A polar luminescent Zn polymer containing an unusual noninterpenetrated utp net

Article abstract of DOI:10.1021/ic060276t

A new Zn coordination polymer with the mixed ligands of 1,3,5-benzenetricarboxylate and 1,3-bis(4-pyridyl)propane has been hydrothermally synthesized, and an unusual distorted noninterpenetrated utp [or (10,3)-d] net has been defined.

Full text of DOI:10.1021/ic060276t

Inorg. Chem. 2006, 45, 3161−3163
A Polar Luminescent Zn Polymer Containing an Unusual
Noninterpenetrated utp Net
Jian Zhang,†,‡ Yu-Biao Chen,† Shu-Mei Chen,† Zhao-Ji Li,† Jian-Kai Cheng,† and Yuan-Gen Yao*,†
The State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of
Matter, The Chinese Academy of Sciences, Fuzhou, Fujian 350002, People’s Republic of China,
and Graduate School of the Chinese Academy of Sciences,
Bejing 100039, People’s Republic of China
Received February 17, 2006
A new Zn coordination polymer with the mixed ligands of 1,3,5-
benzenetricarboxylate and 1,3-bis(4-pyridyl)propane has been
hydrothermally synthesized, and an unusual distorted noninter-
penetrated utp [or (10,3)-d] net has been defined.
nized networks (i.e., CdSO4,5 NbO,6 SrAl2,7 quartz,8 dual
quartz,9 moganite10) have been enumerated or identified.
Among these structures, the three-connected (10,3) nets are
particularly interesting because many of them have large
voids and channels inside the frameworks and they can be
chiral in many cases.11 Up to now, more than 12 different
(10,3) nets have already been defined by Wells3a,b and Koch
and Fischer.12 The (10,3)-d (or utp) net is special in some
sense compared to the chiral higher symmetry (10,3)-a (srs).
Although it resembles a (10,3)-a net in the sense that it has
4-fold helices, these are alternating left- and right-handed
and the whole net is therefore racemic. To our knowledge,
of the utp type, there are currently only three known
examples assigned in the papers. Two H-bonded complexes
In the past decade, the remarkable progress in crystal
engineering has provided a wide range of coordination
polymers with potential applications as functional solid
materials and new topologies.1 Analysis of the network
topology has proven to be a useful tool in the design and
interrogation of crystal structures.2,3 Recently, some new
topologies [i.e. (8,4)4] and many of the previously unrecog-
* To whom correspondence should be addressed. E-mail:
yyg@fjirsm.ac.cn.
{resorcinol13a and [Co(2,2′-biimidazole)3]‚0.5DMF‚0.8H2O13b
}
† Fujian Institute of Research on the Structure of Matter, The Chinese
Academy of Sciences.
and a 3D polymer [Co(NO3)(1,4-bis(3-pyridyl)-2,3-diaza-
1,3-butadiene)1.5]‚H2O13c represent this topology. Both of the
two metal coordination complexes exhibit an interpenetrated
‡ Graduate School of the Chinese Academy of Sciences.
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10.1021/ic060276t CCC: $33.50
Published on Web 03/24/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 8, 2006 3161

COMMUNICATION
Figure 1. ORTEP drawing of the molecular structure of complex 1.
1
Symmetry codes: (a) -x, -1 - y, -1/2 + z; (b) /2 + x, -3/2 - y, z; (c)
1
-1/2 + x, -3/2 - y, z; (d) -x, -1 - y, /2 + z.
utp net. However, a coordination polymer with a noninter-
penetrated utp net has not been reported to date.
As a highly symmetric triangular ligand, 1,3,5-benzene-
tricarboxylate (BTC) is a good selection for the construction
of a (10,3) net. A self-assembly reaction of BTC and Zn-
(NO3)2 gives a chiral complex [Zn2(BTC)(NO3)](H2O)(C2H5-
OH)5 with a srs net.14 Our strategy is based upon the
coordination of a d-block metal (ZnII) with the BTC ligand
and a long but flexible ligand 1,3-bis(4-pyridyl)propane
(BPP) as the auxiliary (second) ligand.15 As the BPP ligand
was added to the Zn-BTC system, the reticular construction
was changed drastically. In this Communication, we describe
an unusual distorted noninterpenetrated utp net in a ZnII
metal-organic polymer [Zn(BTC)(HBPP)]n‚nH2O (1).
Complex 1 was hydrothermally synthesized at 160 °C.16
The structure of the complex was identified by satisfactory
elemental analysis, IR, and X-ray diffraction.17 X-ray dif-
fraction of the complex indicates that it crystallized in
noncentrosymmetric space group Pna21. Its Fourier transform
IR spectrum showed the expected absorptions for the
symmetric and asymmetric vibrations of BTC (1632 and
1435 cm-1) and a H-bonded water (3419 cm-1). It showed
no absorptions for any protonated BTC (1730-1690 cm-1),
indicating the complete deprotonation of H3BTC.
Figure 2. Top: view of the 1D helix-encapsulated BPP ligands. Bottom:
packing diagram of complex 1, showing the large channels along the b
axis and the orientation of the BPP ligands.
The crystal structure of 1 is illustrated in Figure 1. Each
BTC ligand bridges three ZnII ions in a trigonal-planar
fashion by its three carboxylate groups in the monodentate
mode [Zn-O ) 1.923(5), 1.948(5) and 1.951(4) Å, respec-
tively]. Each Zn atom locates at the center of a distorted
tetrahedral geometry with three O donors from three
individual carboxylate groups and one N donor from the
terminal BPP ligand [Zn-N ) 2.063(6) Å]. While one of
the two BPP pyridyl groups is protonated, the auxiliary BPP
ligand does not bridge ZnII ions in the net. The BTC ligand
adopts two carboxylate groups to link the Zn centers to give
a 1D cylindrical 61 helix in the b direction (Figure 2). The
Zn-Zn distances bridged by BTC are in the range of 8.15-
10.64 Å, and the repeating period in the helical column is
about 7.89 Å. The diameter of the helical column is about
11.22 Å. Each helical column is occupied by a BPP ligand.
The uncoordinated pyridine ring of the BPP ligand is parallel
to the benzene ring of the BTC ligand, but no interactions
are found between them. From another point of view, it is
the BPP ligand that molds the formation of such a helix.
The third carboxylate group of the BTC ligand binds to the
unsaturated site of the Zn center of other helices, resulting
in the final 3D architecture. Because of the presence of large
template BPP ligands, no interpenetrated phenomenon is
found. Another interesting feature of the complex is that all
uncoordinated ends of the BPP ligands are extended to the
same direction, so no center of inversion can be found and
the whole framework is polar.
(14) Yaghi, O. M.; Davis, C. E.; Li, G. M.; Li, H. L. J. Am. Chem. Soc.
1997, 119, 2861.
(15) (a) Wen, Y.-H.; Zhang, J.; Wang, X.-Q.; Feng, Y.-L.; Cheng, J.-K.;
Li, Z.-J.; Yao, Y.-G. New J. Chem. 2005, 29, 995. (b) Almeida Paz,
F. A.; Klinowski, J. Inorg. Chem. 2004, 43, 3882. (c) Dai, J. C.; Wu,
X. T.; Hu, S. M.; Fu, Z. Y.; Zhang, J. J.; Du, W. X.; Zhang, H. H.;
Sun, R. Q. Eur. J. Inorg. Chem. 2004, 2096. (d) Luo, J. H.; Hong, M.
C.; Wang, R. H.; Cao, R.; Han, L.; Lin, Z. Z. Eur. J. Inorg. Chem.
2003, 2705. (e) Li, X. J.; Cao, R.; Sun, D. F.; Bi, W. H.; Wang, Y.
Q.; Li, X.; Hong, M. C. Cryst. Growth Des. 2004, 4, 775.
(16) A mixture of ZnSO4‚7H2O (0.287 g, 1.0 mmol), BPP (0.198 g, 1.0
mmol), benzene-1,3,5-tricarboxylate acid (0.105 g, 0.5 mmol) with
NaOH (0.040 g, 1.0 mmol), and 15 mL of water was placed in a Parr
Teflon-lined stainless steel vessel (25 cm3), and then the vessel was
sealed and heated to 160 °C. The temperature was held for 3 days,
and then the reactant mixture was cooled at a rate of 0.5 °C min-1 to
lead to the formation of colorless crystals of 1 (yield ) about 35%
based on Zn; final pH ) 5.2). Anal. Calcd for 1: C, 53.95; H, 4.12;
N, 5.72. Found: C, 53.99; H, 4.22; N, 5.69. IR (solid KBr pellet,
v/cm-1) for complex 1: 3419 (m), 1633 (vs), 1567 (m), 1435 (s),
1366 (s), 1227 (m), 1099 (w), 1030(m), 767 (s), 718 (s), 615 (w).
(17) Crystal data for 1: C22H20N2O7Zn, Mr ) 489.77, colorless crystal (0.25
× 0.20 × 0.15 mm), orthorhombic, space group Pna21, a ) 19.0972-
(12) Å, b ) 7.8864(5) Å, c ) 13.7586(8) Å, V ) 2072.2(2) Å3, Z )
4, T ) 293(2) K, Fcalcd ) 1.570 g cm-1, F(000) ) 1008, µ ) 1.234
mm-1, Flack ) 0.04(2), R1(wR2) ) 0.0460 (0.1228), and S ) 1.026
for 2318 reflections with I > 2σ(I).
If BPP ligands are ommited, the Zn atom can be looked
at as a three-coordinate nonplanar node with triangular-
pyramidal geometry. Because the BTC ligand can be looked
at as a planar three-coordinate node, the whole network can
3162 Inorganic Chemistry, Vol. 45, No. 8, 2006

COMMUNICATION
Figure 4. Fluorescent excitation (dashed line) and emission (red line)
spectra of complex 1 in the solid state at room temperature.
Complex 1 is totally transparent in the visible region and
insoluble in common solvents. The powder second-harmonic
generation (SHG) measurements18 of complex 1 (the powders
were from crystals) were carried out in a manner similar to
that described by Kurtz at λ ) 1064 nm. It has a SHG of
about 2 times as large as that of potassium dihydrogen
phosphate, which confirms its nonlinear optical behavior and
validates the noncentrosymmetric space group.
Figure 3. Schematic representation of the (10,3) net in 1 along the a, b,
and c axes. Highlighted are a single helix (yellow) and three 10-membered
shortest circuits (purple). The handedness of some helices is illustrated as
red arrows, and the center dot defines the direction as out of the page.
Preliminary fluorescence measurements in the solid state
of 1 showed a broad band with a maximum at 440 nm when
irradiated at 320 nm at room temperature (Figure 4). The
intense emissions for the BTC ligands occur at 370 nm (λex
) 334 nm). A similar emission band at about 430 nm has
also been observed previously for other zinc organic polymer
compounds with either photoluminescent or nonphotolumi-
nescent ligands. Therefore, this emission may not be related
to the π* f n transition of the ligands but simply arises
from the charge-transfer transition.19
thus be represented topologically by two types of three-
coordinate nodes (triangular-pyramidal and trigonal-planar
nodes, respectively). The whole structure can be extended
to an unusual (10,3) net, as displayed in Figure 3. The
extended Schla¨fli symbol of this net is 102.104.104, which is
assigned to the utp net. One triangular-pyramidal node links
three planar nodes, and the angles between the three planes
are 21.37°, 51.54°, and 56.41°, respectively. An interesting
feature of this (10,3) net is the presence of parallel single
helices running through the structure, as highlighted in Figure
3a. This net is constructed by hexagonal helices along the b
axis. Each hexagonal helix connects to six adjacent helices
by sharing a common edge. Because the right- and left-
handed helices are alternatively arranged, the whole net is
therefore racemic. The present net is strongly distorted. It
differs from the regular utp net in the following three
aspects: (i) It contains two type of nodes and cannot be
classified as either a “regular” net [all vertexes, edges, and
angles are equivalent (related by symmetry)] or a “quasi-
regular” net [all vertexes and edges (but not angles) are
equivalent]. (ii) Because of the presence of the triangular-
pyramidal node, the 41 helical deposition in the regular utp
net is lowered to 21 helical deposition. (iii) The space group
of the most symmetrical configuration of the utp net is Pnna,
which is different from the noncentrosymmetric space group
Pna21 of complex 1.
In summary, we have defined an unusual distorted
noninterpenetrated utp net based on Zn coordination with
the mixed ligands of BTC and BPP. The present results
demonstrate that the template effect of the auxiliary ligand
plays an important role in the construction of novel topologi-
cal nets.
Acknowledgment. This work was supported by the
National Natural Science Foundation of China under Project
20173063, YIF of Fujian Province (Project 2005J060), the
Major Special Foundation of Fujian Province (Project
2005H201-1), and the NSF of Fujian Province (Project
E0020001).
Supporting Information Available: The TGA diagram of
complex 1 and X-ray crystallographic file in CIF format. This
material is available free of charge via the Internet at http://
pubs.acs.org.
Thermogravimetric analysis (TGA) of 1 was performed
in a N2 atmosphere when it was heated to 800 °C at a rate
of 10 °C min-1. The TGA diagram of 1 indicates two main
steps of weight losses (Figure S1 in the Supporting Informa-
tion). The weight loss begins at 50 °C and is completed at
160 °C. The observed weight loss of 3.68% corresponds to
the loss of the water molecules (calcd 3.67%). The frame-
work [Zn(BTC)(HBPP)]n is stable up to 340 °C, and then
decomposition starts.
IC060276T
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Inorganic Chemistry, Vol. 45, No. 8, 2006 3163