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1.
The heat capacity of copper hydride has been measured in the temperature range 2–60 and 60–250 K using two adiabatic calorimeters. Special procedure for the purification of CuH has been applied and a careful analysis of sample contamination has been performed. The experimental results have been extrapolated up to 300 K due to instability of the copper hydride at room temperature. From the temperature dependence of heat capacity the values of entropy S°(T), thermal part of enthalpy H°(T)−H°(0) and Gibbs function [−(G°(T)−H°(0))] have been calculated assuming S°(0)=0. The standard absolute entropy, standard entropy of formation from the elements and enthalpy of decomposition of copper hydride from the elements have been calculated and found to be 130.8 J K−1 mol−1 (H2), −85.1 J K−1 mol−1 (H2), −55.1 kJ mol−1 (H2), respectively. These new results gave the possibility of discussion on thermodynamic properties of copper hydride. Debye temperature has been for the first time determined experimentally.  相似文献   

2.
In the present work temperature dependences of heat capacity of carbosilane dendrimers with butyl terminal groups of the third and the fourth generations as well as of the fifth and the sixth generations have been determined first in the range from 6 to 340 K and between 6 and 600 K, respectively, by precision adiabatic vacuum and dynamic calorimetry. In the above temperature ranges the physical transformations have been detected and their thermodynamic characteristics have been estimated and analyzed. The experimental data were used to calculate standard thermodynamic functions, namely the heat capacity , enthalpy Ho(T) − Ho(0), entropy So(T) − So(0) and Gibbs function Go(T) − Ho(T), for the range from T → 0 to (340–600) K. Linear dependences of changing the corresponding thermodynamic functions of the dendrimers on their molecular weight and the number of butyl groups on an outer sphere have been determined.  相似文献   

3.
The heat capacities and enthalpy increments of strontium bismuth niobate SrBi2Nb2O9 (SBN) and strontium bismuth tantalate SrBi2Ta2O9 (SBT) were measured by the relaxation method (2–150 K), Calvet-type heat-conduction calorimetry (305–570 K) and drop calorimetry (773–1373 K). The temperature dependences of non-transition heat capacities in the form Cpm = 324.47 + 0.06371T − 5.0755 × 106/T2 J K−1 mol−1 (298–1400 K) and Cpm = 320.22 + 0.06451T − 4.7001 × 106/T2 J K−1 mol−1 (298–1400 K) were derived for SBN and SBT, respectively, by the least-squares method from the experimental data. Furthermore, the standard molar entropies at 298.15 K Sm°(SBN)=327.15±0.80 and Sm°(SBT)=339.23±0.72 J K−1 mol−1 were evaluated from the low-temperature heat capacity measurements.  相似文献   

4.
A 3D network [Cu(tmen)(tp)(H2O)2]n (1) (tmen = N,N,N′,N′-tetramethylethylenediamine; tp = terephthalate) and a 2D sheet [Cu(pyrazole)2(tp)]n (2), featuring 1D chains interwoven by hydrogen bonds, have been prepared and characterized by means of X-ray analyses and magnetic measurements. For 1, coordinative zigzag chains contain Cu(II) centers capped by the chelate ligand tmen, in which the tetragonal structure is elongated due to Jahn–Teller distortion. Coordinated water molecules are hydrogen-bonded to two free carboxylate oxygens of tp bridges, leading to the observed 3D structure. The use of the non-chelating capping ligand pyrazole produced the covalent-bonded 1D linear compound 2 with hydrogen bonds. A severe octahedral distortion of the Cu(II) center arises from a small bite angle (52.3(1)°) of two carboxylate oxygen atoms of tp, which are in turn hydrogen-bonded to the N–H groups of pyrazole ligands coordinated to Cu(II) atoms in neighboring chains. Magnetic data were fitted with the high-temperature series expansion for the Heisenberg chain spin Hamiltonian H = −JiSi · Si + 1 together with consideration of the molecular field approximation (zJ′). Both compounds interestingly exhibit ferromagnetic interactions with g = 2.17, J = 4.08 cm−1, zJ′ = −0.28 cm−1 for 1 and g = 2.09, J = 1.47 cm−1, zJ′ = −0.04 cm−1 for 2. By taking into account structural parameters of distances between Cu atoms, it is reasonably assigned that the ferromagnetic couplings (J > 0) in these systems originate from the hydrogen bonds. The spin density of the dx2-y2 orbital on a Cu(II) atom in a chain is propagated and induced over the dz2 orbital of another Cu(II) atom in an adjacent chain. This orbital orthogonality gives rise to such interactions. The negative zJ′ term suggests that the tp bridges communicate only tiny antiferromagnetic interactions.  相似文献   

5.
A novel dinuclear complex [Cu2(μ-L)4(HL)2] (1) was isolated from starting 2-pyridone (HL) via a resonance and a tautomeric transformation. Each copper centre is in a square-pyramidal coordination sphere, defined by two oxygen atoms (Cu–O4 1.978(5), Cu–O11 1.964(4) Å) and two nitrogen atoms (Cu–N2 2.003(5), Cu–N3 2.007(5) Å) of four bridging deprotonated pyridin-2-olates and an oxygen atom on the top from a neutral 2-pyridone (Cu–O2 2.227(5) Å), analogous to tetracarboxylate paddle-wheel complexes. Compound 1 was compared with mixed pyridin-2-olato/methanoato analogues [Cu2(μ-HCO2)2(μ-L)2(HL)2] · 2CH3CN (2) and [Cu2(μ-HCO2)2(μ-L)2(HL)2] (2a) (2a is an air stable form obtained from 2 outside mother-liquid). The EPR spectra of air stable 1 and 2a show three signals Hz1, H2 and Hz2, typical for the binuclear systems with spin S = 1, both revealing strong antiferromagnetism 2J = −334 (1) and −324 cm−1 (2a). Interestingly, only for 1 additional H1 signal at 100 mT is noticed (D(1) = 0.293 cm−1 <  = 0.320 cm−1 < D(2a) = 0.347 cm−1). On the other hand, several broad signals in the 100–450 mT region, only in the high temperature spectrum for 2a are observed. These results are in agreement with the magnetic susceptibility analysis.  相似文献   

6.
A metal-organic complex, which has the potential property of absorbing gases, [LaCu6(μ-OH)3(Gly)6im6](ClO4)6 was synthesized through the self-assembly of La3+, Cu2+, glycine (Gly) and imidazole (Im) in aqueous solution and characterized by IR, element analysis and powder XRD. The molar heat capacity, Cp,m, was measured from T = 80 to 390 K with an automated adiabatic calorimeter. The thermodynamic functions [HT − H298.15] and [ST − S298.15] were derived from the heat capacity data with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimetry (DSC).  相似文献   

7.
The effect of temperature on the extraction of FE(III) by dehydrated castor oil fatty acids (DCOFA) has been studied in the temperature range 283–313 K at 1.0M constant ionic strength (NaClO4). The temperature dependence of the conditional constant of extraction is given in the form: ln Kext=31.95 − 12800(1/T). Also, it was found that the average thermodynamic parameters, ΔH°ext, ΔG°ext, and ΔS°ext are 106.5 kJ/mole, 27.3 kJ/mole, and 0.3 kJ. mole−1.K−1, respectively. The extracted species in toluene solution were identified as FeR3.HR and Fe(OH)R2, where HR represents the fatty acid used.  相似文献   

8.
A “genome order index,” defined as S = a2 + c2 + t2 + g2, where a, c, t, and g are the nucleotide frequencies of A, C, T, and G, respectively, was used to suggest that there exist genome-specific constraints on nucleotide composition. We show that the “evidence” for constraint, S < 1/3, is in fact a mathematical property that is always true regardless of data. Moreover, we show that S is strictly equivalent to and derivable from the Shannon H-function and has no advantage over it.  相似文献   

9.
The structure of 1-chloronaphthalene, C10H7–Cl, at 293 K was investigated using the X-ray diffraction method. Monochromatic radiation MoK (λ=0.71069 Å) enabled the determination of the scattered radiation intensity between S0=4πsin 0/λ=0.430 Å−1 and Smax=14.311 Å−1. The interpretation of the results was carried out using the reduction method of Blum and Narten. Experimental distributions of X-ray scattered intensity were compared with theoretical results predicted for a proposed model of 1-chloronaphthalene molecule. The electron-density radial-distribution function was calculated and some intra- and intermolecular distances in liquid 1-chloronaphthalene were determined. X-ray structural analysis was applied to determine the packing coefficient of 1-chloronaphthalene molecules.  相似文献   

10.
We studied the isotope, pressure and doping effects on the pseudogap temperature T* by neutron spectroscopic experiments of the relaxation rate of crystal-field excitations in La1.96−xSrxHo0.04CuO4 (x = 0.11, 0.15, 0.20, 0.25) on the high-resolution time-of-flight spectrometer FOCUS at SINQ, PSI. We found clear evidence for the opening of a pseudogap in the underdoped regime at T*(x = 0.11) = (82.2 ± 1.2) K as well as in the overdoped and the heavily overdoped compounds at T*(x = 0.2) = (49.2 ± 0.7) K and at T*(x = 0.25) = (46.5 ± 0.5) K, respectively. Furthermore, we investigated the effect of oxygen isotope substitution on the pseudogap, the experiments revealed ΔT*(x = 0.11) = (21.3 ± 5.2) K and ΔT*(x = 0.2) = (4.5 ± 1.3) K. The application of hydrostatic pressure (0.8 and 1.2 GPa) on the optimally doped compound (x = 0.15) results in a downward shift of dT*/dp = (−5.9 ± 1.6) K/GPa.  相似文献   

11.
Two novel hydrogen maleato (HL) bridged Cu(II) complexes 1[Cu(phen)Cl(HL)2/2] 1 and 1[Cu(phen)(NO3)(HL)2/2] 2 were obtained from reactions of 1,10-phenanthroline, maleic acid with CuCl2·2H2O and Cu(NO3)2·3H2O, respectively, in CH3OH/H2O (1:1 v/v) at pH=2.0 and the crystal structures were determined by single crystal X-ray diffraction methods. Both complexes crystallize isostructurally in the monoclinic space group P21/n with cell dimensions: 1 a=8.639(2) Å, b=15.614(3) Å, c=11.326(2) Å, β=94.67(3)°, Z=4, Dcalc=1.720 g/cm3 and 2 a=8.544(1) Å, b=15.517(2) Å, c=12.160(1) Å, β=90.84(8)°, Z=4, Dcalc=1.734 g/cm3. In both complexes, the square pyramidally coordinated Cu atoms are bridged by hydrogen maleato ligands into 1D chains with the coordinating phen ligands parallel on one side. Interdigitation of the chelating phen ligands of two neighbouring chains via π–π stacking interactions forms supramolecular double chains, which are then arranged in the crystal structures according to pseudo 1D close packing patterns. Both complexes exhibit similar paramagnetic behavior obeying Curie–Weiss laws χm(T−θ)=0.414 cm3 mol−1 K with the Weiss constants θ=−1.45, −1.0 K for 1 and 2, respectively.  相似文献   

12.
A coordination polymer was synthesized by the reaction of CoCl2 with 1,2,4-triazole-5-one (TO) and charaterized by means of IR and TG–DTG. Single-crystal structure analysis showed that the complex crystallized in the monoclinic space group C2/c: a = 23.105(9) Å, b = 3.5683(2) Å, c = 13.589(6) Å,  = 90°, β = 124.038(4)°, γ = 90°, V = 928.4(7) Å3, Z = 4. The standard molar enthalpy of formation of the complex was determined to be (−1034.28 ± 0.95) kJ mol−1.  相似文献   

13.
The heat capacities of NaNO3 and KNO3 were determined from 350 to 800 K by differential scanning calorimetry. Solid-solid transitions and melting were observed at 550 and 583 K for NaNO3 and 406 and 612 K for KNO3, respectively. The entropies associated with the solid-solid transitions were measured to be (8.43± 0.25) J K−1 mole−1 for NaNO3 and (13.8±0.4) J K−1 mole−1 for KNO3. At 298.15 K the values of C0P S0P, {H0(T)-H0(0)}/T and -{G0(T)-H0(0)}/T, respectively, are 91.94, 116.3, 57.73, and 58.55 J K−1 mole−1 for NaNO3 and 95.39, 133.0, 62.93, and 70.02 J K−1 mole−1 for KNO3. Values for S0T, {H0(T)-H0(0)}/T, and -{G0(T)-H0(0)}/T were calculated and tabulated from 15 to 800 K for NaNO3 and KNO3.  相似文献   

14.
The oxygen permeation properties of mixed-conducting ceramics SrFeCo0.5O3−δ (SFCO), Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCFO), La0.2Sr0.8Co0.8Fe0.2O3−δ (LSCFO) and Ba0.95Ca0.05Co0.8Fe0.2O3−δ (BCCFO) were studied by thermogravimetric method in the temperature range 600–900 °C. The results show that the oxygen adsorption rate constants ka of all material are larger than oxygen desorption rate constants kd and both ka and kd are not strongly dependent on temperature in the studied temperature range. The oxygen vacancy contents δ(N2) and δ(O2) in nitrogen and oxygen and their difference Δδ = δ(N2) − δ(O2) play an important role in determining the temperature behavior of oxygen permeation flux JO2.  相似文献   

15.
With a hydrothermal technique, a layered titanium phosphate with the formula Ti2(H2PO4)(HPO4)(PO4)2 · 0.5C6N2H16 (denoted TP-J2) has been prepared by treating the Ti/H3PO4/H2O/1-methylpiperazine system directly. The as-synthesized products were characterized by powder X-ray diffraction, CP-MAS solid-state 31P NMR spectroscopy, thermogravimetric and differential thermal analyses (TG-DTA). The structure was solved by single-crystal X-ray diffraction analysis and it presents an extended γ-phase intercalated with organic amine. Crystal data: triclinic, , a = 8.106 (2) Å, b = 8.197 (2) Å, c = 11.658 (2) Å.  = 78.32 (3)°, β = 80.85 (3)°, γ = 77.90 (3)°, Z = 2. Additionally, the intercalation behavior of TP-J2 with n-alkyl monoamine (n = 2, 3, 4, 6, 8, 10 and 12) was investigated. Owing to the strong brønsted base, N,N′-dimethylpiperazine, resides in the interlayer, it presented unusual features of TP-J2 in contrast with that of γ-Tip.  相似文献   

16.
Effects of sintering atmospheres on properties of SrCo0.4Fe0.5Zr0.1O3−δ mixed-conducting membranes were in detail studied in terms of sintering behavior, electrical conductivity and oxygen permeability. The sintering atmospheres were 100% N2, 79% N2–21% O2, 60% N2–40% O2, 40% N2–60% O2, 20% N2–80% O2 and 100% O2 (in vol.%), and the prepared membranes were correspondingly denoted as S-0, S-21, S-40, S-60, S-80 and S-100, respectively. It was found that the properties of membranes were strongly dependent on the sintering atmosphere. As the oxygen partial pressure in the sintering atmosphere (PO2) increased, sintering ability, electrical conductivity and oxygen permeability decreased at first, which was in the order of S-0 > S-21 > S-40. However, as PO2 increased further, sintering ability, electrical conductivity and oxygen permeability increased gradually: S-40 < S-60 < S-80 < S-100. And the S-100 membrane had the best sintering ability, electrical conductivity and oxygen permeability in all membranes.  相似文献   

17.
The MutT pyrophosphohydrolase from E. coli (129 residues) catalyzes the hydrolysis of nucleoside triphosphates (NTP), including 8-oxo-dGTP, by substitution at Pβ, to yield NMP and pyrophosphate. The product, 8-oxo-dGMP is an unusually tight binding, slowly exchanging inhibitor with a KD=52 nM, (ΔG°=−9.8 kcal/mol) which is 6.1 kcal/mol tighter than the binding of dGMP (ΔG°=−3.7 kcal/mol). The higher affinity for 8-oxo-dGMP results from a more favorable ΔHbinding (−32 kcal/mol) despite an unfavorable −TΔS°binding (+22 kcal/mol). The solution structure of the MutT–Mg2+-8-oxo-dGMP complex shows a narrowed, hydrophobic nucleotide-binding cleft with Asn-119 and Arg-78 among the few polar residues. The N119A, N119D, R78K and R78A single mutations, and the R78K+N119A double mutant all showed largely intact active sites, on the basis of small changes in the kinetic parameters of dGTP hydrolysis and in 1H–15N HSQC spectra. However, the N119A mutation profoundly weakened the active site binding of 8-oxo-dGMP by 4.3 kcal/mol (1650-fold). The N119D mutation also weakened 8-oxo-dGMP binding but only by 2.1 kcal/mol (37-fold), suggesting that Asn-119 functioned both as a hydrogen bond donor to C8=O, and a hydrogen bond acceptor from N7H of 8-oxo-dGMP, while aspartate at position −119 functioned as an acceptor of a single hydrogen bond. Much smaller weakening effects (0.3–0.4 kcal/mol) on the binding of dGMP and dAMP were found, indicating specific hydrogen bonding of Asn-119 to 8-oxo-dGMP. While formation of the wild type MutT–Mg2+-8-oxo-dGMP complex slowed the backbone NH exchange rates of 45 residues distributed throughout the protein, the same complex of the N119A mutant slowed the exchange rates of only 11 residues at or near the active site, indicating an increase in conformational flexibility of the N119A mutant. The R78K and R78A mutations weakened the binding of 8-oxo-dGMP by 1.7 and 1.1 kcal/mol, respectively, indicating a lesser role of Arg-78 than of Asn-119 in the selective binding of 8-oxo-dGMP, likely donating a single hydrogen bond to its C6=O. The R78K+N119A double mutant weakened the binding of 8-oxo-dGMP (KIslope=3.1 mM) by 6.5±0.2 kcal/mol which overlaps, within error with the sum of the effects of the two single mutants (6.0±0.3 kcal/mol). Such additive effects of the two single mutants in the double mutant are most simply explained by the independent functioning of Asn-119 and Arg-78 in the binding of 8-oxo-dGMP. Independent functioning of these two residues in nucleotide binding is consistent with their locations in the MutT–Mg2+-8-oxo-dGMP complex, on opposite sides of the active site cleft, with a distance of 8.4±0.5 Å between their side chain nitrogens.  相似文献   

18.
The dissociative excitation reaction of BrCN induced by the products of the electron cyclotron resonance (ECR) plasma flow of He was studied based on the electrostatic-probe measurements and on the optical emission spectra of the B2Σ+ − X2Σ+ transition of CN radicals. The partial pressures of He and BrCN were 3 and 1 mTorr, respectively, and the partial pressure of H2O, PH2O, was in the range of 0.0–0.6 mTorr. The electron density, ne, showed a negative dependence on PH2O as (2.63 ± 0.13) × 1012 − (0.23 ± 0.10) × 1012 m−3, and the electron temperature, Te, a positive dependence, (2.38 ± 0.36) − (4.51 ± 0.15) eV. The CN(B2Σ+ − X2Σ+) emission intensity showed a negative dependence on PH2O. Based on a kinetic analysis of these PH2O dependencies, the decomposition of BrCN does not proceed via electron impact; instead, decomposition proceeds via the processes involving He+ and/or He metastable atoms.  相似文献   

19.
Physico-chemical properties of the binary system NaHSO4–KHSO4 were studied by calorimetry and conductivity. The enthalpy of mixing has been measured at 505 K in the full composition range and the phase diagram calculated. The phase diagram has also been constructed from phase transition temperatures obtained by conductivity for 10 different compositions and by differential thermal analysis. The phase diagram is of the simple eutectic type, where the eutectic is found to have the composition X(KHSO4) = 0.44 (melting point ≈ 406 K). The conductivities in the liquid region have been fitted to polynomials of the form κ(X) = A(X) + B(X)(T − Tm) + C(X)(T − Tm)2, where Tm is the intermediate temperature of the measured temperature range and X, the mole fraction of KHSO4. The possible role of this binary system as a catalyst solvent is also discussed.  相似文献   

20.
Recent measurements of Rayleigh scattering employing neutron capture γ-rays are presented. Experimental conditions are achieved such that the Rayleigh contribution is dominant and much larger than the other competing coherent processes. A detailed comparison with the modified relativistic form factor (MRFF) approximation is made and it is concluded that the latter overestimates the cross-section by 3–4%. New calculations of S, the incoherent scattering function, are presented in the relativistic treatment of Ribberfors and Berggren, using multiconfiguration Dirac–Fock relativistic wavefunctions. Tables of S, for Z=1–110, are shown on a momentum transfer mesh identical to previous non-relativistic calculations. S has been calculated at a representative angle θ=60° and energies compatible with the presentation mesh. For other scattering angles, the values presented in the tables are accurate to within 1–2% for momentum transfers larger than 0.1 Å−1. In the region below 0.1 Å−1 the accuracy worsens with decreasing momentum transfer, reaching 6% at 0.01 Å−1 and 10% at 0.005 Å−1. The same multiconfiguration wave functions were used to evaluate new MRFFs. The new elastic scattering cross sections differ by 3–6% compared with calculations based on single configuration wave functions.  相似文献   

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