Experimental Evidence of Long-Lived Electric Fields of Ionic Liquid Bilayers

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Mattia Belotti, Xin Lyu, Longkun Xu, Peter Halat, Nadim Darwish, Debbie S. Silvester, Ching Goh, Ekaterina I. Izgorodina, Michelle L. Coote, and Simone Ciampi
feedproxy.google.com/~r/acs/jacsat/~3/VhMovJk-BuI/jacs.1c06385

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Metal-Free Synthesis of Heteroaryl Amines or Their Hydrochlorides via an External-Base-Free and Solvent-Free C–N Coupling Protocol

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The Journal of Organic Chemistry

The Journal of Organic Chemistry: Latest Articles (ACS Publications)
Authors: Guang-Gao Fan, Bo-Wen Jiang, Wei Sang, Hua Cheng, Rui Zhang, Bao-Yi Yu, Ye Yuan, Cheng Chen, and Francis Verpoort
feedproxy.google.com/~r/acs/joceah/~3/11Vduhz81vs/acs.joc.1c01467

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Selection and Identification of Novel Antibacterial Agents against Planktonic Growth and Biofilm Formation of Enterococcus faecalis

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Journal of Medicinal Chemistry

Journal of Medicinal Chemistry: Latest Articles (ACS Publications)
Authors: Zhong Chen, Kun Song, Yongpeng Shang, Yanpeng Xiong, Zhihui Lyu, Junwen Chen, Jinxin Zheng, Peiyu Li, Yang Wu, Chenjian Gu, Youhua Xie, Qiwen Deng, Zhijian Yu, Jian Zhang, and Di Qu
feedproxy.google.com/~r/acs/jmcmar/~3/YC-8YLs8pb8/acs.jmedchem.1c00939

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Double Proton Transfer Across a Table: The Formic Acid Dimer–Fluorobenzene Complex

Double Proton Transfer Across a Table: The Formic Acid Dimer–Fluorobenzene Complex

Proton transfer via tunneling is a fundamental quantum-mechanical phenomenon. We report rotational spectroscopy measurements of this process in the complex of the formic acid dimer with fluorobenzene. The experiment indicates that this complex exists in the form of a π–π stacked structure. The fluorobenzene environment slows down the proton transfer in this complex compared to the free formic acid dimer.

Abstract

Proton transfer via tunneling is a fundamental quantum-mechanical phenomenon. We report rotational spectroscopy measurements of this process in the complex of the formic acid dimer with fluorobenzene. The assignment of the spectrum indicates that this complex exists in the form of a π–π stacked structure. Each rotational transition of the parent isotopologue exhibits splitting. Isotopic substitution experiments show that the spectral splitting results from double-proton transfer tunneling in the formic acid dimer. Presence of fluorobenzene as a neighboring molecule does not quench the double proton transfer in the formic acid dimer but decreases its tunneling splitting from 341(3) MHz to 267.608(1) MHz. Calculations suggest that the presence of the weakly bounded fluorobenzene does not influence the activation energy of the proton transfer. The fluorobenzene is reoriented with respect to the formic acid dimer during the course of the reaction, slowing down the proton transfer motion.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Weixing Li, Denis S. Tikhonov, Melanie Schnell
onlinelibrary.wiley.com/doi/10.1002/anie.202108242

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Halogen‐Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions

Halogen-Bridged Methylnaphthyl Palladium Dimers as Versatile Catalyst Precursors in Coupling Reactions

Halide-bridged 1- and 2-methylnaphthyl palladium dimers are presented as convenient, yet highly efficient palladium sources for cross-coupling catalysis. The bench-stable complexes smoothly react with various ligands yielding monoligated palladium precatalysts. These display record-setting activity in various catalytic reactions, clearly beyond that achievable by ligand screening alone.

Abstract

Halogen-bridged methylnaphthyl (MeNAP) palladium dimers are presented as multipurpose Pd-precursors, ideally suited for catalytic method development and preparative organic synthesis. By simply mixing with phosphine or carbene ligands, they are in situ converted into well-defined monoligated complexes. Their catalytic performance was benchmarked against state-of-the-art systems in challenging Buchwald–Hartwig, Heck, Suzuki and Negishi couplings, and ketone arylations. Their use enabled record-setting activities, beyond those achievable by optimization of the ligand alone. The MeNAP catalysts permit syntheses of tetra-ortho-substituted arenes and bulky anilines in near-quantitative yields at room temperature, allow mono-arylations of small ketones, and enable so far elusive cross-couplings of secondary alkyl boronic acids with aryl chlorides.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Nardana Sivendran, Nico Pirkl, Zhiyong Hu, Angelino Doppiu, Lukas J. Gooßen
onlinelibrary.wiley.com/doi/10.1002/anie.202110450

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Mechanism of the Photodegradation of A‐D‐A Acceptors for Organic Photovoltaics**

Mechanism of the Photodegradation of A-D-A Acceptors for Organic Photovoltaics**

The photodegradation pathway of acceptor–donor–acceptor-type non-fullerene acceptors with 1,1-dicyanomethylene-3-indanone termini for organic photovoltaics was elucidated as a 6-e electrocyclic reaction between the dicyanomethylene unit and the thiophene ring, followed by a 1,5-sigmatropic hydride shift (see picture). This photoisomerization was accelerated under inert conditions, as explained by DFT calculations predicting a triplet-mediated reaction pathway.

Abstract

Herein, we elucidate the photodegradation pathway of A-D-A-type non-fullerene acceptors for organic photovoltaics. Using IT-4F as a benchmark example, we isolated the photoproducts and proved them isomers of IT-4F formed by a 6-e electrocyclic reaction between the dicyanomethylene unit and the thiophene ring, followed by a 1,5-sigmatropic hydride shift. This photoisomerization was accelerated under inert conditions, as explained by DFT calculations predicting a triplet-mediated reaction path (quenchable by oxygen). Adding controlled amounts of the photoproduct P1 to PM6:IT-4F bulk heterojunction cells led to a progressive decrease in photocurrent and fill factor attributed to its poor absorption and charge transport properties. The reaction is a general photodegradation pathway for a series of A-D-A molecules with 1,1-dicyanomethylene-3-indanone termini, and its rate varies with the structure of the donor and acceptor moiety.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yuxuan Che, Muhammad Rizwan Niazi, Ricardo Izquierdo, Dmitrii F. Perepichka
onlinelibrary.wiley.com/doi/10.1002/anie.202109357

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Front Cover: Synthesis of 2,2’‐Bipyridines through Catalytic C−C Bond Formations from C−H Bonds (Eur. J. Org. Chem. 39/2021)

Front Cover: Synthesis of 2,2’-Bipyridines through Catalytic C−C Bond Formations from C−H Bonds (Eur. J. Org. Chem. 39/2021)

The Front Cover shows – drawn in a cartoon-style illustration – the different strategies to synthesize 2,2′-bipyridines involving a C−H bond functionalization step. On the left side, the three approaches are inlaying in green lines. The catalysts (transition metal) are drawn in a bubble to illustrate the challenge of maintaining their catalytic activity while 2,2’-bipyridines can coordinate and affect their properties. On the right side, the 2,2′-bipyridine is designed as an allegory featuring a pink Cardoon flower for ligands and a bee for metals, showing their mutual bonding. Anne-Sophie Pochet is thanked for taking the original photography on which this cover is built. More information can be found in the Minireview by J.-F. Soulé et al.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Wided Hagui, Kiruthika Periasamy, Jean‐François Soulé
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202101217

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Spectral Signatures of Oxidation States in a Manganese‐Oxo Cubane Water Oxidation Catalyst

Spectral Signatures of Oxidation States in a Manganese-Oxo Cubane Water Oxidation Catalyst

Tracing fingerprints. Key IR and UV/Vis spectroscopic signatures to differentiate oxidation states of the manganese-oxo vanadate catalyst [(Mn4O4)(V4O13)(OAc)3]n are identified. During oxidation from [MnMn] to [Mn], in the UV/Vis spectrum a band at about 570 nm increases while another one at 850 nm vanishes. In the IR spectra, oxidation leads to a remarkable shift of the V=O stretch mode to higher energies.

Abstract

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn4O4)(V4O13)(OAc)3]3−. Simulated IR spectra show that V=O stretching vibrations in the 900–1000 cm−1 region shift consistently by about 20 cm−1 per oxidation equivalent. Multiple bands in the 1450–1550 cm−1 region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of MnIII atoms. Spectroelectrochemical measurements of the oxidation from [MnMn] to [Mn] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Sebastian Mai, Sarah Klingler, Ivan Trentin, Julian Kund, Marcus Holzer, Anastasia Andreeva, Robert Stach, Christine Kranz, Carsten Streb, Boris Mizaikoff, Leticia González
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102583

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Insights on Luminescent Micro‐ and Nanospheres of Infinite Coordination Polymers

Insights on Luminescent Micro- and Nanospheres of Infinite Coordination Polymers

The formation and growth mechanisms of spherical particles of infinite coordination polymers (ICPs) is discussed. Main reported applications for micro- and nanospheres of ICPs exhibiting luminescent behavior are presented, including chemical sensing, light emission, bioimaging and templating by using topotactic transformations. Additional insights on the challenges for future applications are also given.

Abstract

Coordination polymers have been extensively studied in recent years. Some of these materials can exhibit several properties such as permanent porosity, high surface area, thermostability and light emission, as well as open sites for chemical functionalization. Concerning the fact that this kind of compounds are usually solids, the size and morphology of the particles are important parameters when an application is desired. Inside this context, there is a subclass of coordination polymers, named infinite coordination polymers (ICPs), which auto-organize as micro- or nanoparticles with low crystallinity. Specifically, the particles exhibiting spherical shapes and reduced sizes can be better dispersed, enter cells much easier than bulk crystals and be converted to inorganic materials by topotactic transformation. Luminescent ICPs, in particular, can find applications in several areas, such as sensing probes, light-emitting devices and bioimaging. In this review, we present the state-of-the-art of ICP-based spherical particles, including the growth mechanisms, some applications for luminescent ICPs and the challenges to overcome in future commercial usage of these materials.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Guilherme Arroyos, Caroline M. Silva, Lucas B. Theodoroviez, Jonatas E. M. Campanella, Regina C. G. Frem
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202103104

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CdS Reinforced with CoSX/NiCo‐LDH Core‐shell Co‐catalyst Demonstrate High Photocatalytic Hydrogen Evolution and Durability in Anhydrous Ethanol

CdS Reinforced with CoSX/NiCo-LDH Core-shell Co-catalyst Demonstrate High Photocatalytic Hydrogen Evolution and Durability in Anhydrous Ethanol

The new core-shell structured co-catalyst CoSX/NiCo-LDH and CdS are coupled by electrostatic self-assembly to form a composite catalyst 3 %Co/NiCo/CdS, which exhibits high-efficiency hydrogen evolution performance and stability under visible light (λ≥420 nm). CoSX/NiCo-LDH provides sufficient space for the effective load of CdS. Meanwhile, the effective interface contact accelerates the transfer of electrons and jointly promotes the precipitation of hydrogen.

Abstract

At present, inefficient charge separation of single photocatalyst impedes the development of photocatalytic hydrogen evolution. In this work, the CoSX/NiCo-LDH core-shell co-catalyst was cleverly designed, which exhibit high activity and high stability of hydrogen evolution in anhydrous ethanol system when coupled with CdS. Under visible light (λ≥420 nm) irradiation, the 3 %Co/NiCo/CdS composite photocatalyst exhibits a surprisingly high photocatalytic hydrogen evolution rate of 20.67 mmol g−1 h−1, which is 59 times than that of the original CdS. Continuous light for 20 h still showed good cycle stability. In addition, the 3 %Co/NiCo/CdS composite catalyst also shows good hydrogen evolution performance under the Na2S/Na2SO3 and lactic acid system. The fluorescence (PL), ultraviolet-visible diffuse reflectance (UV-vis) and photoelectrochemical tests show that the coupling of CdS and CoSX/NiCo-LDH not only accelerates the effective transfer of charges, but also greatly increases the absorption range of CdS to visible light. Therefore, the hydrogen evolution activity of the composite photocatalyst has been significantly improved. This work will provide new insights for the construction of new co-catalysts and the development of composite catalysts for hydrogen evolution in multiple systems.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yongkang Quan, Guorong Wang, Dujuan Li, Zhiliang Jin
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102726

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Thiophene‐Fused 1,4‐Diazapentalene: A Stable C=N‐Containing π‐Conjugated System with Restored Antiaromaticity

Thiophene-Fused 1,4-Diazapentalene: A Stable C=N-Containing π-Conjugated System with Restored Antiaromaticity

Best of both worlds: The thiophene-fused 1,4-diazapentalene with two C=N bonds (TAP) was synthesized as a stable compound. The fused thiophene rings restored the antiaromatic character of the 8π-electron system diminished by C=N doping while imparting thermal stability. TAP readily underwent hydrogenation owing to the pronounced aromaticity of the hydrogenated product. Moreover, the high electrophilicity of C=N bonds of TAP led to dense π-stacking in the solid state.

Abstract

A thiophene-fused 1,4-diazapentalene (TAP) was rationally designed and synthesized as a C=N-containing 4n π-electron system that exhibits restored antiaromaticity impaired by the doping with C=N bonds. X-ray crystallographic analysis and quantum chemical calculations revealed that the annulation of thiophene rings with the 1,4-diazapentalene moiety resulted in a much higher antiaromaticity than the pristine 1,4-diazapentalene. These effects can be ascribed to the reduced bond alternation of the eight-membered-ring periphery caused by stabilization of the less-stable bond-shifted resonance structure upon increasing the degree of substitution of imine moieties. Consequently, TAP underwent facile hydrogenation even under mild conditions because of its pronounced antiaromaticity and the high aromaticity of the corresponding hydrogenated product H2-TAP. In addition, the electrophilic C=N moieties in TAP led to the formation of a dense π-stacked structure. These results highlight the effect of partial replacement of C=C bonds with C=N bonds in antiaromatic π-electron systems.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Junichi Usuba, Aiko Fukazawa
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202103122

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Hierarchical Self‐Assembly of Amphiphilic β‐C‐Glycosylbarbiturates into Multiresponsive Alginate‐Like Supramolecular Hydrogel Fibers and Vesicle Hydrogel

Hierarchical Self-Assembly of Amphiphilic β-C-Glycosylbarbiturates into Multiresponsive Alginate-Like Supramolecular Hydrogel Fibers and Vesicle Hydrogel

Barbituric acid-mediated Knoevenagel condensation on unprotected carbohydrates enabled the molecular design of amphiphilic β-C-glycosyl barbiturates as hydrogelators. The single-tailed glycoamphiphiles self-assembled into alginate-like multistimuli-triggered and responsive supramolecular hydrogel fibers. While, the double-tailed glycoamphiphiles led to vesicle hydrogels. Barbituric acid proves to be an efficient and versatile chemical toolbox for the access and design of glycoconjugates.

Abstract

Ordered molecular self-assembly of glycoamphiphiles has been regarded as an attractive, practical and bottom-up approach to obtain stable, structurally well-defined, and functional mimics of natural polysaccharides. This study describes a versatile and rational design of carbohydrate-based hydrogelators through N,N’-substituted barbituric acid-mediated Knoevenagel condensation onto unprotected carbohydrates in water. Amphiphilic N-substituted β-C-maltosylbarbiturates self-assembled into pH- and calcium-triggered alginate-like supramolecular hydrogel fibers with a multistimuli responsiveness to temperature, pH and competitive metal chelating agent. In addition, amphiphilic N,N’-disubstituted β-C-maltosylbarbiturates formed vesicle gels in pure water that were scarcely observed for glyco-hydrogelators. Finally, barbituric acid worked as a multitasking group allowing chemoselective ligation onto reducing-end carbohydrates, structural diversity, stimuli-sensitiveness, and supramolecular interactions by hydrogen bonding.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Shun Yao, Robin Brahmi, François Portier, Jean‐Luc Putaux, Jing Chen, Sami Halila
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102950

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The Preparation of a Water‐Soluble Phospholate‐Based Macrocycle for Constructing Artificial Light‐Harvesting Systems

The Preparation of a Water-Soluble Phospholate-Based Macrocycle for Constructing Artificial Light-Harvesting Systems

A novel water-soluble phospholate-based macrocycle (WPCTX) was prepared with satisfying yield and its host-guest properties were investigated. Based on this, tetraphenylethylene guest molecules (G) self-assembled with WPCTX to form WPCTX⊃G nanoparticles (NPs) acting as donors in water. Moreover, two hydrophobic fluorescent dyes, Eosin Y (ESY) and Nile red (NiR), were encapsulated in NPs to construct artificial light-harvesting systems with high antenna effect.

Abstract

On the basis of cyclotrixylohydroquinoylene (CTX), a novel water-soluble phospholate-based CTX derivative (WPCTX) was prepared with facile synthetic procedure and satisfying yield. Several model guest molecules were selected to investigate WPCTX′s host-guest properties. Based on the study of the host and model guest complexation, a tetraphenylethylene derivative from model guest was employed as a guest molecule (G) to form WPCTX⊃G nanoparticles (NPs) with WPCTX through further supramolecular self-assembly in water. Moreover, a hydrophobic fluorescent dye, Eosin Y(ESY) or Nile red (NiR), was encapsulated in WPCTX⊃G NPs to construct two types of artificial light-harvesting systems. Their high antenna effect demonstrated such NPs successfully mimicked light-harvesting systems in nature.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Jianmin Jiao, Guangping Sun, Jikun Zhang, Chen Lin, Juli Jiang, Leyong Wang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102758

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Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

Iodine(I) and Silver(I) Complexes of Benzoimidazole and Pyridylcarbazole Derivatives

Silver(I) complexes of benzoimidazole and carbazole-derived sp2N-containing Lewis bases are synthesized and the isostructural iodine(I) complexes with a strong 3-center 4-electron [N−I−N]+ halogen bond are obtained through the [N−Ag−N]+→[N−I−N]+ cation exchange reaction. The unambiguous confirmation of the complex formation is obtained in the solution state using NMR spectroscopy, and in the solid-state, with single crystal X-ray diffraction.

Abstract

The synthesis of iodine(I) complexes with either benzoimidazole or carbazole-derived sp2N-containing Lewis bases is described, as well as their corresponding silver(I) complexes. The addition of elemental iodine to the linear two-coordinate Ag(I) complexes produces iodine(I) complexes with a three-center four-electron (3c–4e) [N−I−N]+ bond. The 1H and 1H-15N HMBC NMR studies unambiguously confirm the formation of the complexes in all cases via the [N−Ag−N]+→[N−I−N]+ cation exchange, with the 15N NMR chemical shift change between 94 to 111 ppm when compared to the free ligand. The single crystal X-ray crystallographic studies on eight I+ complexes revealed highly symmetrical [N−I−N]+ bonds with I−N bond distances of 2.21–2.26 Å and N−I−N angles of 177–180°, whilst some of the corresponding Ag+ complexes showed a clear deviation from linearity with N−Ag−N angles of ca. 150° and Ag−N bond distances of 2.09–2.18 Å.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Essi Taipale, Marcel Siepmann, Khai‐Nghi Truong, Kari Rissanen
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202103152

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Take a “Snapshot” of New Syntheses, Reactions, and Characterizations from Unusual Unsaturated Ring Strained Group 4 Metallacycles

Take a “Snapshot” of New Syntheses, Reactions, and Characterizations from Unusual Unsaturated Ring Strained Group 4 Metallacycles

Indeed interesting and important: Recently published contributions of unusual unsaturated ring strained Group 4 metallocene metallacycles show new aspects of these compounds. Several new investigations of 7- and 5-membered metalla-cyclocumulenes, 5- and 4-membered metalla-cycloallenes as well as metalla-cyclopentynes, complete the understanding of these compounds. From the theoretical point of view and the reactivity they have a great potential for important synthetic applications.

Abstract

Recently published syntheses, reactions and characterizations of unusual unsaturated ring strained Group 4 metallocene metallacycles like metalla-cyclocumulenes, -cycloallenes and -cycloalkynes with different ring size are updated for the last three years. There exist for some of these metallacycles, depending on the ring size, 7-, 5- and 4-membered compounds. The new results for these metallacycles are summarized here and considered in addition to the former published results. Additionally, several compounds of this type were now characterized by new reactions. For a better understanding of these compounds, some spectroscopical methods as well as theoretical calculations were published. Despite of these all-C-metallacycles, only in some cases the syntheses and reactions for the corresponding hetero-metallacycles were published too. Examples for these metallaheterocyclic compounds will not be considered in this article. All these unusual ring strained compounds have a great potential for a lot of interesting synthetic applications in the future. Additionally, they are very interesting from the theoretical point of view.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Uwe Rosenthal
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102855

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Water‐Assisted Chemical Route Towards the Oxygen Evolution Reaction at the Hydrated (110) Ruthenium Oxide Surface: Heterogeneous Catalysis via DFT‐MD and Metadynamics Simulations

Water-Assisted Chemical Route Towards the Oxygen Evolution Reaction at the Hydrated (110) Ruthenium Oxide Surface: Heterogeneous Catalysis via DFT-MD and Metadynamics Simulations

The present study quantitatively assesses the free-energy barriers behind the OER at the hydrated (110)-RuO2 catalyst surface revealing a noticeable water-assisted reaction pathway where the explicit water environment acts as co-catalyst enhancing the OER.

Abstract

Notwithstanding that RuO2 is a promising catalyst for the oxygen evolution reaction (OER), a plethora of fundamental details on its catalytic properties are still elusive, severely limiting its large-scale deployment. It is also established experimentally that corrosion and wettability of metal oxides can, in fact, enhance the catalytic activity for OER owing to the formation of a hydrated surface layer. However, the mechanistic interplay between surface wettability, interfacial water dynamics and OER across RuO2, and what degree these processes are correlated are still debated. Herein, spin-polarized Density Functional Theory Molecular Dynamics (DFT-MD) simulations, coupled with advanced enhanced sampling methods in the well-tempered metadynamics framework, are applied to gain a global understanding of RuO2 aqueous interface (explicit water solvent) in catalyzing the OER, and hence possibly help in the design of novel catalysts in the context of photochemical water oxidation. The present study quantitatively assesses the free-energy barriers behind the OER at the (110)-RuO2 catalyst surface revealing plausible pathways composing the reaction network of the O2 evolution. In particular, OER is investigated at room temperature when such a surface is exposed to both gas-phase and liquid-phase water. Albeit a unique efficient pathway has been identified in the gas-phase OER, a surprisingly lowest-free-energy-requiring reaction route is possible when (110)-RuO2 is in contact with explicit liquid water. By estimating the free-energy surfaces associated to these processes, we reveal a noticeable water-assisted OER mechanism which involves a crucial proton-transfer-step assisted by the local water environment. These findings pave the way toward the systematic usage of DFT-MD coupled with metadynamics techniques for the fine assessment of the activity of catalysts, considering finite-temperature and explicit-solvent effects.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Fabrizio Creazzo, Sandra Luber
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102356

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The E2 state of FeMoco: Hydride Formation versus Fe Reduction and a Mechanism for H2 Evolution

The E2 state of FeMoco: Hydride Formation versus Fe Reduction and a Mechanism for H2 Evolution

Hydride formation versus Fe reduction: Hybrid quantum mechanics / molecular mechanics calculations were used to explore the the E2 redox state of the iron-molybdenum cofactor of nitrogenase. Two stable isomers were found: a bridging hydride model (with an open belt sulfide-bridge) and a non-hydride model (with two belt sulfides protonated and reduced Fe). A path back to the resting state, by H2 evolution via a hydride-proton reaction was found.

Abstract

The iron-molybdenum cofactor (FeMoco) is responsible for dinitrogen reduction in Mo nitrogenase. Unlike the resting state, E0, reduced states of FeMoco are much less well characterized. The E2 state has been proposed to contain a hydride but direct spectroscopic evidence is still lacking. The E2 state can, however, relax back the E0 state via a H2 side-reaction, implying a hydride intermediate prior to H2 formation. This E2→E0 pathway is one of the primary mechanisms for H2 formation under low-electron flux conditions. In this study we present an exploration of the energy surface of the E2 state. Utilizing both cluster-continuum and QM/MM calculations, we explore various classes of E2 models: including terminal hydrides, bridging hydrides with a closed or open sulfide-bridge, as well as models without. Importantly, we find the hemilability of a protonated belt-sulfide to strongly influence the stability of hydrides. Surprisingly, non-hydride models are found to be almost equally favorable as hydride models. While the cluster-continuum calculations suggest multiple possibilities, QM/MM suggests only two models as contenders for the E2 state. These models feature either i) a bridging hydride between Fe2 and Fe6 and an open sulfide-bridge (terminal SH on Fe6) (E2-hyd) or ii) a double belt-sulfide protonated, reduced cofactor without a hydride (E2-nonhyd). We suggest both models as contenders for the E2 redox state and further calculate a mechanism for H2 evolution. The changes in electronic structure of FeMoco during the proposed redox-state cycle, E0→E1→E2→E0, are discussed.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Albert Th. Thorhallsson, Ragnar Bjornsson
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102730

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The Photophysics and Photochemistry of Melanin‐ Like Nanomaterials Depend on Morphology and Structure

The Photophysics and Photochemistry of Melanin- Like Nanomaterials Depend on Morphology and Structure

Melanin-like materials can be easily prepared from simple precursors upon controlled oxidation/polymerization. In the resulting system, species with different structure and morphology coexist and interact. The overall photophysical and photochemical properties depend in part on the nature of the chromophores formed but also, to a large extent, on the interchromophoric interactions as typical for supramolecular architectures.

Abstract

Melanin-like nanomaterials have found application in a large variety of high economic and social impact fields as medicine, energy conversion and storage, photothermal catalysis and environmental remediation. These materials have been used mostly for their optical and electronic properties, but also for their high biocompatibility and simplicity and versatility of preparation. Beside this, their chemistry is complex and it yields structures with different molecular weight and composition ranging from oligomers, to polymers as well as nanoparticles (NP). The comprehension of the correlation of the different compositions and morphologies to the optical properties of melanin is still incomplete and challenging, even if it is fundamental also from a technological point of view. In this minireview we focus on scientific papers, mostly recent ones, that indeed examine the link between composition and structural feature and photophysical and photochemical properties proposing this approach as a general one for future research.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Alexandra Mavridi‐Printezi, Arianna Menichetti, Moreno Guernelli, Marco Montalti
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202102479

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Mesoscale Frank–Kasper Crystal Structures from Dendron Assembly by Controlling Core Apex Interactions

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Journal of the American Chemical Society

Journal of the American Chemical Society: Latest Articles (ACS Publications)
Authors: Taesuk Jun, Hyunjun Park, Seungbae Jeon, Seungyun Jo, Hyungju Ahn, Woo-Dong Jang, Byeongdu Lee, and Du Yeol Ryu
feedproxy.google.com/~r/acs/jacsat/~3/SBVoIIoY7KA/jacs.1c07313

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Discovery of Potent, Selective, and Brain-Penetrant Apoptosis Signal-Regulating Kinase 1 (ASK1) Inhibitors that Modulate Brain Inflammation In Vivo

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Journal of Medicinal Chemistry

Journal of Medicinal Chemistry: Latest Articles (ACS Publications)
Authors: J. Howard Jones, Zhili Xin, Martin Himmelbauer, Michael Dechantsreiter, Istvan Enyedy, Joseph Hedde, Terry Fang, Janaky Coomaraswamy, Kristopher W. King, Paramasivam Murugan, Joseph C. Santoro, Thomas Hesson, Dirk M. Walther, Ru Wei, Fengmei Zheng, Douglas J. Marcotte, Kerri Spilker, P. Rajesh Kumar, Ying Liu, Rab Gilfillan, and Felix Gonzalez-Lopez de Turiso
feedproxy.google.com/~r/acs/jmcmar/~3/49kcLggHwyU/acs.jmedchem.1c01458

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Development of BromoTag: A “Bump-and-Hole”–PROTAC System to Induce Potent, Rapid, and Selective Degradation of Tagged Target Proteins

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Journal of Medicinal Chemistry

Journal of Medicinal Chemistry: Latest Articles (ACS Publications)
Authors: Adam G. Bond, Conner Craigon, Kwok-Ho Chan, Andrea Testa, Athanasios Karapetsas, Rotimi Fasimoye, Thomas Macartney, J. Julian Blow, Dario R. Alessi, and Alessio Ciulli
feedproxy.google.com/~r/acs/jmcmar/~3/BZ-5fvh1QxU/acs.jmedchem.1c01532

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