Rational design and crystal structure determination of a 3-D metal-organic jungle-gym-like open framework

Article abstract of DOI:10.1021/ic049005d

A new three-dimensional (3-D) jungle-gym-like open metal-organic framework has been synthesized from a two-dimensional (2-D) layer compound using a heterogeneous pillar insertion reaction. Both the starting 2-D layer and the resulting 3-D open compounds have been characterized using X-ray crystallography.

Full text of DOI:10.1021/ic049005d

Inorg. Chem. 2004, 43, 6522−6524
Rational Design and Crystal Structure Determination of a 3-D
Metal Organic Jungle-Gym-like Open Framework
−
Ryo Kitaura,†,‡ Fumiyasu Iwahori,§ Ryotaro Matsuda,† Susumu Kitagawa,*,† Yoshiki Kubota,|
Masaki Takata, and Tatsuo C. KobayashiO
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering,
Kyoto UniVersity, Katsura, Nisikyo-ku, Kyoto 615-8510, Japan, Department of Chemistry,
School of Science and Engineering, Aoyama-Gakuin UniVersity, 5-10-1 Fuchinobe, Sagamihara,
Kanagawa 229-8558, Japan, Department of Natural Science, Osaka Women’s UniVersity, Sakai,
Osaka 590-0035, Japan, Japan Synchrotron Radiation Research Institute, Kouto, Mikazuki, Sayo,
Hyogo 679-5198, Japan, and Department of Physics, Okayama UniVersity Tsushima-naka,
Okayama 700-8530, Japan
Received July 23, 2004
A new three-dimensional (3-D) jungle-gym-like open metal−organic
framework has been synthesized from a two-dimensional (2-D)
layer compound using a heterogeneous pillar insertion reaction.
Both the starting 2-D layer and the resulting 3-D open compounds
have been characterized using X-ray crystallography.
Figure 1. Schematic representation of a construction of 3-D porous
framework by a pillar insertion strategy.
A new class of porous materials, known as coordination
polymers, which are constructed from transition metal ions
and organic bridging ligands, have attracted a great deal of
attention recently,1 and a great deal of research effort has
been devoted to the development, design, and synthesis of
novel high porous metal-organic frameworks. One of the
most rational methods used for the construction of three-
dimensional (3-D) porous frameworks is to insert pillar
moieties between the layers of two-dimensional (2-D) layered
compounds (Figure 1).
This strategy has already been successfully used in
inorganic compounds, resulting in many pillared layer porous
materials being synthesized, such as pillared montmorillonite
and smectite.2 On the other hand, the number of coordination
compounds designed using this strategy is still low.3 Re-
cently, a series of 3-D CuII-dicarboxylate-dabco (where
dabco ) 1,4-diazabicyclo[2.2.2]octane) coordination frame-
works, which exhibit an exceptionally high methane storage
capacity, have been synthesized using a pillar insertion
strategy.4 However, due to difficulties in achieving crystal-
lization and in structural characterization, the crystal struc-
tures of both the starting 2-D layer compounds and the
resulting 3-D framework compounds have not been eluci-
dated. In this paper, we report on the synthesis and
determination of the crystal structure of novel 2-D and 3-D
CuII-dicarboxylate coordination frameworks, hereafter re-
ferred to as 2-D and 3-D frameworks 1 and 2, respectively.
The 3-D framework, [Cu(tfbdc)(dabco)0.5] (2), was prepared
by a heterogeneous pillar insertion reaction of [Cu(tfbdc)-
(MeOH)] (1), in which tfbdc ) tetrafluorobenzene-1,4-
dicarboxylate and the pillar ligand ) dabco. This pillar
insertion reaction involves a sliding of the 2-D layers,
resulting in a considerable increase in the channel size and
* To whom correspondence should be addressed. E-mail: kitagawa@
sbchem.kyoto-u.ac.jp.
† Kyoto University.
‡ Current Address: Toyota Central R&D Laboratories, Inc., Nagakute,
Aichi 480-1192, Japan.
§ Aoyama-Gakuin University.
| Osaka Women’s University.
(2) (a) Ohtsuka, K. Chem. Mater. 1997, 9, 2039. (b) Cheng, S.; Wang,
T.-C. Inorg. Chem. 1989, 28, 1283. (c) Anderson, M. W.; Klinowski,
J. Inorg. Chem. 1990, 29, 3260. (d) Pinnavaia, T. J.; Tzou, M.-S.;
Landau, S. D. J. Am. Chem. Soc. 1985, 107, 4783.
(3) (a) Alberti, G.; Murcia-Mascaros, S.; Vivani, R. J. Am. Chem. Soc.
1998, 120, 9291S. (b) Kitagawa; Kitaura, R. Comments Inorg. Chem.
2002, 23, 101. (c) Evans, O. R.; Lin, W. Inorg. Chem. 2000, 39, 2189.
(d) Lin, W.; Evans, O. R.; Yee, G. T. J. Solid State Chem. 2000, 152,
152.
Japan Synchrotron Radiation Research Institute.
O Okayama University.
(1) (a) Kitagawa, S.; Kitaura, R.; Noro, S. Angew. Chem., Int. Ed. 2004,
43, 2334. (b) Eddaoudi, M.; Moler, D. B.; Li, H.; Chen, B.; Reineke,
T. M.; O’Keeffe, M.; Yaghi, O. M. Acc. Chem. Res. 2001, 34, 319.
(c) Moulton, B.; Zaworotko, M. J. Chem. ReV. 2001, 101, 1629. (d)
Hagrman, D.; Hagrman, P. J.; Zubieta, J. Angew. Chem., Int. Ed. 1999,
38, 3165. (e) Kitaura, R.; Seki, K.; Akiyama, G.; Kitagawa, S. Angew.
Chem., Int. Ed. 2003, 428. (f) Pan, L.; Liu, H.; Lei, X.; Huang, X.;
Olson, D.; Turro, N.; Li, J. Angew. Chem., Int. Ed. 2003, 542.
(4) (a) Seki, K.; Mori, W. J. Phys. Chem. B 2002, 106, 1380. (b) Seki, K.
Chem. Commun. 2001, 1496
6522 Inorganic Chemistry, Vol. 43, No. 21, 2004
10.1021/ic049005d CCC: $27.50
© 2004 American Chemical Society
Published on Web 09/21/2004

COMMUNICATION
Figure 2. Crystal structure of 1. (a) Paddle-wheel CuII building unit of 1.
(b) 2-D grid layer of 1. The neighboring layer is drawn as black line. H
atoms are omitted for clarity (Cu, orange; F, light blue; O, red; C, gray).
pore volume dimensions. The repulsion between the F atoms
probably facilitates this reaction.
Figure 3. Synchrotron X-ray powder diffraction pattern of 2, and the final
result of Rietveld fitting.
Compound 1 was prepared by reacting Cu(HCOO)2‚4H2O
and H2tfbdc in MeOH/EtOH at T ) 298 K. One of the green,
plate-shaped crystals formed was chosen for the X-ray
crystallography studies.5 Figure 2 displays the crystal struc-
ture of 1, showing the paddle-wheel-like clusters of CuII ions
with axial MeOH ligands (Figure 2a) that are bridged by
tfbdc ligands to form 2-D infinite layers. These layers form
in a square grid configuration, with dimensions of 10.87 ×
10.87 Å2 (Figure 2b). These layers are stacked alternately,
so that the paddle wheel CuII clusters of neighboring 2-D
layers are located in the middle of the grid layer (i.e., an
ABAB mode, see Figure 2b).
This results in there being no cavities large enough to
accommodate any guest molecules (as the channel dimen-
sions are ca. 3.8 × 3.1 Å2, the only possible guest molecule
candidates are He and H2). The benzene rings of the tfbdc
ligands are highly tilted against the ac-plane with a dihedral
angle of 115.9°, which is attributed to the repulsion between
F atoms of neighboring 2-D layers, and from the steric
hindrance between the F atoms and carboxylate oxygen
atoms. Compound 1 is not soluble in common organic
solvents, such as MeOH, EtOH, and THF.
transparence. This degradation is attributed to structural
changes in the crystals arising from the pillar insertion
reaction. Single crystals are able to endure this type of drastic
structural change, resulting in the degradation of the crystal
transparence. To elucidate the crystal structure of 2, we
performed synchrotron X-ray powder diffraction measure-
ments at the SPring-8, BL02B2 synchrotron facility in Japan.6
Figure 3 shows the powder diffraction pattern of 2 and the
result of the final Rietveld fitting.
The reliability factors based on the powder pattern, Rwp,
and the integrated intensities, RI, were 3.04% and 3.75%,
respectively.7 Compared with 1, both the cell parameters and
the space group were drastically changed after the reaction
(1 ) monoclinic, C2/m, a ) 15.139 Å, b ) 15.426 Å, c )
10.676 Å, and â ) 131.27°, and 2 ) tetragonal, P4/mmm,
a ) 10.866 Å, c ) 9.6705 Å). Figure 4a,b shows the crystal
structure of 2 looking down the c- and a-axes, respectively.
Two-dimensional grid layers constructed by the CuII ions
and the tfbdc groups are linked by dabco groups to form a
3-D jungle-gym-like open framework. The dihedral angle
between the benzene rings and the ac-plane decreased from
Compound 2 was prepared by the heterogeneous reaction
of compound 1 with dabco in MeOH at T ) 373 K in a
stainless reaction vessel. (Although we confirmed that this
reaction proceeds at ambient temperature, a high reaction
temperature of T ) 373 K was utilized to speed up the
reaction.) During the reaction, the color of the crystals
changed from green to yellow-green, but the crystal mor-
phology did not alter with the slight change in crystal
(6) (a) Nishibori, E.; Takata, M.; Kato, K.; Sakata, M.; Kubota, Y.; Aoyagi,
S.; Kuroiwa, Y.; Yamakata, M.; Ikeda, N. J. Phys. Chem. Solids 2001,
62, 2095. (b) Kitaura, R.; Kitagawa, S.; Kubota, Y.; Kobayashi, T.;
Kindo, K.; Mita, Y.; Matsuo, A.; Kobayashi, M.; Chang, H.; Ozawa,
T.; Suzuki, M.; Sakata, M.; Takata, M. Science 2002, 298, 2361.
(7) The crystal structure determination of 2 was carried out from
synchrotron X-ray powder diffraction data. Data collection was
performed using a Debye-Scherrer camera and imaging plate as a
detector at SPring-8, BL02B2. The powder crystal was sealed in the
glass capillary (0.4 mm inside diameter). Cell parameters were
determined by indexing program DICVOL91.8 A Le Bail structureless
profile fitting algorithm affords refined cell parameters, peak shift
parameters, and profile parameters. The peak shape was modeled by
a Split-Pearson function. The structure refinement was performed
by the Rietveld method with RIETAN software.9 Soft constraints about
bond angles and bond distances were adapted throughout the refine-
ment. Hydrogen atoms were placed at calculated positions, and their
parameters were not refined. Crystallographic data for 2: C11F4H6O4-
Cu, M ) 341.70, λ ) 0.90229 Å, tetragonal, space group P4/mmm
(No. 123), a ) 10.8661(1) Å, c ) 9.6703(5) Å, U ) 1141.79(6) Å3,
Z ) 2, T ) 298 K, 2θmin ) 2.4°, 2θmax ) 50.0°, step size 0.1°, number
of reflections ) 337, Rwp ) 0.0304, RI ) 0.0375. These data are
available from the Crystallographic Data Centre as supplementary
publication CCDC-236931. Copies of the data can be obtained
free of charge on application to CCDC, 12 Union Road, Cam-
bridge CB21EZ, U.K. (Fax: (+44)1223-336-033. E-mail: deposit@
ccdc.cam.ac.uk.)
(5) Data collection for a green plate single crystal of 1 was performed on
a Rigaku mercury charge coupled device (CCD) system using graphite-
monochromatized Mo KR radiation (λ ) 0.71073) at 298 K. The
structure was solved by direct methods and refined by full-matrix least-
squares methods with the teXsan crystallographic software package
from Molecular Sructure Corporation. Hydrogen atoms were placed
at calculated positions, and their parameters were not refined.
Crystallographic data for 1: C9F4H4O5Cu, M ) 335.70, monoclinic,
space group C2/m (No. 12), a ) 15.139(4) Å, b ) 15.426(9) Å, c )
10.676(1) Å, and â ) 131.270(3)°, U ) 1873(1) Å3, Z ) 4, Fcalcd
)
1.190 g‚cm-3, 2θmax ) 54.18°, 1962 reflections measured, 1297
observed (I > 3.00 σ(I)), 91 parameters, R ) 0.0776, Rw ) 0.0841.
These data are available from the Crystallographic Data Centre as
supplementary publication CCDC-235831. Copies of the data can be
obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB21EZ, U.K. (Fax: (+44)1223-336-033. E-mail: deposit@
ccdc.cam.ac.uk.)
Inorganic Chemistry, Vol. 43, No. 21, 2004 6523

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m2/g, respectively (using a sphere with diameter of 3.0 Å).10
No guest molecules were found in the channels of 2, probably
due to disorder in the guest molecules. This type of 3-D open
framework has been reported before, but this is the first
characterization of such a compound’s crystal structure using
X-ray crystallography.
Interestingly, the sliding of the 2-D layers during the
heterogeneous pillar insertion reaction resulted in a drastic
change of stacking mode of the 2-D layers from the ABAB
mode to a nonoffset mode. This probably is associated with
the repulsion between the F atoms, which facilitates the
sliding of the 2-D layers. This framework is stable and retains
its original structure after desolvation, which was confirmed
by X-ray diffraction measurements under reduced pressure
at higher temperatures.
Figure 4. Crystal structure of 2 with CPK model: (a) down from c-axis,
(b) down from b-axis. H atoms and disordered atoms are omitted for clarity
(Cu, orange; F, light blue; O, red; C, gray).
In conclusion, we have succeeded in synthesizing novel
fluorinated 3-D open frameworks11 using a heterogeneous
pillar insertion reaction that involved the sliding of the 2-D
layers, and we have successfully characterized their structure
using single crystal and synchrotron X-ray powder crystal-
lography.
Acknowledgment. We acknowledge experimental sup-
port at SPring-8 from Mr. Kenichi Kato and Miss Megumi
Suzuki. This work was supported by a Grant-in-Aid for
Science Research in a Priority Area “Chemistry of Coordina-
tion Space” (No. 434) from the Ministry of Education,
Science, Sports, and Culture, Japan.
Figure 5. A stick representation of the crystal structure of 2 with accessible
3-D interconnected open channel along the c-axis, which is shown as a
white surface (Cu, orange; F, light blue; O, red; C, gray).
Supporting Information Available: Crystallographic data in
CIF format. This material is available free of charge via the Internet
at http://pubs.acs.org.
115.9° to 35.8°. This results from the increase in distance
between the 2-D layers, as induced by the pillar insertion
reaction. Figure 5 shows the solvent-accessible pore surface,
which is defined by the possible surface of a rolling sphere
with a diameter ) 3.0 Å.
As illustrated in Figure 5, 3-D interconnected channels
exist, and their dimensions looking down the c- and a-axis
are approximately 6.3 × 6.3 and 3.5 × 4.7 Å2, respectively.
The calculated solvent-accessible pore volume and surface
area are 0.54 cm3/g (0.55% of unit cell volume) and 2020
IC049005D
(8) Boultif, A.; Louer, D. J. Appl. Crystallogr. 1991, 24, 987.
(9) Izumi, F.; Ikeda, T. Mater. Sci. Forum 2000, 198, 321.
(10) We performed a Monte Carlo integration calculation to evaluate the
pore volume and surface area accessible to guest molecules. Note that
the surface area depends on the size of the probe molecules. In this
study, a probe molecule is a sphere of 3.0 Å diameter.
(11) (a) Pan, L.; Sander, M.; Huang, X.; Li, J.; Smith, M.; Bittner, E.;
Bockrath, B.; Johnson, J. J. Am. Chem. Soc. 2004, 126, 1308. (b) Kasai,
K.; Aoyaghi, M.; Fujita, M. J. Am. Chem. Soc. 2000, 122, 2140.
6524 Inorganic Chemistry, Vol. 43, No. 21, 2004