Journal of Structural Chemistry最新文献

Properties of molecular electron density functionals are studied. The Kohn potential can be considered as the potential density of the system′s particles whose integration gives the energy of the molecule′s quantum state. Unambiguous expressions for molecular electron energies are obtained in the form of the Kohn potential integrals using a simplified wave density model based on the nuclear wave density isolation. A one-electron Schrödinger equation with an effective potential for calculating molecular orbitals is presented. The equation can be used to calculate 3D electron density of molecules in ground and excited states.

A series of 5-(2,4-dichlorophenyl)-1,3,4-oxadiazole-2-thione alkyl derivatives are obtained. Structures of the products are determined from the IR, UV, ¹H and ¹³C NMR spectroscopic results together with single crystal X-ray diffraction (XRD). The aromaticity of the 1,3,4-oxadiazole ring is estimated by single crystal XRD and DFT calculations using the Multiwfn program package. It is found that in S-derivatives, the π electron system is redistributed in the pseudo-aromatic 1,3,4-oxadiazole-2-thione moiety relative to initial 5-(2,4-dichlorophenyl)-1,3,4-oxadiazole-2(3H)-thione. In the S-derivatives of 5-(2,4-dichlorophenyl)-1,3,4-oxadiazole-2-thione the aromaticity of the 1,3,4-oxadiazole heterocycle is lower than that in N3-derivatives.

In order to develop the application of 1,3,4-oxadiazole compounds in the direction of fluorescent probes, we modified the probes by introducing 2-(bromomethyl)pyridine on the amino group of 1,3,4-oxadiazole derivatives, and synthesized HL1(2-(5-(2-aminophenyl)-1,3,4-oxadiazol-2-yl)-N-(pyridin-2-ylmethyl)aniline). Its structure was characterized by NMR, HRMS and single crystal X-ray diffraction. The weak interaction of HL1 was analyzed by using Multiwfn to draw Hirshfeld surface. The HOMO and LUMO orbitals of HL1 were analyzed in B3LYP/6-311++G basis set using DFT theory. HL1 is highly selective to Sn⁴⁺ in ACN, LOD = 5.08∙10^–7 M, Ka = 1.73∙103M^–1.

Schiff-based compounds, which represent an important class in the field of organic compounds, form the basis of this research article. This research article aims to investigate the synthesized compound (E)-4-methoxy-2-(((2-phenoxyphenyl) imino) methyl) phenol using experimental methods. FTIR, UV-Vis, 13C and 1H nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction methods were used to elucidate the structural properties of the compound synthesized at the end of chemical processes. The structure solution was carried out from the data obtained as a result of X-ray analysis. According to these results, one of the two compounds in the asymmetric cell completed their formation in the enol-imine form and the other in the keto-amine form. This structural situation, which is rare in the literature, was supported and explained by FTIR, 13C and 1H NMR spectroscopy studies. According to the results obtained as a result of UV-Vis spectroscopy, the structure revealed that the enol-imine form was dominant. The reasons for this situation were explained.

The ZrO₂–HfO₂ oxide films are prepared by pulsed chemical vapor deposition using volatile organometallic precursors. It is shown that the morphology, thickness, and uniformity of the resulting coatings are affected by the mode of reaction space organization. A 360 nm thick oxide coating is obtained by introducing the precursor vapor and the reactant gas into the reactor through an earlier elaborated system of separate reaction components supply. The atomic force microscopy data show that the resulting surface is almost smooth and has an arithmetic average roughness of a few nanometers. Current-voltage and capacitance-voltage characteristics of the obtained ZrO₂–HfO₂ oxide coatings are studied. It is noted that the breakdown electric field is almost independent of the oxide coating thickness (0.1-0.48 MV/cm) in the interval of 225-325 nm. The breakdown electric field increases as the oxide film thickness increases from 325 nm to 360 nm. The dependence of the dielectric constant on the oxide film thickness is determined from the measured capacitance-voltage characteristics of the obtained ZrO₂–HfO₂ films. It is shown that this dependence depends linearly on the film thickness.

A mixture of two structurally different cluster phases I and II with the general chemical formula W₅Br₁₂·BiBr₃ is obtained as a product of the WBr₆ reduction reaction with elemental bismuth at 280 °C. The elemental composition of the mixture is determined by the energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry. For the single crystals selected from a mixture of phases I and II their crystal structures are determined, and the powder X-ray diffraction analysis is performed for the polycrystalline mixture. In the crystal structure of I, square-pyramidal cluster fragments are bridged by bromine atoms into infinite chains by the W–Br^a–a–W interaction. In the structure of II, BiBr₃ (W–{Br^aBiBrBr^a}–W) molecules incorporate into the chain instead of the bridging bromine atom.

An XRD study is conducted at 150(2) K for two complexes: tris-(1,1-difluoroacetylacetonato)scandium(III) ([Sc(dfac)₃]) and tris-(5,5,6,6,6-pentafluorohexane-2,4-dionato)scandium(III) ([Sc(5Fac)₃]). Crystal data for C₁₅H₁₅F₆O₆Sc: Pbca space group, a = 15.5725(3), b = 13.8414(3), c = 17.2587(3) Å, V = 3720.03(13) Å³, Z = 8; for C₁₈H₁₂F₁₅O₆Sc: (Pbar{1}) space group, a = 12.2258(5), b = 13.0513(5), c = 15.6120(6) Å, α = 86.740(1), β = 88.605(1), γ = 81.479(1)°, V = 2459.29(17) Å³, Z = 4. Both structures are composed of neutral molecules, the metal atom coordinates six oxygen atoms of three β-diketone ligands. The Sc–O distances vary from 2.074(3) Å to 2.093(3) Å in [Sc(dfac)₃] and from 2.069(3) Å to 2.118(3) Å in [Sc(5Fac)₃]. The molecules in the crystals of both compounds are connected only Van der Waals interactions and form a pseudo-layered structure with a hexagonal molecular arrangement inside the layer. The shortest Sc⋯Sc distances are 7.673(1) Å in [Sc(dfac)₃] and 7.4359(9) Å and 7.4007(9) Å in [Sc(5Fac)₃]. The analysis of Hirshfeld surfaces shows that H⋯H, F⋯H, and F⋯F are the main intermolecular contacts in the packing of these complexes. A comparison with known tris-β-diketonate scandium complexes is performed, and the influence of the structure and the nature and number of intermolecular interactions in the crystals of the studied compounds on their thermal properties is analyzed.

A synthesis procedure for composite precursors of the composition yttrium-stabilized zirconia nanoparticles – 2,2,6,6-tetramethyl-3,5-heptandionato-hafnium(IV) is developed. The thermal behavior of the synthesized composites is studied by the complex thermal analysis up to 600 °C in a wide concentration range. Main components of thermolysis products are determined by the energy-dispersive X-ray (EDX) analysis. Features are revealed in TG curves for all compositions in the temperature range of 310-410 °C. From the IR, XPS, and EDX data it is found that the observed effects are due to low-temperature decomposition of a small part of the volatile metal-organic precursor irreversibly absorbed on the surface of nanoparticles. A hypothesis is put forward that irreversible adsorption is caused by Lewis acid centers on the surface of nanoparticles. The obtained information about the thermal properties of composite precursorscan facilitate the development of methods to control nanoparticle concentrations in the coating formed.

The possibility of forming molecular Ag(I) complexes with tris(3,5-dimethylpyrazol-1-yl)methane (HC(3,5-Me₂pz)₃) and fluorinated β-diketones (hexafluoroacetylacetone (Hhfac) and trifluoroacetylacetone (Htfac)) is tested to expand the library of potential precursors for the chemical vapor deposition of Ag containing materials. It is established that the interaction of HC(3,5-Me₂pz)₃ with silver β-diketonates leads to the formation of [Ag{HC(3,5-Me₂pz)₃}₂]⁺ cationic complexes. At the same time, a stable desired product [Ag{HC(3,5-Me₂pz)₃}hfac] (L = hfac) was isolated and characterized. The structures of [Ag{HC(3,5-Me₂pz)₃}₂](tfac) and as series of solvates [Ag{HC(3,5-Me₂pz)₃}(hfac)]·½THF and [Ag{HC(3,5-Me₂pz)₃}₂](L)Solv_x (L = hfac, Solv = Et₂O (x = ¼), C₇H₈ (x = ½), CHCl₃ (x = 1); L = tfac, Solv = THF (x = 1)) are determined by XRD. Structures of the cationic and molecular complexes are compared with those of related compounds.

Drug transport to specific areas of the body is accomplished by drug delivery systems. Components of these systems are often biodegradable and bioabsorbable polymers. The elaboration of effective drug delivery methods can, along with the search for new drugs, significantly enhance the development of corresponding therapeutic strategies. In the present work, the possibility of utilizing chitosan to deliver antiviral drugs is studied using the density functional theory (DFT, B3LYP-D3(BJ)/6-311+G(d,p)). The energies of frontier molecular orbitals and fundamental DFT indices are calculated, densities of electronic states are analyzed. The results indicate that medicinal compounds are adsorbed on chitosan by H-bonds, and the strongest bond energy between chitosan and ivermectin B1b is –34.83 kcal/mol. The analysis of reactivity descriptors for the interaction of chitosan with hydroquinone, chloroquine, and hydroxychloroquine reveals specific interactions indicating that these complexes are not stable. In view of the chitosan compatibility with the human body, its non-toxicity, and the possibility to control the release of medicinal compounds due to such factors as pH, solubility, and ionic strength, we propose to use this compound as a system for the delivery of medicinal compounds.