Том 57, № 5 (2016)

Detailed quantum mechanical calculations of the interaction of cyclodextrin (α-, β-, and γ-CD) with 4-nitrophenol (I), 4-nitro-2,6-dimethylphenol (II), 4-nitro-3,5-dimethylphenol (III), and their anions (IVVI) with the formation of intercalation complexes are carried out for the first time. The calculations of the compounds are performed within the density functional theory by the hybrid Becke–Lee–Yang–Parr (B3LYP) method with LanL2DZ basis sets. For the α-CD+III and α-CD+VI complexes it is shown that a nitrophenol molecule of III and a nitrophenolate anion of VI are not contained in the α-CD torus, which agrees with the experimental equilibrium constants. It is found that the calculated equilibrium constants of the formation of guest–host complexes with phenolate anions are much larger than those of neutral molecules. The most stable CD complexes with nitrophenols and their anions should be expected for γ-CD. The β-CD complexes when the guest enters into the host cavity are formed only with compounds I, V, and VI.

On the example of a simple mechanical model (a linear chain of three bound atoms) it is shown that the equilibrium conditions of forces and force moments completely determine the linearly elastic properties of the structure and make it possible to find the number of free parameters of the quadratic force field.

In this work, an atrinuclear-oxo-centered complex of the CrFe₂ type with the CF₂ClCOO^– bridging ligand is newly synthesized. The complex is characterized by experimental and theoretical methods. The optimized geometry and theoretical vibrational frequencies are computed using the density functional theory (DFT) method. Also, the AIM analysis was applied to study changes in topological parameters such as the electron density at critical points of all the bonds of the complex. In the optimized geometry of the complex, three metal ions form a trigonal-planar structure with a μ₃-O atom in its center. Each of M³⁺ metal ions has an octahedral coordination environment of oxygen atoms. The DFT results are in agreement with the experimental ones, confirming the validity of the optimized geometry for the complex.

The work demonstrates the results of quantum chemical calculations of ¹⁹F and ¹³C NMR spectra of model fluorocarbon C_nF_2n+2 molecules with various configurations and hydrocarbon chain molecules. The possibilities to determine the chain length, formation of branches, identification of fluorine substitution for hydrogen during the fluorination of hydrocarbon paraffins and polymers are discussed.

Solid solutions Ba₂In₂O_5–0.5yF_y with the structure of brownmillerite are studied by IR and ¹Н MAS NMR spectroscopy. During the fluorine doping, the nearest oxygen environment of indium atoms is distorted and a part of In–O bonds is shortened. It is shown that partial fluoride ion substitution for oxygen atoms results in an increase in the proton mobility in hydrated Ba₂In₂O_5–0.5yF_y∙nН₂О phases.

Quantum dots (QDs) based on zinc sulfide are synthesized by a microwave method in an aqueous medium using dioctyl sodium sulfosuccinate (DS) or 4,4′-bipyridine (BP). Based on the analysis of X-ray diffraction profiles the conclusion is drawn that QDs obtained have a structure of cubic zinc blende with an average particle size of 5.6 nm for the ZnS_DS sample and 4.8 nm for ZnS_BP. Transmission electron microscopy images show the presence of spherical aggregates of particles only for ZnS_DS. FTIR data indicate the presence of sulfate ions in both samples; DS remains in the sample, facilitating the QD agglomeration, while BP is effectively washed out. From the optical diffuse reflectance spectra the band gap is estimated, which turns out to be larger than the expected one due to the presence of elemental sulfur in the samples and partial oxidation of the QD surface. The QD structure based on ZnS particles is also modeled in the work. The possibility to employ X-ray absorption near-edge spectroscopy for the verification of atomic structural parameters around zinc sites in QDs based on zinc sulfide is demonstrated.

In a recent work by Zelikman et al.(J. Struct. Chem., 2015, 56(1)), the molecular dynamics simulation of dimers of glycyrrhizic acid (GA) arising from the spontaneous collision of two GA molecules in water is performed. Several relatively stable dimer structures are found, and when a cholesterol molecule is inserted, associates are observed constituting a GA dimer with a cholesterol molecule “stuck” to it. Here, we simulate the associates consisting of three and four GA molecules and a cholesterol molecule. It appears that the cholesterol molecule, as a rule, also locates at the surface of the GA associate. Therewith, the trimers do not form any clear characteristic structures, as dimers do, and the tetramers can be two stuck dimers.

An interest in NiMoО₄–SiO₂ reduction stems from its promising use as catalysts for hydrodeoxygenation and hydrodesulfurization processes. The work exploits in situ X-ray diffraction to investigate phase transformations during NiMoO₄–SiO₂ reduction with hydrogen in a temperature range of 30-700°C. The α-NiMoО₄ reduction is shown to proceed in two stages. In the first stage, at 400-500°C, an intermediate state (Ni,Mo,□)O mixed oxide and Ni_1–xMo_x form. In the second stage, above 650°C, two solid solutions based on the Mo and Ni structures form. The structure of the intermediate state is refined by the Rietveld method. It is demonstrated that the Ni–Mo mixed oxide forms based on the NiO structure, which contains a certain number of cation vacancies.

The new mixed-ligand complex of [Tl(Ph₂phen)Cl₃(DMSO)] (1) is obtained from the reaction of TlCl₃∙4H₂O with 4,7-diphenyl-1,10-phenanthroline (Ph₂phen) in a methanol solution. Suitable crystals of 1 are obtained for the X-ray diffraction measurement by methanol diffusion into a DMSO solution. This complex is characterized by spectral methods (IR, UV-Vis, ¹H NMR, and luminescence), elemental analysis, thermal analysis (TG, DTA), and single crystal X-ray diffraction.

The titled complex is synthesized from the ethanolic solutions of 1-chloro-2,4-dinitrobenzene, 2-thiobarbituric acid, and 2-methylpyridine and characterized by spectral and elemental analyses. The single crystal X-ray diffraction results for the complex are compatible with the spectral observations. The titled complex exhibits anticonvulsant activity and reduces all phases of convulsion even at a low dosage. Acute toxicity studies of the complex are performed to understand the safer dose concentration for clinical trials.

This work is a brief review of the authors’ applications of Löwdin–Amos–Hall paired orbitals for the analysis of spin-polarized DFT solutions. The possibilities of this approach are demonstrated on the example (1) of models of Fe(III) hydroxocomplexes with two forms of the terminal oxo center, which are involved in the detachment of methane hydrogen, and (2) models of vanadium oxide experiencing the dissociation of the vanadyl group.

The previous multireference configuration interaction (MRCI) results show that the ground state ⁴Σ^– of the AlC molecule is basically single configurational in nature. In this paper, the potential energy curve (PEC) of ⁴Σ^– is calculated with the Brueckner coupled-cluster doubles with perturbative triple and quadruple corrections [BD(TQ)]. Basis set extrapolations with the correlation-consistent basis sets are performed. The efficiency and precision of the methods with different basis sets are compared. The calculated spectroscopic constants are in excellent agreement with the experimental ones. Our results reveal that the correlation from higher order excitations than doubles is very important for this system.

Proton acceptor abilities of some heterocyclic compounds of the pyrrole series are determined by data on the self-association of molecules. It is demonstrated that a change in the vibrational frequency ν_ас of the N–H group of associated molecules is observed in the transition from pyrrole to other compounds of this series. This change in the frequency is due to the inductive effect of the introduced structural fragments on the equilibrium electron configuration of the N–H group.

A new Cd(II) coordination polymer, namely [Cd(pbmb)(mip)]n (pbmb = 1,1′-(1,3-propane)bis-(2-methylbenzimidazole), H₂mip = 5-methylisophthalic acid), is hydrothermally synthesized and characterized by elemental analyses, infrared spectroscopy and single crystal X-ray diffraction analyses. It crystallizes in the triclinic space group \(P\overline 1 \), a = 0.2883(11), b = 11.3409(12), c = 13.2519(14) Å, α = 69.6950(10)°, β = 73.5850(10)°, γ = 63.8100(10)°, V = 1285.8(2) ų, Z = 2, C₂₈H₂₈CdN₄O₅, M_r = 612.94, D_c = = 1.583 g/cm³, μ = 0.896 mm^–1. In the complex, adjacent dinuclear units [Cd₂(pbmb)₂] are bridged by mip^2– ligands in the μ₂-η², η¹ coordination modes to construct 1D ladder-like chains which are additionally assembled into a 2D supramolecular network via C–H∙∙∙π interactions. Moreover, the luminescence properties of the complex are described.

Diamonds synthesized in the Mg_0.9–Ge_0.1–C system at high pressure-high temperature (HPHT) conditions are investigated by the EPR and luminescence methods. A new GeV paramagnetic center with the spin S = 1 and D_3d symmetry is detected in the EPR spectra of the Ge-doped samples, along with the impurity nitrogen (Р1) and silicon-vacancy defect KUL1 (SiV⁰) centers. The investigation demonstrates that this new center has a double semi-vacancy structure with the germanium atom in the center. The studied GeV center is in a neutral charge state and is assigned to the 602 nm system in the photoluminescence spectra.

The structure of (CH₃)₃Pt(ptac)Py (ptac = (CH₃)₃C(O)CHC(O)CF₃) is determined by single crystal X-ray diffraction (XRD) at a temperature of 150 K. The crystallographic data are as follows: space group P2₁/c, a = 8.5513(2) Å, b = 16.1089(3) Å, c = 14.0877(3) Å, β = 107.4060(10)°, V = 1851.75(7) ų, Z = 4, R = 0.0365. The structure is molecular; the coordination polyhedron of platinum is a distorted octahedron. The average Pt–O and Pt–CMe distances are 2.149(1) Å and 2.029(5) Å, respectively; the Pt–N distance is 2.179(2) Å, the chelate angle O–Pt–O = 89.77(8)°. The thermal properties of (CH₃)₃Pt(ptac)Py in the condensed phase are examined by thermogravimetry.