catena-Poly[[bis[pentaaqua-erbium(III)]-μ-benzenehexacarboxylato] tetrahydrate]

Article abstract of DOI:10.1107/S010827010300341X

The title compound is composed of one-dimensional polymeric {[Er₂(C₁₂O₁₂)(H₂O)₁₀] ·4H₂O}_n chains containing Er in a slightly distorted antiprismatic eightfold coordination. The benzenehexacarboxylate ion is located about an inversion centre. Water molecules of crystallization, linked by hydrogen bonding to water molecules of the rare earth coordination spheres or the carboxylate groups of the organic ligands, fill the space generated by the packing of the separated chains.

Full text of DOI:10.1107/S010827010300341X

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
The Er atom in (I) is eight-coordinated by three O atoms
from two mellitate ions and ®ve water O atoms. The ErÐO
distances are quite homogeneous (Table 1) and the environ-
ment of the Er atom is a slightly distorted square antiprism
(Fig. 3). The mellitate ion is located about an inversion centre
ISSN 0108-2701
catena-Poly[[bis[pentaaqua-
erbium(III)]-l-benzenehexa-
carboxylato] tetrahydrate]
Â
Andre Deluzet and Olivier Guillou*
GRCM Chimie Inorganique des Lanthanides, INSA CS 14315, F-35043 Rennes
Cedex, France
Correspondence e-mail: olivier.guillou@insa-rennes.fr
and each ligand is bonded to four different Er atoms. The six
carboxylate groups are each linked to an Er atom via one O
atom, while the other O atom remains free. The carboxylate
groups are greatly twisted out of the plane of the benzene ring
Received 14 October 2002
Accepted 11 May 2003
Online 20 June 2003
The title compound is composed of one-dimensional poly-
meric {[Er2(C12O12)(H2O)10]Á4H2O}n chains containing Er in a
slightly distorted antiprismatic eightfold coordination. The
benzenehexacarboxylate ion is located about an inversion
centre. Water molecules of crystallization, linked by hydrogen
bonding to water molecules of the rare earth coordination
spheres or the carboxylate groups of the organic ligands, ®ll
the space generated by the packing of the separated chains.
Comment
Aromatic acids usually form rare earth salts which exhibit
optical properties (strong ¯uorescent emission) and possess
very important physical and biological properties. Mellitic acid
(benzenehexacarboxylic acid) can lose between two to six H
atoms, depending on the reaction conditions used, and this
gives rise to a great diversity of salts. The mellitate anion is
known to be a multidentate agent via its carboxylate O atoms
to metal cations, such as main group metal ions (for example,
Ca or Al; Uchtman & Jandacek, 1980; Giacovazzo et al., 1973),
transition metal ions (CuII, NiII, CoIII or YIII; Endres &
Knieszner, 1984; Robl & Hentschel, 1991, 1992) or rare earth
ions (LaIII; Wu et al., 1996). In these materials, the dimen-
sionality of the networks varies from three-dimensional in
[Al2{C6(CO2)6}]Á16H2O to two-dimensional in the Cu com-
pound, where layers are linked to each other by hydrogen
bonds, and one-dimensional in the Co or Ni compounds,
where in®nite chains are formed. We present here the crystal
structure of the title compound, (I), an analogous Er
compound with mellitate.
The title compound, (I), forms a one-dimensional polymer.
As shown in Fig. 1, the chains are formed by the succession of
one organic ligand and a pair of Er atoms along a. Each chain
is separated from neighbouring chains by free water molecules
(Fig. 2).
Figure 1
A projection view of (I) along the b axis, showing the packing of the
in®nite chains. For clarity, water molecules of crystallization and all H
atoms have been omitted.
Acta Cryst. (2003). C59, m277±m279
DOI: 10.1107/S010827010300341X
# 2003 International Union of Crystallography m277

metal-organic compounds
crystallization exhibit high displacement parameters. We
attribute these high parameters to the existence of numerous
hydrogen bonds of comparable importance.
It is interesting to note that the crystal structure of (I)
differs from the La-containing structure already reported by
Wu et al. (1996). The La-containing material was synthesized
by hydrothermal methods, whereas both Y- and Er-containing
compounds have been obtained by slow diffusion in gel media.
Experimental
Mellitic acid was supplied by Aldrich Chemical Company Inc. and the
oxide of erbium was supplied by Rhodia Inc. Both were used without
further puri®cation. By reaction with NaOH, mellitic acid provided
the hexasodium mellitate salt. By reaction with HCl, the erbium
oxide gave the pentahydrated erbium chloride. Dilute aqueous
solutions of ErIII chloride and hexasodium mellitate were allowed to
diffuse slowly through an agar gel medium in a U-shaped tube. After
one and a half months, pale-pink single crystals of (I) were collected.
Analysis calculated (found) for [Er2{C(CO2)6}(H2O)10]Á4H2O: Er 36.3
(36.3), C 15.5 (15.6), H 3.2 (3.0), O 45.3% (45.1%).
Crystal data
Figure 2
3
[Er2(C12O12)(H2O)10]Á4H2O
Dx = 2.444 Mg m
Mo Kꢁ radiation
Cell parameters from 8641
re¯ections
A projection view of (I) along the a axis, showing the packing of the
in®nite chains and the location of the crystallization water molecules,
together with the labelling scheme for the water molecules.
Mr = 922.86
Monoclinic, P21=n
Ê
a = 8.4499 (1) A
ꢂ = 1.0±30.0ꢁ
ꢃ = 6.76 mm
T = 298 (2) K
Ê
b = 9.2595 (2) A
1
Ê
c = 16.2911 (4) A
(the twist angles lie in the range 50±70ꢁ). This twisting ability
of a carboxylate group involved in a rare-earth-containing
coordination polymer has already been reported in both a
terephthalate compound (Reineke et al., 1999) and a
benzenetetracarboxylate compound (Cao et al., 2002).
In addition to the ®ve water molecules in the ®rst coordi-
nation sphere of the Er atoms, two water molecules per Er
atom were re®ned (Fig. 2). This is in accordance with the
results of a thermogravimetric analysis. For the two sets of
sites O1W±O4W and O2W±O3W, a disorder model (0.5:0.5)
was introduced. These water molecules build a complex
network of hydrogen bonding between themselves, the
carboxylate O atoms and the water molecules of the ®rst
coordination sphere. The O atoms from the water molecules of
ꢀ = 100.3390 (8)ꢁ
Ê
V = 1253.95 (4) A
Z = 2
3
Plate, pale pink
0.31 Â 0.09 Â 0.06 mm
Data collection
Nonius KappaCCD area-detector
diffractometer
CCD rotation image scans, thick
slices
Absorption correction: analytical
(Alcock, 1970)
Tmin = 0.256, Tmax = 0.646
17 561 measured re¯ections
Re®nement
Re®nement on F2
R[F2 > 2ꢄ(F2)] = 0.037
wR(F2) = 0.093
S = 1.03
3648 re¯ections
3648 independent re¯ections
2884 re¯ections with I > 2ꢄ(I)
Rint = 0.049
ꢂmax = 30ꢁ
h = 11 ! 9
k = 13 ! 11
l = 21 ! 22
w = 1/[ꢄ2(Fo2) + (0.0438P)2
+ 4.4981P]
where P = (Fo2 + 2Fc2)/3
(Á/ꢄ)max < 0.001
3
Ê
Áꢅmax = 2.48 e A
3
Ê
2.05 e A
199 parameters
H-atom parameters not de®ned
Áꢅmin
=
The s.u. values of the cell constants indicate the internal consis-
tency of the measurements themselves, i.e. the precision of the
measurements, not their accuracy. The maximum peak in the ®nal
Table 1
Selected interatomic distances (A).
Ê
ErÐO31i
ErÐO5
ErÐO21
ErÐO11
2.281 (3)
2.341 (5)
2.343 (3)
2.350 (3)
ErÐO1
ErÐO3
ErÐO4
ErÐO2
2.351 (4)
2.358 (4)
2.362 (5)
2.391 (4)
Figure 3
A projection view of the coordination polyhedron of the ErIII ions in (I),
along with the atomic labelling scheme. Displacement ellipsoids are
drawn at the 50% probability level.
Symmetry code: (i) 1 x; y; z.
ꢀ
m278 Deluzet and Guillou
[Er2(C12O12)(H2O)10]Á4H2O
Acta Cryst. (2003). C59, m277±m279

metal-organic compounds
Ê
Ê
difference map is 2.08 A from O3W and the minimum peak is 0.77 A
from Er.
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Â
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 Â
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ꢀ
Acta Cryst. (2003). C59, m277±m279
Deluzet and Guillou [Er2(C12O12)(H2O)10]Á4H2O m279