Metal-polymer complexes of cobalt(II) and Copper(II) with hyperbranched polyester polycarboxylic acids

Hyperbranched polyester polycarboxylic acids of the second and third generations for use as high-efficiency complexing agents are synthesized. On the basis of these compounds, new metal-polymer complexes of cobalt(II) and copper(II) are prepared for the first time. As evidenced by IR and ERR studies, the central atom in these metal polycarboxylates occurs in the axially symmetric system MO₆. The thermal stability of polymer copper complexes is improved with increases in the content of metal ions, the degree of functionalization, and the generation number of the polyacid platform.     

Electrochemical reduction and quantification of menadione in sodium dodecyl sulfate micellar media

Menadione cyclic voltammograms show a pair of redox steps on glassy carbon electrode in 0.1 M H₃PO₄ with potential separation of 343 mV. Cationic, nonionic, and anionic surfactants micellar media significantly decrease the menadione peak potential separation. Statistically significant increase of menadione reduction current (3- and 4.4-fold) has been observed in Triton X 100 and sodium dodecyl sulfate (SDS) micellar media, respectively. Electrochemical reduction of menadione in 9 mM SDS micellar media is reversible diffusion-controlled one-electron process corresponding to formation of relatively stable semiquinone anion radical. The linear dynamic ranges of menadione determination are 7–560 and 600–2,550 μM with the limits of detection and quantification of 1.66 and 5.53 μM, respectively. The current concentration sensitivity is (8.6?±?0.2)?×?10³ μA μM^?1. The voltammetric method for the determination of menadione in pharmaceutical “Aekol” based on preliminary extraction with ethanol has been developed.     

Compatibility of olefinic thermoelastoplastics with oxidized bitumens of various colloidal structures

The compatibility of oxidized bitumens of types I and III with blended olefinic thermoelastoplastics was studied by calorimetry, viscometry, and atomic-force microscopy. Improvement of process characteristics of modified products based on bitumens is asssociated with different mechanisms of formation of their structure.     

Cationic polyisoprene: Synthesis,structure, and some properties

Russian Journal of Applied Chemistry - The effect of the catalyst composition and temperature on the cationic polymerization of isoprene in the presence of the catalytic system...     

Binding of 1,5-bis(p-sulfonatophenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane with tetramethylviologen calix[4]resorcin with a methyl radical in the resorcinol ring

The binding of the amphiphilic 1,5-bis(para-sulfonatophenyl)-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane dianion (APCO^2?) with the octacation of the amphiphilic tetramethylviologen calix[4]resorcin having a methyl radical in the resorcinol ring (MVCA-C ₁ ⁸⁺ ) in 30% aqueous DMSO in a 0.1M NaCl supporting solution was studied by various methods. The dianion was bound at the upper rim of calixresorcin due to the donor-acceptor interactions between the viologen acceptor units and the nitrogen- and phosphorus-centered electron-donor fragments of APCO^2? and at the lower rim due to hydrophobic interactions. The composition of the complex depended on the MVCA-C ₁ ⁸⁺ : APCO^2? ratio. The complexes aggregated, forming insoluble precipitates. MVCA-C ₁ ⁸⁺ -APCO^2? is a system with reversibly electro-switchable aggregation. The starting MVCA- ₁ ⁸⁺ octacation partially bound APCO^2?, a certain quantity of both substrates remaining in a free state in solution. The MVCA-C ₁ ^4+· tetraradical tetracation formed as a result of the reduction of MVCA-C ₁ ⁸⁺ completely bound APCO^2? due to hydrophobic interactions when the MVCA-C ₁ ⁸⁺ : APCO^2? ratio was 1: 3. The reversible oxidation of MVCA-C ₁ ^4+· to the starting MVCA-C ₁ ⁸⁺ octacation brought the system back to its starting state     

Determination of the antioxidant capacity of the micellar extracts of spices in Brij® 35 medium by differential pulse voltammetry

It was established that the micellar extracts of spices are electrochemically active on a glassy carbon electrode modified with cerium dioxide nanoparticles in a 0.02 M Brij® 35 in the presence of a phosphate buffer solution (pH 7.4) under the conditions of differential pulse voltammetry. The number of oxidation steps and their potentials vary over a wide range depending on the type of spice. A number of the oxidation peaks of the micellar extracts of spices were identified based on the oxidation potentials of the following individual antioxidants: gallic acid, ferulic acid, p-coumaric acid, caffeic acid, rosmarinic acid, thymol, eugenol, vanillin, syringaldehyde, capsaicin, rutin, quercetin, catechin, tannin, and curcumin. The contribution of the main antioxidants to the amperometric response of the extracts was confirmed by the standard addition method. A procedure for the voltammetric determination of the antioxidant capacity of the extracts of spices based on the oxidation of their antioxidants was developed. The antioxidant capacity of spices was evaluated from the total area of the oxidation steps in units of gallic acid, whose analytical range, detection limit, and determination limit were 50–2490, 11.9, and 39.6 μM, respectively. Twenty types of spices were analyzed. Positive correlations of the antioxidant capacity with the ferric reducing power and the antioxidant activity (r = 0.8971 and 0.9127, respectively at r_crit = 0.497) were found.     

Electrochemical behavior and voltammetric determination of cysteine and cystine at carbon-paste electrodes modified with metal phthalocyanines

The electrochemical behavior of cysteine and cystine on carbon-paste electrodes modified with Fe(II), Co(II), Ni(II), and Cu(II) phthalocyanines is studied. Metal phthalocyanines exhibit catalytic activity in the electrooxidation of cysteine and cystine and in the reduction of cystine. The best catalyst is the cobalt complex. In the electrooxidation of cysteine, the catalysts are electrogenerated complex species of Co(II)Pc or Co(III)Pc⁺, and in the oxidation of cystine, oxidized or reduced forms of the coordinated ligand. Various versions of the determination of cysteine and cystine by the electrocatalytic reactions on the modified electrodes are proposed.     

Two-step one-pot electrosynthesis and catalytic activity of xCoO–yCo(OH)2-supported silver nanoparticles

Journal of Solid State Electrochemistry - Efficient two-step electrosynthesis of xCoO–yCo(OH)2 (CoOxHy)-supported silver nanoparticles (AgNPs) is carried out in N,N-dimethylformamide (DMF)...     

The Complexation Properties of the Water-Soluble Tetrasulfonatomethylcalix[4]resorcinarene toward α-Aminoacids

The flexible bowl-type water-soluble molecule1, consisting of a resorcinol core and fourconvergent tetrasulfonatomethylene groups, existingas a tetraanion in neutral water solution, was studiedas the host molecule for recognition of-aminoacids. Out of 12 examined guestmolecules only those possessing aromatic hydrophobicmoieties or a long hydrophobic chain with a second ionogenic groupform inclusion complexes with 1. The complex formationwas considered with the help of both ¹H NMRand pH-metric titration in a broad range of pH.The role of host and guest geometric complementarity aswell as additional – and hydrophobic interactionsis discussed. The lack of these interactions inaqueous media provides domination of the guestsolvation by water over the 1 : 1 complexformation with 1.