Influence of the Nature of Crosslinking Agent on the Oxidation Behavior of Crosslinked Polystyrene‐Supported Polyoxyethylene Bound Permanganate

Abstract

Polystyrene‐supported polyoxyethylene (PSPOE) bound permanganate with varying crosslinking agents have been prepared and used as a new class of recyclable oxidizing agents for low molecular weight alcohols and aldehydes. The effect of the nature of crosslinking agents on the oxidation reactions was studied in detail. The crosslinking agents used were ethyleneglycol dimethacrylate (EGDMA), 1,4‐butanediol dimethacrylate (BDDMA), and 1,6‐hexanediol diacrylate (HDODA). Polymer supports were synthesized by free radical suspension polymerization. Chloromethylation was done using the Friedel‐Crafts reaction. A cyclic polyether type compound was developed by the reaction of functionlized resin with polyethylene glycol (PEG₆₀₀) and sodium. Polystyrene‐supported polyoxyethylene was equilibrated with potassium permanganate in benzene to give the oxidizing agent. The results reveal that the reactivity of HDODA‐crosslinked system shows higher reactivity than the BDDMA, and EGDMA‐crosslinked systems. This is due to higher flexibility of the HDODA‐crosslinked system compared to the BDDMA, and EGDMA‐crosslinked systems. The effect of solvent, temperature, and molar concentration of the reagent on oxidation were carried out using benzoin to benzil as the model reaction. For a less flexibile EGDMA‐crosslinked resin, tetrahydrofuran (THF) is the best solvent, for BDDMA‐crosslinked system dioxane and for the highly flexible HDODA‐crosslinked system CHCl₃ is found to be best. In all cases, the reactivity of the reagent increased with an increase in temperature and molar excess of the reagent.     

Studies on the Effect of Glass Transition on the Crystalline Transition in Syndiotactic Polystyrene – Solvent Complexes

Summary: Amorphous syndiotactic polystyrene (sPS) was crystallized at room temperature in Norbornadiene (bicyclo[2,2,1]-hepta-2,5-diene), Mesitylene (1,3,5- Trimethylbenzene), 3-Carene (3,7,7-trimethyl bicyclo[4,1,0]hept-3-ene) and DMN (1,4-Dimethylnaphthalene) to form the sPS-solvent complex (δ form) with respective solvent molecules. In situ HTFTIR studies showed that the δ form to γ form transformation temperature occurs well below the glass transition temperature of sPS, which is depressed due to the presence of solvent in the amorphous phase; higher the solvent content in the complex, lower the transition temperature. Glass transition temperatures determined by Modulated differential scanning calorimetry (MDSC) coincide with the transition temperatures, indicating that the δ form transforms into γ form at the glass transition temperature for these complexes. Such a behavior is very different from the behaviour of the sPS- solvent complexes formed by dichloromethane, chloroform, toluene, o-dichlorobenzene, decalin (cis-trans) etc. and for these complexes the transition occur well above the T_g. 1     

On the Nature of the Cherdyntsev–Chalov Effect

It is shown that the Cherdyntsev–Chalov effect, usually presented as the separation of even isotopes of uranium upon their transition from the solid to the liquid phase, can include initiated acceleration of the radioactive decay of uranium-238 nuclei during the formation of cracks in geologically (seismic and volcanically) active zones of the Earth’s crust. The fissuring of the solid-phase medium leads to an increase in mechanical tensile stress and the emergence of strong local electric fields, resulting in the injection of chemical-scale high-energy electrons into the aqueous phase of the cracks. Under these conditions, the e^? catalytic decay of uranium-238 nucleus studied earlier can occur during the formation of metastable protactinium-238 nuclei with locally distorted nucleon structure, which subequently undergo β^–decay with the formation of thorium-234 and helium-4 nuclei as products of the fission of the initial uranium-238 nucleus with a characteristic period of several years. The observed increased activity of uranium-234 nuclei that form during the subsequent β-decay of thorium and then protactinium is associated with the initiated fission of uranium-238. The possibility is discussed of developing thermal power by using existing wastes from uranium production that contain uranium-238 to activate this isotope through the mechanochemical processing of these wastes in aqueous media with the formation of ₉₁ ²³⁸ Pa _isu , the half-life of which is several years.     

Effect of the Metal within Regioisomeric Paddle-Wheel-Type Metal–Organic Frameworks

The effect of metal on the degree of flexibility upon evacuation of metal–organic frameworks (MOFs) has been revealed with positional control of the organic functionalities. Although Co-, Cu-, and Zn-based DMOFs (DMOF = DABCO MOF, DABCO = 1,4-diazabicyclo[2.2.2]octane) with ortho-ligands (2,3-NH₂Cl) have frameworks that are inflexible upon evacuation, MOFs with para-ligands (2,5-NH₂Cl) showed different N₂ uptake amounts after evacuation by metal exchange. Considering that the structural analyses were not fully sufficiently different to explain the drastic changes in N₂ adsorption after evacuation, quantum chemical simulation was explored. A new index (η) was defined to quantify the regularity around the metal based on differences in the oxygen-metal-oxygen angles. Within 2,5-NH₂Cl, the η value becomes larger as the metal are varied from Co to Zn. A large η value means that the structures around the metal center are less ordered. These results can be used to explain flexibility changes upon evacuation by altering the metal cation in this regioisomeric system.     

Effect of the Nature of the Polymer Matrix on the Luminescence of Tb(III) Complexes with β-Diketone Copolymers

The formation conditions and luminescence of Tb(III) complexes with synthesized copolymers of unsaturated acetylacetone derivatives with styrene and methyl methacrylate were studied. The luminescence intensity of these Tb(III) complexes was found to depend on the β-diketone substituent nature (CH₃, CF₃, C₆H₅) and structure (linear, branched) and the β-diketone to monomer ratio in the polymerizing mixture.     

Synthesis and Characterization of Two Extended High-dimensional Architectures Formed by Transition Metal–Glycine Complexes

Under the same experimental condition, changing the kinds of the transition metal (TM) of the reaction, we gained two new compounds: Na₃[Cu(Gly)₂][Cr(OH)₆Mo₆O₁₈]·13H₂O 1, and NaCo₂(gly)₆ClO₄ 2. Compound 1 exhibits an unusual three-dimensional (3D) network constructed from [Cr(OH)₆Mo₆O₁₈]³⁻ building blocks, trinuclear Na⁺ ions and [Cu(gly)₂] coordination complexes as linkers, representing the first example of a 3D extended framework based on Anderson type polyanions and amino acid molecules. Compound 2 consists of an unusual 3D network grafted with Na[Co(gly)₃]₆ complexes. Moreover, compound 2 contains left-handed and right-handed helical chains. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of the Acid–Base Properties of the Support on the Activity of Pd–Zeolite Catalysts for CO Oxidation

The effect of the acid–base properties of zeolite Y on the activity of palladium–zeolite catalysts for CO oxidation was studied. The modification of the support with basic additives was found to improve the catalyst activity. A linear correlation between the ratio between the amounts of O₂and CO adsorbed on the surface of palladium and the catalyst activity was established.     

Effect of Acetylene on the γ-Ray Crosslinking Polymerization of Various Kinds of Acrylic Monomers

The γ-radiation-induced crosslinking polymerization of methyl methacrylate (MMA), methacrylic acid (MAA), 2-hydroxyethyl methacrylate (HEMA), methyl acrylate (MA), and acrylic acid (AA) was carried out in bulk. The polymerization rates of AA and HEMA were much larger than those of other monomers. Acetylene had no influence on the polymerization rate in the initial stage, and the rate was dependent only on the kinds of monomers. In the absence of acetylene, gelation took place in PMA, PAA, and PHEMA obtained at complete conversion, but not in PMMA and PMAA. By the addition of acetylene, complete gelation of PMMA was observed, but no gel formation was observed for PMAA. Volume and weight swelling ratios were measured for PMA, PAA, PHEMA, and PMMA with complete gelation. It was found that by the addition of acetylene the molar concentration of crosslinks increased as much as about twice for PMA and PHEMA, and over about one hundred times for PMMA AND PAA. The relation between volume S_v and weight swelling ratio S_w was studied theoretically. S_v was expressed by the the equation, S_v = (p_p /p+)S_w+ (1 -p_p/p_s), as a function of S_w and the densities of pure polymer (p_p) and solvent (p_s) in swollen polymer.     

Effect of ionic strength on the stabilities of ciprofloxacin – Metal complexes

Proton–ligand dissociation constant of 1-cyclopropyl-1,4-dihydro-4-oxo-7-(1-piperazinyl) quinolone-3-carboxylic acid is ciprofloxacin and metal–ligand stability constants of its complexes with some metal ions have been determined potentiometrically in the presence of (0.01, 0.02 and 0.03 mol/dm³) NaClO₄. The order of the stability constants of the formed complexes increases in the sequence Cu²⁺, Fe³⁺, Ni²⁺ and Zn²⁺ and decreases with increase in the concentration of ionic strength.     

Effect of Additive Agent on the Electrochemical Capacitance of Activated Carbon

In order to compare the effect of additive agent on the electrochemical capacitance of activated carbon, three additive agents like carbon nanotubes (CNTs), activated carbon fibre (ACF) and acetylene black (AB) were added to activated carbon by ultrasonic dispersion. Two electrodes including 95wt.% activated carbon, 2wt.% additive agent and 3wt.% PTFE binder were prepared. ECs were assembled in an argon-filled glove box by sandwiching a microporous separator (Celgard 2400) between two ele…     

Effect of L‐Aspartate Concentration on the Response of the Amperometric L‐Glutamate Sensor for the Measurement of L‐Glutamate and Aspartate Aminotransferase Activity in Serum

Abstract

L‐glutamate oxidase was immobilized in a photo‐cross‐linkable polymer membrane on a palladium strip electrode for the amperometric measurement of aspartate aminotransferas eactivity. The sample, serum for example, was injected into a buffered L‐aspartate and α‐ketoglutarate solution. L‐aspartate is the essential substrate and can transfer to L‐glutamate via the aspartate aminotransferase catalyzing reaction. Aspartate aminotransferase activity can be measured by determining the increasing rate of L‐glutamate. Under the optimal condition, the current increasing rate was proportional to the aspartate aminotransferase activity of the sample in the range of 8–200 U/L. The data are in good correlation (R²= 0.998) with data from a commercial aspartate aminotransferase assay kit. Good reproducibility (relative standard deviation=3.03%, n=8) was obtained from a sample with 50 U/L aspartate aminotransferase activity. The sensor is expectable to be applied in a clinical point‐of‐care diagnosis.     

Effect of the Nature of the Template on Formation of the Spatial Structure of Germanium Dioxide under Sol–Gel Synthesis Conditions

We have synthesized for the first time novel forms of germanium dioxide, templated by micellar structures, with hexagonal and/or lamellar spatial structure. We used an original method for detemplating the synthesized materials. We show that it is possible to use these as the basis for obtaining mesophase sorbents, including mesoporous molecular sieves (MMSs). We note that in each specific case, in synthesis of new nanoperiodic and mesoporous materials, including semiconductors, the determining factor is the correct choice of certain template/framework former systems that match with respect to chemical structure and reactivity.     

The Effect of Arg on the Structure Perturbation and Chaperone Activity of α-Crystallin in the Presence of the Crowding Agent,Dextran

α-Crystallin is a protein that is expressed at high levels in all vertebrate eye lenses. It has a molecular weight of 20 kDa and is composed of two subunits: αA and αB. α-Crystallin is a member of the small heat shock protein (sHsps) family that has been shown to prevent protein aggregation. Small molecules are organic compounds that have low molecular weight (<800 Da). Arginin (Arg) is a small molecule and has been shown to prevent protein aggregation through interaction with partially folded intermediates. In this study, the effect of Arg on the chaperone activity of α-crystallin in the presence of dextran, as a crowding agent, against ordered and disordered aggregation of different target proteins (α-lactalbumin, ovotransferrin, and catalase) has been investigated. The experiments were done using visible absorption spectroscopy, ThT-binding assay, fluorescence spectroscopy, and CD spectroscopy. The results showed that in amorphous aggregation and amyloid fibril formation, both in the presence and absence of dextran, Arg had a positive effect on the chaperone action of α-crystallin. However, in the presence of dextran, the effect of Arg on the chaperone ability of α-crystallin was less than in its absence. Thus, our result suggests that crowding interior media decreases the positive effect of Arg on the chaperone ability of α-crystallin. This is a very important issue, since we are trying to find a mechanism to protect living cells against the toxic effect of protein aggregation.     

Origin of the Aggregation-Induced Phosphorescence of Platinum(II) Complexes: The Role of Metal–Metal Interactions on Emission Decay in the Crystalline State

Discerning the origins of the phosphorescent aggregation-induced emission (AIE) from Pt(II) complexes is crucial for developing the broader range of photo-functional materials. Over the past few decades, several mechanisms of phosphorescent AIE have been proposed, however, not have been directly elucidated. Herein, we describe phosphorescence and deactivation processes of four class of AIE active Pt(II) complexes in the crystalline state based on experimental and theoretical investigation. These complexes show metal-to-ligand and/or metal−metal-to-ligand charge transfer emission in crystalline state with different heat resistance against thermal emission quenching. The calculated energy profiles including the minimum energy crossing point between S₀ and T₁ states were consistent with the heat resistant properties, which provided the mechanism for AIE expression. Furthermore, we have clarified the role of metal-metal interaction in AIE by comparing two computational models.     

The Effect of Rare Earth on the Activity of Methanol Synthesis Catalyst

AlthoughtheCuO/ZnO/Al=O,cataIysthasbeenusedasasuccessfulmethan0lsynthesiscatalystfromCOhydrogenationformanyyears,itscatalyticactivityisnothighenoughf0rmethan0Isynthesisfr0mpureCO,hydrogenati0n.Manynewsynthesismethods,includingsol-gelco-precipitati0nmethodandultrasonicsynthesismeth0d,wereusedtopreparethemethanolsynthesiscatalyst"'.Intheliterature,manymetal0xidessuchasZrO,,Cr,O,,Ga,O,,Al,O,,SiO,andTiO,etc.wereaddedintocatalystt0improveitscatalyticactivityandmethanoIselectivity'~'.Howev…     

Effect of Larger Pore Size on the Sorption Properties of Isoreticular Metal–Organic Frameworks with High Number of Open Metal Sites

Four isostructural CPO-54-M metal-organic frameworks based on the larger organic linker 1,5-dihydroxynaphthalene-2,6-dicarboxylic acid and divalent cations (M=Mn, Mg, Ni, Co) are shown to be isoreticular to the CPO-27 (MOF-74) materials. Desolvated CPO-54-Mn contains a very high concentration of open metal sites, which has a pronounced effect on the gas adsorption of N₂, H₂, CO₂ and CO. Initial isosteric heats of adsorption are significantly higher than for MOFs without open metal sites and are slightly higher than for CPO-27. The plateau of high heat of adsorption decreases earlier in CPO-54-Mn as a function of loading per mole than in CPO-27-Mn. Cluster and periodic density functional theory based calculations of the adsorbate structures and energetics show that the larger adsorption energy at low loadings, when only open metal sites are occupied, is mainly due to larger contribution of dispersive interactions for the materials with the larger, more electron rich bridging ligand.     

Effect of Sπ on the Polymerization of Liquid Sulfur and the Nature of Sπ

The Tobolsky-Eisenberg theory serves to explain the equilibrium polymerization of sulfur in terms of the dependence of S₈ (ring) concentration on temperature and the dependence of number-average degree of polymerization on temperature. The predictions of the theory are completely in accord with experiment. In this paper it is shown that it is possible to take the presence of another component in the melt, Sπ, into account, using a slightly modified version of the Tobolsky-Eisenberg theory. When this is done it is found that the earlier conclusions remain valid. The molecular complexity and structure of Sπ is also discussed.     

Effect of the Loading of Metal Salts on the Formation of Fe–Co Solid Solution Nanoparticles in the IR-Pyrolyzed Chitosan Matrix

Russian Journal of General Chemistry - In this study, metal-carbon nanocomposites have been synthesized via the method of simultaneous formation of bimetallic Fe–Co nanoparticles and carbon...     

CD Spectroscopic Study on the Molecular Recognition of Chiral Salen－Metal Complexes

The molecular recognition behavior of the chiral salen-metal complexes towards guest molecules, such as imidazole derivatives and amino-acid ester, was systematically investigated by means of circular dichroism (CD) spectra. The coordination numbers of the host-guest complexes as well as the recognition capability of the salen-metal complexes were explained by character and intensity analyses of the CD spectra.     

Superoxide Dismutase Mimetic Activity of the Metal (II) Complexes of a Dithiocarbamate Derivative of β-Cyclodextrin1

Abstract

The synthesis of a new β-cyclodextrin derivative containing a dithiocarbamate group (3) by condensation of mono-2-methylamino-2-deoxy-β-CD (2) with CS₂ in the presence of NEt₃ is reported. SOD-mimetic activity was found for the Mn(II) and Cu(II) complexes of 2 and 3 (IC₅₀ = 0.76-7.4 μ). To study the influence of the cyclodextrin residue on the catalytic activity of these complexes, a comparison was made with diethylamine and diethyldithiocarbamate complexes. Complexes of 2 and 3 resulted in 1.3 to 11 fold higher activities. An explanation for this observation, in terms of a possible cooperation of the cyclodextrin residue with the catalytic center of the complex, is given.