ChemDigest – Basic bits and bolts of chemistry

The Synthetic Potential of Thiophenium Ylide Cycloadducts

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Alkynyl sulfides were shown to participate in thermal (3+2) cycloadditions with tethered alkynes. The resulting thiophenium ylide cycloadducts led to a variety of polysubstituted thiophenes by trapping with diverse electrophiles.

Abstract

(3+2) cycloaddition reactions are undeniably one of the most robust and versatile synthetic tools in heterocyclic chemistry. The classically required 1,3-dipoles are however limited to three-atom sequences bearing stabilized formal charges in their Lewis structure. The scope of three-atom groupings possible in (3+2) cycloadditions can be greatly expanded by taking of advantage neutral three-atom components (TACs). These groupings result in zwitterionic (3+2) cycloadducts adaptable to multiple outcomes depending on structure and conditions. Herein, the intramolecular (3+2) cycloaddition reaction between alkynyl sulfides (neutral TAC) and alkynes to provide key thiophenium ylide intermediates is first reported. These reactive species provide access to highly substituted fused thiophenes following predictable chemical sequences. Structural features on the obtained thiophenes were highly configurable by judicious choice of both alkynyl sulfide substitution and reaction conditions.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Alice Pommainville, Dominic Campeau, Fabien Gagosz
onlinelibrary.wiley.com/doi/10.1002/anie.202205963

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Evolution and Single‐Droplet Analysis of Fuel‐Driven Compartments by Droplet‐Based Microfluidics

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Droplet-based microfluidics were used to encapsulate a fuel-driven cycle that drives phase separation into coacervate-based droplets. This approach enables the analysis of every coacervate-based droplet in the reaction container throughout its lifetime. The nucleation, growth, and dissolution of active coacervate-based droplets were investigated with this setup.

Abstract

Active droplets are a great model for membraneless organelles. However, the analysis of these systems remains challenging and is often limited due to the short timescales of their kinetics. We used droplet-based microfluidics to encapsulate a fuel-driven cycle that drives phase separation into coacervate-based droplets to overcome this challenge. This approach enables the analysis of every coacervate-based droplet in the reaction container throughout its lifetime. We discovered that the fuel concentration dictates the formation of the coacervate-based droplets and their properties. We observed that coacervate-based droplets grow through fusion, decay simultaneously independent of their volume, and shrinkage rate scales with their initial volume. This method helps to further understand the regulation of membraneless organelles, and we believe the analysis of individual coacervate-based droplets enables future selection- or evolution-based studies.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Alexander M. Bergmann, Carsten Donau, Fabian Späth, Kevin Jahnke, Kerstin Göpfrich, Job Boekhoven
onlinelibrary.wiley.com/doi/10.1002/anie.202203928

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High‐Temperature and Dynamic RGB (Red‐Green‐Blue) Long‐Persistent Luminescence in an Anti‐Kasha Organic Compound

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A novel organic ultra-long persistence luminescent material with dynamic RGB-tunable and high-temperature long-persistent luminescence (LPL) based on a triamino-s-triazine derivative was designed and prepared for information encryption and decryption.

Abstract

Organic LPL (long-persistent luminescence) materials have sparked extensive research interest due to the ultralong-lived triplet states. Although numerous organic LPL materials have been reported, most of the triplet emission was static and monotonous. Therefore, LPL materials with dynamic triplet emission are urgently required. A triamino-s-triazine derivative 1 with dynamic LPL was fabricated. The single-crystal structure shows that the abundant intermolecular interactions and small free volume restrict the molecular motion and avoid the quenchers. Spectral and theoretical calculations upheld the existence of multiple excited states in 1, and the migration of electrons between multiple excited states is very sensitive to external stimuli. By modulating the stimulus, the residence of electrons in different triplet states can be manipulated to achieve RGB LPL. Importantly, blue LPL was achieved by manipulating the anti-Kasha emission. And the red LPL can still be observed at high temperature.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Qiang‐Sheng Zhang, Shi‐Cheng Wang, Xiao‐Hong Xiong, Peng‐Yan Fu, Xiao‐Dong Zhang, Ya‐Nan Fan, Mei Pan
onlinelibrary.wiley.com/doi/10.1002/anie.202205556

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Selective Oxidative Coupling of Methane to Ethylene in a Solid Oxide Electrolyser Based on Porous Single‐Crystalline CeO2 Monoliths

Par admin / 25 juin 2022 25 juin 2022 / Non classé

The selective conversion of CH₄ to C₂H₄ at the anode and the electrolysis of CO₂ to CO at the cathode in a solid oxide electrolyser is presented. Well-defined interfaces were constructed that function as three-phase boundaries by exsolving single-crystalline Ni nanoparticles in porous single-crystalline CeO₂ monoliths.

Abstract

Catalytic conversion of CH₄ to C₂H₄ plays an important role in the light olefin industry. Here, we report the electrochemical conversion of CH₄ to C₂H₄/C₂H₆ at the anode with the electrolysis of CO₂ to CO at the cathode in a solid oxide electrolyser. We constructed well-defined interfaces that function as three-phase boundaries by exsolving single-crystalline Ni nanoparticles in porous single-crystalline CeO₂ monoliths. We engineered the chemical states and flux of active oxygen species for the oxidation of CH₄ at the anode by controlling voltage and temperature. We show the unprecedented C₂ selectivity (C₂H₄ and C₂H₆) of ≥99.5 % at a CH₄ conversion of ≈7 %. The electrolyser exhibits excellent durability without performance degradation being observed in a continuous operation of 100 hours. Our work enables a novel path for the selective conversion of CH₄/CO₂ into useful chemicals, and the technique of building well-defined interfaces may find potential applications in other fields.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Lingting Ye, Zhibo Shang, Kui Xie
onlinelibrary.wiley.com/doi/10.1002/anie.202207211

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Fast Magic‐Angle‐Spinning NMR Reveals the Evasive Hepatitis B Virus Capsid C‐Terminal Domain

Par admin / 25 juin 2022 25 juin 2022 / Non classé

The combination of proton-detected fast MAS NMR >100 kHz and specific labelling schemes reveals the formerly invisible domain of the Hepatitis B virus capsid. Since the evasiveness of this domain lies in its dynamic behavior, it is expected that this methodology will be of use to characterize flexible domains in a wider range of proteins.

Abstract

Experimentally determined protein structures often feature missing domains. One example is the C-terminal domain (CTD) of the hepatitis B virus capsid protein, a functionally central part of this assembly, crucial in regulating nucleic-acid interactions, cellular trafficking, nuclear import, particle assembly and maturation. However, its structure remained elusive to all current techniques, including NMR. Here we show that the recently developed proton-detected fast magic-angle-spinning solid-state NMR at >100 kHz MAS allows one to detect this domain and unveil its structural and dynamic behavior. We describe the experimental framework used and compare the domain’s behavior in different capsid states. The developed approaches extend solid-state NMR observations to residues characterized by large-amplitude motion on the microsecond timescale, and shall allow one to shed light on other flexible protein domains still lacking their structural and dynamic characterization.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Morgane Callon, Alexander A. Malär, Lauriane Lecoq, Marie Dujardin, Marie‐Laure Fogeron, Shishan Wang, Maarten Schledorn, Thomas Bauer, Michael Nassal, Anja Böckmann, Beat H. Meier
onlinelibrary.wiley.com/doi/10.1002/anie.202201083

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Water‐Soluble Melanin–Protein–Fe/Cu Conjugates Derived from Norepinephrine as Reliable Models for Neuromelanin of Human Brain Locus Coeruleus

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Melanin–protein conjugates derived from norepinephrine fibrillar β-lactoglobulin were synthesized as soluble models of neuromelanin from human brain locus coeruleus. This pigment contains a significant amount of iron and copper. The synthetic models show that the two metals exhibit a strong tendency to remain coupled to each other in dinuclear or multinuclear aggregates.

Abstract

Water-soluble melanin-protein-Fe/Cu conjugates derived from norepinephrine and fibrillar β-lactoglobulin are reliable models for neuromelanin (NM) of human brain locus coeruleus. Both iron and copper promote catecholamine oxidation and exhibit strong tendency to remain coupled in oligonuclear aggregates. The Fe-Cu clusters are EPR silent and affect the ¹H NMR spectra of the conjugates through a specific sequence of signals. Derivatives containing only Fe or Cu exhibit different NMR patterns. The EPR spectra show weak signals of paramagnetic Fe^III in conjugates containing Fe or mixed Fe-Cu sites due to small amounts of mononuclear centers. The latter derivatives exhibit EPR signals for isolated Cu^II centers. These features parallel the EPR behavior of NM from locus coeruleus. The spectral data indicate that Fe^III is bound to the melanic fraction, whereas Cu^II is bound on the protein fibrils, suggesting that the Fe-Cu clusters occur at the interface between the two components of the synthetic NMs.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Andrea Capucciati, Enrico Monzani, Michela Sturini, Stefania Nicolis, Fabio A. Zucca, Luigi Bubacco, Marco Bortolus, Luigi Zecca, Luigi Casella
onlinelibrary.wiley.com/doi/10.1002/anie.202204787

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N‐CF3 Imidazolidin‐2‐one Derivatives via Photocatalytic and Silver‐Catalyzed Cyclizations

Par admin / 25 juin 2022 25 juin 2022 / Non classé

The reported methodologies open access to the mono-substituted N-CF₃ imidazolidin-2-ones at the 4-position which was previously inaccessible. Directly from the linear N-CF₃ ureas bearing an alkene moiety, N-CF₃ imidazolidin-2-ones were prepared via Ag-catalysis and light assisted proton coupled electron transfer. Instead of prior modification of the alkene moiety, tandem PCET and Nickel catalysis were shown to increase the diversity of the core. The cyclic compounds were then treated under various conditions to modify the core structure to introduce structural complexity.

Abstract

While the N-trifluoromethylation of cyclic ureas is of interest for the potential to fundamentally change the properties of these biologically relevant moieties, the single synthetic procedure known to date describing their access only gives 4,4-disubstituted or fused aromatic cyclic N-CF₃ urea derivatives. We herein report an alternative approach to unleash access to the 4-monosubstituted imidazolidinone motif. The strategy relies on straightforward cyclization of readily accessible acyclic ureas, enabled by Ag-catalysis or light-assisted proton coupled electron transfer. The cyclic core is shown to be highly robust and amenable to various derivatizations, such as tandem Ni-catalysis, C−B, C−N, C−C cross couplings or C−H functionalizations, tolerating basic, nucleophilic and/or oxidizing conditions.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Abdurrahman Turksoy, Samir Bouayad‐Gervais, Franziska Schoenebeck
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201435

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Tuning Deazaflavins Towards Highly Potent Reducing Photocatalysts Guided by Mechanistic Understanding – Enhancement of the Key Step by the Internal Heavy Atom Effect

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Inspired by nature and based on mechanistic understanding, we designed deazaflavins (dFl) with reducing powers comparable to Li which function via the consecutive photo-induced electron transfer (conPET) mechanism independently on molecular oxygen. The internal heavy atom effect (IHAE) by introducing bromine into the photocatalyst enhances considerably the key triplet pathway via a triplet-born radical pair. Furthermore, an optimal concentration of the sacrificial electron donor (S_sac) is required for bypassing the unproductive reaction via the singlet-born radical pair.

Abstract

Deazaflavins are well suited for reductive chemistry acting via a consecutive photo-induced electron transfer, in which their triplet state and semiquinone – the latter is formed from the former after electron transfer from a sacrificial electron donor – are key intermediates. Guided by mechanistic investigations aiming to increase intersystem crossing by the internal heavy atom effect and optimising the concentration conditions to avoid unproductive excited singlet reactions, we synthesised 5-aryldeazaflavins with Br or Cl substituents on different structural positions via a three-component reaction. Bromination of the deazaisoalloxazine core leads to almost 100 % triplet yield but causes photo-instability and enhances unproductive side reactions. Bromine on the 5-phenyl group in ortho position does not affect the photostability, increases the triplet yield, and allows its efficient usage in the photocatalytic dehalogenation of bromo- and chloroarenes with electron-donating methoxy and alkyl groups even under aerobic conditions. Reductive powers comparable to lithium are achieved.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Tetiana Pavlovska, David Král Lesný, Eva Svobodová, Irena Hoskovcová, Nataliya Archipowa, Roger Jan Kutta, Radek Cibulka
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202200768

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1,5‐Allyl Shift by a Sequential Achmatowicz/Oxonia‐Cope/Retro‐Achmatowicz Rearrangement

Par admin / 25 juin 2022 25 juin 2022 / Non classé

An unexpected 1,5-allyl shift is discovered for allyl furfuryl alcohol through two-step sequential ring expansion/contraction rearrangement at room temperature, which could be considered as a Woodward–Hoffmann-forbidden formal [3,5]-sigmatropic rearrangement. Mechanistically, it involves Achmatowicz rearrangement, oxonia-Cope rearrangement, and an unprecedented “retro-Achmatowicz” rearrangement.

Abstract

1,3-Allyl and 1,2-allyl shifts through [3,3]- and [2,3]-sigmatropic rearrangements are well-established and widely used in organic synthesis. In contrast, 1,5-allyl shift through related [3,5]-sigmatropic rearrangement is unknown because [3,5]-sigmatropic rearrangement is thermally Woodward–Hoffmann forbidden. Herein, we report an unexpected discovery of a formal 1,5-allyl shift of allyl furfuryl alcohol through a 2-step sequential rearrangement. Mechanistically, this formal 1,5-allyl shift is achieved through a sequential ring expansion/contraction rearrangement: 1) Achmatowicz rearrangement (ring expansion), and 2) cascade oxonia-Cope rearrangement/retro-Achmatowicz rearrangement (ring contraction). This new 1,5-allyl shift method is demonstrated with >20 examples and expected to find applications in organic synthesis and materials chemistry.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Xiayan Y. Zhang, Yi Tong, Gang Li, Hao Zhao, Guanye Chen, Hongliang Yao, Rongbiao Tong
onlinelibrary.wiley.com/doi/10.1002/anie.202205919

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Graphene‐Based Nanomaterials for Solar‐Driven Overall Water Splitting

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Graphene has attracted great attention in solar-driven overall water splitting because of its versatile properties. This review discussed the roles of graphene played in two solar-to-hydrogen energy conversion techniques – photocatalysis and photoelectrochemical water splitting. The challenges and prospects of the future applications of graphene-based nanomaterials in solar-driven water splitting are highlighted.

Abstract

Water splitting through photocatalysis and photoelectrochemical methods is a promising strategy for solar energy utilization. Graphene is widely used in solar-driven overall water splitting because of its versatile properties. This review summarizes the preparation of graphene-based photocatalysts and photoelectrodes and the functions of graphene, and highlights the challenges and prospects of the future applications of graphene in solar-driven water splitting.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jingyi Lin, Hui Pan, Zhixin Chen, Lianzhou Wang, Yao Li, Shenmin Zhu
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202200722

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Synthesis and Visualization of Entangled 3D Covalent Organic Frameworks with High‐Valency Stereoscopic Molecular Nodes for Gas Separation

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A new high-valency quadrangular prism (D_4h) stereoscopic molecular node is used synthesize two isoreticular 3D covalent organic frameworks (COFs). Low-dose electron microscopy unravels their 2-fold interpenetrating networks with a bcu topology. The unique pore architectures and strong binding sites enable excellent performance in separating C₂H₂/CO₂ and C₂H₂/CH₄ gas pairs. The high-valency molecular node may lead to new 3D COF topologies.

Abstract

The structural diversity of three-dimensional (3D) covalent organic frameworks (COFs) are limited as there are only a few choices of building units with multiple symmetrically distributed connection sites. To date, 4 and 6-connected stereoscopic nodes with T_d, D_3h, D_3d and C₃ symmetries have been mostly reported, delivering limited 3D topologies. We propose an efficient approach to expand the 3D COF repertoire by introducing a high-valency quadrangular prism (D_4h) stereoscopic node with a connectivity of eight, based on which two isoreticular 3D imine-linked COFs can be created. Low-dose electron microscopy allows the direct visualization of their 2-fold interpenetrated bcu networks. These 3D COFs are endowed with unique pore architectures and strong molecular binding sites, and exhibit excellent performance in separating C₂H₂/CO₂ and C₂H₂/CH₄ gas pairs. The introduction of high-valency stereoscopic nodes would lead to an outburst of new topologies for 3D COFs.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Chengtao Gong, Hao Wang, Guan Sheng, Xiaokang Wang, Xiaoqiu Xu, Jian Wang, Xiaohe Miao, Yikuan Liu, Yinling Zhang, Fangna Dai, Liangjun Chen, Nanjun Li, Guodong Xu, Jianhong Jia, Yihan Zhu, Yongwu Peng
onlinelibrary.wiley.com/doi/10.1002/anie.202204899

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Chemical Tools for the Temporal Control of Water Solution pH and Applications in Dissipative Systems

Par admin / 25 juin 2022 25 juin 2022 / Non classé

The chemical reagents and methodologies (tools) employed for accurately and precisely programming over time the pH of a water solution are described in detail. For each tool, a number of selected examples is reported in order to show its feasibility and usefulness

Abstract

The chemical reagents used to achieve a predictable and programmable time control of the pH of water solutions are reviewed with the purpose to present a toolbox of instruments to be used when a precise pH vs time profile is needed. These tools are particularly useful in view of the growing interest on dissipative systems, many of which operate in water solutions, under the action of reagents (chemical fuels) that allow for programmed pH evolution. After a brief introduction describing the importance of such tools for the operation of dissipative systems in water, five sections follow, which illustrate the different method used so far to temporally control the pH of a water solution. In particular, time-programmable pH variations based on: 1) bubbling of gases (CO₂, N₂, Air), 2) hydrolysis of esters, lactones and sultones, 3) enzymatic and biocatalytic networks, 4) decarboxylation reaction of activated carboxylic acids, and 5) pH-oscillators are described together with selected examples of application.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Daniele Del Giudice, Federico Frateloreto, Carla Sappino, Stefano Di Stefano
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202200407

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Optimizing Pt Electronic States through Formation of a Schottky Junction on Non‐reducible Metal–Organic Frameworks for Enhanced Photocatalysis

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Platinum nanoparticles are supported on different MOFs, including non-reducible ZIF-8 and reducible UiO-66 and MIL-125. Unexpectedly, the Pt/ZIF-8 exhibits higher activity than Pt/UiO-66 and Pt/MIL-125 in the photocatalytic benzylamine oxidative coupling reaction. The different electron transfer behaviors among these photocatalysts lead to the highest Pt electron density on ZIF-8 toward O₂ activation, accounting for its superior activity.

Abstract

Charge transfer between metal sites and supports is crucial for catalysis. Redox-inert supports are usually unfavorable due to their less electronic interaction with metal sites, which, we demonstrate, is not always correct. Herein, three metal–organic frameworks (MOFs) are chosen to mimic inert or active supports for Pt nanoparticles (NPs) and the photocatalysis is studied. Results demonstrate the formation of a Schottky junction between Pt and the MOFs, leading to the electron-donation effect of the MOFs. Under light irradiation, both the MOF electron-donation effect and Pt interband excitation dominate the Pt electron density. Compared with the “active” UiO-66 and MIL-125 supports, Pt NPs on the “inert” ZIF-8 exhibit higher electron density due to the higher Schottky barrier, resulting in superior photocatalytic activity. This work optimizes metal catalysts with non-reducible supports, and promotes the understanding of the relationship between the metal–support interaction and photocatalysis.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zi‐Xuan Sun, Kang Sun, Ming‐Liang Gao, Önder Metin, Hai‐Long Jiang
onlinelibrary.wiley.com/doi/10.1002/anie.202206108

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Visible Light‐Mediated Metal‐Free Chlorodifluoromethylation of Arenes and Heteroarenes by a Hypervalent Iodine EDA Complex

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A visible light-mediated electron donor–acceptor complex enabling direct chlorodifluoromethylation of (hetero)arenes is described. This method provides the privileged moiety with mild conditions across a broad range of functional groups and bioactive scaffolds. Post-functionalization reactions and key control experiments are reported as well. The core EDA complex is studied spectroscopically, enabling further synthetic applications in the future.

Abstract

A novel EDA complex comprised of a bis(chlorodifluoroacetoxy)iodoarene and 1,3,5-trimethoxybenzene is described, which enables the direct radical C(sp²)−H chlorodifluoromethylation of arenes and heteroarenes under monochromatic visible-light irradiation. The procedure is mild, operationally simple, and utilizes commercially available reagents. The developed conditions demonstrate compatibility with a host of commonly encountered functionalities and biologically relevant scaffolds, whilst showcasing the post-functionalization capabilities of the −CF₂Cl moiety. Various mechanistic studies were performed to explore the EDA complex and radical generation pathway.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Daniel Lin, Vinayak Krishnamurti, G. K. Surya Prakash
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202200607

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An endo‐Directing‐Group Strategy Unlocks Enantioselective (3+1+2) Carbonylative Cycloadditions of Aminocyclopropanes

Par admin / 25 juin 2022 25 juin 2022 / Non classé

An endo-directing group strategy enables enantioselective (3+1+2) cycloadditions that are triggered by carbonylative C−C bond activation of cyclopropanes. These processes are rare examples of cycloadditions where C−C bond oxidative addition is enantiodetermining.

Abstract

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Olga O. Sokolova, John F. Bower
onlinelibrary.wiley.com/doi/10.1002/anie.202205007

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Modulated Synthesis of Self‐Standing Covalent Organic Framework Films

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A modulated strategy was developed for the synthesis of self-standing COF films with good crystallinity and tunable thickness. As compared with the non-modulated method, the modulated approach changes the COF morphology from nanoparticles to nanofibers, enabling the facile preparation of self-standing COF films with improved mechanical properties. The Young’s modulus of the self-standing COF film obtained via the modulated strategy could increase by 26 times.

Abstract

The weak interaction of covalent organic framework (COF) nanoparticles makes the preparation of self-standing COF films difficult. Herein, a modulated strategy for the facile synthesis of self-standing COF films with good crystallinity and tunable thickness is reported. As compared with the non-modulated approach, the modulated strategy changes the COF morphology from nanoparticles to nanofibers, enabling the facile preparation of self-standing COF films with improved mechanical properties. The Young’s modulus of the self-standing COF film obtained via the modulated strategy could increase by 26 times. Moreover, self-standing LZU-8 film can be used as a membrane for efficient removal of 99 % mercury ions from aqueous solution. Our results open up a new approach to prepare self-standing COF thin films for practical applications.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yang Wang, Bei Guo, Tong Yang, Zhi‐Cong Zhang, Lin Liang, San‐Yuan Ding, Wei Wang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202200961

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A Highly Water‐ and Air‐Stable Iron‐Containing MRI Contrast Agent Sensor for H2O2

Par admin / 25 juin 2022 25 juin 2022 / Non classé

An Fe(II) complex with the macrocyclic quinol-containing ligand H₄qp4 displays high water- and air-stability. The complex rapidly reacts with H₂O₂, but not O₂, to yield Fe(III) complexes with oxidized ligands that contain para-quinone groups. Upon oxidation by H₂O₂, the r₁ increases by over four-fold, enabling the Fe(II) complex to act as an MRI contrast agent sensor for this reactive oxygen species.

Abstract

A highly water- and air-stable Fe(II) complex with the quinol-containing macrocyclic ligand H₄qp4 reacts with H₂O₂ to yield Fe(III) complexes with less highly chelating forms of the ligand that have either one or two para-quinones. The reaction increases the T₁-weighted relaxivity over four-fold, enabling the complex to detect H₂O₂ using clinical MRI technology. The iron-containing sensor differs from its recently characterized manganese analog, which also detects H₂O₂, in that it is the oxidation of the metal center, rather than the ligand, that primarily enhances the relaxivity.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Sana Karbalaei, Alicja Franke, Aubree Jordan, Cayla Rose, P. Raj Pokkuluri, Ronald J. Beyers, Achim Zahl, Ivana Ivanović‐Burmazović, Christian R. Goldsmith
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202201179

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Enantioselective Hydroxylation of Dihydrosilanes to Si‐Chiral Silanols Catalyzed by In Situ Generated Copper(II) Species

Par admin / 25 juin 2022 25 juin 2022 / Non classé

Copper(II)-mediated σ-metathesis with prochiral dihydrosilanes has been successfully leveraged to efficiently synthesize Si-chiral silanols as well as many other related Si-chiral skeletons. The reaction hinges on the continuous generation of catalytically active copper(II) species via single-electron transfer oxidation of copper(I) by alkyl halides and the efficient stereocontrol with multidentate anionic N,N,P-ligands.

Abstract

Catalytic enantioselective hydroxylation of prochiral dihydrosilanes with water is expected to be a highly efficient way to access Si-chiral silanols, yet has remained unknown up to date. Herein, we describe a strategy for realizing this reaction: using an alkyl bromide as a single-electron transfer (SET) oxidant for invoking Cu^II species and chiral multidentate anionic N,N,P-ligands for effective enantiocontrol. The reaction readily provides a broad range of Si-chiral silanols with high enantioselectivity and excellent functional group compatibility. In addition, we manifest the synthetic potential by establishing two synthetic schemes for transforming the obtained products into Si-chiral compounds with high structural diversity. Our preliminary mechanistic studies support a mechanism involving SET for recruiting chiral Cu^II species as the active catalyst and its subsequent σ-metathesis with dihydrosilanes.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Wu Yang, Lin Liu, Jiandong Guo, Shou‐Guo Wang, Jia‐Yong Zhang, Li‐Wen Fan, Yu Tian, Li‐Lei Wang, Cheng Luan, Zhong‐Liang Li, Chuan He, Xiaotai Wang, Qiang‐Shuai Gu, Xin‐Yuan Liu
onlinelibrary.wiley.com/doi/10.1002/anie.202205743

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Functionalizable and Chemically Recyclable Thermoplastics from Chemoselective Ring‐Opening Polymerization of Bio‐renewable Bifunctional α‐Methylene‐δ‐valerolactone

Par admin / 25 juin 2022 25 juin 2022 / Non classé

The controlled ring-opening polymerization (ROP) of α-methylene-δ-valerolactone (MVL) to produce functionalizable P(MVL)_ROP is presented. It can recycle back to pristine monomer with an almost quantitative yield (ca. 96 %). P(MVL)_ROP with high molar mass behaves as a tough thermoplastic with good mechanical properties, which is comparable to isotactic polypropylene (PP) and low-density polyethylene (LDPE).

Abstract

It is a highly attractive strategy to develop chemically recyclable polymers to establish a circular plastic economy. Despite the recent advancements, chemically recyclable polymers still face challenges including high energy cost for polymer preparation or recycling, poor monomer recovery selectivity and efficiency as well as undesired material performance. In this contribution, we present the chemoselective controlled ring-opening polymerization of bio-renewable bifunctional α-methylene-δ-valerolactone (MVL) to produce exclusive functionalizable polyester using strong base/urea binary catalysts. The obtained polyester with high molar mass exhibits good tensile strength comparable to that of some commodity plastics. Remarkably, the obtained polyester can be depolymerized to recover pristine monomer with a 96 % yield by thermolysis, thus successfully establishing a closed-loop life cycle.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jiandong Li, Fusheng Liu, Yalei Liu, Yong Shen, Zhibo Li
onlinelibrary.wiley.com/doi/10.1002/anie.202207105

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Solar‐Driven Overproduction of Biofuels in Microorganisms

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A hybrid photo-biosynthesis system was constructed for the overproduction of jet fuel farnesene by interfacing engineered E. coli with persistent phosphor mesoporous Al₂O₃ (meso-Al₂O₃). meso-Al₂O₃ with rich defects prolonged the lifetime of photo-excited electrons that were passed to E. coli and improved the farnesene production by a factor of over 100 %.

Abstract

Microbial cell factories reinvigorate current industries by producing complex fine chemicals at low costs. Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is the main reducing power to drive the biosynthetic pathways in microorganisms. However, insufficient intrinsic NADPH limits the productivity of microorganisms. Here, we report that supplying microorganisms with long-lived electrons from persistent phosphor mesoporous Al₂O₃ (meso-Al₂O₃) can elevate the NADPH level to facilitate efficient fine chemical production. The defects in meso-Al₂O₃ were demonstrated to be highly efficient in prolonging electrons’ lifetime. The long-lived electrons in meso-Al₂O₃ can pass the material–microorganism interface and power the biosynthetic pathways of E. coli to produce jet fuel farnesene. This work represents a reliable strategy to design photo-biosynthesis systems to improve the productivity of microorganisms with solar energy.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jie Wang, Na Chen, Guangkai Bian, Xin Mu, Na Du, Wenjie Wang, Chong‐Geng Ma, Shai Fu, Bolong Huang, Tiangang Liu, Yanbing Yang, Quan Yuan
onlinelibrary.wiley.com/doi/10.1002/anie.202207132

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Liam J. Donnelly

Par admin / 25 juin 2022 25 juin 2022 / Non classé

“Modern science needs to focus on placing sustainability at the heart of research … A key experience in my career was an internship at Merck where I had my first taste of research …” Find out more about Liam Donnelly in his Introducing … Profile.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors:
onlinelibrary.wiley.com/doi/10.1002/anie.202207896

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A Lattice‐Matching Strategy for Highly Reversible Copper‐Metal Anodes in Aqueous Batteries

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A lattice-matching strategy was developed to design high-performance Cu-metal anodes. Benefiting from the high lattice matching between Cu anodes and Ni substrates, Ni substrate-supported Cu anodes exhibit superior deposition/striping reversibility, lower nucleation overpotential and uniform deposition on the Ni substrates in comparison with other typical substrates.

Abstract

Copper metal is an attractive anode material for aqueous rechargeable batteries due to its high theoretical specific capacity (844 mAh g⁻¹), good environmental compatibility and high earth abundance. However, the Cu anodes often suffer from poor deposition/stripping reversibility and nonuniform deposition during the charge/discharge process, degrading the lifetime of aqueous Cu-metal batteries. Herein, a lattice-matching strategy was developed to design high-performance Cu-metal anodes. In such a strategy, Ni substrates that exhibit high lattice matching with Cu were selected to support the Cu anodes. The high lattice matching endows Cu anodes with high deposition/stripping reversibility, low nucleation overpotential as well as a uniform and dense electrodeposition on Ni substrates. Based on the Ni substrate-supported Cu anodes, the full cells paired with lead dioxide cathodes show a stable cycling behavior. This work provides a route for the design of high-performance Cu electrodes in aqueous rechargeable batteries.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Haixia Cai, Songshan Bi, Rui Wang, Lili Liu, Zhiqiang Niu
onlinelibrary.wiley.com/doi/10.1002/anie.202205472

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The Microscopic Diamond Anvil Cell: Stabilization of Superhard, Superconducting Carbon Allotropes at Ambient Pressure

Par admin / 25 juin 2022 25 juin 2022 / Non classé

DAC-carbon: A metallic, covalently bonded carbon allotrope is predicted via first principles calculations. The superhard sp³ carbon framework serves as a microscopic diamond anvil cell, in which the sp² chains are compressed to establish metallicity and superconductivity.

Abstract

A metallic, covalently bonded carbon allotrope is predicted via first principles calculations. It is composed of an sp³ carbon framework that acts as a diamond anvil cell by constraining the distance between parallel cis-polyacetylene chains. The distance between these sp² carbon atoms renders the phase metallic, and yields two well-nested nearly parallel bands that cross the Fermi level. Calculations show this phase is a conventional superconductor, with the motions of the sp² carbons being key contributors to the electron–phonon coupling. The sp³ carbon atoms impart superior mechanical properties, with a predicted Vickers hardness of 48 GPa. This phase, metastable at ambient conditions, could be made by on-surface polymerization of graphene nanoribbons, followed by pressurization of the resulting 2D sheets. A family of multifunctional materials with tunable superconducting and mechanical properties could be derived from this phase by varying the sp² versus sp³ carbon content, and by doping.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Xiaoyu Wang, Davide M. Proserpio, Corey Oses, Cormac Toher, Stefano Curtarolo, Eva Zurek
onlinelibrary.wiley.com/doi/10.1002/anie.202205129

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Relaxation of the Plant Cell Wall Barrier via Zwitterionic Liquid Pretreatment for Micelle‐Complex‐Mediated DNA Delivery to Specific Plant Organelles

Par admin / 25 juin 2022 25 juin 2022 / Non classé

A unique strategy to overcome the plant cell wall barrier for organelle-specific DNA delivery is presented. This strategy leverages the synergistic effects of a cell wall-loosening zwitterionic liquid and an organelle-targeting micelle complex, allowing greatly augmented DNA delivery to target organelles, such as chloroplasts, in living plants.

Abstract

Targeted delivery of genes to specific plant organelles is a key challenge for fundamental plant science, plant bioengineering, and agronomic applications. Nanoscale carriers have attracted interest as a promising tool for organelle-targeted DNA delivery in plants. However, nanocarrier-mediated DNA delivery in plants is severely hampered by the barrier of the plant cell wall, resulting in insufficient delivery efficiency. Herein, we propose a unique strategy that synergistically combines a cell wall-loosening zwitterionic liquid (ZIL) with a peptide-displaying micelle complex for organelle-specific DNA delivery in plants. We demonstrated that ZIL pretreatment can enhance cell wall permeability without cytotoxicity, allowing micelle complexes to translocate across the cell wall and carry DNA cargo into specific plant organelles, such as nuclei and chloroplasts, with significantly augmented efficiency. Our work offers a novel concept to overcome the plant cell wall barrier for nanocarrier-mediated cargo delivery to specific organelles in living plants.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Takaaki Miyamoto, Kousuke Tsuchiya, Kiminori Toyooka, Yumi Goto, Ayaka Tateishi, Keiji Numata
onlinelibrary.wiley.com/doi/10.1002/anie.202204234

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Humins‐Like Solid Support for Palladium Immobilization: Highly Efficient and Recyclable Catalyst for Cross‐Coupling Reactions

Par admin / 25 juin 2022 25 juin 2022 / Non classé

In the present work, we demonstrate the preparation of a novel bio-based polymeric material derived of 2,5-bis(hydroxymethyl)furan (DHMF) and maleic anhydride and its use as a solid support for metal immobilization, followed by its application as a reusable catalyst in cross-coupling reactions.

Abstract

In the present work, a new humins-like resin was prepared using 2,5-bis(hydroxymethyl)furan (DHMF) and maleic anhydride in 2 min at 110 °C. Such a new material was used as a solid support for palladium immobilization. For metal anchoring, encapsulation was the method of choice and palladium was encapsulated by in-situ polymerization. This resulting Pd@DHMF-based catalyst was characterized by solid-state ¹³C NMR, FT-IR, SEM, TGA, DSC, XRD, and XPS. To demonstrate proof of concept, Heck and Suzuki cross-coupling reactions were selected to evaluate the activity and reusability of the catalyst. Green solvents such as γ-valerolactone (GVL), Cyrene^TM and ethylene carbonate proved to be excellent reaction media for Heck coupling, whereas EtOH/H₂O was preferred for Suzuki coupling. Yields of up to 99 % were obtained in both cases. The recyclability of the Pd@DHMF-based catalyst was also demonstrated, 7 cycles have been achieved without loss of catalytic activity in both Heck and Suzuki reactions.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Renan S. Galaverna, Lucas P. Fernandes, Vitor H. Menezes da Silva, Abner Siervo, Julio C. Pastre
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202200376

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