David B

Beryllium Atom Mediated Dinitrogen Activation via Coupling with Carbon Monoxide

Beryllium Atom Mediated Dinitrogen Activation via Coupling with Carbon Monoxide

Beryllium atoms react with dinitrogen and carbon monoxide mixtures to form the end‐on bonded NNBeCO and side‐on bonded (η2‐N2)BeCO complexes, both of which isomerize to the more stable NBeNCO isomer, showing that the activation of N2 with fully cleaved N−N bond can be achieved by coupling with carbon monoxide via a major group atom.

Abstract

The reactions of laser‐ablated beryllium atoms with dinitrogen and carbon monoxide mixtures form the end‐on bonded NNBeCO and side‐on bonded (η2‐N2)BeCO isomers in solid argon, which are predicted by quantum chemical calculations to be almost isoenergetic. The end‐on bonded complex has a triplet ground state while the side‐on bonded isomer has a singlet electronic ground state. The complexes rearrange to the energetically lowest lying NBeNCO isomer upon visible light excitation, which is characterized to be an isocyanate complex of a nitrene derivative with a triplet electronic ground state. A bonding analysis using a charge‐ and energy decomposition procedure reveals that the electronic reference state of Be in the NNBeCO isomers has an 2s02p2 excited configuration and that the metal‐ligand bonds can be described in terms of N2→Be←CO σ donation and concomitant N2←Be→CO π backdonation. The results demonstrate that the activation of N2 with the N−N bond being completely cleaved can be achieved via coupling with carbon monoxide mediated by a main group atom.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Guohai Deng, Sudip Pan, Guanjun Wang, Lili Zhao, Mingfei Zhou, Gernot Frenking
doi.org/10.1002/anie.202007241

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Electrocatalytic CO2 Reduction on CuOx Nanocubes: Tracking the Evolution of Chemical State, Geometric Structure, and Catalytic Selectivity using Operando Spectroscopy

Electrocatalytic CO2 Reduction on CuOx Nanocubes: Tracking the Evolution of Chemical State, Geometric Structure, and Catalytic Selectivity using Operando Spectroscopy

Cu2O cubes of nanometer‐sized dimensions allow the chemical and structural factors that control the selectivity of the CO2 reduction reaction (CO2RR) to be traced. The Faradaic product efficiencies over time can be linked to changes in the chemical state at the surface and bulk and in the catalyst morphology for supported and unsupported nanocubes (S‐NC, U‐NC).

Abstract

The direct electrochemical conversion of carbon dioxide (CO2) into multi‐carbon (C2+) products still faces fundamental and technological challenges. While facet‐controlled and oxide‐derived Cu materials have been touted as promising catalysts, their stability has remained problematic and poorly understood. Herein we uncover changes in the chemical and morphological state of supported and unsupported Cu2O nanocubes during operation in low‐current H‐Cells and in high‐current gas diffusion electrodes (GDEs) using neutral pH buffer conditions. While unsupported nanocubes achieved a sustained C2+ Faradaic efficiency of around 60 % for 40 h, the dispersion on a carbon support sharply shifted the selectivity pattern towards C1 products. Operando XAS and time‐resolved electron microscopy revealed the degradation of the cubic shape and, in the presence of a carbon support, the formation of small Cu‐seeds during the surprisingly slow reduction of bulk Cu2O. The initially (100)‐rich facet structure has presumably no controlling role on the catalytic selectivity, whereas the oxide‐derived generation of under‐coordinated lattice defects, can support the high C2+ product yields.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Tim Möller, Fabian Scholten, Trung Ngo Thanh, Ilya Sinev, Janis Timoshenko, Xingli Wang, Zarko Jovanov, Manuel Gliech, Beatriz Roldan Cuenya, Ana Sofia Varela, Peter Strasser
doi.org/10.1002/anie.202007136

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Intermolecular Dearomatization of Naphthalene Derivatives by Photoredox‐Catalyzed 1,2‐Hydroalkylation

Intermolecular Dearomatization of Naphthalene Derivatives by Photoredox‐Catalyzed 1,2‐Hydroalkylation

The development of dearomative functionalization strategies for arenes is intrinsically challenging and remains a largely unsolved synthetic problem owing to the particularly high resonance energy. We have now developed the first catalytic intermolecular hydroalkylative dearomatization of naphthalene derivatives with commercially available α‐amino acids by a photoredox‐neutral process.

Abstract

An intermolecular hydroalkylative dearomatization of naphthalenes with commercially available α‐amino acids is achieved via visible‐light photoredox catalysis. With an organic photocatalyst, a series of multi‐substituted 1,2‐dihydronaphthalenes are obtained in good‐to‐excellent yields. Intriguingly, by tuning the substituents at the C2 position of naphthalenes, formal dearomative [3+2] cycloadditions occur exclusively via a hydroalkylative dearomatization–cyclization sequence. This overall redox‐neutral method features mild reaction conditions, good tolerance of functionalities, and operational simplicity. Diverse downstream elaborations of the products are demonstrated. Preliminary mechanistic studies suggest the involvement of a radical–radical coupling pathway.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yuan‐Zheng Cheng, Xu‐Lun Huang, Wei‐Hui Zhuang, Qing‐Ru Zhao, Xiao Zhang, Tian‐Sheng Mei, Shu‐Li You
doi.org/10.1002/anie.202008358

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Single‐Molecule Analysis Determines Isozymes of Human Alkaline Phosphatase in Serum

Single‐Molecule Analysis Determines Isozymes of Human Alkaline Phosphatase in Serum

A rapid approach to profile various alkaline phosphatase (ALP) isozymes as important biomarkers in blood via a single‐molecule‐analysis microarray platform is demonstrated.

Abstract

Alkaline phosphatase (ALP) is an important biomarker, as high levels of ALP in blood can indicate liver disease or bone disorders. However, current clinical blood tests only measure the total concentration of ALP but are unable to distinguish enzyme isotypes. Here, we demonstrate a novel and rapid approach to profile various ALP isozymes in blood via a single‐molecule‐analysis platform. The microarray platform provides enzyme kinetics of hundreds of individual molecules at high throughput. Using these single molecule kinetics, we characterize the different activity profiles of ALP isotypes. By analyzing both healthy and disease samples, we found the single molecule activity distribution of ALP in serum reflects the health status of patients. This result demonstrates the potential utility of the method for improving the conventional ALP test, as well as for analyzing other enzymatic biomarkers, including enzyme isotypes.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yu Jiang, Xiang Li, David R. Walt
doi.org/10.1002/anie.202007477

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Functionalization of Zirconium‐Based Metal–Organic Layers with Tailored Pore Environments for Heterogeneous Catalysis

Functionalization of Zirconium‐Based Metal–Organic Layers with Tailored Pore Environments for Heterogeneous Catalysis

A facile one‐pot synthetic strategy was explored to incorporate multiple functionalities into stable zirconium metal–organic layers (MOLs) through the functionalization of Zr6‐BTB (BTB=benzene‐1,3,5‐tribenzoate) layers via secondary ligand pillaring. A metal–phthalocyanine fragment was successfully incorporated into this Zr‐MOL system, giving rise to an ideal platform for the selective oxidation of anthracene.

Abstract

Intriguing properties and functions are expected to implant into metal–organic layers (MOLs) to achieve tailored pore environments and multiple functionalities owing to the synergies among multiple components. Herein, we demonstrate a facile one‐pot synthetic strategy to incorporate multiple functionalities into stable zirconium MOLs via secondary ligand pillaring. Through the combination of Zr6‐BTB (BTB=benzene‐1,3,5‐tribenzoate) layers and diverse secondary ligands (including ditopic and tetratopic linkers), 31 MOFs with multi‐functionalities were systematically prepared. Notably, a metal–phthalocyanine fragment was successfully incorporated into this Zr‐MOL system, giving rise to an ideal platform for the selective oxidation of anthracene. The organic functionalization of two‐dimensional MOLs can generate tunable porous structures and environments, which may facilitate the excellent catalytic performance of as‐synthesized materials.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Guan‐Yu Qiao, Shuai Yuan, Jiandong Pang, Heng Rao, Christina T. Lollar, Dongbin Dang, Jun‐Sheng Qin, Hong‐Cai Zhou, Jihong Yu
doi.org/10.1002/anie.202007781

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Engineering Platinum–Oxygen Dual Catalytic Sites via Charge Transfer towards High‐Efficient Hydrogen Evolution

Engineering Platinum–Oxygen Dual Catalytic Sites via Charge Transfer towards High‐Efficient Hydrogen Evolution

Atomically dispersed Pt embedded in Ti1−xO2 (Pt1O1/Ti1−xO2) was engineered via a cation‐deficient electrostatic anchorage route. The inherent charge transfer within the Pt−O realm thus evolved the catalytic matrix into the dual Pt−OPt catalytic sites towards high‐efficient and durable hydrogen evolution.

Abstract

A dual‐site catalyst allows for a synergetic reaction in the close proximity to enhance catalysis. It is highly desirable to create dual‐site interfaces in single‐atom system to maximize the effect. Herein, we report a cation‐deficient electrostatic anchorage route to fabricate an atomically dispersed platinum–titania catalyst (Pt1O1/Ti1−xO2), which shows greatly enhanced hydrogen evolution activity, surpassing that of the commercial Pt/C catalyst in mass by a factor of 53.2. Operando techniques and density functional calculations reveal that Pt1O1/Ti1−xO2 experiences a Pt−O dual‐site catalytic pathway, where the inherent charge transfer within the dual sites encourages the jointly coupling protons and plays the key role during the Volmer–Tafel process. There is almost no decay in the activity of Pt1O1/Ti1−xO2 over 300 000 cycles, meaning 30 times of enhancement in stability compared to the commercial Pt/C catalysts (10 000 cycles).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Fei Lu, Ding Yi, Shoujie Liu, Fei Zhan, Bo Zhou, Lin Gu, Dmitri Golberg, Xi Wang, Jiannian Yao
doi.org/10.1002/anie.202008117

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NiMn‐Based Bimetal–Organic Framework Nanosheets Supported on Multi‐Channel Carbon Fibers for Efficient Oxygen Electrocatalysis

NiMn‐Based Bimetal–Organic Framework Nanosheets Supported on Multi‐Channel Carbon Fibers for Efficient Oxygen Electrocatalysis

NiMn‐based bimetal–organic framework nanosheets are successfully grown on multi‐channel carbon fibers (MCCF/NiMn‐MOFs) as a promising bifunctional oxygen electrocatalyst. The strong synergetic effect of bimetallic nodes as well as the well‐designed hierarchical architecture is unraveled to enable MCCF/NiMn‐MOFs with fast kinetics and robust stability towards efficient oxygen electrocatalysis.

Abstract

Developing noble‐metal‐free bifunctional oxygen electrocatalysts is of great significance for energy conversion and storage systems. Herein, we have developed a transformation method for growing NiMn‐based bimetal–organic framework (NiMn‐MOF) nanosheets on multi‐channel carbon fibers (MCCF) as a bifunctional oxygen electrocatalyst. Owing to the desired components and architecture, the MCCF/NiMn‐MOFs manifest comparable electrocatalytic performance towards oxygen reduction reaction (ORR) with the commercial Pt/C electrocatalyst and superior performance towards oxygen evolution reaction (OER) to the benchmark RuO2 electrocatalyst. X‐ray absorption fine structure (XAFS) spectroscopy and density functional theory (DFT) calculations reveal that the strong synergetic effect of adjacent Ni and Mn nodes within MCCF/NiMn‐MOFs effectively promotes the thermodynamic formation of key *O and *OOH intermediates over active NiO6 centers towards fast ORR and OER kinetics.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Weiren Cheng, Xue Feng Lu, Deyan Luan, Xiong Wen (David) Lou
doi.org/10.1002/anie.202008129

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Solvation Rule for Solid‐Electrolyte Interphase Enabler in Lithium‐Metal Batteries

Solvation Rule for Solid‐Electrolyte Interphase Enabler in Lithium‐Metal Batteries

Fluoroethylene carbonate can form a robust solid‐electrolyte interphase (SEI) on the lithium metal surface. Using fluoroethylene carbonate as the SEI enabler allows relatively stable lithium‐metal battery (LMB) cycling. The solvation number of fluoroethylene carbonate must be greater than or equal to 1 to ensure the formation of a stable SEI.

Abstract

Despite the exceptionally high energy density of lithium metal anodes, the practical application of lithium‐metal batteries (LMBs) is still impeded by the instability of the interphase between the lithium metal and the electrolyte. To formulate a functional electrolyte system that can stabilize the lithium‐metal anode, the solvation behavior of the solvent molecules must be understood because the electrochemical properties of a solvent can be heavily influenced by its solvation status. We unambiguously demonstrated the solvation rule for the solid‐electrolyte interphase (SEI) enabler in an electrolyte system. In this study, fluoroethylene carbonate was used as the SEI enabler due to its ability to form a robust SEI on the lithium metal surface, allowing relatively stable LMB cycling. The results revealed that the solvation number of fluoroethylene carbonate must be ≥1 to ensure the formation of a stable SEI in which the sacrificial reduction of the SEI enabler subsequently leads to the stable cycling of LMBs.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Chi‐Cheung Su, Meinan He, Jiayan Shi, Rachid Amine, Jian Zhang, Khalil Amine
doi.org/10.1002/anie.202008081

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Interfacially Bridging Covalent Network Yields Hyperstable and Ultralong Virus‐Based Fibers for Engineering Functional Materials

Interfacially Bridging Covalent Network Yields Hyperstable and Ultralong Virus‐Based Fibers for Engineering Functional Materials

A strategy to interfacially bridge a covalent network within tobacco mosaic virus (TMV) virus‐like particles (VLPs) is presented. T103C‐TMV‐E50C‐A74C shows the highest robustness in assembly capability and structural stability with the largest length for a TMV VLP to date. The robust nature of this TMV VLP allows for reducer‐free synthesis of excellent electrocatalysts for application in harshly alkaline hydrogen evolution.

Abstract

We present a strategy of interfacially bridging covalent network within tobacco mosaic virus (TMV) virus‐like particles (VLPs). We arranged T103C cysteine to laterally conjugate adjacent subunits. In the axis direction, we set A74C mutation and systematically investigated candidate from E50C to P54C as the other thiol function site, for forming longitudinal disulfide bond chains. Significantly, the T103C‐TMV‐E50C‐A74C shows the highest robustness in assembly capability and structural stability with the largest length, for TMV VLP to date. The fibers with lengths from several to a dozen of micrometers even survive under pH 13. The robust nature of this TMV VLP allows for reducer‐free synthesis of excellent electrocatalysts for application in harshly alkaline hydrogen evolution.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Kun Zhou, Yihao Zhou, Hongchao Yang, Huile Jin, Yonggang Ke, Qiangbin Wang
doi.org/10.1002/anie.202008670

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Atom Exchange Versus Reconstruction: (GexAs4−x)x− (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6(Ge3As)(Ge2As2)3]3−

Atom Exchange Versus Reconstruction: (GexAs4−x)x− (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6(Ge3As)(Ge2As2)3]3−

Two types of intermetalloid cluster architectures are obtained from reactions of binary Zintl anions (Tt2Pn2)2− (Tt=Ge, Sn, Pb; Pn=As, Sb, Bi) with [(PPh3)AuMe], as described by S. Dehnen et al. in their Research Article (DOI: doi.org/10.1002/anie.20200810810.1002/anie.202008108): while combinations of heavier atoms lead to reconstruction of the binary precursor to form {[AuTt5Pn3]2}4− (take a left turn), the lightest homologue yields [Au6(Ge3As)(Ge2As2)3]3− with a new supertetrahedral Zintl cluster architecture (take a right turn) upon an atom exchange reaction that was rationalized by DFT calculations.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Fuxing Pan, Lukas Guggolz, Florian Weigend, Stefanie Dehnen
doi.org/10.1002/anie.202010490

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Synthesis of Robust MOFs@COFs Porous Hybrid Materials via an Aza‐Diels–Alder Reaction: Towards High‐Performance Supercapacitor Materials

Synthesis of Robust MOFs@COFs Porous Hybrid Materials via an Aza‐Diels–Alder Reaction: Towards High‐Performance Supercapacitor Materials

The functional porous hybrid material aza‐MOF@COF is synthesised through post‐synthesis modification of MOF@COF‐LZU1 by a cycloaddition‐based aza‐Diels–Alder reaction. The aza‐MOF@COF exhibit exhibits high specific capacitance of 20.35 μF cm−2 and an exceptional stack capacitance of 1.16 F cm−3.

Abstract

Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have attracted enormous attention in recent years. Recently, MOF@COF are emerging as hybrid architectures combining the unique features of the individual components to enable the generation of materials displaying novel physicochemical properties. Herein we report an unprecedented use of aza‐Diels–Alder cycloaddition reaction as post‐synthetic modification of MOF@COF‐LZU1, to generate aza‐MOFs@COFs hybrid porous materials with extended π‐delocalization. A a proof‐of‐concept, the obtained aza‐MOFs@COFs is used as electrode in supercapacitors displaying specific capacitance of 20.35 μF cm−2 and high volumetric energy density of 1.16 F cm−3. Our approach of post‐synthetic modification of MOFs@COFs hybrids implement rational design for the synthesis of functional porous materials and expands the plethora of promising application of MOFs@COFs hybrid porous materials in energy storage applications.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Haijun Peng, Jésus Raya, Fanny Richard, Walid Baaziz, Ovidiu Ersen, Artur Ciesielski, Paolo Samorì
doi.org/10.1002/anie.202008408

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Controlling the Product Platform of Carbon Dioxide Reduction: Adaptive Catalytic Hydrosilylation of CO2 Using a Molecular Cobalt(II) Triazine Complex

Controlling the Product Platform of Carbon Dioxide Reduction: Adaptive Catalytic Hydrosilylation of CO2 Using a Molecular  Cobalt(II) Triazine Complex

Organometallic treasure hunt: A molecular cobalt catalyst “navigates” the CO2 reduction with phenylsilanes to arrive at each product level individually with high selectivity and activity. This demonstrates the possibility of developing adaptive catalytic systems for the use of carbon dioxide as raw material for chemicals or energy carriers, as detailed by C. Werlé, W. Leitner et al. in their Research Article (DOI: doi.org/10.1002/anie.20200446310.1002/anie.202004463).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Hanna H. Cramer, Basujit Chatterjee, Thomas Weyhermüller, Christophe Werlé, Walter Leitner
doi.org/10.1002/anie.202010500

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Integrating Time‐Resolved Imaging Information by Single‐Luminophore Dual Thermally Activated Delayed Fluorescence

Integrating Time‐Resolved Imaging Information by Single‐Luminophore Dual Thermally Activated Delayed Fluorescence

Single‐luminophore dual thermally activated delayed fluorescence properties were utilized for integrating time‐resolved imaging information. The “planets” in the artwork illustrate biological cells or units of life—the biological microenvironment resembles a cosmic space with countless unknown entities, waiting to be explored by molecular probes with different emission signals. More information can be found in the Research Article by X. Wang, L. Zhu et al. (DOI: doi.org/10.1002/anie.20200907710.1002/anie.202009077).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Mengkai Luo, Xuping Li, Longjiang Ding, Gleb Baryshnikov, Shen Shen, Mingjie Zhu, Lulu Zhou, Man Zhang, Jianjun Lu, Hans Ågren, Xu‐Dong Wang, Liangliang Zhu
doi.org/10.1002/anie.202010498

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Bench‐Stable S‐(Monofluoromethyl)sulfonium Salts: Highly Efficient C‐ and O‐Regioselective Monofluoromethylation of 1,3‐Dicarbonyl Compounds

Bench‐Stable S‐(Monofluoromethyl)sulfonium Salts: Highly Efficient C‐ and O‐Regioselective Monofluoromethylation of 1,3‐Dicarbonyl Compounds

Novel bench‐stable S‐(monofluoromethyl)‐S‐phenyl‐S‐(2,4,6‐trialkoxyphenyl)sulfonium salts were readily prepared for C‐ and O‐regioselective monofluoromethylation of 1,3‐dicarbonyl compounds in good to excellent yields under mild reaction conditions.

The new bench‐stable electrophilic monofluoromethylating reagents, S‐(monofluoromethyl)‐S‐phenyl‐S‐(2,4,6‐trialkoxyphenyl)sulfonium salts, were successfully developed, which were readily prepared from inexpensive starting materials 1,3,5‐trimethoxybenzene and monofluoromethyl phenyl sulfoxides. The reactivity of these reagents was demonstrated through the C‐ and O‐regioselective monofluoromethylation of 1,3‐dicarbonyl compounds. Employing this reagent, a wide range of β‐keto esters easily underwent O‐regioselective monofluoromethylation reaction to afford their corresponding O‐monofluoromethylated products in good to excellent yields under mild reaction conditions. Contrastively, various malonates were smoothly transferred into their corresponding C‐monofluoromethylated products in good to excellent yields under the standard reaction conditions.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Wen‐Bing Qin, Jian‐Jian Liu, Zhongyan Huang, Xin Li, Wei Xiong, Jia‐Yi Chen, Guo‐Kai Liu
doi.org/10.1002/ejoc.202000998

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PhI(OAc)2‐Promoted 1,2‐Diaza‐Cope Rearrangement of β,γ‐Unsaturated Hydrazones with Acetate/H2O: Access to Diacyl/Acyl N‐Allylhydrazines

PhI(OAc)2‐Promoted 1,2‐Diaza‐Cope Rearrangement of β,γ‐Unsaturated Hydrazones with Acetate/H2O: Access to Diacyl/Acyl N‐Allylhydrazines

A novel metal‐free methodology for the synthesis of diacyl/acyl N‐allylhydrazines based on PhI(OAc)2‐promoted 1,2‐diaza‐Cope rearrangement reaction of β,γ‐unsaturated hydrazones with acetate/H2O has been described. This cascade reaction works efficiently and features good substrate tolerance under mild conditions. A possible mechanism involving hydrazonyl radicals and N–I(III) intermediates of β,γ‐unsaturated hydrazones is proposed.

A novel metal‐free methodology for the synthesis of diacyl/acyl N‐allylhydrazines based on PhI(OAc)2‐promoted 1,2‐diaza‐Cope rearrangement reaction of β,γ‐unsaturated hydrazones with acetate/H2O has been described. This cascade reaction works efficiently under mild conditions. A possible mechanism involving hydrazonyl radicals and N–I(III) intermediates of β,γ‐unsaturated hydrazones is proposed.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Zhuo‐Yue Fang, Lin Qi, Jin‐Yan Song, Pei‐Xing Ren, Cong‐Ying Hou, Shi‐Chao Ji, Li‐Jing Wang, Wei Li
doi.org/10.1002/ejoc.202000875

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Modulation of Self‐Separating Molecular Catalysts for Highly Efficient Biomass Transformations

Modulation of Self‐Separating Molecular Catalysts for Highly Efficient Biomass Transformations

Self‐isolating catalyst: The covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (‐SO3H) is reported by grafting sulfonic acid groups on the POM’s surface followed by oxidation of (3‐mercaptopropyl)trimethoxysilane. The acidity of TBA6‐P2W17‐SO3H (TBA=tetrabutyl ammonium) has been demonstrated by 31P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes, during which it self‐separates from the mixture to enable recovery.

Abstract

The energetically viable fabrication of stable and highly efficient solid acid catalysts is one of the key steps in large‐scale transformation processes of biomass resources. Herein, the covalent modification of the classical Dawson polyoxometalate (POMs) with sulfonic acids (‐SO3H) is reported by grafting sulfonic acid groups on the POM’s surface followed by oxidation of (3‐mercaptopropyl)trimethoxysilane. The acidity of TBA6‐P2W17‐SO3H (TBA=tetrabutyl ammonium) has been demonstrated by using 31P NMR spectroscopy, clearly indicating the presence of strong Brønsted acid sites. The presence of TBA counterions renders the solid acid catalyst as a promising candidate for phase transfer catalytic processes. The TBA6‐P2W17‐SO3H shows remarkable activity and selectivity, excellent stability, and great substrate compatibility for the esterification of free fatty acids (FFA) with methanol and conversion into biodiesel at 70 °C with >98 % conversion of oleic acid in 20 min. The excellent catalytic performance can be attributed to the formation of a catalytically active emulsion, which results in a uniform catalytic behavior during the reaction, leading to efficient interaction between the substrate and the active sites of the catalyst. Most importantly, the catalyst can be easily recovered and reused without any loss of its catalytic activity owing to its excellent phase transfer properties. This work offers an efficient and cost‐effective strategy for large‐scale biomass conversion applications.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Lifei Lian, Xiang Chen, Xianfeng Yi, Yubing Liu, Wei Chen, Anmin Zheng, Haralampos N. Miras, Yu‐Fei Song
doi.org/10.1002/chem.202001451

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A Cationic NHC‐Supported Borole

A Cationic NHC‐Supported Borole

Think positive! Halide abstraction from an NHC‐adduct to a haloborole allowed for the synthesis of the first cationic borole featuring a three‐coordinate boron‐atom embedded in a cyclic 4π electron system. This cation reveals high boron‐centered Lewis‐acidity and a very small reduction potential. CO readily and reversibly binds to the boron‐center to form a rare carbonyl complex with considerably low stretching frequency that indicates backbonding.

Abstract

This work describes the synthesis and characterization of a highly reactive cationic borole. Halide abstraction with Li{Al[OC(CF3)3]4} from the NHC‐chloroborole adduct yields the first stable NHC‐supported 1‐(MeNHC)‐2,5‐(SiMe3)2‐3,4‐(Ph*)2‐borole cation. Electronically, it features both a five‐membered cyclic conjugated 4 π‐electron system and a cationic charge and thus resembles the yet elusive cyclopentadienyl cation. The borole cation was characterized crystallographically, spectroscopically (NMR, UV/Vis), by cyclovoltammetry, microanalysis and mass‐spectrometry and its electronic structure was probed computationally. The cation reacts with tolane and reversibly binds carbon monoxide. Direct comparison with the structurally related, yet neutral, 1‐mesityl borole reveals strong Lewis acidity, reduced HOMO–LUMO gaps, and increased anti‐aromatic character.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Tobias Heitkemper, Christian P. Sindlinger
doi.org/10.1002/chem.202001916

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Enhancing Tris(pyrazolyl)borate‐Based Models of Cysteine/Cysteamine Dioxygenases through Steric Effects: Increased Reactivities, Full Product Characterization and Hints to Initial Superoxide Formation

Enhancing Tris(pyrazolyl)borate‐Based Models of Cysteine/Cysteamine Dioxygenases through Steric Effects: Increased Reactivities, Full Product Characterization and Hints to Initial Superoxide Formation

More space through more bulk at the residues of a trispyrazolylborato coligand is the secret to advancing cysteine and cysteamine dioxygenase modeling chemistry. Reaction rates are significantly increased and for the first time also the reaction products could be crystallized, leading to the first structural characterization of a sulfinate with biomimetic η2‐O,O‐binding mode of the SO2 groups. Increasing the space around the iron center even more led at low temperatures to the detection of an intermediate, which by comparison with an analogous cobalt series was assigned as an iron(II) superoxide species.

Abstract

The design of biomimetic model complexes for the cysteine dioxygenase (CDO) and cysteamine dioxygenase (ADO) is reported, where the 3‐His coordination of the iron ion is simulated by three pyrazole donors of a trispyrazolyl borate ligand (Tp) and protected cysteine and cysteamine represent substrate ligands. It is found that the replacement of phenyl groups—attached at the 3‐positions of the pyrazole units in a previous model—by mesityl residues has massive consequences, as the latter arrange to a more spacious reaction pocket. Thus, the reaction with O2 proceeds much faster and afterwards the first structural characterization of an iron(II) η2O,O‐sulfinate product became possible. If one of the three Tp‐mesityl groups is placed in the 5‐position, an even larger reaction pocket results, which leads to yet faster rates and accumulation of a reaction intermediate at low temperatures, as shown by UV/Vis and Mössbauer spectroscopy. After comparison with the results of investigations on the cobalt analogues this intermediate is tentatively assigned to an iron(III) superoxide species.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Lars Müller, Santina Hoof, Matthias Keck, Christian Herwig, Christian Limberg
doi.org/10.1002/chem.202001818

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Rationalizing the AlI‐Promoted Oxidative Addition of C−C Versus C−H Bonds in Arenes

Rationalizing the AlI‐Promoted Oxidative Addition of C−C Versus C−H Bonds in Arenes

A C−C or a C−H bond? In this work, the competition between oxidative additions of C−C vs. C−H bonds in different arenes promoted by the AlI‐carbenoid shown in the figure is explored. Whereas larger arenes (naphthalene, anthracene) lead to C−H activation products, the C−C bond is preferred in the process involving benzene. State‐of‐the‐art computational tools are used to quantitatively rationalize these reactivity trends.

Abstract

The factors controlling the oxidative addition of C−C and C−H bonds in arenes mediated by AlI have been computationally explored by means of Density Functional Theory calculations. To this end, we compared the processes involving benzene, naphthalene and anthracene which are promoted by a recently prepared anionic AlI‐carbenoid. It is found that this species exhibits a strong tendency to oxidatively activate C−H bonds over C−C bonds, with the notable exception of benzene, where the C−C bond activation is feasible but only under kinetic control reaction conditions. State‐of‐the‐art computational methods based on the combination of the Activation Strain Model of reactivity and the Energy Decomposition Analysis have been used to rationalize the competition between both bond activation reactions as well as to quantitatively analyze in detail the ultimate factors controlling these transformations.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jorge Juan Cabrera‐Trujillo, Israel Fernández
doi.org/10.1002/chem.202000921

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The First Use of a ReX5 Synthon to Modulate FeIII Spin Crossover via Supramolecular Halogen⋅⋅⋅Halogen Interactions

The First Use of a ReX5 Synthon to Modulate FeIII Spin Crossover via Supramolecular Halogen⋅⋅⋅Halogen Interactions

Inorganic synthon controls SCO behavior: Incorporating an {ReIVX5} synthon into an FeIII system provides a highly directional supramolecular design using halogen⋅⋅⋅halogen interactions. Removal of solvent from the crystal lattice “switches on” these interactions, providing a long‐range cooperative pathway ideal for an SCO event.

Abstract

We have added the {ReIVX5} (X=Br, Cl) synthon to a pocket‐based ligand to provide supramolecular design using halogen⋅⋅⋅halogen interactions within an FeIII system that has the potential to undergo spin crossover (SCO). By removing the solvent from the crystal lattice, we “switch on” halogen⋅⋅⋅halogen interactions between neighboring molecules, providing a supramolecular cooperative pathway for SCO. Furthermore, changes to the halogen‐based interaction allow us to modify the temperature and nature of the SCO event.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Rebecca Busch, Anthony B. Carter, Konstantis F. Konidaris, Irina A. Kühne, Ricardo González, Christopher E. Anson, Annie K. Powell
doi.org/10.1002/chem.202001668

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Binding Site Switch by Dispersion Interactions: Rotational Signatures of Fenchone–Phenol and Fenchone–Benzene Complexes

Binding Site Switch by Dispersion Interactions: Rotational Signatures of Fenchone–Phenol and Fenchone–Benzene Complexes

Time to switch! The interplay between hydrogen‐bonding and dispersion interactions has been investigated though the study of complexes of the odorant fenchone with phenol and benzene, mimics of tyrosine and phenylalanine residues, respectively. Two isomers of each complex have been characterised by rotational spectroscopy (see figure). The increased contribution of dispersion interactions in these complexes is responsible for a change in the preferred binding site in fenchone.

Abstract

Non‐covalent interactions between molecules determine molecular recognition and the outcome of chemical and biological processes. Characterising how non‐covalent interactions influence binding preferences is of crucial importance in advancing our understanding of these events. Here, we analyse the interactions involved in smell and specifically the effect of changing the balance between hydrogen‐bonding and dispersion interactions by examining the complexes of the common odorant fenchone with phenol and benzene, mimics of tyrosine and phenylalanine residues, respectively. Using rotational spectroscopy and quantum chemistry, two isomers of each complex have been identified. Our results show that the increased weight of dispersion interactions in these complexes changes the preferred binding site in fenchone and sets the basis for a better understanding of the effect of different residues in molecular recognition and binding events.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Ecaterina Burevschi, Elena R. Alonso, M. Eugenia Sanz
doi.org/10.1002/chem.202001713

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Light‐Activated Carbon Monoxide Prodrugs Based on Bipyridyl Dicarbonyl Ruthenium(II) Complexes

Light‐Activated Carbon Monoxide Prodrugs Based on Bipyridyl Dicarbonyl Ruthenium(II) Complexes

Bright and harmful: A BODIPY dye has been connected to a bipyridyl dicarbonyl ruthenium(II) complex by the Staudinger ligation. The cellular uptake of the complex can be monitored by its green fluorescence. Exposure to UV light induced quick monodecarbonylation accompanied by cell damage.

Abstract

Two photoactivatable dicarbonyl ruthenium(II) complexes based on an amide‐functionalised bipyridine scaffold (4‐position) equipped with an alkyne functionality or a green‐fluorescent BODIPY (boron‐dipyrromethene) dye have been prepared and used to investigate their light‐induced decarbonylation. UV/Vis, FTIR and 13C NMR spectroscopies as well as gas chromatography and multivariate curve resolution alternating least‐squares analysis (MCR‐ALS) were used to elucidate the mechanism of the decarbonylation process. Release of the first CO molecule occurs very quickly, while release of the second CO molecule proceeds more slowly. In vitro studies using two cell lines A431 (human squamous carcinoma) and HEK293 (human embryonic kidney cells) have been carried out in order to characterise the anti‐proliferative and anti‐apoptotic activities. The BODIPY‐labelled compound allows for monitoring the cellular uptake, showing fast internalisation kinetics and accumulation at the endoplasmic reticulum and mitochondria.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Stepan Geri, Tereza Krunclova, Olga Janouskova, Jiri Panek, Martin Hruby, Daniel Hernández‐Valdés, Benjamin Probst, Roger A. Alberto, Constantin Mamat, Manja Kubeil, Holger Stephan
doi.org/10.1002/chem.202002139

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A Systems Approach to a One‐Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode

A Systems Approach to a One‐Pot Electrochemical Wittig Olefination Avoiding the Use of Chemical Reductant or Sacrificial Electrode

Fully electrified: For the first time, a electrochemical system for a one‐pot Wittig olefination reaction (WOR) is reported, which includes a very efficient recycling of triphenylphosphine from triphenylphosphine oxide waste and subsequent carbonyl olefinations through in situ base‐free Wittig ylide formation, avoiding chemical reductants or sacrificial electrodes.

Abstract

An unprecedented one‐pot fully electrochemically driven Wittig olefination reaction system without employing a chemical reductant or sacrificial electrode material to regenerate triphenylphosphine (TPP) from triphenylphosphine oxide (TPPO) and base‐free in situ formation of Wittig ylides, is reported. Starting from TPPO, the initial step of the phosphoryl P=O bond activation proceeds through alkylation with RX (R=Me, Et; X=OSO2CF3 (OTf)), affording the corresponding [Ph3POR]+X salts which undergo efficient electroreduction to TPP in the presence of a substoichiometric amount of the Sc(OTf)3 Lewis acid on a Ag‐electrode. Subsequent alkylation of TPP affords Ph3PR+ which enables a facile and efficient electrochemical in situ formation of the corresponding Wittig ylide under base‐free condition and their direct use for the olefination of various carbonyl compounds. The mechanism and, in particular, the intriguing role of Sc3+ as mediator in the TPPO electroreduction been uncovered by density functional theory calculations.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Biswarup Chakraborty, Arseni Kostenko, Prashanth W. Menezes, Matthias Driess
doi.org/10.1002/chem.202001654

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Unraveling the Beneficial Microstructure Evolution in Pyrite for Boosted Lithium Storage Performance

Unraveling the Beneficial Microstructure Evolution in Pyrite for Boosted Lithium Storage Performance

Improving Li storage: An evident enhancement in lithium storage performances is realized in MoS2‐modified pyrite FeS2. Synchrotron X‐ray techniques and electrochemical tests monitor the beneficial microstructure evolution, which is responsible for the origin of the improved performances. The in situ formed metallic Mo can effectively prevent the coarsening of Fe0 and improve the Li+ diffusion and electron transport in the electrode.

Abstract

Pyrite FeS2 as a high‐capacity electrode material for lithium‐ion batteries (LIBs) is hindered by its unstable cycling performance owing to the large volume change and irreversible phase segregation from coarsening of Fe. Here, the beneficial microstructure evolution in MoS2‐modified FeS2 is unraveled during the cycling process; the microstructure evolution is responsible for its significantly boosted lithium storage performance, making it suitable for use as an anode for LIBs. Specifically, the FeS2/MoS2 displays a long cycle life with a capacity retention of 116 % after 600 cycles at 0.5 A g−1, which is the best among the reported FeS2‐based materials so far. A series of electrochemical tests and structural characterizations substantially revealed that the introduced MoS2 in FeS2 experiences an irreversible electrochemical reaction and thus the in situ formed metallic Mo could act as the conductive buffer layer to accelerate the dynamics of Li+ diffusion and electron transport. More importantly, it can guarantee the highly reversible conversion in lithiated FeS2 by preventing Fe coarsening. This work provides a fundamental understanding and an effective strategy towards the microstructure evolution for boosting lithium storage performances for other metal sulfide‐based materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jie Wang, Jinwen Qin, Yan Jiang, Baoguang Mao, Xin Wang, Minhua Cao
doi.org/10.1002/chem.202001695

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Dinuclear Complexes of Flexidentate Pyridine‐Substituted Formazanate Ligands

Dinuclear Complexes of Flexidentate Pyridine‐Substituted Formazanate Ligands

Coordination modes: Flexidentate pyridine‐substituted ligand designs allow facile and modular assembly of dinuclear coordination compounds scaffolded with redox‐active formazanate bridging ligands. A series of dinuclear complexes of platinum and iridium are described, with a variety of ligand binding modes observed (see figure).

Abstract

The utility of flexidentate pyridyl‐substituted formazanate ligands for assembling dinuclear coordination complexes with iridium(III) and/or platinum(II) building blocks is demonstrated herein. The dinuclear complexes are prepared either via a stepwise strategy, adding one metal unit at a time, or via one‐pot self‐assembly. Eight of the new complexes, including both mononuclear precursors and dinuclear products, are structurally characterized by single‐crystal X‐ray diffraction and NMR spectroscopy, revealing several distinct binding modes of the formazanates. All complexes are characterized by UV/Vis absorption spectroscopy and cyclic voltammetry. The frontier orbitals are primarily localized on the formazanate ligand, and a characteristic, intense formazanate‐centered π→π* absorption band is observed in the absorption spectra.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Ge Mu, Chenggang Jiang, Thomas S. Teets
doi.org/10.1002/chem.202002351

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