Dispersion Interactions Research Articles

Attraction between Like Charged Ions in Ionic Liquids: Unveiling the Enigma of Tetracyanoborate Anions.

Intermolecular interactions in ionic liquids are mainly governed by Coulombic forces. Attraction between cations has been previously observed and was attributed to dispersion interactions between nonpolar moieties, hydrogen bonding, or π stacking. In this study, we present the intriguing behavior of tetracyanoborate anions in ionic liquids that, unlike their dicyanamide and tricyanomethanide counterparts, form dimers in both solid and liquid phases. A joint simulation and experimental study uncovers the origin of such anion-anion attraction: stabilization by induction and dispersion forces between several cyano groups, which is strong enough to overcome electrostatic repulsion. These findings open up new opportunities in the rational design of ionic liquids, where interactions between ions of the same charge can be controlled and fine-tuned by the presence of cyano groups.

A synthetic approach towards drug modification: 2-hydroxy-1-naphthaldehyde based imine-zwitterion preparation, single-crystal study, Hirshfeld surface analysis, and computational investigation.

The current work is about the modification of primary amine functionalized drugs, pyrimethamine and 4-amino-N-(2,3-dihydrothiazol-2-yl)benzenesulfonamide, via condensation reaction with 2-hydroxy-1-naphthaldehyde to produce new organic zwitterionic compounds (E)-1-(((4-(N-(2,3-dihydrothiazol-2-yl)sulfamoyl)phenyl)iminio)methyl)naphthalen-2-olate (DSPIN) and (E)-1-(((4-amino-5-(4-chlorophenyl)-6-ethylpyrimidin-2-yl)iminio)methyl)naphthalen-2-olate (ACPIN) in methanol as a solvent. The crystal structures of both compounds were confirmed to be imine-based zwitterionic products via single-crystal X-ray diffraction (SC-XRD) analysis which indicated that the stabilization of both crystalline compounds is achieved via various noncovalent interactions. The supramolecular assembly in terms of noncovalent interactions was explored by the Hirshfeld surface analysis. Void analysis was carried out to predict the crystal mechanical response. Compound geometries calculated in the DFT (Density Functional Theory) study showed reasonably good agreement with the experimentally determined structural parameters. Frontier molecular orbital (FMO) analysis showed that the DSPIN HOMO/LUMO gap is by 0.15 eV smaller than the ACPIN HOMO/LUMO gap due to some destabilization of the DSPIN HOMO and some stabilization of its LUMO. The results of the charge analysis implied formation of intramolecular hydrogen bonds and suggested formation of intermolecular hydrogen bonding and dipole-dipole and dispersion interactions.

Exploration of carvacrol aggregation by laser spectroscopy.

Carvacrol is an aromatic monoterpenoid found in thyme oil. Due to its implications for human health, it is important to elucidate its structure and its intramolecular interactions. We have characterised the carvacrol monomer, its complex with water, its dimer, and even its trimer in a supersonic expansion using mass-resolved laser spectroscopy techniques complemented by quantum-chemical computations. The resonance-enhanced multiphoton ionisation spectrum of the monomer features several transitions, which were assigned to the same conformer, confirmed by ion-dip infrared spectroscopy. However, a conclusive assignment of the infrared bands to one of the four conformations of carvacrol remains elusive. The experimental spectra for the monohydrated, the homodimer, and the homotrimer point to the detection of the lowest energy isomer in each case. Their structures are governed by a balance of intramolecular interactions, specifically hydrogen bonding and dispersion forces. Comparison with other similar systems demonstrates that dispersion interactions are key to the stabilisation of the aggregates, being present in all the structures. However, the hydrogen bonding is the dominant force as observed in the lowest-energy conformations.

Interactions of phosphate, phosphine oxide and phosphoramide ligands with Th(IV)

The complexation behavior of phosphate, phosphine oxide, and phosphoramide ligands with Th(IV) is investigated at the Density Functional Theory (DFT) level. Employing Energy Decomposition Analysis (EDA), the study reveals significant contributions of geometric strain and dispersion interactions in determining the stability of these complexes. It is observed that the orbital interaction in the various Th(IV) complexes increases in the order phosphate < phosphine oxide < phosphoramide.

A many-body energy decomposition analysis (MB-EDA) scheme based on a target state optimization self-consistent field (TSO-SCF) method.

In this paper, we combine an energy decomposition analysis (EDA) scheme with many-body expansion (MBE) to develop a MB-EDA method to study the cooperative and anti-cooperative effects in molecular cluster systems. Based on the target state optimization self-consistent field (TSO-SCF) method, the intermolecular interaction energy can be decomposed into five chemically meaningful terms, i.e., electrostatic, exchange, polarization, charge transfer and dispersion interaction energies. MB-EDA can decompose each of these terms in MBE. This MB-EDA has been applied to 3 different cluster systems: water clusters, ionic liquid clusters, and acetonitrile-methane clusters. This reveals that electrostatic, exchange, and dispersion interactions are highly pairwise additive in all systems. In water and ionic liquid clusters, the many-body effects are significant in both polarization and charge transfer interactions, but are cooperative and anti-cooperative, respectively. For acetonitrile-methane clusters, which do not involve hydrogen bonds or charge-charge Coulombic interactions, the many-body effects are quite small. The chemical origins of different many-body effects are deeply analyzed. The MB-EDA method has been implemented in Qbics (https://qbics.info) and can be a useful tool for understanding the many-body behavior in molecular aggregates at the quantum chemical level of theory.

Dispersion interaction between thin conducting cylinders.

The ground state and excited state resonance dipole-dipole interaction energy between two elongated conducting molecules is explored in this study. We review the current status for ground state interactions. This interaction is found to be of a much longer range than in the case when the molecules are pointlike and nonconducting. These are well known results found earlier by Davies, Ninham, and Richmond, and later, using a different formalism, by Rubio and co-workers. We show how the theory can be extended to excited state interactions. A characteristic property observed from our calculation is that the interaction energy dependence on separation (R) follows f(R)/R2 for both resonance and van der Waals cases in the long-range limit. Under some limits, f(R) has a logarithmic dependency, while under others, it has constant values. We predict an unusual slow decay rate for the energy transfer between conducting molecules.

Analysing the stability of He-filled hydrates: how many He atoms fit in the sII crystal?

Clathrate hydrates have the ability to encapsulate atoms and molecules within their cavities, and thus they could be potentially large storage capacity materials. The present work studies the multiple cage occupancy effects in the recently discovered He@sII crystal. On the basis of previous theoretical and experimental findings, the stability of He(1/1)@sII, He(1/4)@sII and He(2/4)@sII crystals was analysed in terms of structural, mechanical and energetic properties. For this purpose, first-principles DFT/DFT-D computations were performed by using both semi-local and non-local functionals, not only to elucidate which configuration is the most energetically favoured, but also to scrutinize the relevance of the long-range dispersion interactions in these kinds of compounds. We have encountered that dispersion interactions play a fundamental role in describing the underlying interactions, and different tendencies were observed depending on the choice of the functional. We found that PW86PBE-XDM shows the best performance, while the non-local functionals tested here were not able to correctly account for them. The present results reveal that the most stable configuration is the one presenting singly occupied D cages and tetrahedrally occupied H cages (He(1/4)@sII) in line with the experimental observation.

Binary conformers of a flexible, long-chain fluoroalcohol: dispersion controlled selectivity and relative abundances in a jet.

The complex conformational panorama of binary 4,4,4-trifluoro-1-butanol (TFB) aggregates was investigated using chirped-pulse Fourier transform microwave spectroscopy, aided by conformational searches using CREST (Conformer-Rotamer Ensemble Sampling Tool) and quantum chemistry calculations. From nearly 1500 initial dimer geometries, 16 most stable binary candidates were obtained within a relative energy window of ∼4 kJ mol-1. Rotational spectra of five binary conformers were experimentally observed in supersonic expansion and assigned. Interestingly, three out of the five observed binary conformers are composed solely of monomer conformers, which were not observed in their isolated gas phase forms in jet expansion. In addition, an observed dimer that is made exclusively of the most stable TFB monomer subunits does not correspond to the global minimum. The intricate kinetically and thermodynamically controlled dimer formation mechanisms are discussed, and a modified kinetic-thermodynamic model was developed, providing conformational abundances that are in good agreement with the experiment. Subsequent non-covalent interaction analyses reveal that the observed conformers are held together by one primary O-H⋯O hydrogen bond and secondary intermolecular C-H⋯O, C-H⋯F, and/or O-H⋯F interactions, as well as C-H⋯H-C London dispersion interactions between the methylene groups. Further symmetry-adapted perturbation theory analyses of the TFB dimer conformers and related alcohol dimers reveal a considerable rise in dispersion contributions with increasing n-alkyl carbon chain length and highlight the role of dispersion interactions in preferentially stabilizing the global minimum of the TFB dimer.

Extended siponimod release via low-porosity PLGA fibres: a comprehensive three-month in vitro evaluation for neovascular ocular diseases.

Neovascular ocular diseases are among the most common causes of preventable or treatable vision loss. Their management involves lifelong, intravitreal injections of anti-vascular endothelial growth factor (VEGF) therapeutics to inhibit neovascularization, the key pathological step in these diseases. Anti-VEGF products approved for ocular administration are expensive biological agents with limited stability and short half-life. Additionally, their therapeutic advantages are hindered by high treatment resistance, poor patient compliance and the need for frequent, invasive administration. Herein, we used electrospinning to develop a unique, non-porous, PLGA implant for the ocular delivery of siponimod to improve ocular neovascular disease management. Siponimod is an FDA-approved drug for multiple sclerosis with a novel indication as a potential ocular angiogenesis inhibitor. The electrospinning conditions were optimised to produce a microfibrous, PLGA matte that was cut and rolled into the desired implant size. Physical characterisation techniques (Raman, PXRD, DSC and FTIR) indicated siponimod was distributed uniformly within the electrospun fibres as a stabilised, amorphous, solid dispersion with a character modifying drug-polymer interaction. Siponimod dispersion and drug-polymer interactions contributed to the formation of smooth fibres, with reduced porous structures. The apparent reduced porosity, coupled with the drug's hydrophobic dispersion, afforded resistance to water penetration. This led to a slow, controlled, Higuchi-type drug diffusion, with ∼30% of the siponimod load released over 90 days. The released drug inhibited human retinal microvascular endothelial cell migration and did not affect the cells' metabolic activity at different time points. The electrospun implant was physically stable after incubation under stress conditions for three months. This novel siponimod intravitreal implant broadens the therapeutic possibilities for neovascular ocular diseases, representing a potential alternative to biological, anti-VEGF treatments due to lower financial and stability burdens. Additionally, siponimod interaction with PLGA provides a unique opportunity to sustain the drug release from the electrospun fibres, thereby reducing the frequency of intravitreal injection and improving patient adherence.

Deciphering the shape selective conformational equilibrium of E- and Z-locked azobenzene-tetraethylammonium ion in regulating photo-switchable K+-ion channel blocking.

The search for photo-switchable optopharmacological agents that can block ion channels has been a prevalent area owing to its prime advantages of reversibility and specificity over the traditional blockers. However, the quest for a higher blocking ability shown by a less stable photo-isomer to perfectly suit the requirement of the optopharmacological agents is still ongoing. To date, only a marginal improvement in terms of blocking ability is observed by the less stable E-isomer of para-substituted locked azobenzene with TEA (LAB-TEA) for the K+-ion channel. Thus, rationalization of the limitation for achieving high activity by the E-isomer is rather essential to aid the improvement of the efficiency of photoswitchable blocker drugs. Herein, we report a molecular-level analysis on the mechanism of blocking by E- and Z-LAB-TEA with the bacterial KcsA K+-ion channel using Molecular Dynamics (MD) simulation and Quantum Mechanical (QM) calculations. The positively charged TEA fragment engages in stronger electrostatic interactions, while the neutral LAB fragment engages in weaker dispersive interactions. The binding free energy calculated by Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) for E-LAB-TEA (-22.3 kcal mol-1) shows less thermodynamic preference for binding with K+-ion channels than Z-LAB-TEA (-21.6 kcal mol-1) corroborating the experimental observation. The correlation between the structure and the binding ability of E- and Z-isomers of LAB-TEA indicates that the channel gate is narrow and acts as a bottleneck for the entry of the binder molecule inside the large cavity. Upon irradiation, the Z-isomer converts into a less stable but long and planar E-isomer (ΔE of photoisomerism = 7.0 kcal mol-1, at SA2-CASPT2(6,4)/6-31+G(d)//CASSCF(6,4)/6-31+G(d)), which is structurally more suitable to fit into the narrow channel gate rather than the curved and non-planar Z-LAB-TEA. Thus, a reduction in the ionic current is observed owing to the preferential entry and subsequent blocking by E-LAB-TEA. Discontinuing the irradiation leads to conversion to the Z-isomer, the curved nature of which hinders its spontaneous release outside the cavity, thereby contributing only a small increase in the ionic current.

Mechanistic studies of HF/BF3-catalyzed anthracene polymerization to prepare mesophase pitch.

The mesophase pitch prepared by acid catalytic method typically had the advantages of low softening point and high solubility. To fully understand the mechanism of acid-catalyzed reactions and gain a deeper understanding of the microstructure of mesophase pitch, this article studied the mechanism of hydrofluoride/boron trifluoride (HF/BF3)-catalyzed anthracene using molecular simulation methods. The results showed that there might be two types of carbocations present in the system: classical and non-classical carbocations, and five reactions might occur, protonation reaction, chain elongation reaction, intramolecular cyclization reaction, deprotonation reaction, and dehydrogenation reaction. Classical carbocations acted as reactive intermediates in the chain elongation reaction and intramolecular cyclization reaction. When anthracene occurred chain elongation reactions with carbocations to form polymers, the generation of the tetramer required lager energy barriers than that of the dimer and trimer. The stiffness and flatness of molecules could be increased via intramolecular cyclization reactions. The polymers of anthracene might also occurred dehydrogenation reactions when the non-classical carbocations played the role of reactive intermediates. The dehydrogenation reactions required large energy barriers, which might be the reason for the product having a high aliphatic hydrogen content. The Materials Studio (MS) 2020 software was used to complete the simulation. The atomic charge distribution calculation and the structure optimization of molecules were carried out using the B3LYP functional and DNP basis. The DFT-D (TS) dispersion corrections were added to calculate the dispersion interaction between aromatic molecules. The complete LST/QST method was used to search the transition states and calculate the reaction energy barrier.

Mechanistic docking in terpene synthases using EnzyDock.

Terpene Synthases (TPS) catalyze the formation of multicyclic, complex terpenes and terpenoids from linear substrates. Molecular docking is an important research tool that can further our understanding of TPS multistep mechanisms and guide enzyme design. Standard docking programs are not well suited to tackle the unique challenges of TPS, like the many chemical steps which form multiple stereo-centers, the weak dispersion interactions between the isoprenoid chain and the hydrophobic region of the active site, description of carbocation intermediates, and finding mechanistically meaningful sets of docked poses. To address these and other unique challenges, we developed the multistate, multiscale docking program EnzyDock and used it to study many TPS and other enzymes. In this review we discuss the unique challenges of TPS, the special features of EnzyDock developed to address these challenges and demonstrate its successful use in ongoing research on the bacterial TPS CotB2.

A density functional theory study on interactions in water-bridged dimeric complexes of lignin.

Lignin is the main plant cell wall component responsible for recalcitrance in the process of lignocellulosic biomass conversion into biofuels. The recalcitrance and insolubility of lignin in different reaction media are due in part to the hydrogen bonds and π interactions that hold syringyl (S) and guaiacyl (G) units together and promote the formation of stable water-bridged dimeric complexes (WBDCs): S⋯G and S⋯S, in native lignin. The current understanding of how each type of interaction influences the stability of these complexes within lignin native cell walls is still limited. Here, we found by DFT calculations that hydrogen bonding is more dominant than π-stacking interaction between aromatic rings of WBDCs. Although there is a stronger interaction of hydrogen bonds between subunits and water and higher π-stacking interaction in the S⋯S complex compared to the S⋯G complex, the former complex is less thermodynamically stable than the latter due to the entropic contribution coming from the methoxy substituents in the S-unit. Our results demonstrate that the methoxylation degree of lignin units does not significantly influence the structural geometries of WBDCs; if anything, an enhanced dispersion interaction between ring aromatics results in quasi-sandwich geometries as found in "coiled" lignin structures in the xylem tissue of wood. In the same way as that with ionic liquids, polar solvents can dissolve S-lignin by favorable interactions with the aliphatic hydroxyl group in the α-position as the key site or the aromatic hydroxyl group as the secondary site.

Mechanism of cationic ring-opening polymerisation of ε-caprolactone using metallocene/borate catalytic systems: a DFT and NCI study on chain initiation, propagation and termination.

We present a comprehensive DFT investigation on the cationic ring-opening polymerisation (CROP) of ε-caprolactone (CL) using zirconocene/borate catalyst systems. All possible pathways of the interaction between cationic species [Cp2ZrMe+] and counteranions, [A-] = [MeB(C6F5)3]- and [B(C6F5)4]-, were examined during chain initiation, propagation, and termination steps. The calculations reveal an active chain-end mechanism with O-alkyl bond cleavage of the polymerisation. The catalytic performance of the two counteranions is found to be identical, and they influence the initial process through stabilisation of the cationic species via non-covalent interactions (NCI), with the [MeB(C6F5)3]- anion stabilising the catalyst-monomer complex more effectively than the [B(C6F5)4]- anion by 24.3 kJ mol-1. The first two propagations are likely the rate-determining step, with calculated free-energy barriers of 61.4-71.2 and 73.9-80.6 kJ mol-1 with and without the anions (A-), respectively. The presence of the counteranion significantly affects the third propagation rate, lowering the barriers up to 20 kJ mol-1. Comparison of the first termination and the third propagation shows that they are not competitive, with the termination being less facile. We also studied the initiation and propagation steps for the hafnocene catalyst and found that the Hf catalyst slightly favours the CL CROP in comparison to the Zr catalyst. Analysis of solvent and dispersion interaction demonstrates that both factors play an important role in the process. NCI analysis reveals weak (van der Waals) interactions at the contacts between the cationic species and the counteranions during the reaction course. Overall, our results offer insights into the structures and interactions involved in the polymerisation.

Lysine-based non-cytotoxic ultrashort self-assembling peptides with antimicrobial activity.

Peptide-based molecules and their hydrogels are useful materials for biomedical applications due to the reversible nature of their self-assembly as well as the diversity of nanostructures that can be created starting from low-molecular weight compounds. In this study, we have focused on comprehending the characteristics of fibrillar networks of l-lysine-based self-assembled dipeptide hydrogels with a focus on their antibacterial properties. For that purpose, l-lysine has been complemented with hydrophobic aromatic moieties coming from l-phenylalanine and benzyloxyxarbonyl N-capping. In addition, the peptide C-terminus is blocked with alkylamides of different chain lengths which introduces additional dispersive interactions and hydrophobicity. These materials were well characterized by transmission electron microscopy, scanning electron microscopy, wide-angle powder X-ray diffraction and oscillatory rheology. Finally, biocompatibility and antimicrobial tests were performed showing that these hydrogels are compatible with HEK 293 cells and present a remarkable antibacterial activity against both Gram positive (S. aureus) and Gram negative (E. coli) bacteria.

Self-association as a solubility limiting factor of riboflavin in aqueous media.

Single crystal X-ray diffraction analysis of needle shaped riboflavin (RF) crystals revealed π-stacking of RF's isoalloxazine units (distance: 3.643-3.313 Å) with syn-orientated ribityl chains. In line with this, classical molecular dynamics (MD) (400 ns) using an isobaric-isothermal (NPT) ensemble of eight RF in a water box (〈V〉 ∼ 508.62 nm3, 〈p〉 = 1.11 bar) revealed anti-aligned aggregation of RF in water (COM-distance: 4 Å). Comparing umbrella sampling for the separation of two RF molecules to the separation of two lumichrome molecules, the similar mean potential force for the separation of RF and lumichrome (22.8 kJ mol-1; 24.4 kJ mol-1) proved dispersive interactions as the origin of RF's aggregation. Though stacking of RF is the major water-solubility limiting factor, the conformation of RF's ribityl chain may alter the solubility in water. Both, MD (in water) and COSMO-RS (in water continuum) predicted that conformations of RF with an extended ribityl chain are thermodynamically preferred over any conformations with internal hydrogen bonds between hydroxyl groups and nitrogen/oxygen atoms of the pyrimidine moiety of the flavin ring. Interestingly, COSMO-RS predicted the solubility of the extended conformation to be significantly lower than the latter leading to the very low average solubility of RF. Nuclear Overhauser effect measurements (NOESY) of the structurally related sodium riboflavin 5'-monophosphate (RF-PO4) in deuterium oxide confirmed π-stacking of the isoalloxazine rings. In conformity with the 350 times higher water-solubility of RF-PO4, NOESY also indicated a contorted conformation of the ribityl phosphate chain, whereas, for RF, indications for a contorted chain were not observed.

Отклик химических связей никеля на растягивающие деформации кристалла Ni-пиридиндикарбоксамида

We have carried out a theoretic research of plasticity for the coordination and noncovalent bonds modelling uniaxial mechanical deformation of the crystal cell of bis(2-N,6-N-dibutylpyridin-2,6-dicarboxamide)-nickel (II) dichloride. For this purpose, we have modeled stretching deformation of the crystal structure along its crystallographic axes using the 3-corrected Hartree-Fock method with the following semi-empirical corrections for the weak interactions (the Grimme correction of dispersion interactions, D3, basis set superposition error removal by the atom-pair wise geomet-rical counterpoise correction, gCP, and correction of short-ranged basis set incompleteness effects, SRB) with the use of periodic boundary conditions. We have concluded that the geometry of bis(2-N,6-N-dibutylpyridin-2,6-dicarboxamide complex has high stability to the increased defor-mations. We have carried out the analysis of the bond lengths and dihedral angels within the metal complex, which has shown insignificant changes of bond lengths, in particular, the bond length change is equal to 4.3 % for N…Ni…N and 5.4 % for Ni…O. The conformation straightening ef-fects of one of the N-butylamine chain has been found under the high stretching deformation of the crystal cell (7–8 Å) due to analysis of dihedral angles and the distance between specific atoms of N-butylamine chain that proves the hypothesis about a forced and twisted conformation state of bis(2-N,6-N-dibutylpyridin-2,6-dicarboxamide. In addition, we have found the appearance of a cavity and a crack at the last deformation steps (8–10 Å), which is caused by shifts of neighbour-ing metal complexes in relation to each other; it influences the location of chloride ions. It is noteworthy that cavities and cracks are formed regardless of the axis choice along which the ten-sile deformation is modeled. This fact indicates that the crystal should not exhibit elasticity, but rather brittleness.

The nature of metallophilic interactions in closed-shell d8-d8 metal complexes.

We have quantum chemically analyzed the closed-shell d8-d8 metallophilic interaction in dimers of square planar [M(CO)2X2] complexes (M = Ni, Pd, Pt; X = Cl, Br, I) using dispersion-corrected density functional theory at ZORA-BLYP-D3(BJ)/TZ2P level of theory. Our purpose is to reveal the nature of the [X2(CO)2M]⋯[M(CO)2X2] bonding mechanism by analyzing trends upon variations in M and X. Our analyses reveal that the formation of the [M(CO)2X2]2 dimers is favored by an increasingly stabilizing electrostatic interaction when the M increases in size and by more stabilizing dispersion interactions promoted by the larger X. In addition, there is an overlooked covalent component stemming from metal-metal and ligand-ligand donor-acceptor interactions. Thus, at variance with the currently accepted picture, the d8-d8 metallophilicity is attractive, and the formation of [M(CO)2X2]2 dimers is not a purely dispersion-driven phenomenon.

Maximizing Photoelectrochemical Performance in Metal-Oxide Hybrid Composites via Amorphous Exsolution-A New Exsolution Mechanism for Heterogeneous Catalysis.

Exsolution generates metal nanoparticles anchored within crystalline oxide supports, ensuring efficient exposure, uniform dispersion, and strong nanoparticle-perovskite interactions. Increased doping level in the perovskite is essential for further enhancing performance in renewable energy applications; however, this is constrained by limited surface exsolution, structural instability, and sluggish charge transfer. Here, hybrid composites are fabricated by vacuum-annealing a solution containing SrTiO3 photoanode and Co cocatalyst precursors for photoelectrochemical water-splitting. In situ transmission electron microscopy identifies uniform, high-density Co particles exsolving from amorphous SrTiO3 films, followed by film-crystallization at elevated temperatures. This unique process extracts entire Co dopants with complete structural stability, even at Co doping levels exceeding 30%, and upon air exposure, the Co particles embedded in the film oxidize to CoO, forming a Schottky junction at the interface. These conditions maximize photoelectrochemical activity and stability, surpassing those achieved by Co post-deposition and Co exsolution from crystalline oxides. Theoretical calculations demonstrate in the amorphous state, dopant─O bonds become weaker while Ti─O bonds remain strong, promoting selective exsolution. As expected from the calculations, nearly all of the 30% Fe dopants exsolve from SrTiO3 in an H2 environment, despite the strong Fe─O bond's low exsolution tendency. These analyses unravel the mechanisms driving the amorphous exsolution.

In Ukrainian

Creation of new "targeted delivery" drugs is one of the priority areas of pharmacology. This is especially true for oncology. Medicinal substances, in particular of the anthracycline series, immobilized on the surface of nanosized carriers for the targeted delivery of drugs to target organs or target tissues, allow creating an optimal concentration of the drug in the area of therapeutic effect. The latter significantly reduces systemic toxicity by reducing the total dose and longer retention in the lesion, as well as increasing the solubility and bioavailability of drugs. One of the promising excipients are nanocarbon materials, in particular, fullerene (C60) and original and modified graphene. To date, the specifics of the interaction of epirubicin with a graphene-like plane (GP) and fullerene at the atomic level remain poorly understood. Therefore, the energy parameters of the interaction of HP and C60 with epirubicin in various protolytic forms, which exist at different pH values of the aqueous medium, were investigated using quantum chemistry methods. Calculations were performed using the MOPAC2016 program using the PM6-D3H4X method, in which, in addition to taking into account hydrogen bonds, dispersion interactions are also taken into account. Based on the analysis of the results of quantum chemical studies, the thermodynamic probability of the epirubicin adsorption process on GP is predicted in the entire pH range of the aqueous medium, as evidenced by the negative values of interaction enthalpies in all four cases. It has been found that epirubicin (protonated form) will have the greatest adsorption both on the graphene plane (-209.1 kJ/mol) and upon interaction with the fullerene molecule (-121.3 kJ/mol).