Mois : septembre 2020

Total Synthesis of Kopsinitarine E

Total Synthesis of Kopsinitarine E

Kopsinitarine E, an indole alkaloid with a highly strained cage system, is synthesized for the first time in 20 steps. The fused‐ring system was efficiently installed by an unprecedented SmI2‐mediated Dieckmann‐like condensation, Prins‐type cyclization cascade, and subsequent semi‐pinacol rearrangement. Boc=tert‐butoxycarbonyl; TES=triethylsilyl.

Abstract

Kopsinitarines A–E are complex octacyclic caged Kopsia alkaloids with strained cage skeletons and a unique cyclic hemiaminal bridge that makes total synthesis challenging. Herein, we disclose the first total synthesis of kopsinitarine E. The key synthetic features include a SmI2‐mediated radical cascade cyclization and a subsequent semi‐pinacol rearrangement to install the key carbocyclic skeleton, a chemoselective hydrosilyl amide reduction to construct the hemiaminal ether bridge, and an intramolecular Mannich reaction to establish the highly strained cage system.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Karre Nagaraju, Dongshun Ni, Dawei Ma
doi.org/10.1002/anie.202011093

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Electron‐Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

Electron‐Deficient Imidazolium Substituted Cp Ligands and their Ru Complexes

Ligand design and application: The synthesis of electron‐poor imidazolium substituted Cp‐ylides is presented. Their electronic properties are elucidated based on NMR spectroscopy, DFT and reactivity studies. The first η5‐Cp coordination of electron‐poor cationic ylides is confirmed by X‐ray structure analyses and an equilibrium for the coordination of a Cp ligand is observed. Electrochemical investigations of the ligands and of the ruthenocenes quantify the decreasing donor properties with increasing number of imidazolium substituents.

Abstract

The synthesis of electron‐poor mono‐, di‐ and tri(imidazolium)‐substituted Cp‐ylides is presented and their electronic properties are discussed based on NMR spectroscopy, X‐ray structure analyses, electrochemical investigations and DFT calculations as well as by their reactivity toward [Ru(CH3CN)3Cp*](PF6). With mono‐ and di(imidazolium)‐substituted cyclopentadienides the respective monocationic and dicationic ruthenocences are formed (X‐ray), whereas tri(imidazolium) cyclopentadienides are too electron‐poor to form the ruthenocenes. Cyclic voltammetric analysis of the ruthenocenes shows reversible oxidation at a potential that increases with every additional electron‐withdrawing imidazolium substituent at the Cp ligand by 0.53–0.55 V in an electrolyte based on a weakly coordinating anion. A reversible oxidation can be observed for the free 1,3‐disubstituted ligand as well.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Fabio Mazzotta, Georg Zitzer, Bernd Speiser, Doris Kunz
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002801

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FeIII and FeII Phosphasalen Complexes: Synthesis, Characterization, and Catalytic Application for 2‐Naphthol Oxidative Coupling

FeIII and FeII Phosphasalen Complexes: Synthesis, Characterization, and Catalytic Application for 2‐Naphthol Oxidative Coupling

Phosphasalen iron(II) and iron(III) complexes, that differ from their salen analogues by the presence of a P=N linkage instead of imine in the ligand backbone, were synthesized and characterized in the solid state and in solution. The FeIII complexes were used to catalyze the oxidative coupling of 2‐naphthol using O2 from air as oxidant.

Abstract

We report on the synthesis and characterization of three iron(III) phosphasalen complexes, [FeIII(Psalen)(X)] differing in the nature of the counter‐anion/exogenous ligand (X=Cl, NO3, OTf), as well as the neutral iron(II) analogue, [FeII(Psalen)]. Phosphasalen (Psalen) differs from salen by the presence of iminophosphorane (P=N) functions in place of the imines. All the complexes were characterized by single‐crystal X‐ray diffraction, UV/Vis, EPR, and cyclic voltammetry. The [FeII(Psalen)] complex was shown to remain tetracoordinated even in coordinating solvent but surprisingly exhibits a magnetic moment in line with a FeII high‐spin ground state. For the FeIII complexes, the higher lability of triflate anion compared to nitrate was demonstrated. As they exhibit lower reduction potentials compared to their salen analogues, these complexes were tested for the coupling of 2‐naphthol using O2 from air as oxidant. In order to shed light on this reaction, the interaction between 2‐naphthol and the FeIII(Psalen) complexes was studied by cyclic voltammetry as well as UV/Vis spectroscopy.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Emmanuel Oheix, Christian Herrero, Jules Moutet, Jean‐Noël Rebilly, Marie Cordier, Régis Guillot, Sophie Bourcier, Frédéric Banse, Katell Sénéchal‐David, Audrey Auffrant
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001662

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Highlights on the Binding of Cobalta‐Bis‐(Dicarbollide) with Glucose Units

Highlights on the Binding of Cobalta‐Bis‐(Dicarbollide) with Glucose Units

Glued to glucose: The binding of the cobalta‐bis‐dicarbollide (COSAN) anion with carbohydrate moieties, which are important in a large range of biological functions in cells and tissues, is highlighted and described here. Adsorption of COSAN onto a sugar‐covered surface and co‐micellization with octyl‐glucoside were investigated at the molecular and supramolecular scales. The strong and non‐electrostatic COSAN‐C8G1 interactions arise from the hydrophobic and superchaotropic effects.

Abstract

Metalla‐bis‐dicarbollides, such as the cobalta‐bis‐dicarbollide (COSAN) anion [Co(C2B9H11)2], have attracted much attention in biology but a deep understanding of their interactions with cell components is still missing. For this purpose, we studied the interactions of COSAN with the glucose moiety, which is ubiquitous at biological interfaces. Octyl‐glucopyranoside surfactant (C8G1) was chosen as a model as it self‐assembles in water and creates a hydrated glucose‐covered interface. At low COSAN content and below the critical micellar concentration (CMC) of C8G1, COSAN binds to C8G1 monomers through the hydrophobic effect. Above the CMC of C8G1, COSAN adsorbs onto C8G1 micelles through the superchaotropic effect. At high COSAN concentrations, COSAN disrupts C8G1 micelles and the assemblies become similar to COSAN micelles but with a small amount of solubilized C8G1. Therefore, COSAN binds in a versatile way to C8G1 through either the hydrophobic or superchaotropic effect depending on their relative concentrations.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Tania Merhi, Alban Jonchère, Luc Girard, Olivier Diat, Miquel Nuez, Clara Viñas, Pierre Bauduin
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002123

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Separating Growth from Nucleation for Facile Control over the Size and Shape of Palladium Nanocrystals

Separating Growth from Nucleation for Facile Control over the Size and Shape of Palladium Nanocrystals

Taking shape: A one‐pot protocol that allows the separation of growth from nucleation and achieves better control over the size and shape of Pd nanocrystals is reported. The synthesis can also be scaled up by at least tenfold without compromising the quality.

Abstract

In order to maximize the performance of nanocrystals in a specific application, it is necessary to control both their size and shape. Here we report a one‐pot protocol that allows us to separate growth from nucleation for achieving better control over the size and shape of Pd nanocrystals. The two processes are temporally separated from each other, although the synthesis is carried out in the same reaction container. Size control is achieved by simply varying the ratio between the amounts of precursor allocated to the growth and nucleation processes. With the involvement of seeds at a fixed number, increasing the amount of precursor for growth leads to increasingly larger nanocrystals. Shape control is made possible by varying the capping agent, with bromide leading to a cubic shape and citrate inducing the formation of an octahedral shape. The synthesis can also be scaled up by at least tenfold without compromising the quality.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Annemieke Janssen, Yifeng Shi, Younan Xia
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001626

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Catalytic Light‐Triggered Reduction Promoted by a Dithienylethene Derivative

Catalytic Light‐Triggered Reduction Promoted by a Dithienylethene Derivative

A pyridinium‐substituted dithienylethene derivative was used for the first time as an efficient photoreducing agent of two different substrates. This reaction exhibits high catalytic yields due to the continuous regeneration of the initial state of the photochromic molecule.

Abstract

A pyridinium substituted dithienylethene derivative was used for the first time as an efficient photoreducing agent of two different substrates. This reaction exhibits high catalytic yields due to the continuous regeneration of the initial state of the photochromic molecule.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Amina Khettabi, Arkadiusz Grempka, Frederic Lafolet, Elarbi Chatir, Nicolas Leconte, Marie‐Noelle Collomb, Damien Jouvenot, Saioa Cobo
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.201905825

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Near‐Infrared (>1000 nm) Light‐Harvesters: Design, Synthesis and Applications

Near‐Infrared (>1000 nm) Light‐Harvesters: Design, Synthesis and Applications

Sun light is a part of the electromagnetic radiation given off by the sun. Organic molecules can absorb and emit light in different regions of solar radiation. Almost 50 % of solar energy lies in the IR region of solar radiation. Low band gap π‐conjugated materials can absorb NIR radiation. NIR absorbing molecules have potential application in biomedical and photoelectronic applications.

Abstract

Organic molecules can absorb or emit light in UV, visible and infra‐red (IR) region of solar radiation. Fifty percent of energy of solar radiation lies in the IR region of solar spectrum and extended π‐conjugated molecules containing low optical band gap can absorb NIR radiations. Recently IR molecules have grabbed the attention of synthetic chemists. Although only few molecules have been reported so far such as derivative of BODIPY, naphthalimide, porphyrins, perylene, BBT etc., they have shown highest absorbing capacity towards greater than 1100 nm. These compounds have potential applications in different fields, such as for biomedical and optoelectronic applications. In this review, we present different classes of light‐harvesters with harvesting range above 1000 nm.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Ravulakollu Srinivasa Rao, Suman, Surya Prakash Singh
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001126

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2D PbS Nanosheets with Zigzag Edges for Efficient CO2 Photoconversion

2D PbS Nanosheets with Zigzag Edges for Efficient CO2 Photoconversion

Edge sites: An enhanced photochemical activity for CO2 reduction was achieved over abundant edges sites PbS nanosheets. This study provides a strategy to regulate structure with effective edge sites for the CO2 reduction.

Abstract

The rational design of transition‐metal sulfide with two‐dimensional (2D) structure and tunable edges on the nanoscale can effectively improve their activity for variously catalytic reactions. Herein, the 2D PbS nanosheets with abundant zigzag edges (e‐PbS NS), which exhibited an excellent performance for CO2 photoconversion to CO, were constructed. The zigzag edges on the PbS NS are beneficial for exposing more active sites and promoting charge separation, thereby accelerating the kinetics process of CO2 photoreduction. This study provides a strategy to regulate structure with effective edge sites for the CO2 reduction.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Zezhou Zhu, Yunteng Qu, Zhiyuan Wang, Fangyao Zhou, Changming Zhao, Yue Lin, Liqiang Li, Yagang Yao, Yuen Wu
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001863

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Heterochiral DNA with Complementary Strands with α‐d and β‐d Configurations: Hydrogen‐Bonded and Silver‐Mediated Base Pairs with Impact of 7‐Deazapurines Replacing Purines

Heterochiral DNA with Complementary Strands with α‐d and β‐d Configurations: Hydrogen‐Bonded and Silver‐Mediated Base Pairs with Impact of 7‐Deazapurines Replacing Purines

Heterochiral DNA with parallel strands has been constructed from complementary strands with nucleosides in the α‐d or β‐d configuration. Purines were replaced by 7‐deazapurines and silver‐mediated base pairs were formed when cytosine residues were facing cytosine, thymine, or adenine. The CD spectra of the modified helices show a B‐type structure almost indistinguishable from natural DNA.

Abstract

Heterochiral DNA with hydrogen‐bonded and silver‐mediated base pairs have been constructed using complementary strands with nucleosides with α‐d or β‐d configuration. Anomeric phosphoramidites were employed to assemble the oligonucleotides. According to the Tm values and thermodynamic data, the duplex stability of the heterochiral duplexes was similar to that of homochiral DNA, but mismatch discrimination was better in heterochiral DNA. Replacement of purines by 7‐deazapurines resulted in stable parallel duplexes, thereby confirming Watson–Crick‐type base pairing. When cytosine was facing cytosine, thymine or adenine residues, duplex DNA formed silver‐mediated base pairs in the presence of silver ions. Although the CD spectra of single strands with α‐d configuration display mirror‐like shapes to those with the β‐d configuration, the CD spectra of the hydrogen‐bonded duplexes and those with a limited number of silver pairs show a B‐type double helix almost indistinguishable from natural DNA. Nonmelting silver ion–DNA complexes with entirely different CD spectra were generated when the number of silver ions was equal to the number of base pairs.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yingying Chai, Xiurong Guo, Peter Leonard, Frank Seela
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002765

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Photoregulation of Gene Expression with Amantadine‐Modified Caged siRNAs through Host–Guest Interactions

Photoregulation of Gene Expression with Amantadine‐Modified Caged siRNAs through Host–Guest Interactions

A new type of caging strategy involving host–guest interactions has been developed by using amantadine‐modified caged siRNAs (see figure). The host–guest interactions between amantadine and β‐cyclodextrin derivatives greatly enhanced the blocking effect of RNA‐induced silencing complex formation and/or processing. The photoregulation of both exogenous and endogenous gene silencing was successfully achieved with low leaking activity.

Abstract

RNA interference is an essential and powerful tool for targeting and verifying specific gene functions. Conditional control of small interfering RNA (siRNA) activity, especially using light activation, is a potential method for regulating target gene expression and functions. In this study, a series of photolabile siRNAs with amantadine modification have been rationally designed and developed through host–guest interactions between amantadine and β‐cyclodextrin derivatives to enhance the blocking effect of siRNA binding and/or RNA‐induced silencing complex processing. These caged siRNAs with amantadine modification at the 5′ end of antisense‐strand RNA were efficiently inactivated through the host–guest interactions between amantadine and β‐cyclodextrin. Photomodulation of the gene silencing activity of these amantadine‐modified caged siRNAs targeting both exogenous and endogenous genes was successfully achieved, which indicates that host–guest interactions could be a new strategy for developing new caged siRNAs for gene photoregulation with low leaking activity.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jinhao Zhang, Nannan Jing, Xinli Fan, Xinjing Tang
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003084

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Divergent Synthesis of γ‐Amino Acid and γ‐Lactam Derivatives from meso‐Glutaric Anhydrides

Divergent Synthesis of γ‐Amino Acid and γ‐Lactam Derivatives from meso‐Glutaric Anhydrides

Desymmetrisation: A divergent synthetic strategy to access both γ‐amino acid and γ‐lactam derivatives by treatment of meso‐glutaric anhydrides with TMSN3 is reported (see scheme).

Abstract

The first divergent synthesis of both γ‐amino acid and γ‐lactam derivatives from meso‐glutaric anhydrides is described. The organocatalytic desymmetrisation with TMSN3 relies on controlled generation of a nucleophilic ammonium azide species mediated by a polystyrene‐bound base to promote efficient silylazidation. After Curtius rearrangement of the acyl azide intermediate to access the corresponding isocyanate, hydrolysis/alcoholysis provided uniformly high yields of γ‐amino acids and their N‐protected counterparts. The same intermediates were shown to undergo an unprecedented decarboxylation–cyclisation cascade in situ to provide synthetically useful yields of γ‐lactam derivatives without using any further activating agents. Mechanistic insights invoke the intermediacy of an unconventional γ‐N‐carboxyanhydride (γ‐NCA) in the latter process. Among the examples prepared using this transformation are 8 APIs/molecules of considerable medicinal interest.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Simon N. Smith, Ryan Craig, Stephen J. Connon
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003280

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Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Germacrene A–A Central Intermediate in Sesquiterpene Biosynthesis

Inspired by nature: This review discusses the unique chemistry of germacrene A, its occurrence in Nature and its central role as an intermediate in the biosynthesis of sesquiterpenes. Biosynthetic derivatives include eudesmanes and guaianes and further compounds arising from skeletal rearrangements. For each compound the reasoning for its assigned absolute configuration is discussed, if it has been established, and the natural sources are summarised.

Abstract

This review summarises known sesquiterpenes whose biosyntheses proceed through the intermediate germacrene A. First, the occurrence and biosynthesis of germacrene A in Nature and its peculiar chemistry will be highlighted, followed by a discussion of 6–6 and 5–7 bicyclic compounds and their more complex derivatives. For each compound the absolute configuration, if it is known, and the reasoning for its assignment is presented.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Houchao Xu, Jeroen S. Dickschat
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002163

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Hydrogen‐Bond Catalysis of Imine Exchange in Dynamic Covalent Systems

Hydrogen‐Bond Catalysis of Imine Exchange in Dynamic Covalent Systems

Hydrogen bond donors, such as thioureas and squaramides, have been shown to catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. The catalytic effect takes place in different solvents and in the presence of sensitive additives, leading to rate accelerations for imine metathesis and transimination with amines, hydrazines, and hydroxylamines.

Abstract

The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Fredrik Schaufelberger, Karolina Seigel, Olof Ramström
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202001666

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Protein‐Templated Hit Identification through an Ugi Four‐Component Reaction

Protein‐Templated Hit Identification through an Ugi Four‐Component Reaction

Screening fast: The Ugi four‐component reaction (Ugi‐4CR) is introduced as a novel reaction in kinetic‐target guided synthesis (KTGS). Novel inhibitors of a model enzyme (aspartic protease endothiapepsin) and new binders of the emerging antibacterial target (β‐sliding clamp DnaN) were successfully identified. This new technique enables a rapid screening of a large number of compounds in early drug discovery.

Abstract

Kinetic target‐guided synthesis represents an efficient hit‐identification strategy, in which the protein assembles its own inhibitors from a pool of complementary building blocks via an irreversible reaction. Herein, we pioneered an in situ Ugi reaction for the identification of novel inhibitors of a model enzyme and binders for an important drug target, namely, the aspartic protease endothiapepsin and the bacterial β‐sliding clamp DnaN, respectively. Highly sensitive mass‐spectrometry methods enabled monitoring of the protein‐templated reaction of four complementary reaction partners, which occurred in a background‐free manner for endothiapepsin or with a clear amplification of two binders in the presence of DnaN. The Ugi products we identified show low micromolar activity on endothiapepsin or moderate affinity for the β‐sliding clamp. We succeeded in expanding the portfolio of chemical reactions and biological targets and demonstrated the efficiency and sensitivity of this approach, which can find application on any drug target.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Federica Mancini, M. Yagiz Unver, Walid A. M. Elgaher, Varsha R. Jumde, Alaa Alhayek, Peer Lukat, Jennifer Herrmann, Martin D. Witte, Matthias Köck, Wulf Blankenfeldt, Rolf Müller, Anna K. H. Hirsch
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002250

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Shedding Light on the Origin of Solid‐State Luminescence Enhancement in Butterfly Molecules

Shedding Light on the Origin of Solid‐State Luminescence Enhancement in Butterfly Molecules

Shaped to soar: A new set of butterfly‐shaped α‐phenylstyrylarene derivatives are synthesised with the aim of improving the solid‐state fluorescence emission of their parent styrylarene compounds. X‐ray diffraction, fluorescence spectroscopy and DFT calculations are carried out to unravel the origin of different photophysical behaviours of these compounds in the solid state.

Abstract

Different molecular strategies have been carefully evaluated to produce solid‐state luminescence enhancement (SLE) in compounds that show dark states in solution. A set of α‐phenylstyrylarene derivatives with a butterfly shape have been designed and synthesised, for the first time, with the aim of improving the solid‐state fluorescence emission of their parent styrylarene compounds. Although these butterfly molecules are not fluorescent in solution, one of them (1,2,4,5‐tetra(α‐phenylstyryl)benzene) exhibits a fluorescence quantum yield as high as 68 % in a drop‐cast sample and 31 % in its crystalline form. In contrast, 1,3,5‐tris(α‐phenylstyryl)benzene and 4,6‐bis(α‐phenylstyryl)pyrimidine do not show SLE. A range of fluorescence spectroscopy experiments and DFT calculations were carried out to unravel the origin of different photophysical behaviour of these compounds in the solid state. The results indicate that a rational strategy to control the SLE effect in luminogens depends on a delicate balance between molecular properties and inter‐/intramolecular interactions in the solid state.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Antonio Sánchez‐Ruiz, Julián Rodríguez‐López, Andrés Garzón‐Ruiz, Sonia B. Jiménez‐Pulido, Nuria A. Illán‐Cabeza, Amparo Navarro, Joaquín C. García‐Martínez
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002920

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Copper‐Based Hybrid Polyion Complexes for Fenton‐Like Reactions

Copper‐Based Hybrid Polyion Complexes for Fenton‐Like Reactions

Photo opportunity: An innovative strategy allowing the development of a new generation of easy‐to‐prepare nanosized catalysts with high tenability is presented. This strategy is based on the formation of hybrid polyion complexes (HPICs) from the complexation of copper ions with a block copolymer consisting of an ionizable complexing block and a neutral stabilizer block. The obtained HPICs are particularly effective for photo‐Fenton catalysis.

Abstract

An innovative strategy allowing the development of a new generation of easy‐to‐prepare and easy‐to‐use nano‐sized catalysts with high tenability is presented. This strategy is based on the formation of hybrid polyion complexes (HPICs) from the complexation of copper with a block copolymer consisting of an ionizable complexing block and a neutral stabilizer block. These complexes have a well‐defined structure and size with a hydrodynamic diameter around 29 nm. They are stable in aqueous solution over a pH range from 4 to 8 and are not sensitive to NaCl salt addition or dilution effects. As a proof‐of‐concept the degradation of naphthol blue black in water through the use of the Fenton or photo‐Fenton reaction is studied. Their performances are comparable to a classical homogeneous reaction, whereas HPICs are easily recyclable by simple dialysis.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Mathieu Mestivier, Jun Rong Li, Aurèle Camy, Camille Frangville, Christophe Mingotaud, Florence Benoît‐Marquié, Jean‐Daniel Marty
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202002362

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Single‐Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture

Single‐Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture

Admix it up: The first mononuclear high‐spin d5 (S=5/2) iron(III) compound that shows both in‐plane magnetic anisotropy and single‐ion magnet behaviour with applied external magnetic field is reported. Despite the expected isotropic spin ground state, it has large and positive magnetic anisotropy (D=+19.2 cm−1), which can be attributed to the contribution of quartet excited states (i.e., spin‐admixed character of the ground state).

Abstract

A mononuclear iron(III) porphyrin compound exhibiting unexpectedly slow magnetic relaxation, which is a characteristic of single‐ion magnet behaviour, is reported. This behaviour originates from the close proximity (≈550 cm−1) of the intermediate‐spin S=3/2 excited states to the high‐spin S=5/2 ground state. More quantitatively, although the ground state is mostly S=5/2, a spin‐admixture model evidences a sizable contribution (≈15 %) of S=3/2 to the ground state, which as a consequence experiences large and positive axial anisotropy (D=+19.2 cm−1). Frequency‐domain EPR spectroscopy allowed the mS= |±1/2⟩→|±3/2⟩ transitions to be directly accessed, and thus the very large zero‐field splitting in this 3d5 system to be unambiguously measured. Other experimental results including magnetisation, Mössbauer, and field‐domain EPR studies are consistent with this model, which is also supported by theoretical calculations.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Marta Viciano‐Chumillas, Geneviève Blondin, Martin Clémancey, Jurek Krzystek, Mykhaylo Ozerov, Donatella Armentano, Alexander Schnegg, Thomas Lohmiller, Joshua Telser, Francesc Lloret, Joan Cano
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003052

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Front Cover: Glucose as an Eco‐Friendly Reductant in a One‐Pot Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones (Eur. J. Org. Chem. /2020)

Front Cover: Glucose as an Eco‐Friendly Reductant in a One‐Pot Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones (Eur. J. Org. Chem. /2020)

The Front Cover shows the Iguaçu cascades in Brazil, that illustrate the reaction cascade consisting of nitrile hydration, nitro‐reduction, imine formation, and cyclization which takes place when glucose is employed as a mild reductant in alkaline aqueous medium for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones. The different intermediates are placed along the path of the falling water. More information can be found in the doi.org/10.1002/ejoc.202000970Communication by G. C. Clososki, T. Opatz et al.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Thiago dos Santos, Caroline Grundke, Tobias Lucas, Luca Großmann, Giuliano Cesar Clososki, Till Opatz
doi.org/10.1002/ejoc.202001285

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Cover Feature: Synthesis and Photophysical Properties of Hexabenzocoronene‐Tetrabenzoporphyrin Architectures (Eur. J. Org. Chem. /2020)

Cover Feature: Synthesis and Photophysical Properties of Hexabenzocoronene‐Tetrabenzoporphyrin Architectures (Eur. J. Org. Chem. /2020)

The Cover Feature shows the receiver‐transmitter properties of “heterodyad‐satellites” derived from hexa‐peri‐hexabenzocoronene (HBC) and tetrabenzoporphyrin (TBP). Owing to the efficient light absorptivity of both “satellites”, a broad range of signals from the near‐UV up to the near‐IR of the solar spectrum can be received. By excited energy transfer from the HBC antennae to the TBP core, the received input is “deconvoluted” to the emission of near‐IR signals, which are transmitted by the “satellites”. More information can be found in the doi.org/10.1002/ejoc.202000860Full Paper by N. Jux et al.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Michael Ruppel, Lampros‐Pascal Gazetas, Dominik Lungerich, Norbert Jux
doi.org/10.1002/ejoc.202001284

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Front Cover: Bioinspired Divergent Oxidative Cyclizations of Geissoschizine: Total Synthesis of (–)‐17‐nor‐Excelsinidine, (+)‐16‐epi‐Pleiocarpamine, (+)‐16‐Hydroxymethyl‐Pleiocarpamine and (+)‐Taberdivarine H (Eur. J. Org. Chem. /2020)

Front Cover: Bioinspired Divergent Oxidative Cyclizations of Geissoschizine: Total Synthesis of (–)‐17‐nor‐Excelsinidine, (+)‐16‐epi‐Pleiocarpamine, (+)‐16‐Hydroxymethyl‐Pleiocarpamine and (+)‐Taberdivarine H (Eur. J. Org. Chem. /2020)

The Front Cover shows pleiocarpamine the emblematic structure of the mavacuran alkaloids. Pleiocarpamine was historically isolated from Pleiocarpa mutica, an apocynaceae from west Africa. More information can be found in the doi.org/10.1002/ejoc.202000962Full Paper by E. Poupon, L. Evanno, G. Vincent et al.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Maxime Jarret, Aurélien Tap, Victor Turpin, Natacha Denizot, Cyrille Kouklovsky, Erwan Poupon, Laurent Evanno, Guillaume Vincent
doi.org/10.1002/ejoc.202001283

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Front Cover: Continuous Flow Synthesis of Quinolines via a Scalable Tandem Photoisomerization‐Cyclization Process (Eur. J. Org. Chem. /2020)

Front Cover: Continuous Flow Synthesis of Quinolines via a Scalable Tandem Photoisomerization‐Cyclization Process (Eur. J. Org. Chem. /2020)

The Cover Feature shows a continuous photochemical process converting amino‐enone substrates into a series of quinoline and tetrahydroquinoline products. The amino‐enone substrates are thereby irradiated with a new high‐power LED lamp in the flow reactor to render the quinoline scaffold in higher efficiency than by using alternative light sources. In a telescoped manner, the quinoline products are then subjected to a Pd‐catalysed hydrogenation process in a reactor that generates hydrogen gas in situ from water. This provides a powerful and green process that delivers various bioactive species including the antimalarial natural product galipinine. More information can be found in the doi.org/10.1002/ejoc.202000957Full Paper by M. Di Filippo and M. Baumann.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Mara Di Filippo, Marcus Baumann
doi.org/10.1002/ejoc.202001282

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Dye‐Doped Silica Nanoparticles for Enhanced ECL‐Based Immunoassay Analytical Performance

Dye‐Doped Silica Nanoparticles for Enhanced ECL‐Based Immunoassay Analytical Performance

Using silica nanoparticles, a 8.5‐fold higher ECL intensity was achieved with respect to a system mimicking a commercial immuno‐sensing system, benefiting from the deep knowledge acquired by combining ECL with nanostructures.

Abstract

The combination of highly sensitive techniques such as electrochemiluminescence (ECL) with nanotechnology sparked new analytical applications, in particular for immunoassay‐based detection systems. In this context, nanomaterials, particularly dye‐doped silica nanoparticles (DDSNPs) are of high interest, since they can offer several advantages in terms of sensitivity and performance. In this work we synthesized two sets of monodispersed and biotinylated [Ru(bpy)3]2+‐doped silica nanoparticles, named bio‐Triton@RuNP and bio‐Igepal@RuNP, obtained following the reverse microemulsion method using two different types of nonionic surfactants. Controlling the synthetic procedures, we were able to obtain nanoparticles (NPs) offering highly intense signal, using tri‐n‐propylamine (TPrA) as coreactant, with bio‐Triton@RuNps being more efficient than bio‐Igepal@RuNP.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Alessandra Zanut, Francesco Palomba, Matilde Rossi Scota, Sara Rebeccani, Massimo Marcaccio, Damiano Genovese, Enrico Rampazzo, Giovanni Valenti, Francesco Paolucci, Luca Prodi
doi.org/10.1002/anie.202009544

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Ag+‐Coupled Black Phosphorus Vesicles with Emerging NIR‐II Photoacoustic Imaging Performance for Cancer Immune‐Dynamic Therapy and Fast Wound Healing

Ag+‐Coupled Black Phosphorus Vesicles with Emerging NIR‐II Photoacoustic Imaging Performance for Cancer Immune‐Dynamic Therapy and Fast Wound Healing

An Ag+ coupled black phosphorus vesicle (BP Ve‐Ag+) was assembled from black phosphorus quantum dots (BP QDs) and simultaneously accommodated with Ag+. The optical absorption ability of BP Ve‐Ag+ in second near infrared (NIR‐II) region was significantly enhanced, which benefited from the intense charge coupling between BP QD and Ag+.

Abstract

A silver‐ion‐coupled black phosphorus (BP) vesicle (BP Ve‐Ag+) with a second near infrared (NIR‐II) window photoacoustic (PA) imaging capability was firstly constructed to maximize the potential of BP quantum dot (QD) in deeper bioimaging and diversified therapy. The embedded Ag+ could improve the relatively large band gap of BP QD via intense charge coupling based on theoretical simulation results, subsequently leading to the enhanced optical absorption capability, accompanied with the occurrence of the strong NIR‐II PA signal. Guiding by NIR‐II PA bioimaging, the hidden Ag+ could be precisely released with the disassembly of Ve during photodynamic therapy process and captured by macrophages located in lesion region for arousing synergistic cancer photodynamic/Ag+ immunotherapy. BP Ve‐Ag+ can contrapuntally kill pathogenic bacteria and accelerate wound healing monitored by NIR‐II PA imaging.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zhi Li, Qinrui Fu, Jiamin Ye, Xiaoguang Ge, Jie Wang, Jibin Song, Huanghao Yang
doi.org/10.1002/anie.202009609

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Structural Phase Transitions of a Molecular Metal Oxide

Structural Phase Transitions of a Molecular Metal Oxide

Structural transitions of the molecular metal oxide [Na@(SO3)2(n‐BuPO3)4MoV4MoVI14O49]5− were examined by single‐crystal X‐ray diffraction analysis. The Na+ encapsulated in the discrete metal‐oxide anion exhibited a reversible order–disorder transition with distortion of the Mo–O molecular framework induced by temperature (see picture).

Abstract

The structural phase of a metal oxide changes with temperature and pressure. During phase transitions, component ions move in multidimensional metal–oxygen networks. Such macroscopic structural events are robust to changes in particle size, even at scales of around 10 nm, and size effects limiting these transitions are particularly important in, for example, high‐density memory applications of ferroelectrics. In this study, we examined structural transitions of the molecular metal oxide [Na@(SO3)2(n‐BuPO3)4MoV4MoVI14O49]5− (Molecule 1) at approximately 2 nm by using single‐crystal X‐ray diffraction analysis. The Na+ encapsulated in the discrete metal‐oxide anion exhibited a reversible order–disorder transition with distortion of the Mo–O molecular framework induced by temperature. Similar order–disorder transitions were also triggered by chemical pressure induced by removing crystalline solvent molecules in the single‐crystal state or by substituting the countercation to change the molecular packing.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Masaru Fujibayashi, Yu Watari, Ryo Tsunashima, Sadafumi Nishihara, Shin‐ichiro Noro, Chang‐Gen Lin, Yu‐Fei Song, Kiyonori Takahashi, Takayoshi Nakamura, Tomoyuki Akutagawa
doi.org/10.1002/anie.202010748

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TTF‐Annulated Silicon Phthalocyanine Oligomers and Their External‐Stimuli‐Responsive Orientational Ordering

TTF‐Annulated Silicon Phthalocyanine Oligomers and Their External‐Stimuli‐Responsive Orientational Ordering

External‐stimuli‐responsive orientational ordering was achieved based on the rotational isomerism of μ‐oxo silicon phthalocyanine oligomers and intermolecular interaction of tetrathiafulvalene. The stable performance of oligomers as a lithium‐ion battery cathode compared with monomer ensures potential use of one‐dimensionally stacked oligomer structures toward creation of artificial molecular systems for energy/electron harvesting and transfer.

Abstract

Orientational control of functional molecules is essential to create complex functionalities as seen in nature; however, such artificial systems have remained challenge. Herein, we have succeeded in controlling rotational isomerism of μ‐oxo silicon phthalocyanine (SiPc) oligomers to achieve an external‐stimuli‐responsive orientational ordering using intermolecular interactions of tetrathiafulvalene (TTF). In this system, three modes of orientations, free rotation, eclipsed conformation, and staggered conformation, were interconverted in response to the oxidation states of TTF, which varied interactions from association due to formation of mixed‐valence TTF dimer to dissociation due to electrostatic repulsion between TTF dications. Furthermore, a stable performance of oligomers as a cathode material in a Li‐ion battery proved that the one‐dimensionally stacked, rotatable structure of SiPc oligomers is useful to control the orientation of functional molecules toward molecular electronics.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yuta Shiina, Yuto Kage, Ko Furukawa, Heng Wang, Hirofumi Yoshikawa, Hiroyuki Furuta, Nagao Kobayashi, Soji Shimizu
doi.org/10.1002/anie.202011025

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