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1.
The densities, viscosities and refractive indices of N,N /-ethylene-bis(salicylideneiminato)-diaquochromium(III) chloride, [Cr(salen)(H2O)2]Cl, in aqueous dimethylsulfoxide (DMSO) with different mass fractions (w 2 = 0.20, 0.40, 0.60, 0.80 and 1.00) of DMSO were determined at 298.15, 308.15 and 318.15 K under atmospheric pressure. From measured densities, viscosities and refractive indices the apparent molar volumes (V φ ), standard partial molar volume (V φ 0 ), the slope (S V * ), standard isobaric partial molar expansibility (φ E 0 ) and its temperature dependence (?φ E 0 /?T) p , the viscosity B-coefficient, its temperature dependence (?B/?T), solvation number (S n ) and apparent molar refractivity (R D φ ), etc., were calculated and discussed on the basis of ion–ion and ion–solvent interactions. These results revealed that the solutions are characterized by ion–solvent interactions rather than by ion–ion interactions and the complex behaves as a long range structure maker. Thermodynamics of viscous flow was discussed in terms of transition state theory.  相似文献   

2.
Structural parameters and vibrational frequencies of the clusters (Td)–Nb4O10, (C3v)-TaNb3O10, (D2d)-Nb4O 10 , and (Cs)-TaNb3O 10 were calculated. According to the (U)DFT/SDD calculations with BLYP, B3LYP, and PBE0 functionals magnetization of the anion (D2d)-Nb4O 10 is distributed equally among four niobium atoms. In the anion (Cs)-TaNb3O 10 unpaired electron presumably occupies niobium atoms. The distinction in contributions from Nb atoms in the magnetization of the tantalum-containing cluster grows with the exchange component of the DFT functional in the series of functionals BLYP < B3LYP < PBE0 < UHF.  相似文献   

3.
A powder of deuterated rubidium diselenatouranylate dihydrate Rb2UO2(SeO4)2 · 2D2O has been studied by neutron diffraction. The compound is orthorhombic, space group Pna21, with the following unit cell parameters: a = 13.654(2) Å, b = 11.863(2) Å, c = 7.625(1) Å, Z = 4, R F = 3.77, R I = 6.12, and χ2 = 2.21. Basic structure units are [UO2(SeO4)2 · D2O]2? layers belonging to the AB 2 2 M1 crystal-chemical group (A = UO 2 2+ , B2 = SeO 4 2? , M1 = D2O) of uranyl complexes. The hydrogen atoms if the water molecules involved in the layer form intralayer hydrogen bonds with the terminal oxygen atoms of selenate ions. The outer-sphere water molecules are coordinated to the rubidium ions and are involved in hydrogen bonding with oxygen atoms of neighboring [UO2(SeO4)2 · D2O]2? layers.  相似文献   

4.
By means of the formula \(e^{ - ((r^{XH} - r_0^{XH} )/b^{XHX} )^{5/3} } + e^{ - ((r^{YH} - r_0^{YH} )/b^{YHY} )^{5/3} } = 1\) that characterizes the correlation between the parameters of XH?Y linear fragments (r 0 XH , r 0 YH are the bond lengths in free molecules, b XHX, b YHY are the dimensional coefficients) r XX(r XH) and r XY(r YH) dependences are obtained. Given the length of a hydrogen bridge formed by O, N, and F atoms, they enable us to find the proton position in the bridge. The definition “a quasi-symmetric hydrogen bond,” based on the invariance of the r XX distance when the proton shifts by 0.1 Å, is established to be applicable to OHO, FHF, NHN, and ClHCl fragments. It is shown that the hydrogen bridge length remains almost constant (exceeds the minimum length by no more than 0.1 Å) if its bond orders are above 0.1. Here the displacement of the central proton can reach 0.2–0.3 Å.  相似文献   

5.
The applications of the Sand equation in potentiometry of electrode and membrane systems for precise measurements of the transition time (τ) have been determined. An approach was suggested for choosing the diffusion coefficient of electrolyte (D) in the case when the concentration changes from its value in the agitated solution (where D = Db) to the nearly zero value at the surface (D = D0 corresponds to an infinitely dilute solution), Db and D0 being substantially different. The Nernst–Planck–Poisson nonstationary equations were numerically solved in a one-dimensional system including an ion-exchange membrane and two adjacent diffusion layers (for the electrode–solution system, the result is a particular case). An effective value Def was found, whose substitution in the Sand equation gave τ identical to that obtained by numerical solution. The neglect of the concentration dependence D(с) can lead to a nonadequate determination of the ion transport numbers in the membrane.  相似文献   

6.
The geometric parameters, normal vibration frequencies, and thermochemical characteristics of the ions present in vapor over sodium fluoride, Na2F+, Na3F 2 + , NaF 2 ? , and Na2F 3 ? , were calculated ab initio by the Hartree-Fock method and taking into account electron correlation. The main equilibrium configuration of all ions was found to be the linear configuration of D h symmetry. Pentaatomic ions could also exist as two isomers, planar cyclic of C 2v symmetry and bipyramidal of D 3h symmetry. Their energies were higher than that of the D h isomers, and their contents in vapor were negligibly low. The energies and enthalpies of dissociation of the ions with the elimination of the NaF molecule were calculated. The enthalpies of formation of the ions were obtained.  相似文献   

7.
A new compound, (dibenzo-18-crown-6)ammonium bromide tetrahydrofuran solvate [NH4(Db18C6)]+ · Br? · THF (I), is synthesized and studied by X-ray diffraction analysis. The crystals of compound I are triclinic: a = 8.848 Å, b = 9.696 Å, c = 16.023 Å, α = 73.75°, β = 86.93°, γ = 78.06°, Z = 2, space group P \(\bar 1\). The structure of compound I is solved by a direct method and refined by full-matrix least squares in the anisotropic approximation to R = 0.095 by 5624 independent reflections (CAD-4 automated diffractometer, γMoK α). The Db18C6 molecule in structure I has a butterfly conformation with approximate symmetry C 2v . The NH 4 + cation where three disordered H atoms form hydrogen bonds with all six O atoms of the Db18C6 molecule is situated in the center of the cavity of the eighteen-membered macrocycle of the Db18C6 molecule. One ordered H atom of the NH 4 + cation forms a strong hydrogen bond with the Br? anion.  相似文献   

8.
The paper presents the results of a theoretical study of the dynamics of nonadiabatic transitions between the ion-pair states E0 g + and D0 u + of the I2 molecule induced by collisions with the I2 molecule in the ground electronic state X0 g + . The potential energy surfaces and diabatic coupling matrix elements of electronic states were obtained using a model based on the diatomics-in-molecule approximation. Special perturbation theory for intermolecular interaction was used to show that the large transition dipole moment between the E0 g + and D0 u + states caused the appearance of additional long-range corrections, an electrostatic dipole-quadrupole correction to the diabatic coupling matrix elements and induction dipole-dipole correction to the potential energy surface. The influence of these corrections on nonadiabatic dynamics was studied at the level of the semiclassical approximation. The electrostatic correction was found to sharply increase the contribution of resonance (accompanied by minimum kinetic energy changes) vibronic transitions at large distances between the colliding molecules. The induction correction had the opposite effect because of the high transition probability at short distances. The results obtained were in qualitative agreement with experimental data. The conclusion was drawn that obtaining quantitative agreement required a more balanced inclusion of interactions at short and long distances.  相似文献   

9.
The effect of γ-irradiation on thermophoto-emf of hot carriers in n-Cd0.94Hg0.06Тe and р-Cd0.82Hg0.18Тe single crystals has been studied. The dependence of the pattern of |Utp| curves on E in the test CdxHg1—хTe crystals is explained by the change in the degree of spatial heterogeneity of these crystals resulted from the accumulation of point radiation defects at relatively low Dγ and their spatial ordering caused by the introduction of a large number of point radiation defects at higher exposures. The proposed mechanism for the effect of γ-irradiation on the thermophoto-emf of hot carriers explains satisfactorily the dependence of |Utp| kinetics on radiation dose, sample composition, temperature, and field strength.  相似文献   

10.
The electronic and geometric structures, energy stabilities, normal mode frequencies, and spin density distributions (in radicals) of different stepwise-chlorinated aluminum clusters Al13Cl n ? (n = 1–9) are calculated within the B3LYP approximation of the density functional theory using 6-31G* and 6-311+G* basis sets. The results are compared with analogous computation data on hydrides Al13H n ? (n = 1–12) obtained at the same level. The general qualitative pattern for related series of hydrides, chlorides, and iodides (as well as fluorides and bromides) turns out to be similar in many respects. For all Al13X n ? clusters with different electronegative substituents X, there is a set of a considerable number of low-lying closely spaced inner isomers (with a centered icosahedral cage), marquee isomers, and outer isomers (capped). The effects found by calculations in centered icosahedral isomers—localization of spin density on the trans-Al* atom in radical anions and its associated trans addition rule for an even substituent and the zigzag (odd-even) dependence of the energies D n (X) of successive addition of substituents X to the metal cage on n described in the framework of the molecular model of the valence states of the Al 13 ? superatom—should also be shared by many Al13X n ? series with different X’s. The differences between hydrides Al13H n ? and chlorides Al13Cl n ? of the same type are quantitative. For the hydrides, inner isomers are preferable in the first half of the series (n = 1–6); and in the second half (n = 7–12), outer isomers are more favorable. For the chlorides, icosahedral isomers are preferable only at the very beginning of the series. In the other cases, nonicosahedral structures are most favorable, for which the situation becomes very complicated due to the large number of position isomers and the aforementioned simple rules found for centered icosahedral structures are fulfilled to a considerably less extent or not at all.  相似文献   

11.
A solvate [Cu(CF3COCHCOCH3)2(CH3COCH3)] has been synthesized and characterized for the first time. According to X-ray structural data (diffractometer X8 APEX BRUKER, radiation MoK α, T = 150 K), it crystallizes in the monoclinic crystal system, space group P21/c, a = 8.9940(4) Å, b = 22.3966(11) Å, c = 8.1884(3) Å, β = 92.705(2)°, V = 1647.59(12) Å3, Z = 4, d calc = 1.725 g/cm3, final R = 0.0272. The structure is molecular. In the equatorial plane the atom Cu(II) is surrounded with four oxygen atoms of two chelating ligands (CF3COCHCOCH3)?; Cu-O distances 1.927–1.937 Å, O-Cu-O angles 86.18–93.30° and 170.18–175.67°. Square coordination of Cu is complemented to the square-pyramidal one by the oxygen atom of an acetone molecule behaving as an axial ligand; Cu-Oacetone 2.342 Å, O-Cu-Oacetone 89.66–100.11°. In the studied compound disorder of one of the chelate ligands implies the co-existance of the molecules in the cis- and trans-configuration in the crystal under ratio 54.6:45.4. In air the solvate rapidly degrades losing acetone, while in a sealed vessel melts around 313 K. Temperature dependence of equilibrium vapor pressure of acetone over the complex was measured with the static spoon gauge technique, thermodynamic characteristics of its dissociation process being derived: [Cu(CF3COCHCOCH3)2(CH3COCH3)]s = [Cu(CF3COCHCOCH3)2]s + CH3COCH3g, ΔH av 0 = 49.6(3) kJ/mol, ΔS av 0 = 152(1) J/(mol K), ΔG av 0 = 4.30(2) kJ/mol.  相似文献   

12.
The formulas for calculation of the number of atoms in nanoparticles with symmetry group D 6h are reported. The numbers of atoms are determined by six structurally invariant numbers and the “quantum number” of the group order n. Eight classes of nanostructures with symmetry group D 6h are revealed: C ? + 12z , where z = 0, 1, 2, …, and C ? is C 2, C 6, C 8, or C 14. The sum rule for the coordination numbers of all atoms of subshells related to symmetry elements is established. Two-dimensional nanoparticles are considered.  相似文献   

13.
The distribution of NO molecules desorbed from a Pt(111) surface due to valence electron excitation over rotational energy levels N(J) is analyzed using a simple impulse-induced model. A linear dependence is found between lnN(J) and (Er)1/2, where Er is the rotational energy of the desorbed molecules. The lifetime of the excited state and the critical time of residence in the excited state estimated using this dependence are found to be close to one another (~10?15 s). The frequency and amplitude of the tilting vibrations of the adsorbed molecules in the excited state are estimated.  相似文献   

14.
The structural features of 38 mononuclear d 2-Re(V) octahedral monooxo complexes (I–XXXVIII) with oxygen atoms of bidentate-chelating (O, P) ligands (L n ) are considered. The atoms O(L n ) are mostly in trans positions to O(oxo) ligands. In three compounds of general formula [ReO(Lmono)(L n )2] (XXXVI–XXXVIII), the O atoms of two L n ligands occupy both trans and cis positions to oxo ligands. In one complex, namely, in [ReO(L n )(L tri 11 )], n = 3 (XXXV), the atom O(L3) is in the cis position to the oxo ligand; the trans position to O(oxo) is occupied by the atom O(L tri 11 ).  相似文献   

15.
The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6–370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions Cp°(T), H°(T) ? H°(0), S°(T) ? S°(0), and G°(T) ? H°(0) are calculated from the obtained experimental data for the region of Т → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at Т = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.  相似文献   

16.
The work proposes a method to predict changes in the heat capacity of the liquid—vapor phase transition Δ l g Ср 0 (298.2) based on modified Randi? indices for alkanes and acyclic oxygen-containing compounds: alcohols, aldehydes, ketones, ethers, and esters. Based on the obtained Δ l g Ср 0 (298.2) values heat capacities in the liquid phase Cp liq 0 (298.2) are calculated for the compounds under study.  相似文献   

17.
Densities (ρ) and refractive indices (nD) of solutions of antiemetic drug metoclopramide (4-amino-5-chloro-N-(2-(diethylamino)ethyl)-2-methoxybenzamide hydrochloride hydrate) in methanolwater and ethanol-water mixtures of different compositions were measured at 30°C. Apparent molar volume (φv) of the drug was calculated from density data and partial molar volumes (φv0) were determined from Massons relation. Concentration dependence of nD has been studied to determine refractive indices of solution at infinite dilution (nD0). Results have been interpreted in terms of solute-solvent interactions.  相似文献   

18.
Tellurite of the composition Li2CeTeO5 is synthesized by solid-phase method from cerium(IV) and tellurium(IV) oxides and lithium carbonate. The type of syngony, the unit cell parameters, and the compound’s X-ray and pycnometry densities are determined via X-ray diffraction analysis. The isobaric heat capacity of lithium–cerium tellurite is studied by means of dynamic calorimetry in the temperature range of 298.15–673 K; the results serve as the basis for deriving C p ° ~ f(T) dependency equations and determining the compound’s thermodynamic functions. λ-shaped anomalous effects, due probably to Type II phase transitions, are found on the C p ° ~ f(T) dependence.  相似文献   

19.
A hydrated salt of 2.2.2-cryptand and sulfuric acid [H2(Crypt-222)]2+ · SO 4 2? · 4H2O(I) was prepared and studied by X-ray diffraction. The structure of I (space group C2/c, a = 22.823, b = 9.610, c = 26.150 Å, β = 107.71°, Z = 8) was solved by the direct method and refined by full-matrix least-squares in the anisotropic approximation to R = 0.056 for 4032 independent reflections (CAD4 automated diffractometer, λMoK α radiation). In the structure of I, the 2.2.2-cryptand dication (with approximate C 2 symmetry) has a rare exo-exo conformation where two H atoms at two N atoms are directed away from the cavity. The tetrahedral SO 4 2? anion is disordered over two orientations. In two water molecules, the H atoms are disordered, while in the other two water molecules all atoms are disordered. The crystal structure of I has an extensive three-dimensional system of ion-ion (intermolecular) hydrogen bonds in which infinite chains of alternating SO 4 2? anions and 2.2.2-dications can be distinguished.  相似文献   

20.
The saturated vapors of ErCl3 and YbCl3 were studied in a simultaneous electron diffraction and mass spectrometric experiment at 1165 K and 1170 K, respectively. In the vapors of these compounds, we found up to 3 mol.% dimers along with the monomers. The parameters of the r g effective configuration of the monomer molecules were determined. For ErCl3 and YbCl3, the internuclear distances r g(Ln-Cl) were 2.436(5) Å and 2.416(5) Å, and the bond angles ∠g(Cl-Ln-Cl) were 117.0(10)° and 117.2(10)°, respectively. The equilibrium configurations and vibration frequencies of the monomer and dimer molecules were calculated by the HF, B3LYP, and MP2 methods using the combination of the ECPD energy-consistent quasirelativistic core potential, including 4f electrons [Kr4d 104f n ], and the contracted [5s4p3d] valence basis set for Er and Yb atoms and the MIDIX [4s3p1d] basis set for Cl atoms. The parameters of the effective r g configuration of the monomer molecules corresponding to the temperature of the experiment were calculated. The difference between the calculated equilibrium r e(Ln-Cl) and temperature-averaged r g(Ln-Cl) distances was found to be 0.001–0.002 Å and did not exceed the error of the r g(Ln-Cl) parameter determined in the electron diffraction experiment. The experimental parameters of the r g structure were shown to be consistent with the idea about the planar equilibrium geometrical configuration of ErCl3 and YbCl3 molecules.  相似文献   

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