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The properties of the ground and low-lying excited states of methyl mercaptan (CH₃SH) are studied by using quantum chemistry methods. The geometric parameters and energies of the ground state and the triplet excited state are calculated in this work. It is shown that the calculated geometries of the ground and triplet state are stable and the triplet state potential energy surface has the repulsive feature. The calculated vertical excitation energies and vertical ionization potentials of methyl mercaptan are in best agreement with the experimental values. In addition, the vertical electron affinity and the adiabatic electron affinity of the CH₃SH molecule are also calculated.

The crystalline samples of the orthorhombic phase of H₅O₂⁺ClO₄^– (I) and D₅O₂⁺ClO₄^– (II) are examined by infrared (IR) absorption spectroscopy. Inaccuracies referring to the identification of II found in the literature are corrected. The work shows that a typical evidence of the crystallization of I is the doublet splitting ν(ОН) at 3232 cm^–1 and 3340 cm^–1; and a typical evidence of the crystallization of II is a similar doublet splitting n(ОD) at 2391 cm^–1 and 2484 cm^–1. In order to determine the doublet origin and to make clear how it depends on the concentration of hydrogen isotopes, specially prepared isotopically mixed crystalline samples of the composition (H_1–xD_x)₅O₂⁺ClO₄^– (III, x = 0.17–0.90) are studied. Observations of the concentration dependence of the doublet splitting are used to check the quality of the existing variants of the crystal structure of I. Agreement in the experiments with the samples of III is obtained when the structural model of the cation with the H⁺ and D⁺ positions in the center of a strong Н₂О…Н⁺…ОН₂ and D₂О…D⁺…ОD₂ hydrogen bond (HB) is used. Although we do not exclude the possibility of a symmetrical statistical distribution of H⁺ and D⁺ between two potential energy minima. The results of the spectroscopic analysis agree with the known data of the X-ray crystallographic analysis, showing that the crystals of I have a space symmetry group Pnma . At the same time, they disagree with the recently published data of theoretical calculations of the crystal structure of I (P2₁2₁2₁), these data showing that H⁺ notably shifts from the center of the strong HB towards an oxygen atom of one of the two water molecules.

Raman spectra of tin 2–hydroxy–3,6–di–tert–butyl–para–benzoquianone complexes L₂SnX₂ and LSnX₃ (L is 2–oxy–3,6–di–tert–butyl–para–benzoquianone; X = CH₃, C₂H₅, n–C₄H₉, and C₆H₅) are studied. A comparative analysis of the experimental and calculated spectra is carried out and the vibrational frequencies are conventionally assigned. A new tin(IV) complex based on 2,5–dihydroxy–3,6–di–tert–butyl–para–benzoquianone (L'H₂) containing phenyl substituents at the metal atom is synthesized. Absorption bands of the complexes are interpreted in the low-frequency range of the infrared spectrum that was not considered previously.

In this work, the N,N'-dipyridoxyl(1,2-diaminocyclohexane) [=H₂L] Schiff-base ligand and its square complex [Cu(L)] are newly synthesized and characterized by IR, mass spectroscopy, ¹H NMR, and elemental analysis. The ful optimization of geometries, the ¹H NMR chemical shifts (for the H₂L) and their vibrational frequencies are calculated using the density functional theory (DFT) method. The optimized geometry of the ligand is not planar, but each of two pyridine rings and the cyclohexane moiety are in the separate planes. The tetradentate-dianionic L^2– ligand occupies the four coordination positions of the square comlex in the N, N, O^–, O^– manner.

The effects of tetraphenylammonium (TPhA) on the equilibrium distribution of aluminosilicate oligomers in aqueous and methanolic alkaline aluminosilicate solutions were investigated using ²⁷Al NMR spectroscopy. Alkaline solutions containing both silicate and aluminate ions are of considerable research interest inter alia because of their involvement in the synthesis of zeolites. In the present work, we use ²⁷Al NMR to characterize alkaline aqueous and methanolic tetraphenylammonium (TPhA) aluminosilicate solutions with different Al/Si ratios. Tetraphenylammonium (TPhA) used as a cation template and no alkaline metals are used for preparation of aluminosilicate solutions. The distribution of aluminosilicate species was affected by the presence of the alcohol such as methanol and the method of mixing the silicate and aluminosilicate solutions. To understand the reaction between silicate and aluminate ions in this system, the evolutions of ²⁷Al NMR spectra with time are investigated.

The reaction of 1,4-diaminobutane with 2,2'-diformyl-6,6'-dimethoxy-diphenoxypropane in a mixed solvent of methanol and chloroform results in a new 17-membered macrocyclic Schiff base compound MeO-sal-pn-pn. The title compound is characterized by the elemental analysis (CHN), FT-IR, ¹H NMR spectroscopy, and powder X-ray diffraction. The crystal data are: M_r = 396.5, orthorhombic, P2₁2₁2₁, with unit cell parameters: a = 4.71769(3) Å, b = 19.1524(2) Å, c = 22.9418(2) Å, V = 2072.90(3) ų, and Z = 4.

Water–sodium dodecylsulfate–triethanolamine–1-pentanol–1,1,2,2-tetrafluorodibromoethane microemulsions of five compositions with different water–hydrocarbon ratios at a constant total surfactant+co-surfactant concentration of ~ 22 wt.% are obtained and their specific isobaric heat capacity and specific conductivity are measured. The temperature and concentration dependences of the mentioned properties of microemulsions are analyzed and interpreted from the standpoint of structural changes in the five-component system.

Thermodynamic characteristics are calculated for aqueous solutions of self-associated alkanolamines, which are capable of forming hydrogen bond networks. Correlations are found between the thermodynamic properties and structure of the solutions. The correlation between the entropy and enthalpy characteristics of water-alkanolamine systems with excess packing coefficients suggests that universal interactions determine the structural and energy properties of aqueous solutions of alkanolamines being studied. The structural and thermodynamic characteristics of aqueous solutions of self-associated alkanolamines are found to be similar to the previously obtained parameters of aqueous solutions of diols and oxyethylated glycols.

Crystallographic analysis is used to investigate the mutual packing arrangements of cluster groupings in the structures of KNa₂₃O₄(H₂O)₄₈[{Rh₄O₂(H₂O)₂}(H₂W₉O₃₃)₂] (I), (NH₄)₂[H₃Mo₅₇V₆(NO)₆O₁₈₃(H₂O)₁₈]·53H₂O (II), and Na₆Sr₂[W₁₂O₄₀(OH)₂]·24H₂O (III). It is found that all heavy cations in the clusters are located near the nodes of the single sublattice of the crystal. This arrangement ensures the coherence-assembly of the structural fragments since both the mutual orientation of the fragments and intervals between them are defined by the single cation sublattice.

Thermal transformations of the crystal structure and composition of the h-MoO₃ metastable phase with a transition to the α-МоО₃ stable modification are investigated. The study is performed using submicron phase-pure crystals exhibiting stability during their long storage in the air. By powder XRD, SEM, TGA, CHN, LMS, Raman and IR spectroscopy it is found: the composition of the deposited crystals is expressed by the general formula МоО₃·0.26H₂O; the impurity cationic composition consists of 1.8 wt.% of ammonia groups and a sum of 15 elements detected at a level of 10^–4 wt.%. Thermal treatment of the crystals to T = 350 °C in the air results in the removal of adsorbed and structural water, ОН^–, and NH₄⁺ groups with retaining the h-phase of hygroscopic МоО₃·0.08H₂O. The h-МоО ₃·0.08H₂O crystals obtained show instability during the storage and transform into the α-МоО₃ stable modification. At T = 380 °C the h → a phase transition occurs with the removal of coordinated water and texture transformations resulting in the formation of α-МоО ₃ hygroscopic crystals that at T = 650 °C acquire the platelet shape characteristic of the α-phase.