Green Additives in Chitosan‐Based Bioplastic Films: Physical, Mechanical, and Chemical Properties

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Green Additives in Chitosan-Based Bioplastic Films: Physical, Mechanical, and Chemical Properties

Synthesis and analysis of chitosan-based materials with different green additives as a first step towards renewable plastic alternatives. The properties of the films were tunable in a broad range, and the additives could be divided in three different classes depending on their uptake behavior: linear, non-linear, and crosslinking additives.


Abstract

To switch to alternatives for fossil-fuel-based polymer materials, renewable raw materials from green resources should be utilized. Chitosan is such a material that is a strong, but workable derivative from chitin, obtained from crustaceans. However, various applications ask for specific plastic properties, such as certain flexibility, hardness and transparency. With different additives, also obtainable from green resources, chitosan-based composites in the form of self-supporting films, ranging from very hard and brittle to soft and flexible were successfully produced. The additives turned out to belong to one of three categories, namely linear, non-linear, or crosslinking additives. The non-linear additives could only be taken up to a certain relative amount, whereas the uptake of linear additives was not limited within the range of our experiments. Additives with multiple functional groups tend to crosslink chitosan even at room temperature in an acidic medium. Finally, it was shown that dissolving the chitosan in acetic acid and subsequently drying the matrix as a film results in reacetylation compared to the starting chitosan source, resulting in a harder material. With these findings, it is possible to tune the properties of chitosan-based polymer materials, making a big step towards application of this renewable polymer within consumer goods.

RNA‐Selective Small‐Molecule Ligands: Recent Advances in Live‐Cell Imaging and Drug Discovery

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RNA-Selective Small-Molecule Ligands: Recent Advances in Live-Cell Imaging and Drug Discovery

Advancing cell-membrane-permeable and/or bioactive small-molecule ligands specifically binding to RNA structures may provide powerful tools to understand further RNA biology in live cells and facilitate the investigation in the cutting-edge research areas of fluorescence live-cell imaging, chemical biology and drug discovery.


Abstract

RNA structures, including those formed from coding and noncoding RNAs, alternative to protein-based drug targets, could be a promising target of small molecules for drug discovery against various human diseases, particularly in anticancer, antibacterial and antivirus development. The normal cellular activity of cells is critically dependent on the function of various RNA molecules generated from DNA transcription. Moreover, many studies support that mRNA-targeting small molecules may regulate the synthesis of disease-related proteins via the non-covalent mRNA-ligand interactions that do not involve gene modification. RNA-ligand interaction is thus an attractive approach to address the challenge of “undruggable” proteins in drug discovery because the intracellular activity of these proteins is hard to be suppressed with small molecule ligands. We selectively surveyed a specific area of RNA structure-selective small molecule ligands in fluorescence live cell imaging and drug discovery because the area was currently underexplored. This state-of-the-art review thus mainly focuses on the research published within the past three years and aims to provide the most recent information on this research area; hopefully, it could be complementary to the previously reported reviews and give new insights into the future development on RNA-specific small molecule ligands for live cell imaging and drug discovery.

Metal‐Catalyzed Carbonylation Reactions with CO2: An Update

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Metal-Catalyzed Carbonylation Reactions with CO2: An Update

Catalytic carbonylation with CO2 : The latest updates on C1-carbonylative homologation of carbon scaffolds by means of metal catalyzed fixation of CO2 are collected in the present Review article. Innovative catalytic systems, enabling technologies and mechanistic investigations are contributing to the current developments of this fascinating research field.


Abstract

The utilization of CO2 as an efficient and environmentally friendly chemical analogue of CO is becoming a solid reality in the chemical scenario. CO2-based carbonylations have started paralleling the more consolidated carboxylation procedures, opening new horizons and perspectives in the utilization of carbon dioxide as an organic C1-containing building block. The advent of efficient and site-selective metal-catalyzed protocols for the fixation of CO2 into organic scaffolds, under controlled reductive conditions, contributed substantially to the development of robust, efficient, and convenient protocols. In the present Review article, a collection of the most recent examples of metal-catalyzed CO2-based carbonylations is documented with a particular emphasis on mechanistic aspects.

An Overview of α‐Aminoalkyl Radical Mediated Halogen‐Atom Transfer

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An Overview of α-Aminoalkyl Radical Mediated Halogen-Atom Transfer

Halogen-atom-transfer (XAT) processes have revolutionized the use of ubiquitous halide reagents in organic chemistry. This mini-review focuses on recent C−C bond forming reactions that have exploited α-aminoalkyl radicals as metal-free XAT procedures.


Abstract

The merging of photocatalysis with halogen-atom transfer (XAT) processes has proven to be a versatile tool for the generation of carbon-centered radicals in organic synthesis. XAT processes are unique in that they generate radicals without requiring the use of strong reductants necessary for the traditional single electron transfer (SET) activation of halides. Pathways to achieve XAT in synthetic applications can be categorized into three major sections: i) heteroatom-based activators, ii) metal-based activators, and iii) carbon-based activators among which α-aminoalkyl radicals have taken the center stage. Access to these α-aminoalkyl radicals as XAT reagents has gained significant attention in the past few years due to the robustness of the reactions, the simplicity of the reagents required, and the broadness of their applications. Generation of these α-aminoalkyl radicals is simply achieved through the single electron oxidation of tertiary amines, which after deprotonation at the α-position generates the α-aminoalkyl radicals. Due to the wide scope of tertiary amines available and the tunable nucleophilicity of α-aminoalkyl radical formed, this strategy has become an attractive alternative to heteroatom/metal-based radicals for XAT. In this minireview, we focus our attention on recent (2020–2023) developments and uses of this robust technology to mediate XAT processes.

Irreversible Structural Phase Transition in [(9‐triptycylammonium) ([18]crown‐6)][Ni(dmit)2]: Origin and Effects on Electrical and Magnetic Properties

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Irreversible Structural Phase Transition in [(9-triptycylammonium) ([18]crown-6)][Ni(dmit)2]: Origin and Effects on Electrical and Magnetic Properties

Two salts, [(9-triptycylammonium)([18]crown-6)][Ni(dmit)2] (1) and [(9-triptycylammonium)([15]crown-5)][Ni(dmit)2] (2) were prepared and characterized. [Ni(dmit)2]− formed dimers in 1 but was arranged in zigzag stacks in 2. At 381 K, 1 underwent an irreversible phase transition originating from the rearrangement of [Ni(dmit)2] dimers and therefore experienced a drastic change in magnetic and electrical properties.


Abstract

Materials exhibiting irreversible phase transitions, leading to changes in their properties, have a potential for novel application in electronic components such as a non-rewritable high-security memory. Here, we focused on the two salts, [(9-triptycylammonium)([18]crown-6)][Ni(dmit)2] (1) and [(9-triptycylammonium)([15]crown-5)][Ni(dmit)2] (2), which featured 2D sheet structures with alternately stacked cation and anion layers. Both salts exhibit similar cation arrangements, however, their anion arrangements differ significantly. The temperature-dependent magnetic susceptibilities of 1 and 2 were well reproduced by the alternating chain model (J AC1/k B=−306(8), J AC2/k B=−239(3) K) and the Curie-Weiss model (θ=−3.9(1) K), respectively. 1 experience a reversible phase transition around 40–60 K, causing anomalies in magnetic behavior. Moreover, an irreversible single-crystal-to-single-crystal phase transition to 1′ undergo at ~381 K, inducing a rearrangement of [Ni(dmit)2]− anions and a resistivity decrease from 6.5×106 to 6.5×102 Ω cm. The susceptibility curve of 1′ was reproduced by a combination of the Curie-Weiss and dimer models (J dimer/k B=−407(5), θ=−26.7(5) K). The irreversible transition of 1 is the first example for such supramolecule and [Ni(dmit)2]− system to our knowledge, in opening potential new-type materials.

The Role of Trp79 in β‐Actin on Histidine Methyltransferase SETD3 Catalysis

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The Role of Trp79 in β-Actin on Histidine Methyltransferase SETD3 Catalysis

Second site: A distant Trp79 binding site modulates the histidine methyltransferase SETD3-catalysed methylation of His73 in β-actin. Our findings have implications for the identification of new substrates and chemical probes of biomedically important SETD3.


Abstract

Nτ-methylation of His73 in actin by histidine methyltransferase SETD3 plays an important role in stabilising actin filaments in eukaryotes. Mutations in actin and overexpression of SETD3 have been related to human diseases, including cancer. Here, we investigated the importance of Trp79 in β-actin on productive human SETD3 catalysis. Substitution of Trp79 in β-actin peptides by its chemically diverse analogues reveals that the hydrophobic Trp79 binding pocket modulates the catalytic activity of SETD3, and that retaining a bulky and hydrophobic amino acid at position 79 is important for efficient His73 methylation by SETD3. Molecular dynamics simulations show that the Trp79 binding pocket of SETD3 is ideally shaped to accommodate large and hydrophobic Trp79, contributing to the favourable release of water molecules upon binding. Our results demonstrate that the distant Trp79 binding site plays an important role in efficient SETD3 catalysis, contributing to the identification of new SETD3 substrates and the development of chemical probes targeting the biomedically important SETD3.

Adducts of Bicyclic (Alkyl)(Amino)Carbene with ECl3 and Three Electron Reduction Thereof: Syntheses of BICAAC Stabilized E−E Bonded Compounds (E=P, Sb)

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Adducts of Bicyclic (Alkyl)(Amino)Carbene with ECl3 and Three Electron Reduction Thereof: Syntheses of BICAAC Stabilized E−E Bonded Compounds (E=P, Sb)

We present the first BICAAC adducts of ECl3 (E=P, Sb) and a phosphaalkene, (BICAAC)=P−Ph stabilized by BICAAC (BICAAC=bicyclic (alkyl)(amino)carbene)). Further, strong π-acceptor character of BICAAC has been exploited in three electron reduction of the BICAAC:ECl3 adducts and afforded the bis(BICAAC)P2 and bis(BICAAC)Sb2 dinuclear compounds with the pnictogen elements in low valent state.


Abstract

The stoichiometric reaction of bicyclic (alkyl)(amino)carbene (BICAAC) with group 15 chlorides, ECl3 (E=P, Sb) to form the Lewis adducts BICAAC:ECl3 (E=P (1), Sb (2)) has been investigated in the present work. The BICAAC smoothly reacts with PPhCl2 to form [BICAAC:PPhCl2] which on in-situ two electron reduction with 2 equivalents of KC8 afforded the phosphinidene complex, BICAAC=P-Ph (3). Complete dechlorination of the BICAAC-ECl3 adducts 1 and 2 with 3 equivalents of KC8 leads to three-electron reduction to afford low-valent trans bent bis(BICAAC)E2 complexes (E=P (4) and Sb (5)). These complexes are the first examples of BICAAC adducts with pnictogens and all the complexes have been characterized by different spectroscopic techniques and their solid-state structure have been elucidated by single crystal X-ray diffraction.

Effect of para‐Substituents on meso‐Functionalized Oxidovanadium(IV) Porphyrins as Catalysts for Oxygen Atom Transfer Mediated Oxidation of Benzoin to Benzil under Mild Conditions

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Effect of para-Substituents on meso-Functionalized Oxidovanadium(IV) Porphyrins as Catalysts for Oxygen Atom Transfer Mediated Oxidation of Benzoin to Benzil under Mild Conditions

meso-Functionalized vanadyl porphyrins were employed as efficient catalysts for oxidizing benzoin to benzil via oxygen atom transfer using DMSO or aq. H2O2 as an oxidant.


Abstract

Systematic analysis of the effect of para-substituents (H, Cl, Br and OMe) on the meso-phenyl group in vanadyl meso-tetraphenylporphyrins ([VIVO(TPP)] (R=H, 1), [VIVO(TCPP)] (R=Cl, 2), [VIVO(TBPP)] (R=Br, 3) and [VIVO(TMPP)] (R=OMe, 4)) on their properties and catalytic oxygen atom transfer (OAT) for oxidation of benzoin to benzil using DMSO as well as 30 % aqueous H2O2 as the sacrificial oxygen source have been studied. Electrochemical and theoretical (density functional theory) studies are in good agreement with the influence of these substituents on the catalytic property of these complexes. Complex [VIVO(TCPP)] (2) displayed the best catalytic activity for the conversion (92 %) of benzoin to benzil in 30 h with >99 % product selectivity when DMSO was used as an oxygen source, whereas excellent conversion (~100 %) of benzoin to benzil was noticed in 18 h with 95 % product selectivity when 30 % aqueous H2O2 was used as a source of oxygen. Furthermore, among these complexes, the electron-withdrawing nature of the chloro substituent at the p-position of meso-phenyl group significantly influences the oxygen atom transfer. Experimental and simulated EPR studies confirmed the +4 oxidation of vanadium in these complexes. The structure of 2, 3 and 4, confirmed by single crystal X-ray diffraction method, are domed in shape, and the displacement of V(IV) ion from the mean porphyrin plane follows the order: 2 (0.458 Å) <3 (0.459 Å) <4 (0.479 Å). We observed that the electron-withdrawing nature of chloro substituent at the p-position of meso-phenyl group influence the oxygen atom transfer from vanadyl porphyrin to dimethyl sulfide much.

A Review of Polymer Electrolyte Fuel Cells Fault Diagnosis: Progress and Perspectives

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A Review of Polymer Electrolyte Fuel Cells Fault Diagnosis: Progress and Perspectives

By combining detailed knowledge acquired from the established off-line characterisation of fuel cells with a careful categorisation of signatures of faults from on-line measurements, it may be possible to develop a complex and accurate understanding of the health state of electrochemical systems from more simple sensing when advanced machine learning and data-driven approaches are taken.


Abstract

Polymer electrolyte fuel cells (PEFCs) are regarded as a substitution for the combustion engine with high energy conversion efficiency and zero CO2 emissions. Stable system operation requires control within a relatively narrow range of operating conditions to achieve the optimal output, leading to faults that can easily cause accelerated degradation when operating conditions deviate from the control targets. Performance recovery of the system can be realized through early fault diagnosis; therefore, accurate and effective diagnostic characterisation is vital for long-term serving. A review of off-line and on-line techniques applied to the fault diagnosis of fuel cells is presented in this work. Off-line approaches include electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic charge (GSC), visualisation-based and image-based techniques; the on-line methods can be divided into model-based, data-driven, signal-based and hybrid methods. Since each methodology has advantages and drawbacks, its effectiveness is analysed, and limitations are highlighted.

A Dibismuthane with Olefin Functional Groups: Towards Tridentate Hybrid Chalcogen/Olefin Ligands

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A Dibismuthane with Olefin Functional Groups: Towards Tridentate Hybrid Chalcogen/Olefin Ligands

The Front Cover shows the evolution of a dibismuthane with olefin functional groups to give a set of potential hybrid ligands featuring chalcogen and olefin coordination sites. In the picture, a dibismuthane caterpillar is moving along a branch towards a delicious meal of chalcogen leaves. The facile insertion of elemental chalcogens into the Bi−Bi bond transforms the caterpillars into colorful butterflies, with a central Bi−E−Bi motif, fluttering around a mountain meadow. DFT calculations were used to investigate the potential of these bismuth compounds to act as tridentate chalcogen/olefin ligands towards a variety of transition metals. These metal atoms are represented by blue flowers in the picture, attracting the butterflies to form a range of coordination entities. More information can be found in the Research Article by C. Lichtenberg and co-workers.