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Journal of Thermal Analysis and Calorimetry, Vol. 92 (2008) 3, 945–951
SYNTHESIS, CHARACTERIZATION AND THERMAL BEHAVIOUR OF
SOLID 2-METHOXYBENZOATES OF TRIVALENT METALS
A. B. Siqueira1,*, C. T. Carvalho1, E. Y. Ionashiro2, G. Bannach2, E. C. Rodrigues3 and
M. Ionashiro1
1Instituto de Química, UNESP, CP 355, CEP 14801-970, Araraquara, SP, Brazil
2Universidade Estadual de Ponta Grossa, CEP 84010-919, Ponta Grossa, PR, Brazil
3Funda¸±o Educacional de Barretos, CEP 14780-000, Barretos, SP, Brazil
Solid-state Ln(L)3 compounds, where Ln stands for trivalent Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y and L is 2-methoxybenzoate
have been synthesized. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning
calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy and complexometry were used to characterize and to study
the thermal behaviour of these compounds. The results provided information on the composition, dehydration, coordination mode,
structure, thermal behaviour and thermal decomposition.
Keywords: characterization, heavier lanthanides, 2-methoxybenzoate, thermal behaviour
Introduction
thermal analysis (TG-DTA), differential scanning
calorimetry (DSC) and other methods of analysis.
Several metal-ion compounds of benzoate,
C6H5–COO– (Bz), and phenyl-substituted derivatives
of benzoate have been investigated in aqueous
solutions [1–3] and in solid state [4–13]. In aqueous
solutions these works reported the thermodynamics of
complexation of lanthanides by some benzoic acid
derivatives; the spectroscopic study of trivalent
lanthanides with several carboxylic acids including
benzoic acid; the influence of pH, surfactant and
synergic agent on the luminescent properties of
terbium chelates with benzoic acid derivatives and
thermodynamic of complexation of lanthanides by
benzoic and isophthalic acids [1–3].
In solid state the works reported the thermal and
spectral studies on solid compounds of benzoate and
derivatives with rare earth elements; the reaction of
divalent copper, cobalt and nickel with 3-hydroxy-
4-methoxy and 3-methoxy-4-hydroxybenzoic acid and
structure for these compounds has been proposed on the
basis of spectroscopic and thermogravimetric data;
the thermal decomposition of thorium salts of benzoic
and 4-methoxybenzoic acids in air atmosphere and
thermal behaviour of solid state methoxybenzoate of
some divalent transition metal ions [4–13].
Experimental
Materials
The 2-methoxybenzoic acid (HL) 99% was obtained
from Aldrich. Aqueous solution of Na–L 0.15 mol L–1
was prepared from aqueous HL suspension by treatment
with sodium hydroxide solution (0.1 mol L–1). Lanthanide
chlorides were prepared from the corresponding
metal oxides by treatment with concentrated hydro-
chloric acid. The resulting solutions were evaporated
to near dryness, the residues were again dissolved in
distilled water, transferred to a volumetric flask and
diluted in order to obtain ca. 0.1 mol L–1 solutions,
whose pH were adjusted to 5.0 by adding diluted
sodium hydroxide or hydrochloric acid solutions. The
solid state compounds were prepared by adding
slowly, with continuous stirring the ligand solution to
the respective metal chloride solutions, until total
precipitation of the metal ions. The precipitates were
washed with distilled water until elimination of the
chloride ions, filtered through and dried on Whatman
n° 42, filter paper, and kept in a desiccator over
anhydrous calcium chloride.
In this work 2-methoxybenzoates of trivalent Eu,
Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y were synthesized.
The compounds were investigated by means of
infrared spectroscopy, X-ray powder diffractometry,
simultaneous thermogravimetry and differential
In the solid-state compounds, hydrate water,
ligand and metal ion contents were determined from
the TG curves. The metal ions were also determined
by complexometric titrations with standard EDTA
*
Author for correspondence: massaoi@yahoo.com.br
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