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[en] The list of authors and their affiliations should read:N. V. Roota, b, D. Yu. Kultina, L. M. Kustova, b, I. K. Kudryavtseva, and O. K. Lebedevaa,*aDepartment of Chemistry, Moscow State University, Moscow, 119991 RussiabN.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 119991 Russia*e-mail: email@example.com
[en] A polysiloxane with attached groups of rubeanic acid is proposed for the extraction of silver(I), platinum(IV) and palladium(II) from dilute aqueous systems. The sorbent is synthesized for the first time via modern sol–gel technology and has a high degree of surface modification; the concentration of the attached dithiooxamide groups is 0.90 mmol/g. Isotherms of the sorption of silver(I), platinum(IV), and palladium(II) from individual solutions are constructed. The curves are mathematically processed with the Langmuir, Freundlich, Redlich–Peterson, Langmuir–Freundlich, and Toth equations, so exchange capacity values are determined for the modified polysiloxane. The sorbent has good capacitive characteristics and can be used to accumulate large amounts of noble metal ions.
[en] The solubility of 2-chloro-3-(trifluoromethyl)pyridine (CTP) in ethyl acetate, n-butyl alcohol, 2‑propanol, methanol, trichloromethane, acetonitrile, and acetone under atmospheric pressure was measured at 273.15–303.15 K. The solubility of CTP in all eight solvents increased with the increase in temperature. The solubility of CTP had a relation with the polarity of the solvents. The modified Apelblat equation, λh equation, Wilson model, and NRTL model were used to correlate the solubility. The standard dissolution enthalpies were also evaluated.
[en] The results of a thermodynamic study of the Tl2Te–Tl2Te3–TlGdTe2 system by the electromotive force (EMF) method in the temperature range 300–450 K were presented. The partial thermodynamic functions of GdTe and Gd in alloys were first determined from the experimental EMF data for concentration cells relative to the GdTe electrode. The standard thermodynamic functions of formation and standard entropies of Tl9GdTe6 and TlGdTe2 were calculated based on these data.
[en] The aim of this study is to investigate the physicochemical behavior of some selected thiobarbituartes and explore their interaction with ds-DNA. To the best of our knowledge limited work has been reported on physicochemical investigation of these medicinal compounds and their interaction with ds-DNA. Therefore, this lack of information on the fundamental physicochemical studies of such medicinal compounds needs to be addressed. For this purpose five thiobarbiturate derivatives, denoted as: MKA 25, MKA26, MKA27, MKA28, MKA29, have been synthesized and characterized. Various physicochemical investigations of these thiobarbiturates are carried out. The thermal decomposition of these medicinal compounds was also studied by TGA technique. Further the mode of interaction and binding of these newly synthesized compounds with ds-DNA was carried by using UV–Vis spectrometry. It was seen from the overall results that the physicochemical properties as well as the extent of their interaction with biopolymer not only depend on the side alkyl groups but also on varying the functional groups of the samples.
[en] Cation-π and anion-π interactions were studied in the Na+-substituted-COT and F-substituted-COT complexes (where substituted-COT is planar cyclooctatetraene with four X‒C≡C-substituents (X = OH, CH3, H, F, and CN) using computational quantum chemistry methods. There are no direct electrostatic interactions of substituents with cations and anions in these complexes. The electron-donating and electron-withdrawing substituents lead to increase of the strength of cation-π and anion-π interactions, respectively. There are meaningful correlations between the Hammett constants and binding energies. The AIM analysis shows that the electron-donating and electron-withdrawing substituents lead to increase in electronic charge density values at ring critical points (RCPs) of the Na+-substituted-COT and F–-substituted-COT complexes, respectively (compared to complexes with X = H). NMR calculations demonstrate that the cation-π interactions are consistent with more antiaromatic rings and the anion-π ones are in accord with less antiaromatic rings.
[en] UV–Vis spectra of neutral and acidic solutions of C-methyl derivatives of dimethylaminoazobenzene are compared to the analogous spectra of dimethylaminoazobenzene (DAB), the main state of which is Rydberg dimers (rydimers) DAB2. The identical nature of the spectra of DAB and its 2-, 2′-, 3′-, 4′-methyl derivatives in neutral ethanol is established, testifying to the rydimer structure of these azo dyes and the identical nature of their chromogens, which have intense Vis bands at 400–430 nm. Uniform spectral changes are observed for solutions of 2-, 3′-, 4-methyl-substituted DAB and DAB2 during protonation at low acidities, demonstrating the stability of the respective rydimers and the identical protonation mechanism of their dimethylamino groups. UV bands at 320 nm and Vis bands at 500–530 nm are observed in the spectra of the resulting rydimers with ammonia groups. It is concluded that as acidity rises, these rydimers first attach a proton to the azo group, change into a triprotonated form, and then decompose with the formation of diprotonated monomers. At low acidity, rydimers with methyl groups at positions 2′ and 3 on phenylene rings are also protonated on amino groups but dissociate with the formation of the corresponding monomeric ammonium cations, the spectra of which copy the UV–Vis spectrum of azobenzene. Based on an analogy between the observed spectral characteristics and those known from the literature on a large number of azo dyes, it is concluded that the rydimer structure is a common property of azo dyes.
[en] The effect ethonium, a dicationic surfactant, has on the physicochemical properties of a natural flavonoid, rutin, is studied spectrophotometrically in a wide range of concentrations in the region of physiological pH. It is found there are a bathochromic shift of the bands in the absorption spectra of rutin, a drop in the apparent constant of its dissociation , and an increase in solubility and adsorption on the surface of nanosilica relative to aqueous solutions. The constant of bonding between rutin and ethonium is calculated.
[en] Concentration dependences of the surface tension and density of solutions of three-component acetone–ethanol–water systems and the bounding binary systems at 273 K are studied. The molar volume, adsorption, and composition of surface layers are calculated. Experimental data and calculations show that three-component solutions are close to ideal ones. The surface tensions of these solutions are calculated using semi-empirical and theoretical equations. Theoretical equations qualitatively convey the concentration dependence of surface tension. A semi-empirical method based on the Köhler equation allows us to predict the concentration dependence of surface tension within the experimental error.