Microporous material based on π-π Stacking of 1,4-bis(3,6- diphenylpyridazin-4-yl)benzene

Article abstract of DOI:10.1080/15421400600788708

A microporous material constructed by π-π interaction of a twisted H-shape poly-aromatic molecule, 1,4-bis(3,6-diphenylpyridazin-4-yl)benzene (1) was synthesized and X-ray quality crystals were isolated. The intermolecular distances between the various ar

Full text of DOI:10.1080/15421400600788708

This article was downloaded by: [Pennsylvania State University]
On: 08 October 2013, At: 12:19
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Molecular Crystals and Liquid
Crystals
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/gmcl20
Microporous Material Based
on π-π Stacking of 1,4-
Bis(3,6-diphenylpyridazin-4-
yl)benzene
Hsien-Chang Kao a , Shang-Wei Tang a , Jau-Shuenn
Wang a & Wen-Jwu Wang a
a Department of Chemistry , Tamkang University ,
Tamsui, Taipei, Taiwan (ROC)
Published online: 21 Dec 2006.
To cite this article: Hsien-Chang Kao , Shang-Wei Tang , Jau-Shuenn Wang &
Wen-Jwu Wang (2006) Microporous Material Based on π-π Stacking of 1,4-Bis(3,6-
diphenylpyridazin-4-yl)benzene, Molecular Crystals and Liquid Crystals, 456:1,
193-200, DOI: 10.1080/15421400600788708
To link to this article: http://dx.doi.org/10.1080/15421400600788708
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the
information (the “Content”) contained in the publications on our platform.
However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness,
or suitability for any purpose of the Content. Any opinions and views
expressed in this publication are the opinions and views of the authors, and
are not the views of or endorsed by Taylor & Francis. The accuracy of the
Content should not be relied upon and should be independently verified with
primary sources of information. Taylor and Francis shall not be liable for any
losses, actions, claims, proceedings, demands, costs, expenses, damages,
and other liabilities whatsoever or howsoever caused arising directly or

indirectly in connection with, in relation to or arising out of the use of the
Content.
This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden. Terms & Conditions of access and use can be found at
http://www.tandfonline.com/page/terms-and-conditions

Mol. Cryst. Liq. Cryst., Vol. 456, pp. 193–200, 2006
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400600788708
Microporous Material Based on p-p Stacking of
1,4-Bis(3,6-diphenylpyridazin-4-yl)benzene
Hsien-Chang Kao
Shang-Wei Tang
Jau-Shuenn Wang
Wen-Jwu Wang
Department of Chemistry, Tamkang University,
Tamsui, Taipei, Taiwan (ROC)
A microporous material constructed by p-p interaction of a twisted H-shape poly-
aromatic molecule, 1,4-bis(3,6-diphenylpyridazin-4-yl)benzene (1) was synthesized
and X-ray quality crystals were isolated. The intermolecular distances between the
˚
various aromatic rings are within the range of 3.4 ꢀ 3.7 A, which indicate intermo-
˚
lecular p-p interactions. Hexagonal channels with pores of 13 A width along the
c-axis were observed. Interstitial H2O and MeOH molecules were located within
each porous channel.
Keywords: H-shape molecule; microporous; pyridazine; p-p stacking
INTRODUCTION
Recently, intense research activities have been directed towards
the development of open porous frameworks based on the assembly of
inorganic compounds, activated carbons, metal-organic frameworks,
and organic molecules, into extended motifs held together either by
strong metal–ligand bonding or non-covalent interactions, such as
hydrogen-bonding, and p-p interactions [1–3]. Porous materials have
attracted the attention of chemists due to their nanometer-sized
spaces, which may be used to investigate novel phenomena and for
applications such as molecular storage and heterogeneous catalysis.
These characteristic features are based on their open frameworks,
This work was supported by the National Science Council of Taiwan (ROC) and
Tamkang University.
Address correspondence to Wen-Jwu Wang, Department of Chemistry, Tamkang
University, Tamsui 25137, Taipei, Taiwan (ROC). E-mail: wjw@mail.tku.edu.tw
193

194
H.-C. Kao et al.
which are ascribed to a robust porosity that can accommodate various
guest molecules within their crystal structures [4,5].
Inorganic porous compounds such as zeolites are widely used in
separation, catalysis and exchange. Zeolites frameworks have high
stability and crystallinity but of low porosity [6]. Activated forms of
carbon have high porosity with a broad pore size distribution, so that
many of the channels or cavities are often superfluous and unnecess-
ary for the required porous functions, which leads to poor storage=
separation capacity for a specific guest [7].
Manipulation of functional metal-organic frameworks and organic
porous materials are specially intriguing because they are easier to
control and fine-tune [8,9]. Hydrogen bonding and p-p interactions
have been used in particular for this purpose. Hydrogen bonding is
the most studied intermolecular interaction due to its frequent pres-
ence in organic frameworks. The selectivity and directional nature of
the hydrogen bond has led to its extensive use in the construction
and stabilization of large non-covalently bonded organic porous com-
pounds. Although many of them show unique catalytic properties,
their frameworks are liable to collapse or deform after removal of
guest molecules from the micropores [10]. To date, the number of
organic networks with new structural aspects is increasing, but to
our knowledge of aromatic and heteroaromatic porous structures sus-
tained by p-p interactions are still scarce. This has prompted us to
undertake a program to construct organic solid in which p-p stacking
interactions could be predicted to play an important role in the porous
material.
In this paper we study a twisted H-shape poly-aromatic molecule,
1,4-bis(3,6-diphenylpyridazin-4-yl)benzene (1), in which p-p stacking
of aromatic interactions have been proposed to provide the assembling
force that makes the extended aromatic molecules into an overall
three-dimensional structure.
The intermolecular distance between various aromatic rings are
˚
within the range of 3.4 ꢀ 3.7 A and the dihedral angle between each
aromatic and heteroaromatic rings indicates that the large intermole-
cular p-p interaction is operating in the molecule and a hexagonal
˚
channels with pore width 13 A along the c-axis are observed.
EXPERIMENTAL
3,6-Diphenyl-1,2-dihydro-1,2,4,5-tetrazine [11]
A mixture of 3-benzonitrile (10.4 g, 0.1 mol) and an excess of hydrazine
hydrate (10 ml, 0.32 mol) were warmed in a water bath for 6 h. The

Microporous Material Based on p-p Stacking
195
solid was collected and crystallization from ethanol afforded yellow
needles (m.p. 233–235ꢁC), which was used directly in the subsequent
reaction. The yield was 8.6 g (72%).
3,6-Diphenyltetrazine [11]
3,6-Diphenyl-1,2-dihydro-1,2,4,5-tetrazine (7.0 g) was dissolved in a
mixture of glacial acetic acid (300ml) and water (200 ml) and cooled to
0ꢁC. Sodium nitrite (9.2 g) in cold water (25 ml) was added slowly to this
solution with vigorous stirring. The color of the solution turned to red-
purple. The mixture was neutralized with an ammonia solution and
the product was collected by filtration. Crystallization from ethanol
afforded purplish red plates, m.p. 201–202ꢁC. The yield was 4.2 g (61%).
1H NMR(300 MHZ, CDCl3), (ppm), J (HZ): 8.67(d, 4H, phenyl-H,
J ¼ 1.8), 7.63(t, 4H, phenyl-H, J1 ¼ 1.8, J2 ¼ 1.4), 7.62(d, 2H, phenyl-H,
J ¼ 1.4)
1,4-Bis(3,6-diphenylpyridazin-4-yl)benzene [11]
A mixture of 1,4-diacetylbenzene (2 g, 12.3 mmol) and 3,6-diphenylte-
trazine (5.9 g, 25 mmol) in dry THF was warmed in a water bath for
FIGURE 1 ORTEP diagram of 1,4-bis(3,6-diphenylpyridazin-4-yl)benzene.
Inset diagram is numbering of the aromatic and hetroaromatic rings.

196
H.-C. Kao et al.
3 h followed by addition of 2.5% KOH=MeOH solution into the
mixture. The solid was collected and crystallized by slow diffu-
sion of a THF solution into MeOH. The crystal is colorless needle,
m.p. 271–273ꢁC. The yield was 3.57 g (53%).
RESULTS AND DISCUSSION
The title compound 1,4-bis(3,6-diphenylpyridazin-4-yl)benzene is shown
in Figure 1. Crystal data and structure refinement parameter are listed
in Table 1. A twisted H-shaped conformation is formed by two 3,6-diphe-
nylpyridazine units linked together by benzene at the para-position
(1,4-position). The torsion angle between the two pyridazine units
(ring 2–ring 20) is 70ꢁ, as shown in Figure 2a. The benzene linked at
the 4-position of two pyridazine units makes the ring 1, ring 2 and ring
4 to lie in different planes, creating a twisted H-shape conformation and
a packing structure consisting of a 3-D network. Figure 2b shows the
two phenyl rings (ring 1 and ring 3) attached to pyridazine ring at 3
and 6 position. These two rings (ring 1 and ring 3) make dihedral angles
of 43ꢁ and 6.8ꢁ with the pyridzaine ring (ring 2), respectively. The
TABLE 1 Crystal Data and Structure Refinement Parameter [12]
Empirical formula
Formula weight
C160 H104 N16 O20
2570.59
Temperature
273(2) K
Wavelength
0.71073 A
Crystal system, space group
Unit cell dimensions
Orthorhombic, Pbcn
a ¼ 16.3407(7) A alpha ¼ 90 deg.
b ¼ 10.8145(5) A beta ¼ 90 deg.
c ¼ 18.6069(8) A gamma ¼ 90 deg.
3288.1(3) A^3
Volume
Z, Calculated density
Absorption coefficient
F(000)
1, 1.298 Mg=m^3
0.087 mm^ꢂ1
1336
Crystal size
Theta range for data collection
Limiting indices
Reflections collected=unique
Completeness to theta ¼ 28.36
Refinement method
Data=restraints=parameters
Goodness-of-fit on F^2
Final R indices [I > 2sigma(I)]
R indices (all data)
0.6 ꢃ 0.5 ꢃ 0.3 mm
2.19 to 28.36 deg.
ꢂ18 ꢄ h ꢄ 21, ꢂ14 ꢄ k ꢄ 14, ꢂ 24 ꢄ 1 ꢄ 22
33608=4064 [R(int) ¼ 0.0485]
98.7%
Full-matrix least-squares on F^2
4064=0=223
1.057
R1 ¼ 0.0915, wR2 ¼ 0.2166
R1 ¼ 0.1320, wR2 ¼ 0.2354
0.0035(7)
0.502 and ꢂ0.466 e.A^ ꢂ3
Extinction coefficient
Largest diff. peak and hole

Microporous Material Based on p-p Stacking
197
FIGURE 2 a) Dihedral angle of Ring 2, Ring 4 and Ring 20. B). Dihedral angle
of Ring 1, Ring 2, and Ring 3, solvent molecules hydrogen atoms have been
omitted for clarity.
dihedral angle between ring 1 and ring 2 is greater than between ring 2
and ring 3. This may due to the repulsion between the hydrogen atoms
at 2-position of ring 1 and at 6-position of ring 4 whereas ring 3 is far
away from ring 4 and it experiences less repulsion. Moreover, steric hin-
drance between ring 2 and ring 4 makes the dihedral angle 55.2ꢀ. None
of the aromatic or heteroarometic rings lie in the same plane, which
impedes the formation of p-stacked packing structure.
The twisted H-shape conformation of 1,4-bis(3,6-diphenylpyridazin-
4-yl)benzene is organized into stair-like 1-D chains along a-axis
by pyridazine and phenyl-phenyl intermolecular interactions. The
pyridazine rings reveals an anti stacked orientation to neighbor
˚
molecule along b-axis with a distance 3.8 A, while the other two phenyl

198
H.-C. Kao et al.
FIGURE 3 2-D representation of the crystal cell viewing down the a-axis,
b-axis and c-axis exhibit the molecular packing solvent molecules have been
omitted for clarity. (See COLOR PLATE XVIII)
rings separated by a face to face orientation with other unit and the
˚
distance between the rings is 4.9 A. Furthermore, the 3,6-diphenyl-
pyridazine forms a pseudo-zigzag chain along the b-axis. Overall, each
H-shape unit is connected with four other units through eight iden-
tical offset p-p interactions, forming an unusually compact, ordered,
and stable molecular solid. Figure 3 shows a 2D representation of
the crystal cell.
The 1-D chains along a-axis are propagating in the b directions. The
strand running along the b-axis exhibits separation of benzene in
every unit and the distance between the centroids of interplanar
˚
benzene is 12.3 A. This layer-like arrangement creates void spaces
that are made hydrophilic by the surrounding pyridazines. The overall
result is p-stacked strands with hydrophilic channels along the c-axis,
wherein the intra-channel water and solvent are located. Figure 4 is
the space-filling diagram along c-axis.

Microporous Material Based on p-p Stacking
199
FIGURE 4 Space-filling diagram along c-axis, solvent molecules have been
omitted for clarity.
CONCLUSION
This study has shown an organic microporous material formed by
intermolecular p-stacking interactions between 1,4-bis (3,6-diphenyl-
pyridazin-4-yl) benzene. Such new porous material may prove highly
interesting in host-guest applications since the intra-channel interac-
tions are much different and distinct from the forces holding the
channel framework together.
REFERENCES
[1] Batten, S. R. & Robson R. (1998). Angew. Chem. Int. Ed., 37, 1460.
[2] Blake, A. J., Champness, N. R., Hubberstey, P., Li, W. S., Withersby, M. A., &
Schrtder, M. (1999). Coord. Chem. Rev., 183, 117.
[3] Kitagawa, S. & Kawata, S. (2002). Coord. Chem. Rev., 224, 11.
[4] Yaghi, O. M., O’Keeffe, M., Ockwig, N. W., Chae, H. K., Eddaoudi, M., & Kim, J.
(2003). Nature, 423, 705.
[5] Moulton, B. & Zaworotko, M. J. (2001). Chem. Rev., 101, 1629.
[6] Li, H., Laine, A., O’Keeffe, M., & Yaghi, O. M. (1999). Science, 283, 1145.
[7] Zhou, Y., Zhu, H., Chen, Z., Chen, M., Xu, Y., Zhang, H., & Zhao, D. (2001). Angew.
Chem. Int. Ed., 40, 2166.
[8] Seki, K. (2001). Chem. Commun., 1496.
[9] Chui, S. Y., Lo, S. M. F., Charmant, J. P. H., Orpen, A. G., & Williams, I. D. (1999).
Science, 283, 1148.
[10] Lai, S. F., Cheng, C.Y., & Lin, K. J. (2001). Chem. Commun., 1082.

200
H.-C. Kao et al.
[11] Geldard, J. F. & Francis, L. (1965). J. Org. Chem., 30, 318.
[12] CCDC 284419 contains the supplementary crystallographic data for this paper.
These data can be obtained free of charge at www.ccdc.cam.ac.uk=conts=
retrieving.html [or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) 44 1223=336–033; E-mail: depos-
it@ccdc.cam.ac.uk].