A copper(II)-catalyzed,sequential Michael–aldol reaction for the preparation of 1,2-dihydroquinolines

A copper(II)-catalyzed, sequential Michael addition-aldol condensation reaction of N-carboxybenzyl-protected aminobenzaldehyde with various α,β-unsaturated N-acyl pyrroles is described. Substrate scope was found to include both aryl and aliphatic N-acyl pyrroles as the Michael acceptors, and isolated product yields as high as 93% were observed. The use of acetonitrile as the reaction solvent proved to be crucial for catalysis, both to function as a labile ligand for copper, as well as an agent to minimize hydrolytic catalyst poisoning.     

LC–MS methods combination for identification and quantification of trans-sinapoylquinic acid regioisomers in green coffee

The present study aims to both identify and quantify trans-sinapoylquinic acid (SiQA) regioisomers in green coffee by combined UHPLC-ESI-QqTOF-MS/MS and UHPLC-ESI-QqQ-MS/MS methods. Among the various mono-acyl chlorogenic acids found in green coffee, SiQA regioisomers are the least studied despite having been indicated as unique phytochemical markers of Coffea canephora (known as Robusta). The lack of commercially available authentic standards has been bypassed by resorting to the advantages offered by high-resolution LC–MS as far as the identification is concerned. SiQA regioisomers have been identified in several samples of Robusta and Coffea arabica (known as Arabica) commercial lots from different geographical origin and, for the first time, in different samples of coffee wild species (Coffea liberica and Coffea pseudozanguebariae). Quantification (total SiQA ranging from 3 to 5 mg/100 g) let to reconsider these chlorogenic acids as unique phytochemical markers of Robusta being present in the same quantity and distribution in C. liberica as well. Gardeniae Fructus samples (fruits of Gardenia jasminoides) have additionally been characterized as this matrix is recognized as one of the few naturally occurring SiQA sources. The SiQA regioisomer content (total SiQA about 80 mg/100 mg) fully supports the proposal to use this matrix as a surrogate standard for further studies.     

Coumarin-cored carbazole dendrimers as solution-processed non-doped green emitters for electroluminescent devices

A series of green-emitting thiophenyl coumarin-cored carbazole dendrimers containing carbazole dendrons up to the third generation as substituent were synthesized and characterization. Their optical, thermal, electrochemical, and electroluminescent properties as non-doped solution-processed light-emitters for OLEDs were investigated. By incorporating carbazole dendrons in the molecule, we are able to reduce the crystallization and retain the high emissive ability of a planar thiophenyl coumarin fluorescent core in the solid state as well as improve the thermal stability of the material. These dendrimers showed a bright-green fluorescence and can form morphologically stable amorphous thin films with glass-transition temperatures as high as 285 °C. Simple structured solution-processed OLEDs using these materials as hole-transporting non-doped emitters and BCP as a buffer layer emit a stable green electroluminescence (λ_EL=502–526 nm) with high luminance efficiencies (up to 7.92 cd/A at 7.39 mA/cm²) and high green color purity (CIE=0.26, 0.62, which are close to the pure green color).     

Hydrides compounds for electrochemical applications

Hydrides have been used since a long time for solid-state hydrogen storage and electrochemical nickel-metal hydride batteries. Besides these applications, growing attention has been devoted to their development as anode materials, as well as solid electrolytes for Li-ion and other ion batteries. Herein, we review and summarize the recent advances of hydrides as negative electrodes for Ni-MH and A-ion batteries (A = Li, Na), and as electrolyte for all solid-state batteries (ASSB). Metallic hydrides such as intergrowth compounds are highlighted as the best compromise up to now for Ni-MH. Regarding anodes of Li-ion batteries, MgH₂, especially its combination with TiH₂, provides very promising results. Complex hydrides such as Li-borohydride and related closo-borates and monovalent carborate boron clusters appear to be very attractive as solid electrolytes for Li-based ASSB, whereas closo-hydroborate sodium salts and closo-carboborates are investigated for Na- and Mg-ASSB. Finally, further research directions are foreseen for hydrides in electrochemical applications.     

Capillary electrophoresis‐based enzyme assays for β‐lactamase enzymes

Generic in‐capillary as well as offline CE‐based enzyme assays were developed for serine‐β‐lactamases and metallo‐β‐lactamases. The hydrolysis of benzylpenicillin to benzylpenicilloic acid was analyzed using 100 mM sodium phosphate solution, pH 6.0, as a background electrolyte. In‐capillary assays employed an uncoated as well as a polyethylene oxide‐coated capillary, while the offline assays employing long end and short end injection were performed in an uncoated capillary. Using procaine hydrochloride or 4‐hydroxybenzoic acid as internal standard, the respective assays were validated with regard to linearity, LOD and LOQ, repeatability, precision, and accuracy. The assays were applied to the determination of the Michaelis‐Menten parameters K_m and V_max of Bacillus cereus penicillinase as well as New Delhi metallo‐β‐lactamase 1 and Verona integrin‐encoded metallo‐β‐lactamase 2. Furthermore, the inhibition of the enzymes by irreversible and competitive inhibitors was evaluated. Comparable data were obtained with all assays. The use of a simple substrate ensured broad applicability to the various types of β‐lactamases.     

New synthetic routes to nano-composites with ceramic particles, using lanthanide compounds

Gas-phase as well as sol–gel techniques can be used to access to materials which contain two sorts of solid phases, of which one is mostly acting as the matrix. The choice of the molecular precursor in both processing techniques is crucial to obtain the desired composite product. Single source precursors have advantages over multi source precursors, as they allow a simplified technique and often also lead to purer materials. Moreover, the same precursor may behave similarly in the gas phase or wet process or may behave very differently. In this review composite compounds are discussed with Al₂O₃ mostly acting as a matrix and with Ln₂O₃ (Ln = lanthanide element) acting as a second phase. Two processes for Nd:YAG materials are described in more detail as well as some new alcoholates of lanthanides derived from carbinol substituted by thiophenes.     

New metal free organic dyes incorporating heterocyclic Benzofuran core as conjugated spacer: Synthesis,Opto-electrochemical,DFT and DSSC studies

Synthesis of a series of new organic photosensitizers, designated as BZ1 - BZ4 , was achieved by incorporating benzofuran core as π-spacer, triphenylamine (TPA) and 4-methoxy triphenylamine (4-MeO-TPA) as donors and cyanoacrylic acid (CAA) and rhodanine-3-acetic acid (RAA) as acceptor/anchoring groups. Structurally, dyes BZ1 and BZ2 carry TPA and 4-MeO-TPA as donors, respectively, whereas CAA constitutes as a common acceptor. On the other hand, BZ3 and BZ4 incorporate TPA and 4-MeO-TPA as donors, respectively, and RAA serves as a common acceptor. Key steps to access BZ1 - BZ4 involved Wittig olefination, reduction of cyano groups to aldehyde, and finally Knoevenagel condensation. In UV–visible spectra, dyes BZ1 - BZ4 exhibited intramolecular charge transfer (ICT) maxima in the range of 503 nm to 534 nm and their extinction coefficients varied from 22,600 to 40,400 M⁻¹ cm⁻¹. Using cyclic voltammetry and UV–visible data, we calculated the optical band gaps, (E₀₋₀) of BZ1-BZ4 to be 2.09, 2.00, 2.01, and 1.93 eV, respectively. DFT studies revealed that HOMOs of dyes were localized essentially on the donors triphenylamine groups, whereas the LUMOs are largely confined over electron acceptors CAA and RAA as well as partly diffused into the benzofuran spacer. DSSCs, configured using BZ1 - BZ4 as photosensitizers, showed fill factors (ff) in the range of 0.57 to 0.76, comparable to standard N3 dye (0.67). In addition, BZ1 and BZ2 dyes with CAA as an acceptor also exhibited decent open circuit voltage (V_oc) in the range of 0.61 to 0.63 relative to the 0.66 observed for N3 dye. Dyes BZ1-BZ2 carrying CAA as an acceptor exhibited an efficiency (η) of 2.03% and 1.49%, respectively, against the benchmark N3 dye, showing η of 5.02%. Due to poor V_oc and short circuit current density (I_sc), dyes BZ3-BZ4 carrying RAA as acceptor/anchoring group performed significantly poor, showing η of 0.08%, and 0.32%, respectively.     

Total cross sections of electron collisions with S atoms; H2S,OCS and SO2 molecules (Ei ≥ 50 eV)

Collisions of intermediate to high energy electrons are considered with S-atoms as well as H₂S, OCS and SO₂ molecules as targets. We employ e^- atom total cross sections calculated in the complex optical potential, to calculate e^--molecule total cross sections in a simple and a modified Additivity Rule. Our total (elastic + inelastic) cross sections above 50 eV, fare reasonably well as compared to various experimental and theoretical data. The calculated inelastic cross sections serve as the upper limit of total ionization cross sections. Results are presented graphically from about 10 to 5000 eV.     

Preparation,characterization, and applications of a novel solid-phase microextraction fiber by sol-gel technology on the surface of stainless steel wire for determination of poly cyclic aromatic hydrocarbons in aquatic environmental samples

A novel solid-phase microextraction(SPME) fiber was prepared using sol–gel technology with ethoxylated nonylphenol as a fiber coating material. The fiber was employed to develop a headspace SPME–GC–MS method suitable for quantification of 13 polycyclic aromatic hydrocarbons (PAHs) in water samples. Surface characteristics of the fibers were inspected by energy dispersive X-ray (EDX) spectroscopy as well as by scanning electron microscopy (SEM). The SEM measurements showed the presence of highly porous nano-sized particles in the coating. Important parameters affecting the extraction efficiency such as extraction temperature and time, desorption conditions as well as ionic strength have been evaluated and optimized. In the next step, the validation of the new method have been performed, finding it to be specific in the trace analysis of PAHs, with the limit of detection (LOD) ranging from 0.01 to 0.5 μg L⁻¹ and the linear range from the respective LOD to 200 μg L⁻¹with RSD amounting to less than 8%. The thermal stability of the fibers was investigated as well and they were found to be durable at 280 °C for 345 min. Furthermore, the proposed method was successfully applied for quantification of PAHs in real water samples.     

Direct-scanning alpha-spectrometer for americium and plutonium contamination on highly-enriched uranium surfaces

Trace²³⁹Pu and²⁴¹Am contamination on a surface whose alpha count is dominated by²³⁵U and²³⁴U decay has been successfully quantified by counting swipes in external alpha-spectroscopy chambers. The swipe process, however, is labor intensive and subject to uncertainties in the swiping process as well as degraded spectral resolution due to the presence of the swipe material. A multichannel instrument for automated in situ measurements of interior and exterior contamination has been developed which incorporates a rotary table, 13 fixed ion-implanted silicon detectors, and spectroscopy electronics. Custom software was written to allow alpha-spectrometer to function as a virtual instrument in the LabView environment. This system gives improved speed and resolution as well as a complete log of the location of areas of high surface contamination, a feature not practical to obtain by other methods, and one which opens the possibility of long term studies such as Pu outgrowth evaluation employing the instrument. We present performance data as well as system integration, calibration, control, and dynamic geometric efficiency calculations related to the design of this and next generation systems.     

Chiral 1,2-diaminocyclohexane as organocatalyst for enantioselective aldol reaction

A simple and commercially available chiral 1,2-diaminocyclohexane as catalyst, hexanedioic acid as co-catalyst could efficiently catalyze the asymmetric aldol reaction in MeOH-H₂O. Cyclic ketones as aldol substrates gave the anti-β-hydroxyketone products with moderate to good yields, diastereoselectivity and enantioselectivity (up to 78% yield, >20:1 anti/syn, 94% ee). Hydroxyacetone as aldol substrate afforded the syn-α, β-dihydroxyketones as major products in up to 85% yield with good enantioselectivity (up to >20:1 syn/anti, 93% ee).     

Wholly aromatic polyamide-hydrazides. IV. Structure–property relationships for polymers containing p-phenylene and m-phenylene units

A series of wholly aromatic polyamide-hydrazides was investigated in order to acquire clear understanding of the influence exerted by controlled structural variations in these polymers upon some of important properties, such as chain flexibility, membrane permselectivity, and thermal as well as thermo-oxidative stability. For that reason, the content of para and meta phenylene units was varied within this series so that the changes in the latter were 12.5 mol % from polymer to polymer, starting from an overall content of 0–50 mol %. The polymers were prepared by a low-temperature solution polycondensation reactin of p-aminobenzhydrazide (ABH) and terephthaloyl chloride (TCI), isophthaloyl chloride (ICI), and their appropriate combinations in N,N-dimethylacetamide (DMA) as solvent and all of these preparations were monitored viscometrically in order to prepare the products with as similar as possible average molecular weights. Polymer structures were characterized by elemental analysis, infrared spectrometry, and ¹³C NMR spectroscopy, while their molecular weights were determined by light scattering and dilute-solution viscometry. Polymer properties were evaluated by solution viscometry, reverse osmosis tests, and thermal gravimetric analysis. The results obtained during the preparation of these materials, their subsequent structural characterization, and their property evaluations are discussed. They clearly indicate that substitution of m-phenylene units for p-phenylene ones within this polymer series led to an increase in polymer chain flexibility (from what is usually referred to as semiflexible or semirigid to typically flexible macromolecules), disrupted selectivity of the asymmetric thin membranes under reverse osmosis conditions and decreased stability at elevated temperatures in inert as well as in oxidative atmospheres.     

A novel approach for the one-pot synthesis of linear and angular fused quinazolinones

A convenient and inexpensive one step methodology has been developed for the synthesis of linear and angular fused quinazolinones. The protocol, which uses amino heterocycles and o-bromo benzyl/naphthyl bromides as reactants, CuI as catalyst, Cs₂CO₃ as base, l-proline as ligand, and DMF as solvent, proceeds via nucleophilic aromatic substitution of the N-heteroaromatic cationic intermediate followed by in situ aerial oxidation at the benzylic position to the quinazolinone scaffold.     

Investigation on stability and preservation of antimonite in iron rich water samples

The stability of antimonite in iron rich water samples is rather poor. The aim of the study was to find a simple procedure by using preservation agents to keep the speciation information from sampling till analysis. Species analysis of antimony traces (lower μg L⁻¹ range) was done by HPLC–ICP-MS. Phosphoric acid, tartrate, and EDTA were tested as preservation agents in comparison to no addition. The use of EDTA as the preservation agent provided the best results. The suggested procedure is to add 20 mM EDTA as final concentration immediately during sampling and store them at dark and cool (6 °C) as usual. Using this procedure, the stability of Sb(III) as well as of Sb(V) was proven for at least 7 days, even for high iron concentrations.     

Recent discoveries on the structure of iodine(iii) reagents and their use in cross-nucleophile coupling

This perspective article discusses structural features of iodine(iii) compounds as a prelude to presenting their use as umpolung reagents, in particular as pertains to their ability to promote the selective coupling of two nucleophilic species via 2e⁻ oxidation.

This perspective article discusses structural features of iodine(iii) compounds as a prelude to presenting their use as umpolung reagents, to promote the selective coupling of two nucleophilic species via 2e⁻ oxidation.     

NMR Spectroscopy of Poly(Vinyl Chloride) Defects. 1H-NMR Analysis of the 1,2-Dichloroethyl End Group to the Triad Level

Abstract

We synthesized and analyzed by ¹H NMR the mixture of meso (m) and racemic (r) 1,2,4,5-tetrachloropentane, as well as the mixture of mm, mr, and rr isomers of 1,2,4,6,7-pentachloroheptane and its precursor 1,2,6,7-tetrachloroheptane-4-ol as models for PVC 1,2-dichloroethyl end group. We were able to correct previous assignments as well as extend the ¹H-NMR analysis of this end group in PVC to the triad level.     

Preparation and adsorption properties of glucose molecularly imprinted polymers in hydrous solution for effective determination of glucose in fruits by MISPE–HPLC

In this paper, a kind of surface molecular imprinting polymers in hydrous solution, with glucose selectively recognition, was successfully synthesized by surface molecular imprinting method, using glucose (Glu) as template molecule, acrylamide as functional monomers, N,N′-methylenebisacrylamide as the cross-linking agent, ammonium peroxydisulfate as the initiator, activated silica gel (SiO₂@NH₂) as support particles. The influences of cross-linker, initiator as well as support particles amount on the adsorption capacity of Glu-MIPs were performed by single-factor experiments. The optimum conditions were 100 mg of cross-linker, 25 mg of initiator and 1 g of SiO₂@NH₂. The adsorption and thermodynamics research revealed that the adsorption of MIPs was fitted to Langmuir, maximum imprinting factor of 2.49 and maximum absorption capacity of 50.06 mg/g. Furthermore, a procedure of extraction of glucose from real fruits samples using the Glu-MIPs as solid-phase extraction adsorbent was developed to apply in analytical techniques.