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septembre 2022 – Page 33 – ChemDigest

Mois : septembre 2022

Novel Poxin Stable cGAMP‐Derivatives Are Remarkable STING Agonists

Par / 1 septembre 2022 / Non classé
Novel Poxin Stable cGAMP-Derivatives Are Remarkable STING Agonists

Dideoxy-cyclic-dinucleotide analogs of cGAS/STING second messenger 2′,3′-cGAMP are prepared using a new and concise synthetic combination of phosphoramidite and phosphotriester chemistry. The dideoxy analogs are found to exhibit remarkable in cellulo and in vitro properties, are stable against degradation by poxvirus immune nucleases, and exhibit superior tumor growth control in a mouse model.

Abstract

2′,3′-cGAMP is a cyclic A- and G-containing dinucleotide second messenger, which is formed upon cellular recognition of foreign cytosolic DNA as part of the innate immune response. The molecule binds to the adaptor protein STING, which induces an immune response characterized by the production of type I interferons and cytokines. The development of STING-binding molecules with both agonistic as well as antagonistic properties is currently of tremendous interest to induce or enhance antitumor or antiviral immunity on the one hand, or to treat autoimmune diseases on the other hand. To escape the host innate immune recognition, some viruses encode poxin endonucleases that cleave 2′,3′-cGAMP. Here we report that dideoxy-2′,3′-cGAMP (1) and analogs thereof, which lack the secondary ribose-OH groups, form a group of poxin-stable STING agonists. Despite their reduced affinity to STING, particularly the compound constructed from two A nucleosides, dideoxy-2′,3′-cAAMP (2), features an unusually high antitumor response in mice.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Samuele Stazzoni, Daniel F. R. Böhmer, Fabian Hernichel, Dilara Özdemir, Aikaterini Pappa, David Drexler, Stefan Bauernfried, Gregor Witte, Mirko Wagner, Simon Veth, Karl‐Peter Hopfner, Veit Hornung, Lars M. König, Thomas Carell
onlinelibrary.wiley.com/doi/10.1002/anie.202207175

Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica

Par / 1 septembre 2022 / Non classé
Formation of a Strong Heterogeneous Aluminum Lewis Acid on Silica

Al(OC(CF3)3)3(PhF) reacts with partially dehydroxylated silica to form very strong Lewis acid sites. The well-defined aluminum Lewis acids are significantly stronger than common molecular Lewis acids and engage in alkyl abstraction reactions that are uncommon using well-defined supported Lewis acids.

Abstract

Al(OC(CF3)3)(PhF) reacts with silanols present on partially dehydroxylated silica to form well-defined ≡SiOAl(OC(CF3)3)2(O(Si≡)2) (1). 27Al NMR and DFT calculations with a small cluster model to approximate the silica surface show that the aluminum in 1 adopts a distorted trigonal bipyramidal coordination geometry by coordinating to a nearby siloxane bridge and a fluorine from the alkoxide. Fluoride ion affinity (FIA) calculations follow experimental trends and show that 1 is a stronger Lewis acid than B(C6F5)3 and Al(OC(CF3)3)(PhF) but is weaker than Al(OC(CF3)3) and iPr3Si+. Cp2Zr(CH3)2 reacts with 1 to form [Cp2ZrCH3][≡SiOAl(OC(CF3)3)2(CH3)] (3) by methide abstraction. This reactivity pattern is similar to reactions of organometallics with the proposed strong Lewis acid sites present on Al2O3.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Kavyasripriya K. Samudrala, Winn Huynh, Rick W. Dorn, Aaron J. Rossini, Matthew P. Conley
onlinelibrary.wiley.com/doi/10.1002/anie.202205745

A Water‐Soluble Antimony‐Rich Polyoxometalate with Broad‐Spectrum Antitumor Activities

Par / 1 septembre 2022 / Non classé
A Water-Soluble Antimony-Rich Polyoxometalate with Broad-Spectrum Antitumor Activities

A novel soluble and water-stable giant Sb-rich polyoxometalate (POM) has been developed, which shows the largest Sb−Ln−W cluster and has the greatest number of Sb centers in a cluster yet found in POM chemistry. Importantly, the Sb-rich POM can exhibit broad-spectrum antitumor and anti-metastatic activities in vitro and in vivo without causing adverse effects, making it a promising candidate for a antitumor agent.

Abstract

Herein, a giant Sb-rich polyoxometalate (POM) {Sb21Tb7W56} is reported, which contains the largest number of Sb atoms in a POM so far. The Sb-rich POM has many interesting structural features and is a rare example of a soluble and water-stable giant POM. Biomedical studies indicate that the Sb-rich POM exhibits broad-spectrum antitumor activity against various cancer cell lines by reactivating the P53-dependent apoptotic processes and disrupting the mitochondrial membrane. In addition, this Sb-rich POM was capable of suppressing the growth and metastasis of a breast cancer in vivo. This work demonstrates that Sb-rich POMs are promising candidates for the development of new anticancer drugs.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Hui‐Ping Xiao, Ya‐Shuai Hao, Xin‐Xiong Li, Peng Xu, Ming‐Dong Huang, Shou‐Tian Zheng
onlinelibrary.wiley.com/doi/10.1002/anie.202210019

Electrochemically Initiated Synthesis of Methanesulfonic Acid

Par / 1 septembre 2022 / Non classé
Electrochemically Initiated Synthesis of Methanesulfonic Acid

The synthesis of methanesulfonic acid was achieved from only methane and oleum in an electrochemical reactor. At the boron-doped diamond anode the species is formed, which initiates the catalytic cycle where methane is selectively sulfonated to the product. A concentration of 3.7 M (approximately 62 % yield) was achieved at 70 °C and 90 bar methane pressure in 22 hours.

Abstract

The direct sulfonation of methane to methanesulfonic acid was achieved in an electrochemical reactor without adding peroxide initiators. The synthesis proceeds only from oleum and methane. This is possible due to in situ formation of an initiating species from the electrolyte at a boron-doped diamond anode. Elevated pressure, moderate temperature and suitable current density are beneficial to reach high concentration at outstanding selectivity. The highest concentration of 3.7 M (approximately 62 % yield) at 97 % selectivity was reached with a stepped electric current program at 6.25–12.5 mA cm−2, 70 °C and 90 bar methane pressure in 22 hours. We present a novel, electrochemical method to produce methanesulfonic acid, propose a reaction mechanism and show general dependencies between parameters and yields for methanesulfonic acid.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Joel Britschgi, Wolfgang Kersten, Siegfried R. Waldvogel, Ferdi Schüth
onlinelibrary.wiley.com/doi/10.1002/anie.202209591

Central Unit Fluorination of Non‐Fullerene Acceptors Enables Highly Efficient Organic Solar Cells with Over 18 % Efficiency

Par / 1 septembre 2022 / Non classé
Central Unit Fluorination of Non-Fullerene Acceptors Enables Highly Efficient Organic Solar Cells with Over 18 % Efficiency

A series of CH molecules with newly modification site on central unit of Y-series electron acceptors has been designed and synthesized to afford better-performed organic solar cells (OSCs). Further fluorination on the largely unexplored central unit enabled significantly improved photovoltaic performance with over 18% efficiency for CH6-based binary OSCs..

Abstract

Halogenation of terminal of acceptors has been shown to give dramatic improvements in power conversion efficiencies (PCEs) of organic solar cells (OSCs). Similar significant results could be expected from the halogenation of the central units of state-of-the-art Y-series acceptors. Herein, a pair of acceptors, termed CH6 and CH4, featuring a conjugation-extended phenazine central unit with and without fluorination, have been synthesized. The fluorinated CH6 has enhanced molecular interactions and crystallinity, superior fibrillar network morphology and improved charge generation and transport in blend films, thus affording a higher PCE of 18.33 % for CH6-based binary OSCs compared to 16.49 % for the non-fluorinated CH4. The new central site offers further opportunities for structural optimization of Y-series molecules to afford better-performed OSCs and reveals the effectiveness of fluorination on central units.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Hongbin Chen, Huazhe Liang, Ziqi Guo, Yu Zhu, Zhe Zhang, Zhixiang Li, Xiangjian Cao, Haohui Wang, Wanying Feng, Yalu Zou, Lingxian Meng, Xiaoyun Xu, Bin Kan, Chenxi Li, Zhaoyang Yao, Xiangjian Wan, Zaifei Ma, Yongsheng Chen
onlinelibrary.wiley.com/doi/10.1002/anie.202209580

A Metal‐Organic Framework with Nonpolar Pore Surfaces for the One‐Step Acquisition of C2H4 from a C2H4 and C2H6 Mixture

Par / 1 septembre 2022 / Non classé
A Metal-Organic Framework with Nonpolar Pore Surfaces for the One-Step Acquisition of C2H4 from a C2H4 and C2H6 Mixture

The metal-organic framework FJI-H11-Me(des) which has nonpolar pore surfaces can directly give polymer-grade C2H4 from C2H4/C2H6 mixtures at different gas flow rates, temperatures, and relative humidity. This separation is possible because it adsorbs C2H6 rather than C2H4 between 273 and 303 K.

Abstract

Because C2H4 plays an essential role in the chemical industry, economical and energy-efficient separation of ethylene (C2H4) from ethane (C2H6) is extremely important. With the exception of energy-intensive cryogenic distillation, there are few one-step methods to obtain polymer-grade (≥99.95 % pure) C2H4 from C2H4/C2H6 mixtures. Here we report a highly stable metal-organic-framework (MOF) FJI-H11-Me(des) (FJI-H=Hong’s group in Fujian Institute of Research on the Structure of Matter) which features one-dimensional hexagonal nonpolar pore surfaces constructed by aromatic rings and alkyl groups. This FJI-H11-Me(des) adsorbs C2H6 rather than C2H4 between 273 and 303 K. Practical breakthrough experiments with C2H4 containing 1 % C2H6 have shown that FJI-H11-Me(des) can realize the acquisition in one-step of polymer-grade, 99.95 % pure C2H4 under various conditions including different gas flow rates, temperatures and relative humidity.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zhengyi Di, Caiping Liu, Jiandong Pang, Shuixiang Zou, Zhenyu Ji, Falu Hu, Cheng Chen, Daqiang Yuan, Maochun Hong, Mingyan Wu
onlinelibrary.wiley.com/doi/10.1002/anie.202210343

Bright and Photostable Fluorescent Metal Nanocluster Supraparticles from Invert Emulsions

Par / 1 septembre 2022 / Non classé
Bright and Photostable Fluorescent Metal Nanocluster Supraparticles from Invert Emulsions

Supraparticles of gold, silver and copper nanoclusters are formed by drying the water droplets in invert emulsions, resulting in a profoundly enhanced photoluminescence emission and resistance to photobleaching. The supraparticle structure greatly enhances the performance, where the inhibition of the twisted intermolecular charge transfer is one of the responsible causes.

Abstract

Fluorescent supraparticles of gold, silver and copper nanoclusters are synthesized by simply drying of invert emulsions, resulting in a dozen-fold increase in photoluminescence quantum yield (up to ≈80 %) and a significant improvement in photostability. The inhibition of the ligand twisting during the intramolecular charge transfer is found to be responsible for the enhancement, especially for the gold nanocluster supraparticles. This research provides a general, flexible, and easy method for producing highly luminescent and photostable metal nanocluster-based materials that promise practical applications in white-light-emitting diodes.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Shaochen Zhou, Bo Peng, Yanyan Duan, Kai Liu, Olli Ikkala, Robin H. A. Ras
onlinelibrary.wiley.com/doi/10.1002/anie.202210808

Highly Efficient Electrosynthesis of Nitric Oxide for Biomedical Applications

Par / 1 septembre 2022 / Non classé
Highly Efficient Electrosynthesis of Nitric Oxide for Biomedical Applications

An electrochemical system employing a rationally designed single-iron atom based biomimetic catalyst (Fe SAC) is developed for high-efficient and controlled generation of nitric oxide (NO). The effectiveness of NO generation system underscores a great promise to expedite NO research in both therapeutic and mechanistic applications.

Abstract

Nitric oxide (NO) constitutes one of the most versatile therapeutics for biomedical applications. The efficient and on-demand NO generation essentially dictates its concentration dependent therapeutic activity. Here, we report an electrochemical system employing a rationally designed single-iron atom based biomimetic catalyst (i.e., Fe SAC), for high-efficient and controlled NO generation. The Fe SAC shows superior catalytic ability in electrochemical reduction of nitrite, with maximal NO generation rate achieving 2.1 μM (min μg)−1. Theoretical studies suggest the significant decrease of Gibbs-free energy of NO2− adsorption on single-iron atom accounts for its high catalytic efficiency. Moreover, ample amount of NO can be controllably generated in a potential dependent manner. For antibacterial application, the generated NO overwhelmingly disrupts both gram-negative and gram-positive strains, highlighting a great promise to expedite NO research in both basic and applied sciences.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jing Jin, Junjie Mao, Wenjie Wu, Ying Jiang, Wenjie Ma, Ping Yu, Lanqun Mao
onlinelibrary.wiley.com/doi/10.1002/anie.202210980

Stereogradient Poly(Lactic Acid) from meso‐Lactide/L‐Lactide Mixtures

Par / 1 septembre 2022 / Non classé
Stereogradient Poly(Lactic Acid) from meso-Lactide/L-Lactide Mixtures

Enter stereogradient PLA: A tripodal zirconium complex catalyzes the polymerization of L-lactide contaminated with meso-lactide to yield stereogradient poly(lactic acid) (PLA) as described by Moshe Kol et al. in their Research Article (DOI: 10.1002/anie.202207652). The stereogradient copolymers exhibit enhanced crystallinities relative to the stereo-random copolymers derived from tin octanoate, and may alleviate the need for L-lactide purification.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Rami Hador, Michael Shuster, Vincenzo Venditto, Moshe Kol
onlinelibrary.wiley.com/doi/10.1002/anie.202212470

The Alkynylative Difunctionalization of Alkenes

Par / 1 septembre 2022 / Non classé
The Alkynylative Difunctionalization of Alkenes

The alkynylative difunctionalization of alkenes is one of the most straightforward and efficient strategies for preparing useful alkynyl-containing compounds and so has made great progress in recent years. This review comprehensively summarized the alkynylative difunctionalization of alkenes. For more information, see the Review by J. Huang and Z.-M. Chen (DOI: 10.1002/chem.202201519).

Abstract

Given alkynyl group is an important functional unit, a variety of efficient methods have been developed to construct alkynyl-containing compounds. Among them, the alkynylative difunctionalization of alkenes is one of the most straightforward and efficient strategies for preparing these compounds and so has made great progress in recent years, including the catalytic asymmetric manner. However, there is no comprehensive review to summarize these studies. This review is aimed at comprehensively summarizing the alkynylative difunctionalization of alkenes, which is presented in terms of alkynylation-initiated and alkynylation-terminated difunctionalizations of alkenes. We hope that this review will help to encourage more researchers to further explore in this field.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jie Huang, Zhi‐Min Chen
onlinelibrary.wiley.com/doi/10.1002/chem.202201519

Two Paths to Oxidative C−H Amination Under Basic Conditions: A Theoretical Case Study Reveals Hidden Opportunities Provided by Electron Upconversion

Par / 1 septembre 2022 / Non classé
Two Paths to Oxidative C−H Amination Under Basic Conditions: A Theoretical Case Study Reveals Hidden Opportunities Provided by Electron Upconversion**

Exploring the possibilities of an odd-electron bond formation under basic and oxidative conditions in silico: How radical-anion bond formation and electron upconversion allow for milder oxidative conditions.

Abstract

Traditionally, cross-dehydrogenative coupling (CDC) leads to C−N bond formation under basic and oxidative conditions and is proposed to proceed via a two-electron bond formation mediated by carbenium ions. However, the formation of such high-energy intermediates is only possible in the presence of strong oxidants, which may lead to undesired side reactions and poor functional group tolerance. In this work we explore if oxidation under basic conditions allows the formation of three-electron bonds (resulting in “upconverted” highly-reducing radical-anions). The benefit of this “upconversion” process is in the ability to use milder oxidants (e. g., O2) and to avoid high-energy intermediates. Comparison of the two- and three-electron pathways using quantum mechanical calculations reveals that not only does the absence of a strong oxidant shut down two-electron pathways in favor of a three-electron path but, paradoxically, weaker oxidants react faster with the upconverted reductants by avoiding the inverted Marcus region for electron transfer.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Paul Eckhardt, Quintin Elliot, Igor V. Alabugin, Till Opatz
onlinelibrary.wiley.com/doi/10.1002/chem.202201637

Interplay and Competition Between Two Different Types of Redox‐Active Ligands in Cobalt Complexes: How to Allocate the Electrons?

Par / 1 septembre 2022 / Non classé
Interplay and Competition Between Two Different Types of Redox-Active Ligands in Cobalt Complexes: How to Allocate the Electrons?

Molecular transition metal complexes with two different types of redox-active ligands are uncommon. Herein, the synthesis of the first mono- and dinuclear cobalt complexes is reported which exhibit redox-active oxolene-type ligands in combination with redox-active bisguanidine/urea azine ligands, representing four or six center redox systems. Radical ligands are present in all complexes; the differences in the electronic structures lead to characteristic magnetic and optical properties.

Abstract

The field of molecular transition metal complexes with redox-active ligands is dominated by compounds with one or two units of the same redox-active ligand; complexes in which different redox-active ligands are bound to the same metal are uncommon. This work reports the first molecular coordination compounds in which redox-active bisguanidine or urea azine (biguanidine) ligands as well as oxolene ligands are bound to the same cobalt atom. The combination of two different redox-active ligands leads to mono- as well as unprecedented dinuclear cobalt complexes, being multiple (four or six) center redox systems with intriguing electronic structures, all exhibiting radical ligands. By changing the redox potential of the ligands through derivatisation, the electronic structure of the complexes could be altered in a rational way.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Lukas Lohmeyer, Marco Werr, Elisabeth Kaifer, Hans‐Jörg Himmel
onlinelibrary.wiley.com/doi/10.1002/chem.202201789

π‐Extended Pleiadienes by [5+2] Annulation of 1‐Boraphenalenes and ortho‐Dihaloarenes

Par / 1 septembre 2022 / Non classé
π-Extended Pleiadienes by [5+2] Annulation of 1-Boraphenalenes and ortho-Dihaloarenes

Intrigued by their (anti)aromaticity and expected negative curvature, a series of π-extended pleiadienes has been synthesized by palladium-catalyzed [5+2] annulation. Their structural, redox and optical properties were probed and further investigated by theoretical calculations.

Abstract

Palladium-catalyzed [5+2] annulation of 1-boraphenalenes with ortho-dihaloarenes afforded negatively curved π-extended pleiadienes. Two benzo[1,2-i:4,5-i’]dipleiadienes (BDPs) featuring a seven-six-seven-membered ring arrangement were synthesized and investigated. Their crystal structure revealed a unique packing arrangement and theoretical calculations were employed to shed light onto the dynamic behavior of the BDP moiety and its aromaticity. Further, a naphthalene-fused pleiadiene was stitched together by oxidative cyclodehydrogenation to yield an additional five-membered ring. This formal azulene moiety led to distinct changes in optical and redox properties and increased perturbation of the aromatic system.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Matthias Schnitzlein, Chongwei Zhu, Kazutaka Shoyama, Frank Würthner
onlinelibrary.wiley.com/doi/10.1002/chem.202202053

Mechanistic Studies for the Rational Design of Multivalent Glycodendrimers

Par / 1 septembre 2022 / Non classé
Mechanistic Studies for the Rational Design of Multivalent Glycodendrimers

Interaction analysis of B antigen 16-mers (glycodendrimers), which differ with respect to the length of their linkers, with their IgM antibody revealed that the statistical rebinding model, which involves the rapid exchange of clustered glycans, contributes significantly to the multivalency. These results suggest that in addition to the chelation ability, high-density glycan-presentation to enhance statistical rebinding should also be taken into consideration in glycodendrimer design.

Abstract

We have synthesized B-antigen-displaying dendrimers (16-mers) with different sizes and evaluated their affinity to their IgM antibody in order to investigate which design features lead to effective multivalency. Unexpectedly, the smallest dendrimer, which cannot chelate the multiple binding sites of IgM, clearly exhibited multivalency, together with an affinity similar to or higher than those of the larger dendrimers. These results indicate that the statistical rebinding model, which involves the rapid exchange of clustered glycans, significantly contributes to the multivalency of glycodendrimers. Namely, in the design of glycodendrimers, high-density glycan presentation to enhance statistical rebinding should be considered in addition to the ability to chelate multiple binding sites. This notion stands in contrast to the currently prevailing scientific consensus, which prioritizes the chelation model. This study thus provides new and important guidelines for molecular design of glycodendrimers.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yoshiyuki Manabe, Masato Tsutsui, Kohtaro Hirao, Risako Kobayashi, Hiroshi Inaba, Kazunori Matsuura, Daisuke Yoshidome, Kazuya Kabayama, Koichi Fukase
onlinelibrary.wiley.com/doi/10.1002/chem.202201848

Synthesis of Enantioenriched Sulfoxides by an Oxidation‐Reduction Enzymatic Cascade

Par / 1 septembre 2022 / Non classé
Synthesis of Enantioenriched Sulfoxides by an Oxidation-Reduction Enzymatic Cascade

Linear oxidation-reduction bienzymatic cascade was designed to synthesize chiral sulfoxides starting from sulfides. The combinatorial cascade gave a broad range of structurally diverse sulfoxides in excellent optical purity (>99 % ee) with complementary chirality. The cascade combines the superb stability of CiVCPO and enantioselectivity of MsrA/MsrB, as a result, it not only allows CiVCPO to gain relevance in chiral sulfoxide synthesis, but also provides a powerful approach for (S)-sulfide synthesis.

Abstract

Chiral sulfoxides are versatile synthons and have gained a particular interest in asymmetric synthesis of active pharmaceutical and agrochemical ingredients. Herein, a linear oxidation–reduction bienzymatic cascade to synthesize chiral sulfoxides is reported. The extraordinarily stable and active vanadium-dependent chloroperoxidase from Curvularia inaequalis (CiVCPO) was used to oxidize sulfides into racemic sulfoxides, which were then converted to chiral sulfoxides by highly enantioselective methionine sulfoxide reductase A (MsrA) and B (MsrB) by kinetic resolution, respectively. The combinatorial cascade gave a broad range of structurally diverse sulfoxides with excellent optical purity (>99 %  ee) with complementary chirality. The enzymatic cascade requires no NAD(P)H recycling, representing a facile method for chiral sulfoxide synthesis. Particularly, the envisioned enzymatic cascade not only allows CiVCPO to gain relevance in chiral sulfoxide synthesis, but also provides a powerful approach for (S)-sulfoxide synthesis; the latter case is significantly unexplored for heme-dependent peroxidases and peroxygenases.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Peipei Wang, Xiaofeng Han, Xinqi Liu, Richen Lin, Yongzheng Chen, Zhoutong Sun, Wuyuan Zhang
onlinelibrary.wiley.com/doi/10.1002/chem.202201997

Water Reduction and Dihydrogen Addition in Aqueous Conditions With ansa‐Phosphinoborane

Par / 1 septembre 2022 / Non classé
Water Reduction and Dihydrogen Addition in Aqueous Conditions With ansa-Phosphinoborane

Water reduction and H2 activation by an ortho-phenylene-bridged phosphinoborane compound are demonstrated. The mechanisms of these transformations are investigated using kinetic measurements and DFT calculations. Nuclear spin hyperpolarization is detected as a result of parahydrogen (para-H2) activation by the phosphinoborane in the presence of water, proving the reversibility of water addition to this compound.

Abstract

Ortho-phenylene-bridged phosphinoborane (2,6-Cl2Ph)2B-C6H4-PCy21 was synthesized in three steps from commercially available starting materials. 1 reacts with H2 or H2O under mild conditions to form corresponding zwitterionic phosphonium borates 1-H2 or 1-H2O. NMR studies revealed both reactions to be remarkably reversible. Thus, when exposed to H2, 1-H2O partially converts to 1-H2 even in the presence of multiple equivalents of water in the solution. The addition of parahydrogen to 1 leads to nuclear spin hyperpolarization both in dry and hydrous solvents, confirming the dissociation of 1-H2O to free 1. These observations were supported by computational studies indicating that the formation of 1-H2 and 1-H2O from 1 are thermodynamically favored. Unexpectedly, 1-H2O can release molecular hydrogen to form phosphine oxide 1-O. Kinetic, mechanistic, and computational (DFT) studies were used to elucidate the unique “umpolung” water reduction mechanism.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Kristina Sorochkina, Konstantin Chernichenko, Vladimir V. Zhivonitko, Martin Nieger, Timo Repo
onlinelibrary.wiley.com/doi/10.1002/chem.202201927

Improving the Electrocatalytic Activity of a Nickel‐Organic Framework toward the Oxygen Evolution Reaction through Vanadium Doping

Par / 1 septembre 2022 / Non classé
Improving the Electrocatalytic Activity of a Nickel-Organic Framework toward the Oxygen Evolution Reaction through Vanadium Doping

The spherical structure V-doped Ni-MOF was successfully constructed on nickel foam by a facile two-step hydrothermal method. The V0.09−Ni0.91MOF/NF catalyst demonstrates extraordinary OER performance in alkaline. Studies showed that the three-dimensional structure of V-doped Ni-MOF/NF can provide more catalytically active sites and adjust the binding energy with intermediates, thereby enhancing the OER catalytic activity.

Abstract

Metal-organic frameworks (MOFs) have been considered as potential oxygen evolution reaction (OER) electrocatalysts owning to their ultra-thin structure, adjustable composition, high surface area, and high porosity. Here, we designed and fabricated a vanadium-doped nickel organic framework (V1−x−NixMOF) system by using a facile two-step solvothermal method on nickel foam (NF). The doping of vanadium remarkably elevates the OER activity of V1−x−NixMOF, thus demonstrating better performance than the corresponding single metallic Ni-MOF, NiV-MOF and RuO2 catalysts at high current density (>400 mA cm−2). V0.09−Ni0.91MOF/NF provides a low overpotential of 235 mV and a small Tafel slope of 30.3 mV dec−1 at a current density of 10 mA cm−2. More importantly, a water-splitting device assembled with Pt/C/NF and V0.09−Ni0.91MOF/NF as cathode and anode yielded a cell voltage of 1.96 V@1000 mA cm−2, thereby outperforming the-state-of-the-art RuO2(+)||Pt/C(−). Our work sheds new insight on preparing stable, efficient OER electrocatalysts and a promising method for designing various MOF-based materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Hongbo Yu, Lixia Wang, Huatong Li, Zuyang Luo, Tayirjan Taylor Isimjan, Xiulin Yang
onlinelibrary.wiley.com/doi/10.1002/chem.202201784

Modulation of the Sorption Characteristics for an H‐bonded porous Architecture by Varying the Chemical Functionalization of the Channel Walls

Par / 1 septembre 2022 / Non classé
Modulation of the Sorption Characteristics for an H-bonded porous Architecture by Varying the Chemical Functionalization of the Channel Walls

Fine tuning of gas sorption properties and I2 capture/release was achieved by variation of the functional group(s) decorating the channels of a microporous H-bonded framework material.

Abstract

Five isostructural microporous supramolecular architectures prepared by H-bonded assembly between the hexa-anionic complex [Zr2(Ox)7]6− (Ox=oxalate, (C2O4)2−) and tripodal cations (H3-TripCH2-R)3+ with R=H, CH3, OH and OBn (Bn=CH2Ph) are reported. The possibility to obtain the same structure using a mixture of tripodal cations with different R group (R=OH and R=CH3) has also been successfully explored, providing a unique example of three-component H-bonded porous framework. The resulting SPA-1(R) materials feature 1D pores decorated by R groups, with apparent pore diameters ranging from 3.0 to 8.5 Å. Influence of R groups on the sorption properties of these materials is evidenced through CO2 and H2O vapor sorption/desorption experiments, as well as with I2 capture/release experiments in liquid media. This study is one of the first to demonstrate the possibility of tuning the porosity and exerting precise control over the chemical functionalization of the pores in a given H-bonded structure, without modifying the topology of the reference structure, and thus finely adjusting the sorption characteristics of the material.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Nans Roques, Anthony Tovar‐Molle, Carine Duhayon, Stéphane Brandès, Alex Spieß, Christoph Janiak, Jean‐Pascal Sutter
onlinelibrary.wiley.com/doi/10.1002/chem.202201935

Chemo‐ and Site‐Selective Electro‐Oxidative Alkane Fluorination by C(sp3)−H Cleavage

Par / 1 septembre 2022 / Non classé
Chemo- and Site-Selective Electro-Oxidative Alkane Fluorination by C(sp3)−H Cleavage

Metal-free electrochemical C(sp3)−H fluorination was accomplished without the requirement for directing groups and electrophilic fluorine sources, featuring high levels of site- and chemoselectivity.

Abstract

Electrochemical fluorinations of C(sp3)−H bonds with a nucleophilic fluoride source have been accomplished in a chemo- and site-selective fashion, avoiding the use of electrophilic F+ sources and stoichiometric oxidants. The introduced metal-free strategy exhibits high functional group tolerance, setting the stage for late-stage fluorinations of biorelevant motifs. The synthetic utility of the C(sp3)−H fluorination was reflected by subsequent one-pot arylation of the generated benzylic fluorides.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Maximilian Stangier, Alexej Scheremetjew, Lutz Ackermann
onlinelibrary.wiley.com/doi/10.1002/chem.202201654

High‐fidelity Recognition of Organotrifluoroborate Anions (R−BF3−) as Designer Guest Molecules

Par / 1 septembre 2022 / Non classé
High-fidelity Recognition of Organotrifluoroborate Anions (R−BF3−) as Designer Guest Molecules

Organic trifluoroborate anions (R−BF3−) are found to be competent size-matched binding partners for cyanostar macrocycles. Binding involves the BF3− headgroups and is modulated by the sterics of the substituent. Small vinyl and methyl substituents bind equally well and lay a foundation for the guest-design of self-assembled architectures.

Abstract

The recognition of boron compounds is well developed as boronic acids but untapped as organotrifluoroborate anions (R−BF3−). We are exploring the development of these and other designer anions as anion-recognition motifs by considering them as substituted versions of the parent inorganic ion. To this end, we demonstrate strong and reliable binding of organic trifluoroborates, R−BF3−, by cyanostar macrocycles that are size-complementary to the inorganic BF4− progenitors. We find that recognition is modulated by the substituent’s sterics and that the affinities are retained using the common K+ salts of R−BF3− anions.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Edward G. Sheetz, Zhao Zhang, Alyssa Marogil, Minwei Che, Maren Pink, Veronica Carta, Krishnan Raghavachari, Amar H. Flood
onlinelibrary.wiley.com/doi/10.1002/chem.202201584

Dynamic Covalent Optical Chirality Sensing with a Sterically Encumbered Aminoborane

Par / 1 septembre 2022 / Non classé
Dynamic Covalent Optical Chirality Sensing with a Sterically Encumbered Aminoborane

A sterically encumbered aminoborane was designed to generate strong CD effects upon dynamic covalent binding of chiral alcohols, amino alcohols and diols. This can be used for the fast determination of the concentration, absolute configuration and enantiomeric excess of a variety of small molecules and for streamlining of small-scale asymmetric reaction analysis with less than 1 mg of crude material and without work-up.

Abstract

A sterically encumbered aminoborane sensor is introduced and used for quantitative stereochemical analysis of monoalcohols, diols and amino alcohols. The small-molecule probe exhibits a rigid ortho-substituted arene scaffold with a proximate boron binding site and a triarylamine circular dichroism (CD) reporter unit which proved to be crucial for the observed chiroptical signal induction. Coordination of the chiral target molecule produces strong Cotton effects and UV changes that are readily correlated to its absolute configuration, enantiomeric composition and concentration to achieve comprehensive stereochemical analysis within a 5 % absolute error margin. The sensing method was successfully applied in the chromatography-free analysis of less than one milligram of a crude asymmetric reaction mixture and the advantages of this chiroptical sensing approach, which is amenable to high-throughput experimentation equipment and automation, over traditional methods is discussed.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Zeus A. De los Santos, Ciarán C. Lynch, Christian Wolf
onlinelibrary.wiley.com/doi/10.1002/chem.202202028

(Na0.74Ag1.26)BaSnS4: A New AgGaS2‐Type Nonlinear Optical Sulfide with a Wide Band Gap and High Laser Induced Damage Threshold

Par / 1 septembre 2022 / Non classé
(Na0.74Ag1.26)BaSnS4: A New AgGaS2-Type Nonlinear Optical Sulfide with a Wide Band Gap and High Laser Induced Damage Threshold

A new AgGaS2-type sulfide (Na0.74Ag1.26)BaSnS4 with compressed chalcopyrite-like structure was obtained. It exhibits balanced NLO properties, including moderate SHG response, wide band gap, and high LIDT.

Abstract

The development of high-power solid-state lasers is in urgent need of infrared (IR) nonlinear optical (NLO) materials with wide band gaps and high laser-induced damage thresholds (LIDTs). Herein, a new compressed chalcopyrite-like IR NLO crystal (Na0.74Ag1.26)BaSnS4 was successfully synthesized using a facile high-temperature solid-state method. Its structure can be considered as a variant of chalcopyrite AgGaS2 (AGS)-type ones. It features a three-dimensional framework constructed by corner-sharing {[(Na/Ag)S4]7−}∞ layers and isolated SnS4 tetrahedra with negative cavities occupied by counter ion Ba2+. (Na0.74Ag1.26)BaSnS4 exhibits phase-matchable moderate SHG response (0.31 × AGS), wide band gap (3.70 eV), and high LIDT (6.44 × AGS). Theoretical calculations reveal that the NLO response of (Na0.74Ag1.26)BaSnS4 is mainly originated from the synergetic effects of AgS4 and SnS4 tetrahedra, and the inclusion of alkaline and alkaline earth metals is responsible for the wide band gap and high LIDT. Moreover, the discovery of this chalcopyrite-like compound will provide a feasible design strategy for the exploration of new promising IR NLO materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Wenfeng Zhou, Wenlong Liu, Sheng‐Ping Guo
onlinelibrary.wiley.com/doi/10.1002/chem.202202063

Coordination Adaptable Networks: Zirconium(IV) Carboxylates

Par / 1 septembre 2022 / Non classé
Coordination Adaptable Networks: Zirconium(IV) Carboxylates

Getting into shape again: Coordination adaptable networks (CooANs) are reshapable materials based on the dynamic and degenerate exchange of coordinative bonds. The materials described here, built by ligand exchange from [Zr6O4(OH)4(O2CMe)12] and a carboxylic acid-containing polymer matrix, which yields [Zr6O4(OH)4]-based crosslinks, display vitrimer-like properties.

Abstract

Vitrimers are 3D “covalent adaptable networks” (CANs) with flow properties thanks to thermally activated associative exchange reactions. This contribution introduces coordination adaptable networks, or CooANs, that are topologically related to metal–organic frameworks with octahedral Zr6 clusters as secondary building units in a carboxylic acid-functionalized acrylate-methacrylate copolymer matrix. A series of Zr-CooAN-x materials (x=percent of Zr6 loading relative to maximum capacity) was synthesized with x=5, 10, 15, 20, 25, 50 and 100. The mechanical and rheological investigations demonstrate vitrimer-like properties for x up to 50, the crosslink migration being ensured by carboxylate ligand exchange, with relaxation becoming slower as the Zr6 content is increased. The flow activation energy of Zr-CooAN-10 is 92.9±3.6 kJ mol−1. Rapid (30 min) hot-press reshaping occurs at temperatures in the 50–100 °C range under a 3-ton pressure and does not significantly alter the material properties.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Meenu Murali, Dimitri Berne, Christine Joly‐Duhamel, Sylvain Caillol, Eric Leclerc, Eric Manoury, Vincent Ladmiral, Rinaldo Poli
onlinelibrary.wiley.com/doi/10.1002/chem.202202058

20π Antiaromatic Isophlorins without Metallation or Core Modification

Par / 1 septembre 2022 / Non classé
20π Antiaromatic Isophlorins without Metallation or Core Modification**

For the first time, the synthesis of free-base (metal-free) isophlorins with 20π antiaromatic character was achieved without core modification. The reduction of β-tetracyanoporphyrins by hydrazine under aerobic conditions yielded isophlorins. These 18π aromatic porphyrin/20π antiaromatic isophlorin redox interconversions are reversible.

Abstract

Isophlorins (two-electron-reduced porphyrins) with 20π antiaromaticity have been synthesized by metallation or core modification (replacing the inner NHs with less bulky atoms) thus far. The core-modification number (CMN) is an important factor for the stability of isophlorins against their oxidation to porphyrins. However, isophlorins with small CMN (≤2), i. e., without significant core modification, are difficult to synthesize and important for understanding their structure–antiaromaticity relationships. Herein, we report the synthesis of free-base (metal-free) antiaromatic isophlorins with no core modification (CMN=0) for the first time. β-Tetracyanoporphyrins were successfully reduced by hydrazine to their corresponding isophlorins under aerobic conditions. These porphyrin/isophlorin transformations are reversible. Their structure and antiaromaticity were studied via 1H NMR, UV-vis/near-infrared absorption spectroscopy, X-ray diffraction and theoretical calculations.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Haruna Sugimura, Kana Nakajima, Ken‐ichi Yamashita, Takuji Ogawa
onlinelibrary.wiley.com/doi/10.1002/ejoc.202200747

We Need to Talk about Kekulé: The 150th Anniversary of the Benzene Structure

Par / 1 septembre 2022 / Non classé
We Need to Talk about Kekulé: The 150th Anniversary of the Benzene Structure

2022 is a more appropriate year than 2015 to celebrate the 150th anniversary of the Kekulé benzene structure, for in 1865 Kekulé did not propose the familiar hexagonal 1,3,5-cyclohexatriene formulation. Why did he not?

Abstract

Although the paper published by Kekulé in 1865 is generally accepted as the seminal document regarding the elucidation of the structure of benzene, it was not for another seven years that Kekulé introduced a “collision theory” which, in his view, made the 1,3,5-cyclohexatriene formulation at last acceptable. 2022 is therefore an appropriate year to celebrate the 150th anniversary of his proposal. The present Perspective focusses in particular on how Kekulé’s mind has evolved during that short period of time. After a short introduction, followed by a historical note about the emergence of aromatic chemistry and the role of Kekulé as founder of structural organic chemistry, this Perspective discloses in three chapters the step-by-step unveiling of the 1,3,5-cyclohexatriene structure and focusses on Kekulé’s own dubiety about this formula. Eventually, in 1872 Kekulé’s benzene saga is completed in the article in which he discloses his final theory on the structure of benzene. In the last section, a short review is presented on the later quest for a fully symmetric single-formula representation of benzene.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Pierre De Clercq
onlinelibrary.wiley.com/doi/10.1002/ejoc.202200171