Solid-state reactions of lanthanide(III) with sodium salicylate and 8-hydroxyquinoline at room temperature

Article abstract of DOI:10.1081/SIM-120027317

At room temperature, four complexes Ln(Hsal)₂(hq) (Ln = La(III), Ce(III), Pr(III), Y(III), Hsal^- = C₆H₄(OH) COO^-, salicylateanion; hq^- = C₉H ₆NO^-, 8-hydroxyquinoline anion) were successfully synthesized by a solid-state reaction. These complexes were further characterized by elemental analyses, electrical conductance in non-aqueous solvents, x-ray powder diffraction, IR and TG-DTA. IR spectra showed that the rare earth ions are not only coordinated by the oxygen atom from the COO group, but also by the nitrogen atom and oxygen atom of 8-hydroxyquinoline. TG-DTA showed that the stability of the four complexes is better than that of sodium salicylate and 8-hydroxyquinoline. These results show good agreement with results of the literature. The unit cells of the complexes at room temperature have been determined by x-ray powder diffraction (XRD). The crystals of all four complexes belong to the triclinic system and P₁ space group. Unit cell parameters were found by using trial and error methods.

Full text of DOI:10.1081/SIM-120027317

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Synthesis and Reactivity in Inorganic and Metal-
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Solid‐State Reactions of Lanthanide(III) with
Sodium Salicylate and 8‐Hydroxyquinoline at Room
Temperature
Xiaofei Yang a , Qizhuang He a , Xibin Yu a , Yingying Yuan a & Hui Min a
a Department of Chemistry, Shanghai Normal University, Box 305, 100 Guilin Road,
Shanghai, 200234, P.R. China
Published online: 16 Nov 2010.
To cite this article: Xiaofei Yang , Qizhuang He , Xibin Yu , Yingying Yuan & Hui Min (2004): Solid‐State Reactions of
Lanthanide(III) with Sodium Salicylate and 8‐Hydroxyquinoline at Room Temperature, Synthesis and Reactivity in Inorganic
and Metal-Organic Chemistry, 34:1, 67-77
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SYNTHESIS AND REACTIVITY IN INORGANIC AND METAL-ORGANIC CHEMISTRY
Vol. 34, No. 1, pp. 67–77, 2004
Solid-State Reactions of Lanthanide(III)
with Sodium Salicylate and
8-Hydroxyquinoline at Room Temperature
*
Xiaofei Yang, Qizhuang He, Xibin Yu, Yingying Yuan,
and Hui Min
Department of Chemistry, Shanghai Normal University,
Shanghai, P.R. China
ABSTRACT
At room temperature, four complexes Ln(Hsal)2(hq) (Ln ¼ La(III), Ce(III),
Pr(III), Y(III), Hsal2 ¼ C6H4(OH)COO2, salicylate anion; hq2 ¼ C9H6NO2,
8-hydroxyquinoline anion) were successfully synthesized by a solid-state
reaction. These complexes were further characterized by elemental analyses,
electrical conductance in non-aqueous solvents, x-ray powder diffraction,
IR and TG–DTA. IR spectra showed that the rare earth ions are not only
coordinated by the oxygen atom from the COO group, but also by the nitrogen
atom and oxygen atom of 8-hydroxyquinoline. TG–DTA showed that the
stability of the four complexes is better than that of sodium salicylate and
8-hydroxyquinoline. These results show good agreement with results of the
*
Correspondence: Xiaofei Yang, Department of Chemistry, Box 305, Shanghai
Normal University, 100 Guilin Road, Shanghai 200234, P.R. China; E-mail:
yxfei1980@yahoo.com.cn.
67
DOI: 10.1081/SIM-120027317
0094-5714 (Print); 1532-2440 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

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Yang et al.
literature. The unit cells of the complexes at room temperature have been
determined by x-ray powder diffraction (XRD). The crystals of all four
complexes belong to the triclinic system and P1 space group. Unit cell
parameters were found by using trial and error methods.
Key Words: Solid state reactions; Room temperature; Lanthanide(III);
Sodium salicylate; Antibacterial.
INTRODUCTION
Solid state chemistry is of fundamental importance in material science.
Most studies have been focused on inorganic oxides at elevated temperatures.
But very few studies on the synthesis of coordination compounds at lower
temperatures or even at room temperature have been reported so far. Recently,
a series of complexes of transition metals with organic ligands such as
8-hydroxyquinoline, phenanthroline, salicyladoxime, bipyridyl and amino-
benzoic acid have been synthesized by solid state reactions at room
temperature.[1–5] However, the study of solid state reactions between rare
earth ions and mixed ligands has been rudimentary.[6,7] Complexes
Ln(Hsal)2(hq) were easily prepared by mixing ethanol solutions of
[8]
LnCl3 6H2O with salicylic acid and 8-hydroxyquinoline, but no reports
.
about their unit cells of these complexes. Chelate complexes of rare earth ions
with salicylic acid and salts have attracted considerable attention because they
have special antibacterial properties. Salicylic acid and sodium salicylate are
known to be antifungal compounds,[9,10] and 8-hydroxyquinoline also has
strong antiseptic properties. The synthesis of the title complexes by solid-
state reactions is of great significance as studies on solid state reactions of
coordination compounds and the preparation of new antibacterial
materials. Here we report the preparation, characterization and unit cells of
the new complexes Ln(Hsal)2(hq) (Ln ¼ La(III), Ce(III), Pr(III), Y(III),
Hsal2 ¼ C6H4(OH)COO2, hq2 ¼ C9H6NO2).
EXPERIMENTAL
Materials
Rare earth oxides, DMF (N,N-dimethylformamide), absolute ethyl
alcohol, sodium salicylate and 8-hydroxyquinoline were purchased from the
Yue Long Chemical Plant (Shanghai). All reagents were of analytical grade

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Solid-State Reactions of Lanthanide(III)
69
EQ1
and were used without further purification. Hydrated rare earth chlorides were
prepared from the corresponding oxides. Deionized water was used throughout.
General Measurements
The contents of the elements C, H, O were determined by using an
Elementar Vario EL elemental analyzer. Rare earth ions were titrated by a
complexometric method using EDTA and xylenol orange as indicator. FT-IR
spectra were measured on a PK-60000 FT-IR spectrometer in KBr pellets.
Differential thermal analysis and thermogravimetric analysis (TG–DTA)
were conducted in air at a heating rate of 10 8C min21 from room temperature
.
to 800 8C on a ZRP-1P thermal analyzer with a-alumina (a-Al2O3) as a
reference. X-ray diffraction (XRD) patterns of the ligands and the prepared
complexes were recorded on a D8 Advance X-ray (Bruker Company)
diffractometer by using CuKa radiation with a Ni-filter by the Debye–
Scherrer method. The lattice parameters of the complexes were calculated
using the program WIN-METRIC Ver 3.06.
Preparation of the Complexes by Solid-State Reactions
Accurately weighed sodium salicylate (15 mmol, 2.402 g) and
8-hydroxyquinoline (5mmol, 0.726 g) in a 3:1 molar ratio were mixed and
ground in an agate mortar for 30min in order to get the best possible homo-
.
geneity, then 5 mmol LnCl3 6H2O (LaCl3 6H2O, 1.767 g; CeCl3 6H2O,
.
.
.
.
1.773 g; PrCl3 6H2O, 1.777 g; YCl3 6H2O, 1.517 g) was added to the system.
The mixture turned yellow quickly, indicating the occurrence of the solid state
reaction. The mixture was further ground for 30min. And then the product was
washed with deionized water and three times with absolute ethyl alcohol. Finally
it was dried under vacuum for six hours, resulting in a yellow solid product.
RESULTS AND DISCUSSION
Elemental analysis results are in good accordance with the stoichiometry
Ln(Hsal)2(hq) (Ln ¼ La(III), Ce(III), Pr(III), Y(III), Hsal2 ¼ C6H4(OH)COO2,
hq2 ¼ C9H6NO2). The results of the elemental analyses and molar
conductance data are collected in Table 1 and show good agreement with
results of the literature.[8]
All complexes were found to be soluble in DMSO, DMF. However, they
were only slightly soluble in methanol, ethanol and nearly insoluble in water.

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Yang et al.

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Solid-State Reactions of Lanthanide(III)
71
Low molar conductances for the complexes in DMF correspond to non-
electrolytes.[11]
IR Spectra
In order to confirm the results of the IR spectra of the prepared complexes,
and for comparison, IR spectra of sodium salicylate and 8-hydroxyquinoline
were recorded. The infrared spectra of the four complexes, sodium salicylate
and 8-hydroxyquinoline were determined in KBr in the range 400–4000 cm21
and are shown in Table 2.
The IR spectra of the four complexes are similar to each other and the
results of Table 2 show good agreement with corresponding data in the
literature,[8] but displayed great differences from those of the ligands, showing
that the formation of the complexes had significant influence on the IR spectra.
When the acid is converted into salts the absorption band of the COOH group
at 1658 cm21 disappears, and two bands arising from asymmetric and
symmetric vibrations of COO2 appear at 1590 and 1379 cm21, respectively.
In the IR spectra of the prepared complexes, the absorptions arising from the
symmetric and asymmetric stretching modes of the salicylate are sharp, and
the separation between them, Dn ¼ nas(COO) 2 ns(COO) ¼ 211.6 cm21, is
indicative of bidentate chelating coordination.[12] However, the positions of
the vibration band at 3200–3300 and 1483 cm21 of the C–OH group which
does not change, or changes only slightly, in comparison to the corresponding
absorption band of the salt indicating that the phenol group does not take part
in the coordination of the rare earth ions. In the free ligand 8-hydroxyquinoline
a strong band at 1094 cm21 due to n(C55O) shifts to higher energy in the
complexes indicating the coordination of the OH group to the metal ions.
Another strong band at 1579 cm21 due to n(C55N) shifts to lower energy in
the complexes indicating the coordination of the –C55N– nitrogen to the
metal ions. From the above assignments, we can conclude that the rare earth
ions are not only coordinated by the oxygen atom from the COO group, but
also by the nitrogen atom and oxygen atom of 8-hydroxyquinoline.
X-ray Powder Diffractions (XRD) and Their Indexing
X-ray powder diffraction of the four complexes showed that the x-ray
powder diffraction patterns of the complexes show great difference from that of
the two ligands and the rare earth chlorides, but the x-ray powder diffraction
patterns of the four complexes are similar to each other, showing that the four
complexes have similar structure. The XRD datas are shown in Table 3.

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Yang et al.
d

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Solid-State Reactions of Lanthanide(III)
73
g
ab

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74
Yang et al.
u
u
u
u

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Solid-State Reactions of Lanthanide(III)
75
In the XRD patterns of the complexes, neither the diffraction pattern of the
.
ligands nor that of the LnCl3 6H2O precursors appear. The new patterns of
the complexes are not the addition of the patterns of the three reactants, but are
those of new compounds.
Indexing of the x-ray diffraction patterns shows that all of the diffraction
peaks in each pattern can be readily indexed by using trial and error methods.
As is shown in Table 4, all of the complexes are single-phase compounds with
triclinic symmetry and P1 space group.
Thermal Analysis
The data of TG–DTA for the complexes are showed in Table 5. Thermal
degradtion of the complexes showed one main step. The degradation patterns
were found to be similar. Take Y(Hsal)2(hq) for example, the decomposition
process of the complex is confirmed by a exothermic peak at 390–520 8C, and
the maximum of the peak is at 458 8C. The step corresponds to a weight loss of
77.32% (weight loss calculated: 77.74%) in the TG curve, which displays the
loss of salicylate and 8-hydroxyquinoline. The final residue is Y2O3
(determined by x-ray powder patterns).
In order to confirm the heat stability of the prepared complexes, and for
comparison, TG–DTA of sodium salicylate and 8-hydroxyquinoline were
also measured. It can be easily concluded that the stabilities of the four
complexes are better than those of sodium salicylate or 8-hydroxyquinoline.
It is important for the complexes to have good heat stability because they should
Table 5. Data of TG–DTA for the complexes.
Oxidative
decomposition
(exothermic
Melting
(endothermic
Total weight
loss (%) found
(calculated)
Compound
peak temp) (8C) peak temp) (8C)
Final residuea
NaHsal
Hhq
259
72
337.5
179
395
346
396
458
60.91 (66.90)
98.31 (100)
La(Hsal)2(hq)
Ce(Hsal)2(hq)
Pr(Hsal)2(hq)
Y(Hsal)2(hq)
194
184
187
205
69.57 (70.77)
69.29 (68.52)
66.75 (69.56)
77.32 (77.74)
La2O3
CeO2
Pr6O11
Y2O3
aThe final residue in each case was determined by XRD. The diffraction pattern of the
final residue in each case shows that all the peaks match very well to the published
powder patterns (JCPDS Card).

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Yang et al.
Figure 1. Suggested structure of the complexes.
endure temperature over 200 8C when being prepared as new antiseptic
materials.
CONCLUSIONS
In conclusion, four rare earth complexes of the formula Ln(Hsal)2(hq)
(Ln ¼ La(III), Ce(III), Pr(III), Y(III), Hsal2 ¼ C6H4(OH)COO2, hq2
¼
C9H6NO2) were synthesized, and their crystal structures were determined by
x-ray powder diffraction. The crystals of the complexes all belong to the
triclinic system and the P1 space group. The structure proposed for the
complexes is shown in Fig. 1.
ACKNOWLEDGMENTS
This work was financially supported by the Research Fund of Education
Committee and Technologies R&D Program of Shanghai City. We are also
grateful to Professor Zhu Y. L. of the Department of Chemistry, Fudan
University, Professor Wang Z. M. and Dr. Yang Shiping of the Department of
Chemistry, Shanghai Normal University, for their valuable suggestions and
discussions during the course of this work.

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77
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Received January 29, 2003
Accepted August 18, 2003
Referee I: L. E. Pence
Referee II: R. D. Pike

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