FT-IR study of rare earth 4-aminobenzenesulfonate complexes

Article abstract of DOI:10.1016/S0022-2860(00)00744-4

The crystal structure of lanthanum 4-amino-benzenesulfonate complex has been determined by X-ray diffraction. The crystal data indicate that lanthanum and neodymium 4-amino-benzenesulfonates are isomorphous. The FT-IR spectroscopic study of rare earth 4-amino-benzenesulfonate complexes showed that the spectra of light rare earth (La, Nd, Sm, Eu) complexes are similar and so are the spectra of heavy rare earth (Dy, Er, Y) complexes. There are remarkable differences between the spectra of light rare earth and heavy rare earth complexes. Based on above results, we infer that light rare earth (La, Nd, Sm, Eu) complexes are isomorphous and three heavy rare earth (Dy, Er, Y) complexes are of a different structure but also isomorphous.

Full text of DOI:10.1016/S0022-2860(00)00744-4

Journal of Molecular Structure 560 (2001) 115±120
www.elsevier.nl/locate/molstruc
FT-IR study of rare earth 4-aminobenzenesulfonate complexes
a,b
a
b
b
a
a,
*
Ying Zhao , Bo Sun , Yizhuang Xu , Dujin Wang , Shifu Weng , Jinguang Wu ,
Duanfu Xub, Guangxian Xua
aState Key Laboratory of Rare Earth Materials Chemistry and Applications, Peking University, Beijing 100871, People's Republic of China
bState Key Laboratory of Polymer Physics and Chemistry, Center for Molecular Science, Institute of Chemistry,
The Chinese Academy of Sciences, Beijing 100080, People's Republic of China
Received 10 December 1999; accepted 5 September 2000
Abstract
The crystal structure of lanthanum 4-amino-benzenesulfonate complex has been determined by X-ray diffraction. The crystal
data indicate that lanthanum and neodymium 4-amino-benzenesulfonates are isomorphous. The FT-IR spectroscopic study of
rare earth 4-amino-benzenesulfonate complexes showed that the spectra of light rare earth (La, Nd, Sm, Eu) complexes are
similar and so are the spectra of heavy rare earth (Dy, Er, Y) complexes. There are remarkable differences between the spectra
of light rare earth and heavy rare earth complexes. Based on above results, we infer that light rare earth (La, Nd, Sm, Eu)
complexes are isomorphous and three heavy rare earth (Dy, Er, Y) complexes are of a different structure but also isomorphous.
q 2001 Elsevier Science B.V. All rights reserved.
Keywords: FT-IR spectroscopy; Rare earth complexes; 4-Aminobenzenesulfonates; Crystal structure; X-ray diffraction
1. Introduction
amino and sulfonate groups participate in the coordi-
nation with Co21 ions. Compared with many crystal
structures of alkali, alkaline earth and transitional
metal complexes of arylsulfonic acid reported in the
literature [4,6±12], relatively little was known about
the rare earth complexes [1,13,14]. In this paper,
different compositions were found for light and
heavy rare earth complexes of 4-aminobenzenesul-
fonic acid and also distinct differences were observed
in their corresponding FT-IR spectra. The crystal
structure of lanthanum 4-aminobenzenesulfonate is
also presented.
The sulfonate group in metal complexes may act as
monodentate, bidentate chelating or tridentate ligand
to different metal ions according to the property of the
metal ions and the number of water molecules therein
[1±3]. The coordination fashion of the sulfonate
group in arylsulfonate complexes also depends on
other substituting groups on the benzene ring and
the number of water molecules. For example, in the
hexaaqua Co21 complexes of benzenesulfonate [4],
the central ions are coordinated only with water mole-
cules, and the benzenesulfonate forms hydrogen
bonding with water molecules. While for tetraaqua
Co aminobenzenesulfonate complexes [5], both
2. Experimental
2.1. Synthesis
* Corresponding author. Tel.: 186-10-6275-7951; fax: 186-10-
6275-1708.
4-aminobenzenesulfonic acid was dissolved in hot
E-mail address: wjg@chemms.chem.pku.edu.cn (J. Wu).
0022-2860/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-2860(00)00744-4

116
Y. Zhao et al. / Journal of Molecular Structure 560 (2001) 115±120
Table 1
Elemental results of title complexes
non-hydrogen atom coordinates. The coordinates of
hydrogen atoms of benzene ring were located in
calculated positions and the coordinates of hydrogen
atoms of ±NH2 were calculated according to the
diffraction density around the nitrogen atoms.
Complexes
C
H
N
Cal.
Exp.
Cal.
Exp.
Cal.
Exp.
La
Nd
Sm
Eu
Tb
Dy
Er
27.04
26.86
26.66
26.60
25.81
25.70
25.56
26.92
27.13
26.66
26.39
25.94
25.90
25.95
4.29
4.26
4.22
4.22
4.33
4.31
4.28
4.21
4.17
4.15
4.11
3.99
3.99
3.56
5.26
5.22
5.18
5.17
5.02
4.99
4.97
5.17
5.16
5.05
4.95
4.89
4.83
4.82
3. Results and discussion
3.1. Elemental analysis
The elemental analysis gave the following results:
LnL3´8H2O (Ln ˆ La, Nd, Sm, Eu), LnL3´9H2O
(Ln ˆ Tb, Dy, Er; L represents the p-aminobenzene-
sulfonate anion), see Table 1.
water, lanthanide (La, Nd, Sm, Eu, Tb, Dy, Er or Y)
hydroxide was added until it could not be dissolved
further. After ®ltration, the ®ltrate was left under room
temperature, crystals were formed after several days.
For lanthanum, crystals suitable for single crystal
determination were obtained.
Table 3
Ê
Selected bond lengths (A) and angles (8) in LaL3´8H2O
La±O(2)
2.464(9) La±O(4)
2.545(10) La±O(11)
2.625(10) La±O(13)
2.556(9) La±O(15)
2.692(10) S(1)±C(1)
1.456(11) S(1)±O(2)
1.439(10) S(2)±C(7)
1.437(10) S(2)±O(5)
1.419(11) S(3)±C(13)
1.409(14) S(3)±O(8)
1.482(14) O(2)±La±O(4)
2.484(10)
2.561(10)
2.613(9)
La±O(10)
La±O(12)
La±O(14)
La±O(16)
S(1)±O(1)
S(1)±O(3)
S(2)±O(4)
S(2)±O(6)
S(3)±O(7)
S(3)±O(9)
2.2. Instruments
2.557(9)
The elemental analysis was performed with Carlo
Erba 1106 microanalysis instrument. FT-IR spectra
were performed in Nujol mull on a Nicolet Magna
750 IR spectrometer.
All diffraction data were collected on a Ragaku
AFC6S diffractometer, with MoKa radiation ꢀl ˆ
1.739(13)
1.461(10)
1.749(14)
1.442(12)
1.772(15)
1.433(16)
90.4(3)
ꢀ
0:71073 A; graphite monochromator) at room
O(2)±La±O(10)
77.6(3)
O(4)±La±O(10) 138.7(3)
temperature in v ±2u scan mode. Corrections to the
absorption data were made by semi-empirical method.
The structure was solved by direct method with
shelxtl PLUS(VMS) program, and re®ned by the
full-matrix least-squares method to determine the
O(2)±La±O(11) 138.4(3)
O(10)±La±O(11) 90.0(3)
O(4)±La±O(11)
O(2)±La±O(12)
73.1(3)
70.1(3)
O(4)±La±O(12)
71.4(3)
O(10)±La±O(12) 136.1(3)
O(2)±La±O(13) 136.3(3)
O(10)±La±O(13) 67.4(3)
O(12)±La±O(13) 120.1(3)
O(4)±La±O(14) 139.2(3)
O(11)±La±O(14) 137.8(3)
O(13)±La±O(14) 69.6(3)
O(11)±La±O(12) 133.8(3)
O(4)±La±O(13) 133.2(3)
O(11)±La±O(13) 68.4(3)
O(2)±La±O(14)
78.2(3)
Table 2
O(10)±La±O(14) 77.2(3)
O(10)±La±O(14) 67.9(3)
O(12)±La±O(14) 138.9(3)
O(10)±La±O(15) 135.8(3)
O(12)±La±O(15) 68.7(3)
O(14)±La±O(15) 86.4(3)
Structural parameters of LaL3´8H2O
Formula
Mw
C18H34LaN3O17S3
799.6
O(4)±La±O(15)
76.8(3)
O(11)±La±O(15) 75.2(3)
O(13)±La±O(15) 68.5(3)
Color; habit
Colorless needle
0.10 £ 0.20 £ 0.30
Orthorhombic
Pbca
Crystal size (mm)
O(2)±La±O(16)
69.0(3)
Crystal system
Space group
O(4)±La±O(16)
69.3(3)
O(10)±La±O(16) 69.5(3)
O(12)±La±O(16) 121.8(3)
O(14)±La±O(16) 137.1(3)
O(1)±S(1)±O(2) 111.9(6)
O(2)±S(1)±O(3) 112.7(6)
O(4)±S(2)±O(8) 111.6(7)
O(7)±S(3)±O(2) 118.3(9)
O(8)±S(3)±O(9) 108.9(8)
O(11)±La±O(16) 69.5(3)
O(13)±La±O(16) 118.1(3)
O(15)±La±O(16) 136.5(3)
O(1)±S(1)±O(3) 111.1(6)
O(4)±S(2)±O(5) 109.2(7)
O(5)±S(2)±O(6) 114.7(8)
O(7)±S(3)±O(9) 108.8(7)
Ê
7.985(3) A
Ê
23.701(9) A
Ê
32.039(8) A
a
b
c
Ê 3
V(A )
6063(4)
8
Z
Density (Mg m23
)
1.752

Y. Zhao et al. / Journal of Molecular Structure 560 (2001) 115±120
117
Fig. 1. The structure of LaL3´8H2O (L ˆ 4-aminobenzenesulfonate anion).
Fig. 2. Hydrogen bonding network and layer structure in LaL3´8H2O (L ˆ 4-aminobenzenesulfonate anion).

118
Y. Zhao et al. / Journal of Molecular Structure 560 (2001) 115±120
Fig. 5. FT-IR spectra of the complexes and ligand in the range of
1290±950 cm21: (a) ligand, (b) La complex, (c) Nd complex, (d) Er
complex.
Fig. 3. FT-IR spectra of the complexes and ligand in the range of
3650±3100 cm21: (a) ligand, (b) La complex, (c) Er complex.
3.2. Crystal structure of LaL3´8H2O
The collection parameter and data were listed in
Table 2. The structure of the complexes LaL3´8H2O
is given in Fig. 1. Selected bond lengths and bond
angles are listed in Table 3. In the complex, the
lanthanum atom is coordinated to two oxygen atoms
from two ±SO32 groups and seven oxygen atoms from
water molecules, thus the coordination number of
lanthanum atom is nine, another water molecule exists
as lattice water, the other 4-aminobenzenesulfonic
acid molecule is not bonded to the lanthanum atom,
but forms H-bonding with water molecules. The coor-
dination geometry around the lanthanum ion is a
tricapped trigonal prism. There is complicated
hydrogen bonding network between ±SO32 groups,
water molecules and ±NH2 group in the complexes.
Also layer structure can be observed in the compound
as shown in Fig. 2. According to the report of
Staryhowwicz [13], the La and Nd complexes are
isomorphous.
Compared with the sulfonate group in the
complexes of Ln(PTS)3´9H2O [1], in which PTS is
p-methylbenzenesulfonate anion, the geometry of
sulfonate group in the complexes of LaL3´8H2O was
Fig. 4. FT-IR spectra of the complexes in the range of 1700±
1550 cm21: (a) ligand, (b) La complex, (c) Er complex.

Y. Zhao et al. / Journal of Molecular Structure 560 (2001) 115±120
119
Table 4
The assignment of bands in the FT-IR spectra of ligand and the title complexes
LnL3´8H2O
La
LnL3´9H2O
Dy
Ligand
Assignments
Nd
Sm
Eu
Er
Y
3458
3372
3305
3253
3238
3458
3372
3304
3253
3237
3458
3373
3305
3254
3237
3373
3322
3375
3321
3373
3321
3377
3319
nO±H
nN±H
1649
1624
1651
1631
1653
1632
1643
1634
1642
1642
dH±O±H
dH±N±H
1632
1602
1602
1602
1600
1233
1600
1232
1600
1232
1601
1245
nCyC
1208
1186
1174
1209
1187
1172
1212
1187
1176
1211
1187
1175
1209
1163
1209
1163
1208
1163
n
as,SO 2
3
1155
1124
1129
1129
1130
1129
1127
1050
1127
1051
1127
1051
bC±H
1043
1033
1044
1033
1045
1033
1046
1033
1046
1033
1041
1034
1041
1033
n
s,SO 2
3
1034
1009
1012
1013
1013
1012
1009
1009
1009
b
C±H 1 nC±S
distorted, especially in the non-coordinated sulfonate
group, the largest difference between the angle O±S±
O is 108 and the largest difference between the three
LnL3´9H2O (Dy, Er, Y). But there are distinct differ-
ences between the spectra of the two series of
complexes, e.g. the vibrational absorption bands of
H2O and ±SO32. Remarkable differences between
the absorption bands of ±SO32 group reveal its
different coordination fashions in two series of
complexes.
Ê
S±O is 0.07 A.
3.3. FT-IR spectra
It is well-known that the property of lanthanide ions
are similar. Ohki and co-workers [14] have reported
Selected FT-IR spectra are shown in Figs. 3±5. The
main absorption bands and the preliminary assign-
ments are listed in Table 4. The IR spectra of the
complexes show great difference from that of the
ligand. These changes indicate the formation of
these complexes. Absorption bands in the range of
3700±3100 cm21 show that there are water molecules
in the complexes. In the crystal of 4-aminobenzene-
sulfonic acid, ±NH31 exists instead of ±NH2, therefore
there are no nN±H absorption bands in its IR spectrum,
while combination broad absorption bands of H2O and
±NH2 appear in the spectra of title complexes. This
difference indicates that the bond between ±SO3H and
±NH2 was destroyed, thus ±NH2 group appears.
The spectra of LnL3´8H2O (La, Nd, Sm, Eu) are
similar to each other and so are the spectra of
that
the
crystal
structure
of [RE(PTS)2
(H2O)6](PTS)´3H2O (RE ˆ Y, Sm, Gd, Dy, Ho, Er,
Yb; PTS represents the p-methylbenzenesulfonate
anion) are similar and so are their IR spectra. So it
may be concluded that rare earth complexes with
same composition and similar IR spectra are
isomorphous. According to our result, both the IR
spectra and crystal structure of La and Nd complexes
are all similar, and the IR spectra of La, Nd, Sm and Eu
complexes are also similar. Therefore, it is concluded
that the crystal structures of Sm and Eu complexes are
similar to those of La and Nd complexes. In other
words, light rare earth LnL3´8H2O (La, Nd, Sm, Eu)
complexes are isomorphous.

120
Y. Zhao et al. / Journal of Molecular Structure 560 (2001) 115±120
From the results of elemental analyses and FT-IR
References
spectra, we can infer that the crystal structure of heavy
rare earth complexes should be different from those of
light rare earth complexes. Also, the same composi-
tion and the similarity of IR spectra of heavy rare
earth complexes may re¯ect that the complexes of
LnL3´9H2O (Dy, Er, Y) are isomorphous too.
Compared with rare earth complexes of 4-methyl-
benzenesulfonates whose crystal structures were
similar, it can be seen that the substituting group on
the benzene ring has an impact on the crystal structure
of rare earth complexes.
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Acknowledgements
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This project was supported by the National Natural
Science Foundation of China (No. 29671002 and No.
39730160) and State Key Project of Basic Research
and Development of China (No. G1998061311).
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