Synthesis of diethyl 2-{[3-(triethoxysilyl)propyl]amino}ethylphosphonate

Diethyl 2-{[3-(triethoxysilyl)propyl]amino}ethylphosphonate is promising reagent for the modification of silica surface and thus for the creation of chelate adsorbents for extraction of d‑metals ions from water media. Diethyl 2-{[3-(triethoxysilyl)propyl]amino}ethylphosphonate was synthe­sized by alkylation of 3-aminopropyltriethoxysilane (APTES) with diethyl vinylphosphonate under quick neat heating. The possible alternative approaches to the synthesis of this compound were investigated (alkylation of APTES and N-acetylAPTES) as well as behavior of APTES towards heating in absolute ethanol and THF. APTES was shown to be not stable in absolute ethanol, that is caused by polycondensation processes. Because of this fact, previously reported protocol of diethyl 2‑{[3‑(triethoxysilyl)propyl]amino}ethylphosphonate synthesis in ethanol turned to be impossible.

Search for new luminophores with predetermined physicochemical and chemical properties. XIV.N-Arylmethylene- and N-hetarylmethylene derivatives of poly (3‒aminopropene)

The possibility of creating polymers with fluorescence, derivatives of poly (3-aminopropene) (PAP) by alkylation of amino groups with aromatic or heterocyclic aldehydes by Leykart-Wallach reaction with own fluorescence was investigated. Synthesis of N-alkylated PAP derivatives was performed by sequential conversion: acrylamide → PAA (Mν = 100 kDa) → PAP → alkylated PAP. Due to the impossibility of using LiAlH4 to reduce the amide groups of polyacrylamide to amine due to the low solubility of PAA in the non-aqueous (diethyl ether, tetrahydrofuran, etc.) solvents, the reduction of PAA by other reducing agents was optimized. It was found that the best conditions for the reduction of amide groups of PAA to amine - acetic acid - dioxane as a solvent and NaBH4 (suspended in anhydrous 1,4-dioxane) as a reducing agent. According to IR spectroscopy, the products obtained are copolymers of 3-aminopropene (the main amount of elementary units), acrylamide and acrylic acid. To modify the structure of the obtained polymer, the Leuckart-Wallach reaction was used, where the following aldehydes having luminescence were selected: pyrene-3-aldehyde, 2-hydroxy-1-naphthaldehyde, anthracene-9-carbaldehyde, and 3.5 phenyl-1-(4-formylphenyl)-2-pyrazoline. To obtain N-Ar/Het-methylene derivatives, a mixture of PAP, aldehyde and 98% formic acid was heated under harsh conditions (6 hours, glycerol bath), isolated and purified. The obtained modified samples of polymers are intensely fluorescent both in the solid state and in the form of solutions, which indicates the successful passage of the Leykart-Wallach reaction. Spectral characteristics were obtained for solutions in a mixed solvent – ethyl acetate – formic acid (9 : 1). For both the original aldehydes and the copolymers in the mixed solvent used, the spectral fluorescence curves lose their oscillatory structure, probably due to the specific effect of the mixed solvent on the phosphor molecules (for the original aldehydes) and the side methylamino-N-arylmethylene - […СН2-СН(СН2-NH-CH2-Ar)- …] and methylamino-N-getarylmethylene […-СН2-СН(СН2-NH-CH2-Het)-…] groups both in the ground and in the excited state, and for polymers of inhomogeneity of the medium with local polarity zones.

Sorption properties of polymeric beads and films containing tetraoctyl diglycolamide towards europium (III) ions

The article presents results obtained during investigation of Eu(III) ion removal from aqueous solutions using triacetate cellulose films and styrene-divinylbenzene copolymer beads containing tetraoctyl diglycolamide (TODGA). A simple method for manufacturing films containing up to 50 % w/w TODGA is provided. Solution acidity effect on the removal rate of Eu(III) ions was studied. Maximum removal of Eu(III) ions was obtained in nitric acid solutions with concentrations of 1-6 mol/l. Additionally, increase in the europium removal rate is also observed at pH > 2 for beads and in the pH range of 2 to 4 for films. In the former case increase in the removal rate is explained by increase in the nitrate ion concentration in the solution and Eu(NO3)3(TODGA)3 complex formation, and in the latter case – by decrease in TODGA protonation rate with рН growth. Observed trends indicate a high similarity in surface sorption mechanisms between the materials studied. Sorption equilibrium of Eu(III) ions onto the styrene-divinylbenzene copolymer beads impregnated with TODGA is adequately fitted to Langmuir sorption isotherm. The maximum sorption capacity of this material for Eu(III) removal from solutions with nitric acid concentration of 1 mol/l is 7.4 mg/g. It has been found that the maximum removal rate of Eu(III) ions by the triacetate cellulose films is achieved for TODGA content in the films ≥ 40 % w/w. The possibility of selective europium sorption from natural water using both beads and films is shown. Although cations present in natural water do not bind to sorbents studied, there is still slight deterioration in sorption properties when moving from model solutions to natural water. Complete desorption of Eu(III) ions from the film surface is achieved by washing three times with an EDTA solution, рН = 6.8. Prepared films can be reused for Eu(III) ion removal.

Synthesis of 1-(methylsulfonyl)-1-propene and N,N-dimethyl-1-propene-1-sulfonamide

Various vinylsulfones and vinylsulfonamides have a wide range of biological activities (mainly, inhibition of different types of enzymes) and are frequently used in synthetic organic chemistry (as active dienophiles, Michael acceptors and, generally, active agents in 1,4‑addition and electrocyclization reactions). However, despite numerous synthesized substances of this type, the synthetic protocols for the obtaining of the low molecular weight representatives of these compounds – 1‑(methylsulfonyl)-1-propene and N,N‑dimethyl-1‑propene-1-sulfonamide – seem to be still little known. In the present work we report a simple, efficient and general protocol for the dehydrative synthesis of 1‑(methylsulfonyl)-1‑propene and N,N‑dimethyl-1‑propene-1‑sulfonamide starting from corresponding 1-(methylsulfonyl)-2-propanol and N,N‑dimethyl-2‑hydroxypropanesulfonamide, respectively, using MeSO2Cl/organic base system basing on the preliminary experiment of 2‑(4‑bromophenyl)-N,N‑dimethylethenesulfonamide synthesis from 2‑(4‑bromophenyl)-2‑hydroxy-N,N-dimethylethanesulfonamide. The latter in its turn has been obtained starting from N,N‑dimethylmethanesulfonamide by lithiation with n-BuLi, subsequent action of 4‑bromobenzaldehyde and further workup. The applied protocol of vinyl derivatives synthesis allows to avoid isolation of intermediate mesyl derivatives, consisting of one-pot formation of leaving group and its elimination. Accordingly to coupling constants in 1H NMR spectra, synthesized N,N‑dimethyl-1-propene-1‑sulfonamide exists as mixture of E- and Z-isomers (in the ratio 88:12), while isolated 1‑(methylsulfonyl)-1‑propene and 2-(4-bromophenyl)-N,N‑dimethylethenesulfonamide are the most stable E‑isomers. The structures of the synthesized compounds are confirmed by the methods of 1H NMR-spectroscopy and mass-spectrometry.

Atomic absorption and atomic emission with inductive connected plasma detection of Lead and Iron in strata water using new medias and standard composition samples

An influence of SAS (Тriton Х-100) concentration and ultrasound treatment time on the value of analytical signal at atomic absorption and atomic emission with inductive connected plasma detection of analytes in strata water was studied. Maximal analytical signal at of Lead and Iron was reached at using nonionogenic SAS which let us to decrease surface tension of the analyzed solution and to increase absorptivity at analytes detection. It was shown that using of the modern sample preparation increase sensibility of atomic absorption detection of Lead in 1,5 times and Iron in 1,8 times. By the methods of atomic absorption and atomic emission with inductive connected plasma spectroscopy and using acetylacetonates of Lead and Iron as standard composition samples, that let us to increase sensitivity of the detection of analytes, contain of Lead and Iron in strata water was determined. By variation of the sample volume and by "injected-found out" method we have proved that systematic error is not significant. The results, obtained by two independent methods were compared according to F- and t-criteria. It was proved that dispersions are homogenous and run of the means is not sufficient and proved by random scatter. By atomic absorption method we estimated the detection limit of the analytes according to the developed methodic and show that the obtained results are lower than the same data from literature. The developed methodic, according to its metrological characteristics, is competitive at international level.

Quantitative analysis of micellar effect on the reaction rate of cationic triphenylmethine dyes with water according to Berezin’s model

Several approaches quantitatively describe the effect of surfactant micellar solution on the reaction rate. The most used among them are Piszkiewicz’s, Berezin’s, and Pseudophase Ion-Exchange (PIE) models. The last-named was developed by Bunton and Romsted. Piszkiewicz’s model is based on representations of the micellization according to the mass action law with the formation of a catalytic micelle, which consists of some surfactant molecules and a substrate. In our previously paper, this model was used to explain the kinetic micellar effect on the reaction of cationic triphenylmethine dyes with water once again showed the main disadvantages of this approach. Berezin’s model is based on another model of micelle formation viz. the pseudophase model, and the binding of reagents by micelles is considered as the distribution of a substance between two phases. In this work, we aim to consider the applicability of Berezin’s approach for the interaction of malachite green and brilliant green cations with water molecule as a nucleophile in aqueous systems of nonionic, anionic, cationic, and zwitterionic surfactants. On the whole, Berezin's model performed well when applied to the description of the micellar effect on the reaction of similar dye with the hydroxide ion. However, it was revealed that this model does not take into account the change in the local concentration of the HO– ions due to a compression of the double electric layer upon addition of reacting ions to the system, as well as the constant of association of the HO– ions with cationic head groups of surfactant. In this case, when water is used as a nucleophile, the question of the degree of nucleophile binding can be solved differently. The PIE model is also based on a pseudophase model of micellization, but a substrate binding by micelles is considered as an association in a stoichiometric ratio of 1:1, and a nucleophile concentration is expressed in a local concentration based on the neutralization degree of micelles. Given the latter, its approach cannot be applied to the kinetic micellar influence on the reaction of cationic triphenylmethine dyes with water.

Nitroxyl spin probe in ionic micelles: A molecular dynamics study

The compounds containing nitroxyl radical (NO˙) are actively used as spin probes to examine colloid systems, including lipid membranes and micelles. Their electron paramagnetic resonance spectrum provides information about the composition of the medium, in particular, the content of water there. Yet, the proper treatment of the measurement results demands understanding the microscopic characteristics of the molecular probe. In the present paper, we extend our previous studies on the microscopic state of acid-base and solvatochromic probes in surfactant micelles to the field of spin probes. We report the results of molecular dynamics simulation of a common spin probe, methyl-5-doxylstearate, in micelles of anionic (sodium n-dodecyl sulfate, SDS) and cationic (n-dodecyltrimethylammonium bromide, DTAB) surfactants. The localization of the molecule within the micelles, its shape, composition of the local environment, hydration were quantified and compared with the available relevant experimental data. No significant dissimilarity was found in the characteristics of the probe molecule in both kinds of micelles. However, the characteristics of the O˙ atom carrying the unpaired electron are pronouncedly different, namely, in DTAB micelles it is less hydrated and forms less hydrogen bonds with water. Similar situation was observed for the COO group. The main reason was found to be the interactions with cationic surfactant headgroups, which screen the O˙ atom and COO group from water. These findings allowed revisit the point of view that the surface layer of DTAB micelles as a whole is less hydrated in comparison to that of the SDS ones.

Recent advances in theoretical investigation of titanium dioxide nanomaterials. A review

Titanium dioxide (TiO2) is one of the most widely used nanomaterials in many emerging areas of material science, including solar energy harvesting and biomedical implanting. In this review, we present progress and recent achievements in the theory and computer simulations of the physicochemical properties of small TiO2 clusters, middle-size nanoparticles, as well as the liquid-solid interface. The historical overview and the development of empirical force fields for classical molecular dynamics (MD) of various TiO2 polymorphs, such as rutile, anatase, and brookite, are given. The adsorption behavior of solvent molecules, ions, small organic ligands, and biomacromolecules on TiO2 interfaces are examined with the aim of the understanding of driving forces and mechanisms, which govern binding and recognition between adsorbate and surfaces. The effects of crystal forms, crystallographic planes, surface defects, and solvent environments on the adsorption process are discussed. Structural details and dynamics of adsorption phenomena, occurring at liquid-solid interfaces, are overviewed starting from early empirical potential models up to recent reactive ReaxFF MD simulations, capable of capturing dissociative adsorption of water molecules. The performance of different theoretical methods, ranged from quantum mechanical (QM) calculations (ab initio and the density functional theory) up to classical force field and hybrid MM/QM simulations, is critically analyzed. In addition, the recent progress in computational chemistry of light-induced electronic processes, underlying the structure, dynamics, and functioning of molecular and hybrid materials is discussed with the focus on the solar energy applications in dye-sensitized solar cells (DSSC), which are currently under development. Besides, dye design principles, the role of anchoring moiety and dye aggregation in the DSSC performance are crucially analyzed. Finally, we outline the perspectives and challenges for further progress in research and promising directions in the development of accurate computational tools for modeling interactions between inorganic materials with not perfect structures and natural biomacromolecules at physiological conditions.