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Chiral Ph-dbfox (Ph-dbfox = (R,R)-4,6-dibenzofurandiyl-2,2′-bis(4-phenyloxazoline))/Zn(NTf2)2catalyzed enantioselective Friedel–Crafts reactions of β-CF3acrylates with pyrroles and indoles have been investigated, which afforded the corresponding chiral trifluoromethyl pyrrole and indole derivatives in high yields (90–99%) with a range of 66–99% ee values. With the aid of the chiral adduct of the asymmetric Friedel–Crafts reaction, the chiral trifluoromethylated heliotridane has been successfully constructed in good total yield. [ABSTRACT FROM AUTHOR]

Selective oxidation of tetralin by molecular oxygen over mesoporous CrMCM-41 molecular sieve catalyst using supercritical carbon dioxide (scCO2) solvent has been investigated. CrMCM-41 catalyst gave high selectivity (96.2%) and good yield (63.4%) of 1-tetralone. The presence of scCO2medium improves 1-tetralone selectivity and suppresses leaching of chromium from the CrMCM-41. The activity over recycled CrMCM-41 remains nearly the same under the present experimental conditions. The effect of the reaction parameters on CrMCM-41 was also studied in detail along with comparison of its catalytic activities with other mesoporous catalysts, viz.MnMCM-41, CoMCM-41, microporous CrAPO-5, CoMFI, and macroporous Cr/SiO2catalyst, respectively. In addition this catalytic system was also applied for the oxidation of other benzylic compounds such as indane, fluorene, acenaphthene and diphenylmethane. [ABSTRACT FROM AUTHOR]

The voltammogram features of TMPD2+/TMPD, N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD), reflect the intensive instability of TMPD2+ in aqueous solutions. The instability of TMPD2+ strongly restricts its application in electrochemical syntheses. The striking feature of this paper is the stabilization of this redox-active species via amine functionalization. The procedure started with the chemical reaction of TMPD with sodium nitrite to produce N-(2-nitro-4-(dimethylamino)phenyl)-N-methylnitramide (NDPM). The nitro functional group of NDPM was reduced electrochemically to the corresponding amine derivative, N-(2-amino-4-(dimethylamino)phenyl)-N-methylnitramide (ADPM). Unlike TMPD2+/TMPD, the voltammetric results of ADPM presented a reversible redox process at low redox potentials. The phenomenon introduces ADPM as an effective compound for the electrochemical synthesis of p-phenylenediamine derivatives in green conditions. To examine the hypothesis, we have developed a paired electrochemical synthesis method via the reduction of NDPM at the surface of the cathode followed by oxidation at the anode surface in the presence of arylsulfinic acids as typical nucleophiles. The electrochemical synthesis was successfully performed under green conditions in the absence of redox mediators. [ABSTRACT FROM AUTHOR]

The emphasis of this mini review is on the representation of dynamic NMR methods to obtain kinetic and mechanistic information on the equilibria of metal complexes in aqueous solution. A brief discussion of the basic aspects of NMR relaxation and the effect of chemical exchange on that providing information on the dynamics of equilibrium is given. The experimental and computational tools for extracting kinetics from dynamic data are also described, underlining the importance of a multinuclear approach. It reviews some theoretical background citing useful books and papers on the chemical applications of the most often used dynamic NMR methods. It focuses on the use of these methods for elucidating reaction pathways, and mechanisms and for determination of kinetic parameters, through examples, rather than on the technical and theoretical details or on an exhaustive survey of the present literature. The usefulness of the multinuclear NMR approach in this context is illustrated quoting cases when it has been applied. Most of the concrete experimental data refer to the authors own work on the kinetics of lanthanide, uranium and thallium complexes; however, the general aspects are always emphasized. The aim of this paper is to encourage coordination chemists to employ NMR and discover that the dynamic aspects of this very powerful technology are exactly made for coordination chemistry. [ABSTRACT FROM AUTHOR]

Reactive distillation is a process intensification technology that combines a chemical reaction with distillation in a device. Enzymatic Reactive Distillation (ERD)—the application of immobilized enzyme catalysts instead of traditional acid–base catalysts in reactive distillation has attracted much attention due to its high selectivity and mild process conditions. However, to apply ERD to industrial processes, it is critical to address constraints such as the cost and stability of immobilized enzyme catalysts. Herein, in this paper, Candida antarctica lipase B (CALB) was immobilized in a commercial resin "NKA" by a hydrophobic interaction, and the immobilized enzyme was PEGylated by a series reaction. Both the stability and catalytic performance of the prepared NKA-CALB-PEGylated are significantly improved. The catalytic efficiency of NKA-CALB-PEGylated (80.1%) in the transesterification reaction system is slightly higher than those of NKA-CALB (71.7%) and Novozyme435 (69.3%), and significantly higher than that of Sol gel-CALB (60%) published in our previous literature. Additionally, NKA-CALB-PEGylated retained an initial activity of 92.4% after repeated use six times, which was significantly higher than those of Novozyme435 (60.2%) and NKA-CALB (78.6%). Therefore, the prepared stable and economical enzyme catalyst has great prospects for applications in the ERD industry. [ABSTRACT FROM AUTHOR]

LaMnO3 and LaCoO3 perovskite nanoparticles have sprung up as the platinum group-metal (PGM)-free catalysts of NO oxidation to reduce NOX in the exhaust. In this paper, we present mesoporous LaMnO3 and LaCoO3 with rhombohedral structures prepared by a facile molten-salt synthesis method. LaMnO3 and LaCoO3 achieved NO oxidation performance with the highest NO conversions of 85% and 94% at 300 °C, which may be improved by K and Na introduced via flux. [ABSTRACT FROM AUTHOR]

This paper presents a series of six examples of 1,1-difluoro-3-aryl(heteroaryl)-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uides (2)―in which aryl(heteroaryl) = phenyl, 4-MeC6H4, 4-N(CH3)2C6H4, 4-NO2C6H4, 2-naphthyl, and 2-thienyl―as pyridine-based boron heterocycles with variable ligand structures. The heterocycles 2 were easily synthesized at yields of 51–70% from reactions―at room temperature for 24 h―of simple N-(pyridin-2-yl)benzamides (1) with BF3·Et2O, and they were fully characterized by 1H-, 13C-, 19F-, and 11B-NMR spectroscopy, GC-MS, and X-ray diffractometry. The optical and electrochemical properties of 2 (UV-vis spectra, fluorescence spectra, quantum yield calculations, Stokes’ shifts, redox potentials, and DFT calculations) were determined and discussed. BSA-binding experiments and molecular docking studies of new complexes 2 were performed and correlated between each other. [ABSTRACT FROM AUTHOR]

Based on the recent results obtained in papers it has become possible to create an original theory for the quantitative detection/description of different electrode states in electrochemical measurements. This new approach allows for the taking into account of the influence of the apparatus function and for the quantitative comparison of two similar electrodes used for measurements of the same substance. The new approach does need unjustified suppositions and a specific model for the description of measured curves; the desired curves (reduced to an ideal experiment after the elimination of the apparatus function) are expressed quantitatively in terms of the so-called intermediate model. The fitting parameters of the intermediate model coincide with the fragment of the Fourier series used as the fitting function. Besides, the distribution of measurements has a universal distribution and can be expressed in terms of the fitting parameters associated with a beta distribution function. The new approach opens new perspectives for conventional electrochemistry and can be used as an accurate tool for the description of reproducible data, the detection of “traces” and the selection of the “best fit” model among competitive hypotheses suggested by theoretical electrochemistry. [ABSTRACT FROM AUTHOR]

Here we report self-assembly of ultrathin gold nanowires and single-walled carbon nanotubes with an ultrahigh aspect ratio as a highly sensitive substrate for surface enhanced Raman spectroscopy. And we demonstrated that the hybrids were especially efficient in adsorption of aromatic molecules such as 4-mercaptobenzoic acid and the hybrids materials could be used as a novel platform for trace level detection in the verification of paper notes through the Raman enhancement technique. [ABSTRACT FROM AUTHOR]

A series of luminescent salicylaldehyde azines (SAs) containing different electron-accepting substituents (-NO2, -F, and -Cl), electron-donating substituents (-OMe and -NEt2), and a π-extended system (naphthalene ring) are prepared for the application of fluorescent pH probes. These SAs inheriting the aggregation-induced emission (AIE) features display strong blue, green, and red fluorescence with large Stokes shifts in water and solid medium. Combining the advantages of AIE and the chemical reactivity of phenol towards OH-/H+, most of the SAs can be used as ratiometric fluorescent pH probes with a broad pH range (2-14) in water and solid medium (test paper). Moreover, the inherent relationship between their chemical structures and AIE properties/pKa values (7.5-13.3) is studied, which provides unequivocal insights into the design of AIE-active dyes and their applications. [ABSTRACT FROM AUTHOR]

This paper describes the immobilization of citrate capped gold nanoparticles (cit-AuNPs) on indium tin oxide (ITO) and glassy carbon electrode (GCE) surfaces using a electroactive linker, meso-tetra(para-aminophenyl)porphyrinatocobalt(ii) Co(ii)MTpAP. The immobilization of cit-AuNPs on Co(ii)MTpAP was achieved with the aid of amine groups present on the self-assembled monolayer (SAM) of Co(ii)MTpAP. This was confirmed by UV-vis, atomic force microscopy (AFM), cyclic voltammetry, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques. The particle coverage estimated from AFM was found to be ∼65% which is higher than the previously reported linkers used for immobilization. The AFM image shows that the cit-AuNPs were densely packed on Co(ii)MTpAP. Furthermore, the electrocatalytic activity of the AuNP modified electrode was examined by studying the oxidation of hydrazine. Interestingly, the cit-AuNPs immobilized on Co(ii)MTpAP showed a greater catalytic effect towards hydrazine oxidation than cit-AuNPs immobilized on free base porphyrin. This was attributed to the synergistic effect arising from both AuNPs and Co(ii). [ABSTRACT FROM AUTHOR]

In the course of our studies on nitrogen trifluoride dissociation, we consider in this paper two different sets of reactive systems: the first one consists of the abstraction and the exchange channels of NF3 + F and the other is composed of the unimolecular and the abstraction production of N2 + F. Accurate electronic properties are determined and applied in the scope of the transition state theory (TST) to obtain thermal rate constants for these systems. An extensive investigation in terms of minimum energy paths and intrinsic reaction coordinates was previously carried out in order to ensure the good quality of our TST results. We apply Wigner corrections to consider tunneling effects whenever their importance is numerically verified. The obtained results for the abstraction channel thermal rate constants are in good agreement with experimental data which indicates that this kind of study is of potential use to help to clarify the decomposition mechanism of NF3. [ABSTRACT FROM AUTHOR]

The aim of the present paper was to investigate the reaction of quercetin, the flavonol very often used as a dietary supplement, with [AuCl4]− ions. The reaction was studied spectrophotometrically using the equimolar solutions in 1 : 1 water–methanol at pH ∼ 2. The spectrophotometric data indicated the formation of the products with an absorption maximum at 295 nm in all cases, characteristic of the oxidized forms of quercetin. HPLC coupled with DAD and LC-MS analysis of the reaction products suggested that the oxidation of quercetin resulted in the generation of similar metabolites including quinone and various oxidized quercetin–solvent adducts. In addition, cyclic voltammetric measurements confirmed that under applied experimental conditions, the reduction of Au(iii) to Au(0) took place. The reduction species in the reaction mixture were Au(iii) ions, while Au(i) disproportionates back to Au(iii) and Au(0). The newly generated Au(iii) ions further oxidized 3′,4′-dihydroxy groups of quercetin adducts obtained after first 2e− oxidation, giving the final reaction products. Based on the identification of reaction products, the reaction mechanism for the oxidation of quercetin in the presence of Au(iii) which involves two 2e− transfer processes was proposed. [ABSTRACT FROM AUTHOR]

Natural photosynthetic pigments bacteriochlorophylls c, dand ein green bacteria undergo self-assembly to create an organized antenna system known as the chlorosome, which collects photons and funnels the resulting excitation energy toward the reaction centers. Mimicry of chlorosome function is a central problem in supramolecular chemistry and artificial photosynthesis, and may have relevance for the design of photosynthesis-inspired solar cells. The main challenge in preparing artificial chlorosomes remains the synthesis of the appropriate pigment (chlorin) equipped with a set of functional groups suitable to direct the assembly and assure efficient energy transfer. Prior approaches have entailed derivatization of porphyrins or semisynthesis beginning with chlorophylls. This paper reports a third approach, the de novosynthesis of macrocycles that contain the same hydrocarbon skeleton as chlorosomal bacteriochlorophylls. The synthesis here of Zn(ii) 3-(1-hydroxyethyl)-10-aryl-131-oxophorbines (the aryl group consists of phenyl, mesityl, or pentafluorophenyl) entails selective bromination of a 3,13-diacetyl-10-arylchlorin, palladium-catalyzed 131-oxophorbine formation, and selective reduction of the 3-acetyl group using BH3·tBuNH2. Each macrocycle contains a geminal dimethyl group in the pyrroline ring to provide stability toward adventitious dehydrogenation. A Zn(ii) 7-(1-hydroxyethyl)-10-phenyl-17-oxochlorin also has been prepared. Altogether, 30 new hydroporphyrins were synthesized. The UV-Vis absorption spectra of the new chlorosomal bacteriochlorophyll mimics reveal a bathochromic shift of ∼1800 cm−1of the Qyband in nonpolar solvent, indicating extensive assembly in solution. The Zn(ii) 3-(1-hydroxyethyl)-10-aryl-131-oxophorbines differ in the propensity to form assemblies based on the 10-substituent in the following order: mesityl

This paper reports the efficient core-substitution of halogenated naphthalene diimides utilizing the Suzuki cross-coupling reaction to install various aryl substituents at the 2,6 positions. The UV-visible spectra of these compounds show a clear absorbance red shift and an enhanced fluorescence output, making them potential candidates for solar-cell dyes and electroactive elements for supramolecular materials. [ABSTRACT FROM AUTHOR]