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1.
The enthalpies of solution of NaRb[B4O5(OH)4]·4H2O in approximately 1 mol dm−3 aqueous hydrochloric acid and of RbCl in aqueous (hydrochloric acid + boric acid + sodium chloride) were determined. From these results and the enthalpy of solution of H3BO3 in approximately 1 mol dm−3 HCl(aq) and of sodium chloride in aqueous (hydrochloric acid + boric acid), the standard molar enthalpy of formation of −(5128.02 ± 1.94) kJ mol−1 for NaRb[B4O5(OH)4]·4H2O was obtained from the standard molar enthalpies of formation of NaCl(s), RbCl(s), H3BO3(s) and H2O(l). The standard molar entropy of formation of NaRb[B4O5(OH)4]·4H2O was calculated from the Gibbs free energy of formation of NaRb[B4O5(OH)4]·4H2O computed from a group contribution method.  相似文献   

2.
A pure calcium borate Ca2[B2O4(OH)2]·0.5H2O has been synthesized under hydrothermal condition and characterized by XRD, FT-IR and TG as well as by chemical analysis. The molar enthalpy of solution of Ca2[B2O4(OH)2]·0.5H2O in HC1·54.582H2O was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in HC1·54.561H2O 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 −(3172.5 ± 2.5) kJ mol−1 of Ca2[B2O4(OH)2]·0.5H2O was obtained.  相似文献   

3.
A new magnesium borate MgO·3B2O3·3.5H2O has been synthesized by the method of phase transformation of double salt and characterized by XRD, IR and Raman spectroscopy as well as by TG. The structural formula of this compound was Mg[B6O9(OH)2]·2.5H2O. The enthalpy of solution of MgO·3B2O3·3.5H2O in approximately 1 mol dm−3 HCl was determined. With the incorporation of the standard molar enthalpies of formation of MgO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(5595.02±4.85) kJ mol−1 of MgO·3B2O33.5H2O was obtained. Thermodynamic properties of this compound was also calculated by group contribution method.  相似文献   

4.
A new magnesium borate, β-2MgO·3B2O3·17H2O, has been synthesized by the method of phase transformation of double salt and characterized by XRD, IR, and Raman spectroscopy as well as by TG. The structural formula of this compound was Mg[B3O3(OH)5]·6H2O. The enthalpy of solution of β-2MgO·3B2O3·17H2O in approximately 1 mol dm−3 HCl was determined. With the incorporation of the standard molar enthalpies of formation of MgO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(10256.39±4.93) kJ mol−1 of β-2MgO·3B2O3·17H2O was obtained. Thermodynamic properties of this compound was also calculated by group contribution method.  相似文献   

5.
A new magnesium borate Mg2[B2O4(OH)2]·H2O has been synthesized by the method of phase transformation of double salt at hydrothermal condition and characterized by XRD, IR, TG and DSC. The enthalpy of solution of Mg2[B2O4(OH)2]·H2O in 0.9764 mol L–1 HCl was determined. With the incorporation of the enthalpies of solution of H3BO3 in HCl (aq), of MgO in (HCl+H3BO3) (aq), and the standard molar enthalpies of formation of MgO(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of –(3185.78±1.91) kJ mol–1 of Mg2[B2O4(OH)2]·H2O was obtained.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

6.
Two pure strontium borates SrB2O4·4H2O and SrB2O4 have been synthesized and characterized by means of chemical analysis and XRD, FT-IR, DTA-TG techniques. The molar enthalpies of solution of SrB2O4·4H2O and SrB2O4 in 1 mol dm−3 HCl(aq) were measured to be −(9.92 ± 0.20) kJ mol−1 and −(81.27 ± 0.30) kJ mol−1, respectively. The molar enthalpy of solution of Sr(OH)2·8H2O in (HCl + H3BO3)(aq) were determined to be −(51.69 ± 0.15) kJ mol−1. With the use of the enthalpy of solution of H3BO3 in 1 mol dm−3 HCl(aq), and the standard molar enthalpies of formation for Sr(OH)2·8H2O(s), H3BO3(s), and H2O(l), the standard molar enthalpies of formation of −(3253.1 ± 1.7) kJ mol−1 for SrB2O4·4H2O, and of −(2038.4 ± 1.7) kJ mol−1 for SrB2O4 were obtained.  相似文献   

7.
Two solid-state coordination compounds of rare earth metals with glycin, [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O and [ErY(Gly)6(H2O)4](ClO4)6·5H2O were synthesized. The low-temperature heat capacities of the two coordination compounds were measured with an adiabatic calorimeter over the temperature range from 78 to 376 K. [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O melted at 342.90 K, while [ErY(Gly)6(H2O)4](ClO4)6·5H2O melted at 328.79 K. The molar enthalpy and entropy of fusion for the two coordination compounds were determined to be 18.48 kJ mol−1 and 53.9 J K−1 mol−1 for [Gd4/3Y2/3(Gly)6(H2O)4](ClO4)6·5H2O, 1.82 kJ mol−1 and 5.5 J K−1 mol−1 for [ErY(Gly)6(H2O)4](ClO4)6·5H2O, respectively. Thermal decompositions of the two coordination compounds were studied through the thermogravimetry (TG). Possible mechanisms of the decompositions are discussed.  相似文献   

8.
A new synthetic method of szaibelyite (2MgO·B2O3·H2O) has been reported. The enthalpy of solution of 2MgO·B2O3·H2O in 2.9842 mol dm−3 HCl (aq) was determined. From a combination of this result with measured enthalpies of solution of H3BO3 in 2.9842 mol dm−3 HCl (aq) and of MgO in (HCl+H3BO3) solution, together with the standard molar enthalpies of formation of MgO (s), H3BO3 (s), and H2O (l), the standard molar enthalpy of formation of −(2884.36±1.82) kJ mol−1 of 2MgO·B2O3·H2O was obtained.  相似文献   

9.
A new Ni4 distorted cubane complex [Ni43-OMe)4Q4(MeOH)4] (1) (where Q is the anion of 8-quinolinol) is obtained from the reaction of NaQ with Ni(OAc)2 · 4H2O in refluxing MeOH via solvent derived μ3-OMe assisted self-assembly of four nickel(II) centres. The periphery of [Ni4(OMe)4] cubane is covered by four Q and four MeOH molecules. This methanol specific reaction is not supported in solvent glycinol (Hgl; NH2(CH2)2OH), an amine substituted ethanol, producing monomeric [NiQ2(Hgl)2] · 2H2O (2 · 2H2O) instead and is able to cleave 1 to yield 2 · 2H2O. The cryomagnetic susceptibility data of powdered 1 can be modeled by a two J equation yielding J1 = −1.8(1) cm−1, J2 = 3.9(1) cm−1 and g = 2.24.  相似文献   

10.
A complex of holmium perchlorate coordinated with l-glutamic acid, [Ho2(l-Glu)2(H2O)8](ClO4)4·H2O, was prepared with a purity of 98.96%. The compound was characterized by chemical, elemental and thermal analysis. Heat capacities of the compound were determined by automated adiabatic calorimetry from 78 to 370 K. The dehydration temperature is 350 K. The dehydration enthalpy and entropy are 16.34 kJ mol−1 and 16.67 J K−1 mol−1, respectively. The standard enthalpy of formation is −6474.6 kJ mol−1 from reaction calorimetry at 298.15 K.  相似文献   

11.
An on-line solution-reaction isoperibol calorimeter has been constructed. The performance of the apparatus was evaluated by measuring the molar enthalpy of solution of KCl in water at 298.15 K. The uncertainty and the inaccurary of the experimental results were within ±0.3% compared with the recommended reference data. Using the calorimeter, the molar enthalpies of reaction for the following two reactions: LaCl3·7H2O(s)+2Hhq(s)+NaAc(s)=La(hq)2Ac(s)+NaCl(s)+2HCl(g)+7H2O(l) and PrCl3·6H2O(s)+2Hhq(s)+NaAc(s)=Pr(hq)2Ac(s)+NaCl(s)+2HCl(g)+6H2O(l), were determined at T=298.15 K, as −(78.3±0.6) and −(97.3±0.5) kJ mol−l, respectively. From the above molar enthalpies of reaction and other auxiliary thermodynamic quantities, the standard molar enthalpies of formation of La(hq)2Ac and Pr(hq)2Ac, at T=298.15 K, have been derived to be −(1535.5±0.7) and −(1536.7±0.6) kJ mol−l, respectively.  相似文献   

12.
Dirubidium calcium tetraborate octahydrate, Rb2Ca[B4O5(OH)4]2·8H2O, was prepared by reaction of Rb-borate aqueous solution with CaCl2 and it's structure has been determined by single-crystal X-ray diffraction data. It crystallizes in the orthorhombic system, space group P212121 with unit cell parameters, Z=4, The structure contains alternate layers of [B4O5(OH)4]2− polyanions separated by water molecules and Rb, Ca cations. The isolated [B4O5(OH)4]2− is constructed from two BO3(OH) tetrahedron groups and two BO2(OH) triangular groups joined at common oxygen atoms. The two BO3(OH) tetrahedron groups are further linked by means of an oxygen bridge across the ring. The Ca2+ ion displays seven coordination, while the two non-equivalent Rb+ ions display nine and seven coordination, respectively. Infrared and Raman (4000-400 cm−1) spectra of Rb2Ca[B4O5(OH)4]2·8H2O were recorded at room temperature and analyzed. Fundamental vibrational modes were identified and band assignments were made. The dehydration of this hydrated mixed borate occurs in one step and leads to an amorphous phase which undergoes a crystallization.  相似文献   

13.
The [Pt2(H2P2O5)4]4− ions in the ground and excited states and the excited-state complexes M-[Pt2(H2P2O5)4]3− and M2-[Pt2(H2P2O5)4]2− (M = Ag, Tl) were studied in solution with various density functional theory (DFT) functionals from Gaussian 09 and Amsterdam Density Functional (ADF) programs. Calculated results were compared with ultrafast X-ray solution scattering data. Time dependent DFT (TD-DFT) calculations with the B3PW91 functional and unrestricted open shell calculations with the mPBE functional produce good agreement with the experimental results. Compared to gas phase calculations, the surrounding solvent is found to play an important role to shorten the Pt-Pt and M-Pt (M = Ag, Tl) bond lengths, lowering the molecular orbital energies and influences the molecular orbital transitions upon excitation, which stabilizes the excited transient molecules in solution.  相似文献   

14.
The compounds M[PO2(OH)2]2·2H2O (M=Mg, Mn, Fe, Co, Ni, Zn, Cd) were prepared from super-saturated aqueous solutions at room temperature. Single-crystal X-ray structure investigations of members with M=Ni, Zn, Cd were performed at 295 and 120 K. The space-group symmetry is P21/n, Z=2. The unit-cell parameters are at 295/120 K for M=Ni: a=7.240(2)/7.202(2), b=9.794(2)/9.799(2), c=5.313(1)/5.285(1) Å, β=94.81(1)/94.38(1)°, V=375.4/371.9 Å3; M=Zn: a=7.263(2)/7.221(2), b=9.893(2)/9.899(3), c=5.328(1)/5.296(2) Å, β=94.79(1)/94.31(2)°, V=381.5/377.5 Å3; M=Cd: a=7.356(2)/7.319(2), b=10.416(2)/10.423(3), c=5.407(1)/5.371(2) Å, β=93.85(1)/93.30(2)°, V=413.4/409.1 Å3. Layers of corner-shared MO6 octahedra and phosphate tetrahedra are linked by three of the four crystallographically different hydrogen bonds. The fourth hydrogen bond (located within the layer) is worth mentioning because of the short Oh?O bond distance of 2.57-2.61 Å at room temperature (2.56-2.57 Å at 120 K); only for M=Mg it is increased to 2.65 Å. Any marked temperature-dependent variation of the unit-cell dimension is observed only vertical to the layers. The analysis of the infrared (IR) spectroscopy data evidences that the internal PO4 vibrations are insensitive to the size and the electronic configuration of the M2+ ions. The slight strengthening of the intra-molecular P-O bonds in the Mg salt is caused by the more ionic character of the Mg-O bonds. All IR spectra exhibit the characteristic “ABC trio” for acidic salts: 2900-3180 cm−1 (A band), 2000-2450 cm−1 (B band) and 1550-1750 cm−1 (C band). Both the frequency and the intensity of the A band provide an evidence that the PO2(OH)2 groups in M[PO2(OH)2]2·2H2O compounds form weaker hydrogen bonds as compared with other acidic salts with comparable O?O bond distances of about 2.60 Å. The observed shift of the O-H stretching vibrations of the water molecule in the order M=Mg>Mn≈Fe≈Co>Ni>Zn≈Cd has been discussed with respect to the influence of both the character and the strength of M↔H2O interactions.  相似文献   

15.
Low-temperature heat capacities of the compound Na(C4H7O5)·H2O(s) have been measured with an automated adiabatic calorimeter. A solid-solid phase transition and dehydration occur at 290-318 K and 367-373 K, respectively. The enthalpy and entropy of the solid-solid transition are ΔtransHm = (5.75 ± 0.01) kJ mol−1 and ΔtransSm = (18.47 ± 0.02) J K−1 mol−1. The enthalpy and entropy of the dehydration are ΔdHm = (15.35 ± 0.03) kJ mol−1 and ΔdSm = (41.35 ± 0.08) J K−1 mol−1. Experimental values of heat capacities for the solids (I and II) and the solid-liquid mixture (III) have been fitted to polynomial equations.  相似文献   

16.
Three Pd(II) complexes [Pd2(μ-Cl)2{7,8-(PPh2)2-7,8-C2B9H10}2] · 0.25CH2Cl2 (1), [Pd{7,8-(PPh2)2-7,8-C2B9H10}2] · 4CHCl3 (2) and [PdCl2(1,2-(PPh2)2-1,2-C2B10H10)] (3) have been synthesized by the reactions of 1,2-(PPh2)2-1,2-C2B10H10 with PdCl2 in acetonitrile, cyanophenyl and dichloromethane, respectively. A fourth complex, [PdI2(1,2-(PPh2)2-1,2-C2B10H10)] (4), was obtained by a ligand exchange reaction through the substitution of the Cl of complex 3 with I. All four complexes have been characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopy and X-ray structure determination. Single crystal X-ray determination showed that the carborane cage, nido for 1, 2 and closo for 3, 4, was coordinated bidentately to the Pd atom through the two P atoms, and the geometry at the Pd atom was square-planar in all the complexes.  相似文献   

17.
A detailed analysis of the 35Cl/37Cl isotope effects observed in the 19.11 MHz 103Rh NMR resonances of [RhCln(H2O)6−n]3−n complexes (n = 3–6) in acidic solution at 292.1 K, shows that the ‘fine structure’ of each 103Rh resonance can be understood in terms of the unique isotopologue and in certain instances the isotopomer distribution in each complex. These 35Cl/37Cl isotope effects in the 103Rh NMR resonance of the [Rh35/37Cl6]3− species manifest only as a result of the statistically expected 35Cl/37Cl isotopologues, whereas for the aquated species such as for example [Rh35/37Cl5(H2O)]2−, cis-[Rh35/37Cl4(H2O)2] as well as the mer-[Rh35/37Cl3(H2O)3] complexes, additional fine-structure due to the various possible isotopomers within each class of isotopologues, is visible. Of interest is the possibility of the direct identification of stereoisomers cis-[RhCl4(H2O)2], trans-[RhCl4(H2O)2], fac-[RhCl3(H2O)3] and mer-[RhCl3(H2O)3] based on the 103Rh NMR line shape, other than on the basis of their very similar δ(103Rh) chemical shift. The 103Rh NMR resonance structure thus serves as a novel and unique ‘NMR-fingerprint’ leading to the unambiguous assignment of [RhCln(H2O)6−n]3−n complexes (n = 3–6), without reliance on accurate δ(103Rh) chemical shifts.  相似文献   

18.
The N4O3 coordinating heptadentate imidazolidinyl phenolate ligand, H3L (2-(2′-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) forms with Cu(II) a rare aqua bridged complex [{Cu2(μ-L)(μ-H2O)}2](ClO4)2 · 4.5H2O (1 · 4.5H2O). Complex 1 · 4.5H2O contains two crystallographically different but chemically equivalent dinuclear [Cu2(μ-L)(μ-H2O)]+ cationic units in the asymmetric unit. The copper atoms of each dinuclear unit are in a distorted square-pyramidal environment and are held together by phenolate, imidazolidinyl and aqua bridges with a Cu···Cu separation of av. 3.34 Å. The compound exhibits a very weak antiferromagnetic exchange interaction (J = −0.77 cm−1, ? = J?1?2) between the two copper(II) (S = 1/2) ions. The 1H NMR spectrum of the complex shows a total of 17 hyperfine shifted peaks, as expected from the idealized Cs symmetry of the compound, spread over a very large window of chemical shift, spanning about 250 ppm. The complex, having an appropriate intermetallic separation for catechol binding, shows catecholase like activity in MeCN at 25 °C, with the aerobic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ).  相似文献   

19.
We report the results of a calorimetric study on the hydrolysis of UO22+ in different ionic media (NaClO4 aq, NaClaq) at 25 °C. Experiments in NaCl were performed at different ionic strength, at I≤1 mol l−1. The species considered in both ionic media were UO2(OH)+, (UO2)2(OH)22+ and (UO2)3(OH)5+, and in addition (UO2)3(OH)42+ and (UO2)3(OH)7 in NaClaq. The dependence on ionic strength of enthalpy changes in NaClaq was expressed by the simple linear equation ΔHpqH°pq+aI1/2 (a, empirical parameter). Comparison with literature findings is given and some recommended values are reported.  相似文献   

20.
Four tetrahydrofuran-2,3,4,5-tetracarboxylato bridged copper(II) coordination polymers with alkali metals, Na2[Cu(H2O)(THFTC)]·5H2O 1, K2[Cu3(H2O)2(THFTC)2]·9H2O 2, Rb2[Cu3(H2O)2(THFTC)2]·6H2O 3 and Cs2[Cu3(H2O)2(THFTC)2]·6H2O 4 (H4THFTC = tetrahydrofuran-2,3,4,5-tetracarboxylic acid) were prepared from reactions of Cu(NO3)2·3H2O, tetrahydrofuran-2,3,4,5-tetracarboxylic acid and alkali hydroxide or carbonate at pH 5.0–6.0 under ambient conditions. Compound 1 features 2D (33·43·54) topological layers generated from six-coordinated Cu2+ cations interlinked by (THFTC)4− anions, and the resulting layers are ecliptically stacked along [1 0 0] direction to form lozenge-shaped and octagonal channels filled with Na+ ions and lattice H2O molecules. In 2–4, both penta- and hexa-coordinated copper(II) ions are bridged by tetracarboxylate anions to form negatively charged 2D layers formulated as 2[Cu(H2O)2L3/2]2− with the corresponding alkali metal cations (K+, Rb+ or Cs+ ions) and hydrogen bonded lattice H2O molecules sandwiched between them. Additionally, the results about i.r. spectroscopic, thermal characterizations and magnetic properties are presented.  相似文献   

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