Valentina V. Sobornova

The interaction between carbon dioxide and molecularly confined pharmaceutical compounds can result in CO₂ retention that exceeds that achieved through conventional physical adsorption. This study investigates CO₂ retention following sorption in hydrophilic and hydrophobic silica aerogels containing the fenamates mefenamic acid and flufenamic acid. The Thermal stability of the retained CO₂ was characterized using temperature-programmed oxidation and temperature-programmed desorption measurements. Concurrently, single-point nitrogen adsorption measurements monitored relative changes in the apparent accessible surface area of the porous matrix. Untreated silica aerogels did not exhibit a significant CO₂ desorption peak at elevated temperatures. In contrast, all composites containing fenamates exhibited an additional high-temperature desorption step beginning at approximately 225 °C, indicating enhanced CO₂ retention after sorption once the external CO₂ layer was removed. This characteristic persisted following preliminary thermal treatment, suggesting it is not solely attributable to residual volatile substances. Surface-area measurements indicated minimal changes in the original aerogels after the CO₂ cycle, whereas composites with flufenamic acid demonstrated more pronounced alterations. Considering previous nuclear magnetic resonance, spectroscopic, and computational studies, these findings suggest a combined effect of nanoconfinement, surface-dependent interfacial phenomena, and specific interactions involving the fenamate-containing phase. Reversible chemical interactions may contribute to the observed retention, although the current measurements do not allow for quantitative separation of their effects from those of physical confinement.

The study presents a thorough and detailed analysis of bicalutamide’s structural and conformational properties. Quantum chemical calculations were employed to explore the conformational properties of the molecule, identifying significant energy differences between conformers. Analysis revealed that hydrogen bonds stabilise the conformers, with notable variations in torsion angles. Conformers were classified into ‘closed’ and ‘open’ types based on the relative orientation of the cyclic fragments. NOE spectroscopy in different solvents (CDCl₃ and DMSO-d₆) was used to study the conformational preferences of the molecule. NOESY experiments provided the predominance of ‘closed’ conformers in non-polar solvents and a significant presence of ‘open’ conformers in polar solvents. The proportions of open conformers were 22.7 ± 3.7% in CDCl₃ and 59.8 ± 6.2% in DMSO-d₆, while closed conformers accounted for 77.3 ± 3.7% and 40.2 ± 6.2%, respectively. This comprehensive study underscores the solvent environment’s impact on its structural behaviour. The findings significantly contribute to a deeper understanding of conformational dynamics, stimulating further exploration in drug development.

The possibilities of nuclear Overhauser effect spectroscopy (NOESY) for conformational analysis of fenamate (e.g., flufenamic acid) molecules were shown. It was established that the proportions of conformer groups changed by up to 32% on passing from a system with pure DMSO to a solvent based on SC-CO₂ with a 2 mol % DMSO addition. The results showed that the conformational equilibrium of small drug-like molecules can be controlled using supercritical fluids for slightly soluble compounds. This is promising for the micronization of fenamates by the RESS, SAS, and DELOS methods.

1,5-Diaryl-3-Oxo-1,4-Pentadiene derivatives are intriguing organic compounds with a unique structure featuring a pentadiene core, aryl groups, and a ketone group. This study investigates the influence of fluorine atoms on the conformational features of these derivatives in deuterated chloroform (CDCl₃) solution. Through nuclear magnetic resonance (NMR) spectroscopy and quantum chemical calculations, we discerned variations in interatomic distances and established predominant conformer proportions. The findings suggest that the non-fluorinated entity exhibits a uniform distribution across various conformer groups. The introduction of a fluorine atom induces substantial alterations, resulting in the predominance of a specific conformer group. This structural insight may hold the key to their diverse anticancer activities, previously reported in the literature.

This study examines the influence of mefenamic acid on the physical and chemical properties of silica aerogels, as well as its effect on the sorption characteristics of the composite material. Solid state magic angle spinning nuclear magnetic resonance (MAS NMR) and high-pressure ¹³C NMR kinetic studies were conducted to identify the presence of mefenamic acid and measure the kinetic rates of CO₂ sorption. Additionally, a high-pressure T₁–T₂ relaxation-relaxation correlation spectroscopy (RRCOSY) study was conducted to estimate the relative amount of mefenamic acid in the aerogel’s pores, and a high-pressure nuclear Overhauser effect spectoscopy (NOESY) study was conducted to investigate the conformational preference of mefenamic acid released from the aerogel. The results indicate that mefenamic acid is affected by the chemical environment of the aerogel, altering the ratio of mefenamic acid conformers from 75% to 25% in its absence to 22% to 78% in the presence of aerogel.

The study of supercritical carbon dioxide sorption processes is an important and urgent task in the field of “green” chemistry and for the selection of conditions for new polymer material formation. However, at the moment, the research of these processes is very limited, and it is necessary to select the methodology for each polymer material separately. In this paper, the principal possibility to study the powder sorption processes using ¹³C nuclear magnetic resonance spectroscopy, relaxation-relaxation correlation spectroscopy and molecular dynamic modeling methods will be demonstrated based on the example of polymethylmethacrylate and supercritical carbon dioxide. It was found that in the first nanoseconds and seconds during the sorption process, most of the carbon dioxide, about 75%, is sorbed into polymethylmethacrylate, while on the clock scale the remaining 25% is sorbed. The methodology presented in this paper makes it possible to select optimal conditions for technological processes associated with the production of new polymer materials based on supercritical fluids.