Coordination polymers of various architectures built with mixed imidazole/benzimidazole and carboxylate donor ligands and different metal ions: Syntheses, structural features and magnetic properties

Article abstract of DOI:10.1039/c0nj00302f

Ten coordination polymers {[Cd(L₁)₂]}_n (1), {[Cu(L₁)₂]}_n (2), {[Cd₂(L ₁)₂(HCOO)₂(H₂O)]}_n (3), {[Cd₂(L₁

Full text of DOI:10.1039/c0nj00302f

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PAPER
www.rsc.org/njc | New Journal of Chemistry
Coordination polymers of various architectures built with mixed
imidazole/benzimidazole and carboxylate donor ligands and different
metal ions: syntheses, structural features and magnetic propertieswz
Arshad Aijaz,a Prem Lama,a E. Carolina Sanudo,b Rupali Mishraa and
Parimal K. Bharadwaj*a
Received (in Victoria, Australia) 20th April 2010, Accepted 8th August 2010
DOI: 10.1039/c0nj00302f
Ten coordination polymers {[Cd(L1)2]}n (1), {[Cu(L1)2]}n (2), {[Cd2(L1)2(HCOO)2(H2O)]}n (3),
{[Cd2(L1)4]ꢀ3H2O}n (4), {[Cd(L1)(CH3COO)]}n (5), {[Cd(L1)2(C5H5N)]ꢀ2.5H2O}n (6), {[Zn(L2)2]}n
(7), {[Cd2(L2)4]ꢀH2O}n (8), {[Cd3(L2)6(H2O)]ꢀ2EtOHꢀH2O}n (9) and {[Cd(L3)2]ꢀ2DMFꢀ4H2O}n
(10), where HL1 = 4-imidazole-1-yl-benzoic acid, HL2 = 3-imidazole-1-yl-benzoic acid and
HL3 = 4-benzmidazole-1-yl-benzoic acid, have been synthesized under different experimental
conditions. Their structures are determined by single-crystal X-ray diffraction analyses and further
characterized by IR spectra, thermogravimetric (TG) and elemental analyses. The structure of 1 is
a 2D - 2D (2D = two dimensional) interpenetrating network with (4,4) grid topology while 2
has an interesting Kagome structure. Compounds 4 and 6 crystallize in 4- and 3-fold
interpenetrating diamondoid frameworks respectively. Compound 7 is a layered non-
interpenetrating (4,4) grid network whereas 8 has an unprecedented self-penetrating structure with
2D framework. Compound 9 is a self-penetrating 3D structure while 10 crystallizes in a
non-interpenetrating (4,4) square-grid with one-dimensional (1D) channels. From these results,
it is demonstrated that the structures of the coordination polymers are strongly dependent on the
geometry of L1, L2 and reaction conditions. Variable temperature magnetic susceptibility study of
2 has also been performed.
of new functional materials. However, at times, finding
Introduction
strategies to prepare a designed solid-state architecture can
The rational design of new coordination polymers is of
be highly empirical, and obtaining a phase with the desired
enormous current interest because of their potential applica-
organization of components becomes a trial and error process.
tions in several contemporary problems.1–5 During the past
Coordination polymer structures can be synthesized by hydro-
decade, judicious combination of organic ligands as ‘‘spacers’’
(solvo)thermal or room temperature reactions between metal
and metal ions as ‘‘nodes’’ have been the common synthetic
ions and multi-dentate ligands. In most cases, it may not be
approach to produce coordination polymers.6 In particular, a
possible to predict the structural pattern by looking at the ligand
structure while, in a few cases, unexpected reactions10 such as
large number of noteworthy 2D and 3D frameworks containing
cavities with diverse sizes and shapes have been engineered by
ligand oxidative coupling, hydrolysis or substitution, can occur
the assembly of ditopic ligands and square planar or octa-
making it almost impossible to predict the final structure.
hedral metal centers.7 So far, the synthetic focus in this area of
However, such ligand transformations provide alternate routes
research has been centered on the exploitation of the rod-like
for the construction of new coordination polymers.
and symmetrically bridging ligands.8 Use of unsymmetrical
It has been noted that coordination complexes with in situ
ligands, possessing two or more coordination sites with
generated ligands are of great interest both in coordination
different donor ability, can be assembled around metal centers
chemistry and organic chemistry for discovery of new organic
in diverse arrangements, resulting in structures with novel
reactions and understanding the reaction mechanisms, as well
topological features.9 The development and identification of
as for preparation of network architectures that are usually
inaccessible via direct use of the ligands.11 However, there is
novel solid-state architectures is a general theme in the pursuit
presently very little understanding concerning the factors that
a Chemistry Department, Indian Institute of Technology, Kanpur,
208016, India. E-mail: pkb@iitk.ac.in; Fax: (+91)-512-2597436;
Tel: (+91)-512-2597304
determine their synthesis and the attainment of rational control
over desired topologies. In fact, we were unable to generate some
of the polymers like (4,4) net with similar type of ligands under
same or different conditions via direct use of the ligand, but those
were obtained by in situ cyanide hydrolysis.
b
´
Departament de Quımica Inorganica, Universitat de Barcelona,
Diagonal, 647, 08028-Barcelona, Spain
`
w This article is part of a themed issue on Coordination polymers:
structure and function.
z Electronic supplementary information (ESI) available: Additional
figures and selected bond distances and bond angles. CCDC reference
numbers 773576–773585. For ESI and crystallographic data in CIF or
other electronic format see DOI: 10.1039/c0nj00302f
Herein, we have chosen ligands with imidazole/benzimidazole
and carboxylate donors at the terminals (Scheme 1). These
ligands are an extension of our previously reported ligand.12
The ligands are chosen because they have (1) rotatable single
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conditions and high temperatures, the rate of the reaction
increases dramatically. Introduction of imidazoles in the
ligands can have subtle influences on crystal packing.
By judicious control of reaction conditions, ten coordination
polymers with different metal ions have been successfully
achieved.
The ligands L4 and L5 show the characteristic nitrile
stretching at B2230 cmꢁ1 in the IR spectra. This peak is absent
in the respective coordination polymers14 and at the same
time, each polymer exhibits strong absorption in the region,
1350–1550 cmꢁ1 diagnostic of coordinated carboxylate.15
Scheme
1 Ligands used for the construction of coordination
polymers.
Structure of {[Cd(L1)2]}n, (1)
Single-crystal X-ray analysis reveals that 1 forms a (4,4) grid
structure. The metal ion lies on a 2-fold axis, adopts an
octahedral geometry with equatorial ligation from four
O atoms from two carboxylates bound to the metal in
asymmetric chelating fashion (Cd–O, 2.261–2.451 A) and axial
ligation from two imidazole N (Cd–N = 2.261 A). Thus, each
Cd(II) is connected to four different L1ꢁ1 ligands (Fig. 1a). The
ligands are bonded to other Cd(II) centers generating a square-
grid (4, 4) net as a 2D sheet (Fig. 1b). The grid size of 16.53 ꢂ
16.44 A2 and the two independent angles of 104.69 and 113.051
are described by a 40-membered Cd4(L1)4 macrocyclic ring.
Two such square grid sheets interpenetrate in a parallel
manner (Fig. 2a) such that the Cd atom of one layer is located
in middle of the grid of the second interpenetrating layer.
These 2D interpenetrated sheets stack in —AA— fashion
through noncovalent interactions to form an overall 3D
structure. There is no open channel and no solvent molecules
are found in the lattice of 1 (Fig. 2b).
C–N bond(s) that impart a variety of topological structures,
(2) rigid rod-like nature that is potentially attractive for having
porous structures and (3) carboxylate groups that help to
create neutral frameworks without anions in the pores. We
have synthesized a series of coordination polymers with these
linkers and different transition metal ions under hydro/
solvothermal conditions. A variety of geometries including
interpenetrated/non-interpenetrated square grids, distorted
(4,4) net, layer, Kagome, diamondoid and self-penetrating
2D and 3D frameworks have been observed and rationalized
them with respect to various ligands and reaction conditions
used. Variable temperature magnetic susceptibility measurement
of one of the compounds is also reported.
Results and discussion
The ligands are chosen such that there is the possibility of
rotational motion of arene-imidazole C–N bonds to adopt
different conformations and generate different coordination
polymer structures.13 It is known that nitriles can be hydrolyzed
to carboxylic acids and ammonia. In neutral conditions, the
rate of this reaction is slow, whereas under basic or acidic
Structure of {[Cu(L1)2]}n, (2)
Single-crystal X-ray analysis reveals that 2 has a Kagome
structure16 with 1D hexagonal open channels. Here, the
Fig. 1 (a) Coordination environment around Cd(II) center in 1 and (b) View of the single (4,4) net.
c
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report18 a Kagome structure has been reported with Cu(II) and
the present ligand with subtle differences.
Structure of {[Cd2(L1)2(HCOO)2(H2O)]}n, (3)
Compound 3 is a 3D mixed ligand coordination polymer with
in situ generated formate anions. Single-crystal X-ray analysis
reveals two crystallographically independent Cd(II) ions, two
L1ꢁ1, two formate anions and one coordinated water molecule
in the asymmetric unit. The formate comes from the hydrolysis
of DMF under high pressure and temperature, which has
been widely reported in the literature.19 The two Cd(II) ions
(both octahedral) are bridged by carboxylate to form a
bimetallic unit (Cd1—Cd2 sꢁe1paration, B3.692 A) and are
further connected by two L1 ligands to generate a zig-zag
chain along the crystallographic b-axis (Fig. 5). The Cd–O and
Cd–N bond distances are normal within statistical errors when
compared with reported values.20
Fig. 2 (a) Schematic view of the parallel 2-fold and (b) Crystal
packing along b-axis in 1.
This structure shows two bridging modes of formate anions
in a single structure with a rare mono-bridging mode. The
zig-zag chains are connected with (syn, anti) formate anions in
both crystallographic a and c directions to generate a 3D
coordination polymer with no embedded guest molecules
(Fig. 6).
Fig. 3 (a) Coordination environment around Cu(II) center in 2 and
(b) View of the 2D Kagome net.
asymmetric unit contains one Cu(II) ion (half occupancy) and
one L1ꢁ1. Like in the case of 1, distorted octahedral Cu(II) is
coordinated by two imidazole N (Cu–N = 1.978 A) and two
asymmetrically chelated carboxylates (Cu–O = 1.971–2.663 A)
from four different organic L1ꢁ1 ligands (Fig. 3a). Each Cu(II)
ions lie on an inversion center, has four Cu(II) ions as
neighbors to generate a Kagome net as a two dimensional
sheet showing Cu. . .Cu distances of 11.747 A (length of arms)
and 23.494 A as the diagonal Cu. . .Cu distance in the hexa-
gonal rings (Fig. 3b).
Fig. 5 Cꢁo1ordination environment around Cd(II) center in 3 (only
partial L1 are given for clarity).
These 2D layers stack over each other in —ABCABC—
fashion to generate a three dimensional structure with open
channels when viewed along c-axis (Fig. 4). The solvent
accessible volume for 2, calculated with the PLATON17
program, is 20.4% of the total unit cell volume. In a recent
Fig. 4 (a) Schematic representation of —ABCABC— stacking of
Kagome layers and (b) Crystal packing along c-axis with 1D channels
in 2.
Fig. 6 Crystal packing along b-axis in 3.
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Structure of {[Cd2(L1)4]ꢀ3H2O}n, (4)
This compound crystallizes in the chiral triclinic space group
ꢁ1
P1. The asymmetric unit contains two Cd(II) ions, four L1
and three water molecules. In this structure, each metal ion
shows a distorted octahedral geometry (Fig. 7a) with ligation
from two chelating carboxylates (Cd–O, 2.333–2.417 A) and
two imidazole nitrogens (Cd–N, 2.256–2.276 A) to form an
adamꢁan1tane type architecture containing 10 Cd(II) ions and
12 L1 ligands (Fig. 7b).
The generated adamantanoid moieties make 4-fold inter-
penetration, although the resulting 3D network contains voids
that are filled with guest water molecules (Fig. 8).
While these water molecules are H-bonded to the neighboring
carboxylate O (B2.8 A), weak p. . .p stacking interactions
between aromatic moieties are also present. The solvent acces-
sible volume for 4, calculated by PLATON as 21.2% of the total
unit cell volume.
Fig. 8 View of the 3D structure along a-axis with open channels in 4
(guest water molecules in channels are omitted for clarity).
Structure of {[Cd(L1)(CH3COO)]}n, (5)
The asymmetric unit here contains two crystallographically
independent Cd(II) ions (both half occupancy) lie on the same
2-fold axis, one L1ꢁ1 and one acetate. One of the metal ions is
distorted octahedrally coordinated with equatorial ligation by
two chelating carboxylates (Cd–O, 2.321–2.373 A) and axial
ligation by two imidazole nitrogens (Cd–N, 2.253 A). The
other metal ion shows 8-coordination with ligation from
four chelating carboxylates (Cd–O, 2.228–2.764 A) (Fig. 9a).
The polyhedra generated around Cd(II) centers are shown in
Fig. 9b.
Fig. 9 (a) Coordination environment around Cd(II) centers and
(b) Polyhedra generated around metal centers in 5.
Cd(II) (half occupancy), one L1ꢁ1, half of the pyridine and 1.25
water molecules. Cd(II) ion and distorted pyridine molecule lie
on the same 2-fold axis. The metal ion shows distorted penta-
gonal bipyramidal geometry (Fig. 11) with bonding from two
chelating carboxylates (Cd–O, 2.400–2.488 A), two imidazole N
(Cd–N, 2.279 A) and the pyridine N (Cd–N, 2.328 A).
This dinuclear motif is repeated along b-axis to generate a
1D chain that is further connected with L1ꢁ1 linkers to form a
2D coordination polymer (Fig. 10a). Also, stacking of these
2D layers one over the other in —ABCDE— fashion generates
a packed 3D supramolecular architecture (Fig. 10b).
The network structure of 6 is similar to that of 4 except that
octahedral Cd(II) is replaced by pentagonal bipyramidal
Cd(II) (Fig. 12a). Interestingly, the diamondoid network
possesses 3-fold interpenetration instead of 4-fold due to the
Structure of {[Cd(L1)2(C5H5N)]ꢀ2.5H2O}n, (6)
This compound crystallizes in the non-centrosymmetric tetra-
gonal space group P43212. The asymmetric unit contains one
Fig. 7 (a) Coordination environment around Cd(II) center in 4 and (b) View of the single adamantane composed of Cd10L1(12) unit in 4.
c
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Fig. 10 (a) View of the single 2D network and (b) Crystal packing along b-axis in 5.
coordinated pyridine molecules which itself occupy some of the
space in spacious single net. Fig. 12b shows how coordinated
pyridine molecules occupy the voids in the framework.
Structure of {[Zn(L2)2]}n, (7)
This compound crystallizes in the non-centrosymmetric
orthorhombic space group Aba2. The asymmetric unit con-
ꢁ1
ꢁ1
tains one Zn(II) and two L2 ligands. The L2 ligands are
generated through hydrolysis during hydrothermal reaction.
The metal ion shows distorted tetrahedral coordination with
bonding from two monodentate carboxylate and two imidazole
N (Fig. 13).
All Zn–O and Zn–N bond distances are within normal
statistical errors21 as found in other Zn(II) complexes. Zn(II)
ions along with the ligand L2ꢁ1 form a Zn6(L2)6 macrocycle in
the form of an open-book. These macrocyclic units form a parallel
self-interpenetrated 2D network (Fig. 14). These independent
Fig. 11 Coordination environment around Cd(II) center in 6.
Fig. 12 (a) A single diamondoid framework and (b) 3D structure along c-axis where channels are occupied by coordinated pyridine molecules in 6.
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Fig. 13 Coordination environment around Zn(II) center in 7.
Fig. 15 Coordination environment around Cd(II) center in 8.
Fig. 16 (a) Single (4,4) net in 8 and (b) Space filling model of
that net.
Fig. 14 Single self-penetrating 2D sheet in 7.
2D networks stack in —ABAB— fashion to generate an
overall 3D structure.
As reported by Sun et al.9d Zn(II) polymer with HL1 is a 2D
interpenetrated (4,4) net, meta-substituted analogue HL2
forms a self-penetrated 2D coordination polymer. Still we
have tried same experimental methods in both cases but did
not able to get self-penetrated structure with L1 which
confirm the crucial role of the nature of organic ligands to
obtain specific supramolecular structures. While few 3D self-
penetrated structures are known22 in the literature, self-
penetrated 2D coordination polymers are still rare.23
Fig. 17 Schematic view of the (a) stacking of layers and (b) non-
interpenetrating layer structure along b-axis in 8.
identical nets stacked over one another in —ABAB— fashion
are held together by week p. . .p interactions (B3.7 A) with an
interlayer spacing of B3.6 A calculated by considering the van
der Waals radii of atoms. These two 2D-layers are further
stacked in —ABAB— fashion and connected through
H-bonds with coordinated carboxylate O atoms and trapped
water molecules (OW1–O, 2.813–2.874 A), where the spacing
between two sets of the layers is B4.2 A to generate an overall
3D structure.
Structure of {[Cd2(L2)4]ꢀH2O}n, (8)
Compound 8 crystallizes in the monoclinic space group
P21/c as a non-interpenetrated 2D net. The asymmetric unit
ꢁ1
contains two Cd(II) ions, four L2 and one water molecule.
Each metal ion is distorted octahedral with coordination
from two chelating carboxylates and two imidazole N
(Fig. 15). The overall structure is a (4,4) net having the grid
size (considering diagonals of two opposite metal centers) of
17.5 ꢂ 10.7 A2 (Fig. 16).
On comparison with the structure of 1 which is double
interpenetrated, 8 is non-interpenetrated presumably due to
the angular nature of the donor atoms in L2ꢁ1. Also, strong
p. . .p interactions between aromatic rings of two layers in 8
can stabilize the structure without interpenetration.
Two different types of interactions and spacing exist in
between layers. As shown in Fig. 17, two layers composed of
c
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Structure of {[Cd3(L2)6(H2O)]ꢀ2EtOHꢀH2O}n, (9)
The asymmetric unit in this structure contains three crystallo-
bonded equatorially to two bridging carboxylates (Cd1–O,
2.206–2.776 A) and axially to two imidazole N (Cd1–N,
2.210–2.279 A) from four different ligand moieties.
The Cd(2) is 7-coordinated with two chelating carboxy-
lates (Cd2–O, 2.275–2.523 A), one bridging carboxylate
(Cd2–O, 2.805 A) and two imidazole nitrogens (Cd2–N,
2.264–2.296 A). The third Cd(II) ion is bonded to two chelating
carboxylates (Cd3–O, 2.351–2.511 A), two imidazole N
(Cd3–N, 2.304–2.309 A) and one water molecule (Cd3–OW1,
2.296 A) (Fig. 18a).
ꢁ1
graphically independent Cd(II), six L2 ligands, one metal
bound water molecule besides one water and two ethanol
molecules in the lattice. Each Cd(II) ion shows a different
coordination geometry. Distorted octahedral Cd(1) is
Overall, the structure is a 3D self-penetrating coordination
polymer in which free ethanol and water solvent molecules are
trapped. Fig. 18b illustrates how self-penetration occurs in this
ꢁ1
structure. The angular nature of ligand L2 plays a crucial
role for self-penetration. It is interesting to note here that pH
of the reaction medium has a profound effect on the structure
of the coordination polymer, as under basic conditions 2D
self-penetrating structure 8 was isolated, and under neutral
conditions 3D self-penetrating structure 9 was isolated.
Fig. 18 (a) Coordination environment around Cd(II) centers.
(b) View of the self-penetration in the 3D structure of 9.
Structure of {[Cd(L3)2]ꢀ2DMFꢀ4H2O}n, (10)
The asymmetric unit in 10 contains one Cd(II) ion which lies
ꢁ1
on a 2-fold axis, two L2 besides one DMF and two water
molecules in the lattice. The metal ion is distorted octahedral
with coordination from two chelating carboxylates (Cd–O,
2.312–2.372 A) and two imidazole N (Cd–N, 2.285 A)
(Fig. 19). The overall structure is a 2D coordination polymer
with (4,4) net having rhombic grid size of 18.29 ꢂ 16.26 A2
(diagonal) (Fig. 20a).
Due to bulky nature of the benzimidazole moiety and
high capacity of p. . .p stacking with aromatic rings, these 2D
layers are stacked one over the other to generate a non-
interpenetrated 3D structure with open channels along the
c-axis. These channels are filled with guest DMF and water
molecules (Fig. 20b). The solvent accessible volume for 10,
Fig. 19 Coordination environment around Cd(II) center in 10.
Fig. 20 Schematic view of the (a) 2D layers and (b) space filling model with 1D channels along c-axis in 10.
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calculated with the PLATON program, is 41.6% of the total
unit cell volume.
weight loss of 2.0% corresponding to one water molecule
(calculated, 1.8%) and the 2D framework is stable up to
350 1C. Compound 9 shows a weight loss of 8.0% (calculated,
7.0%) corresponding to 2C2H5OH + H2O starting at 90 1C
and continuing up to B300 1C. The framework is stable up to
B380 1C. Finally, compound 10 shows weight loss in two
stages beginning at 50 1C and continuing up to 180 1C showing
a total loss of 29% (calculated, 27%) corresponding to two
DMF and four water molecules. The framework is, however,
stable up to B360 1C.
It is obvious from the above descriptions that the nature of
ligands and reaction conditions has significant effects on the
final structures of the resulting complexes. As demonstrated
by a comparison of Cd(II) complexes 1 and 8, doubly inter-
penetratꢁed1 and non-interpenetrated (4,4) net were separated
ꢁ1
with L1
and L2
respectively under neutral and basic
ꢁ1
conditions. Similarly comparison of Zn(II) complexes of L1
reported by Sun et al.9d and L2ꢁ1 have doubly interpenetrated
and self-penetrated architectures with tetrahedral metal centers.
ꢁ1
ꢁ1
Magnetic properties
Basically linear and angular nature of L1 and L2 causes
the distinctness of the coordination environment around
metal centers and finally results in the formation of different
structures. Also, angular or bent nature is helpful to stabilize
the structure through strong p. . .p interactions between
aromatic rings of two layers and prevent interpenetration. In
addition, reaction conditions have a significant effect on the
structures, as evidenced by the fact that the structures of 4
and 9 are significantly different, even though the reaction
Variable temperature magnetic susceptibility data for com-
pound 2 are collected with an applied DC field of 1.0 T in the
2 to 300 K temperature range. The wT product at 300 K has a
value of 0.39 cm3 K molꢁ1 per Cu(II) ion, in agreement with
the value expected for an isolated Cu(II) ion (wT = 0.375 cm3
K molꢁ1 at 300 K, S = 1/2 and g = 2.0). As temperature
decreases, the wT product (circles in Fig. 21) remains nearly
constant, and then decreases sharply at temperatures below
10 K.
ꢁ1
conditions are the same. But under basic conditions, L2
generates (4,4) net structure without interpenetration. It
should be nꢁo1ted that we didn’t successfully isolate the
crystals of L2 with metal ions via direct use of HL2. Under
high temperature and pressure the CN functional groups get
hydrolyzed slowly to corresponding carboxylic acid and
generates the metal bound coordination polymers, which
highlights the importance of in situ generated ligands. Further-
more, the comparison of 10 with 1 and 8 shows that the
increase of bulky and high capacity of p. . .p stacking in
organic ligands may exert an important influence on the
formation of resulting diverse structures.
This indicates that the Cu(II) ions in 2 are magnetically
isolated from their neighbours in the solid state. This is not
surprising and can be expected from the structure of com-
pound 2. The Cu(II) ions are bridged by the ligand at a
In addition to the aforementioned coordination polymers,
we have also tried to synthesize coordination polymers
with other transition metal ions under different experimental
conditions, butꢁo1 nly Zn(II) and Co(II) bound coordination
polymers of L1 were separated. These structures have the
same doubly interpenetrated (4,4) net structures as 1 with
tetrahedrally coordinated metal centers as reported in the
literature, while other cases generate amorphous powders with
unknown compositions.
Fig. 21 Temperature dependence of the magnetic susceptibility for
compound 2.
Thermogravimetric analysis
In order to examine thermal stabilities of these compounds,
TG analyses are carried out in N2 atmosphere at the rate of
5 1C per minute. The thermograms are shown in the Support-
ing Informationz.14 The TGA curves of 1, 2, 5 and 7 show no
weight loss and they decompose at various temperatures but
not before 400 1C. Compound 3 shows a weight loss of 2.5%
due to removal of one H2O molecule (calculated, 2.54%) and
starts to decompose at B290 1C. Compound 4, on the other
hand, shows a weight loss of 5.5% due to removal of 3H2O
(calculated, 5.26%) and the framework starts to decompose at
B310 1C. Compound 6 shows a weight loss in stages – first a
loss of 6% due to 3H2O starting at 80 1C and then a loss of
B16% starting at 290 1C due to metal-bound pyridine. The
framework starts to decompose at B310 1C as coordinated
pyridine molecule is liberated. TGA of compound 8 shows a
Fig. 22 Field dependence of the magnetization for compound 2. The
solid line is the Brillouin curve for S = 1/2 and g = 2.0.
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distance of 11.747 A. Fig. 22 shows field dependence of
magnetization which follows the Brillouin law, as expected
for an isolated Cu(II).
Synthesis of 3-imidazole-1-yl-benzoic acid (HL2). This com-
pound was synthesized similar to HL1. A mixture containing
imidazole (1.1 mmol), ethyl-3-fluorobenzoate (1 mmol) and
K2CO3 (1.5 mmol) in 10 mL of N,N0-dimethyl formamide
(DMF) was heated at 100 1C for 48 h with constant stirring.
After removal of solvent under reduced pressure, the residue
was washed with water and the compound extracted with ethyl
acetate. Removal of ethyl acetate afforded a colorless oily
product as the ester. It was hydrolyzed by boiling in 5%
aqueous ethanolic NaOH solution for 10 h. Acidification with
1N HCl afforded the desired acid as a white solid which was
washed several times with water and dried in air. Yield: 63%.
Conclusion
We have utilized rigid ditopic organic linkers for the synthesis
of ten coordination polymers with different metal ions. These
ditopic ligands have a strong ability to bind with metal ions
and tendency to show the flexibility that can generate a variety
of supramolecular architecture. The nature of the metal ions
and organic ligands is the key to synthesize these polymers,
even using similar conditions. We have shown interpenetrated/
noninterpenetrated (4,4) nets, Kagome net, 3-fold and 4-fold
diamondoid nets and self-penetrating 2D and 3D nets with
complete structural characterization. Interesting self-penetrating
2D and 3D polymers were separated under in situ cyanide
hydrolysis and structural comparison was demonstrated with
similar type of ligands.
Synthesis of 4-benzmidazole-1-yl-benzoic acid (HL3). The
ligand HL3 was synthesized adopting a procedure as in case
of HL2. A mixture of benzimidazole (1.1 mmol), ethyl-4-
fluorobenzoate (1 mmol) and K2CO3 (1.5 mmol) in 10 mL
of DMF were heated at 100 1C for 48 h with constant stirring.
Thereafter, all the solvent was removed under reduced
pressure, the residue was washed with water and the com-
pound extracted with ethyl acetate. Removal of ethyl acetate
afforded a crude product that was recrystallized from methanol
to obtain the ester as a pale yellow crystalline solid. The acid
was obtained by hydrolyzing the ethyl ester in aqueous ethanol
containing 5% NaOH followed by acidification with 1N HCl.
The desired acid precipitates as a pale-brown solid. Yield:
71%. 1H-NMR, d (ppm): 8.6 (s, 1H), 8.13–8.12 (d, 2H),
7.8–7.78 (d, 2H), 7.76–7.74 (d, 1H), 7.69–7.68(d, 1H),
7.35–7.29 (q, 2H).
Experimental
Materials and methods
Ethyl-4-fluorobenzoate, 4-fluorobenzonitrile, ethyl-3-fluoro-
benzoate, 3-fluorobenzonitrile and metal salts were purchased
from Aldrich and used as received. All solvents, imidazole,
benzimidazole and K2CO3 were procured from S. D. Fine
Chemicals, India. All solvents were purified prior to use.
Synthesis of 4-imidazole-1-yl-benzonitile (L4). This ligand
was synthesized following a reported procedure.24
Physical measurements
Infrared spectra were recorded on a Perkin-Elmer Model
1320 spectrometer (KBr disk, 400–4000 cmꢁ1). 1H-NMR were
recorded on a JEOL JNM-LA500 FT (500 MHz) instrument
in DMSO-d6 with Me4Si as the internal standard. ESI mass
spectra were recorded on a WATERS Q-TOF Premier mass
spectrometer. X-Ray powder patterns were obtained using a
Phillips PW 100 X-ray generator (Cu-Ka radiation at a scan
rate of 31/min, 293 K), while thermogravimetric analyses
(TGA) were carried out on a Mettler Toledo thermal analyzer
(heating rate of 5 1C minꢁ1). Microanalyses for the com-
pounds were carried out using a CE-440 elemental analyzer
(Exeter Analytical Inc.).
Synthesis of 3-imidazole-1-yl-benzonitile (L5). A mixture of
imidazole (1.1 mmol), 3-fluorobenzonitrile (1 mmol) and
K2CO3 (1.5 mmol) in 10 mL of DMF were heated at 100 1C
for 48 h with constant stirring. After cooling to room tempera-
ture, the mixture was poured slowly into ice-water (100 ml)
with constant stirring. The precipitated white solid was
collected by filtration, washed with water and dried in air.
The crude product was recrystallized from methanol to get
needle like crystals. Yield: 46%. 1H-NMR, d (ppm): 8.4
(s, 1H), 8.18 (s, 1H), 7.98–7.96 (dd, 1H), 7.8 (s, 1H),
7.77–7.75(d, 1H), 7.68–7.65 (t, 1H), 7.09 (s, 1H); ESI-MS:
m/z (80%) 170.0673 [M + 1]+.
Magnetic susceptibility data (2–300 K) were collected at
the Unitat de Mesures Magnetiques at the Universitat de
Barcelona using crushed crystals of the sample on a Quantum
Design MPMS-XL SQUID magnetometer equipped with a 5T
magnet. The data were corrected for temperature independent
paramagnetism (TIP) and the diamagnetic corrections were
calculated using Pascal’s constants; an experimental correction
for the sample holder was applied.
Synthesis of {[Cd(L1)2]}n, (1). A mixture of Cd(NO3)2ꢀ6H2O
(0.50 mmol) and HL1 (0.25 mmol) in H2O (4 ml) was placed in
a Teflon-lined stainless steel autoclave, and heated to 180 1C
for 72 h. After the mixture was cooled to room temperature at
the rate of 0.1 1C minꢁ1, colorless crystals of 1 were collected,
washed with water and dried at room temperature to give 38%
yield based on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 1: C, 49.35%;
H, 2.89%; N,11.51%. Found: C, 49.13%; H, 3.01%;
N,11.73%. IR (cmꢁ1): 3134(s), 1604(m), 1548(m), 1394(m),
1302(s), 1237(s), 1169(s), 1116(m), 1061(m), 1015(s), 962(s),
931(s), 852(m), 832(s), 783(m), 748(s), 721(s), 699(s), 656(m).
Synthesis
All syntheses were carried out in dinitrogen atmosphere unless
otherwise mentioned.
Synthesis of {[Cu(L1)2]}n, (2). A mixture of Cu(NO3)2ꢀ6H2O
(0.50 mmol), 4-imidazole-1-yl-benzoic acid ethyl ester12
(0.25 mmol) and aq. NH3 (0.1 ml) in dist. H2O (4 ml) were
Synthesis of 4-imidazole-1-yl-benzoic acid (HL1). This ligand
was synthesized following a reported procedure.12
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placed in a Teflon-lined stainless steel autoclave and heated to
180 1C for 72 h. After the mixture was cooled to room
temperature at the rate of 0.1 1C minꢁ1, colorless crystals of
2 were collected, washed with water and dried at room
temperature to give 31% yield based on Cu(NO3)2ꢀ6H2O.
Anal. calcd. for 2: C, 54.85%; H, 3.22%; N, 12.79%. Found:
C, 55.17%; H, 3.41%; N, 12.47%. IR (cmꢁ1): 3164(w),
3143(s), 2923(w), 1689(m), 1689(s), 1609(w), 1577(s),
1500(m), 1421(s), 1361(m), 1273(m), 1230(m), 1177(m),
1150(m), 1133(m), 1119(m), 1096(m), 1062(m), 964(m),
948(m), 875(s),846(m), 782(m), 745(m), 700(s), 660(s), 644(s).
IR (cmꢁ1): 3578(w,br), 3360(s), 2985(s), 1585(m), 1539(s),
1481(s), 1391(m), 1240(m), 1211(m), 1163(m), 1012(s), 976(m),
924(s), 852(m), 800(m), 780(m), 749(m), 718(m), 641(s).
Synthesis of {[Zn(L2)2]}n, (7). A mixture of Zn(NO3)2ꢀ6H2O
(0.50 mmol) and L5 (0.25 mmol) in H2O (4 ml) were placed in a
Teflon-lined stainless steel autoclave and heated to 180 1C for
72 h. After the mixture was cooled to room temperature at the
rate of 0.1 1C minꢁ1, colorless crystals of 7 were collected,
washed with water and dried at room temperature to obtain
30% yield of the product based on Zn(NO3)2ꢀ6H2O. Anal.
calcd. for 7: C, 54.62%; H, 3.20%; N, 12.74%. Found: C,
54.46%; H, 3.39%; N, 12.50%. IR (cmꢁ1): 3147(w), 3123(m),
3065(w), 3037((w), 1620(s), 1583(s), 1515(s), 1452(m), 1375(s),
1352(s), 1243(m), 1144(m), 1066(s), 989(w), 947(s), 901(m),
858(m), 823(m), 766(s), 732(s), 684(s).
Synthesis of {[Cd2(L1)2(HCOO)2(H2O)]}n, (3). A mixture of
Cd(NO3)2ꢀ6H2O (0.50 mmol) and HL1 (0.25 mmol) in
DMF–H2O (4 ml, 3 : 1 v/v) were placed in a Teflon-lined
stainless steel autoclave and heated to 110 1C for 48 h. After
the mixture was cooled to room temperature at the rate of
0.1 1C minꢁ1, colorless crystals of 3 were collected, washed
with water and dried at room temperature to give 49% yield
based on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 3: C, 37.36%; H,
2.56%; N, 7.92%. Found: C, 37.27%; H, 2.68%; N, 7.77%.
IR (cmꢁ1): 3398(br), 3124(m), 1606(s), 1568(w), 1523(m),
1402(s), 1308(m), 1267(w), 1188(w), 1121(m), 1062(m),
961(m), 932(w), 857(m), 782(s), 746(w), 695(w), 643(m).
Synthesis of {[Cd2(L2)4]ꢀH2O}n, (8). A mixture of Cd(NO3)2ꢀ
6H2O (0.50 mmol), L5 (0.25 mmol) and aq. NH3 (0.1 ml) in
EtOH–H2O (4 ml, 1 : 1 v/v) were placed in a Teflon-lined
stainless steel autoclave and heated to 180 1C for 72 h. After
the mixture was cooled to room temperature at the rate of 0.1
1C minꢁ1, colorless crystals of 8 were collected, washed with
water and dried at room temperature to get 44% yield based
on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 8: C, 48.45%; H, 3.04%;
N, 11.30%. Found: 48.51%; H, 2.91%; N, 11.46%. IR (cmꢁ1):
3141(s), 3101(s), 1577(m), 1512(m), 1447(m), 1397(m), 1325(s),
1247(m), 1115(m), 1064(m), 989(s), 935(m), 868(m), 824(m),
771(m), 736(m), 689(m), 651(m).
Synthesis of {[Cd2(L1)4]ꢀ3H2O}n, (4).
A mixture of
Cd(NO3)2ꢀ6H2O (0.50 mmol) and L4 (0.25 mmol) in
EtOH–H2O (4 ml, 1 : 1 v/v) were placed in a Teflon-lined
stainless steel autoclave and heated to 180 1C for 72 h. After
the mixture was cooled to room temperature at the rate of
0.1 1C minꢁ1, colorless crystals of 4 were collected, washed
with water and dried at room temperature to give 13% yield
based on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 4: C, 46.75%; H,
3.33%; N, 10.90%. Found: C, 46.92%; H, 3.42%; N, 10.76%.
IR (cmꢁ1): 3403(br), 3134(m), 1607(s), 1549(m), 1524(m),
1402(s), 1304(m), 1263(m), 12185(m), 1063(s), 1014(w),
963(m), 934(w), 857(m), 783(m), 740(w), 697(w), 650(w).
Synthesis of {[Cd3(L2)6(H2O)]ꢀ2EtOHꢀH2O}n, (9).
A
mixture of Cd(NO3)2ꢀ6H2O (0.50 mmol) and L5 (0.25 mmol)
in EtOH–H2O (4 ml, 1 : 1 v/v) were placed in a Teflon-lined
stainless steel autoclave and heated to 180 1C for 72 h. After
the mixture was cooled to room temperature at the rate of
0.1 1C minꢁ1, colorless crystals of 9 were collected, washed
with water and dried at room temperature to give 35% yield
based on Zn(NO3)2ꢀ6H2O. Anal. calcd. for 9: C, 48.39%; H,
3.68%; N, 10.58%. Found: C, 48.22%; H, 3.49%; N, 10.43%.
IR (cmꢁ1): 3401(w,br), 3111(s), 1554(m), 1511(s), 1448(s),
1396(m), 1261(s), 1115(s), 1063(m), 933(s), 867(s), 828(s),
772(m), 734(m), 688(s), 655(s).
Synthesis of {[Cd(L1)(CH3COO)]}n, (5). A mixture of
Cd(OAc)2ꢀ6H2O (0.50 mmol), L4 (0.25 mmol) and aq. NH3
(0.1 ml) in EtOH–H2O (4 ml, 1:1v/v) were placed in a Teflon-
lined stainless steel autoclave and heated to 180 1C for 72 h.
After the mixture was cooled to room temperature at the rate
of 0.1 1C minꢁ1, colorless crystals of 5 were collected, washed
with water and dried at room temperature to give 42% yield
based on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 5: C, 40.18%; H,
2.81%; N, 7.81%. Found: C, 40.03%; H, 2.93%; N, 7.91%.
IR (cmꢁ1): 3107(s), 2928(s), 1606(m), 1537(s), 1511(s),
1418(m), 1345(s), 1305(s), 1261(s), 1224(m), 1172(m),
1106(s), 1067(m), 855(s), 820(s), 781(m), 728(s), 698(s), 640(m).
Synthesis of {[Cd(L3)2]ꢀ2DMFꢀ4H2O}n, (10). A mixture of
Cd(NO3)2ꢀ6H2O (0.50 mmol) and HL3 (0.25 mmol) in DMF
(3 ml) were placed in a Teflon-lined stainless steel autoclave
and heated to 100 1C for 72 h. After the mixture was cooled to
room temperature at the rate of 0.1 1C minꢁ1, colorless filtrate
was put in open air. Block shaped crystals of 10 were collected
within 2 h in 31% yield based on Cd(NO3)2ꢀ6H2O. Anal. calcd.
for 10: C, 50.72%; H, 5.01%; N, 10.43%. Found: C, 50.52%;
H, 5.14%; N, 10.23%. IR (cmꢁ1): 3408(s), 3304(s), 3112(s),
3017(s), 2921(s), 2816(s), 2737(s), 1636(m), 1598(s), 1541(m),
1467(s), 1416(s), 1331(m), 1209(s), 1112(s), 1049(m), 1088(m),
973(s), 950(m), 902(s), 842(m), 847(m), 741(m), 688(s), 615(m).
Synthesis of {[Cd(L1)2(C5H5N)]ꢀ2.5H2O}n, (6). Hot DMF
solution of HL1 (0.25 mmol, 5 ml) and pyridine (0.1 ml) were
added slowly into a hot aqueous solution of Cd(NO3)2ꢀ6H2O
(0.50 mmol in 2 ml H2O) with constant stirring. The mixture
left stirring at room temperature for 2 h. Then the solution was
filtered and the filtrate left for crystallization. Colorless
crystals of 6 were collected after 10 days in 29% yield based
on Cd(NO3)2ꢀ6H2O. Anal. calcd. for 6: C, 48.43%; H, 4.06%;
N, 11.29%. Found: C, 48.66%; H, 3.92%; N, 11.15%.
X-Ray structural studies
Single crystal X-ray data were collected at 100 K on a Bruker
SMART APEX CCD diffractometer using graphite-
monochromated Mo-Ka radiation (l = 0.71073 A). Linear
c
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c
2512 New J. Chem., 2010, 34, 2502–2514 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010

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absorption coefficients, scattering factors for the atoms and
the anomalous dispersion corrections were taken from Inter-
national Tables for X-ray Crystallography. Data integration
and reduction were processed with SAINT25 software. An
empirical absorption correction was applied to the collected
reflections with SADABS26 using XPREP.27 The structure
was solved by the direct method using SHELXTL28 and
refined on F2 by full-matrix least-squares technique using the
SHELXL-97 program package. The non-hydrogen atoms
were refined anisotropically except OW2 in 6. Hydrogen atoms
attached to carbon atoms were positioned geometrically and
treated as riding atoms using SHELXL default parameters,
while hydrogen atoms of water molecules were located from
difference Fourier maps and refined freely keeping the O–H
bond distances constrained to B0.85 A with the DFIX
command. However, one hydrogen of OW3 in 4, both
hydrogens of OW1 and OW2 in 6 and hydroxyl proton of
one EtOH solvent molecule in 9 could not be located even in
successive difference Fourier maps due to their distorted
nature. Also, due to distorted nature of pyridine molecule in
6, several DIFIX and DANG commands were used to fix it.
The crystal and refinement data are collected in Table 1 while
selective bond distances and angles are given in Table S1
(Supporting Informationz).14
6 (a) S. K. Ghosh, J. Ribas and P. K. Bharadwaj, Cryst. Eng.
Commun., 2004, 6, 250; (b) H. Chun, H. Jung and J. Seo, Inorg.
Chem., 2009, 48, 2043; (c) M. Eddaoudi, J. Kim, N. Rosi,
D. Vodak, J. Wachter, M. O’Keeffe and O. M. Yaghi, Science,
2002, 295, 469.
7 (a) J.-R. Li, D. J. Timmons and H.-C. Zhou, J. Am. Chem. Soc.,
2009, 131, 6368; (b) F. Luo, Y.-X. Che and J.-M. Zheng, Cryst.
Growth Des., 2009, 9, 1066; (c) N. L. Rosi, J. Kim, M. Eddaoudi,
B. Chen, M. O’Keeffe and O. M. Yaghi, J. Am. Chem. Soc., 2005,
127, 1504.
8 (a) S. Yang, X. Lin, A. Dailly, A. J. Blake, P. Hubberstey,
N. R. Champness and M. Schroder, Chem.–Eur. J., 2009, 15,
¨
4829; (b) D. Tanaka, S. Horike, S. Kitagawa, M. Ohba,
M. Hasegawa, Y. Ozawa and K. Toriumi, Chem. Commun.,
2007, 3142; (c) D. N. Dybtsev, H. Chun and K. Kim, Angew.
Chem., Int. Ed., 2004, 43, 5033.
9 (a) K. Uemura, Y. Kumamoto and S. Kitagawa, Chem.–Eur. J.,
2008, 14, 9565; (b) C. A. Black and L. R. Hanton, Cryst. Growth
Des., 2007, 7, 1868; (c) D. M. Shin, I. S. Lee, Y. K. Chung and
M. S. Lah, Inorg. Chem., 2003, 42, 5459; (d) Z. S. Bai, S. S. Chen,
Z. H. Zhang, M. S. Chen, G. X. Liu and W. Y. Sun, Sci. China
Chem., 2009, 52, 459.
10 (a) X.-M. Chen and M.-L. Tong, Acc. Chem. Res., 2007,
40, 162; (b) L. Han, X. Bu, Q. Zhang and P. Feng, Inorg. Chem.,
2006, 45, 5736; (c) X.-M. Zhang, Coord. Chem. Rev., 2005, 249,
1201.
11 (a) Y.-Q. Lan, S.-L. Li, Y.-G. Li, Z.-M. Su, K.-Z. Shao and
X.-L. Wang, CrystEngComm, 2008, 10, 1129; (b) H. Deng,
Y.-C. Qiu, Y.-H. Li, Z.-H. Liu, R.-H. Zeng, M. Zeller and
S. R. Batten, Chem. Commun., 2008, 2239; (c) Y.-T. Wang,
H.-H. Fan, H.-Z. Wang and X.-M. Chen, Inorg. Chem., 2005,
44, 4148.
12 A. Aijaz, E. Barea and P. K. Bharadwaj, Cryst. Growth Des., 2009,
9, 4480.
Acknowledgements
13 (a) J.-P. Zhang, Y.-Y. Lin, X.-C. Huang and X.-M. Chen, Chem.
Commun., 2005, 1258; (b) C.-Y. Chen, P.-Y. Cheng, H.-H. Wu and
H. M. Lee, Inorg. Chem., 2007, 46, 5691.
We gratefully acknowledge the financial support received from
the Department of Science and Technology, New Delhi, India
and a SRF from the CSIR to A. A and P.L. ECS acknow-
ledges the financial support from Spanish Government,
(Grant CTQ2006/03949BQU and Ramon y Cajal fellowship).
14 See Supporting Information (ESI)z.
15 (a) L. Lisnard, P. Mialane, A. Dolbecq, J. Marrot, J. M. Clemente-
Juan, E. Coronado, B. Keita, P. de Oliveira, L. Nadjo and
F. Secheresse, Chem.–Eur. J., 2007, 13, 3525; (b) X. Li, R. Cao,
W. Bi, Y. Wang, Y. Wang, X. Li and Z. Guo, Cryst. Growth Des.,
2005, 5, 1651; (c) X.-J. Li, X.-Y. Wang, S. Gao and R. Cao, Inorg.
Chem., 2006, 45, 1508.
References
16 (a) S. Horike, S. Hasegawa, D. Tanaka, M. Higuchi and
S. Kitagawa, Chem.Comm., 2008, 4436; (b) D.-C. Zhong,
W.-G. Lu, L. Jiang, X.-L. Feng and T.-B. Lu, Cryst. Growth
Des., 2010, 10, 739.
17 A. L. Spek, PLATON, Version 1.62, University of Utrecht, 1999.
18 X.-D. Chen, X.-H. Zhao, M. Chen and M. Du, Chem.-Eur. J.,
2009, 15, 11974.
19 (a) F. Dai, P. Cui, F. Ye and D. Sun, Cryst. Growth Des., 2010, 10,
1474; (b) L. H. Xie, S. X. Liu, B. Gao, C. D. Zhang, C. Y. Sun,
D. H. Li and Z. M. Su, Chem. Commun., 2005, 2402; (c) W. Chen,
J.-Y. Wang, C. Chen, Q. Yue, H.-M. Yuan, J.-S. Chen and
S.-N. Wang, Inorg. Chem., 2003, 42, 944.
20 (a) T. K. Maji, K. Uemura, H.-C. Chang, R. Matsuda and
S. Kitagawa, Angew. Chem., Int. Ed., 2004, 43, 3269; (b) L. Wen,
Z. Lu, J. Lin, Z. Tian, H. Zhu and Q. Meng, Cryst. Growth Des.,
2007, 7, 93.
21 (a) W.-P. Wu, Y.-Y. Wang, Y.-P. Wu, J.-Q. Liu, X.-R. Zeng,
Q.-Z. Shi and S.-M. Peng, CrystEngComm, 2007, 9, 753;
(b) H.-L. Gao, L. Yi, B. Zhao, X.-Q. Zhao, P. Cheng,
D.-Z. Liao and S.-P. Yan, Inorg. Chem., 2006, 45, 5980.
22 (a) L. Carlucci, G. Ciani, D. M. Proserpio and F. Porta, Angew.
Chem., Int. Ed., 2003, 42, 317; (b) S. R. Batten, CrystEngComm,
2001, 3, 67; (c) L.-P. Zhang, J.-F. Ma, J. Yang, Y.-Y. Pang and
J.-C. Ma, Inorg. Chem., 2010, 49, 1535.
23 (a) G. A. Farnum and R. L. LaDuca, Cryst. Growth Des., 2010,
10, 1897; (b) P.-K. Chen, Y. Qi, Y.-X. Che and J.-M. Zheng,
CrystEngComm, 2010, 12, 720; (c) D.-R. Xiao, Y.-G. Li,
E.-B. Wang, L.-L. Fan, H.-Y. An, Z.-M. Su and L. Xu, Inorg.
Chem., 2007, 46, 4158.
1 (a) H.
K Chae, D. Y. Siberio-Perez, J. Kim, Y. B. Go,
M. Eddaoudi, A. J. Matzger, M. O’Keeffe and O. M. Yaghi,
Nature, 2004, 427, 523; (b) C. Janiak, Dalton Trans., 2003, 2781;
(c) L. J. Murray, M. Dinca and J. R. Long, Chem. Soc. Rev., 2009,
38, 1294; (d) M. C. Das and P. K. Bharadwaj, J. Am. Chem. Soc.,
2009, 131, 10942; (e) J. J. Perry, IV, J. A. Perman and
M. J. Zaworotko, Chem. Soc. Rev., 2009, 38, 1400.
2 (a) P. Lama, A. Aijaz, E. C. Sanudo and P. K. Bharadwaj, Cryst.
Growth Des., 2010, 10, 283; (b) A. Aijaz, E. C. Sanudo and
P. K. Bharadwaj, Inorg. Chim. Acta, 2009, 362, 4246;
(c) E. Coronado, J. R. Galan-Mascaros and C. Marti-Gastaldo,
J. Am. Chem. Soc., 2008, 130, 14987; (d) J. T. Brockman,
T. C. Stamatatos, W. Wernsdorfer, K. A. Abboud and
G. Christou, Inorg. Chem., 2007, 46, 9160; (e) L. J. Murray,
M. Dinca and J. R. Long, Chem. Soc. Rev., 2009, 38, 1294.
3 (a) L. Ma, C. Abney and W. Lin, Chem. Soc. Rev., 2009, 38, 1248;
(b) J. Y. Lee, O. K. Farha, J. Roberts, K. A. Scheidt, S. B.
T. Nguyen and J. T. Hupp, Chem. Soc. Rev., 2009, 38, 1450;
(c) J. J. Vittal, Coord. Chem. Rev., 2007, 251, 1781.
4 (a) L. Zhang, Y.-Y. Qin, Z.-J. Li, Q.-P. Lin, J.-K. Cheng, J. Zhang
and Y.-G. Yao, Inorg. Chem., 2008, 47, 8286; (b) H. Han, Y. Song,
H. Hou, Y. Fan and Y. Zhu, Dalton Trans., 2006, 16, 1972;
(c) L. Han, M. Hong, R. Wang, J. Luo, Z. Lin and D. Yuan,
Chem. Commun., 2003, 20, 2580; (d) J. L. Atwood, L. J. Barbour
and A. Jerga, Angew. Chem., Int. Ed., 2004, 43, 2948.
5 (a) Q. Li, W. Zhang, O. S. Miljanic, C.-H. Sue, Y.-L. Zhao, L. Liu,
C. B. Knobler, J. F. Stoddart and O. M. Yaghi, Science, 2009, 325,
855; (b) B. Chen, L. Wang, F. Zapata, G. Qian and
E. B. Lobkovsky, J. Am. Chem. Soc., 2008, 130, 6718;
(c) M. Sarkar and K. Biradha, Cryst. Growth Des., 2007, 7, 1318.
24 J. M. Fevig, D. J. Pinto, Q. Han, M. L. Quan, J. R. Pruitt,
I. C. Jacobson, R. A. Galemmo, Jr., S. Wang, M. J. Orwat,
c
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View Article Online
L. L. Bostrom, R. M. Knabb, P. C. Wong, P. Y. S. Lam and
R. R. Wexler, Bioorg. Med. Chem. Lett., 2001, 11, 641.
25 SAINT + , 6.02ed.; Bruker AXS, Madison, WI, 1999.
26 G. M. Sheldrick, SADABS, Empirical Absorption Correction
27 XPREP, 5.1 ed. Siemens Industrial Automation Inc., Madison,
WI, 1995.
28 G. M. Sheldrick, SHELXL-97, Program for the Refinement of
Crystal Structures, University of Gottingen, Gottingen, Germany,
1997.
¨
¨
Program, University of Gottingen, Germany, 1997.
¨
c
2514 New J. Chem., 2010, 34, 2502–2514 This journal is The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2010