metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
these MOFs and, as such, have decided to explore the current
limit of aliphatic chain length that can be incorporated into
these structures. For this effort, we have used sebacic acid
(C10H18O4), a ¯exible aliphatic dicarboxylic acid that is longer
than previously reported for Ln-MOFs. This publication
presents the synthesis, structure and thermal properties of the
title compound, [Nd(C10H16O4)(C10H16O3OH)(H2O)], (I), a
novel Ln-MOF with the longest aliphatic chain length to date.
ISSN 0108-2701
Poly[[aquaneodymium(III)]-l3-
decane-1,10-dicarboxylato-l3-
9-carboxynonanecarboxylato]
Lauren A. Borkowskia and Christopher L. Cahilla,b
*
aDepartment of Chemistry, George Washington University, 725 21st Street NW,
Washington, DC 20052, USA, and bGeophysical Laboratory, Carnegie Institution of
Washington, Washington DC 20015, USA
Correspondence e-mail: cahill@gwu.edu
Received 21 January 2004
Accepted 12 February 2004
Online 11 March 2004
The title compound, [Nd(C10H16O4)(C10H17O4)(H2O)]n, has a
novel Nd±organic framework constructed from sebacic acid
(C10H18O4) linkers, the longest aliphatic ligand used to date in
lanthanide metal±organic framework compounds. The struc-
ture contains edge-shared chains of NdO8(H2O) tricapped
trigonal prisms that propagate in the [100] direction, with
The structure of (I) contains a single crystallographically
unique Nd site, within the coordination sphere of which there
are two modes of bonding for the carboxylic acid (Fig. 1): each
carboxylic acid chain acts as a monodentate ligand at one end
and a bridging tridentate ligand at the other. There is a bound
Ê
water molecule (O9) at a distance of 2.535 (5) A from the Nd
Ê
NdÐO distances in the range 2.414 (4)±2.643 (4) A.
center. Two of the O atoms (O3 and O5) are involved in the
edge-sharing of the NdO8(H2O) polyhedra (Table 1). These O
atoms, with their respective pairs (O4 and O6), form the
bridging tridentate end of each acid. The remaining two O
atoms in the coordination sphere are O1 and O7. Carboxyl
atoms O2 and O8 are not coordinated to Nd but are linked via
an OÐHÁ Á ÁO hydrogen bond (Table 2).
Comment
Metal±organic frameworks (MOFs) have been the subject of
increased study recently, due to their potential for designed
architectures and their unique applicability to separations, gas
storage, molecular recognition and catalysis (Moulton &
Zaworotko, 2001). A subset of these materials are lanthanide-
containing MOFs, the structures of which have the potential
for unique topologies when one considers the rich and vari-
able coordination chemistry of the Ln elements. Furthermore,
the luminescent properties of these compounds, which result
from Ln f±f electronic transitions, are being exploited for
possible sensing applications (Ma et al., 1999).
In the crystal structure of (I), there are edge-shared chains
of NdO8(H2O) tricapped trigonal prisms that propagate in the
[100] direction (Fig. 2). The edge sharing results from a
polymerization of Nd3+ centers through bridging tridentate
carboxylate groups on the sebacic acid molecules. The overall
topology is thus a three-dimensional framework, as these
chains are then crosslinked to each other by the difunctional
acid groups.
A representative survey of Ln-MOFs with aliphatic
carboxylate linkers reported since 1998 reveals some recurring
structural features with respect to the building units of these
materials (Dimos et al., 2002; Gøowiak et al., 1986; Kim et al.,
2004; Kiritsis et al., 1998; Michaelides et al., 2003; Serpaggi &
Ferey, 1998; Vaidhyanathan et al., 2002). For example, many
Ln-MOFs contain zero-dimensional Ln building units or
isolated metal centers. That is, a single Ln ion (or at most a
dimer) is coordinated to multifunctional organic linkers and/
or water molecules to form the extended framework struc-
tures. Less common are one-dimensional chains of Ln poly-
hedra which are in turn crosslinked to form framework
topologies.
One interesting aspect of Ln-MOFs is their thermal stability
and retention of crystallinity once dehydrated (Reineke et al.,
1999). Thermogravimetric analysis of (I) reveals a weight loss
of approximately 3% between 383 and 423 K (dehydration;
loss of bound H2O group), followed by the complete break-
down of the structure beginning at 478 K. When compared
with other Ln-MOFs, (I) appears to be less robust, presumably
as a result of the acid chain length. Brzyska & Ozga (1991)
have reported that Ln±sebacic acid complexes are stable up to
approximately 553 K, but the structures of these compounds
were not reported. Despite a low decomposition temperature,
compound (I) does retain its crystalline structure upon
dehydration at 423 K, as noted by a very similar powder
diffraction pattern of the dehydrated material. The absence of
H2O (O9) was con®rmed by IR spectroscopy.
We are concerned with understanding the principles of what
factors in¯uence the dimensionality of the Ln building units of
Acta Cryst. (2004). C60, m159±m161
DOI: 10.1107/S0108270104003427
# 2004 International Union of Crystallography m159
Borkowski, Lauren A.
