


Том 60, № 9 (2019)
- Год: 2019
- Статей: 19
- URL: https://bakhtiniada.ru/0022-4766/issue/view/9829
Article
Aromaticity and Induced Current Study of C8H8( n+2) (n = −6, −4, −2, 0): In the Viewpoint of Huckel’s Rule
Аннотация
The (4n+2)π aromatic systems are studied in variants of C8H8( n+2) (n = −6, −4, −2, 0) via the localized orbital localization (LOL) and the electron localized function (ELF) by considering the induced current density. In this work, a four-electron dia-tropic (aromatic) ring current for (4n+2)π variants of C8H8( n+2) (n = −6, −4, −2, 0) and a two-electron paratropic (anti-aromatic) current for (4n)π arepredicted. With the HOMO and LUMO energies and also the HOMO/LUMO overlap in the whole space, it is possible to predict the transition states from delocalized currents in carbocyclic compounds to nitrogen-localized currents in all heterocyclic compounds in viewpoint of aromaticity and antiaromaticity. In addition, NICS and SNICS values confirm the degree of aromaticity and antiaromaticity in these rings.



Compositional Homogeneity and Optical Properties of Stoichiometric Lithium Niobate Crystals of Various Geneses
Аннотация
It is shown that the method of high temperature top-seeded solution growth (HTTSSG) can be used to obtain near stoichiometric LiNbO3 crystals from a congruent melt with the addition of 6.0 wt.% of the K2O flux. The structure of complex defects containing OH− groups in these crystals is close to those in stoichiometric crystals grown from a melt containing ∼ 58.6 mol.% of Li2O. However, the former are significantly superior to the latter in terms of total optical and structural homogeneity. The obtained crystals are studied using laser conoscopy, photoinduced light scattering, measuring the fundamental absorption edge, IR absorption spectroscopy in the region of OH− stretchings, Raman spectroscopy in the region of two-particle states of acoustic phonons with zero total wave vector.



Bis-Hexaaquasodium Decaaqua-Monohydrogen-Hexasodium-Gadolinium-bis-(Nitrilo-Tris-Methylenephosphonate) Tetrahydrate: Synthesis, Structure, Chemical Bonding
Аннотация
Bis-hexaaquasodium decaaqua-monohydrogen-hexasodium-gadolinium-bis-(nitrilo-tris-methylenephosphonate) tetrahydrate [Na(H2O)6]2[GdNa6H(H2O)10{N(CH2PO3}2]·4H2O (space group P21/c, Z = 2, a = 11.8168(7) Å, b = 10.5403(9) Å, c = 19.8094(10) Å, β = 94.232(5)) has been synthesized and isolated. The Gd3+ ion is coordinated in the configuration of an elongated rhombohedron in the environment of two acid residues {N(CH2PO3)3}. Two rhombohedron’s vertices distant from its center are occupied by nitrogen atoms, and six nearest vertices are occupied by oxygen atoms. Six sodium ions form inorganic bridges P-O-Na-O-P. The structure of the obtained complex is confirmed spectroscopically. XPS data indicate the formation of coordination bonds Gd-N and multiple bonds Gd-O.



Crystal, Molecular, Electronic Structures and Spectroscopic Characteristics of N-Hydroxyamide of 3-[3,3-Dimethyl-1,2,3,4-Tetrahydroisoquinolin-1-Iden]-2-Oxopropanoic Acid
Аннотация
X-ray crystallography, quantum chemical modeling, IR, and electron spectroscopy methods are used to establish the structure of N-hydroxyamide of 3-[3,3-dimethyl-1,2,3,4-tetrahydroisoquinolin-1-iden]-2-oxopropanoic acid (1) possessing antifungal activity. It is shown that compound 1 exists in the form of an enamino-ketone-hydroxamic isomer in both crystalline state and solutions. The total charges on the atoms of the tetrahydroisoquinoline fragment and the atoms of the substituent in position 1 in molecule 1 are +0.425 e and −0.425 e, respectively. The structural and spectroscopic characteristics can be used in the studies of similar compounds.



Experimental and Theoretical Study of the Raman Spectra of Ganoderic Acid T
Аннотация
Ganoderic acid T (GAT) has many pharmacological functions such as antitumor and antimycobacterial activity. However, to the best of our knowledge, no commercial high-purity GAT is available and the experimental and theoretical study of the Raman spectrum of GAT has never been reported up to date. Therefore, in this work, we extracted GAT and purified from Ganoderma lucidum mycelia, measured its Raman spectrum and analyzed it based on the density functional theory (DFT) calculation at the B3LYP/6-311+G(d,p) level. The research on the molecular, structural, and spectral properties may provide deeper insights into the functions and better applications of GAT.



Frequency Dispersion of the Electroelasticity Modulus in Aqueous Electrolyte Solutions
Аннотация
Friction coefficients βa and βb, relaxation times τa, τb, τab, and ∈(ω) for aqueous solutions of LiCl, NaCl, KCl, RbCl, CsCl are numerically calculated as functions of concentration c, density ρ, and temperature T in a wide range of frequencies ω using analytical expression for the electroelasticity modulus ∈(ω) obtained previously in the case of exponentially relaxing flows for a specific form of potential energy corresponding to the interaction between structural units of solution Φab(r) and the equilibrium radial distribution function gab(r). The obtained theoretical data are presented in the form of tables and graphs and are shown to be in a satisfactory agreement with experimental results.



Estimating Crystality Index of Microcrystalline Cellulose Using Diffraction Methods
Аннотация
Microcrystalline cellulose samples are studied by X-ray diffraction. The technique of the diffraction experiment allows achieving higher accuracy and reliability when interpreting the data obtained for plant materials. The determined crystallinity indices of cellulose are compared using several X-ray techniques.



Structural Studies of Lake Baikal Natural Gas Hydrates
Аннотация
The structure of near-bottom gas hydrate samples obtained in Lake Baikal during the expeditions in 2005–2018 are reported. The hydrates contain mainly methane and ethane. More than 85% of the samples contain hydrate of cubic structure I (sI) with up to 4.2 mol.% ethane. The concentration of ethane in the samples containing hydrate of cubic structure II (sII) is 12–14 mol.%. Refined unit cell parameters of natural hydrates are in good agreement with the data obtained in the studies of artificially synthesized hydrates. Possible mechanisms for the formation of sII hydrates are discussed. Some arguments are provided in favor of a probable presence of dispersed gas hydrates in the near-bottom layers of Baikal sediments and the possibility of small variations in the composition of hydrate gas in different hydrate fragments taken from the same hydrate layer.



Synthesis, Crystal Structure, and Optical Property of Ce4InSbS9
Аннотация
Quaternary sulfide Ce4InSbS9 is prepared at 1223 K in an evacuated silica tube. It crystallizes in the chiral tetragonal space group P41212 (No. 92) with a = 10.1961(3) Å, c = 28.128(2) Å, V = 2924.2(2) Å3, Dcalc = 4.932 g/cm3, and Z = 8. The structure features infinite 21 helical chains [In2Sb2S1110−]∞ propagating along the c direction separated by Ce3+ cations and S2− anions. The UV/Vis diffuse reflectance spectroscopy study shows that the optical gap of Ce4InSbS9 is about 2.07 eV, showing a red shift with respect to corresponding sulfide La4InSbS9, which is attributed to the allowed electronic transfer from the narrow Ce4f level to the conduction band, mainly built from empty Ce5d orbitals. The magnetic susceptibility measurement indicates antiferromagnetic interactions between Ce3+ cations.



New Chalcogenide Cobalt Complexes with Diimine Ligands: Synthesis and Crystal Structure
Аннотация
Reactions of a low-valent cobalt complex [Co(nacnac)(η6-C7H8)] (1) ((nacnac)− = (HC(C(Me)NC6H3-iPr2)2)−) with selenium and tellurium are studied. Two new binuclear complexes [(Co(nacnac))2(μ,η2-Se2)] (2) and [(Co(nacnac))2(μ,η2-Te2)] (3) have been isolated and characterized. The structures of the complexes are determined by single crystal X-ray diffraction.



Network Coordination Polymers Based on Thieno[3,2-b]Thiophene-2,5-Dicarboxylic Acid
Аннотация
Heating the solutions of Mn(II), Cd(II) salts and thieno[3,2-b]thiophene-2,5-dicarboxylic acid (H2[3,2-b]ttdc) in N,N-dimethylformamide (DMF) or N,N-dimethylacetamide (DMA) results in the formation of crystalline complex compounds [Mn2([3,2-b]ttdc)2(dmf)2]·4DMF (1), [Cd2([3,2-b]ttdc)2(dmf)2]·2DMF (2), and [Mn2([3,2-b]ttdc)2(dma)2]·2[Mn(dma)6](ClO4)2 (3). According to the X-ray diffraction data, the compounds are two-dimensional layered coordination polymers with square network topologies. In compounds 1 and 2 the layers are shifted relative to each other, while in 3 the layers are located exactly one above another to form extended 9.5×13.0 Å channels occupied by solvated [Mn(dma)6]2+ complex cations and perchlorate ClO4− anions located mainly near thienothiophene groups.



Polyazamacrocyclic Copper-Based Cyanide-Bridged Bimetallic Sandwich-Like Complexes: Synthesis, Crystal Structure, and Magnetic Properties
Аннотация
By employing three dicyanometallates as building blocks (K[Fe(bpb)(CN)2], K[Cr(bpb)(CN)2] (bpb2− = 1,2-bis(pyridine-2-carboxamido)benzenate), K[Fe(bpmb)(CN)2] (bpmb2− = 1,2-bis(pyridine-2-carboxamido)-4-methyl-benzenate)) and one 14-membered polyazamacrocycle Cu(II) compound as an assembling segment, three cyanide-bridged complexes {[Cu(6,13-dihydroxylcyclam)][Fe(bpb)(CN)2]2}·2CH3OH·H2O (1), {[Cu(6,13-dihydroxylcyclam][Cr(bpb)(CN)2]2}·2CH3OH (2), and {[Cu(6,13-dihydroxylcyclam)][Fe(bpmb) (CN)2]2}·2H2O (3) (6,13-dihydroxylcyclam = 6,13-dihydroxyl-1,4,8,11-tetraazacyclotetradecane) are successfully prepared and characterized by elemental analysis, IR spectroscopy and X-ray structure determination. The single X-ray diffraction analysis shows that all the three complexes containing the M2Cu (M = Fe, Cr) core have neutral trinuclear sandwich-like structures in which the central Cu(II) ion is face-to-face coordinated to two Fe or Cr ions of the cyanide precursors functioning as a monodentate ligand through one of its two cyanide groups. The investigation of their magnetic properties reveals the antiferromagneitic and ferromagnetic coupling between the cyanide-bridged Fe(III)-Cu(II) and Cr(III)-Cu(II) ions, respectively.



Synthesis and Crystal Structure of Chloride complexes of Rh(III) Diammino- and Monoammino Series
Аннотация
Complex compounds cis-K[Rh(NH3)2Cl4]·KCl (I), cis-K[Rh(NH3)2Cl3(NO2)] (II), and K2[Rh(NH3)Cl5] (III) are synthesized. The single crystal X-ray diffraction analysis of the compounds obtained is performed at T = 296 K. Crystallographic data for I are: a = 11.822(5) Å, b = 11.608(5) Å, c = 8.196(4) Å, β = 107.56(2)°, space group C2/m, Z = 4, dcalc = 2.431 g/cm3. For II: a = 8.946(3) Å, b = 5.941(2) Å, c = 8.182(3) Å, space group Pmn21, Z = 2, dcalc= 2.509 g/cm3. For III: a = 13.464(6) Å, b = 9.989(4) Å, c = 6.932(3) Å, space group Pnma, Z = 4, dcalc = 2.675 g/cm3. The compounds are characterized by IR spectroscopy, powder X-ray diffraction, and chemical analysis.



Main Alkaloids of Securinega suffruticosa. Nitrogen Atom Inversion in Securinine
Аннотация
The main alkaloids such as securinine (1), allosecurinine (2), and securitinine (3) are isolated from the Securinega suffruticosa plant and identified by spectral techniques. The spatial structure of 3 is determined by single crystal XRD. The inversion of the pyramidal-tetrahedral nitrogen atom of compound 1 in the crystal and the solution is analyzed based on single crystal XRD and NMR spectroscopy data. By the computational methods and NMR spectroscopy it is shown that the configuration of the nitrogen atom in securinine is related to the alkaloid salt formation rather than the crystal field effect (packing factor).



A Complex Powder X-Ray Diffraction Study of Copper-Cerium Oxide Catalysts Prepared by the Pechini Method
Аннотация
By means of a complex of powder X-ray diffraction techniques the features of the structural organization of highly dispersed copper-cerium CuO-CeO2 catalysts prepared by the Pechini method are studied. The current structural technique for studying nanomaterials, namely the atomic pair (interatomic distances) distribution function analysis, is used to refine the phase composition of materials with revealing highly dispersed compounds, sizes of atomic ordering regions, and possible defects. It is shown that materials synthesized from polymeric precursors represent mixed CuO-CeO2 oxides with a high concentration of structural defects. Highly dispersed individual copper compounds are not detected. The results obtained support the previous assumptions that copper cations can incorporate into the structure of cerium dioxide in the composition of copper-cerium catalysts.



Structure Formation Model in the Pt/C-CNT-Nafion System
Аннотация
Based on the data of electron scanning and transmission microscopy, X-ray energy-dispersive spectroscopy (EDS), voltammetry, and electrochemical impedance spectroscopy the structures of composite electrode materials are modeled. Materials with a mixed (electron and proton) conductivity, which contain platinum nanoparticles on carbon black (Pt/C, electron conductor), the proton-conducting polymer Nafion (fluorocarbon polymer containing sulfo groups), and two types of additives of nanostructured carbon materials (carbon nanotubes (CNTs) and thermally expanded graphite (TEG)) are investigated. Concentration profiles of elements (EDS data) obtained by scanning sample surfaces and features of the dependences of the electrochemically active platinum surface area and concentration dependences of the electron and proton resistance on the Nafion concentration in the material are analyzed. It is shown that the structure of the material, in particular, the proton-conducting polymer Nafion, depends on the type of the additive. Structural models of the materials studied are proposed.



Molecular Dynamics Simulation Evaluating the Hydrophilicity of Nanowollastonite on Cellulose
Аннотация
To clarify the effect of nanowollastonite on the hydrophilicity of wood and wood-composite, water adsorption on the cellulose surface in the presence of nanowollastonite is investigated using a molecular dynamics method. The simulations reveal the adsorption of nanowollastonite on the cellulose surface. When nanowollastonite-cellulose gets into contact with water molecules, new hydrogen bonds form between nanowollastonite and water molecules. Consequently, the hydrogen bonds between nanowollastonite and the cellulose surface are weakened and eventually broken. As the exposure to water molecules is continued, water molecules rapidly form more hydrogen bonds with cellulose. Close agreement is found between the previous experimental observations and the theoretical results of the present research. It is concluded that nanowollastonite can only decrease the cellulose hydrophilicity for a short time.



Erratum
Erratum to: Synthesis and Structural Characterization of a Monomeric Mixed Ligand Copper(II) Complex Involving N,N,N′,N′-Tetramethylethylenediamine and Mefenamate
Аннотация
In the original article there was a mistake in the information of the corresponding author. The correct spelling of the names of the authors and their order is: S. S. Batool1,2*, S. R. Gilani1, S. S. Zainab2, M. N. Tahir3, W. T. A. Harrison4, Q. Syed5, and S. Mazhar5





