Crystal engineering of 3D porous coordination polymers through hydrogen bonding to coordination from 1D helical chains

Article abstract of DOI:10.1246/cl.2003.588

The combination of salicylic acid and 4-aminopyridine leads to a 3D hydrogen bonding network while the replacement of 4-aminopyridine with 4,4′-bipyridine yields the same topological net with big channels via coordination.

Full text of DOI:10.1246/cl.2003.588

588
Chemistry Letters Vol.32, No.7 (2003)
Crystal Engineering of 3D Porous Coordination Polymers through Hydrogen Bonding to
Coordination from 1D Helical Chains
Long-Guan Zhu,ꢀ Susumu Kitagawa,y and Kenji Sekiyy
Department of Chemistry, Zhejiang University, Hangzhou 310027, P. R. China
yDepartment of Synthetic Chemistry and Biological Chemistry, Engineering Faculty, Kyoto University, Sakyo-ku, Kyoto 606-8501
yyResearch and Development Department, Osaka Gas Company, Limited, Kohohana-ku 6-19-9, Osaka 554-0051
(Received April 3, 2003; CL-030287)
The combination of salicylic acid and 4-aminopyridine
leads to a 3D hydrogen bonding network while the replacement
of 4-aminopyridine with 4,40-bipyridine yields the same topolo-
gical net with big channels via coordination.
nation of 4-aminopyridine and water consists of a hydrogen-
bond spacer ligand, namely APW, leading to a 3D network with
little porosity and the separation of CuÁ Á ÁCu by APW linker is
ꢀ
9.902(3) A.
The small porosity in compound 1 is caused by short linker
of APW. If we keep the robust of framework supported by sal
The construction of porous framework through crystal en-
gineering1 is currently attracting a considerable interest because
of their potential applications in catalysts,2 gas sorbents,3 ion-
exchange,4 and so on. Strategies for assemblies of these novel
materials includes hydrogen-bonded architecture, pillared clay
mimics, zeolite analogues, and coordination polymer
chemistry.5 A key challenge in the porous coordination poly-
mers is to design and synthesize predictable topological struc-
tures or control the dimensionality of coordination polymers.6
Salicylic acid, H2sal, has received a great deal of interest as
a bifunctional ligand capable of forming coordination polymers
in this laboratory.7 The structures associated with this ligand are
controlled by the extent of deprotonation of the H2sal, such as
salÀ and sal2À, and the nature of the second ligand coordinated
to the metal center.8 The bidentate property of 4-aminopyridine
ligand (4AP) reported by Rosseinsky5 raised our interest to con-
struct high dimensional coordination polymers. Thus the combi-
nation of salicylic acid and 4-aminopyridine leads to a helical
chain and extended 3D network via hydrogen bonding.
Figure 1. (a) An ORTEP view of 1 with 50% ellipsoids
and labelling scheme. Importanꢀt bond distances
ꢀ
(A):Cu(1)-O(1) 1.942(4), Cu(1)-O(2 ) 1.991(3), Cu(1)-
Slow diffusion of 4AP into a water/methanol solution of
copper acetate and H2sal yields pure compound 1,
[Cu(sal)(4AP)(H2O)]n.9 The molecular structure of 1, estab-
lished by single-crystal X-ray diffraction analysis,11 is shown
O(3) 1.917(3), Cu(1)-O(4) 2.364(4), Cu(1)-N(1) 2.018(3).
(b) View of 1D helical chain of 1.
in Figure 1(a). Each sal is fully deprotonated, namely sal2À
.
The sal ligand acts as a bridging ligand to two CuII via the oxy-
gen atoms. The copper center in 1 is a square pyramidal with
three oxygen atoms of the sal and a pyridine-N atom of 4-ami-
nopyridine occupying the basal positions and the oxygen atom
of water occupying the apical position. As a consequence of the
sal bridge, compound 1 has an extended 1D helical structure as
shown in Figure 1(b). Each motif of [CuII(sal)]n in the 1D chain
is linked through hydrogen bond to three neighbouring chains
having opposite helicity with
ꢀ
a
4.692(3) A. The atoms of water molecules with pyridine-N
CuÁ Á ÁCu separation of
atoms of 4AP from the neighboring 1D chains form hydrogen
ꢀ
bonds [OÁ Á ÁN, 2.951(7) A]. Moreover one-dimensional helical
network has three orientational hydrogen-bonded sites, direct-
ing a 3D network with small channels (Figure 2). The bifunc-
tional 4-aminopyridine ligand therefore allows the construction
of molecular frameworks in which the infinite one-dimensional
helical building blocks characteristic of sal are linked to form a
hydrogen-bonded three-dimensional pore network. The combi-
Figure 2. View of 3D hydrogen bonding network of 1
along c axis.
Copyright Ó 2003 The Chemical Society of Japan

Chemistry Letters Vol.32, No.7 (2003)
589
while replace the combination of hydrogen-bond ligand (APW)
into a rigid and long spacer ligand, the same topological 3D net
and bigger channel will be expected. This idea was achieved by
the combination of H2sal and 4,40-bipyridine (4,40-bipy) leading
to the formation of compound 2, [Cu(sal)(4,40-bipy)]n.10 The
compound 2 was obtained from the reaction of Cu(CH3COO)2,
salicylic acid and 4,40-bipy in mixed solvents of DMF and
methanol.
done while we found it is difficult to locate all solvents, so we
dried crystals at vacuum condition 10 h at room temperature be-
fore data collection. Compound 2 is stable when heated up to
270 ꢁC and fully desolvated after vacuum degassing 10 h as evi-
denced by X-ray single-crystal analysis, and nice data collection
was obtained, which is few examples of 3D coordination poly-
mers when solvents are removed and still shows structural sta-
bility.
In compound 2 the copper center has a square pyramidal
geometry, and with shorter bond lengths comparing with that
of in 1 (Figure 3). And in 1D motif, [CuII(sal)], of compound
2 is the same as that of compound 1 and the separation distance
between two neighboring CuII ions in the 1D chain of 2 is
We succeeded in synthesizing two compounds based on
building blocks, CuII, H2sal and N-donor ligands, using
layered-solution approach and two 3D coordination polymers
assembled by hydrogen bonding and coordination. Our syn-
thetic successful examples are of benefit to design process of
crystal engineering of porous coordination polymers.
ꢀ
4.58(1) A, much shorter than that of in 1. Obviously compound
2 has a compact structure comparing with that of compound 1.
3D coordination polymer of compound 2 is constructed by
1D helical chains of [CuII(sal)]n with threefold symmetry and
linkers 0of 4,40-bipyridine. Six 1D helical chains hold together
One of the authors (L. G. Zhu) thanks the NNSF of China
(No. 50073019) for financial support.
ꢀ
References and Notes
by 4,4 -bipyridine linkers into a channel with 8:6 Â 8:6 A
1
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2568 (2002). d) C. J. Kepert, T. J. Prior, and M. J. Rosseinsky, J.
Solid State Chem., 152, 261 (2000).
(Figure 4). The ring of each channel is made up of six sal units
joining six CuII cations. For this compound data collections at
room temperature, low temperature or capillary conditions were
2a) M. Fujita, Y. J. Kwon, S. Washizu, and K. Ogura, J. Am. Chem.
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3
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4
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6
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7
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Prepartion of compound 1. Crystals were obtained using a three-
layer solution in a slender tube. The upper layer (ca. 5 cm) was a
methanol solution that contained Cu(CH3COO)2ÁH2O (0.05 mol/
L) and H2sal (0.2mol/L). The middle layer (ca. 2cm) was mixed
solvents of methanol and water with volume ration of 1:1. The low-
er layer (ca. 5 cm) was an aqueous solution of 4AP (0.2mol/L).
Product crystals were obtained on standing several days at ambient
conditions. Elemental analysis for [Cu(sal)(4AP)(H2O)], Calcd.
(%): C: 41.95, H: 3.13, N: 5.43; Found: C: 42.35, H: 2.93, N:
5.61. Yield is 76% based on copper salt.
Figure 3. An ORTEP view of 2 with 50% ellipsoids
ꢀ
and labelling scheme. Important bond distances (A):
Cu(1)-O(1) 1.977(3), Cu(1)-O(2) 1.933(3), Cu(1)-O(3)
1.901(5), Cu(1)-N(1) 2.055(6), Cu(1)-N(2) 2.301(6).
8
9
10 Preparation of compound 2: The compound was synthesized by si-
milar method in 1. Products were desolvated under vacuum condi-
tion 10 hours. Calcd. for [Cu(sal)(4,40-bipy)]: C: 57.38, H: 3.40, N:
7.87%. Found: C: 57.43, H: 3.35, N: 7.91%. Yield is 84% based on
copper salt.
11 Crystal data for 1: trigonal, R-3(h) (No. 148), a ¼ 24:247ð1Þ,
ꢀ
ꢀ 3
c ¼ 11:3891ð6Þ A,
V ¼ 5798:6ð5Þ A ,
Dc ¼ 1:607 gÁcmÀ3
,
Z ¼ 18, R ¼ 0:036 and Rw ¼ 0:044. Crystal data for 2: trigonal,
ꢀ
R-3 (No. 148), a ¼ 32:602ð2Þ, c ¼ 10:6162ð4Þ A, V ¼
9772:0ð9Þ A , Z ¼ 18, Dc ¼ 1:088 gÁcmÀ3
,
R ¼ 0:0534 and
ꢀ 3
Figure 4. View of 3D network with big channel of 2
along c axis.
Rw ¼ 0:0683. CCDC-194731 and CCDC-194732for compounds
1 and 2, respectively.
Published on the web (Advance View) June 10, 2003; DOI 10.1246/cl.2003.588