Topological diversification in metal-organic frameworks: Secondary ligand and metal effects

Article abstract of DOI:10.1002/ejic.200800898

A series of interesting coordination polymers have been prepared by the combination of a V-shaped 4,4′-oxybis(benzoic acid) (H₂oba) and neutral organonitrogen ligands with different metal ions, namely, {[M(oba)(bpe)]·H₂O}_n

Full text of DOI:10.1002/ejic.200800898

FULL PAPER
DOI: 10.1002/ejic.200800898
Topological Diversification in Metal-Organic Frameworks: Secondary Ligand
and Metal Effects
Jian-Qiang Liu,[a] Yao-Yu Wang,*[a] Ya-Nan Zhang,[a] Ping Liu,[a] Qi-Zhen Shi,[a] and
Stuart R. Batten*[b]
Keywords: Coordination polymers / Coordination modes / Ligand effects / Crystal engineering
A series of interesting coordination polymers have been pre-
pared by the combination of a V-shaped 4,4Ј-oxybis(benzoic
acid) (H2oba) and neutral organonitrogen ligands with dif-
ferent metal ions, namely, {[M(oba)(bpe)]·H2O}n [M = Mn (1),
Co (2)], [M(oba)(N3)]n [N3 = dipyridin-2-ylamine; M = Cd
(3), Cu (4)] and {[Zn(oba)(N5)]·2H2O}n (5) [bpe = 1,2-bis(4-
pyridyl)ethene, N5 = bis(pyridin-2-yl)pyridine-2,6-diamine].
The framework structures of these neutral polymeric com-
plexes have been determined by single-crystal X-ray diffrac-
tion studies. Compound 1 has a threefold pcu-type network
structure. Although 2 has the same ligands and coordination
modes as 1, it consists of corrugated 2D layers formed of a
series of squares, which allows the sheets to interpenetrate
in an unusual 2DǞ3D parallel fashion. Polymers 3 and 4 ex-
hibit double-helical chains formed by π–π stacking interac-
tions from the phenyl rings of the N3 ligands. Compound 5
forms a 2D supramolecular architecture directed by hydro-
gen bonding between the NH groups of the N5 ligand, the
uncoordinated carboxylate oxygens, and the intercalated
water molecules. This work markedly indicates that the ef-
fect of auxiliary ligands is significant in the construction of
these network structures, which are also well regulated by
the metal centers. Thermogravimetric analysis (TGA) and
XRPD results for compound 1 as well as luminescent proper-
ties for compounds 3 and 5 are discussed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2009)
coordination polymers. For instance, {[Cu(oba)(H2O)]2·
0.5H2O} exhibited a unique fivefold 4-connected 4284
(lvt)[9a,9b] interpenetrating structure with nine interwoven
helices.[9c,9d]
Introduction
The crystal engineering of metal-organic frameworks
(MOFs) is of great current interest not only because of their
significant potential functions in gas storage, chemical sepa-
rations, microelectronics, nonlinear optics, and hetero-
geneous catalysis, but also because of their intriguing archi-
tectures and intricate entangled motifs.[1–3] The mutual en-
tanglement of structural motifs is a commonly encountered
feature in coordination polymer chemistry.[1a–1d,2a,3–5] How-
ever, the formation of extended coordination framework so-
lids with desired structural features and/or physicochemical
properties greatly depends on the sophisticated selection
and utilization of multitopic building blocks as well as tec-
tonic interactions.[1a,6] Conformationally nonrigid ligands
are usually building elements for the assembly of interesting
entangled networks, thanks to their varied geometries.[7,8]
4,4Ј-Oxybis(benzoic acid) (H2oba) is a typical example of a
long, V-shaped, flexible ligand which has been used to pro-
mote the formation of polycatenated and self-penetrating
On the other hand, in the two-ligand MOF assembly sys-
tems, both organic and inorganic secondary ligands can
manipulate the structural topologies through coordination
in either terminal or bridging fashions.[10] For example, Cao
and his coworkers used the secondary ligands as terminal
and bridging ligands to tune the formation of helical struc-
tures.[11] As for the dipyridyl ligands, some analogous link-
ers derived from the proper modification of the classic 4,4Ј-
bipyridine molecule have been employed,[10] which present
unrivaled backbone flexibility and thus impose profound
steric effects on the direction of the unexpected coordina-
tion frameworks. Recently, we have reported a 4-crossing
[2]-catenane motif based on oba and 1,3-bis(4-pyridyl)pro-
pane (bpp).[12] However, the systematic investigation of the
role of auxiliary ligands in the construction of coordination
nets is not well documented to date. Therefore, the develop-
ment of a comprehensive research program is required, and
[a] Key Laboratory of Synthetic and Natural Functional Molecule
Chemistry of Ministry of Education, Department of Chemistry, the rational design of new frameworks would be a long-
Shaanxi Key Laboratory of Physico-Inorganic Chemistry,
range challenge.
Northwest University,
Xi’an 710069, P. R. China
[b] School of Chemistry, Monash University,
Victoria 3800, Australia
With this background in mind, we continued our investi-
gation and chose H2oba as a bridging ligand to react with
d-block metal ions. The neutral bpe, N3, and N5 ligands
were introduced into the MII/oba system, and a series of
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
Eur. J. Inorg. Chem. 2009, 147–154
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
147

J.-Q. Liu, Y.-Y. Wang, Y.-N. Zhang, P. Liu, Q.-Z. Shi, S. R. Batten
FULL PAPER
polymers with unusual topologies were obtained, namely, Table 1. Selected bond lengths [Å] and angles [°].
{[M(oba)(bpe)]·H2O}n [M = Mn (1), Co (2)], [M(oba)-
(N3)]n [M = Cd (3), Cu (4)] and {[Zn(oba)(N5)]·2H2O}n
(5). To the best of our knowledge, compound 2 represents
the first example in the M/oba system that possesses an
Complex 1
Mn(1)–O(1)
Mn(1)–N(1)
Mn(1)–O(4)#2
2.304(4)
2.254(4)
2.097(4)
57.76(14)
Mn(1)–O(2)
2.262(4)
2.281(4)
2.099(4)
101.16(14)
Mn(1)–N(2)#1
Mn(1)–O(5)#3
O(1)–Mn(1)–N(2)
O(1)–Mn(1)–O(4)#2 151.86(14)
O(2)–Mn(1)–O(4)#2 97.20(14)
N(1)–Mn(1)–N(2)#1 174.50(15)
interpenetrating 2DǞ3D structural feature. The crystal O(1)–Mn(1)–O(2)
O(1)–Mn(1)–N(2)#1 81.11(14)
O(2)–Mn(1)–N(2)#1 90.39(14)
O(2)–Mn(1)–O(5)#3 146.64(14)
Symmetry codes: #1: 1 + x, y, 1 + z; #2: 2 – x, –1/2 + y, 1/2 – z; #3: 1 +
x, 1/2 – y, –1/2 + z
structures and topological analysis of these compounds,
along with a systematic investigation of the effect of the
coordination modes of the oba anions, metal ions, and neu-
tral ligands on their ultimate frameworks, will be discussed.
Complex 2
Co(1)–O(1)
Co(1)–N(1)
Co(1)–O(3)#1
O(1)–Co(1)–O(3)#1
O(2)–Co(1)–N(1)
O(2)–Co(1)–O(4)#1
O(3)#1–Co(1)–N(2)
2.011(3)
2.052(4)
2.166(3)
97.34(10)
156.00(12)
105.66(9)
150.68(12)
Co(1)–O(2)
Co(1)–N(2)
Co(1)–O(4)#1
O(1)–Co(1)–O(4)#1 157.87(11)
O(2)–Co(1)–O(3)#1 87.02(9)
2.277(3)
2.054(3)
2.083(3)
Results and Discussion
{[Mn(oba)(bpe)]·H2O}n (1)
The structure of 1 contains one unique Mn atom, one
oba ligand, one bpe ligand, and intercalated water mole-
N(1)–Co(1)–N(2)
O(4)#1–Co(1)–N(2) 89.92(13)
96.89(13)
cules (all of which are related by symmetry). The Symmetry codes: #1: x, –1 + y,1 + z.
{MnO4N2} coordination spheres are each defined by two
oxygen atoms from one chelating oba carboxylate, two oxy-
gen atoms from two different bidentate-bridging carboxyl-
ate groups, and two cis-oriented bpe nitrogen donors. Bond
lengths and angles about the metal centers in 1 are consis-
tent with a distorted octahedral geometry caused by the
presence of chelating/bidentate-bridging ligands and are
given in Table 1. The Mn–O bond lengths span a range of
Complex 3
Cd(1)–O(1)
Cd(1)–N(1)
Cd(1)–O(4)#1
O(1)–Cd(1)–N(3)
O(1)–Cd(1)–O(5)#1
O(2)–Cd(1)–N(3)
O(2)–Cd(1)–O(5)#1
O(4)#1–Cd(1)–N(1)
2.380(13)
2.302(13)
2.404(11)
162.9(4)
96.9(4)
107.6(5)
105.0(4)
94.9(4)
Cd(1)–O(2)
Cd(1)–N(3)
Cd(1)–O(5)#1
O(1)–Cd(1)–O(4)#1 104.7(4)
O(2)–Cd(1)–N(1) 103.7(4)
O(2)–Cd(1)–O(4)#1 153.7(4)
N(1)–Cd(1)–N(3) 84.4(4)
O(5)#1–Cd(1)–N(1) 150.7(4)
2.348(12)
2.288(13)
2.342(11)
2.091(4) to 2.300(4) Å. The Mn atoms are bridged into Symmetry codes: #1: 1 + x,1/2 – y, 1/2 + z.
pairs by carboxylate groups, and the Mn–Mn distance is
4.276 Å (Figure 1). These Mn dimers are then connected to
other dimers by the oba ligand bridges. Each oba bridge
bonds to two Mn atoms through one carboxylate group to
form a dimer, and then to a third Mn atom, which is part
of another dimer, through the other chelating carboxylate
group. The bridging mode of the oba ligand is very similar
to that in the [Co(oba)(bpa)]n [bpa = 1,2-bis(4-pyridyl)eth-
Complex 4
Cu(1)–O(1)
Cu(1)–N(1)
Cu(1)–O(3)#1
O(1)–Cu(1)–O(2)
O(1)–Cu(1)–N(3)
O(1)–Cu(1)–O(4)#1
O(2)–Cu(1)–N(3)
O(3)#1–Cu(1)–N(3)
2.414(2) Cu(1)–O(2)
1.970(2) Cu(1)–N(3)
2.4524(19) Cu(1)–O(4)#1
57.96(8) O(1)–Cu(1)–N(1)
104.09(8) O(1)–Cu(1)–O(3)#1 155.62(7)
102.35(7) O(2)–Cu(1)–N(1) 158.51(9)
1.984(2)
1.988(2)
2.0137(18)
100.71(8)
95.04(9) O(2)–Cu(1)–O(3)#1 104.82(7)
93.96(8) O(4)#1–Cu(1)–N(3) 152.01(9)
ane] complex,[13] which may be responsible for their analo- Symmetry codes: #1: 1 + x,1/2 – y,1/2 + z.
Complex 5
Zn(1)–O(1)
Zn(1)–N(3)
Zn(1)–O(4)#1
O(1)–Zn(1)–N(1)
N(1)–Zn(1)–N(3)
O(4)#1–Zn(1)–N(3)
2.093(3) Zn(1)–N(1)
2.107(4) Zn(1)–N(5)
2.063(3)
89.15(15) O(1)–Zn(1)–N(3)
91.73(16) N(1)–Zn(1)–N(5)
125.47(16) O(4)#1–Zn(1)–N(5) 84.22(16)
2.065(4)
2.088(4)
134.46(15)
176.37(16)
Symmetry codes: #1: –1 + x, y, z.
Figure 1. The coordination environment of the MnII atom in 1.
148
Figure 2. A view of a layer of squares in the structure of 1.
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 147–154

Ligand and Metal Effects on Assembly of Metal-Organic Frameworks
gous structures. The dimers are thus bonded to four oba of a pcu-related net. Figure 4 shows a single box-like cavity
ligands, two of which bridge the Mn atoms to form the of the net; the openness of the single net leads to three
dimer, and two others which each chelate to a different Mn interpenetrating networks.
atom in the dimer. The dimers thus act as a 4-connecting
node to generate a layer formed of a series of squares (Fig-
{[Co(oba)(bpe)]·H2O}n (2)
ure 2). These sheets are then bridged by the bpe ligands to
generate a 3D network. Each Mn dimer is bridged to a
dimer in the sheet above and below by pairs of bpe ligands
(Figure 3). If each pair is treated as a single link, the dimers
become 6-connecting nodes, and the overall topology is that
¯
The asymmetric units of 2 crystallize in the triclinic P1
space group (Table 2). Both contain one divalent metal
atom, one oba ligand, one bpe ligand, and one lattice water
molecule. The structure consists of a corrugated 2D layer
formed of a series of squares in which the metal ions are
bridged in one direction by the oba ligand and in the other
by the bpe ligand. The open, corrugated nature of the sheets
allows them to interpenetrate in an unusual 2DǞ3D paral-
lel fashion,[14] as shown in Figure 5. Each sheet is pene-
trated by two others (one above and one below), which have
parallel but not coincident mean planes. This leads to an
overall 3D entanglement, which is a very uncommon motif.
This structure is isomorphous with the {[Cu(oba)(bpe)]·
H2O}n compound, which was investigated in detail in our
previous communication.[14]
Figure 3. A single box-like cavity in 1 formed by the bridging of
the layers in Figure 2 by the oba ligands.
Figure 5.The unusual 2DǞ3D parallel interpenetration of the
sheets in 2.
[M(oba)(N3)]n [M = Cd (3), Cu (4)]
It has been noted that aromatic chelate ligands (such as
2,2Ј-bipyridine and 1,10-phenanthroline) often lead to 1D
polymers and may provide potential supramolecular re-
cognition sites for π–π aromatic stacking interactions to
Figure 4. The three interpenetrating pcu networks in 1. Nodes rep-
resent the centers of the Mn dimer nodes, and the links represent
either oba ligand bridges or pairs of oba ligand bridges.
Table 2. Crystal data and structure refinement information for compounds 1–5.
Compounds
1
2
3
4
5
Formula
FW
Temp. / K
Crystal system
Space group
a / Å
b / Å
c / Å
α / °
β / °
C26H20MnN2O6
511.38
298(2)
monoclinic
P21/c
10.697(3)
18.619(5)
12.600(3)
90
107.418(5)
90
C26H20CoN2O6
515.37
298(2)
C24H17CdN3O5
539.82
298(2)
monoclinic
P21/c
12.732(10)
15.832(13)
11.304(9)
90
94.529(10)
90
C24H17CuN3O5
490.96
298(2)
monoclinic
P21/c
12.327(2)
15.540(3)
11.252(2)
90
96.093(3)
90
C29H25ZnN5O7
620.93
298(2)
monoclinic
P21/c
14.8933(11)
8.1547(6)
23.1093(17)
90
90.1890(10)
90
2806.6(4)
4
triclinic
¯
P1
9.314(5)
11.334(7)
12.472(7)
69.658(9)
80.316(9)
87.866(9)
1216.6(12)
2
γ / °
V / Å3
Z
2394.4(11)
4
2272(3)
4
2143.3(7)
4
F (000)
Dc / gcm–3
GOF
1052
1.419
0.784
0.0562
0.1831
530
1.407
0.638
0.0379
1080
1.578
1.033
0.1205
0.3499
1004
1.521
0.513
0.0294
0.0382
1280
1.469
1.085
0.0574
[a]
R1 [IϾ2σ(I)]
[a]
WR2 (all data)
0.0616
0.1910
[a] R1 = ∑||Fo| – |Fc||/∑|Fo|, wR2 = {∑[w(Fo – Fc ) ]/∑(Fo2)2}1/2
.
2
2 2
Eur. J. Inorg. Chem. 2009, 147–154
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
149

J.-Q. Liu, Y.-Y. Wang, Y.-N. Zhang, P. Liu, Q.-Z. Shi, S. R. Batten
FULL PAPER
Figure 6. The coordination environment of the Cd center in 3.
form multistranded helices.[7g] Therefore, the heterocyclic π stacking interactions (Figure 7).[7g] To the best of our
aromatic chelate ligands, N3 (dipyridin-2-ylamine) and N5 knowledge, such zipper-like double-stranded helical chains
[bis(pyridin-2-yl)pyridine-2,6-diamine], were introduced have been documented for only one previous example.[15]
with the aim of synthesizing noninterpenetrating 1D nets. The double-stranded helical chains are stabilized by hydro-
In contrast to other aromatic chelate ligands (2,2Ј-bipyr- gen bonds between the carboxylate oxygen atom (O4) and
idine), the tailored diimine contains an active amine (–NH) the nitrogen atom of the –NH group of the N3 ligand.
hydrogen, and the aromatic rings in N3 and N5 may induce
intermolecular hydrogen bonding and π–π stacking interac-
tions to lead to stable supramolecular networks.
{[Zn(oba)(N5)]·2H2O}n (5)
Compounds 3 and 4 are isostructural, and thus only 3 is
described here in detail. In the crystal structure of 3, there
is one CdII atom, one bis(bidentate) oba ligand, and one N3
ligand in each independent crystallographic unit (Figure 6).
Each CdII atom in 3 is primarily coordinated by four oxy-
gen atoms from two bis(bidentate) oba ligands and two ni-
trogen atoms from a chelating N3 to establish a distorted
octahedral geometry. The average Cd–O bond length is
2.36 Å, and the largest O–Cd–O angle is 153.7(4)°, which
indicates a distorted octahedral coordination sphere. Each
pair of adjacent CdII atoms is bridged together by an oba
ligand to form a chiral chain running along a crystallo-
graphic 21 axis in the b direction with a long pitch of
15.1 Å. These chains are decorated with N3 ligands alter-
nating on two sides and are further extended into 2D net-
works through interdigitation of the lateral N3 ligands from
adjacent chains in a zipper-like, offset fashion with a face-
to-face distance of ca. 3.72 Å, which indicates aromatic π–
When N5, a chelating aromatic ligand of a larger size,
was used instead of N3 under similar reaction condition,
an analogous neutral single-stranded chain is formed (5).
As illustrated in Figure 8, the oba ligand adopts a bis(mon-
odentate) mode and links neighboring Zn1 atoms to form
a single-stranded chain. Zn1 is coordinated by two oxygen
atoms from two different oba ligands [Zn1–O4 2.062(3),
Zn1–O1 2.095(3) Å] and three nitrogen atoms from a tri-
dentate N5 ligand [Zn–N1 2.063(4), Zn1–N5 2.087(4), Zn1–
N3 2.106(4) Å]. The two oxygen atoms of the carboxylate
are located in two apical positions and establish a trigonal
bipyramidal N3O2 geometry for the Zn atom. Unlike those
in 3, the N5 ligands are attached to only one side of the
single-stranded helical chain, and are oriented perpendicu-
larly to the chain. The approximately perpendicular orien-
tation of the N5 ligands allows for pairing of two centro-
symmetrically related single-stranded helical chains directed
by hydrogen bonds between an uncoordinated oxygen atom
of a carboxylate group and the nitrogen atom of one of
the –NH groups. These pairs are then further intercon-
nected into 2D layers by hydrogen bonding between the
other –NH groups, the intercalated water molecules, and
the other uncoordinated carboxylate groups. Notably, the
lateral N5 ligands from adjacent chains are not paired to
Figure 7. View of a zipper-like double-chain in the structure of 3.
Figure 8. The coordination environment of the ZnII ion in compound 5. All hydrogen atoms have been omitted for clarity.
150 Eur. J. Inorg. Chem. 2009, 147–154
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Ligand and Metal Effects on Assembly of Metal-Organic Frameworks
afford π–π stacking interactions, which may be attributed to (oba)(bpa)]n complex.[13] The presence of flexible bpa li-
the improper orientation between N5 molecules. The lattice gands may play an important role in the generation of fur-
water molecules intercalate into the spaces between the ther interpenetration in the [Co(oba)(bpa)]n complex.
chains and form small water clusters, as shown in Figure 9. Furthermore, the coordination modes of the oba ligands
The lattice water molecules further bind to the uncoordi- in the [Co(oba)(bpa)]n and [Co(oba)(bpe)]n complexes are
nated oxygen atom (O5) to generate a chair-like formation. different. To further examine the influence of the secondary
ligand on the self-assembly of supramolecular entities, two
aromatic chelate ligands were used instead of bpp and bpe.
Consequently, 3 and 4, featuring helical chain structures,
were obtained. The neighboring chains make zipper-like
double-stranded chains through supramolecular recogni-
tion. In contrast, the presence of the larger aromatic N5
Figure 9. View of a pair of hydrogen-bonded chains in 5.
ligands weakens the π–π stacking interactions in 5 and re-
sults in the formation of 2D grid-like nets in the presence
of hydrogen bonds. Thus the ancillary ligand has a signifi-
cant effect on the formation and structure of the coordina-
tion polymers. In order to construct polymers of peculiar
topologies, an effective method can be to introduce ancil-
lary ligands.
Comparison of the Structures of Coordination Polymers
The simultaneous use of the flexible, rigid, and aromatic
chelating ligands and the aromatic V-shaped dicarboxylate
ligands affords diverse entangled networks, as shown in
Scheme 1. Although we are unable to propose definitive
reasons as to why the compounds exhibit different topolo-
gies with our present state of knowledge, some of the gene-
ral trends observed are discussed below.
Effect of the Metal Nature
It is interesting that, although 1 and 2 bind to the same
ligands and have similar molecular compositions, the CoII
(2) and MnII (1) complexes give completely different prod-
ucts. From the structural descriptions above, the MnII com-
pound 1 contains three interpenetrating 3D pcu-type nets,
Effect of the Secondary Ligand
The connectivities of the polymers are strongly related to while the CuII/CoII complexes 2 have 2D undulated layers
the secondary ligand. The following discussion provides a formed of a series of squares. Furthermore, the CoII and
qualitative explanation for this conclusion. Although the MnII ions are all hexacoordinate and have distorted octahe-
bpp and bpe ligands are both neutral N-containing linkers, dral geometries, but their coordination environments are
they are quite different. For example, the bpp ligand can different. In compound 2 there are two chelating oba and
assume different conformations (TT, TG, GG, and GGЈ) two bpe ligands around the metal ions, whereas in complex
that display quite different N–to–N distances,[16] and it is 1, which contains dimeric Mn units, there is one terminal
more flexible than bpe. When the bpp ligand was intro- chelating and two terminal bridging oba ligands and two
duced into the CuII/CoII/NiII/H2oba system, we obtained bpe ligands around each metal ion. More ligands surround
three 2D isostructural polymers displaying 4-crossing [2]- each MnII ion than the CuII/CoII ions. Moreover, the oba
catenane motifs (Figure S1).[12] Another two isostructural ligand adopts chelating-bidentate and bridging-bidentate
polymers (2 and {[Cu(oba)(bpe)]·H2O}n[14]) with 2D layers coordination modes in 1, which promotes interpenetration
made up of a series of squares were prepared by the combi- and higher dimensionality. Similar results are found for the
nation of bpe, oba, and CuII/CoII. In these structures, how- other complexes with oba ligands in the presence of flexible
ever, each sheet is penetrated by two others (one above and ligands.[13] A rational assembly of metal ions is critical for
one below), which have parallel but not coincident mean the formation of novel and higher dimensional networks.
planes, to lead to an unusual 3D entanglement. Jin and his
As discussed above, a variety of framework structures
coworkers obtained a 3D threefold architecture for the [Co- can be achieved on the basis of the choice of the different
Scheme 1. Reactions of the oba ligand.
Eur. J. Inorg. Chem. 2009, 147–154
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
151

J.-Q. Liu, Y.-Y. Wang, Y.-N. Zhang, P. Liu, Q.-Z. Shi, S. R. Batten
FULL PAPER
secondary ligands. Their network arrays vary from 2D open Kitagawa’s third generation of MOFs, showing a dynamic
layers (4-crossing [2]-catenane motifs[12] and unusual nature.[17]
2DǞ3D parallel interpenetration) and 3D porous struc-
tures (3D threefold interpenetration) to zipper-like double-
Photoluminescent Properties
stranded helical chains. On the other hand, the choice of
metal center may also tune the resultant extended networks
of the MOFs. However, all the variable factors cannot be
accurately forecasted at this stage.
The emission spectra of complexes 3 and 5 in the solid
state at room temperature were investigated. It was ob-
served that an emission occurs at 386 nm (Figure S3, λex
=
260 nm) for 3, which is larger than that of the free N3 li-
gand and is probably due to the H bonding, π–π stacking,
and the enhanced rigidity of 3.[18] It was also observed that
Thermogravimetric Analyses
an intense emission occurred at 400 nm (Figure S3, λex
=
To study the stability of the polymers, thermogravimetric
analysis (TGA) of complex 1 was performed. The TGA dia-
gram of 1 indicates two weight loss steps. The first weight
loss began at 20 °C and was complete at 125 °C. The ob-
served weight loss of 4.3% corresponds to the loss of the
lattice water molecule (calcd. 3.6%). The second weight loss
occurs in the 330–541 °C range, which can be attributed to
the elimination of bpe and oba ligands (Figure S2). Ad-
ditionally, to confirm the phase purity and stability of com-
pound 1, the original sample and the dehydrated sample
were both characterized by X-ray powder diffraction
(XRPD) at room temperature. The pattern that was simu-
lated from the single-crystal X-ray data of compound 1 was
in good agreement with those that were observed (Fig-
ure 10), which indicates that compound 1 was obtained as
a single phase. After heating of compound 1 at 150 °C for
4 h, the guest water molecule was removed (the evacuated
framework is defined as 1Ј). The XRPD pattern of 1Ј is
similar to that of compound 1, although minor differences
can be seen in the positions, intensities, and widths of some
peaks, which indicates that the framework of compound 1
is retained after the removal of the guest molecule. Immer-
sion of the desolvated phase in H2O regenerated a sharper
XRPD pattern. Therefore the dehydration and rehydration
process is reversible for the material, and it belongs to
260 nm) for 5. Interestingly, a clear blueshift of the emission
occurs in 5. By comparison to the spectrum of the free N5
ligand,[18] the emission spectrum of 5 is tentatively assigned
to the intraligand (π–π*) fluorescence. The blue fluorescent
emission occurring in 3 and 5 suggests that they may be
used as new blue-light-emitting materials.
Conclusions
In conclusion, the simultaneous reaction of secondary li-
gands and V-shaped dicarboxylate ligands with d-block
metals affords a new type of interesting polymeric en-
tangled compounds. Notably, the first example of the
2DǞ3D interpenetrating structural feature observed in 2
illustrates again the aesthetic diversity of coordinative net-
work chemistry. Topological analysis of a series of related
complexes indicates that longer and flexible secondary li-
gands are liable to form previously unobserved topologies.
Also, the metal ion plays an important role in modulating
the resulting dimensionality and topology of the frame-
works. It is believed that more metal complexes containing
N-donor ligands and aromatic V-shaped polycarboxylate
with interesting structures as well as physical properties will
be synthesized.
Experimental Section
Abbreviations: bpa = 1,2-bis(4-pyridyl)ethane, bpe: 1,2-bis(4-pyr-
idyl)ethene, bpp: 1,3-bis(4-pyridyl)propane, dde = H2oba: 4,4Ј-oxy-
bis(benzoic acid), pcu: α-polonium.
Materials and Instruments: All reagents were purchased from com-
mercial sources and used as received. IR spectra were recorded with
a Perkin–Elmer Spectrum One spectrometer in the 4000–400 cm–1
range using KBr pellets. The luminescent spectra of the solid sam-
ples were acquired at ambient temperature with a JOBIN YVON/
HORIBA SPEX Fluorolog t3 system (slit: 0.2 nm). TGA was car-
ried out with
a Mettler–Toledo TA 50 in dry dinitrogen
(60 mLmin–1) at a heating rate of 5 °C min–1. XRPD data were
recorded with a Rigaku RU200 diffractometer at 60 KV, 300 mA
for Cu-Kα radiation (λ = 1.5406 Å), a scan speed of 2 °Cmin–1, and
a step size of 0.02° in 2θ.
Synthesis of the Complexes
{[M(oba)(bpe)]·H2O}n [M = Mn (1); Co (2)]: A mixture of
MnSO4·6H2O (0.021 g, 0.11 mmol), dde (0.029 g, 0.1 mmol), bpe
(0.025 g, 0.1 mmol), NaOH (0.5 , 0.4 mL), and deionized water
Figure 10. Comparison of XRPD patterns of the simulated pattern
from the single-crystal structure determination, the as-synthesized
product, and the desolvated and resolvated phases in compound 1.
152
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 147–154

Ligand and Metal Effects on Assembly of Metal-Organic Frameworks
(10 mL) was stirred for 20 min in air, then transferred and sealed
in a 23-mL Teflon reactor, which was heated at 150 °C for 48 h.
The solution was then cooled to room temperature at a rate of
5 °Ch–1 to yield a very fine pale yellow crystalline product (1) in
50% yield based on Mn. C26H20MnN2O6 (511.38): calcd. C 61.29,
[1]
a) S. R. Batten, R. Robson, Angew. Chem. Int. Ed. 1998, 37,
1460–1494; b) V. A. Blatov, L. Carlucci, D. M. Proserpio, Crys-
tEngComm 2004, 6, 377–395; c) I. A. Baburin, V. A. Blatov, L.
Carlucci, G. Ciani, D. M. Proserpio, J. Solid State Chem. 2005,
178, 2471–2493; d) L. Carlucci, G. Ciani, D. M. Proserpio, Co-
ord. Chem. Rev. 2003, 246, 247–289; e) X.-H. Bu, M.-L. Tong,
H. C. Chang, S. Kitagawa, S. R. Batten, Angew. Chem. Int. Ed.
2004, 43, 192–196; f) M.-L. Tong, X.-L. Chen, S. R. Batten, J.
Am. Chem. Soc. 2003, 125, 16170–16171; g) A. N. Khlobystov,
A. J. Blake, N. R. Champness, D. A. Lemenovskii, A. G. Ma-
jouga, N. V. Zyk, M. Schröder, Coord. Chem. Rev. 2001, 222,
155–192; h) B. Moulton, M. J. Zaworotko, Chem. Rev. 2001,
101, 1629–1658.
a) S. R. Batten, CrystEngComm 2001, 3, 67–73; b) B. F. Abra-
hams, S. R. Batten, M. J. Grannas, H. Hamit, B. F. Hoskins,
R. Robson, Angew. Chem. Int. Ed. 1999, 38, 1475–1477; c)
O. R. Evans, W. Lin, Acc. Chem. Res. 2002, 35, 511–512; d)
O. M. Yaghi, M. O’Keeffe, N. W. Ockwig, H. K. Chae, M. Ed-
daoudi, J. Kim, Nature 2003, 423, 705–714; e) S. R. Batten, J.
Solid State Chem. 2005, 178, 2475–2479; f) P. D. Akrivos, Co-
ord. Chem. Rev. 2001, 213, 181–210; g) H. Fleischer, Coord.
Chem. Rev. 2005, 249, 799–827.
H 3.56, N 5.50; found C 61.52, H 3.28, N 5.62. IR (KBr): ν = 3469
˜
(m), 3063 (w), 2298 (w), 1618 (m), 1597 (s), 1405 (vs), 1273 (m),
1064 (m), 882 (vs), 608 (m), 517 (w) cm–1. The synthesis of 2 was
performed using the same procedure as for complex 1 except that
MnSO4·6H2O was replaced by CoSO4·7H2O (0.027 g,0.1 mmol).
Yield: 58% based on Co. C26H20CoN2O6 (515.37): calcd. C 60.59,
H 3.91, N 5.44; found C 59.88, H 4.11, N 5.23. IR (KBr): ν = 3461
˜
(m), 3058 (w), 2297 (w), 1607 (m), 1589 (s), 1410 (vs), 1275 (m),
1058 (m), 881 (vs), 605 (m), 508 (w) cm–1.
[2]
[M(oba)(N3)]n [M = Cd (3), Cu (4)]: Synthetic procedures similar
to that for 1 were used. Yield: 52% based on Cd. C24H17CdN3O5
(539.81): calcd. C 53.39, H 3.17, N 7.78; found C 53.88, H 3.41, N
7.70. IR (KBr): ν = 1608 (vs), 1552 (s), 1443 (s), 1224 (m), 858 (s)
˜
cm–1. C24H17CuN3O5 (490.95): calcd. C 58.83, H 3.29, N 8.58;
found C 53.88, H 3.34, N 7.75. Yield: ca. 55% based on Cu. IR
(KBr): ν = 1605 (vs), 1558 (s), 1446 (s), 1218 (m), 879 (s) cm–1.
˜
[3]
[4]
[5]
http://www.chem.monash.edu.au/staff/sbatten/interpen/
(ac-
{[Zn(oba)(N5)]·2H2O}n (5): A synthetic procedure similar to that
for 1 was used. Yield: 49% based on Zn. C29H25N5O7Zn (620.91):
calcd. C 56.10, H 4.06, N 11.28; found C 56.87, H 3.68, N 11.40.
cessed 21/12/07).
D. P. Martin, R. M. Supkowski, R. L. LaDuca, Inorg. Chem.
2007, 46, 7917–7922.
S. R. Batten, R. Robson, in Molecular Catenanes, Rotaxanes
and Knots, A Journey Through the World of Molecular Topology
(Eds.: J.-P. Sauvage, C. Dietrich-Buchecker), Wiley-VCH,
Weinheim, 1999, 77–105.
a) J.-K. Lu, M.-A. Lawandy, J. Li, Inorg. Chem. 1999, 38, 2695–
2704; b) C.-D. Wu, C.-Z. Lu, W.-B. Yang, S.-F. Lu, H.-H.
Zhuang, J.-S. Huang, Eur. J. Inorg. Chem. 2002, 41, 797–800;
c) R. Cao, D.-F. Sun, Y.-C. Liang, M.-C. Hong, K. Tatsumi,
Q. Shi, Inorg. Chem. 2002, 41, 2087–2094; d) S. Konar, P. S.
Mukherjee, E. Zangrando, F. Lloret, N. R. Chaudhuri, Angew.
Chem. Int. Ed. 2002, 41, 1561–1563.
a) Z. Y. Fu, X. T. Wu, J. C. Dai, L. M. Wu, C. P. Cui, S. M.
Hu, Chem. Commun. 2001, 1856–1857; b) L. Carlucci, G. Ci-
ani, D. M. Proserpio, S. Rizzato, Chem. Eur. J. 2002, 8, 1520–
1526; c) P. Ayyappan, O. R. Evans, W. Lin, Inorg. Chem. 2002,
41, 3328–3330; d) K. Biradha, M. Fujita, Chem. Commun.
2002, 1866–1867; e) Y. H. Li, C. Y. Su, A. M. Goforth, K. D.
Shimizu, K. D. Gray, M. D. Smith, H. C. zur Loye, Chem.
Commun. 2003, 1630–1631; f) L. Carlucci, G. Ciani, D. M.
Proserpio, Chem. Commun. 2004, 380–381; g) X. M. Chen,
G. F. Liu, Chem. Eur. J. 2002, 8, 4811–4817; h) M. Kondo, Y.
Irie, M. Miyazawa, H. Kawaguchi, S. Yasuc, K. Maeda, F.
Uchida, J. Organomet. Chem. 2007, 692, 136–141.
a) M. Fujita, O. Sasaki, K. Watanabe, K. Ogura, K. Yama-
guchi, New J. Chem. 1998, 22, 189–191; b) L. Carlucci, G. Ci-
ani, M. Moret, D. M. Proserpio, S. Rizzato, Angew. Chem. Int.
Ed. 2000, 39, 1506–1510; c) X. L. Wang, Q. Chao, E. B. Wang,
Z. M. Su, Chem. Eur. J. 2006, 12, 2680–2691.
a) O. D. Friedrichs, M. O’Keeffe, O. M. Yaghi, Acta Crys-
tallogr., Sect. A 2003, 59, 22; b) http://rcsr.anu.edu.au; c) X. L.
Wang, C. Qin, E.-B. Wang, Y.-G. Li, Z.-M. Su, Chem. Com-
mun. 2005, 5450–5452; d) H. K. Lee, D. W. Min, B. Y. Cho,
S. W. Lee, Bull. Korean Chem. Soc. 2004, 25, 1959–1962.
a) S. Leininger, B. Olenyyuk, P. J. Stang, Chem. Rev. 2000, 100,
853–908; b) B. Moulton, M. J. Zaworotko, Chem. Rev. 2001,
101, 1629–1658; c) J. Heo, Y. Jeon, C. A. Mirkin, J. Am. Chem.
Soc. 2007, 129, 7712–7713; d) Y. G. Li, N. Hao, E. B. Wang,
Y. Lu, C. W. Hu, L. Xu, Eur. J. Inorg. Chem. 2003, 2567–2571;
e) Q. Chu, G. X. Liu, Y. Q. Huang, X. F. Wang, W. Y. Sun,
Dalton Trans. 2007, 4302–4311; f) C. Y. Niu, B. L. Wu, X. F.
Zheng, H. Y. Zhang, H. W. Hou, Y. Y. Niu, Z. J. Li, Cryst.
Growth Des. 2008, 8, 1566–1574; g) M. Du, X. J. Jiang, X. J.
Zhao, Inorg. Chem. 2007, 46, 3984–3995; h) J. Zhang, E. Chew,
IR (KBr): ν = 13443 (v), 3303 (s), 1621 (vs), 1558 (s), 1448 (s),
˜
1217 (m), 871 (s) cm–1.
X-ray Crystallography: Single-crystal X-ray diffraction studies of
1–5 were performed with a Bruker SMART APEX II CCD dif-
fractometer equipped with graphite-monochromated Mo-Kα radia-
tion (λ = 0.71073 Å) by using an ω-2θ scan technique at room
temperature. The structures were solved by direct methods and suc-
cessive Fourier difference synthesis (SHELXS-97),[19] and refined
using the full-matrix least-squares method on F2 with anisotropic
thermal parameters for all non-hydrogen atoms (SHELXL-97).[20]
The positions of the H atoms for pyridyl rings, benzene rings and
–NH groups were generated by a riding model on idealized geome-
tries, while the H atoms of water molecules were located in differ-
ence Fourier maps. In the case of 2, the final value is not ideal,
which may be attributed to the quality of the crystal. Notably, the
goodness-of-fit for compound 4 was only 0.513, which was also
attributed to the quality of the crystal. The crystallographic data
and other pertinent information for 1–5 are summarized in Table 2.
Selected bond lengths and bond angles are listed in Table 1.
[6]
[7]
Crystallographic data for the structural analysis have been de-
posited with the Cambridge Crystallographic Data Centre:
CCDC-692071 (for 1), -692072 (for 2), -692072 (for 3), and -692074
(for 4) -692075 (for 5). These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[8]
[9]
Supporting Information (see also the footnote on the first page of
this article): Description of the 4-crossing [2]-catenane motif, TG
curve for 1, and luminescence spectra for 3 and 5.
[10]
Acknowledgments
We gratefully acknowledge financial support of this work by the
National Natural Science Foundation of China (20471048 and
20771090), Teaching and Research Award Program for Outstand-
ing Young Teachers in Higher Education Institutes (TRAPOYT),
and Specialized Research Fund for the Doctoral Program of
Higher Education (SRFDP) (20050697005).
Eur. J. Inorg. Chem. 2009, 147–154
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
153

J.-Q. Liu, Y.-Y. Wang, Y.-N. Zhang, P. Liu, Q.-Z. Shi, S. R. Batten
FULL PAPER
S. M. Chen, J. T. H. Pham, X. H. Bu, Inorg. Chem. 2008, 47, [16] L. Carlucci, G. Ciani, D. M. Proserpio, S. Rizzato, Cryst-
3459–3497.
EngComm 2002, 4, 121–129.
[17] a) S. Kitagawa, R. Kitaura, S. Noro, Angew. Chem. Int. Ed.
2004, 43, 2334–2375; b) S. Kitagawa, K. Uemura, Chem. Soc.
Rev. 2005, 34, 109–119.
[11]
[12]
F. Li, Z. Ma, Y. L. Wang, R. Cao, W. H. Bi, X. Li, Cryst-
EngComm 2005, 7, 569–574.
J. Q. Liu, Y. Y. Wang, L. F. Ma, G. L. Wen, Q. Z. Shi, S. R.
[18] M. A. Braverman, R. M. Supkouski, R. L. LaDuca, J. Solid
State Chem. 2007, 180, 1852–1862.
[19] G. M. Sheldrich, Acta Crystallogr., Sect. A 1990, 46, 467.
[20] G. M. Sheldrick, SHELXL-97, Program for Structure Determi-
nation and Refinement, University of Göttingen, Göttingen,
1997.
Batten, D. M. Proserpio, CrystEngComm 2008, 10, 1123–1125.
[13] C. Y. Sun, X. J. Zheng, S. Gao, L. C. Li, L. P. Jin, Eur. J. Inorg.
Chem. 2005, 4150–4159.
[14] J. Q. Liu, Y. Y. Wang, L. F. Ma, F. Zhong, X. R. Zeng, W. P.
Wu, Q. Z. Shi, Inorg. Chem. Commun. 2007, 10, 979–982.
[15] P. Liu, Y. Y. Wang, D. S. Li, H. R. Ma, Q. Z. Shi, G. H. Lee,
S. M. Peng, Inorg. Chim. Acta 2005, 358, 3807–3814.
Received: September 8, 2008
Published Online: November 27, 2008
154
www.eurjic.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2009, 147–154