Russian Chemical Bulletin最新文献

The binding energies of thioligands L of the general formula S=CR₁R₂ in dinitrosyl iron complexes [Fe(NO)₂L₂]⁺ (DNICs) were calculated using density functional theory methods. The TPSSH functional with the def2-TZVP basis set and the PCM–SMD polarizable continuum model were used. The reactions of abstraction of 14 thioamide and thiocarbonyl ligands and their replacement with a H₂O molecule in the gas phase and aqueous medium were studied. It is found that the bond energies in the gas phase do not accurately characterize the stability of DNICs because of the high energy of reorganization of the reaction products upon their transition into the aqueous phase. Analysis of the structure—activity correlations revealed linear regression dependences of Fe—S bond energies on partial charges on S atoms and electronegativity of thioligands.

The three-dimensional Ni redox-active metal-organic framework [Ni(bpy)(fcdHp)] based on nickel(ii) cations, anions of ferrocenylbis(H-phosphinic) acid (H₂fcdHp), and 4,4′-bipyridine (bpy) was first tested as an oxygen reduction reaction (ORR) catalyst. This compound showed remarkable efficiency and good stability under electrochemical conditions. The diagnostic performance in a proton-exchange membrane fuel cell with this catalyst on the cathode side of the membrane-electrode assembly (MEA) was evaluated for the first time. The catalytic ability of the new system as an ORR catalyst without a platinum catalyst on the anode side was confirmed in a half-cell setup, in which the cathode compartment of the MEA and the anode (liquid electrochemical cell) are separated by a polyelectrolyte membrane.

The effect of post-polymerization for photopolymerizable composition based on oligoester methacrylate OCM-2 was studied using IR spectroscopy. Numerical simulation of this process was carried out within the framework of a kinetic model that takes into account changes in the concentration of both the monomer and radicals of growth. It was demonstrated that the increase in conversion due to the post-polymerization depends on the concentration and lifetime of radicals, as well as the ratio of the light pulses length to the repetition period. The influence of post-polymerization on the exposure characteristics of the polymerization process is considered for the cases of exposure to single radiation pulses (scanning lithography) and photoiniation by a periodic sequence of light pulses (using pulse-width modulation of semiconductor light sources).

The photophysical behavior of new type of bimetallic ruthenium complexes based on crown- and phenanthroline-containing ligands was evaluated. Ruthenium(ii) in the explored complexes was coordinated to the 1,10-phenanthroline moiety and caused a noticeable effect on the optical properties of the complex. The second cation was introduced into the macrocyclic cavity in such a way that its presence significantly enhances phosphorescence. It was demonstrated for the monoruthenium crown-containing complex bis(2,2-bipyridine-k4N1′,N1″)[2-(2-(2,3,5,6,8,9,11,12,14,15,16a,20a-dodecahydrobenzo[b][1,4,10,13,7,16]-tetraoxadithiacyclooctadecyn-18-yl)-1H-imidazo[4,5-f][1,10]phenanthroline-k2N7,N8]-ruthenium(ii) chloride that its exposure to visible light led to two different excitation pathways. Only one of them led to the excited state ³MLCT (metal-to-ligand charge transfer) responsible for its phosphorescence. The second excited state of ¹LLCT (ligand-to-ligand charge transfer) nature “withdraws” the excitation energy from the emitting state ³MLCT, thus reducing the quantum yield. The introduction of the second cation into the crown ether moiety significantly affected the electron density distribution; in particular, it hindered the transfer of electrons within the ligand common to the two cations. As a result, long-wave irradiation induced only the MLCT transition, which significantly increased the probability of radiative relaxation.

Methods were developed for the synthesis of hybrid products responsive to both UV irradiation and magnetic stimuli. 2-Furyl-3-acylchromones containing paramagnetic groups (piperidine-N-oxyl and 2-imidazoline-3-oxide-1-oxyl) in the acyl and furanyl moieties of the molecules were prepared. The molecular and crystal structure of the paramagnetic derivative containing the 2-imidazoline-3-oxide-1-oxyl substituent was determined by X-ray diffraction. Short intermolecular contacts between the oxygen and C(2) atoms of the nitronyl nitroxide moieties, at which the spin density of opposite signs is accumulated, were revealed. It was demonstrated that UV irradiation of chromone, containing a paramagnetic moiety isolated from the conjugated benzopyran system, leads to its rearrangement giving a fluorescent product.

Evaporation processes and thermodynamic properties were for the first time investigated using the Knudsen effusion mass spectrometric method for ceramics based on the Cs₂O—Al₂O₃—SiO₂ system within the temperature range of 1000–1200 K. The found values of partial pressures of vapor species, activities of components, and Gibbs energy indicated negative deviations of the thermodynamic properties from the model of ideal solution. The obtained experimental values of thermodynamic properties were optimized using the generalized lattice theory of the associated solutions.

A simple method for modifying sesquiterpene lactones with 3,5-bis(arylidene)piperi-din-4-ones using the phase-transfer catalytic aza-Michael addition in the MeCN—K₂CO₃ system was developed. Molecular docking revealed that the synthesized conjugates of isoalantolactone, alantolactone, and dehydrocostus lactone with various bis(arylidene)-piperidones directly interact with the DNA binding site of the p50 subunit of nuclear factor κB, which may be indicative of their ability to induce apoptotic death of the tumor cells due to activation of the death receptor expression and, thereby, to exhibit an antitumor effect.

The present review is devoted to oxaloacetic esters widely used in the synthesis of heterocyclic compounds and malonic ester derivatives. Three carbonyl groups of oxaloacetic esters have different reactivity allowing the tuning of overall reactivity of these compounds. The synthetic approaches to oxaloacetic esters, in particular the condensation of oxalates and acetates as well as the modern innovations in this classical synthesis that involved alkyl oxalyl chlorides, are reviewed. The main strategies for modification of oxaloacetic esters, e.g., halogenation and arylation, as well as the possibilities to overcome the side reactions are considered in detail. Special attention is paid to transformations of hydroxysuccinic esters and their oxidation to oxaloacetic esters. The reactions of acetylenedicarboxylic esters with carbonyl compounds, N- and S-oxides, and nitrones are also considered. The mechanisms of the rearrangement of the adducts of acetylenedicarboxylic ethers with heteroaromatic N-oxides are thoroughly discussed.

The review is devoted to the main synthetic strategies and optimal methods for preparation of persistent clathrochelate-centered radicals, the macrobicyclic products of free-radical reactions of the clathrochelate precursors. Prospects for practical applications of this type of compounds as radical polymerization initiators and paramagnetic probes for MRI and EPR studies are analyzed.

New iron(ii) complexes with 2,6-bis(1H-imidazol-2-yl)-4-methoxypyridine (L), viz., [FeL₂]Cl₂•2H₂O (1•2H₂O), [FeL₂](NO₃)₂•H₂O (2•H₂O), [FeL₂](ClO₄)₂•0.5H₂O (3•0.5H₂O), and [FeL₂]I₂•C₃H₆O (4•C₃H₆O) were synthesized and studied. Conclusions about the structure of the compounds are based on the diffuse reflectance, IR, and Mössbauer spectroscopy data and on the results of static magnetic susceptibility measurements and quantum chemical calculations. The temperature dependences of the effective magnetic moments of the compounds synthesized, except 1•2H₂O and 1, demonstrated features associated with spin crossover accompanied by thermochromism (changes of the color from orange to red-violet). The cytotoxic and cytostatic activity studies of the compounds in question revealed a cytostatic effect on the human hepatocellular carcinoma HepG2 cells characterized by 50% inhibitory concentration (IC₅₀) values from 44.7 ± 0.4 to 58.8 ± 0.6 µmol L⁻¹.