Lossen Rearrangement vs C–N Reductive Elimination Enabled by Rh(III)-Catalyzed C–H Activation/Selective Lactone Ring-Opening: Chemodivergent Synthesis of Quinolinones and Dihydroisoquinolinones

Organic Letters: Latest Articles (ACS Publications)
Authors: Mengyao Bian, Hamdulla Mawjuda, Hui Gao, Huiying Xu, Zhi Zhou, and Wei Yi
feedproxy.google.com/~r/acs/orlef7/~3/OuU-FjHuQa0/acs.orglett.0c03734

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Tunable Synthesis of Hierarchical Yolk/Double‐Shelled SiOx@TiO2@C Nanospheres for High‐Performance Lithium‐Ion Batteries

Tunable Synthesis of Hierarchical Yolk/Double‐Shelled SiOx@TiO2@C Nanospheres for High‐Performance Lithium‐Ion Batteries

Hierarchical yolk‐shell SiOx@TiO2@C nanospheres were prepared via a facile sol‐gel method combined with carbon coating. The unique structure possessing a suitable void space between yolk and shell can accommodate the volume expansion of the SiOx core; the lithiation products of STC3 including LimTiO2, LinSi, and LizC6 are reversible, and exhibit excellent electrochemical performance.

Abstract

This work reports the preparation of unique hierarchical yolk/double‐shelled SiOx@TiO2@C nanospheres with different voids by a facile sol‐gel method combined with carbon coating. In the preparation process, SiOx nanosphere is used as a hard template. Etch time of SiOx yolk affects the morphology and electrochemical performance of SiOx@TiO2@C. With the increase in etch time, the yolk/double‐shelled SiOx@TiO2@C with 15 and 30 nm voids and the TiO2@C hollow nanospheres are obtained. The yolk/double‐shelled SiOx@TiO2@C nanospheres exhibit remarkable lithium‐ion battery performance as anodes, including high lithium storage capacity, outstanding rate capability, good reversibility, and stable long‐term cycle life. The unique structure can accommodate the large volume change of the SiOx yolk, provide a unique buffering space for the discharge/charge processes, improve the structural stability of the electrode material during repeated Li+ intercalation/deintercalation processes, and enhance the cycling stability. The SiOx@TiO2@C with 30 nm void space exhibits a high discharge specific capacity of ≈1195.4 mA h g−1 at the current density of 0.1 A g−1 after 300 cycles and ≈701.1 mA h g−1 at 1 A g−1 for over 800 cycles. These results suggest that the proposed particle architecture is promising and may have potential applications in improving various high performance anode materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Qinghua Gong, Haiqing Wang, Wenhua Song, Bin Sun, Pei Cao, Shaonan Gu, Xuefeng Sun, Guowei Zhou
doi.org/10.1002/chem.202003246

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Elucidation of the Chemical Role of the Pyroclastic Materials on the State of Conservation of Mural Paintings from Pompeii

Elucidation of the Chemical Role of the Pyroclastic Materials on the State of Conservation of Mural Paintings from Pompeii

Pyroclastic materials buried and protected ancient Pompeii throughout the centuries. In this work, we demonstrate that they could represent a threat for the conservation state of the mural paintings, since rainwater and groundwater cause the leaching and transfer of ions to the mural paintings, promoting salt crystallisation. At Pompeii, the latter is one of the main causes of the detachment of the pictorial layers.

Abstract

Pyroclastic strata have always been thought to protect the archaeological remains of the Vesuvian area (Italy), hence allowing their conservation throughout the centuries. In this work, we demonstrate that they constitute a potential threat for the conservation state of the mural paintings of Pompeii. The ions that could be leached from them and the ion‐rich groundwater coming from the volcanic soil/rocks may contribute to salt crystallisation. Thermodynamic modelling not only allowed to predict which salts can precipitate from such leaching events but also assisted the identification of additional sources of sulfates and alkali metals to explain the formation of the sulfates identified in efflorescences from the mural paintings of Pompeii. For the future, fluorine, mainly related to a volcanic origin, can be proposed as a marker to monitor the extent of the impact in the mural paintings of Pompeii in situ.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Silvia Pérez‐Diez, Luis Javier Fernández‐Menéndez, Héctor Morillas, Alberta Martellone, Bruno De Nigris, Massimo Osanna, Nerea Bordel, Francesco Caruso, Juan Manuel Madariaga, Maite Maguregui
doi.org/10.1002/anie.202010497

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Rare‐Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox‐Switchable Single‐Molecule Magnets

Rare‐Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox‐Switchable Single‐Molecule Magnets

Redox switchable single‐molecule magnets (SMM) arranged in ordered architectures are valuable objects for use in memory devices. A metal–organic framework is an ideal platform to integrate SMM as nodes and redox‐active organic linkers as switching probes (see figure).

Abstract

Using the redox‐active tetrathiafulvalene tetrabenzoate (TTFTB4−) as the linker, a series of stable and porous rare‐earth metal–organic frameworks (RE‐MOFs), [RE93‐OH)133‐O)(H2O)9(TTFTB)3] (1‐RE, where RE=Y, Sm, Gd, Tb, Dy, Ho, and Er) were constructed. The RE93‐OH)133‐O) (H2O)9](CO2)12 clusters within 1‐RE act as segregated single‐molecule magnets (SMMs) displaying slow relaxation. Interestingly, upon oxidation by I2, the S=0 TTFTB4− linkers of 1‐RE were converted into S= TTFTB.3− radical linkers which introduced exchange‐coupling between SMMs and modulated the relaxation. Furthermore, the SMM property can be restored by reduction in N,N‐dimethylformamide. These results highlight the advantage of MOFs in the construction of redox‐switchable SMMs.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jian Su, Shuai Yuan, Jing Li, Hai‐Ying Wang, Jing‐Yuan Ge, Hannah F. Drake, Chanel F. Leong, Fei Yu, Deanna M. D’Alessandro, Mohamedally Kurmoo, Jing‐Lin Zuo, Hong‐Cai Zhou
doi.org/10.1002/chem.202004883

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On the Role of Alkali‐Metal‐Like Superatom Al12P in Reduction and Conversion of Carbon Dioxide

On the Role of Alkali‐Metal‐Like Superatom Al12P in Reduction and Conversion of Carbon Dioxide

Superatom catalysis: The crucial role of Al12P in the CO2 reduction as well as the subsequent cycloaddition reaction with propylene oxide and radical reaction with hydrogen gas to form high‐value chemicals is revealed.

Abstract

Developing efficient catalysts for the conversion of CO2 into fuels and value‐added chemicals is of great significance to relieve the growing energy crisis and global warming. With the assistance of DFT calculations, it was found that, different from Al12X (X=Be, Al, and C), the alkali‐metal‐like superatom Al12P prefers to combine with CO2 via a bidentate double oxygen coordination, yielding a stable Al12P(η2‐O2C) complex containing an activated radical anion of CO2 (i.e., CO2.−). Thereby, this compound could not only participate in the subsequent cycloaddition reaction with propylene oxide but also initiate the radical reaction with hydrogen gas to form high‐value chemicals, revealing that Al12P can play an important role in catalyzing these conversion reactions. Considering that Al12P has been produced in laboratory and is capable of absorbing visible light to drive the activation and transformation of CO2, it is anticipated that this work could guide the discovery of additional superatom catalysts for CO2 transformation and open up a new research field of superatom catalysis.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xiao‐Ling Zhang, Li Zhang, Ya‐Ling Ye, Xiang‐Hui Li, Bi‐Lian Ni, Ying Li, Wei‐Ming Sun
doi.org/10.1002/chem.202003733

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Enhanced Stability and Emission Properties of Perylene Dyes by Surface Tethering: Preparation of Fluorescent Ru Nanoparticle Suspensions by Alkyne Linker Chemistry

Enhanced Stability and Emission Properties of Perylene Dyes by Surface Tethering: Preparation of Fluorescent Ru Nanoparticle Suspensions by Alkyne Linker Chemistry

Support groups: Ru0 nanoparticles were prepared, and their surfaces were modified through the formation of vinylidene linkages with a perylene dye and a Si‐containing alkyne. The vinylidene groups stabilize the Ru0 nanoparticles against precipitation, and the Ru0 nanoparticles enhance the absorption and emission properties (and the stability) of the alkyne‐containing perylene dyes.

Abstract

Spherical ruthenium nanoparticles (NPs) with a narrow size distribution were synthesised in ethanol by a facile low‐temperature solvothermal process without the assistance of templates, structure‐directing agents or post annealing/reduction treatments. Surface passivation with a fluorescent perylene dye (EP), and with silane ligands (ETMS), both initially bearing alkyne groups and subsequently forming vinylidene linkages, provided stable suspensions of the marginally soluble free EP. Quantitative analysis of the suspension gave an estimated EP surface coverage of 15 %, corresponding to an EP/ETMS mole ratio of ≈1:6. Photophysical evaluation of the bound and free dye revealed similar absorption bands and extinction coefficients and improved properties for the bound state, including enhanced fluorescence in the visible range for the bound dye, an extended absorption range into the near‐UV providing strong emission in the visible, and significantly improved photostability. The physical basis of the enhanced photophysical properties, potential routes to further improvements and the implications for applications are discussed.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Eduardo Morais, Cara Moloney, Colin O’Modhrain, Eoin McKiernan, Dermot F. Brougham, James A. Sullivan
doi.org/10.1002/chem.202003514

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Siloxyaluminate and Siloxygallate Complexes as Models for Framework and Partially Hydrolyzed Framework Sites in Zeolites and Zeotypes

Siloxyaluminate and Siloxygallate Complexes as Models for Framework and Partially Hydrolyzed Framework Sites in Zeolites and Zeotypes

Zeotype framework sites: The synthesis and characterization of anionic molecular models for aluminum and gallium framework sites and partially hydrolyzed framework sites on silica with M[OSi(OtBu)3]4 and HOM[OSi(OtBu)3]3 cores are reported. Upon treatment of partially hydrolyzed framework‐site models with alcohols, alkoxide complexes were formed, reminiscent of proposed precatalyst activation for transfer hydrogenations.

Abstract

Anionic molecular models for nonhydrolyzed and partially hydrolyzed aluminum and gallium framework sites on silica, M[OSi(OtBu)3]4 and HOM[OSi(OtBu)3]3 (where M=Al or Ga), were synthesized from anionic chlorides Li{M[OSi(OtBu)3]3Cl} in salt metathesis reactions. Sequestration of lithium cations with [12]crown‐4 afforded charge‐separated ion pairs composed of monomeric anions M[OSi(OtBu)3]4 with outer‐sphere [([12]crown‐4)2Li]+ cations, and hydroxides {HOM[OSi(OtBu)3]3} with pendant [([12]crown‐4)Li]+ cations. These molecular models were characterized by single‐crystal X‐ray diffraction, vibrational spectroscopy, mass spectrometry and NMR spectroscopy. Upon treatment of monomeric [([12]crown‐4)Li]{HOM[OSi(OtBu)3]3} complexes with benzyl alcohol, benzyloxide complexes were formed, modeling a possible pathway for the formation of active sites for Meerwin–Ponndorf–Verley (MPV) transfer hydrogenations with Al/Ga‐doped silica catalysts.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: James P. Dombrowski, Micah S. Ziegler, Neelay M. Phadke, Erum Mansoor, Daniel S. Levine, Ryan J. Witzke, Martin Head‐Gordon, Alexis T. Bell, T. Don Tilley
doi.org/10.1002/chem.202002926

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New Promises and Opportunities in 3D Printable Inks Based on Coordination Compounds for the Creation of Objects with Multiple Applications

New Promises and Opportunities in 3D Printable Inks Based on Coordination Compounds for the Creation of Objects with Multiple Applications

Shaping the future in 3D: Metal–organic compounds with dynamic coordination bonds as new possible 3D inks with interesting properties are reviewed. Technological advances, the combination of various printing techniques, and the properties of coordination bonds lead to the creation of surprising new printable inks and objects with highly complex shapes that will close the gap between academia and industry for research into coordination compounds.

Abstract

This review focuses on the usefulness of coordination bonds to create 3D printable inks and shows how the union of chemistry and 3D technology contributes to new scientific advances, by allowing amorphous or polycrystalline solids to be transformed into objects with the desired shape for successful applications. The review clearly shows how there has been considerable increase in the manufacture of objects based on the combination of organic matrices and coordination compounds. These coordination compounds are usually homogeneously dispersed within the matrix, anchored onto a proper support or coating the printed object, without destroying their unique properties. Advances are so rapid that today it is already possible to 3D print objects made exclusively from coordination compounds without additives. The new printable inks are made mainly with nanoscale nonporous coordination polymers, metal–organic gels, or metal–organic frameworks. The highly dynamic coordination bond allows the creation of objects, which respond to stimuli, that can act as sensors and be used for drug delivery. In addition, the combination of metal–organic frameworks with 3D printing allows the adsorption or selective capacity of the object to be increased, relative to that of the original compound, which is useful in energy storage, gas separation, or water pollutant elimination. Furthermore, the presence of the metal ion can give them new properties, such as luminescence, that are useful for application in sensors or anticounterfeiting. Technological advances, the combination of various printing techniques, and the properties of coordination bonds lead to the creation of surprising, new, printable inks and objects with highly complex shapes that will close the gap between academia and industry for research into coordination compounds.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Noelia Maldonado, Pilar Amo‐Ochoa
doi.org/10.1002/chem.202002259

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Metal–Organic Framework Derived Bimetallic Materials for Electrochemical Energy Storage

Metal–Organic Framework Derived Bimetallic Materials for Electrochemical Energy Storage

Bimetallic metal–organic frameworks (MOFs) have been applied as sacrificial templates or precursors in the preparation of derivatives that can be used in supercapacitors. Bimetallic MOFs and their derivatives can offer the advantages of improved electrochemical activity, convenient redox reactions, and high electrical conductivity, and are excellent candidates as advanced electrode materials.

Abstract

Supercapacitors (SCs), showing excellent power density, long service life, and high reversibility, have received great attention because of the increasing demand for energy storage devices. To further improve their performance, it is essential to develop advanced electrode materials. One group of materials, porous crystalline solids referred to as metal–organic frameworks (MOFs), have proved to be excellent templates for synthesizing functional materials to be employed in the preparation of electrodes for SCs. In comparison to monometallic MOFs, bimetallic MOFs and their derivatives offer a number of advantages, including tunable electrochemical activity, high charge capacity, and improved electrical conductivity. This review focuses on the use of MOF‐derived bimetallic materials in SCs, the origin of the improved performance, and the latest developments in the field. Furthermore, the challenges and perspectives in this research area are discussed.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Soheila Sanati, Reza Abazari, Josep Albero, Ali Morsali, Hermenegildo García, Zibin Liang, Ruqiang Zou
doi.org/10.1002/anie.202010093

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AIEgen‐Lipid Conjugate for Rapid Labeling of Neutrophils and Monitoring of Their Behavior

AIEgen‐Lipid Conjugate for Rapid Labeling of Neutrophils and Monitoring of Their Behavior

An AIE‐Lipid conjugate was designed to offer ultrafast, wash‐free and biocompatible labeling of neutrophils for their in vitro and in vivo behavior monitoring.

Abstract

Studies on neutrophil‐based nanotherapeutic engineering have shown great potentials in treating infection and inflammation disorders. Conventional neutrophil labeling methods are time‐consuming and often result in undesired contamination and activation since neutrophils are terminal‐differentiated cells with a half‐life span of only 7 h. A simple, fast, and biocompatible strategy to construct engineered neutrophils is highly desirable but remains difficult to achieve. In this study, we present an AIEgen‐lipid conjugate, which can efficiently label harvested neutrophils in 30 s with no washing step required. This fast labeling method does not affect the activation and transmigration property of neutrophils, which has been successfully used to monitor neutrophil behaviors such as the chemotaxis process and migrating function towards inflammation sites both in vitro and in vivo, offering a tantalizing prospect for neutrophil‐based nanotherapeutics studies.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Xingang Liu, Min Wu, Meng Wang, Yukun Duan, Chi Uyen Phan, Huan Chen, Guping Tang, Bin Liu
doi.org/10.1002/anie.202012594

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Study of Excited States and Electron Transfer of Semiconductor‐Metal‐Complex Hybrid Photocatalysts for CO2 Reduction by Using Picosecond Time‐Resolved Spectroscopies

Study of Excited States and Electron Transfer of Semiconductor‐Metal‐Complex Hybrid Photocatalysts for CO2 Reduction by Using Picosecond Time‐Resolved Spectroscopies

Hybrid photocatalysts: Photoexcited electron transfer from a photoactive semiconductor to the metal‐complex catalyst is a key process for photocatalytic CO2 reduction with hybrid photocatalysts. A detailed analysis of time‐resolved infrared and emission measurements reveals that the electron transfer does not occur directly upon photoexcitation only, but that the photoexcited electron transfers within one picosecond to a new excited state.

Abstract

A semiconductor‐metal‐complex hybrid photocatalyst was previously reported for CO2 reduction; this photocatalyst is composed of nitrogen‐doped Ta2O5 as a semiconductor photosensitizer and a Ru complex as a CO2 reduction catalyst, operating under visible light (>400 nm), with high selectivity for HCOOH formation of more than 75 %. The electron transfer from a photoactive semiconductor to the metal‐complex catalyst is a key process for photocatalytic CO2 reduction with hybrid photocatalysts. Herein, the excited‐state dynamics of several hybrid photocatalysts are described by using time‐resolved emission and infrared absorption spectroscopies to understand the mechanism of electron transfer from a semiconductor to the metal‐complex catalyst. The results show that electron transfer from the semiconductor to the metal‐complex catalyst does not occur directly upon photoexcitation, but that the photoexcited electron transfers to a new excited state. On the basis of the present results and previous reports, it is suggested that the excited state is a charge‐transfer state located between shallow defects of the semiconductor and the metal‐complex catalyst.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Shunsuke Sato, Sei’ichi Tanaka, Ken‐ichi Yamanaka, Shu Saeki, Keita Sekizawa, Tomiko M. Suzuki, Takeshi Morikawa, Ken Onda
doi.org/10.1002/chem.202004068

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Molecularly Imprinted Polymer‐Based Smart Prodrug Delivery System for Specific Targeting, Prolonged Retention, and Tumor Microenvironment‐Triggered Release

Molecularly Imprinted Polymer‐Based Smart Prodrug Delivery System for Specific Targeting, Prolonged Retention, and Tumor Microenvironment‐Triggered Release

A molecularly imprinted polymer (MIP) based smart prodrug delivery nanoplatform was demonstrated with the ability to specifically target tumor sites with prolonged retention time and gradual tumor microenvironmental pH‐triggered release. The MIP‐based prodrug delivery is liver‐independent but tumor‐dependent, which not only greatly enhances tumor specificity but also expands the scope of applicable prodrugs.

Abstract

Prodrug and drug delivery systems are two effective strategies for improving the selectivity of chemotherapeutics. Molecularly imprinted polymers (MIPs) have emerged as promising carriers in targeted drug delivery for cancer treatment, but they have not yet been integrated with the prodrug strategy. Reported here is an MIP‐based smart prodrug delivery system for specific targeting, prolonged retention time, and tumor microenvironment‐triggered release. 5′‐Deoxy‐5‐fluorocytidine (DFCR) and sialic acid (SA) were used as a prodrug and a marker for tumor targeting, respectively. Their co‐imprinted nanoparticles were prepared as a smart carrier. Prodrug‐loaded MIP specifically and sustainably accumulated at the tumor site and then gradually released. Unlike conventional prodrug designs, which often require in‐liver bioconversion, this MIP‐based prodrug delivery is liver‐independent but tumor‐dependent. Thus, this study opens new access to the development of smart prodrug delivery nanoplatforms.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zikuan Gu, Yueru Dong, Shuxin Xu, Lisheng Wang, Zhen Liu
doi.org/10.1002/anie.202012956

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Solution‐Processed White Circularly Polarized Organic Light‐Emitting Diodes Based on Chiral Binaphthyl Emitters

Solution‐Processed White Circularly Polarized Organic Light‐Emitting Diodes Based on Chiral Binaphthyl Emitters

White CP‐OLED devices showing intense CP‐EL signals are successfully fabricated for the first time by the combination of the blue CPL emitters (S‐/RBN‐tCz) with the orange CPL emitters (S‐/RBN‐PXZ).

Abstract

By combining the blue and orange CPL or functionalized bis‐benzoxanethones emitters (S‐/RBN‐tCz and S‐/RBN‐PXZ), warm white CP‐OLEDs were fabricated using solution‐processed single emitting layer strategy. The successful realization of white CP‐EL benefited from the same stable binaphthyl chirality and similar rigid structure of the two emissive CPL emitters. The devices exhibited the low turn‐on voltage of ≈4.3 V, maximum luminance of ≈10200 cd m−2 and maximum current efficiency of ≈2.0 cd A−1. Most significantly, the devices with CIE coordinates of (0.32, 0.45) displayed intense CP‐EL signals in the spectral range of 450 to 650 nm, and showed stable gEL values of ≈10−3 as the luminance increased from 100 to 6000 cd m−2. To the best of our knowledge, this work provides for the first time a simple and feasible strategy to fabricate solution‐processed white CP‐OLEDs based on the co‐doping of the CPL emitters.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yu Zhang, Jie Li, Yiwu Quan, Shanghui Ye, Yixiang Cheng
doi.org/10.1002/chem.202003721

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Oligo‐Quinolylene–Vinylene Foldamers

Oligo‐Quinolylene–Vinylene Foldamers

Despite lacking polar elements, vinylene isosteres are compatible with the helical conformations of oligo‐quinolinecarboxamides, paving the way to the modulation of charge transport properties in these systems.

Abstract

Quinoline based aromatic amide foldamers are known to adopt stable folded conformations. We have developed a synthetic approach to produce similar oligomers where all amide bonds, or part of them, have been replaced by an isosteric vinylene group. The results of solution and solid state structural studies show that oligomers exclusively containing vinylene linkages are not well folded, and adopt predominantly flat conformations. In contrast, a vinylene segment flanked by helical oligoamides also folds in a helix, albeit with a slightly lower curvature. The presence of vinylene functions also result in an extension of π‐conjugation across the oligomer that may change charge transport properties. Altogether, these results pave the way to foldamers in which both structural control and specific electronic properties may be engineered.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jinhua Wang, Barbara Wicher, Victor Maurizot, Ivan Huc
doi.org/10.1002/chem.202003559

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Multi‐Mode Color‐Tunable Long Persistent Luminescence in Single‐Component Coordination Polymers

Multi‐Mode Color‐Tunable Long Persistent Luminescence in Single‐Component Coordination Polymers

By delicate design of coordination polymers incorporating different halogens, multi‐mode color‐tunable long persistent luminescence (LPL) from green to yellow or green to red was possible. The LPL emission colors can be tuned by time, excitation, and temperature, revealing the counter‐balanced mechanisms from single‐molecule and aggregate triplet excited states resulting from an external heavy‐atom effect.

Abstract

Materials with tunable long persistent luminescence (LPL) properties have wide applications in security signs, anti‐counterfeiting, data encrypting, and other fields. However, the majority of reported tunable LPL materials are pure organic molecules or polymers. Herein, a series of metal‐organic coordination polymers displaying color‐tunable LPL were synthesized by the self‐assembly of HTzPTpy ligand with different cadmium halides (X=Cl, Br, and I). In the solid state, their LPL emission colors can be tuned by the time‐evolution, as well as excitation and temperature variation, realizing multi‐mode dynamic color tuning from green to yellow or green to red, and are the first such examples in single‐component coordination polymer materials. Single‐crystal X‐ray diffraction analysis and theoretical calculations reveal that the modification of LPL is due to the balanced action from single molecule and aggregate triplet excited states caused by an external heavy‐atom effect. The results show that the rational introduction of different halide anions into coordination polymers can realize multi‐color LPL.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zheng Wang, Cheng‐Yi Zhu, Jun‐Ting Mo, Xian‐Yan Xu, Jia Ruan, Mei Pan, Cheng‐Yong Su
doi.org/10.1002/anie.202012831

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Alkali‐Metal Mediation: Diversity of Applications in Main‐Group Organometallic Chemistry

Alkali‐Metal Mediation: Diversity of Applications in Main‐Group Organometallic Chemistry

Alkali metals top the league when it comes to mediating reactions. Organolithium compounds have long been their captain, but now organosodium and organopotassium compounds are finding their form too. This Review highlights their victories in homogeneous catalysis, organic synthesis, low‐valent aluminium chemistry, polymerization, and green chemistry.

Abstract

Organolithium compounds have been at the forefront of synthetic chemistry for over a century, as they mediate the synthesis of myriads of compounds that are utilised worldwide in academic and industrial settings. For that reason, lithium has always been the most important alkali metal in organometallic chemistry. Today, that importance is being seriously challenged by sodium and potassium, as the alkali‐metal mediation of organic reactions in general has started branching off in several new directions. Recent examples covering main‐group homogeneous catalysis, stoichiometric organic synthesis, low‐valent main‐group metal chemistry, polymerization, and green chemistry are showcased in this Review. Since alkali‐metal compounds are often not the end products of these applications, their roles are rarely given top billing. Thus, this Review has been written to alert the community to this rising unifying phenomenon of “alkali‐metal mediation”.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Thomas X. Gentner, Robert E. Mulvey
doi.org/10.1002/anie.202010963

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Statistical Analysis of Glycosylation Reactions

Statistical Analysis of Glycosylation Reactions

Predictable outcomes: Control of stereoselectivity during the glycosylation reaction is the main challenge of synthetic chemistry because the reaction can generate both α‐ and β‐glycosides. Recent mechanistic studies that have applied statistical analysis and quantitation for defining stereoselective changes during the reaction process are discussed.

Abstract

Chemical synthesis is one of the practical approaches to access carbohydrate‐based natural products and their derivatives with high quality and in a large quantity. However, stereoselectivity during the glycosylation reaction is the main challenge because the reaction can generate both α‐ and β‐glycosides. The main focus of the present article is the concept of recent mechanistic studies that have applied statistical analysis and quantitation for defining stereoselective changes during the reaction process. Based on experimental evidence, a detailed discussion associated with the mechanism and degree of influence affecting the stereoselective outcome of glycosylation is included.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Chun‐Wei Chang, Mei‐Huei Lin, Cheng‐Chung Wang
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003105

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Large Polyhedral Oligomeric Silsesquioxane Cages: The Isolation of Functionalized POSS with an Unprecedented Si18O27 Core

Large Polyhedral Oligomeric Silsesquioxane Cages: The Isolation of Functionalized POSS with an Unprecedented Si18O27 Core

A POSS cage with a Si18O27 core is described. In contrast to previous large POSS cages (n>16), our synthesis afforded a single isomeric form, unambiguously identified from among the nine possible isomers by NMR. This is the largest Tn compound isolated as a single isomer. A new ring strain model is described that correlates the chemical shifts of non‐equivalent 29Si NMR signals in POSS.

Abstract

The synthesis of organo‐functionalized polyhedral oligomeric silsesquioxanes (POSS, (R‐SiO1.5)n, Tn) is an area of significant activity. To date, T14 is the largest such cage synthesized and isolated as a single isomer. Herein, we report an unprecedented, single‐isomer styryl‐functionalized T18 POSS. Unambiguously identified among nine possible isomers by multinuclear solution NMR (1H, 13C, and 29Si), MALDI‐MS, FTIR, and computational studies, this is the largest single‐isomer functionalized Tn compound isolated to date. A ring‐strain model was developed to correlate the 29Si resonances with the number of 6‐, 5‐, and/or 4‐Si‐atom rings that each non‐equivalent Si atom is part of. The model successfully predicts the speciation of non‐equivalent Si atoms in other families of Tn compounds, demonstrating its general applicability for assigning 29Si resonances to Si atoms in cage silsesquioxanes and providing a useful tool for predicting Si‐atom environments.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Mathilde Laird, Niklas Herrmann, Naseem Ramsahye, Cédric Totée, Carole Carcel, Masafumi Unno, John R. Bartlett, Michel Wong Chi Man
doi.org/10.1002/anie.202010458

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Sub‐3 nm Ultrafine Cu2O for Visible Light Driven Nitrogen Fixation

Sub‐3 nm Ultrafine Cu2O for Visible Light Driven Nitrogen Fixation

Ultrafine Cu2O, less than 3 nm in size, was synthesized by facile in situ reduction of layered double hydroxide (LDH). This ultrafine Cu2O exhibits superior performance for visible light driven N2 reduction to NH3, with a nearly 64‐fold increase in NH3 production rate compared to bulk Cu2O, and it is superior to most of the reported benchmark photocatalysts. The remarkable activity can be attributed to the availability of surface sites and the generation of long‐lived photoexcited electrons.

Abstract

Cu2O, a low‐cost, visible light responsive semiconductor photocatalyst represents an ideal candidate for visible light driven photocatalytic reduction of N2 to NH3 from the viewpoint of thermodynamics, but it remains unexplored. Reported here is the successful synthesis of uniformly sized and ultrafine Cu2O platelets, with a lateral size of <3 nm, by the in situ topotactic reduction of a CuII‐containing layered double hydroxide with ascorbic acid. The supported ultrafine Cu2O offered excellent performance and stability for the visible light driven photocatalytic reduction of N2 to NH3 (the Cu2O‐mass‐normalized rate as high as 4.10 mmol g−1 h−1 at λ>400 nm), with the origin of the high activity being long‐lived photoexcited electrons in trap states, an abundance of exposed active sites, and the underlying support structure. This work guides the future design of ultrafine catalysts for NH3 synthesis and other applications.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Shuai Zhang, Yunxuan Zhao, Run Shi, Chao Zhou, Geoffrey I. N. Waterhouse, Zhuan Wang, Yuxiang Weng, Tierui Zhang
doi.org/10.1002/anie.202013594

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Regio‐ and Diastereoselective Rhodium‐Catalyzed Allylic Substitution with Unstabilized Benzyl Nucleophiles

Regio‐ and Diastereoselective Rhodium‐Catalyzed Allylic Substitution with Unstabilized Benzyl Nucleophiles

A range of benzylzinc reagents were employed as nucleophiles in a regio‐ and diastereoselective rhodium‐catalyzed substitution of acyclic fluorinated allylic carbonates under mild conditions. The method enables direct installation of a privileged ternary benzyl scaffold, which is a ubiquitous motif in medicinal chemistry.

Abstract

We have developed a highly regio‐ and diastereoselective rhodium‐catalyzed allylic substitution of challenging alkyl‐substituted secondary allylic carbonates with benzylzinc reagents, which are prepared from widely available benzyl halides. This process utilizes rhodium(III) chloride as a commercially available, high‐oxidation state and bench‐stable pre‐catalyst to provide a rare example of a regio‐ and diastereoselective allylic substitution in the absence of an exogenous ligand. This reaction tolerates electronically diverse benzylzinc nucleophiles and an array of functionalized and/or challenging aliphatic allylic electrophiles. Finally, the configurational fluxionality of the rhodium‐allyl intermediate is exploited to develop a novel diastereoselective process for the construction of vicinal acyclic ternary/ternary stereogenic centers, in addition to a cyclic ternary/quaternary derivative.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Debasis Pal, Timothy B. Wright, Ryan O’Connor, P. Andrew Evans
doi.org/10.1002/anie.202008071

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Ionic Liquids with More than One Metal: Optical and Electrochemical Properties versus d‐Block Metal Combinations

Ionic Liquids with More than One Metal: Optical and Electrochemical Properties versus d‐Block Metal Combinations

Mixed metal tetrahalidometallate ionic liquids (ILs) were for the first time synthesized and studied for their structural, optical, and electrochemical properties. The ILs exhibit high conductivities and tunable optical absorption and are thus novel and highly versatile candidates for application in electronic and optical devices.

Abstract

Thirteen N‐butylpyridinium salts, including three monometallic [C4Py]2[MCl4], nine bimetallic [C4Py]2[M1−xaMxbCl4] and one trimetallic compound [C4Py]2[M1−yzaMybMzcCl4] (M=Co, Cu, Mn; x=0.25, 0.50 or 0.75 and y=z=0.33), were synthesized and their structure and thermal and electrochemical properties were studied. All compounds are ionic liquids (ILs) with melting points between 69 and 93 °C. X‐ray diffraction proves that all ILs are isostructural. The conductivity at room temperature is between 10−4 and 10−8 S cm−1. Some Cu‐based ILs reach conductivities of 10−2 S cm−1, which is, however, probably due to IL dec. This correlates with the optical bandgap measurements indicating the formation of large bandgap semiconductors. At elevated temperatures approaching the melting points, the conductivities reach up to 1.47×10−1 S cm−1 at 70 °C. The electrochemical stability windows of the ILs are between 2.5 and 3.0 V.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Christian Balischewski, Karsten Behrens, Kerstin Zehbe, Christina Günter, Stefan Mies, Eric Sperlich, Alexandra Kelling, Andreas Taubert
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003097

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Electron‐Deficient Conjugated Materials via p–π* Conjugation with Boron: Extending Monomers to Oligomers, Macrocycles, and Polymers

Electron‐Deficient Conjugated Materials via p–π* Conjugation with Boron: Extending Monomers to Oligomers, Macrocycles, and Polymers

The development of π‐extended organoboranes is systematically discussed from both theoretical and experimental perspectives. An analysis of the p–π* conjugation and of mutual interactions between electron‐deficient boron centers across π‐conjugated linkers allows for important structure–property relationships to be deduced. It is also illustrated how the unique properties of these boron‐containing π‐conjugated systems are exploited in the field of organic optical and optoelectronic device materials.

Abstract

The extension of conjugated organoboranes from monomeric species to oligomers, macrocycles, and polymers offers access to a plethora of fascinating new materials. The p–π* conjugation between empty orbitals on boron and the conjugated linkers not only affects the electronic structure and optical properties, but also enables mutual interactions between electron‐deficient boron centers. The unique properties of these electron‐deficient π‐conjugated systems are exploited in highly luminescent materials, organic optoelectronic devices, and sensing applications.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xiaodong Yin, Jun Liu, Frieder Jäkle
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003481

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Generation and Identification of the Linear OCBNO and OBNCO Molecules with 24 Valence Electrons

Generation and Identification of the Linear OCBNO and OBNCO Molecules with 24 Valence Electrons

Two of five: Two isomers of five‐atom BCNO2 were synthesized and identified by matrix‐isolation IR spectroscopy and quantum chemical calculations. OCBNO, which is produced by the reaction of boron atoms with CO/NO in solid neon, rearranges to the more stable OBNCO isomer on UV excitation. Bonding analysis indicates that OCBNO is best described by the bonding interactions of triplet‐state B+ and the CO/NO ligands in the triplet state forming two degenerate electron‐sharing π bonds and two ligand‐to‐boron dative σ bonds.

Abstract

Two structural isomers containing five second‐row element atoms with 24 valence electrons were generated and identified by matrix‐isolation IR spectroscopy and quantum chemical calculations. The OCBNO complex, which is produced by the reaction of boron atoms with mixtures of carbon monoxide and nitric oxide in solid neon, rearranges to the more stable OBNCO isomer on UV excitation. Bonding analysis indicates that the OCBNO complex is best described by the bonding interactions between a triplet‐state boron cation with an electron configuration of (2s)0(2pσ)0(2pπ)2 and the CO/NO ligands in the triplet state forming two degenerate electron‐sharing π bonds and two ligand‐to‐boron dative σ bonds.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Guohai Deng, Sudip Pan, Jiaye Jin, Guanjun Wang, Lili Zhao, Mingfei Zhou, Gernot Frenking
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003886

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Understanding the High‐Performance Anode Material of CoC2O4⋅2 H2O Microrods Wrapped by Reduced Graphene Oxide for Lithium‐Ion and Sodium‐Ion Batteries

Understanding the High‐Performance Anode Material of CoC2O4⋅2 H2O Microrods Wrapped by Reduced Graphene Oxide for Lithium‐Ion and Sodium‐Ion Batteries

Metal oxalate nanorods: CoC2O4⋅2 H2O/rGO hybrids with a nanorod structure have superior rate capacity retention and long cycling stability in lithium‐ion batteries. The in situ Raman analysis technique is very powerful for probing the structure and phase composition of the CoC2O4⋅2 H2O/rGO electrode during the charge/discharge process.

Abstract

Metal oxalate has become a most promising candidate as an anode material for lithium‐ion and sodium‐ion batteries. However, capacity decrease owing to the volume expansion of the active material during cycling is a problem. Herein, a rod‐like CoC2O4⋅2 H2O/rGO hybrid is fabricated through a novel multistep solvo/hydrothermal strategy. The structural characteristics of the CoC2O4⋅2 H2O microrod wrapped using rGO sheets not only inhibit the volume variation of the hybrid electrode during cycling, but also accelerate the transfer of electrons and ions in the 3 D graphene network, thereby improving the electrochemical properties of CoC2O4⋅2 H2O. The CoC2O4⋅2 H2O/rGO electrode delivers a specific capacity of 1011.5 mA h g−1 at 0.2 A g−1 after 200 cycles for lithium storage, and a high capacity of 221.1 mA h g−1 at 0.2 A g−1 after 100 cycles for sodium storage. Moreover, the full cell CoC2O4⋅2 H2O/rGO//LiCoO2 consisting of the CoC2O4⋅2 H2O/rGO anode and LiCoO2 cathode maintains 138.1 mA h g−1 after 200 cycles at 0.2 A g−1 and has superior long‐cycle stability. In addition, in situ Raman spectroscopy and in situ and ex situ X‐ray diffraction techniques provide a unique opportunity to understand fully the reaction mechanism of CoC2O4⋅2 H2O/rGO. This work also gives a new perspective and solid research basis for the application of metal oxalate materials in high‐performance lithium‐ion and sodium‐ion batteries.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yingying Zhang, Canpei Wang, Yutao Dong, Ruipeng Wei, Jianmin Zhang
chemistry-europe.onlinelibrary.wiley.com/doi/abs/10.1002/chem.202003309

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