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1.
B3LYP method with the LANL2DZ basis for tin and aug-cc-pVDZ basis for carbon and hydrogen were used to obtain the equilibrium geometry of the main (with a positive charge on the tin) isomers in the C4H11Sn+ system and the transition states at their interconversion. As in the case of silicon and germanium, the cations of lighter elements of the 14th group, the most stable isomer is shown to be the tertiary ion, however, the energy of its complexes with ethane and propane is higher only by several kJ mol−1. Nevertheless, the formation of these complexes from the tertiary ion requires overcoming a rather high barrier (293 and 272 kJ mol−1, respectively). The barrier for isomerization of the secondary ion in the ethane complex is somewhat lower (222 kJ mol−1), but still is significantly greater than the energy gained at the appearance of the nucleogenic ion. The most probable transformation pathways of the nucleogenic stannylium ions are the formation of complexes with ethylene, which requires overcoming barriers of 130 and 117 kJ mol−1 for the tertiary and secondary ions, respectively.  相似文献   

2.
The two complexes, [RE(Gly)4(Im)(H2O)](ClO4)3(s)(RE = Eu, Sm), have been synthesized and characterized. The standard molar enthalpies of reaction for the following reactions, RECl3·6H2O(s)+4Gly(s)+Im(s)+3NaClO4(s) = =[RE(Gly)4(Im)(H2O)](ClO4)3(s)+3NaCl(s)+5H2O(l), were determined by solution-reaction colorimetry. The standard molar enthalpies of formation of the two complexes at T = 298.15 K were derived as Δf H mΘ {Eu(Gly)4(Im)(H2O)}(ClO4)3(s)} = = −(3396.6±2.3) kJ mol−1 and Δf H mΘ {Sm(Gly)4(Im)(H2O)}(ClO4)3(s)} = −(3472.7±2.3) kJ mol−1, respectively.  相似文献   

3.
Differential scanning calorimetry data at different heating rates (5, 10, 15 and 20 °C min−1) of Se70Te15In15 chalcogenide glass is reported and discussed. The crystallization mechanism is explained in terms of recent analyses developed for use under non-isothermal conditions. The value of Avrami exponent (n) indicates that the glassy Se70Te15In15 alloy has three-dimensional growth. The average values of the activation energy for glass transition, E g, and crystallization process, E c, are (154.16 ± 4.1) kJ mol−1 and (98.81 ± 18.1) kJ mol−1, respectively. The ease of glass formation has also been studied. The reduced glass transition temperature (T rg), Hruby’ parameter (K gl) and fragility index (F i) indicate that the prepared glass is obtained from a strong glass forming liquid.  相似文献   

4.
Two new heteropolyoxovanadoborates (H2dap)2H6{(VO)12O6[B3O6(OH)]6(H2O)}·13H2O (1, dap = 1,2-diaminopropane) and {[Zn(dien)]2[Zn(dien)(H2O)]4(VO)12O6[B3O6(OH)]6(H2O)}2·15H2O (2, dien = diethylenetriamine) have been hydrothermally synthesized and structurally characterized. Both 1 and 2 contain {(VO)12O6[B3O6(OH)]6(H2O)} cluster (denoted on V12B18), which is constructed by a puckered B18O36(OH)6 ring sandwiched between two triangles of six alternating cis and trans edge-sharing vanadium atoms, and a central water molecule. 1 consists of discrete [V12B18]10− cluster anions with H2dap2+ as counterions, while 2 consists of discrete neutral {[Zn(dien)]2[Zn(dien)(H2O)]4[V12B18]} clusters, which are built from two types of zinc(II) complex fragments connecting with V12B18 cluster through two Zn-(μ 3-O)-B bonds. Interestingly, 2 is the only example of the V12B18 cluster decorated by two types of zinc(II) complex fragments.  相似文献   

5.
In the compound [Ni(Bptc)2(Bimb)2(H2O)2] (I), where H4Bptc is 3,3′,4,4′-biphenyltetracarboxylic acid; Bimb is 4,4′-bis(1-imidazolyl)biphenyl), Ni(II) has a distorted octahedral coordination geometry, which was bonded with two N atoms from two Bimb ligands, two O atoms from two H2Bptc2− ligands and two water O atoms. The crystal structure of compound I is stabilized by the π-π-stacking and hydrogen bonds interaction.  相似文献   

6.
The heat capacity and the enthalpy increments of strontium metaniobate SrNb2O6 were measured by the relaxation method (2-276 K), micro DSC calorimetry (260-320 K) and drop calorimetry (723-1472 K). Temperature dependence of the molar heat capacity in the form C pm=(200.47±5.51)+(0.02937±0.0760)T-(3.4728±0.3115)·106/T 2 J K−1 mol−1 (298-1500 K) was derived by the least-squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S m0 (298.15 K)=173.88±0.39 J K−1 mol−1 was evaluated from the low temperature heat capacity measurements. The standard enthalpy of formation Δf H 0 (298.15 K)=-2826.78 kJ mol−1 was derived from total energies obtained by full potential LAPW electronic structure calculations within density functional theory.  相似文献   

7.
Methane-intercalated fullerite (CH4)0.56C60 was obtained by low-temperature precipitation from solution. Methane transition from the gas phase to the octahedral void of fullerite is accompanied by a bathochromic shift of normal vibrational frequencies (by 19 and 8 cm−1 for ν3 and ν4, respectively). The methane 13C signal in the proton decoupling 13C NMR spectrum is observed as a singlet at δ−0.42. According to quantum chemical calculations using density functional theory, location of methane in the octahedral void of fullerite (C60)6 leads to a decrease in the total energy of fullerite by 4 kcal mol−1.  相似文献   

8.
The A1, O, AlO, A12O, Al2O2, WO2, and WO3, partial pressures in the vapor over Al2O3 in a tungsten Knudsen effusion cell between 2300 and 2600 K were derived from A1+, O+, AlO+, A12O+, Al2O2+, WO2+, and WO3+, ion intensities. The mass spectrometer was calibrated against the equilibrium constant of the WO3(g) = WO2(g) + O(g) reaction. Refined values of the ionization cross sections of AlO and A12O2 were used in the partial pressure calculations. The enthalpies of atomization of aluminum suboxides were determined to be Δat H o(AlO, g, 0) = 510.7 ± 3.3 kJ mol−1, Δat H o(Al2O, g, 0) = 1067.2 ± 6.9 kJ mol−1, and Δat H o(Al2O2, g, 0) = 1556.7 ± 9.9 kJ mol−1.  相似文献   

9.
The neutral dinuclear iron nitrosyl complex [Fe2(SC3H5N2)2(NO)4] (1) of the “g = 2.03” family with a ligand analogous to natural mercaptohistidine was synthesized by the metathesis reaction of the thiosulfate ligands in the [Fe2(S2O3)2(NO)4]2− anion with imidazolidine-2-thiolate ligands. The electrochemical determination of nitrogen oxide in solution showed that compound 1 has a lower NO-donor ability compared to the iron complexes with 1-methylimidazole-2-thiol and imidazole-2-thiol synthesized earlier. Study of the magnetic properties of polycrystals of 1 demonstrated that the effective magnetic moment at room temperature is ca. 2.45 μB and corresponds to a molecule containing a pair of the noninteracting spins S = 1/2. This is evidence that each iron coordination unit in complex 1 contains one unpaired electron, and the iron atom is in the low-spin state. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 28–34, January, 2007.  相似文献   

10.
Enthalpy of formation of the perovskite-related oxide BaCe0.9In0.1O2.95 has been determined at 298.15 K by solution calorimetry. Solution enthalpies of barium cerate doped with indium and mixture of BaCl2, CeCl3, InCl3 in ratio 1:0.9:0.1 have been measured in 1 M HCl with 0.1 M KI. The standard formation enthalpy of BaCe0.9In0.1O2.95 has been calculated as −1611.7±2.6 kJ mol−1. Room-temperature stability of this compound has been assessed in terms of parent binary oxides. The formation enthalpy of barium cerate doped by indium from the mixture of binary oxides is Δox H 0 (298.15 K)=−36.2±3.4 kJ mol−1.  相似文献   

11.
The geometrical and electronic structures of two isomers (1 and2) of the polyhedral boron nitride molecule, B12N12, have been calculated using the MNDO method. Structure1 having the form of a truncated octahedron is more energetically preferable (ΔH f 0=−128 kcal mol−1) than isomer2, which hasC 6v symmetry. The equilibrium geometries of the N6B6(CH2)6 isomers (3 and4), which simulate fragments of structure2, have been calculated. The stabilization mechanism of the N6 nitrogen cluster (hexaazabenzene) in polyhedral structures is discussed. The parameters calculated for molecules1 and2 have been correlated with the corresponding characteristics of their carbon analogs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1712–1714, October, 1993.  相似文献   

12.
2CaO·3B2O3·H2O which has non-linear optical (NLO) property was synthesized under hydrothermal condition and identified by XRD, FTIR and TG as well as by chemical analysis. The molar enthalpy of solution of 2CaO·3B2O3·H2O in HCl·54.572H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HCl·54.501H2O and of CaO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of CaO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5733.7±5.2) kJ mol−1 of 2CaO·3B2O3·H2O was obtained. Thermodynamic properties of this compound were also calculated by a group contribution method.  相似文献   

13.
The visible light irradiation of the [(η5-C6H7)Fe(η-C6H6)]+ cation (1) in acetonitrile resulted in the substitution of the benzene ligand to form the labile acetonitrile species [(η5-C6H7)Fe(MeCN)3]+ (2). The reaction of 1 with ButNC in MeCN produced the stable isonitrile complex [(η5-C6H7)Fe(ButNC)3]+ (3). The photochemical reaction of cation 1 with pentaphosphaferrocene Cp*Fe(η-cyclo-P5) afforded the triple-decker cation with the bridging pentaphospholyl ligand, [(η5-C6H7)Fe(μ-η:η-cyclo-P5)FeCp*]+ (4). The latter complex was also synthesized by the reaction of cation 2 with Cp*Fe(η-cyclo-P5). The structure of the complex [3]PF6 was established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2088–2091, November, 2007.  相似文献   

14.
The initiation of ethylene polymerization on L2MMe+ cations (M = Ge, Sn; L = alkoxy, alkyl, phenoxyiminate, β-diketonate) was studied by the PBE/TZ2P density functional method. It was found that ethylene insertion into the M—C bond of the L2MMe+ cations is energetically favorable (ΔG 0 = −7.6—−13.6 kcal mol−1). The calculated energy barriers to reactions lie in a wide range 39.8 to 75.6 kcal mol−1. The lowest energy barriers were obtained for tin cations bearing hexa- and heptafluoroacetylacetonate substituents. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1338–1347, July, 2008.  相似文献   

15.
Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO2 composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression method. The results show that the kinetic models for the decomposition process of PANI/ZrO2 composite and PANI are all D3, and the corresponding function is ƒ(α)=1.5(1−α)2/3[1−(1-α)1/3]−1. The correlated kinetic parameters are E a=112.7±9.2 kJ mol−1, lnA=13.9 and E a=81.8±5.6 kJ mol−1, lnA=8.8 for PANI/ZrO2 composite and PANI, respectively.  相似文献   

16.
Thermal internal energy gaps, ΔE s−t; enthalpy gaps, ΔH s−t; Gibbs free energy gaps, ΔD s−t, between singlet (s) and triplet (t) states of R2C4H2M (M = C, Si, and Ge) were calculated at B3LYP/6-311++G** level of theory. The ΔG s−t of R2C4H2C was increased in the order (in kcal/mol): R = −CH3 (−10.51) > −H (−9.59) > i-Pr (−9.51) > t-Bu (−8.98). While, the ΔG s−t of R2C4H2Si and R2C4H2Ge were increased in the order (in kcal/mol): −CH3 (17.01) > i-Pr (15.30) > −H (15.26) > t-Bu (14.35) and -H (22.79) > −CH3 (22.69) > i-Pr (21.66) > t-Bu (21.01), respectively.  相似文献   

17.
The reaction of a sulfur and oxygen-bridged 8-quinolinolato trinuclear molybdenum cluster [Mo3OS3(qn)3(H2O)3]+ (3; Hqn = 8-quinolinol) with equimolar amounts of acetylene carboxylic acid, 4-pentynoic acid, 5-hexynoic acid, acetic acid, and pimelic acid gave clusters having μ-carboxylato groups, [Mo3OS3(qn)3(H2O)(μ-HC≡CCOO)] (6), [Mo3OS3(qn)3(H2O)(μ-HC≡C(CH2)2COO)] (7), [Mo3OS3(qn)3(H2O)(μ-HC≡C(CH2)3COO)] (8), [Mo3OS3(qn)3(H2O)(μ-CH3COO)] (4), and [{Mo3OS3(qn)3(C2H5OH)}2(μ-C7H10O4)] (5), respectively. X-ray structural analyses, 1H NMR, and electronic spectra of these clusters made clear that each of the COO groups of the reagents bridges two Mo atoms in each cluster and that no adduct formation occurred at the sulfurs in the clusters. The reaction of 3 with a large excess-molar amount (50 times) of acetylene carboxylic acid gave [Mo3OS(μ3-SCH=C(COOH)S)(qn)3(H2O)(μ-HC≡CCOO)] (9) with two molecules of acetylene carboxylic acid, one acting as a carboxylato bridge and the other in adduct formation, as supported by the electronic and 1H NMR spectra. The corresponding aqua cluster [Mo3OS3(H2O)9]4+ (1), on the contrary, reacts with acetylene carboxylic acid to give adduct [Mo3OS(μ3-SCH=C(COOH)S)(H2O)9]4+ (2). Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.  相似文献   

18.
The Gibbs free energies of solvation (ΔG s) and the electronic structures of endohedral metallofullerenes M+@C60 (M+= Li+, K+) were calculated within the framework of the density functional theory and the polarizable continuum model. In water environment, the equilibrium position of K+ is at the center of the fullerene cavity whereas that of Li+ is shifted by 0.14 nm toward the fullerene cage. The Li+ cation is stabilized by interactions with both the fullerene and solvent. The equilibrium structures of both endohedral metallofullerenes are characterized by very close ΔG s values. In particular, the calculated ΔG s values for K+@C60 are in the range from −124 to −149 kJ mol−1 depending on the basis set and on the type of the density functional. Molecular dynamics simulations (TIP3P H2O, OPLS force field, water sphere of radius 1.9 nm) showed that the radial distribution functions of water density around C60 and M+@C60 are very similar, whereas orientations of water dipoles around the endohedral metallofullerenes resemble the hydration pattern of isolated metal ions.  相似文献   

19.
Osmotic coefficients and water activities for the Li2B4O7+LiCl+H2O system have been measured at T=273.15 K by the isopiestic method, using an improved apparatus. Two types of osmotic coefficients, φ S and φ E, were determined. φ S is based on the stoichiometric molalities of the solute Li2B4O7(aq), and φ E is based on equilibrium molalities from consideration of the equilibrium speciation into H3BO3,B(OH)4 and B3O3(OH)4. The stoichiometric equilibrium constants K m for the aqueous speciation reactions were estimated. Two types of representations of the osmotic coefficients for the Li2B4O7+LiCl+H2O system are presented with ion-interaction models based on Pitzer’s equations with minor modifications: model (I) represents the φ S data with six parameters based on considering the ion-interactions between three ionic species of Li+, Cl, and B4O72−, and model (II) for represents the φ E data based on considering the equilibrium speciation. The parameters of models (I) and (II) are presented. The standard deviations for the two models are 0.0152 and 0.0298, respectively. Model (I) was more satisfactory than model (II) for representing the isopiestic data.  相似文献   

20.
Heteropoly acid (HPA) H8(PW11TiO39)2xH2O (I) is synthesized by three different ways and studied by chemical analysis, potentiometric titration, mass-spectrometry, IR, 31P, 183W, and 17O NMR spectroscopy, thermogravimetry, and transmission electron microscopy. Anion I consists of two subparticles of the Keggin structure bridged by Ti-O-Ti. The dimeric anion exists in HPA aqueous solutions at [I] > 0.02 M. At pH > 0.6 it splits to a [PW11TiO40]5− monomer stable up to pH ∼ 6. When heated (150–400)°C, I splits into H3PW12O40 and, apparently, H3PW10Ti2O38 without phase separation. Thermolysis products are soluble and when dissolved in water turn again into I. Complete decomposition of I to oxides occurs at ∼450°C.  相似文献   

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