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Preview: Chinese Journal of Chemistry

Chinese Journal of Chemistry



Wiley Online Library : Chinese Journal of Chemistry



Published: 2018-01-01T00:00:00-05:00

 



Cu(I)-Catalyzed Asymmetric Cross-Coupling of N-Tosylhydrazones and Trialkylsilylethynes: Enantioselective Construction of C(sp)-C(sp3) Bonds

2017-12-15T07:41:58.792507-05:00

The first catalytic enantioselective C(sp)-C(sp3) cross-coupling reaction between N-tosylhydrazones and trialkylsilylethynes in the presence of Cu(I) salts and chiral phosphoramidite ligands was developed. A series of synthetically interesting, functionalized alkynes were obtained with moderate to good enantioselectivities (up to 83% ee). Cu(II) carbene migratory insertion is proposed to be the enantio-determining step.



A High Dielectric N-type Small Molecular Acceptor Containing Oligoethyleneglycol Side-Chains for Organic Solar Cells

2017-12-12T09:48:33.475872-05:00

We report a new small molecular acceptor, ITIC-OEG, which is based on indacenodithieno[3,2-b]thiophene and 1,1-(dicyanomethylene)-3-indanone including oligoethyleneglycol (OEG) side-chains. ITIC-OEG was found to have higher dielectric constant (εr = 5.6) than that of a reference molecule of ITIC with normal alkyl substituents (εr = 3.9). The dielectric constant of medium influences significantly the exciton binding energy and the resulting charge separation and recombination. The optical, electrochemical and morphological properties of ITIC-OEG and its photovoltaic characteristics were investigated by blending with a semi-crystalline donor polymer, PPDT2FBT, with comparison to those of ITIC. ITIC-OEG shows more red-shifted absorption and stronger crystalline packing than ITIC. However, the lower photovoltaic performance (with 1.58% power conversion efficiency, PCE) was measured for PPDT2FBT:ITIC-OEG, compared to PPDT2FBT:ITIC (5.52% PCE). The incompatibility between PPDT2FBT and ITIC-OEG (due to high hydrophilic nature of OEG chains) resulted in poor intermixing with large domain separation over 300 nm, showing inefficient charge separation and significant charge recombination. Therefore, to investigate the effect of dielectric constant of the materials on the charge separation and recombination, the blend morphology of the PPDT2FBT:ITIC-OEG should be optimized first by improving their miscibility and phase separation.



Catalytic conversion of CO2 to cyclic carbonates through multifunctional zinc-modified ZSM-5 zeolite

2017-12-08T07:35:41.164511-05:00

The production of fine chemicals using CO2 as C1 building block through inexpensive heterogeneous catalysts with high efficiency under low pressure is challenging. Herein we propose for the first time the utilization of a multifunctional heterogeneous zinc-modified HZSM-5 (ZnHZSM-5) catalyst for upgrading CO2 by incorporation into cyclic carbonates from CO2 and epoxides. Owing to the nice surface properties such as abundant Lewis acid, Brønsted acid and Lewis base sites, large surface area, and plenty of micropores, CO2 could be concentrated and well activated in ZnHZSM-5 verified by CO2-TPD and TG-MS etc. Meanwhile, the epoxides were also activated through metal center and hydrogen bond. Therefore, the reaction can easily assemble at the catalyst interface and show exceptional performance, affording the aimed products with high yield of up to 99% in the presence of commercial tetra-n-propylammonium bromide (90% in kilogram scale with 0.004 mol% ZnHZSM-5 and 0.015 mol% nPr4NBr).



Solution-processed titanium chelate used as both electrode modification layer and intermediate layer for efficient inverted tandem polymer solar cells

2017-12-07T08:03:26.258906-05:00

Organic polymer solar cells (PSCs) have attracted increasing attention due to light weight, low cost, flexibility and roll-to-roll manufacturing. However, the limited light harvest range of the photoactive layer greatly restrains the power conversion efficiency (PCE) enhancement. In order to expand the light absorption range and to further enhance the PCE of the PSCs, tandem structures have been designed and demonstrated. In tandem solar cell, the intermediate layer (IML) plays a critical role in physically and electrically connection of the two subcells. Herein, we apply titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as both electrode modification layer and intermediate layer to investigate the feasibility in inverted tandem polymer solar cells. The same photoactive layers of PTB7-Th:PC71BM are adopted in both front and rear subcells to simplify the evaluation of effectiveness of TIPD layer in tandem structures. By modulating the treatment condition of IML and the thickness of photoactive layer, efficient inverted tandem PSCs have been achieved with minimized voltage loss and excellent charge transportation, giving a best Voc of 1.54 V which is almost double of the single bulk heterojunction (BHJ)-PSC (0.78 V) and an enhanced PCE up to 8.11%.



Metallaaromatics containing main-group heteroatoms

2017-12-01T04:45:33.396645-05:00

Metallaaromatics are metallacycles that are derived from the formal replacement of a carbon atom in the framework of organic aromatics with a metal fragment. As an important subclass of metallaaromatics, metallaaromatics that contain main-group heteroatoms have attracted considerable attention. In the past ten years, we have developed several new methods to construct metallaaromatics as well as those containing main-group heteroatoms, such as metallapyridine, metallapyridinium, metallapyridyne, metallafuran, metallabenzothiazole, metallabenzoxazole, metallabenzthiophene, aza-metallapentalene and some novel tricyclic/tetracyclic metallaaromatics. In addition, interesting reactions such as the first hetero-Diels Alder reaction between 1-metalla-1,3-dienes and nitriles, the first intramolecular nucleophilic aromatic substitution (SNAr) reaction of metallabenzene, and the first iodine-mediated electrophilic cyclizations of a metallabenzene complex were demonstrated. In this account, recent and novel approaches for their synthesis and property analyses are summarized. The structural diversity and unique properties of metallaaromatics containing main-group heteroatoms will strongly inspire further investigation of these species and provide a wide range of potential applications.



A BODIPY-based fluorescent probe for thiophenol

2017-11-28T08:11:35.345645-05:00

Thiophenol has been listed as one of the main sources of pollution. Sensitive probes for thiophenol are very significant. Herein a BODIPY-based fluorescent probe, named BDP, for poisonous thiophenol detection has been reported. BDP shows rapid response (15 s) and clear fluorescence enhancement (30 folds) to thiophenol in solution. The intensity of fluorescence and concentration of thiophenol have a good linear relationship. The detection limit is as low as 13.6 nM. BDP is stable towards pH and light radiation. Cell experiments demonstrate that BDP has good cell membrane penetrability, low cell toxicity and excellent imaging properties in living cells. Therefore, BDP has significant value on the detection of thiophenol in solution and in living cell. Copyright © 2017 John Wiley & Sons, Ltd.



Difunctionalization of Alkynes: Synthesis of Novel Fluoropolymer Materials

2017-11-28T07:56:07.77882-05:00

(A Pd-catalyzed multi-component carbonylative difluoroalkylation/perfluoroalkylation through the alkyne difunc-tionalization process has been developed. Besides, new functional fluoropolymer materials have been successfully synthesized. Owing to the presence of the fluorine element, the materials present excellent chemical resistance, high-temperature-resistance and outstanding hydrophobicity simultaneously, which may significantly make them great appealing in the industrial production and life science as well.) Copyright © 2017 John Wiley & Sons, Ltd.



Efficient P-Chiral Biaryl Bisphosphorus Ligands for Palladium-Catalyzed Asymmetric Hydrogenation

2017-11-27T08:09:38.087977-05:00

A series of structurally novel P-chiral biaryl bisphosphorus ligands L1-5 (BABIBOPs) are developed, providing high efficiency for the first time in palladium-catalyzed asymmetric hydrogenation of β-aryl and β-alkyl substituted β-keto esters. With the Pd-L3 (iPr-BABIBOP) catalyst, a series of chiral β-hydroxyl carboxylic esters are formed in excellent enantioselectivities (up to >99% ee) and yields at catalyst loading as low as 0.01 mol %.



Fabrication of Neutral Supramolecular Polymeric Films via Post-electropolymerization of Discrete Metallacycles

2017-11-27T07:57:38.356954-05:00

Self-assembly post-modification has proven to be an efficient strategy to build higher-order supramolecular architectures and functional materials. In this study, we successfully realized the construction of a new family of neutral supramolecular polymeric films containing well-defined metallacycles as the main scaffolds through combination of coordination-driven self-assembly with post-electropolymerization. The obtained neutral polymeric materials were fully characterized by the cyclic voltammogram (CV), SEM, and TEM. The thickness of the films was able to be well regulated by the number of scanning cycles. Moreover, we found that the shape of the metallacycles and the number of triphenylamine moieties played important roles in the formation of the final polymer films. We believe that the introduction of the neutral metallacycles into the final polymer structures not only enriches the library of supramolecular polymeric films but also provides a new platform to study neutral molecule detection, separation, and capture.



Microwave Synthesized In2S3@CNTs with excellent properties in lithium-ion battery and electromagnetic wave absorption

2017-11-27T07:35:26.400177-05:00

The three-dimensional nanoflower-like β-In2S3 composited with carbon nanotubes (CNTs) had been synthesized by a single mode microwave-assisted hydrothermal technique. The In2S3 and CNTs nanocomposites (In2S3@CNTs) were investigated as the anodes material of lithium batteries (LIBs) and the electromagnetic wave absorption materials. For LIBs applications, the In2S3@CNTs nanocomposite exhibited excellent cycling stability with a high reversible charge capacity of 575 mA h g–1 after 300 cycles at 0.5 A g–1. In addition, the In2S3@CNTs used as electromagnetic wave absorber displayed a maximum reflection loss of −42.75 dB at 11.96 GHz with a thickness of 1.55 mm.



Design, Synthesis, Biological Evaluation and SARs of Novel N-substituted Sulfoximines as Potential Ryanodine Receptor Modulators

2017-11-27T07:26:29.101873-05:00

The sulfoximine group has been evaluated as a pharmacophore. Introducing the sulfoximine structure into medicinal compounds as exciting motifs has brought opportunities in drug discovery. In order to develop new ryanodine receptor (RyR) modulators, a series of phthalamides containing sulfoximine derivatives was designed, synthesized, and evaluated against oriental armyworm and diamondback moth for their insecticidal activities. These studies helped to elucidate the electronic and structural requirements around the sulfoximine motif for insecticidal activity. All new structures were synthesized and characterized by 1H NMR, 13C NMR, HRMS and bioassay and a preliminary structure−activity relationship (SAR) was discussed. The biological assessment indicated that most title compounds showed good to excellent larvicidal activities. Compounds Ia, Ie, and If gave excellent insecticidal activity against oriental armyworm, which showed 100% larvicidal activity at 0.5 mg/L. All compounds showed 100% larvicidal activity at 0.1 mg/L against diamondback moth. In particular, the larvicidal activities of Ie, If, and Ih at 0.0001 mg/L were 50%, 20%, and 40%, respectively, reached as high an activity as commercial flubendiamide (40%, 0.0001 mg/L). Therefore, Ia, Ie, If and Ih could be considered as new lead structures for the development of new ryanodine receptor (RyR) modulators.



Cipaferoids A–C, Three Limonoids Represent Two Different Scaffolds from Cipadessa baccifera

2017-11-20T05:41:11.214543-05:00

Three limonoids cipaferoids A−C (1−3) representing two different scaffolds were isolated from Cipadessa baccifera. Their structures were completely assigned by spectroscopic data, CD exciton chirality method, and X-ray crystallography. Compounds 2 and 3 exhibited moderate antimalarial activity with IC50 values of 9.3 ± 0.1 and 14.7 ± 4.8 μM, respectively.



Upgrading CO2 by incorporation into urethanes through silver-catalyzed one-pot stepwise amidation reaction

2017-11-20T05:40:24.717497-05:00

One-pot two-step stepwise reaction of terminal propargylic alcohols, carbon dioxide, and primary/secondary amines for the effective synthesis of various urethanes through robust silver-catalysed C–O/C–N bond formation is reported. Catalytic activities were investigated by controlling catalyst loading, reaction pressure and time, and very high turnover number (turnover frequency) was obtained: 3350 (35 h-1) with 0.01 mol% silver catalyst under 0.1 MPa, and up to 13360 (139 h-1) with 0.005 mol% silver catalyst under 2.0 MPa at room temperature. The strategy was ingeniously regulated, and synchronously afforded a wide range of β-oxopropylcarbamate and 1,3-oxazolidin-2-one motifs in excellent yields and selectivity together with unprecedented high TON and TOF value.



Nickel-Catalyzed Difluoromethylation of Arylboronic Acids with Bromodifluoromethane

2017-11-17T05:31:52.262808-05:00

Although bromodifluoromethane (BrCF2H) is a simple and readily available fluorine source, direct formation of difluoromethylated arenes with BrCF2H has not been reported. Herein, we describe an efficient method to access difluoromethylated arenes through a nickel-catalyzed difluoromethylation of arylboronic acids with BrCF2H. The reaction exhibits high efficiency, good functional group tolerance and broad substrate scope, thus providing an efficient route for applications in drug discovery and development. Preliminary mechanistic studies reveal that a difluoromethyl radical is involved in the reaction.



Dual Stereocontrol for Enantioselective Hydrogenation of Dihydroisoquinolines Induced by Tuning the Amount of N-Bromosuccinimide

2017-11-15T04:35:26.23283-05:00

An efficient dual stereocontrolin iridium-catalyzed hydrogenation of 1-substituted 3,4-dihydroisoquinolines was realized by tuning the amount of N-bromosuccinimide using chiral ligand of single configuration, providing both enantiomers of 1-substituted 1,2,3,4-tetrahydroisoquinolineswith up to 89% ee (S) and 98% ee (R), respectively. Dual activation role of N-bromosuccinimide is proposed to be responsible for the reversal of enantioselectivity under two hydrogenation conditions.



Palladium-Catalyzed Cyclization Reaction of o-Haloanilines, CO2 and Isocyanides: Access to Quinazoline-2,4(1H,3H)-diones

2017-12-13T09:57:35.533949-05:00

Quinazoline-2,4(1H,3H)-diones are core structural subunits frequently found in many biologically important compounds. The reaction of 2-​aminobenzonitrile and CO2, which was frequently studied, only provided N3-unsubstituted quinazoline-2,4(1H,3H)-dione compounds. Herein we report palladium-catalyzed cyclization reactions of o-haloanilines, CO2 and isocyanides to prepare N3-substituted quinazoline-2,4(1H,3H)-diones. Electron-rich o-bromoanilines participated in the cyclization reaction using Cs2CO3 at high temperature, and electron-deficient o-bromoaniline or o-iodoaniline substrates conducted the reaction using CsF as base to deliver corresponding quinazoline-2,4(1H,3H)-dione products in good yields. A palladium-catalyzed cyclization reaction of o-haloanilines, CO2 and isocyanides to prepare N3-substituted quinazoline-2,4(1H,3H)-diones in good yields is described.



Highly Stable Molecular Borromean Rings

2017-12-13T09:51:36.361995-05:00

A series of Cp*Rh-based molecular Borromean rings (BRs) are prepared from naphthazarine or metallaligand. Some of as-synthesized BRs display high stability and are formed in high yields in solution. The reason is related to the length ratio of the long-arm linker and short-arm linker, where smaller aspect ratios of the metallarectangles promote improved stability and yields of the BRs in solution. Increasing the width of the metallaligand or pyridyl ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts for the acyl transfer reaction between N-acetylimidazole and (4-(pyridin-4-yl)phenyl) methanol. A series of Cp*Rh-based molecular Borromean rings (BRs) are prepared from naphthazarine or metallaligand. Smaller aspect ratios of the metallarectangles could promote improved stability and yields of the BRs in solution. Increasing the width of ligand hinders the formation of BRs and leads to unoccupied monomeric rectangles, which were further used as catalysts for the acyl transfer reaction between N-acetylimidazole and (4-(pyridin-4-yl)phenyl)methanol.



Cover Picture: Visible Light Accelerated Vinyl C–H Arylation in Pd-Catalysis: Application in the Synthesis of ortho Tetra-substituted Vinylarene Atropisomers (Chin. J. Chem. 1/2018)

2017-12-15T08:22:25.859218-05:00

The cover picture shows a protocol of a palladium-catalyzed arylation of vinylarenes with diaryliodonium salts with the assistance of visible light. A palladium-vinylarene complex may be excited via the visible light irradiation, where the kinetic isotope effect (kH/kD) was around 1.1. However under darkness, the reaction proceeded very slowly, and the kinetic isotope was found as 3.6, indicating the C—H bond cleavage step is the rate-determining step. This protocol avoided high reaction temperature and enabled us to access a series of ortho tetra-substituted vinylarene atropisomers with high enantiospecificity. More details are discussed in the article by Gu et al. on page 11–14. The cover picture shows a protocol of a palladium-catalyzed arylation of vinylarenes with diaryliodonium salts with the assistance of visible light. A palladium-vinylarene complex may be excited via the visible light irradiation, where the kinetic isotope effect (kH/kD) was around 1.1. However under darkness, the reaction proceeded very slowly, and the kinetic isotope was found as 3.6, indicating the C—H bond cleavage step is the rate-determining step. This protocol avoided high reaction temperature and enabled us to access a series of ortho tetra-substituted vinylarene atropisomers with high enantiospecificity. More details are discussed in the article by Gu et al. on page 11–14.






Contents: Chin. J. Chem. 1/2018

2017-12-15T08:22:26.250911-05:00




Visible Light Accelerated Vinyl C–H Arylation in Pd-Catalysis: Application in the Synthesis of ortho Tetra-substituted Vinylarene Atropisomers

2017-11-17T10:00:33.310726-05:00

A visible light accelerated C–H functionalization reaction in palladium-catalyzed arylation of vinyl arenes with diaryliodonium salts is reported in the absence of additional photosensitizer. The kinetic isotope effect (kH/kD) was changed from 3.6 (under darkness) to 1.1 when irradiated by visible light, which indicated that the C–H functionalization step was the rate determining step under darkness and significantly accelerated by the irradiation of visible light. Finally the synthesis of ortho tetra-substituted vinylarene atropisomers with high enantiospecificity was realized via this protocol. Palladium-catalyzed vinyl C–H functionalization with diaryliodonium was promoted by the irradiation of visible light. Under darkness the C–H activation step is the rate determining step, and kinetic isotope effect (KIE) is around 3.6. With the aid of visible light, the C–H activation step was significantly accelerated and KIE was changed to 1.1.



Iron-Catalyzed Aerobic Oxidation of Aldehydes: Single Component Catalyst and Mechanistic Studies

2017-11-17T10:00:44.627622-05:00

An aerobic oxidation of aldehydes towards carboxylic acids in MeCN using 1 atm of pure oxygen or oxygen in air as the oxidant and a catalytic amount of single component catalyst, Fe(NO3)3·9H2O, has been developed. Carboxylic acids with different synthetically useful functional groups were obtained at room temperature. Two mechanistic pathways have been proposed based on isotopic labeling, NMR monitoring, and control experiments. The practicality of this reaction has been demonstrated by conducting several 50 mmol-scale reactions using pure oxygen or an air-flow of ~30 mL/min.



Rh/Lewis Acid Catalyzed Regio-, Diastereo- and Enantioselective Addition of 2-Acyl Imidazoles with Allenes

2017-11-17T10:00:53.05055-05:00

A highly regio-, diastereo- and enantioselective addition of 2-acyl imidazoles or 2-acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described. This atom economic approach leads to the formation of the branched allylic alkylated products including acyclic quaternary all-carbon stereogenic centres in good yields with good to excellent diastereo- and enantioselectivities. Kinetic studies reveal that the rate-determining step in this process is the oxidative addition of Rh(I) with C—H bond. A highly regio-, diastereo- and enantioselective addition of 2-acyl imidazoles or 2-acyl pyridines with allenes promoted by Rh/Lewis acid synergistically catalytic system is described which leads to the formation of the branched allylic alkylated products including acyclic quaternary all-carbon stereogenic centres in good yields with good to excellent diastereo- and enantioselectivities.



Organic Nanoprobes for Fluorescence and 19F Magnetic Resonance Dual-Modality Imaging

2017-11-17T10:00:36.832579-05:00

Multimodal imaging techniques have been demonstrated to be greatly advantageous in achieving accurate diagnosis and gained increasing attention in recent decades. Herein, we present a new strategy to integrate the complementary modalities of 19F magnetic resonance imaging (19F MRI) and fluorescence imaging (FI) into a polymer nanoprobe composed of hydrophobic fluorescent organic core and hydrophilic fluorinated polymer shell. The alkyne-terminated fluorinated copolymer (Pn) of 2,2,2-trifluoroethyl acrylate (TFEA) and poly(ethylene glycol) methyl ether acrylate (PEGA) was first prepared via atom transfer radical polymerization (ATRP). The PEGA plays an important role in both improving 19F signal and modulating the hydrophilicity of Pn. The alkynyl tail in Pn is readily conjugated with azide modified tetra-phenylethylene (TPE) through click chemistry to form azo polymer (TPE-azo-Pn). The core-shell nanoprobes (TPE-P3N) with an average particle size of 57.2 ± 8.8 nm are obtained via self-assembly with ultrasonication in aqueous solution. These nanoprobes demonstrate high water stability, good biocompatibility, strong fluorescence and good 19F MRI performance, which present great potentials for simultaneous fluorescence imaging and 19F–MR imaging. A polymeric nanocomposite probe for simultaneous fluorescence and 19F magnetic resonance dual-modality imaging has been fabricated by means of integrating the hydrophobic fluorescence organic core with the hydrophilic fluorinated copolymer shell, which demonstrates high water stability, good biocompatibility, strong fluorescence and excellent 19F MRI performance.



Morphology-controlled Electrodeposition of Copper Nanospheres onto FTO for Enhanced Photocatalytic Hydrogen Production

2017-11-23T03:46:19.132651-05:00

Using CuSO4 as the copper source, nanostructured copper with four different morphologies was obtained by electrodeposition method on FTO substrates. The as-synthesized Cu/FTO samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), Raman, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The effects of electrodeposition potential and electrodeposition time on the Cu/FTO samples and the photocatalytic performance were investigated systematically. The results showed that the Cu/FTO samples were well-crystallized and the morphologies could be changed from nanoslices to nanodendrites structure with the negative shift of the depositing potential. The electrodeposition potential and time have a significant effect on the amount of H2 evolution. The obtained Cu nanospheres which were prepared at the potential of −0.65 V for 600 s showed the best photocatalytic behavior. The mechanisms for the photocatalytic activities were also discussed. This manuscript describes a new kind of photocatalyst Cu/FTO prepared by electrodeposition method. The morphology of Cu on FTO can be nanoparticle, nanoslices or nanodendrites which varied with the depositing potential. Cu/FTO presented stable photocatalytic H2 evolution ability. Electrodeposition potential and time have a significant effect on the amount of H2 evolution.



Enhanced Electrocatalytic Activity of Dual Template Based Pt/Cu-zeolite A/Graphene for Methanol Electrooxidation

2017-11-23T03:46:22.236342-05:00

A novel Pt/Cu-zeolite A/graphene based electrocatalyst was successfully prepared by chemical reduction method for methanol electrooxidation. Graphite oxide and Cu functionalized zeolite A were simultaneously reduced by NaBH4 to prepare Cu-zeolite A/graphene support which was used to deposit Pt nanoparticles. The nanostructure and composition of as-prepared Pt/Cu-zeolite A/graphene composites were characterized by X-ray diffractometer, X-ray fluorescence, Fourier transform infrared spectrometer and scanning electron microscopy. The electrocatalytic properties of Pt/Cu-zeolite A/graphene modified electrode for methanol oxidation were investigated by cyclic voltammetry and chronoamperometry in 0.10 mol/L H2SO4 + 0.50 mol/L CH3OH solution. Compared with Pt/zeolite A/graphene electrode and Pt/graphene electrode, Pt/Cu-zeolite A/graphene based electrode exhibited obviously enhanced current and higher electrocatalytic activity for methanol electrooxidation. The increased electrocatalytic activity was attributed to the presence of zeolite A and reduced graphene oxide based dual template, which significantly increased the effective electrode surface and facilitated the diffusion of analytes into the electroactive catalyst. A novel Pt/Cu-zeolite A/graphene based electrocatalyst was successfully prepared by chemical reduction method for methanol electrooxidation. The upper and lower left are SEMs of Cu-ZEA, RGO and Pt/Cu-ZEA/RGO, respectively. The lower right is CVs of Pt/RGO/GCE (a), Pt/ZEA/RGO (b) and Pt/Cu-ZEA/RGO/GCE (c) at 0.5 V in 0.10 mol/L H2SO4 + 0.50 mol/L CH3OH solution.



Fluorescence Responses of the Protonation and Deprotonation Processes between Phenolate and Phenol within Rosamine

2017-11-23T03:46:45.893145-05:00

Two rosamine-based pH probes 1a and 1b with pyronine-phenol skeleton were designed and synthesized by a simple one-step reaction. pH titration experiments showed that probes 1a and 1b exhibit near OFF–ON fluorescence responses around 550–750 nm towards the hydrogen ions. The pKa of the probe 1a is 8.29, while that of the probe 1b increases to 12.1 because of the hydrogen bond inside it. Selective and competitive experiments indicated that both common ions and amino acids did not interfere their emission with hydrogen ions. Moreover, confocal fluorescent imaging showed that the probe 1a could be served as mitochondria biomarker in HeLa and Ges-1 cells. Two rosamine-based pH probes 1a and 1b exhibit near OFF–ON fluorescence responses around 550–750 nm towards the hydrogen ions. Protonation and deprotonation processes between phenolate and phenol within rosamine were evaluated. The pKa of the probe 1a is 8.29, while that of the probe 1b increases to 12.1 because of the hydrogen bond inside it. And probe 1a was found to be a mitochondria biomarker for HeLa and Ges-1 cells.



Copper Catalyzed Asymmetric [4 + 2] Annulations of D-A Cyclobutanes with Aldehydes

2017-11-23T03:46:57.872232-05:00

Copper catalyzed enantioselective [4 + 2] annulations of D-A cyclobutanes and aldehydes have been developed. In the presence of a side arm modified chiral bisoxazoline (SaBOX) ligand, the [4 + 2] annulations proceeded smoothly with a broad substrate scope. 22 examples were studied, leading to the corresponding products with various functional groups in 41%–99% yields with >99/1 dr and 90%–96% ee. The resulting product with two ester groups was mono-reduced, giving the corresponding product in excellent diastereoselectivity without loss of the enantiopurity. Copper catalyzed enantioselective [4 + 2] annulations of D-A cyclobutanes and aldehydes have been developed, leading to the corresponding products with various functional groups in 41%–99% yields with >99/1 dr and 90%–96% ee.



Layer-by-Layer Approach to Superhydrophobic Zeolite Antireflective Coatings

2017-11-23T03:46:37.222532-05:00

Antireflection surfaces and coatings have attracted considerable interests because they can maximize light transmittance of the substrates. In this work, zeolite antireflective (ZAR) coatings are prepared via layer-by-layer (LBL) assembly of MFI-type zeolite silicalite-1 and polyelectrolyte. A micro- and macroporous hierarchical structure was obtained which contributes to the antireflective property of the zeolite coatings. The light transmittance of the coating on quartz can achieve as high as 99.3% at 650 nm. Furthermore, a superhydrophobic ZAR coating can be obtained by chemical modification with 1H,1H,2H,2H–perfluorooctyl-triethoxysilane. This work demonstrates that zeolites are excellent candidates as high transparent superhydrophobic coatings. Zeolite antireflective (ZAR) coatings have been successfully prepared by LBL assembly method with silicalite-1 nano-crystals and polyelectrolyte, followed by calcination to eliminate the organic component. A superhydrophobic ZAR coating can be obtained by chemical modification. The present work demonstrates that zeolites are excellent materials for highly transparent superhydrophobic coatings.



Ligand-Controlled Copper-Catalyzed Highly Regioselective Difluoromethylation of Allylic Chlorides/Bromides and Propargyl Bromides

2017-11-27T06:10:58.430705-05:00

Highly regiodivergent copper-catalyzed allylic/propargylic difluoromethylation reactions by employing different ligands are described. When 5,6-dimethyl-1,10-phenanthroline was used as the ligand, exclusively α-difluoromethylated products were obtained, while γ-selective difluoromethylated products were generated when N-heterocyclic carbene-SIPr was used as the ligand. Likewise, high α- vs. γ-selectivities were achieved in the presence of similar copper catalysts for the reactions of propargyl bromides. Moreover, a copper-catalyzed asymmetric allylic difluoromethylation reaction with moderate to good enantioselectivity by the use of chiral ligands was developed. Highly regiodivergent copper-catalyzed allylic/propargylic difluoromethylation reactions by employing different ligands are described. When 5,6-dimethyl-1,10-phenanthroline was used as the ligand, exclusively α-difluoromethylated products were obtained, while γ-selective difluoromethylated products were generated when N-heterocyclic carbene-SIPr was used as the ligand. Likewise, high α- vs. γ-selectivities were achieved in the presence of similar copper catalysts for the reactions of propargyl bromides.



pH-Responsive Host−Guest Complexation between a Water-soluble Pillar[7]Arene and a 2,7-Diazapyrenium Salt and Its Application in Controllable Self-assembly

2017-11-27T06:06:47.288519-05:00

A novel host−guest recognition motif based on a water-soluble pillar[7]arene (WP7) and a 2,7-diazapyrenium salt (DMDAP) was prepared. According to the integrated results of 1H NMR, 2D NOESY, UV–vis spectroscopy and fluorescence titration experiments, we demonstrated that the molecular recognition of WP7 to DMDAP in water not only has high association constant but also has pH-responsiveness. Subsequently, we took advantage of this molecular recognition motif to fabricate a supra-amphiphile based on WP7 and an amphiphilic 2,7-diazapyrenium derivative DAPAC. Its controllable self-assembly in water was also investigated by means of TEM and DLS techniques. The host−guest complexation between a water-soluble pillar[7]arene and a 2,7-diazapyrenium salt was studied. Based on this novel recognition motif, a pH-responsive supra-amphiphile was successfully fabricated. Its controllable self-assembly in water was also investigated.



Lanthanide Inorganic Solids Based on Main Group Borates and Oxyanions of Lone Pair Cations

2017-12-15T08:22:27.18622-05:00

Lanthanide borates containing post transition metal main group elements, including Ga(III), Ge(IV), Sb(V) and Te(VI), as well as lanthanide salts of the oxyanions of lone pair cations, such as I(V), Se(IV) and Te(IV), were reviewed. The post transition metal main group elements in lanthanide borates adopt octahedral or tetrahedral geometry only. In the structure of lanthanide galloborates, only octahedral GaO6 was found while both octahedral GeO6 and tetrahedral GeO4 appeared in borogermanates. The fifth period elements Sb(V) and Te(VI) prefer octahedral coordination geometry in lanthanide borates system. The second groups introduced to lanthanide oxyanions of lone pairs are mainly focused on d0 TM units, such as WO4 tetrahedron, VO5 square pyramid or MoO6 octahedron, and rigid tetrahedral groups like sulfate SO4, silica SiO4 or selenate SeO4 units. Divalent cations like Pb(II) and magnetic ions of Cu(II) or Mn(II) were also included. The structure chemistry of lanthanide ions in these systems is rich. Coordination numbers from six to ten are discovered, yielding a wide range of coordination geometries including the pentagonal bipyramid, square antiprism, metabidiminished icosahedron, tricapped trigonal prism, capped triangular cupola, etc. The connectivity modes between the Ln polyhedra are miscellaneous, from 3D network, to 2D layer, 1D chain, tetramer, trimer, dimer and finally monomer. A number of compounds display NCS structures and strong SHG response, and many lanthanide compounds exhibit good luminescent properties in visible and IR region. Lanthanide borates containing Ga(III), Ge(IV), Sb(V) or Te(VI), and lanthanide oxyanions of lone pair cations, such as I(V), Se(IV) and Te(IV), were reviewed. The connectivity style of the Ln polyhedra is miscellaneous. Compounds with multifunction, such as magnetic, photoluminescent and SHG properties, were found in these systems.



Meeting Our New Associate Editors

2017-12-15T08:22:27.306904-05:00