ChemDigest – Basic bits and bolts of chemistry

Green synthesis and investigation of antioxidant ability new pyrazines containing pyrrolo[2,1‐a]isoquinolines derivatives

Par admin / 13 août 2020 13 août 2020 / heterocycles

Abstract

In this study, a new, easy and high yield procedure is investigated for the generation of pyrazine containing pyrrolo[2,1‐a]isoquinoline derivatives using multicomponent reaction of phthalaldehyde or its derivatives, primary amines, α‐haloalketones, electron deficient acetylenic compounds, ammonium acetate and KF/Clinoptilolite nanoparticles (KF/CP NPs) as catalyst in water at room temperature. The reactions of 2‐hydroxy phthalaldehyde, primary amines, α‐haloketones, electron deficient acetylenic compounds, and ammonium acetate in the presence of KF/CP NPs as catalyst in water at room temperature produce pyrazine derivatives in good yields. Also, in this work, antioxidant ability was studied for a number of prepared compounds employing the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging and power of compounds for reducing of ferric ion experiments and evaluating results with synthetic antioxidants (TBHQ and BHT). Comfortable, simple, fast and fresh procedure is the advantages of this study.

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Carrier‐Induced Modification of Palladium Nanoparticles on Porous Boron Nitride for Alkyne Semi‐Hydrogenation

Par David B / 13 août 2020 13 août 2020 / Non classé

Defects in porous boron nitride enable the incorporation of boron atoms to the lattice of supported palladium nanoparticles, creating spatially isolated ensembles of metallic character. Evaluation in the continuous semi‐hydrogenation of 1‐hexyne demonstrates that the modification induced by the carrier can yield unparalleled performance compared to state‐of‐the‐catalysts without the need for introducing further additives.

Abstract

Chemical modifiers enhance the efficiency of metal catalysts in numerous applications, but their introduction often involves toxic or expensive precursors and complicates the synthesis. Here, we show that a porous boron nitride carrier can directly modify supported palladium nanoparticles, originating unparalleled performance in the continuous semi‐hydrogenation of alkynes. Analysis of the impact of various structural parameters reveals that using a defective high surface area boron nitride and ensuring a palladium particle size of 4–5 nm is critical for maximizing the specific rate. The combined experimental and theoretical analyses point towards boron incorporation from defects in the support to the palladium subsurface, creating the desired isolated ensembles determining the selectivity. This practical approach highlights the unexplored potential of using tailored carriers for catalyst design.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Simon Büchele, Zupeng Chen, Edvin Fako, Frank Krumeich, Roland Hauert, Olga V. Safonova, Núria López, Sharon Mitchell, Javier Pérez‐Ramírez
doi.org/10.1002/anie.202005842

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Micro‐Lensed Fiber Laser Desorption Mass Spectrometry Imaging Reveals Subcellular Distribution of Drugs within Single Cells

Par David B / 13 août 2020 13 août 2020 / Non classé

A nanoscale resolution mass spectrometry imaging technique using micro‐lensed fiber as a laser desorption ion source is proposed. Combining this system with a time‐of‐flight mass spectrometer, we achieved the visualization of drug distribution inside a single cell at the resolution of 300 nm.

Abstract

The visualization of temporal and spatial changes in the intracellular environment has great significance for chemistry and bioscience research. Mass spectrometry imaging (MSI) plays an important role because of its unique advantages, such as being label‐free and high throughput, yet it is a challenge for laser‐based techniques due to limited lateral resolution. Here, we develop a simple, reliable, and economic nanoscale MSI approach by introducing desorption laser with a micro‐lensed fiber. Using this integrated platform, we achieved 300 nm resolution MSI and successfully visualized the distribution of various small‐molecule drugs in subcellular locations. Exhaustive dynamic processes of anticancer drugs, including releasing from nanoparticle carriers entering nucleus of cells, can be readily acquired on an organelle scale. Considering the simplicity and universality of this nanoscale desorption device, it could be easily adapted to most of laser‐based mass spectrometry applications.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yifan Meng, Xiaoling Cheng, Tongtong Wang, Wei Hang, Xiaoping Li, Wan Nie, Rong Liu, Zheng Lin, Le Hang, Zhibin Yin, Baolin Zhang, Xiaomei Yan
doi.org/10.1002/anie.202002151

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Naphthalene‐Diimide‐Based Ionenes as Universal Interlayers for Efficient Organic Solar Cells

Par David B / 13 août 2020 13 août 2020 / Non classé

Electronically active ionenes were realized by integration of naphthalene diimide into a polymer backbone. These conductive polymers have a low degree of crystalline order, show a great processing advantage to remove energy barriers between organic semiconductors and metal electrodes, and afford fullerene‐based, non‐fullerene‐based, as well as ternary organic solar cells with high performance and a maximum efficiency of 16.9 %.

Abstract

Self‐doping ionene polymers were efficiently synthesized by reacting functional naphthalene diimide (NDI) with 1,3‐dibromopropane (NDI‐NI) or trans‐1,4‐dibromo‐2‐butene (NDI‐CI) via quaternization polymerization. These NDI‐based ionene polymers are universal interlayers with random molecular orientation, boosting the efficiencies of fullerene‐based, non‐fullerene‐based, and ternary organic solar cells (OSCs) over a wide range of interlayer thicknesses, with a maximum efficiency of 16.9 %. NDI‐NI showed a higher interfacial dipole (Δ), conductivity, and electron mobility than NDI‐CI, affording solar cells with higher efficiencies. These polymers proved to efficiently lower the work function (WF) of air‐stable metals and optimize the contact between metal electrode and organic semiconductor, highlighting their power to overcome energy barriers of electron injection and extraction processes for efficient organic electronics.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Ming Liu, Pu Fan, Qin Hu, Thomas P. Russell, Yao Liu
doi.org/10.1002/anie.202004432

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Mechanistic Insights into C(sp2)−C(sp)N Reductive Elimination from Gold(III) Cyanide Complexes

Par David B / 13 août 2020 13 août 2020 / Non classé

A detailed mechanistic study on the C(sp²)−C(sp)N reductive elimination from gold(III) complexes is reported herein. The kinetic and computational data from a new family of well‐defined phosphine‐ligated dicyanoarylgold(III) complexes unravel a novel asynchronous concerted reductive elimination process operating in these transformations.

Abstract

A new family of phosphine‐ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary ^12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp²)−C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp³)−C(sp³), C(sp²)−C(sp²), and C(sp³)−C(sp²) bond formation processes taking place on gold(III) species.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Alexandre Genoux, Jorge A. González, Estíbaliz Merino, Cristina Nevado
doi.org/10.1002/anie.202005731

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Polymer Transformers: Interdigitating Reaction Networks of Fueled Monomer Species to Reconfigure Functional Polymer States

Par David B / 13 août 2020 13 août 2020 / Non classé

A strategy, called polymer transformers, is developed to adaptively reconfigure functional polymer states with the possibility for rejuvenation and reconfiguration into different outputs in new cycles. This is achieved by interdigitating two ATP‐powered enzymatic reaction networks of dynamically polymerizing monomer mixtures into a joint system.

Abstract

Adaptivity is an essential trait of life. One type of adaptivity is the reconfiguration of a functional system states by correlating sensory inputs. We report polymer transformers, which can adaptively reconfigure their composition from a state of a mixed copolymer to being enriched in either monomer A or B. This is achieved by embedding and hierarchically interconnecting two chemically fueled activation/deactivation enzymatic reaction networks for both monomers via a joint activation pathway (network level) and an AB linker monomer reactive to both A and B (species level). The ratio of enzymes governing the individual deactivation pathways (our external signals) control the enrichment behavior in the dynamic state. The method shows high programmability of the reconfigured state, rejuvenation of transformation cycles, and quick in situ adaptation. As a proof‐of‐concept, we showcase this dynamic reconfiguration for colloidal surface functionalities.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Mo Sun, Jie Deng, Andreas Walther
doi.org/10.1002/anie.202006526

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Making and Breaking Leupeptin Protease Inhibitors in Pathogenic Gammaproteobacteria

Par David B / 13 août 2020 13 août 2020 / Non classé

Leupeptin, a broad‐spectrum protease inhibitor, is used worldwide in protein isolation and has been established as a chemical model in autophagy and immunoproteasome research. The leupeptin pathway was identified in gammaproteobacterial pathogens and associated with animal colonization phenotypes. A new type of protease transforms the leupeptins into novel heterotricyclic “pro‐pyrazinones.”

Abstract

Leupeptin is a bacterial small molecule that is used worldwide as a protease inhibitor. However, its biosynthesis and genetic distribution remain unknown. We identified a family of leupeptins in gammaproteobacterial pathogens, including Photorhabdus, Xenorhabdus, and Klebsiella species, amongst others. Through genetic, metabolomic, and heterologous expression analyses, we established their construction by discretely expressed ligases and accessory enzymes. In Photorhabdus species, a hypothetical protein required for colonizing nematode hosts was established as a new class of proteases. This enzyme cleaved the tripeptide aldehyde protease inhibitors, leading to the formation of “pro‐pyrazinones” featuring a hetero‐tricyclic architecture. In Klebsiella oxytoca, the pathway was enriched in clinical isolates associated with respiratory tract infections. Thus, the bacterial production and proteolytic degradation of leupeptins can be associated with animal colonization phenotypes.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jhe‐Hao Li, Joonseok Oh, Sabine Kienesberger, Nam Yoon Kim, David J. Clarke, Ellen L. Zechner, Jason M. Crawford
doi.org/10.1002/anie.202005506

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Photo‐excited Oxygen Reduction and Oxygen Evolution Reactions Enable a High‐Performance Zn–Air Battery

Par David B / 13 août 2020 13 août 2020 / Non classé

A novel Zn–air battery with two semiconducting PDTB and TiO₂ cathodes sandwiching a Zn anode was constructed. The battery is enabled by photo‐excited ORR and OER in the discharging and charging processes, respectively. The resultant discharge voltage of 1.90 V is much higher than the charge voltage of 0.59 V because of the contribution of photo‐energy.

Abstract

The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn–air battery is constructed with two cathodes of poly(1,4‐di(2‐thienyl))benzene (PDTB) and TiO₂ grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO₂ cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record‐high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo‐involved Zn–air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo‐energy utilization in rechargeable batteries.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Dongfeng Du, Shuo Zhao, Zhuo Zhu, Fujun Li, Jun Chen
doi.org/10.1002/anie.202005929

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Light Dynamics of the Retinal‐Disease‐Relevant G90D Bovine Rhodopsin Mutant

Par David B / 13 août 2020 13 août 2020 / Non classé

Rhodopsin is the major dim light receptor in vertebrate eyes. Numerous mutations associated with impaired visual cycles are known. The G90D mutation leads to a constitutively active mutant form of rhodopsin that causes congenital stationary night blindness (CSNB). We investigated the consequences of this mutation on the visual cycle, both in terms of structural aspects and dynamic changes.

Abstract

The RHO gene encodes the G‐protein‐coupled receptor (GPCR) rhodopsin. Numerous mutations associated with impaired visual cycle have been reported; the G90D mutation leads to a constitutively active mutant form of rhodopsin that causes CSNB disease. We report on the structural investigation of the retinal configuration and conformation in the binding pocket in the dark and light‐activated state by solution and MAS‐NMR spectroscopy. We found two long‐lived dark states for the G90D mutant with the 11‐cis retinal bound as Schiff base in both populations. The second minor population in the dark state is attributed to a slight shift in conformation of the covalently bound 11‐cis retinal caused by the mutation‐induced distortion on the salt bridge formation in the binding pocket. Time‐resolved UV/Vis spectroscopy was used to monitor the functional dynamics of the G90D mutant rhodopsin for all relevant time scales of the photocycle. The G90D mutant retains its conformational heterogeneity during the photocycle.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Nina Kubatova, Jiafei Mao, Carl Elias Eckert, Krishna Saxena, Santosh L. Gande, Josef Wachtveitl, Clemens Glaubitz, Harald Schwalbe
doi.org/10.1002/anie.202003671

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Cryogenic OrbiSIMS Localizes Semi‐Volatile Molecules in Biological Tissues

Par David B / 13 août 2020 13 août 2020 / Non classé

Cryogenic OrbiSIMS decreases molecular fragmentation and expands the chemical space that is amenable to mass spectrometry imaging with high spatial and mass resolution. Semi‐volatile and non‐volatile molecules can now be imaged simultaneously in biological tissues.

Abstract

OrbiSIMS is a recently developed instrument for label‐free imaging of chemicals with micron spatial resolution and high mass resolution. We report a cryogenic workflow for OrbiSIMS (Cryo‐OrbiSIMS) that improves chemical detection of lipids and other biomolecules in tissues. Cryo‐OrbiSIMS boosts ionization yield and decreases ion‐beam induced fragmentation, greatly improving the detection of biomolecules such as triacylglycerides. It also increases chemical coverage to include molecules with intermediate or high vapor pressures, such as free fatty acids and semi‐volatile organic compounds (SVOCs). We find that Cryo‐OrbiSIMS reveals the hitherto unknown localization patterns of SVOCs with high spatial and chemical resolution in diverse plant, animal, and human tissues. We also show that Cryo‐OrbiSIMS can be combined with genetic analysis to identify enzymes regulating SVOC metabolism. Cryo‐OrbiSIMS is applicable to high resolution imaging of a wide variety of non‐volatile and semi‐volatile molecules across many areas of biomedicine.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Clare L. Newell, Jean‐Luc Vorng, James I. MacRae, Ian S. Gilmore, Alex P. Gould
doi.org/10.1002/anie.202006881

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Palladium‐Catalyzed Chlorocarbonylation of Aryl (Pseudo)Halides Through In Situ Generation of Carbon Monoxide

Par David B / 13 août 2020 13 août 2020 / Non classé

Abstract

An efficient palladium‐catalyzed chlorocarbonylation of aryl (pseudo)halides that gives access to a wide range of carboxylic acid derivatives has been developed. The use of butyryl chloride as a combined CO and Cl source eludes the need for toxic, gaseous carbon monoxide, thus facilitating the synthesis of high‐value products from readily available aryl (pseudo)halides. The combination of palladium(0), Xantphos, and an amine base is essential to promote this broadly applicable catalytic reaction. Overall, this reaction provides access to a great variety of carbonyl‐containing products through in situ transformation of the generated aroyl chloride. Combined experimental and computational studies support a reaction mechanism involving in situ generation of CO.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Philip Boehm, Sven Roediger, Alessandro Bismuto, Bill Morandi
doi.org/10.1002/anie.202005891

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Nucleic Acid Aptamers for Molecular Diagnostics and Therapeutics: Advances and Perspectives

Par David B / 13 août 2020 13 août 2020 / Non classé

Advantages of aptamers and SELEX in diverse research fields are summarized in this Minireview, along with some limitations and possible solutions to them. Furthermore described are future perspectives for aptamer modification with a near‐infinite number of molecular‐modulating elements that will result in more powerful tools in bioscience.

Abstract

The advent of SELEX (systematic evolution of ligands by exponential enrichment) technology has shown the ability to evolve artificial ligands with affinity and specificity able to meet growing clinical demand for probes that can, for example, distinguish between the target leukemia cells and other cancer cells within the matrix of heterogeneity, which characterizes cancer cells. Though antibodies are the conventional and ideal choice as a molecular recognition tool for many applications, aptamers complement the use of antibodies due to many unique advantages, such as small size, low cost, and facile chemical modification. This Minireview will focus on the novel applications of aptamers and SELEX, as well as opportunities to develop molecular tools able to meet future clinical needs in biomedicine.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Long Li, Shujuan Xu, He Yan, Xiaowei Li, Hoda Safari Yazd, Xiang Li, Tong Huang, Cheng Cui, Jianhui Jiang, Weihong Tan
doi.org/10.1002/anie.202003563

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Revealing the A‐Site Effect of Lead‐Free A3Sb2Br9 Perovskite in Photocatalytic C(sp3)−H Bond Activation

Par David B / 13 août 2020 13 août 2020 / Non classé

A₃Sb₂Br₉ nanoparticles (NPs) with different ratios of Cs and CH₃NH₃ (MA) were employed in photocatalytic C(sp³)−H bond activation with high conversion rates. It was demonstrated that the octahedron distortion by A‐site cations could affect the electronic properties of A₃Sb₂Br₉ and further influence the photocatalytic activities.

Abstract

The lead‐free halide perovskite A₃Sb₂Br₉ is utilized as a photocatalyst for the first time for C(sp³)−H bond activation. A₃Sb₂Br₉ nanoparticles (A₃Sb₂Br₉ NPs) with different ratios of Cs and CH₃NH₃ (MA) show different photocatalytic activities for toluene oxidation and the photocatalytic performance is enhanced when increasing the amount of Cs. The octahedron distortion caused by A‐site cations can change the electronic properties of X‐site ions and further affect the electron transfer from toluene molecules to Br sites. After the regulation of A‐site cations, the photocatalytic activity is higher with A₃Sb₂Br₉ NPs than that with classic photocatalysts (TiO₂, WO₃, and CdS). The main active species involved in photocatalytic oxidation of toluene are photogenerated holes (h⁺) and superoxide anions (^.O₂⁻). The octahedron distortion by A‐site cations affecting photocatalytic activity remains unique and is also a step forward for understanding more about halide‐perovskite‐based photocatalysis. The relationship between octahedron distortion and photocatalysis can also guide the design of new photocatalytic systems involving other halide perovskites.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zhenzhen Zhang, Yuying Yang, Yingying Wang, Lanlan Yang, Qi Li, Langxing Chen, Dongsheng Xu
doi.org/10.1002/anie.202005495

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Access to Vinyl Ethers and Ketones with Hypervalent Iodine Reagents as Oxy‐Allyl Cation Synthetic Equivalents

Par David B / 13 août 2020 13 août 2020 / Non classé

Access to oxy‐allyl cation equivalents from alkynes by hypervalent iodine reagents is described. The stereoselective transformation of Vinylbenziodoxolones (VBXs) provides aryl enol ethers bearing an allylic ether or ester group and corresponds to an Umpolung of the nucleophilic reactivity of enol ethers. The obtained products are easily transformed into α‐difunctionalized ketones under oxidative conditions.

Abstract

We report an Umpolung strategy of enol ethers to generate oxy‐allyl cation equivalents based on the use of hypervalent iodine reagents. Under mild basic conditions, the addition of nucleophiles to aryloxy‐substituted vinylbenziodoxolone (VBX) reagents, easily available in two steps from silyl alkynes, resulted in the stereoselective formation of substituted aryl enol ethers. The reaction was most efficient with phenols as nucleophiles, but preliminary results were also achieved for C‐ and N‐ nucleophiles. In absence of external nucleophiles, the 2‐iodobenzoate group of the reagent was transferred. The obtained aryl enol ethers could then be transformed into α‐difunctionalized ketones by oxidation. The described “allyl cation”‐like reactivity contrast with the well‐established “vinyl‐cation” behavior of alkenyl iodonium salts.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Nina Declas, Jerome Waser
doi.org/10.1002/anie.202006707

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Synthetic Macrocycle‐Based Nonporous Adaptive Crystals for Molecular Separation

Par David B / 13 août 2020 13 août 2020 / Non classé

This Minireview describes the recent advances of synthetic macrocycle‐based nonporous adaptive crystals for molecular separation and vapochromic application.

Abstract

The exploitation of new materials for adsorptive separation of industrially important hydrocarbons is of great importance in both scientific research and petrochemical industry. Nonporous adaptive crystals (NACs) as a robust class of synthetic materials have drawn much attention during the past five years for their superior performance in adsorption and separation. Pillararenes are the main family of macrocyclic arenes used for NACs construction, where the structure–function relationship has been intensively studied. In the past two years, some emerging types of synthetic macrocyclic arenes have been successfully brought into this research field, showing the gradual enrichment and diversification of NACs materials. This Minireview summarizes the recent advances of synthetic macrocycle‐based NACs, which are categorized by various practical applications in molecular separation. Besides, NACs‐based vapochromic supramolecular systems are also discussed. Finally, future perspectives and challenges of NACs are given. We envisage that this Minireview will be a useful and timely reference for those who are interested in new molecular and supramolecular crystals for storage and separation applications.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jia‐Rui Wu, Ying‐Wei Yang
doi.org/10.1002/anie.202006999

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Formyl MIDA Boronate: C1 Building Block Enables Straightforward Access to α‐Functionalized Organoboron Derivatives

Par David B / 13 août 2020 13 août 2020 / Non classé

One‐pot preparation and chemical reactions of formyl MIDA boronate are described in this work. New types of α‐functionalized organoboron compounds, including boron‐substituted analogues of ynones and β‐dicarbonyl compounds, are synthesized. The method demonstrates high tolerance to diverse functional moieties, making formyl MIDA boronate a valuable C₁ building block for extending the scope of organoboron chemistry.

Abstract

Formyl MIDA boronate has been known to be an elusive type of acylboronate that has not been obtained to date. In this work, an approach to the one‐pot preparation and chemical transformations of formyl MIDA boronate were developed to provide new types of α‐functionalized organoboron compounds. Among them are acylboronate reagents which present boron‐substituted analogues of ynones and β‐dicarbonyl compounds. The developed synthetic procedures, utilizing formyl MIDA boronate, are tolerant to diverse functional groups, making this reagent an advantageous C₁ building block for extending the scope of organoboron chemistry.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yevhen M. Ivon, Ivan V. Mazurenko, Yuliya O. Kuchkovska, Zoya V. Voitenko, Oleksandr O. Grygorenko
doi.org/10.1002/anie.202007651

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Carrier‐Free Delivery of Precise Drug–Chemogene Conjugates for Synergistic Treatment of Drug‐Resistant Cancer

Par David B / 13 août 2020 13 août 2020 / Non classé

A carrier‐free drug delivery system is assembled using an amphiphilic drug–chemogene conjugate, which is prepared by conjugating two paclitaxel (PTX) molecules with an floxuridine‐integrated antisense oligonucleotide against P‐glycoprotein (termed chemogene) using a fluorescent dibromomaleimide linker. The PTX–chemogene assembly can effectively reverse drug resistance and inhibit tumor growth.

Abstract

Combinatorial antitumor therapies using different combinations of drugs and genes are emerging as promising ways to overcome drug resistance, which is a major cause for the failure of cancer treatment. However, dramatic pharmacokinetic differences of drugs greatly impede their combined use in cancer therapy, raising the demand for drug delivery systems (DDSs) for tumor treatment. By employing fluorescent dithiomaleimide (DTM) as a linker, we conjugate two paclitaxel (PTX) molecules with a floxuridine (FdU)‐integrated antisense oligonucleotide (termed chemogene) to form a drug–chemogene conjugate. This PTX–chemogene conjugate can self‐assemble into a spherical nucleic acid (SNA)‐like micellular nanoparticle as a carrier‐free DDS, which knocks down the expression of P‐glycoprotein and subsequently releases FdU and PTX to exert a synergistic antitumor effect and greatly inhibit tumor growth.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Lijuan Zhu, Yuanyuan Guo, Qiuhui Qian, Deyue Yan, Yuehua Li, Xinyuan Zhu, Chuan Zhang
doi.org/10.1002/anie.202006895

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Templated‐Assembly of CsPbBr3 Perovskite Nanocrystals into 2D Photonic Supercrystals with Amplified Spontaneous Emission

Par David B / 13 août 2020 13 août 2020 / Non classé

Perovskite nanocrystals (NCs) are self‐assembled into 2D photonic supercrystals using pre‐patterned polydimethylsiloxane (PDMS) templates and their optical spectra are tunable by varying lattice spacing. These photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near‐IR region due to enhanced multi‐photon absorption caused by light trapping in the photonic crystal.

Abstract

Perovskite nanocrystals (NCs) have revolutionized optoelectronic devices because of their versatile optical properties. However, controlling and extending these functionalities often requires a light‐management strategy involving additional processing steps. Herein, we introduce a simple approach to shape perovskite nanocrystals (NC) into photonic architectures that provide light management by directly shaping the active material. Pre‐patterned polydimethylsiloxane (PDMS) templates are used for the template‐induced self‐assembly of 10 nm CsPbBr₃ perovskite NC colloids into large area (1 cm²) 2D photonic crystals with tunable lattice spacing, ranging from 400 nm up to several microns. The photonic crystal arrangement facilitates efficient light coupling to the nanocrystal layer, thereby increasing the electric field intensity within the perovskite film. As a result, CsPbBr₃ 2D photonic crystals show amplified spontaneous emission (ASE) under lower optical excitation fluences in the near‐IR, in contrast to equivalent flat NC films prepared using the same colloidal ink. This improvement is attributed to the enhanced multi‐photon absorption caused by light trapping in the photonic crystal.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: David Vila‐Liarte, Maximilian W. Feil, Aurora Manzi, Juan Luis Garcia‐Pomar, He Huang, Markus Döblinger, Luis M Liz‐Marzán, Jochen Feldmann, Lakshminarayana Polavarapu, Agustín Mihi
doi.org/10.1002/anie.202006152

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Exerting Spatial Control During Nanoparticle Occlusion within Calcite Crystals

Par David B / 13 août 2020 13 août 2020 / Non classé

Both surface chemistry and [Ca²⁺] concentration are shown to play critical roles in dictating the precise spatial occlusion of the guest nanoparticles within calcite crystals. This new insight enables the rational design of patterned nanocomposite crystals via a multi‐step occlusion strategy.

Abstract

In principle, nanoparticle occlusion within crystals provides a straightforward and efficient route to make new nanocomposite materials. However, developing a deeper understanding of the design rules underpinning this strategy is highly desirable. In particular, controlling the spatial distribution of the guest nanoparticles within the host crystalline matrix remains a formidable challenge. Herein, we show that the surface chemistry of the guest nanoparticles and the [Ca²⁺] concentration play critical roles in determining the precise spatial location of the nanoparticles within calcite crystals. Moreover, in situ studies provide important mechanistic insights regarding surface‐confined nanoparticle occlusion. Overall, this study not only provides useful guidelines for efficient nanoparticle occlusion, but also enables the rational design of patterned calcite crystals using model anionic block copolymer vesicles.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yin Ning, Yide Han, Lijuan Han, Matthew J. Derry, Steven P. Armes
doi.org/10.1002/anie.202007110

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Ultrafast Encapsulation of Metal Nanoclusters into MFI Zeolite in the Course of Its Crystallization: Catalytic Application for Propane Dehydrogenation

Par David B / 13 août 2020 13 août 2020 / Non classé

Overcoming the mismatch between the rapid formation of nanoclusters and the slow crystallization of zeolites allows the in situ encapsulation of metal nanoclusters into zeolites in just a few minutes. The resultant Pt/Sn‐ZSM‐5 shows excellent activity and stability in the dehydrogenation propane to propylene.

Abstract

Encapsulating metal nanoclusters into zeolites combines the superior catalytic activity of the nanoclusters with high stability and unique shape selectivity of the crystalline microporous materials. The preparation of such bifunctional catalysts, however, is often restricted by the mismatching in time scale between the fast formation of nanoclusters and the slow crystallization of zeolites. We herein demonstrate a novel strategy to overcome the mismatching issue, in which the crystallization of zeolites is expedited so as to synchronize it with the rapid formation of nanoclusters. The concept was demonstrated by confining Pt and Sn nanoclusters into a ZSM‐5 (MFI) zeolite in the course of its crystallization, leading to an ultrafast, in situ encapsulation within just 5 min. The Pt/Sn‐ZSM‐5 exhibited exceptional activity and selectivity with stability in the dehydrogenation of propane to propene. This method of ultrafast encapsulation opens up a new avenue for designing and synthesizing composite zeolitic materials with structural and compositional complexity.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jie Zhu, Ryota Osuga, Ryo Ishikawa, Naoya Shibata, Yuichi Ikuhara, Junko N. Kondo, Masaru Ogura, Jihong Yu, Toru Wakihara, Zhendong Liu, Tatsuya Okubo
doi.org/10.1002/anie.202007044

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Electroreduction of CO2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes

Par David B / 13 août 2020 13 août 2020 / Non classé

Molecular cobalt‐based CO₂ electroreduction catalysts achieved the conversion of CO₂ into HCOOH as the major product with very low overpotential by tuning the electronic properties of the metal centers using pyridine‐thiolate ligands. Formation of a stable carbonyl complex caused deactivation. The active catalyst is regenerate by re‐oxidation, promoting CO ligand release.

Abstract

Electrocatalytic CO₂ reduction to value‐added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine‐thiolate complexes as electrocatalysts for CO₂ reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2‐pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s⁻¹. Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Subal Dey, Tanya K. Todorova, Marc Fontecave, Victor Mougel
doi.org/10.1002/anie.202006269

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Methanol‐Assisted Autocatalysis in Catalytic Methanol Synthesis

Par David B / 13 août 2020 13 août 2020 / Non classé

It is shown that the methanol synthesis from syngas with the industrial Cu/ZnO/Al₂O₃ catalyst at commercially applied conditions is dominated by a methanol‐assisted autocatalytic reaction mechanism. Of the two main reaction products, H₂O is strongly inhibiting, whereas CH₃OH is beneficial to the reaction rate. Methanol is proposed to open up a faster pathway of surface formate conversion via methyl formate.

Abstract

Catalytic methanol synthesis is one of the major processes in the chemical industry and may grow in importance, as methanol produced from CO₂ and sustainably derived H₂ are envisioned to play an important role as energy carriers in a future low‐CO₂‐emission society. However, despite the widespread use, the reaction mechanism and the nature of the active sites are not fully understood. Here we report that methanol synthesis at commercially applied conditions using the industrial Cu/ZnO/Al₂O₃ catalyst is dominated by a methanol‐assisted autocatalytic reaction mechanism. We propose that the presence of methanol enables the hydrogenation of surface formate via methyl formate. Autocatalytic acceleration of the reaction is also observed for Cu supported on SiO₂ although with low absolute activity, but not for Cu/Al₂O₃ catalysts. The results illustrate an important example of autocatalysis in heterogeneous catalysis and pave the way for further understanding, improvements, and process optimization of industrial methanol synthesis.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Joachim Thrane, Sebastian Kuld, Niels D. Nielsen, Anker D. Jensen, Jens Sehested, Jakob M. Christensen
doi.org/10.1002/anie.202006921

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The Polarization Effect in Surface‐Plasmon‐Induced Photocatalysis on Au/TiO2 Nanoparticles

Par David B / 13 août 2020 13 août 2020 / Non classé

A polarization effect in charge separation and spatial distribution was discovered using photo‐irradiated Kelvin probe force microscopy. Plasmon‐induced surface photovoltage was demonstrated to be varied as a sine‐squared function of polarization angle. Under suitable polarization angle, local charge density and photocatalytic activity can be dramatically enhanced.

Abstract

Controlling the interaction of polarization light with an asymmetric nanostructure such as a metal/semiconductor heterostructure provides opportunities for tuning surface plasmon excitation and near‐field spatial distribution. However, light polarization effects on interfacial charge transport and the photocatalysis of plasmonic metal/semiconductor photocatalysts are unclear. Herein, we reveal the polarization dependence of plasmonic charge separation and spatial distribution in Au/TiO₂ nanoparticles under 45° incident light illumination at the single‐particle level using a combination of photon‐irradiated Kelvin probe force microscopy (KPFM) and electromagnetic field simulation. We quantitatively uncover the relationship between the local charge density and polarization angle by investigating the polarization‐dependent surface photovoltage (SPV). The plasmon‐induced photocatalytic activity is enhanced when the polarization direction is perpendicular to the Au/TiO₂ interface.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yuying Gao, Wei Nie, Qianhong Zhu, Xun Wang, Shengyang Wang, Fengtao Fan, Can Li
doi.org/10.1002/anie.202007706

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Non‐Interpenetrated Single‐Crystal Covalent Organic Frameworks

Par David B / 13 août 2020 13 août 2020 / Non classé

A 3D single‐crystal COF with a non‐interpenetrated structure was constructed for the first time. The highly open framework provides a unique matrix‐isolation platform to investigate the intrinsic dynamics of individual AIE moiety.

Abstract

Growth of covalent organic frameworks (COFs) as single crystals is extremely challenging. Inaccessibility of open‐structured single‐crystal COFs prevents the exploration of structure‐oriented applications. Herein we report for the first time a non‐interpenetrated single‐crystal COF, LZU‐306, which possesses the open structure constructed exclusively via covalent assembly. With a high void volume of 80 %, LZU‐306 was applied to investigate the intrinsic dynamics of reticulated tetraphenylethylene (TPE) as the individual aggregation‐induced‐emission moiety. Solid‐state ²H NMR investigation has determined that the rotation of benzene rings in TPE, being the freest among the reported cases, is as fast as 1.0×10⁴ Hz at 203 K to 1.5×10⁷ Hz at 293 K. This research not only explores a new paradigm for single‐crystal growth of open frameworks, but also provides a unique matrix‐isolation platform to reticulate functional moieties into a well‐defined and isolated state.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Lin Liang, Yi Qiu, Wei David Wang, Jing Han, Yi Luo, Wei Yu, Guan‐Lin Yin, Zhi‐Peng Wang, Lei Zhang, Jianwei Ni, Jing Niu, Junliang Sun, Tianqiong Ma, Wei Wang
doi.org/10.1002/anie.202007230

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Heterogeneous Electrofreezing of Super‐Cooled Water on Surfaces of Pyroelectric Crystals is Triggered by Planar‐Trigonal Ions

Par David B / 13 août 2020 13 août 2020 / Non classé

Electrofreezing experiments of super‐cooled water with different ions were performed on the charged hemihedral faces of pyroelectric LiTaO₃ and AgI crystals. In their Communication (DOI: doi.org/10.1002/anie.20200643510.1002/anie.202006435), D. Harries, M. Lahav, I. Lubomirsky et al. demonstrate that HCO₃⁻ ions elevate the icing temperature near the positively charged faces, whereas H₃O⁺ slightly reduces the icing temperature.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Sofia Curland, Christoph Allolio, Leah Javitt, Shiri Dishon, Isabelle Weissbuch, David Ehre, Daniel Harries, Meir Lahav, Igor Lubomirsky
doi.org/10.1002/anie.202010813

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