Novel non-PEG derived polyethers as solid supports. 2. Solid-phase synthesis studies

Novel non-PEG derived polyether resins, coined SLURPS (Superior Liquid Uptake Resins for Polymer-supported Synthesis), were studied for their performance in solid-phase synthesis. Novel amino functional resins, SLURPS-NH2, were prepared with a loading of up to 8.5 mmol/g and employed successfully in the solid-phase synthesis of Leu-Enkephalin. The peptide was obtained with the same purity when compared to its synthesis with commercial standard poly(dimethyl acrylamide) resins. Furthermore we show loading and cleavage of aromatic carboxylic acids in excellent yield. The advantageous solvent compatibility of our support was demonstrated through the biphasic dihydroxylation of alkenes with OsO4 in t-BuOH/water mixtures producing bound 1,2-diols and synthesis and removal of a bound oxime using ethanol/water mixtures both in excellent yields. Reactions were easily monitored by gel-phase NMR and FTIR. These results show that SLURPS are very well suited for organic transformations using highly polar solvent mixtures and reagents and at much higher loading levels than standard amphiphilic resins of similar solvent compatibility.     

Lithium bromide as a flexible, mild, and recyclable reagent for solvent-free Cannizzaro, Tishchenko, and Meerwein-Ponndorf-Verley reactions

A room temperature convenient disproportionation or reduction of aldehydes prompted by lithium bromide and triethylamine is described in a solvent-free environment. Distribution of the products to selectively direct the process toward Cannizzaro or Tishchenko reactions is controlled by the type of workup selection. The presence of hydrogen donor alcohols in the mixture completely diverts the process toward the Meerwein-Ponndorf-Verley reaction.     

N,N'-ethylene-bis(benzoylacetoniminato) copper (II), Cu(C22H22N2O2), a new reagent for aromatization of Hantzsch 1,4-dihydropyridines

A variety of Hantzsch 1,4-dihydropyridines were oxidized to their corresponding pyridines in high yields in the presence of Cu(C22H22N2O2) in refluxing acetic acid.     

Electrochemical synthesis and structural characterization of a novel mixed-valence copper(I)-copper(II) complex: {[bis(ethylenediamine)copper(II)] bis[diiodocuprate(I)]}

A novel, mixed-valent copper(I)-copper(II) complex, {[bis(ethylene-diamine)copper(II)] bis[diiodocuprate(I)]} (1), has been prepared by electrochemical dissolution of a sacrificial copper anode in a solution of ethylenediamine (en), I2 and tetraethylammoniumperchlorate (TEAP) as supporting electrolyte in acetonitrile (AcN)and characterized by single-crystal X-ray structure determination. The crystal structure of the complex 1 shows that it consists of a CuI2 polymer formed from I- ligands bridging Cu(I) ions, with a nearly square planar geometry of bivalent Cu(II) atoms chelated by two ethylenediamine ligands. The results also show that direct electrosynthesis of the complex had high current efficiency, purity and electrolysis yield.     

GC-MS Analysis and Biomedical Therapy of Oil from n-Hexane Fraction of Scutellaria edelbergii Rech. f.: In Vitro,In Vivo,and In Silico Approach

The current study aimed to explore the crude oils obtained from the n-hexane fraction of Scutellaria edelbergii and further analyzed, for the first time, for their chemical composition, in vitro antibacterial, antifungal, antioxidant, antidiabetic, and in vivo anti-inflammatory, and analgesic activities. For the phytochemical composition, the oils proceeded to gas chromatography-mass spectrometry (GC-MS) analysis and from the resultant chromatogram, 42 bioactive constituents were identified. Among them, the major components were linoleic acid ethyl ester (19.67%) followed by ethyl oleate (18.45%), linolenic acid methyl ester (11.67%), and palmitic acid ethyl ester (11.01%). Tetrazolium 96-well plate MTT assay and agar-well diffusion methods were used to evaluate the isolated oil for its minimum inhibitory concentrations (MIC), minimum bactericidal concentration (MBC), half-maximal inhibitory concentrations (IC₅₀), and zone of inhibitions that could determine the potential antimicrobial efficacy’s. Substantial antibacterial activities were observed against the clinical isolates comprising of three Gram-negative bacteria, viz., Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa, and one Gram-positive bacterial strain, Enterococcus faecalis. The oils were also effective against Candida albicans and Fusarium oxysporum when evaluated for their antifungal potential. Moreover, significant antioxidant potential with IC₅₀ values of 136.4 and 161.5 µg/mL for extracted oil was evaluated through DPPH (1,1-Diphenyl-2-picryl-hydrazyl) and ABTS assays compared with standard ascorbic acid where the IC50 values were 44.49 and 67.78 µg/mL, respectively, against the tested free radicals. The oils was also potent, inhibiting the α-glucosidase (IC50 5.45 ± 0.42 µg/mL) enzyme compared to the standard. Anti-glucosidase potential was visualized through molecular docking simulations where ten compounds of the oil were found to be the leading inhibitors of the selected enzyme based on interactions, binding energy, and binding affinity. The oil was found to be an effective anti-inflammatory (61%) agent compared with diclofenac sodium (70.92%) via the carrageenan-induced assay. An appreciable (48.28%) analgesic activity in correlation with the standard aspirin was observed through the acetic acid-induced writhing bioassay. The oil from the n-hexane fraction of S. edelbergii contained valuable bioactive constituents that can act as in vitro biological and in vivo pharmacological agents. However, further studies are needed to uncover individual responsible compounds of the observed biological potentials which would be helpful in devising novel drugs.     

Improving barrier properties of polyethylene/Fe2O3-modified nanographene nanocomposites in a magnetic field

The present work aims at improving the barrier properties of high molecular weight Polyethylene/ graphene nanoplatelets (HMWPE/GnP) nanocomposites by aligning the embedded modified graphene nanoparticles in a magnetic field. Graphene nanoplatelets (GnP) were modified by magnetic Fe₂O₃ to produce Fe₂O₃-modified Graphene, GnP-mFe₂O₃. The magnetic properties of Fe₂O₃ were previously characterized by the vibrating sample magnetometer (VSM) method and resulting GnP-mFe₂O₃ nanoparticles were characterized by Fourier transform infrared (FTIR) analysis. HMWPE/GnP nanocomposites were prepared via melt mixing. The prepared nanocomposites were sheeted at high temperatures in a magnetic field using a hot press. The barrier properties of prepared films, HMWPE/GnP and HMWPE/GnP-mFe₂O₃ were characterized by carrying out a permeation to oxygen experiment as a function of GnP and GnP-mFe₂O₃ contents. A decrease in gas transmission rate (GTR) was observed for the samples after being subjected to the magnetic field compared to the non-treated sample. The results of differential scanning calorimetry (DSC) and field emission electron microscopy (FESEM) experiments confirmed the orientation of GnP-mFe₂O₃ nanoparticles in nanocomposites.     

Development of Membranes and Separators to Inhibit Cross-Shuttling of Sulfur in Polysulfide-Based Redox Flow Batteries: A Review

The global rapid transition from fossil fuels to renewable energy resources necessitates the implementation of long-duration energy storage technologies owing to the intermittent nature of renewable energy sources. Therefore, the deployment of grid-scale energy storage systems is inevitable. Sulfur-based batteries can be exploited as excellent energy storage devices owing to their intrinsic safety, low cost of raw materials, low risk of environmental hazards, and highest theoretical capacities (gravimetric: 2600 Wh/kg and volumetric: 2800 Wh/L). However, sulfur-based batteries exhibit certain scientific limitations, such as polysulfide crossover, which causes rapid capacity decay and low Coulombic efficiency, thereby hindering their implementation at a commercial scale. In this review article, we focus on the latest research developments between 2012–2023 to improve the separators/membranes and overcome the shuttle effect associated with them. Various categories of ion exchange membranes (IEMs) used in redox batteries, particularly polysulfide redox flow batteries and lithium-sulfur batteries, are discussed in detail. Furthermore, advances in IEM constituents are summarized to gain insights into different fundamental strategies for attaining targeted characteristics, and a critical analysis is proposed to highlight their efficiency in mitigating sulfur cross-shuttling issues. Finally, future prospects and recommendations are suggested for future research toward the fabrication of more effective membranes with desired properties.     

Facile Synthesis of 5-Aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides via Suzuki Cross-Coupling Reactions,Their Electronic and Nonlinear Optical Properties through DFT Calculations

Synthesis of 5-aryl-N-(pyrazin-2-yl)thiophene-2-carboxamides (4a–4n) by a Suzuki cross-coupling reaction of 5-bromo-N-(pyrazin-2-yl)thiophene-2-carboxamide (3) with various aryl/heteroaryl boronic acids/pinacol esters was observed in this article. The intermediate compound 3 was prepared by condensation of pyrazin-2-amine (1) with 5-bromothiophene-2-carboxylic acid (2) mediated by TiCl₄. The target pyrazine analogs (4a–4n) were confirmed by NMR and mass spectrometry. In DFT calculation of target molecules, several reactivity parameters like FMOs (E_HOMO, E_LUMO), HOMO–LUMO energy gap, electron affinity (A), ionization energy (I), electrophilicity index (ω), chemical softness (σ) and chemical hardness (η) were considered and discussed. Effect of various substituents was observed on values of the HOMO–LUMO energy gap and hyperpolarizability. The p-electronic delocalization extended over pyrazine, benzene and thiophene was examined in studying the NLO behavior. The chemical shifts of ¹H NMR of all the synthesized compounds 4a–4n were calculated and compared with the experimental values.     

Effect of interface stresses on the elastic deformation of an elastic half-plane containing an elastic inclusion

The effect of the interface stresses is studied upon the size-dependent elastic deformation of an elastic half-plane having a cylindrical inclusion with distinct elastic properties. The elastic half-plane is subjected to either a uniaxial loading at infinity or a uniform non-shear eigenstrain in the inclusion. The straight edge of the half-plane is either traction-free, or rigid-slip, or motionless, which represents three practical situations of mechanical structures. Using two-dimensional Papkovich–Neuber potentials and the theory of surface/interface elasticity, the elastic field in the elastic half-plane is obtained. Comparable with classical result, the new formulation renders the significant effect of the interface stresses on the stress distribution in the half-plane when the radius of the inclusion is reduced to the nanometer scale. Numerical results show that the intensity of the influence depends on the surface/interface moduli, the stiffness ratio of the inclusion to the surrounding material, the boundary condition on the edge of the half-plane and the proximity of the inclusion to the edge.