SERS Detection of Hg2+ using Rhenium Carbonyl Labelled Nanoparticle Films

Posted on 5 September 2023 by

A rhenium carbonyl complex is shown to demonstrate the ability to form a stable silver nanoparticle lustrous film, whilst having a visible response to the presence of Hg²⁺ leading to new materials for “labelled” sensing using surface enhanced Raman spectroscopy.

Abstract

Modified silver nanoparticles with a self-assembled disulfide functionalized 2,2'-bipyridine (L1 and L2) monolayer, and the corresponding rhenium complex [Re(L2)(CO)₃Br] are shown to provide a method to position the nanoparticles at a water/dichloromethane interface forming a lustrous metal-like-liquid film (MeLLF) with a unique SERS response. The film formed using L2 showed divergent behaviour in the presence of a range of metal ions whilst bound to the surface. [Re(L)(CO)₃Br] (where L=2,2'-bipyridine, L1 and L2) in solution demonstrates a selective interaction with Hg²⁺, observed by UV-vis, emission and ¹H NMR spectroscopy, attributed to abstraction of the bromide. This interaction was demonstrated by subtle changes in the characteristic Raman Re-CO stretch at 510 cm⁻¹ both with the MeLLF, and when the film is immobilized in a PVA surface-exposed-nano-sheet (SENS). The work provides proof of concept that the organometallic complexes can be employed as “labels” to generate SERS-active nanoparticle films that possess detection capabilities.

Density functional theory study of the isomerization conversion of the cluster ConMoS (n = 1–5)

Posted on 5 September 2023 by

This study employs density functional theory in conjunction with transition state theory to investigate the isomerization process of the clusters. The analysis predominantly centers on a comprehensive theoretical exploration, encompassing both chemical thermodynamics and dynamic considerations. Additionally, the study predicts the equilibrium constants and spontaneity associated with potential isomerization reactions.

Abstract

To investigate the isomerization transition of cluster Co_nMoS (n = 1–5), we employ density functional theory and transition state theory methods in this study. The cluster is optimized at the B3LYP/def2tzvp quantum chemical level. The results reveal eight isomerization reactions for the clusters Co_nMoS (n = 3, 5). Analyzing the activation energies shows a greater propensity for the isomerization transformation in the forward reaction compared to the reverse reaction. At room temperature, six isomerization transformation processes exhibit rapid conversion to the product configurations. Investigation of the equilibrium constants and application of the Arrhenius formula demonstrate that the cluster isomerization reactions are primarily driven by the forward reactions, with four reactions displaying efficient reactant to product conversion rates. Furthermore, there exists a consistent relationship between the structural complexity of the cluster and the change in entropy value. This study provides theoretical insights into reaction rates and optimization of reaction pathways, facilitating mutual validation and development between experimental and theoretical approaches.

Assessment of the health status of Lake Nokoué (Benin, West Africa) exposed to multiple pollutants during flood season

Posted on 5 September 2023 by

A Nature‐Inspired Antioxidant Strategy based on Porphyrin for Aromatic Hydrocarbon Containing Fuel Cell Membranes

Posted on 4 September 2023 by

Membrane degradation: Proton exchange membrane (PEM) fuel cells convert electrochemical energy into electrical energy. During fuel cell operation reactive oxidizing species are formed that degrade the PEM. We investigated the degradation of a generic aromatic sulfonate-type membrane and its repair by the antioxidant (AO) Cu(II)−porphyrin. We found that the porphyrin AO significantly increases the stability towards radical-induced degradation.

Abstract

The use of hydrocarbon-based proton conducting membranes in fuel cells is currently hampered by the insufficient durability of the material in the device. Membrane aging is triggered by the presence of reactive intermediates, such as HO⋅, which attack the polymer and eventually lead to chain breakdown and membrane failure. An adequate antioxidant strategy tailored towards hydrocarbon-based ionomers is therefore imperative to improve membrane lifetime. In this work, we perform studies on reaction kinetics using pulse radiolysis and γ-radiolysis as well as fuel cell experiments to demonstrate the feasibility of increasing the stability of hydrocarbon-based membranes against oxidative attack by implementing a Nature-inspired antioxidant strategy. We found that metalated-porphyrins are suitable for damage transfer and can be used in the fuel cell membrane to reduce membrane aging with a low impact on fuel cell performance.

Development of Kinase‐Centric Drugs: A Computational Perspective

Posted on 4 September 2023 by nV. Pratap Reddy Gajulapallin

To help overcome challenges in developing kinase inhibitors, many computational methods have been developed over the last few decades, either to complement experimental findings or to forecast kinase inhibitor activity and selectivity. This review provides insight into recent advances in theoretical/computational approaches for the design of new kinase inhibitors with the desired selectivity and optimization of existing inhibitors.

Abstract

Kinases are prominent drug targets in the pharmaceutical and research community due to their involvement in signal transduction, physiological responses, and upon dysregulation, in diseases such as cancer, neurological and autoimmune disorders. Several FDA-approved small-molecule drugs have been developed to combat human diseases since Gleevec was approved for the treatment of chronic myelogenous leukemia. Kinases were considered “undruggable” in the beginning. Several FDA-approved small-molecule drugs have become available in recent years. Most of these drugs target ATP-binding sites, but a few target allosteric sites. Among kinases that belong to the same family, the catalytic domain shows high structural and sequence conservation. Inhibitors of ATP-binding sites can cause off-target binding. Because members of the same family have similar sequences and structural patterns, often complex relationships between kinases and inhibitors are observed. To design and develop drugs with desired selectivity, it is essential to understand the target selectivity for kinase inhibitors. To create new inhibitors with the desired selectivity, several experimental methods have been designed to profile the kinase selectivity of small molecules. Experimental approaches are often expensive, laborious, time-consuming, and limited by the available kinases. Researchers have used computational methodologies to address these limitations in the design and development of effective therapeutics. Many computational methods have been developed over the last few decades, either to complement experimental findings or to forecast kinase inhibitor activity and selectivity. The purpose of this review is to provide insight into recent advances in theoretical/computational approaches for the design of new kinase inhibitors with the desired selectivity and optimization of existing inhibitors.

Recent Advances in Domino Synthesis of Fused Polycyclic N‐Heterocycles Based on Intramolecular Alkyne Hydroamination under Copper Catalysis

Posted on 4 September 2023 by nZefeng Jin, nGuodong Shen, nXin Lvn

Comprehensive Summary

Fused polycyclic N-heterocycles are very important scaffolds in biomedicinal chemistry and materials science. Intramolecular alkyne hydroamination is a powerful method for the construction of N-heterocycles. In the last two decades, copper-catalyzed domino reactions based on intramolecular alkyne hydroamination has emerged as a robust strategy for assembling various fused polycyclic N-heterocycles. Great progress has been achieved in this area. This short review covers the advances made in copper-catalyzed domino synthesis of fused polycyclic N-heterocycles based on this strategy from 2008 to 2023, and will hopefully serve as an inspiration towards the exploration of new copper-catalyzed versions of the transformation. The domino transformations are introduced and discussed from five aspects according to the different key processes involved in these reactions.

Construction of a Metallacyclopentadiene Ring Through the Attack of Carbanions to M≡C Bond Followed by C‐H Activation

Posted on 4 September 2023 by nChun Tang, nShengjie Zhang, nZhengyu Lu, nQian Li, nMing Luo, nDafa Chen, nHaiping Xian

Comprehensive Summary

Metallacyclopentadienes are important metallacycles and regarded as intermediates in many reactions, therefore, new methods to achieve them are anticipated. In this study, a formal [3+2] method, through the reactions of an osmapentalyne with benzyl carbanions, was developed. The reactions underwent a nucleophilic attack of carbanions to the Os≡C bond, followed by C–H activation to form the five-membered osmacyclopentadiene ring. Most of the reactions were carried out at room temperature, the substituents on the aromatic rings of benzyl carbanions are diverse, and the resulting products contain an Os–H bond, representing a novel type of 10C-carbolong complexes. This work provides a new convenient route to construct metallacyclopentadienes, which is expected to further promote the development of such a type of substances.

Exploring Photoswitchable Binding Interactions with Small‐Molecule‐ and Peptide‐Based Inhibitors of Trypsin

Posted on 4 September 2023 by

Different for different states: Small-molecule- and peptide-based photoswitchable inhibitors of trypsin were investigated to better understand their binding interactions and hence optimise the difference in biological activity between isomeric states. The best peptidic inhibitor displayed a more than fivefold difference in inhibitory activity between isomeric states compared to the best small-molecule inhibitor (3.4-fold), due to a more significant 3D structural change upon switching.

Abstract

The ability to photochemically activate a drug, both when and where needed, requires optimisation of the difference in biological activity between each isomeric state. As a step to this goal, we report small-molecule- and peptide-based inhibitors of the same protease—trypsin—to better understand how photoswitchable drugs interact with their biological target. The best peptidic inhibitor displayed a more than fivefold difference in inhibitory activity between isomeric states, whereas the best small-molecule inhibitor only showed a 3.4-fold difference. Docking and molecular modelling suggest this result is due to a large change in 3D structure in the key binding residues of the peptidic inhibitor upon isomerisation; this is not observed for the small-molecule inhibitor. Hence, we demonstrate that significant structural changes in critical binding motifs upon irradiation are essential for maximising the difference in biological activity between isomeric states. This is an important consideration in the design of future photoswitchable drugs for clinical applications.

Sodium Tetrakis(hexafluoroisopropyloxy)aluminates: Synthesis and Electrochemical Characterisation of a Room‐Temperature Solvated Ionic Liquid

Posted on 4 September 2023 by

Ionic liquids: Weakly coordinating anions find ubiquitous use in chemistry. This work details the synthesis of sodium tetrakis(hexafluoroisopropyloxy)aluminate, which when solvated by one dimethoxyethane solvent molecule forms a room-temperature solvated ionic liquid. Thermal and electrochemical studies have been performed on this salt and its use an electrolyte for sodium-ion batteries explored.

Abstract

Weakly coordinating anions (WCAs) are used throughout chemistry to minimise cation-anion interactions in the solid and solution states. The ability to suppress ion-pairing has important bearings - or impacts on the properties of materials, on single-site catalysis and on ionic conductivity. Fluorinated alkoxy aluminates (containing [Al(OR^F)₄]⁻ anions) are an attractive class of WCA owing to their high thermodynamic stability, stemming from strong aluminium-oxygen bonds, and the ability to tailor their steric and electronic properties by changing the organic substituents (R). This work explores the structural and electrochemical properties of sodium tetrakis(hexafluoroisopropyloxy)aluminate, Na[Al(hfip)₄] ⋅ xDME (hfip=hexafluoroisopropyloxy, OⁱPr^F, DME=1,2-dimethoxyethane, x=3 or 1). When solvated with one DME molecule, Na[Al(hfip)₄] ⋅ DME is a room-temperature solvated ionic liquid, with an activation energy of conduction of 0.4 eV. Both Na[Al(hfip)₄] ⋅ 3DME and Na[Al(hfip)₄] ⋅ DME have been studied as electrolyte salts for sodium-ion batteries, where sodium-ion cycling proceeds but with low capacity retention.

Construction of Rings via Metal‐Catalyzed C−H Annulation with Unsymmetrical Internal Alkynes: Selectivity and Applications

Posted on 4 September 2023 by

C−H annulation with alkynes has been demonstrated to be one powerful strategy for the expedient construction of ring systems, while the use of unsymmetrical alkynes often led to elusive regioselectivity. Herein, we summarized recent exploration of this field, including the development of directing groups, catalytic systems, and versatile alkynes, which has led to prosperous achievements toward the application in drugs, natural products, and materials.

Abstract

Selective and concise construction of ring systems that are ubiquitous skeletons across chemistry, drugs and materials, is indispensable for human life. Of note, directed C−H annulation with alkynes for the expedient delivery of ring systems holds great importance, featuring step- and atom-economy, mild conditions, and broad substrate scope. However, regioselectivity issues remained when using unsymmetrical alkynes for the directed C−H annulation. Herein, we summarized recent achievements towards solving this problem by developing directing groups, metal catalysts, and alkynes with versatile and traceless functionality that ensure the overall regioselectivity, enantioselectivity, efficiency, and synthetic application. We hope this concept will promote the further development of the precise construction of functional molecules using C−H annulation with unsymmetrical alkynes.