metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
coordination polymer comprised of an isophthalic acid
complex of ZnII.
Communications
ISSN 0108-2701
Aqua(benzene-1,3-dicarboxylato)-
zinc(II)
The asymmetric unit of (I) contains a Zn atom, one
isophthalate group, and one coordinated water molecule. Fig.
1 shows the local coordination environment around the Zn
center as a distorted tetrahedron (Table 1) comprised of one
water molecule and three bridging isophthalate carboxylate O
atoms. This geometric pattern is consistent with other ZnII
coordination frameworks reported in the literature (Mehrota
& Bohra, 1983; Robl, 1987b). Each Zn atom coordinates to six
Thomas J. Otto and Kraig A. Wheeler*
Department of Chemistry, Delaware State University, Dover, DE 19901, USA
Correspondence e-mail: kwheeler@dsc.edu
Received 11 December 2000
Accepted 16 March 2001
adjacent Zn centers [shortest distance is ZnÁ Á ÁZnvi
=
4.3323 (3) A; symmetry code: (vi) 12 + x, 1 y, z] through the
bridging isophthalate atoms O1, O2, and O3 to give a planar
polymeric network in the ac plane (Fig. 2). The two-dimen-
sional architecture is constructed of Zn atoms linked by
bidentate carboxylate groups, O1 and O2, along the a axis.
This motif is extended along the c axis by monodentate
chelation of the remaining carboxylate group to adjacent Zn
centers via O3ÐZn interactions.
The title compound, poly[[aquazinc(II)]-ꢀ-benzene-1,3-di-
Ê
0
carboxylato-O1:O1 :O2], [Zn(C8H4O4)(H2O)]n, forms
a
metal±organic coordination network that consists of tetra-
hedral Zn atoms bonded to one water molecule and three
carboxylate groups. Isophthalate groups bridge the four-
coordinate Zn centers to generate two-dimensional architec-
tures in the ac plane. These planar zinc isophthalate motifs are
linked by in®nite C OÁ Á ÁHÐOÐH interactions along the a
axis to form a chiral framework. The observed polar structural
pattern originates due to the distorted tetrahedral Zn centers
[OÐZnÐO 100.7 (2)±136.0 (1)ꢁ] and the alignment of the
water molecules. Bridging isophthalate groups align to form
approximate centrosymmetric motifs.
A
noteworthy feature is that the non-coordinated
carboxylate O4 atom forms in®nite chains of undulating O5Ð
HÁ Á ÁO4 hydrogen bonds with neighboring chelated water
molecules (Fig. 2 and Table 2). This pattern extends along the
a axis and links the two-dimensional isophthalate±ZnII coor-
dination networks. The resulting three-dimensional assem-
blage, constructed from polymeric Zn centers and catemeric
hydrogen bonds, lacks residual solvent-accessible regions, as
determined from an examination of the structure with
PLATON (Spek, 1990).
Comment
A considerable number of reports based on metal±organic
coordination polymers have appeared over the past few
decades. Constructed of catenary ligands bonded to metal
centers, these materials have successfully been used to
generate desired crystalline architectures with bulk functions
(Biradha et al., 1999; Evans & Lin, 2000; Mori & Takamizawa,
2000). The use of metal centers with relatively robust coor-
dination environments and conformationally rigid ligands
often produces frameworks with structural preferences. ZnII
carboxylates are one such example that form predictable
metal-center geometries which can be linked through multi-
dentate bridging ligands (Li et al., 1998; Lin et al., 1999; Robl,
1987a). The development of new materials based on metal±
organic frameworks requires an understanding of structural
biases resulting from the self-assembly of the fundamental
components. While many of the principles responsible for the
construction of coordination polymers have been exposed
The chiral framework of the structure originates from the
distorted tetrahedral Zn centers and polar alignment of the
chelated water molecules. Inspection of Table 1 reveals ZnÐO
Ê
bonds that differ by only 0.030 (3) A, with signi®cant varia-
tions in the OÐZnÐO angles [100.7 (2)±136.0 (1)ꢁ]. The
skewed coordination environment of each Zn atom generates
a stereogenic metal center with vectorial properties that are
not cancelled by the orientation of neighboring symmetry-
È
(Aakeroy et al., 2000; Guilera & Steed, 1999; Saalfrank et al.,
1999), a uni®ed set of criteria that describes speci®c crystal-
packing arrangements remains relatively undiscovered. Since
steps towards clarifying structural principles often follow a
rational study of the extant crystallographic data, the addition
of new structures to this database serves to support or chal-
lenge existing structural principles. Here, we describe the
synthetic and structural chemistry of the title compound, (I), a
Figure 1
The ZnII coordination environment in (I) and the atom-labeling scheme.
Displacement ellipsoids are shown at the 60% probability level and H
atoms are drawn as small spheres of arbitrary radii [symmetry codes: (i)
x, y, 12 + z; (ii) 1 x, 1 y, 12 + z].
3
2
ꢀ
704 # 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2001). C57, 704±705
Otto
