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Modifiers versus Channels: Creating Shape‐Selective Catalysis of Metal Nanoparticles/Porous Nanomaterials

Par / 10 novembre 2020 / Non classé
Modifiers versus Channels: Creating Shape‐Selective Catalysis of Metal Nanoparticles/Porous Nanomaterials

A modifier strategy is utilized to create shape selectivity in metal nanoparticle/porous nanomaterial with regular/irregular pore structures by intentionally poisoning certain MNPs. The strategy of flexibly matching different MNPs and corresponding modifiers could be extended to various catalytic systems such as selective hydrogenation and selective oxidation reactions.

Abstract

Shape‐selective catalysis plays a key role in chemical synthesis. Porous nanomaterials with uniform pore structures are ideal supports for metal nanoparticles (MNPs) to generate efficient shape‐selective catalysis. However, many commercial irregular porous nanomaterials face the challenge to realize satisfactory shape selectivity due to the lack of molecular sieving structures. Herein, we report a concept of creating shape selectivity in MNPs/porous nanomaterials through intentionally poisoning certain MNPs using suitable modifiers. The remaining MNPs within the substrates can cooperate with the channels to generate selectivity. Such a strategy not only applies to regular porous nanomaterials (such as MOFs, zeolites) but also extended to irregular porous nanomaterials (such as active carbon, P25). Potentially, the matching among different MNPs, corresponding modifiers, and porous nanomaterials makes our strategy promising in selective catalytic systems.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Chuanzhen Fang, Liwei Liu, Jiena Weng, Suoying Zhang, Xinglong Zhang, Zhen Ren, Yu Shen, Fanchen Meng, Bing Zheng, Sheng Li, Jiansheng Wu, Wenxiong Shi, Sungsik Lee, Weina Zhang, Fengwei Huo
doi.org/10.1002/anie.202011866

Photo‐Effect on Ion Transport in Mixed Cation and Halide Perovskites and Implications for Photo‐Demixing**

Par / 10 novembre 2020 / Non classé
Photo‐Effect on Ion Transport in Mixed Cation and Halide Perovskites and Implications for Photo‐Demixing**

The photo‐effect on ion conduction in mixed cation and halide perovskites is studied. Unlike A‐site substitution, anion replacement is of great influence. In I‐Br mixtures the differences in hole localization and defect formation favor (reversible) photo‐demixing (the situation in the right part is simplified as the interstitial neutral iodine is further stabilized by ionic rearrangement, and the hole in the bromide is delocalized over several regular anions).

Abstract

Lead halide perovskites are considered to be most promising photovoltaic materials. Highest efficiency and improved stability of perovskite solar cells have been achieved by using cation and anion mixtures. Experimental information on electronic and ionic charge carriers is key to evaluate device performance, as well as processes of photo‐decomposition and photo‐demixing which are observed in these materials. Here, we measure ionic and electronic transport properties and investigate various cation and anion substitutions with a special eye on their photo‐ionic effect, following our previous study on CH3NH3PbI3, where we found that light enhances not only electronic but also ionic conductivities. We find that this phenomenon is very sensitive to the nature of the halide, while the cationic substitutions are less relevant. Based on the observation that the ionic conductivity enhancement found for iodide perovskites is significantly weakened by bromide substitution, we provide a chemical rationale for the photo‐demixing in mixed halide compositions.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Gee Yeong Kim, Alessandro Senocrate, Ya‐Ru Wang, Davide Moia, Joachim Maier
doi.org/10.1002/anie.202005853

H2‐Free Re‐Based Catalytic Dehydroxylation of Aldaric Acid to Muconic and Adipic Acid Esters

Par / 10 novembre 2020 / Non classé
H2‐Free Re‐Based Catalytic Dehydroxylation of Aldaric Acid to Muconic and Adipic Acid Esters

In the present work, the conversion of bio‐based aldaric acids into muconic and adipic acid through a heterogeneous catalytic process, in the absence of corrosive reagents or gaseous H2 is reported. The mechanism of the selective removal of adjacent OH* groups on Re/C catalysts and the role of (m)ethanol in carboxylic group protection and hydrogen transfer in a slurry reactor are elucidated by DFT calculations and XPS, chemisorption, and HR‐TEM.

Abstract

As one of the most demanded dicarboxylic acids, adipic acid can be directly produced from renewable sources. Hexoses from (hemi)cellulose are oxidized to aldaric acids and subsequently catalytically dehydroxylated. Hitherto performed homogeneously, we present the first heterogeneous catalytic process for converting an aldaric acid into muconic and adipic acid. The contribution of leached Re from the solid pre‐reduced catalyst was also investigated with hot‐filtration test and found to be inactive for dehydroxylation. Corrosive or hazardous (HBr/H2) reagents are avoided and simple alcohols and solid Re/C catalysts in an inert atmosphere are used. At 120 °C, the carboxylic groups are protected by esterification, which prevents lactonization in the absence of water or acidic sites. Dehydroxylation and partial hydrogenation yield monohexenoates (93 %). For complete hydrogenation to adipate, a 16 % higher activation barrier necessitates higher temperatures.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Brigita Hočevar, Anže Prašnikar, Matej Huš, Miha Grilc, Blaž Likozar
doi.org/10.1002/anie.202010035

Cobalt(III)‐Catalyzed Enantioselective Intermolecular Carboamination by C−H Functionalization

Par / 10 novembre 2020 / Non classé
Cobalt(III)‐Catalyzed Enantioselective Intermolecular Carboamination by C−H Functionalization

Chiral CpxCoIII complexes are efficient catalysts for the intermolecular highly enantioselective carboamination of alkenes. The process is enabled by C−H activation of N‐phenoxyamides and can convert acrylates and bicyclic olefins to valuable isotyrosine derivatives and elaborated amino‐substituted bicycles under mild conditions.

Abstract

High‐valent cyclopentadienyl cobalt catalysis is a versatile tool for sustainable C−H bond functionalizations. To harness the full potential of this strategy, control of the stereoselectivity of these processes is necessary. Herein, we report highly enantioselective intermolecular carboaminations of alkenes through C−H activation of N‐phenoxyamides catalyzed by CoIII‐complexes equipped with chiral cyclopentadienyl (Cpx) ligands. The method converts widely available acrylates as well as bicyclic olefins into attractive enantioenriched isotyrosine derivatives as well as elaborated amino‐substituted bicyclic scaffolds under very mild conditions. The outlined reactivity is unique to the CpxCoIII complexes and is complementary to the reactivity of 4d‐ and 5d‐ precious‐metal catalysts.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Kristers Ozols, Shunsuke Onodera, Łukasz Woźniak, Nicolai Cramer
doi.org/10.1002/anie.202011140

Molecular Complexes Featuring Unsupported Dispersion-Enhanced Aluminum–Copper and Gallium–Copper Bonds

Par / 10 novembre 2020 / Non classé

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Kristian L. Mears, Cary R. Stennett, Elina K. Taskinen, Caroline E. Knapp, Claire J. Carmalt, Heikki M. Tuononen, and Philip P. Power
feedproxy.google.com/~r/acs/jacsat/~3/qLcVmk246wg/jacs.0c10099

Synthesis of 1,2-Amino Alcohols by Photoredox-Mediated Decarboxylative Coupling of α-Amino Acids and DNA-Conjugated Carbonyls

Par / 10 novembre 2020 / Non classé

Organic Letters: Latest Articles (ACS Publications)
Authors: Huanan Wen, Rui Ge, Yi Qu, Jialin Sun, Xiaodong Shi, Weiren Cui, Hao Yan, Qi Zhang, Yulong An, Wenji Su, Hongfang Yang, Letian Kuai, Alexander L. Satz, and Xuanjia Peng
feedproxy.google.com/~r/acs/orlef7/~3/OlIzZFrt_og/acs.orglett.0c03461

Butterfly Effects Arising from Starting Materials in Fused-Ring Electron Acceptors

Par / 10 novembre 2020 / Non classé

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Tengfei Li, Yao Wu, Jiadong Zhou, Mengyang Li, Jingnan Wu, Qin Hu, Boyu Jia, Xiran Pan, Maojie Zhang, Zheng Tang, Zengqi Xie, Thomas P. Russell, and Xiaowei Zhan
feedproxy.google.com/~r/acs/jacsat/~3/TCrnK0EXqNU/jacs.0c09800

Unified Strategy to Amphenicol Antibiotics: Asymmetric Synthesis of (−)-Chloramphenicol, (−)-Azidamphenicol, and (+)-Thiamphenicol and Its (+)-3-Floride

Par / 10 novembre 2020 / Non classé

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Jinxin Liu, Yaling Li, Miaolin Ke, Minjie Liu, Pingping Zhan, You-Cai Xiao, and Fener Chen
feedproxy.google.com/~r/acs/joceah/~3/dfDM-GYy7sU/acs.joc.0c02181

Quantitative Perspective on Online Flow Reaction Profiling Using a Miniature Mass Spectrometer

Par / 10 novembre 2020 / Non classé

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Organic Process Research & Development

Organic Process Research & Development: Latest Articles (ACS Publications)

Authors: Huaming Sheng, Emily B. Corcoran, Zachary E. X. Dance, Joseph P. Smith, Zhihao Lin, Victoria Ordsmith, Simon Hamilton, and Ping Zhuang
feedproxy.google.com/~r/acs/oprdfk/~3/D4zEQrZwCBE/acs.oprd.0c00294

Development of Scalable Routes to 1-Bicyclo[1.1.1]pentylpyrazoles

Par / 10 novembre 2020 / Non classé

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Organic Process Research & Development

Organic Process Research & Development: Latest Articles (ACS Publications)

Authors: Cayetana Zarate, Michael Ardolino, Gregori J. Morriello, Kaitlyn M. Logan, William P. Kaplan, Luis Torres, Derun Li, Meng Chen, Hongming Li, Jing Su, Peter Fuller, Matthew L. Maddess, and Zhiguo Jake Song
feedproxy.google.com/~r/acs/oprdfk/~3/-pFeq3mwO_Y/acs.oprd.0c00446

Tumor Microenvironment Stimuli‐Responsive Fluorescence Imaging and Synergistic Cancer Therapy by Carbon‐Dot–Cu2+ Nanoassemblies

Par / 9 novembre 2020 / Non classé
Tumor Microenvironment Stimuli‐Responsive Fluorescence Imaging and Synergistic Cancer Therapy by Carbon‐Dot–Cu2+ Nanoassemblies

A tumor microenvironment (TME) stimuli‐responsive fluorescence imaging and trimodal synergistic cancer treatment nanoplatform is facilely constructed via assembling carbon dots and Cu2+. This could act as a potential strategy to achieve enhanced cancer therapeutic efficiency with minimized side effects.

Abstract

A method is developed to fabricate tumor microenvironment (TME) stimuli‐responsive nanoplatform for fluorescence (FL) imaging and synergistic cancer therapy via assembling photosensitizer (chlorine e6, Ce6) modified carbon dots (CDs‐Ce6) and Cu2+. The as‐obtained nanoassemblies (named Cu/CC nanoparticles, NPs) exhibit quenched FL and photosensitization due to the aggregation of CDs‐Ce6. Their FL imaging and photodynamic therapy (PDT) functions are recovered efficiently once they entering tumor sites by the stimulation of TME. Introducing of Cu2+ not only provides extra chemodynamic therapy (CDT) function through reaction with hydrogen peroxide (H2O2), but also depletes GSH in tumors by a redox reaction, thus amplifying the intracellular oxidative stress and enhancing the efficacy of reactive oxygen species (ROS) based therapy. Cu/CC NPs can act as a FL imaging guided trimodal synergistic cancer treatment agent by photothermal therapy (PTT), PDT, and thermally amplified CDT.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Shan Sun, Qiao Chen, Zhongdi Tang, Chuang Liu, Zhongjun Li, Aiguo Wu, Hengwei Lin
doi.org/10.1002/anie.202007786

Scaling Platinum‐Catalyzed Hydrogen Dissociation on Corrugated Surfaces

Par / 9 novembre 2020 / Non classé
Scaling Platinum‐Catalyzed Hydrogen Dissociation on Corrugated Surfaces

Curved platinum single crystals provide stepped surface arrays featuring terraces, steps, and kinks. Linking the structural elements of these surfaces to their chemical activity towards hydrogen dissociation provides new insights into the scalability of reactivity at low‐coordinated sites, such as those featured on heterogeneous catalyst particles.

Abstract

We determine absolute reactivities for dissociation at low coordinated Pt sites. Two curved Pt(111) single‐crystal surfaces allow us to probe either straight or highly kinked step edges with molecules impinging at a low impact energy. A model extracts the average reactivity of inner and outer kink atoms, which is compared to the reactivity of straight A‐ and B‐type steps. Local surface coordination numbers do not adequately capture reactivity trends for H2 dissociation. We utilize the increase of reactivity with step density to determine the area over which a step causes increased dissociation. This step‐type specific reactive area extends beyond the step edge onto the (111) terrace. It defines the reaction cross‐section for H2 dissociation at the step, bypassing assumptions about contributions of individual types of surface atoms. Our results stress the non‐local nature of H2 interaction with a surface and provide insight into reactivity differences for nearly identical step sites.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Sabine V. Auras, Richard Lent, Dima Bashlakov, Jessika M. Piñeiros Bastidas, Tycho Roorda, Rick Spierenburg, Ludo B. F. Juurlink
doi.org/10.1002/anie.202005616

Multiexcitonic Triplet Pair Generation in Oligoacene Dendrimers as Amorphous Solid‐State Miniatures

Par / 9 novembre 2020 / Non classé
Multiexcitonic Triplet Pair Generation in Oligoacene Dendrimers as Amorphous Solid‐State Miniatures

Heterogeneous couplings and energetics for singlet fission (SF) processes were developed in dendritic structures which mimic complicated SF dynamics in amorphous solids. SF in dendritic structures was thoroughly investigated by time‐resolved spectroscopic techniques and quantum chemical calculations in respect of relative orientation/distance between chromophores and through‐bond/‐space interactions.

Abstract

Singlet fission in organic semiconducting materials has attracted great attention for the potential application in photovoltaic devices. Research interests have been concentrated on identifying working mechanisms of coherent SF processes in crystalline solids as ultrafast SF is hailed for efficient multiexciton generation. However, as long lifetime of multiexcitonic triplet pair in amorphous solids facilitates the decorrelation process for triplet exciton extractions, a precise examination of incoherent SF processes is demanded in delicate model systems to represent heterogeneous structures. Heterogeneous coupling and energetics for SF were developed in our oligoacene dendrimers, which mimic complicated SF dynamics in amorphous solids. SF dynamics in dendritic structures was thoroughly investigated by time‐resolved spectroscopic techniques and quantum chemical calculations in respect of the relative orientation/distance between chromophores and though‐bond/‐space interactions.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Juno Kim, Hao Ting Teo, Yongseok Hong, Juwon Oh, Hyungjun Kim, Chunyan Chi, Dongho Kim
doi.org/10.1002/anie.202008533