The thermal decompositions of Y, La and lanthanide (from Ce(III) to Lu(III) benzene-1,2-dioxyacetates with general formula Ln2(C10H8O6)3·nH2O were studied. The hydrated complexes first lose water of crystallization in one or two steps to yield anhydrous compounds or hydrates containing coordination water molecules, and then decompose to the oxides Ln2O3, CeO2, Pr6O11 and Tb4O7 with formation of intermediates, carbonates and oxycarbonates (La, Pr-Eu), oxycarbonates (Y, Tb-Lu) or carbonate (Gd) only. Anhydrous cerium(III) benzene-1,2-dioxyacetate decomposes on heating directly to CeO2.
Authors:J. Locatelli, E. Rodrigues, A. Siqueira, E. Ionashiro, G. Bannach, and M. Ionashiro
Solid-state Ln(Bz)3·H2O compounds where Ln stands for trivalent yttrium or lanthanides and Bz is benzoate have been synthesized. Simultaneous thermogravimetry-differential
thermal analysis (TG-DTA), X-ray powder diffractometry, infrared spectroscopy and chemical analysis were used to characterize
and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration,
thermal stability and thermal decomposition of the isolated compounds.
On evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and ethanolammonium sulphate in a molar ratio
higher than 1:12, in the presence of sulphuric acid, double sulphates of Sm, Eu, Ho, Tm, Yb and Y with a waxy feel were obtained.
The stoichiometry of the obtained compounds was determined by means of elemental and TG analysis. On the basis of X-ray powder
diffraction patterns it was concluded that an isostructural group with a general formula: Ln2(HOCH2CH2NH3)8(SO4)78H2O was obtained. The above compounds have a stoichiometry and a crystal structure different from those of the double sulphates
of La, Ce, Pr and Nd with the same monovalent cation, as presented earlier.
The thermal decomposition of the investigated compounds in the temperature range from ambient temperature up to 1173 K occurred
in a similar way, mainly in three not well-differentiated steps. Lanthanide oxysulphates were obtained as final products.
Complexes of lanthanides(III) (La-Lu) and Y(III) with 3,4,5-trihydroxybenzoic acid (gallic acid) were obtained and their thermal decomposition, IR spectra and solubility in water have been investigated. When heated, the complexes with a general formula Ln(C7H5O5)(C7H4O5)·nH2O (n=2 for La-Ho and Y: n=0 for Er-Lu) lose their crystallization water and decompose to the oxides Ln2O3, CeO2, Pr6O11, and Tb4O7, except of lanthanum and neodymium complexes, which additionally form stable oxocarbonates such as Ln2O2CO3. The complexes are sparingly soluble in water (0.3·10–5–8.3·10–4 mol dm–3).
Complexes of lanthanide(III) (La–Lu) and Y(III) with 1-hydroxy-2-naphthoic acid were obtained as crystalline compounds with
a general formula Ln[C10H6(OH)COO]3⋅nH2O:n=6 for La–Tm and Y, n=2 for Yb and n=0 for Lu. IR spectra of the prepared complexes were recorded, and their thermal decomposition in air were investigated. Spectroscopic
data suggest that in the coordination of metal-organic ligand only oxygen atoms from the carboxylate group take part. When
heated, the complexes decompose to the oxides Ln2O3, CeO2, Pr6O11 and Tb4O7 with intermediate formation of Ln(C11H7O3)(C11H6O3).
′-dimethylformamide (dmf) is a very popular solvent applied in the synthesis of lanthanide coordination polymers. Polarity of dmf molecules is crucial in the growth process of crystals. Dmf dissolves well not only most of the organic ligands but also inorganic
Authors:Zofia Rzączyńska and Anna Danczowska-Burdon
number of transition and lanthanide complexes with series of the pyridinedicarboxylic acids, which includes the 2,3-, 2,4-, 2,5-, 2,6-, 3,4-, and 3,5-pyridinedicarboxylic isomers, have been reported in the recent two decades. Although there are many
Some new hydrazinium lanthanide sulphite hydrates of the formula N2H5Ln(SO3)2(H2O)2 where Ln=La, Pr, Nd and Sm and N2H5Ce(SO3)2 have been prepared and characterized by chemical analyses, magnetic studies and electronic and infrared spectroscopy. Thermal
degradation of these complexes has been investigated by simultaneous TG-DTA techniques. These complexes decompose in air after
dehydration to give the respective lanthanide sulphate as the final residue. However, cerium complex gives a mixture of cerium
sulphate and ceric oxide as the end products. Cerium and neodymium complexes have also been subjected to thermal degradation
in nitrogen atmosphere and the dehydration of neodymium complex was observed at a higher temperature than in air. The anhydrous
neodymium and cerium complexes decompose in one step to give the respective sulphate in nitrogen atmosphere.