Russian Journal of Physical Chemistry A最新文献

In this study, we conducted a comprehensive spectral analysis of the spatial structure of the anticancer drug compound bicalutamide, marketed under the trade name Casodex®, using a combination of one- and two-dimensional NMR spectroscopy methods in a deuterated dimethyl sulfoxide environment. The data from selective nuclear Overhauser effect experiments and quantum chemical calculations, performed within the framework of density functional theory, allowed us to quantitatively assess the conformer group fractions of the compound in deuterated dimethyl sulfoxide.

A way of processing thermochemical measurements is analyzed in respect to determining the enthalpies of combustion and the formation of ionic liquids (ILs). It is shown that the error in the difference between the heat of combustion of an IL in a polyethylene ampoule and that of polyethylene is ignored, and the error in the difference between the sum of the enthalpies of the formation of combustion products and the combustion of the IL is not considered when calculating the enthalpies of formation. It is proposed that the linear dependence of the heat of combustion on the mass of a sample passing through the origin of coordinates be used to increase the accuracy of calculating an IL’s heat of combustion. The heats of combustion of polyethylene ampoules and three ionic liquids are measured: trihexyltetradecylphosphonium bromide ([P₆₆₆₁₄]Br), butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N₄₁₁₁][NTf₂]), and 1-butyl-4-methylpyridinium tetrafluoroborate ([BMPy][BF₄]). A linear dependence of the heat of combustion on the mass of a sample is established and used to determine the standard enthalpies of combustion of the studied ILs. It is shown that the error in determining an IL’s heat of combustion grows as the mass of a sample shrinks, and the specific heat of combustion falls due to a reduction in the difference between the specific heats of combustion in a polyethylene ampoule and the ampoule itself.

The attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) spectra of the samples of polybutylene terephthalate (PBT) with varying spatial densities of cross-links are obtained. The changes are primarily observed in the fingerprint region. The ratios of the area of the absorption bands 810/794 and 917/935 cm^–1 bands are shown to decrease with increasing degree of cross-linking and can be used to assess it. The changes in infrared absorption are linked to the difference in the bending frequency between the crystalline and amorphous phases of PBT. The latter is more prevalent in the densely cross-linked samples.

Native, modified, and polymeric cyclodextrins are used for the first time to improve the solubility and bioavailability of synthetic immunomodulator fingolimod (FTY720). It is shown that the solubility of FTY720 grows in the presence of cyclodextrins. Constants of the stability of guest–host complexes and the index of efficiency of the solubilizing action of cyclodextrins are calculated from experimentally obtained phase solubility diagrams of FTY720. The effect the structure of cyclodextrin on the solubilization of FTY720 is considered.

Results are presented from developing a model for accurately predicting the wavelength of the absorption maximum of boron(III) dipyrromethenates (BODIPYs). The model is based on a graph neural network (GNN) and includes data for >2500 dyes of various natures. Statistical parameters of the model (MAE and R²) are 4 nm and 0.99 for the training set and 13.5 nm and 0.87 for the testing set. The developed model is available to the public in the GitHub repository (https://github.com/lukanov-9b/Abs_model.git).

Copper antimonides and phases based on them are of great interest as environmentally friendly functional materials for potential application in various areas of industry and technology. Present work demonstrates the results of thermodynamic study of Cu₄Sb and two polymorphic modifications of Cu₂Sb by low temperature electromotive force method (EMF) with a Cu⁺ conducting solid electrolyte RbCu₄Cl₃I₂ in 300–480 K temperatures range. Measurements were performed using equilibrium samples from the Cu₂Sb + Sb and Cu₄Sb + Cu₂Sb phase regions of the system. Phase compositions of samples were controlled using the powder X-ray diffraction (PXRD) method. Partial molar thermodynamic functions of copper in alloys, as well as, thermodynamic functions of formation and the absolute entropies of the RT–Cu₂Sb, HT–Cu₂Sb, and Cu₄Sb compounds were calculated. The enthalpy and entropy of the polymorph transition of Cu₂Sb were calculated based on the EMF data. A comparative analysis of obtained results with literature data was performed.

Liquid interfaces are modeled for n-alkane + water systems with an without added non-ionic surfactants: polyethylene glycol ethers of fatty alcohols (C_nE_m). Coarse-grained molecular dynamic (MD) simulation with the MARTINI force field is combined with a coarse-grained version of a multilayer quasi-chemical model (MQM) of a non-uniform fluid mixture. The effect the choice of the monomer’s unit size has on predicting the interfacial tension and mutual solubility of n-alkanes and water is demonstrated using the MQM. The interfacial tension’s dependence on the length of the n-alkane chain and the structure of the added surfactant molecule are predicted satisfactorily. A predicted drop in the interfacial tension upon adsorption of the surfactant is consistent with the MD data. Liquid-liquid phase diagrams are calculated, and the non-uniform of the surfactant between the hydrocarbon and aqueous phases is described, depending on the ratio of the hydrophobic and hydrophilic parts of the C_nE_m molecule. The coarse-grained MQM is used to obtain normal and tangental pressure profiles and data on the local structure for flat and spherical phase boundaries. A conclusion is reached on the limited applicability of the coarse-grained approach within the MQM.

Precision adiabatic vacuum and high-precision differential scanning calorimetry (DSC) are used to study the temperature dependence of the heat capacity of betamethasone dipropionate in the range of 6–520 K for the first time. A phase transition of betamethasone dipropionate (melting) is detected in the above range of temperatures, and its thermodynamic characteristics are calculated. The low temperature heat capacity (20 ≤ T ≤ 50 K) is processed on the basis of a multifractal model, and the chain-layered topology of the structure is established. The thermal stability of the steroid hormone is studied via thermogravimetric analysis (TGA). It is found that the temperature at which the substance begins to decompose is 480 K. The experimental data are used to calculate standard thermodynamic functions in the region T → 0 to 480 K for the crystalline and liquid states of betamethasone dipropionate.

The author proposes and describes a way of estimating the magnitude of the thermodynamic barrier to the formation of a critical-sized crystalline nucleus. The frequency of the formation of such nuclei that are stable and capable of further growth determines the rate of nucleation. For nucleation to occur, the nucleus must overcome the thermodynamic barrier. The measure of the magnitude of this barrier is the work needed to create the surface of a nucleus W*, determined from the values of surface energy σ and size r* of the critical nucleus for different temperatures of the preliminary heat treatment of glasses and their subsequent manifestation (crystal growth). The values of σ and r* are obtained from experimentally determined rates I_st of steady-state crystal nucleation; periods τ of non-stationary crystal nucleation, the measure of which is time t_ind of the induction period; and difference Δφ between the specific free energies of the glass and crystal. Values of W* are obtained for a series of silicate glass compositions for promoting crystal nucleation in these glasses.

Experimental studies of density and viscosity of gallium-rare-earth metal composition alloys with light lanthanides (neodymium and samarium) are investigated for the first time. It is established that these compositions are characterized by long-term non-monotonic changes of properties (relaxation processes) in liquid state. The coefficients of temperature expansion of Ga₉₅Nd₅ and Ga₉₇Sm₃ alloys and activation energy of viscous flows of their melts are calculated based on experimental data.