Ayrat R. Khamatgalimov

Electronic structure and stability of fullerene C82 isolated-pentagon-rule isomers.

All nine isolated-pentagon-rule isomers of fullerene C(82) were investigated by the DFT method with the B3LYP functional at the 6-31G, 6-31G*, and 6-31+G* levels. The distribution of single, double, and delocalized π-bonds in the molecules of these isomers is shown for the first time. The obtained results are fully supported by DFT quantum-chemical calculations of electronic and geometrical structures of these isomers. The molecules of isomers 7 (C(3v)), 8 (C(3v)), and 9 (C(2v)) contain some radical substructures (such as the phenalenyl-radical substructure), which indicates that they are unstable and cannot be obtained as empty molecules. Thus, there is a possibility of obtaining them only as endohedral metallofullerenes or exohedral derivatives. Isomers 1 (C(2)), 2 (C(s)), 4 (C(s)), 5 (C(2)), and 6 (C(s)) with closed electronic shell are supposed to be stable, resembling isomer 3 (C(2)), which has just been extracted experimentally as an empty fullerene. We assume they can be produced as empty molecules.

Electronic Structure and Stability of C80 Fullerene IPR Isomers

The distribution of single, double and delocalized π - bonds in molecules of seven IPR isomers of fullerene C80 has been shown. Phenalenyl-radical substructures are the reason for molecular instability of unstable isomers. A distortion of hexagons and pentagons has been shown to be a property of molecules of all isomers of fullerene С80, but maximum distortions, similarly to C70, occur in hexagons with delocalized π – bonds that do not affect fullerene stability.

Stability of Isolated-Pentagon-Rule Isomers of Fullerene C76

The structures of both IPR-isomers of C76 fullerene with distributed single, double and delocalized bonds are presented for the first time. Obtained results are fully supported by DFT quantum-chemical calculations of electronic and geometrical structures of these isomers. The main reason of instability of isomer 2 (Td) is presence of four phenalenyl-radical substructures, whereas stable isomer 1 (D2) has the closed electronic shell. Thus, there is a possibility to obtain isomer 2 (Td) only as endohedral metallofullerenes or exohedral derivatives.

Synthesis and antimicrobial activity evaluation of some novel water-soluble isatin-3-acylhydrazones

By acid-catalyzed reaction of substituted isatins with Girard’s reagent T, new water-soluble isatin-3-acylhydrazones were obtained with high yields. Their antimicrobial activity was evaluated. Selective activity against Gram-positive bacteria (S. aureus 209p and B. cereus 8035) and yeast-like fungus Candida albicans 855–653 along with low hematoxicity was established.Graphical abstract

Stability of the Non‐IPR Isomers 6140 (D3) and 6275 (D3) of Fullerene C68

The distribution of single, double and delocalized π‐bonds in molecules of non‐IPR isomers 6140 and 6275 of fullerene C68 has been shown for the first time. The reason of instability of both “empty” isomers has been shown to be presence of pentalene and phenalenyl‐radical substructures and local sterical strains in these molecules as well.

Molecular structures of the open-shell IPR isomers of fullerene C90

ABSTRACT Fifteen open-shell isomers off the forty six IPR isomers of fullerene C90 were found and investigated: 5 (Cs), 7 (C1), 9 (C1), 10 (Cs), 11 (C1), 20 (C1), 21 (C1), 22 (C1), 23 (C2), 24 (C1), 25 (C2v), 41 (C2), 42 (C2), 43 (C2), and 44 (C2). According to developed by us approach the positions of single, double, and delocalized π-bonds in the molecules of these isomers are shown for the first time. The obtained results of electronic and geometrical structures are fully supported by DFT method with the B3LYP functional at the 6-31G and 6-31G* levels. Molecules of these open-shell isomers contain different radical substructures (mainly the phenalenyl-radical substructures), they should be unstable and could not be obtained as empty molecules. Nevertheless, there is a possibility of obtaining them in polymeric forms or as endohedral or exohedral derivatives.

Stabilization of IPR open-shell fullerenes C74 (D3h) and C76 (Td) in radical addition reactions

ABSTRACT The analysis of previously experimentally obtained and characterized by X-ray perfluoralkyl derivatives C74(D3h)(CF3)12 and C76(Td)(CF3)12 have shown for the first time that the most feasible positions of addends are phenalenyl-radical substructures and/or hexagons with delocalized pi-bonds, that lead to stabilization of these molecules. The most probable addition positions of H• and CF3• radicals to the «missing» fullerenes С74 (D3h) and С76 (Td) are revealed on the basis of developed approach of molecular modeling followed by DFT calculations. Radical addition reactions seem to be useful for stabilization of open-shell fullerenes.

Structural aspects of partial solid solution formation: two crystalline modifications of a chiral derivative of 1,5-dihydro-2H-pyrrol-2-one under consideration

The purposeful change of crystallization conditions for rac-3-chloro-5-hydroxy-1-(4-methylbenzyl)-4-[(4-methylphenyl)sulfanyl]-1,5-dihydro-2H-pyrrol-2-one 1 leads to two different crystal modifications, namely, a racemic compound in the triclinic space group P with Z′ = 1 (α-1) and a partial solid solution based on a racemic compound in the monoclinic space group P21 with Z′ = 4 (β-1). The first modification, α-1, is characterized by a higher density of the molecular packing in the crystal, while the second one, β-1, by a stronger system of hydrogen bonds and the presence of positional and substitutional disorder simultaneously. The analysis of the crystal structure of modifications α and β allowed us to define some structural aspects of the partial solid solution formation. Namely, the tendency to build a stronger hydrogen bond system enables the solution of enantiomers of 1 to be formed in the crystalline phase, whereas the propensity of the molecules to adopt a more favorable transoid conformation limits the solubility of the minor enantiomer.

Synthesis, Self-Association, and Solubilizing Ability of an Amphiphilic Derivative of Poly(ethylene glycol) Methyl Ether

A new amphiphilic derivative–methoxy(polyethoxy)ethyl stearate has been synthesized with the goal of creating therefrom systems for delivery and enhancement of bioavailability of piperine. The aggregation and solubilizing properties of ω-methylpoly(oxyethylene) stearate have been studied by means of a set of physicochemical methods.

Aggregation Capacity and Complexation Properties of a System Based on an Imidazole-Containing Amphiphile and Bovine Serum Albumin

A complex of physicochemical methods was used to study the aggregation characteristics of an imidazolium-containing amphiphile and its ability for complex formation with bovine serum albumin (BSA). Tensiometry showed that adding BSA to the surfactant decreases the aggregation threshold of the system by a factor of 50. Dynamic light scattering established, that the size of the surfactant–BSA complexes depends on the size of the polypeptide (6–10 nm) and is independent on the concentrations of the surfactant and BSA. The Stern‒Volmer constants and surfactant‒protein binding constants were calculated from fluorescence spectroscopy data.