Search Results

You are looking at 1 - 10 of 57 items for

  • Author or Editor: Q. Chen x
  • Refine by Access: All Content x
Clear All Modify Search

Two Mn(II) chloride complexes containing guest molecules

Solvothermal syntheses, crystal structures and thermal decomposition

Journal of Thermal Analysis and Calorimetry
Authors: Q. Yang, S. Chen, and S. Gao

Abstract  

Two phenanthroline-manganese inclusion complexes with [MnCl(H2O)(phen)2]+ core have been synthesized and characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric analyses. Uncoordinated 2-mercaptothiazole (tzdtH) and 2-mercaptobenzothiazole (bztzH) as guest molecules are included in the complexes with formulas [MnCl(H2O)(phen)2]Cl·tzdtH (1) and {[MnCl(H2O)(phen)2]Cl}2·bztzH (2). X-ray structural analyses for complexes revealed that the complex 1 is triclinic, space group P1 with a=9.724(1) Å, b=11.858(1) Å, c=12.644(2) Å; β=89.056(2)°; Z=2, D c=1.513 Mg m−3, F(000)=638 and the complex 2 is triclinic, space group P1 with a=9.861(1) Å, b=11.476(1) Å; c=12.908(3) Å; β=84.991(2)°; Z=1, D c=1.511 Mg m−3, F(000)=600. Two complexes exhibit high stability up to 650°C. The molar specific heat capacities for the two complexes 1 and 2 can be estimated as being 96.175±0.332 and 72.505±0.364 J mol−1 K−1 at 298.15 K by RD496-III microcalorimeter, respectively.

Restricted access

Abstract  

Fourteen new complexes with the general formula of Ln(Hmna)3·nH2O (n=2 for Ln=La-Ho and n=1 for Er-Lu, H2mna=2-mercaptonicotinic acid) were synthesized and characterized by elemental analyses, IR spectra and thermogravimetric analyses. In addition, molar specific heat capacities were determined by a microcalorimeter at 298.15 K. The IR spectra of the prepared complexes revealed that carboxyl groups of the ligands coordinated with Ln(III) ions in bidentate chelating mode. Hydrated complexes lost water molecules during heating in one step and then the anhydrous complexes decomposed directly to oxides Ln2O3, CeO2, Pr6O11 and Tb4O7. The values of molar specific heat capacities for fourteen solid complexes were plotted against the atomic numbers of lanthanide, which presented as ‘tripartite effect’. It suggested a certain amount of covalent character existed in the bond of Ln3+ and ligands, according with nephelauxetic effect of 4f electrons of rare earth ions.

Restricted access

Abstract  

Five new complexes M(Hmna)2 [M=Mn(II) (1), Co(II) (2), Ni(II) (3), Cu(II) (4) and Zn(II) (5), H2mna=2-mercaptonicotinic acid] have been synthesized and characterized by elemental analyses, IR spectra, thermogravimetric analyses. In addition, molar specific heat capacities and enthalpy changes of reactions were determined by a microcalorimeter at 298.15 K. All the complexes exhibited similar IR spectra, the sulfur and oxygen atoms from monoanionic Hmna ligand coordinated to M2+ in a bidentate fashion. The thermal stability of M(Hmna)2 complexes varied in the sequence 1>2>3>4>5. The complexes were stable up to about 300°C and decomposed to oxides at higher temperatures. The molar specific heat capacities of the complexes were determined in the range between 106.452±0.399 and 145.920±0.423 J mol−1 K−1. The enthalpy changes of reactions, Δr H m θ, were determined from 18.28±0.05 to 52.59±0.07 kJ mol−1 for complexes 1–5, indicating that the thermodynamic stability of M(Hmna)2 increased in the sequence from Mn2+ to Zn2+.

Restricted access

Abstract  

Silica gel suspension is electrosprayed onto the VYNS thin film to get a circular pad. The weighed -radioactive standard solution is dropped on the circle. After drying it is covered with a thin film to get a sandwich source. A new method is developed in which the -sources of high resolution and quantification are obtained. The thin film is used to avoid the contamination of -detectors used for low-level measurements.

Restricted access

Abstract  

The kinetics of direct reduction of artificial chrome iron ore was studied by isothermal and non-isothermal methods. In the initial, middle and final periods, the reaction is controlled by nucleation and growth, a phase boundary reaction, and diffusion, respectively. In the main reaction region, the kinetic equation is 1–(1–)1/3=kt and the apparent activation energy is 270 kJ mol–1. The kinetic mechanisms found with the isothermal and non-isothermal methods do not differ, and the activation energy values are approximately the same. However, the non-isothermal method can demonstrate the kinetic process completely.

Restricted access

Summary

A rapid, simple, and practical high-performance liquid chromatographic method (HPLC) was developed and validated for the simultaneous determination of norephedrine (NME), norpseudoephedrine (NMP), ephedrine (E), pseudoephedrine (PE), and methylephedrine (ME) in traditional Chinese medicines (TCM) which contained Ephedrae Herba (Ephedra). This analysis could be accomplished within 12.5 min with an Alltima Phenyl Column by isocratic elution using a mixture of KH2PO4 (20 mM)-acetonitrile (96:4, v/v) as the mobile phase at a flow-rate of 0.6 mL min−1 and a wavelength of 210 nm. This method was successfully applied to quantify ephedra alkaloids in both Ma-xing-gan-shi decoction and Ephedra decoction. The concentration of total ephedra alkaloids (4.62 mg mL−1) in Ma-xing-gan-shi decoction was much lower than that (7.10 mg mL−1) in Ephedra decoction. Furthermore, the concentration of NME, NMP, E, PE, and ME was significantly lower in Ma-xing-gan-shi decoction than that in Ephedra decoction, respectively. The method was easily acceptable and would be popular with most analytical laboratories.

Full access

Abstract  

The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.

Restricted access

Abstract  

New solid complex of nitrilotriacetic acid and bismuth trichloride was synthesized by a solid phase reaction of nitrilotriacetic acid and bismuth trichloride at room temperature. The composition of the sample is BiCl3[N(CH2COOH)3]2.5. The crystal structure of the complex belongs to triclinic system with the lattice parameters: α=0.7849 nm, β=0.9821 nm, χ=2.0021 nm, α=96.50, β=98.76 and γ=90.49. The far-infrared spectra show the bonding between the Bi ion and N atom of nitrilotriacetic acid. The thermal analysis also demonstrates the complex formation between the bismuth ion and nitrilotriacetic acid. The gaseous pyrolysis product and the final residue in the thermal decomposition process are determined to check the thermal decomposition reaction.

Restricted access

Abstract  

A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights () and pre-peak areas (), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.

Restricted access

Abstract  

A novel solid complex, formulated as Ho(PDC)3 (o-phen), has been obtained from the reaction of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and 1,10-phenanthroline (o-phenH2O) in absolute ethanol, which was characterized by elemental analysis, TG-DTG and IR spectrum. The enthalpy change of the reaction of complex formation from a solution of the reagents, Δr H m θ (sol), and the molar heat capacity of the complex, c m, were determined as being –19.1610.051 kJ mol–1 and 79.2641.218 J mol–1 K–1 at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy change of complex formation from the reaction of the reagents in the solid phase, Δr H m θ(s), was calculated as being (23.9810.339) kJ mol–1 on the basis of an appropriate thermochemical cycle and other auxiliary thermodynamic data. The thermodynamics of reaction of formation of the complex was investigated by the reaction in solution at the temperature range of 292.15–301.15 K. The constant-volume combustion energy of the complex, Δc U, was determined as being –16788.467.74 kJ mol–1 by an RBC-II type rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δc H m θ, and standard enthalpy of formation, Δf H m θ, were calculated to be –16803.957.74 and –1115.428.94 kJ mol–1, respectively.

Restricted access