Search Results

You are looking at 1 - 10 of 129 items for :

  • "structural studies" x
  • Refine by Access: All Content x
Clear All

Abstract  

The chloro complexes of cobalt, nickel and copper with 3-phenylpyridine were prepared in ethanolic solution from which solid compounds were isolated. The cobalt and copper complexes have stoichiometry M2LCl4 while the nickel complex has stoichiometry NiLCl2. The suggested structure for the cobalt and copper complexes is tetrahedral, while for the nickel complex it is octahedral. Thermal analysis studies show that the cobalt and copper complexes form intermediate complexes before their metal oxides are produced. The nickel complex also forms an intermediate complex and then nickel chloride before the nickel oxide is obtained.

Restricted access

Abstract  

The chloro complexes of 2-amino-3-methylpyridine with cobalt(II) and copper(II) have been prepared in ethanolic solution and solid compounds have been isolated. The compounds have stoichiometry ML2Cl2 whereM is Co2+ or Cu2+ and L is 2-amino-3-methylpyridine. Spectral and magnetic studies have been used to obtain information about the environment of the metal ion in these compounds. The compounds have tetrahedral structures. The thermal decomposition of each compound has been studied using thermogravimetry and differential thermal analysis. Thermogravimetry studies show that the cobalt complex forms an intermediate compound before the metal oxide is produced while the copper compound undergoes decomposition with loss of organic ligand and the formation of copper chloride which then decomposes to give an oxide of copper. The enthalpy of reaction for each of the processes has been calculated from the thermal analysis curves.

Restricted access

Abstract  

The aim of this work was to investigate the influence of different levels of microwave irradiation on the structure and particle size characteristics of α-lactose monohydrate. The structural study of the samples was carried out by XRD, the presence of lactose polymorphs in the test samples was determined by DSC and the particle size distribution was measured by laser diffraction. The samples subjected to microwave irradiation retained their original X-ray patterns. No significant differences in thermal transition characteristics and particle size were observed. Hence, neither the occurrence of crystalline-amorphous transition resulted by microwave irradiation nor the presence of lactose polymorphs in the test samples can be assumed. The unmodified properties can be attributed to the fact that the water of crystallization is very difficult to remove from the crystal structure and is not free to move during microwave treatment, which results in stability to microwaves. Our results allow the conclusion that microwave processing of α-lactose monohydrate has no influence on further pharmaceutical technological properties, which are related to the structure and the particle size distribution of this substance.

Restricted access

Abstract  

Lanthanide picrates with 1,3-dithiane-1,3-dioxide ligand were synthesized and characterized. Thermal decomposition of these compounds by TG/DTG and DSC and structural studies were performed. It was found that the compounds are comprised in a single isomorphous series and their thermal decomposition occurs as exothermic events. The final products were found to be lanthanide dioxysulfates.

Restricted access

Abstract  

Structural studies of lanthanide ions (Nd3+≈Lu3+: about 1 mol/l) in the aqueous chloride (HCl: 0≈6 mol/l) and nitrate (HNO3: 0−13 mol/l) solutions were carried out by extended X-ray absorption fine structure (EXAFS). The radial structural functions appeared to be mainly characterized by hydration in both chloride and nitrate systems and coordination of nitrate ion in nitrate systems. These results indicated that nitrate ion forms inner-sphere complex with lanthanide but chloride ion hardly forms one. The quantitative analyses of EXAFS data have revealed that the total coordination numbers of lanthanide ranged from about 9 for light lanthanides to about 8 for heavy lanthanides in all the samples. The bond distances of Ln−O were from about 2.3 to 2.5 Å for Ln−OH2 and from about 2.4 to 2.6 Å for Ln−O2NO. Nitrate ion locates at 0.1 Å longer position than water, it suggested that nitrate ion ligates more weakly than water.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Maria Lalia-Kantouri, Maria Gdaniec, Agnieszka Czapik, Konstantinos Chrissafis, Wieslawa Ferenc, Jan Sarzynski, and Christos D. Papadopoulos

-007-8747-7 . 15. Dziewulska-Kulaczkowska , A , Mazur , L , Ferenc , W 2009 Thermal, spectroscopic and structural studies of zinc(II) complex with Nicotinamide . J Therm Anal Calorim. 96 1 255 – 260 10.1007/s10973-008-9851-z

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: F. J. Martínez Casado, M. Ramos Riesco, M. I. Redondo Yélamos, A. Sánchez Arenas, and J. A. Rodríguez Cheda

. 34. Martínez Casado , FJ , Ramos Riesco , M , Da Silva , I , Labrador , A , Redondo , MI , García Pérez , MV , López-Andrés , S , Cheda , JAR . Thermal and structural study of the crystal phases and

Restricted access

Abstract  

Blends of poly(ether ketone) (PEK) with poly(terephthaloyl-imide) (a thermoplasticpolyimide, TPI) were studied by temperature-modulated DSC (TMDSC) and X-ray diffraction. Samples were prepared by compression moulding of the premixed materials at 400°C and quenched to prevent crystallisation.The amorphous blends showed a single glass transition but with a jump in the temperature value at 60 mass% of PEK, indicating limited miscibility of the system at both sides of the composition series in the quenched, glassy state. Two cold crystallisation peaks over the concentration range 30 to 70 mass% of PEK were observed, but only one for all other compositions. A single melting peak was observed in all systems.Blends crystallised from the glassy state showed eutectic behaviour with the presence of the crystals of both pure components. This is the first reported case of two semicrystalline polymers exhibiting eutectic co-crystallisation. The formation of eutectic crystals is proof of full miscibility of the two polymers in their liquid state, i.e. at a temperature of 400°C and above. Blends cooled from the melt at a cooling rate of 2 K min–1 showed a single glass transition and an extended melting range.Crystallisation during a second melting run generally starts at a different temperature then during the first run indicating chemical changes occurred in the molten state. This change was also verified by an exothermic peak above the melting temperature using TMDSC.

Restricted access

Abstract  

Ferrocyanides of zirconium(IV) and tin(IV), antimonates of cerium(IV) and titanium(IV), and cerium(IV) tungstate, has been shown to be useful materials as inorganic ion exchangers in radio- and analytical chemistry. These materials are sufficiently stable towards high dose of γ-radiations. Attempt is made to study some structural aspects and possible exchange sites of these materials using different techniques like thermal, Mössbauer and infrared spectroscopy.

Restricted access

Abstract  

An attempt has been made to assign empirical formulae and possible ion exchange site for the antimonates of Zr(IV), Sn(IV) and Cr(III). On the basis of analytical data, exchange capacity, infra-red and thermoanalytical investigations these ion exchangers have the compositions as: ZrO2·0.5 Sb2O5·5.1 H2O, SnO2·2.5 Sb2O5·15 H2O and Cr2O3·5Sb2O5·31 H2O. Water molecules shown is the total water present which includes both water of constitution and water of crystallization. The H+ attached to anionic part of the exchanger, i.e., Sb−OH is the possible site for cation exchange. However, the general shape of curves in McKay Plot and the dependence of Kd values on the concentration of metal ions in solution at constant pH suggest more than single possible exchange site.

Restricted access