showed that when the filtration rate was 3?9 m h^?1 and iron?carbon ratio was 6: 4, the turbidity removal efficiency was over 94%, and the turbidity of the effluent was less than 1 NTU in effective filtration cycle. The effective filtration cycle can last for more than 5 h or longer. Meanwhile, the removal rate of UV₂₅₄ was above 33%, and the concentration of iron ions in the effluent is less than 0.15 mg L^?1. Turbidity and iron indicators have reached the national drinking water standards. It was also found the mechanism of iron?carbon micro electrolytic enhanced filtration by infrared spectroscopy and scanning electron microscopy. And It was also speculated the reasons for the reaction passivation.     

Fluorinated Porous Poly(spirobifluorene) Via Direct C‒H Arylation: Characterization,Porosity, and Gas Uptake

Considering intrinsic properties of conjugated polyfluorenes and special functions of porous polymers, synthesis of fluorinated porous poly(spirobifluorene) via direct C?H arylation polycondensation is explored. Owing to the contorted structure and cross-linking nature, the obtained polymer FPSBF shows permanent porosities with Brunauer–Emmett–Teller specific surface area up to 700 m² g^?1 and exhibits a narrow pore size distribution with the dominant pore size at about 0.63 nm, which is more suitable for adsorption of small gas molecules. Based on the measured gas physisorption isotherms with pressure up to 1.13 bar, the obtained polymer shows good uptaking capacities for hydrogen (1.30 wt% at 1.0 bar and 77 K) and methane (4.80 wt% 1.0 bar and 273 K). Moreover, FPSBF has significant adsorption selectivity for CH₄ against N₂ and the estimated ideal adsorption selectivity ratio is up to 30/1 at 1.0 bar and 273 K, which makes the material possess potential application in gas separation.     

Extraction of Metals in a Water‒Potassium Bis(Alkylpolyoxyethylene)Phosphate‒Ammonium Sulfate System with Various Photometric Reagents

The interfacial distribution of a number of organic photometric reagents in a water?potassium bis(alkylpolyoxyethylene)phosphate (oxyphos B)?ammonium sulphate splitting system is studied. It is found that alizarin complexone, 1-(2-pyridylazo)-2-naphthol-2 (PAN), bromothymol blue, rhodamine 6G, pyrogallol red, morin, fuchsine, malachite green, bromothymol blue, pyrocatechol violet (PCV), chromazurol S, and aluminon are extracted with partition coefficients higher than 100. A possibility of the extraction?photometric determination of gallium with PCV and cobalt with PAN is shown. The proposed procedures do not require the use of fire-hazardous, volatile, and toxic organic solvents.     

CeO2负载的PdO与Ce1‒x Pd x O2‒δ 物种的甲烷催化燃烧性能

通过调控Pd前驱物在CeO₂上的沉积方式, 分别制备了以PdO和离子态的Ce_1?x Pd _x O_2?δ 物种为主的 Pd/CeO₂催化剂, 并采用X射线光电子能谱(XPS)和拉曼(Raman)光谱确证了这两种Pd物种的存在. 氧气程序升温脱附(O₂-TPD)和氢气程序升温还原(H₂-TPR)的表征结果显示, 相比于与载体相互作用较弱的PdO物种, 与CeO₂相互作用较强的Ce_1?x Pd _x O_2?δ 物种具有更加稳定的Pd—O键. 催化剂的甲烷燃烧反应起燃活性测试结果显示, 以PdO物种为主的催化剂表现出了良好的低温催化性能, 在原料气配比为1%CH₄/4%O₂-Ar, 空速为60000 mL·{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^?1的条件下, T₁₀和T₉₀分别为275和367 ℃, 而两种以Ce_1?x Pd _x O_2?δ 物种为主的催化剂的T₁₀均超过420 ℃. 催化剂的甲烷程序升温还原(CH₄-TPR)表征结果表明, 在升温过程中只有当PdO或Ce_1?x Pd _x O_2?δ 物种被CH₄还原后, 催化活性才开始上升. 由于PdO物种的Pd—O键强度较弱, 有利于Pd物种上的晶格氧在较低温度下参与CH₄的氧化过程. 而Ce_1?x Pd _x O_2?δ 物种的Pd—O键较稳定, 且在反应条件下离子态Pd²⁺与反应体系中氧物种的作用较强, 进而抑制了其与CH₄的反应, 因此反应的起燃温度较高. 以γ-Al₂O₃为载体采用相同的方法制备了Pd/γ-Al₂O₃催化剂, 相关的表征结果进一步证实, 与载体相互作用较弱的PdO物种更容易被CH₄还原, 进而具有较高的催化活性. 据此可以认为Pd/CeO₂上氧化态的Pd物种被CH₄的还原性能是决定其甲烷催化燃烧反应活性的重要因素之一.     

A prototype of benzobis(imidazolium)-embedded conjugated polyelectrolyte: Synthesis by direct C‒H arylation and fluorescent responses to anions

We report the convenient synthesis of a benzobis(imidazolium)-embedded conjugated polyelectrolyte pBBI by a Cu-catalyzed direct C?H arylation of a cationic benzobis(imidazolium) monomer with a diiodide comonomer. pBBI shows weak fluorescence in solution due to rotation of the repeat units in the conjugated backbone, and enhanced fluorescence when electrostatically interacting with a variety of anions to form aggregates. Specially, pBBI responds to the bisulfite anion with intensified unique deep-blue fluorescence easily discriminated by naked eye.     

Magnetic properties of electrodeposited Ni‒P alloys with varying phosphorus content

The effect thermal treatment has on the magnetic properties (magnetization, saturation magnetization, and coercivity) of Ni?P alloys prepared via electrodeposition is studied. The process of amorphous Ni?P alloys devitrification is investigated by differential scanning calorimetry. The effects of chemical composition and thermal treatment on magnetic properties of the alloys are revealed.     

席夫碱共价有机框架的合成及对I ‒ 的识别

设计合成了一种新型共价有机框架类荧光探针TpPa-COOH COF, 该探针在THF/H₂O(体积比1∶1)混合溶液中能够高选择性识别I^?. 向体系中加入I^?后, 溶液由浅红色变为黄色, 317 nm处荧光强度明显降低. 该探针具有良好的选择性, 抗干扰能力强, 检出限为0.028 μmol/L, pH适用范围广(1~13), 具有良好的应用前景.     

QuEChERS method combined with GC‒MS for pesticide residues determination in water

A miniaturized, QuEChERS based, liquid–liquid extraction method followed by gas chromatography–mass spectrometry was developed and validated for pesticide residues determination in water. Malathion, chlorpyrifos, profenofos, chlorfenapyr, pyriproxyfen, λ-cyhalothrin, coumaphos and α-cypermethrin were selected for this study. The accuracy, precision, specificity, linearity, limit of detection and limit of quantification were evaluated. The recovery ranged from 85.3 to 107% with RSD ranging from 1.8 to 15.4%. The linearity showed reliable range (0.995–0.999). The limit of detection ranged from 0.3 to 4 μg/L. Matrix effect was evaluated. The obtained results meet the European Commission standard legislations, implying that our method can be considered accurate and reproducible. The validated method was used to analyze river and well water samples. No residues of the investigated pesticides were detected in all collected water samples.     

One-Pot Synthesis of 3,5-Disubstituted 1,2,4-Oxadiazoles Using Catalytic System NaOH‒DMSO

Russian Journal of Organic Chemistry - One-pot convenient process was developed for the production of 3,5-disubstituted 1,2,4-oxadiazoles by reaction of amidoximes with anhydrides or acyl chlorides...     

The Reaction of Ketenylidenetriphenylphosphorane (Ph3P˭C˭C˭O) with Acidic H‒E (E˭O,N) Bonds

Abstract

The reactivity of ketenylidenetriphenylphosphorane (1) with the protic reagents 2,4,6-trimethylphenol (7), 2,6-di-tert-butyl-4-methylphenol (8), and diphenylamine (9) has been explored. Three novel carbonyl-stabilized ylides have been synthesized and characterized. Crystal structures were obtained for Ph₃PCHC(O)O(C₆H₂Me₃) (11), Ph₃PCHC(O)O(C₆H₂t-Bu₂Me) (12), and Ph₃PCHC(O)NPh₂ (13), respectively. These products were then methylated in an attempt to develop a new route to low-valent carbon compounds. Crystals of [Ph₃PCH(CH₃)C(O)O(C₆H₂Me₃)]I (14) were isolated and characterized but this route did not prove to be synthetically useful, at least toward the goal of preparing low-valent carbon-centered materials. Finally, 1 was also reacted with the bulky tin reagent, bis[bis(trimethylsilyl)amido]tin(II), in the presence of 2,4,6-trimethylphenol. A complex mixture of products was obtained, from which crystals of an unusual chelated tin compound (15) were isolated and characterized using X-ray crystallography.     

Alignment of liquid crystals using Langmuir‒Blodgett films of unsymmetrical bent-core liquid crystals

ABSTRACT

The properties of the thin films of liquid crystal (LC) molecules can be governed easily by external fields. The anisotropic structure of the LC molecules has a large impact on the electrical and optical properties of the film. The Langmuir monolayer (LM) of LC molecules at the air–water interface is known to exhibit a variety of surface phases which can be transferred onto a solid substrate using the Langmuir?Blodgett (LB) technique. Here, we have studied the LM and LB films of asymmetrically substituted bent-core LC molecules. The morphology of LB film of the molecules is found to be a controlling parameter for aligning bulk LC in the nematic phase. It was found that the LB films of the bent-core molecules possessing defects favour the planar orientation of nematic LC, whereas the LB films with fewer defects show homeotropic alignment. The defect in LB films may introduce splay or bend distortions in the nematic near the alignment layer which can govern the planar alignment of the bulk LC. The uniform layer of LB film facilitates the molecules of nematic to anchor vertically due to a strong van der Waals interaction between the aliphatic chains leading to a homeotropic alignment.     

Constants of acid‒base equilibria in an aqueous amikacin aminoglycoside solution at 298 K

The acid dissociation constants of form pK₁ = 7.34 ± 0.01, pK₂ = 7.84 ± 0.01, pK₃ = 8.77 ± 0.01, pK₄ = 9.49 ± 0.01, and pK₅ = 10.70 ± 0.02 of cationic amikacin are determined by pH-metric titration at 25°C against the background of 0.1 mol/L KNO₃. K₁, K₂, K₃, and K₄ correspond to the dissociation of protons coordinated to amino groups, while K₅ characterizes the dissociation of the hydroxyl hydrogen atom, testifying to the amphoteric character of amikacin molecules. Applying density functional theory (DFT) with the B3LYP hybrid functional and the 6-311G**++ basis set, the partial charges on the atoms of an amikacin molecule are calculated. It is concluded that the dissociation of H(55)hydrogen atom occurs with a greatest partial charge of +0.53631.     

A new β-diketonate Dy(III) single‒ion magnet featuring multiple magnetic relaxation processes

Abstract

A β-diketonate mononuclear dysprosium compound, [Dy(TFNB)₃(bpy)] (1) (TFNB = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, bpy = 2,2′-bipyridine), has been prepared and structurally and magnetically characterized. X-ray crystallographic analysis reveals that 1 contains two crystallographically equivalent Dy(III) ions of which the eight-coordinate geometries uniformly behave as distorted square antiprismatic configurations (D_4d). Magnetic investigations demonstrate that 1 displays dual relaxation processes of SMMs behavior with the effective barrier (ΔE/k_B) of 23.44 K under 1200 Oe DC field, corresponding to the coexistence of two metal centers in the structure of the compound. The comparative studies of some Dy(III)-based SIMs with TFNB ligand have been conducted as well. Ab initio studies demonstrate that the Kramers doublet ground state is predominantly axial with the g_z tensors of two Dy(III) fragments matching the Ising-limit factor (20) anticipated for the pure M_J = ±15/2 state.