Syntheses and crystal structures of 1D tubular chains and 2D polycatenanes built from the asymmetric 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene ligand with metal salts

Article abstract of DOI:10.1039/b315842j

Reactions of a new asymmetric ligand, 1-(1-imidazolyl)-4-(imidazol-1- ymethyl)benzene (IIMB), with various metal [Cd(II), Mn(II), Zn(II)] salts led to the formation of molecular, one- (1D) and two-dimensional (2D) architectures [Cd(IIMB)₂(H₂O)(SO₄)]·7.5H₂O 1, [Cd(IIMB)₂Cl₂]·H₂O 2, [Cd(IIMB) ₄(H₂O)₂](NO₃)₂-5H ₂O 3, [Cd(IIMB)(OAc)₂]·H₂O 4, [Mn(IIMB)₂(SO₄)(H₂O)]·8.2H₂O 5, [Mn(IIMB)₄(H₂O)₂]Cl₂· 5H₂O 6 and [Zn(IIMB)₂]₄(NO₃) ₈·13.5H₂O 7. All the structures were established by single-crystal X-ray diffraction analysis. Both compounds 1 and 5 with sulfate anion are 2D polycatenanes formed by the interlocking of 1D double-stranded chains, while 2 and 4 with chloride and acetate anions are 1D chains. The results provide nice examples of topologies of metal-organic frameworks controlled by the counter anions. Interestingly, 3 and 6 are discrete molecular complexes with monometallic cores and form 2D networks through strong intermolecular hydrogen bonds. Complex 7, obtained under the same conditions as 3, is a 1D tubular chain. The structural difference between 3 and 7 suggests the metal ions also have a significant effect on the construction of supramolecular architectures. Furthermore, the photoluminescence properties of these compounds were investigated in the solid state at room temperature.

Full text of DOI:10.1039/b315842j

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P A P E R
Syntheses and crystal structures of 1D tubular chains and 2D
polycatenanes built from the asymmetric 1-(1-imidazolyl)-4-
(imidazol-1-ylmethyl)benzene ligand with metal saltsy
Hui-Fang Zhu,a Wei Zhao,a Taka-aki Okamura,b Jian Fan,a Wei-Yin Sun*a and
Norikazu Ueyamab
a
Coordination Chemistry Institute, State Key Laboratory of Coordination Chemistry, Nanjing
University, Nanjing 210093, P. R. China. E-mail: sunwy@nju.edu.cn
Department of Macromolecular Science, Graduate School of Science, Osaka University,
Toyonaka, Osaka 560-0043, Japan
b
Received (in Montpellier, France) 4th December 2003, Accepted 24th March 2004
First published as an Advance Article on the web 15th July 2004
Reactions of a new asymmetric ligand, 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)benzene (IIMB), with various
metal [Cd(II), Mn(II), Zn(II)] salts led to the formation of molecular, one- (1D) and two-dimensional (2D)
architectures [Cd(IIMB)2(H2O)(SO4)]ꢀ7.5H2O 1, [Cd(IIMB)2Cl2]ꢀH2O 2, [Cd(IIMB)4(H2O)2](NO3)2ꢀ5H2O 3,
[Cd(IIMB)(OAc)2]ꢀH2O 4, [Mn(IIMB)2(SO4)(H2O)]ꢀ8.2H2O 5, [Mn(IIMB)4(H2O)2]Cl2ꢀ5H2O 6 and
[Zn(IIMB)2]4(NO3)8ꢀ13.5H2O 7. All the structures were established by single-crystal X-ray diffraction analysis.
Both compounds 1 and 5 with sulfate anion are 2D polycatenanes formed by the interlocking of 1D double-
stranded chains, while 2 and 4 with chloride and acetate anions are 1D chains. The results provide nice examples
of topologies of metal-organic frameworks controlled by the counter anions. Interestingly, 3 and 6 are discrete
molecular complexes with monometallic cores and form 2D networks through strong intermolecular
hydrogen bonds. Complex 7, obtained under the same conditions as 3, is a 1D tubular chain. The structural
difference between 3 and 7 suggests the metal ions also have a significant effect on the construction of
supramolecular architectures. Furthermore, the photoluminescence properties of these compounds were
investigated in the solid state at room temperature.
Introduction
Construction of supramolecules with novel structures and
topologies have attracted great interest from chemists because
of their potential applications in material science, medicine,
chemical technology, etc.1 In the previous reports, there are
several strategies to construct pre-designed metal-organic
frameworks (MOFs),2 for example using rationally designed
organic ligands and/or elaborately chosen metal salts with
defined coordination geometries, introducing non-covalent
weak interactions such as hydrogen bonds, p-p interactions
or even hydrophobic forces.3 However, the self-assembly pro-
Scheme 1 Ditopic ligands bix, bimb and IIMB.
cess is complex and frequently influenced by factors such as
solvent, template, pH of solution, geometric requirements of
the metal ions, counter ions and even the synthesis conditions.4
Therefore, much more work is required to achieve information
of the relevant structural types and establish the proper rela-
tionship between the structures and properties. In the past dec-
ades, extensive work has been carried out and a variety of one-
(1D), two- (2D) and three-dimensional (3D) frameworks with
specific topologies and interesting properties have been
obtained. It has been recognized that the use of bridging
ligands to tune the supramolecular architectures has become
a key step during the self-assembly process. For example, the
flexible bridging ligand 1,4-bis(imidazole-1-ylmethyl)benzene
(bix, Scheme 1) gave an infinite 2D polyrotaxane network by
reaction with silver(I) nitrate or zinc(II) nitrate hexahydrate,
and an infinite 1D chain with manganese(II) nitrite.5 Recently,
an infinite 3D entanglement network was obtained by the reac-
tion of bix and cobalt sulfate.5d
We focus our attention on the design and synthesis of MOFs
with specific topologies and properties by using flexible imida-
zole-containing ligands such as 4,40-bis(imidazole-1-ylmethyl)-
biphenyl (bimb), 1,3,5-tris(imidazol-1-ylmethyl)benzene (TIB)
and
1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene
(TITMB).6 In our previous studies, the ligand bimb was synthe-
sized to detect the effect of p-p interactions on the formation of
the supramolecular architectures and to study the influence of
the spacer group on the MOFs.6a,b As an extension of our
studies,6,7 we have designed and prepared a new imidazole-
containing ligand, 1-(1-imidazolyl)-4-(imidazol-1-ylmethyl)-
benzene (IIMB), and its reactions with various metal salts were
carried out. In this paper, we report the syntheses, crystal
structures and photoluminescence properties of complexes
[Cd(IIMB)2(H2O)(SO4)]ꢀ7.5H2O (1), [Cd(IIMB)2Cl2]ꢀH2O (2),
y Electronic supplementary information (ESI) available: tables of
bonding parameters for compounds 1–7; additional figures of the crys-
tal structures; the excitation and emission spectra of compounds 1–4
and 7. See http://www.rsc.org/suppdata/nj/b3/b315842j/
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
1010
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8

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was added to a solution of IIMB (67.2 mg, 0.3 mmol) in
MeOH (20 mL). The mixture was stirred for ca. 10 min, then
filtered. The compound 3 was obtained by slow evaporation of
the filtrate at room temperature in 54% yield. Anal. Calcd for
C52H62CdN18O13 : C, 49.59; H, 4.96; N, 20.02. Found: C,
49.63; H, 5.01; N, 19.98%.
[Cd(IIMB)4(H2O)2](NO3)2ꢀ5H2O (3), [Cd(IIMB)(OAc)2]ꢀH2O
(4), [Mn(IIMB)2(SO4)(H2O)]ꢀ8.2H2O (5), [Mn(IIMB)4
(H2O)2]Cl2ꢀ5H2O (6) and [Zn(IIMB)2]4(NO3)8ꢀ13.5H2O (7)
obtained by reactions of IIMB with the corresponding metal
salts. To the best of our knowledge, compounds 1 and 5 are
the first examples of 2D polycatenanes formed by interlocking
of 1D double-stranded chains.
[Cd(IIMB)(OAc)2]ꢀH2O, 4. A solution of IIMB (44.8 mg, 0.2
mmol) and Cd(OAc)2ꢀ2H2O (53.3 mg, 0.2 mmol) in water (20
mL) was stirred for ca. 1.5 h at room temperature. Then the sol-
vent was removed under reduced pressure and the residue was
dissolved in N,N-dimethylformamide (DMF; 10 mL) and fil-
tered. Colorless single crystals of 4 suitable for X-ray diffraction
analysis were obtained by slow diffusion of diethyl ether into
the above filtrate at room temperature over several days. The
yield was ca. 51%. Anal. Calcd for C17H20CdN4O5 : C, 43.19;
H, 4.26; N, 11.85. Found: C, 43.33; H, 4.31; N, 11.86%.
Experimental
Materials and measurements
All commercially available chemicals are of reagent grade and
used as received without further purification. Solvents were
purified by standard methods prior to use. Elemental analyses
of C, H and N were taken on a Perkin–Elmer 240C elemental
analyzer, at the Center of Materials Analysis, Nanjing Univer-
1
sity. 500 MHz H NMR spectra were measured on a Bruker
DRX-500 NMR spectrometer at room temperature. The lumi-
nescent spectra for the powdered solid samples were recorded
at room temperature on an Aminco Bowman Series 2 spectro-
fluorometer with a xenon arc lamp as the light source. In the
measurements of emission and excitation spectra the pass
width was 5.0 nm. All the measurements were carried out
under the same experimental conditions.
[Mn(IIMB)2(SO4)(H2O)]ꢀ8.2H2O, 5.
A
solution of
MnSO4ꢀH2O (16.9 mg, 0.1 mmol) in water (10 mL) was added
to a solution of IIMB (44.8 mg, 0.2 mmol) in water (10 mL).
The mixture was stirred for ca. 20 min, then filtered. The
compound 5 was obtained by slow evaporation of the fil-
trate at room temperature in 75% yield. Anal. Calcd for
C26H42.43N8MnO13.22S: C, 40.79; H, 5.59; N, 14.64. Found:
C, 40.79; H, 5.53; N, 14.75%.
Syntheses
Synthesis of IIMB. The ligand 1-(1-imidazolyl)-4-(imidazol-
1-ylmethyl)benzene (IIMB) was synthesized by the Ullmann
condensation method between imidazole and 1-bromo-4-(imi-
dazol-1-ylmethyl)benzene, which was prepared by reaction of
4-bromobenzyl bromide with imidazole under alkaline condi-
tions.8 Reaction of imidazole (4.1 g, 60 mmol), sodium hydro-
xide (2.6 g, 65 mmol) and 4-bromobenzyl bromide (15.0 g, 60
mmol) in dimethylsulfoxide (DMSO; 80 mL) solution was
carried out following the procedures reported for preparation
of TITMB as described previously,8b to give 12.1 g (85%)
1-bromo-4-(imidazol-1-ylmethyl)benzene. 1-Bromo-4-(imidazol-
1-ylmethyl)benzene (12.1 g, 51 mmol), imidazole (3.0 g, 56
mmol), K2CO3 (7.8 g, 56 mmol) and CuSO4 (1.25 g, 5 mmol)
were mixed and heated at 180 ꢁC for 12 h under a nitrogen
atmosphere. After being cooled to room temperature, the reac-
tion mixture was washed by water and the residue was
extracted by CH2Cl2 (5ꢂ 30 mL). The organic layer was sepa-
rated, dried over sodium sulfate and evaporated to dryness to
give the crude product of IIMB, which was recrystallized from
[Mn(IIMB)4(H2O)2]Cl2ꢀ5H2O,
6.
A
solution
of
MnCl2ꢀ4H2O (9.9 mg, 0.05 mmol) in water (10 mL) was added
to a solution of IIMB (44.8 mg, 0.2 mmol) in water (10 mL).
The mixture was stirred for ca. 20 min, then filtered. The
compound 6 was obtained by slow evaporation of the fil-
trate at room temperature in 63% yield. Anal. Calcd For
C52H62Cl2N16MnO7 : C, 54.36; H, 5.44; N, 19.50. Found: C,
54.15; H, 5.52; N, 19.47%.
[Zn(IIMB)2]4(NO3)8ꢀ13.5H2O,
7.
A
solution
of
Zn(NO3)2ꢀ6H2O (29.7 mg, 0.1 mmol) in water (20 mL) was
added to a solution of IIMB (44.8 mg, 0.2 mmol) in MeOH
(10 mL). The mixture was stirred for ca. 10 min, then filtered.
The compound 7 was obtained by slow evaporation of the
filtrate at room temperature in 48% yield. Anal. Calcd for
C104H123N40O37.50Zn4 : C, 44.69; H, 4.44; N, 20.05. Found:
C, 44.75; H, 4.57; N, 19.86%.
Crystallographic analyses
1
dichloromethane and petroleum ether. Yield: 8.11 g (71%). H
The X-ray diffraction measurements for compounds 1–7 were
carried out on a Rigaku RAXIS-RAPID imaging plate dif-
fractometer at 200 K, using graphite-monochromated Mo-
Ka radiation (l ¼ 0.7107 A). The structures were solved by
NMR (500 MHz, D2O): d 7.89 (s, 1H), 7.65 (s, 1H), 7.34
(s, 1H), 7.32 (d, 2H), 7.23 (d, 2H), 7.02 (s, 1H), 7.01 (s, 1H),
6.90 (s, 1H), 5.12 (s, 2H). Anal. Calcd for C13H12N4 : C,
69.62; H, 5.39; N, 24.98. Found: C, 69.68; H, 5.50; N, 25.03.
˚
direct methods using SIR929 and expanded using Fourier tech-
niques.10 One of the lattice water molecules with the O6 atom
in 3 was disordered into two positions with site occupation fac-
tors of 0.672(11) and 0.328(11). The O3 atom (from one of the
uncoordinated water molecules) in 6 has two positions with
site occupation factors of 0.68(3) and 0.32(3). The O41, O42,
O43 atoms in 7 are part of one nitrate ion and have two posi-
tions with site occupation factors of 0.640(8) and 0.360(8). The
O83 and N8 atoms in 7 are part of one nitrate ion and have
two positions with site occupation factors of 0.640(8) and
0.360(8). The nitrate ion with O71, O72, O73 and N7 atoms
in 7 is disordered into two positions with site occupation
factors of 0.515(9) and 0.485(9). In addition, two imidazole
groups and two nitrate anions of 7 are also disordered into
two positions. All the non-hydrogen atoms were refined aniso-
tropically by the full-matrix least-squares method except for
the O43, N8, N8B atoms in 7, which were refined isotropically.
The crystal parameters, data collection and refinement results
for the compounds 1–7 are summarized in Table 1. Selected
[Cd(IIMB)2(H2O)(SO4)]ꢀ7.5H2O, 1. A solution of IIMB
(67.2 mg, 0.3 mmol) and CdSO4ꢀ2.7H2O (38.5 mg, 0.15 mmol)
in water (15 mL) was sealed in a stainless steel vessel and
placed in an oven at 120 ꢁC for 3 days. The resulting colorless
crystals of 1 were collected in 81% yield. Anal. Calcd for
C26H41CdN8O12.50S: C, 38.55; H, 5.10; N, 13.83. Found: C,
38.56; H, 4.96; N, 13.79%.
[Cd(IIMB)2Cl2]ꢀH2O, 2. A solution of IIMB (44.8 mg, 0.2
mmol) in ethanol (7 mL) was layered over a solution of
CdCl2ꢀ2.5H2O (22.8 mg, 0.1 mmol) in water (5 mL). Colorless
single crystals of 2 suitable for X-ray diffraction analysis were
obtained by slow inter-layer diffusion in 45% yield. Anal.
Calcd for C26H26CdCl2N8O: C, 48.00; H, 4.06; N, 17.21.
Found: C, 48.05; H, 4.03; N, 17.24%.
[Cd(IIMB)4(H2O)2](NO3)2ꢀ5H2O, 3.
A
solution of
Cd(NO3)2ꢀ4H2O (23.1 mg, 0.075 mmol) in water (10 mL)
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8
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T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
1012
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8

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bond length and angles are listed in Table S1 [Electronic sup-
plementary information (ESI)]. Further details are provided in
the ESI.z
Results
Description of crystal structures
.
[Cd(IIMB)2(H2O)(SO4)] 7.5H2O, 1. In contrast to the sym-
metric ligands bix and bimb (Scheme 1), IIMB is asymmetric
since one imidazole group is attached to the benzene group
via a methylene group and the other one is directly attached
to the benzene group. Novel MOFs with different structures
and topologies from those with bix and bimb ligands can be
expected by assembly reactions of IIMB with metal salts. As
II
illustrated in Fig. 1(a), each Cd center in compound 1 has a
slightly distorted octahedral environment and is coordinated
by four imidazole groups of four IIMB ligands with Cd1–N
˚
bond lengths in the range of 2.291(4)–2.327(4) A [Cd1–
11
II
˚
˚
Nav ¼ 2.310(15) A]. The Cd atom lies 0.11 A out from the
N4 plane towards the O11 atom; such a deviation may be
attributed to the different axial ligands (water molecule and
II
sulfate anion). Each IIMB ligand links two Cd atoms to form
a double-stranded 1D chain containing 24-membered rings
˚
with a Cdꢀ ꢀ ꢀCd intra-chain distance of 11.94 A [Fig. 1(b)]. In
each ring, the two benzene ring planes are parallel to each
other and are almost perpendicular to the chain plane defined
by the cadmium and methylene carbon atoms [Fig. 1(b)], since
the dihedral angles between them are 87.7 and 85.4ꢁ, respec-
tively. The distance between the two benzene ring planes
˚
within one 24-membered ring is 6.65 A, which makes it possi-
ble for an aromatic ring from another ligand to pass through
the ring. Therefore, the remarkable feature of 1 is that the
1D chains are interlaced with each other to generate a 2D poly-
catenane network structure (Fig. 2). In the interlocked 2D
structure, there are face-to-face p-p interactions between the
benzene ring planes with centroid-centroid separations ranging
˚
from 3.67 to 3.75 A (Fig. S1 in ESI). In addition, the oxygen
atoms of the coordinated SO4 anion form hydrogen bonds
with the coordinated water and with the imidazole ring C–H
2ꢃ
Fig. 2 (a) Wire-frame and (b) space-filling views of the 2D polycate-
nane network formed from independent double-stranded 1D chains
in 1.
from the adjacent interlaced chains. In addition, there are a
lot of O–Hꢀ ꢀ ꢀO hydrogen bonding interactions between the
2ꢃ
SO4 and water molecules, water and water molecules, and
C-Hꢀ ꢀ ꢀO hydrogen bonds between the imidazole ring C–H
and water molecules. The data on the hydrogen bonds are
summarized in Table S2 in the ESI. Such hydrogen bonds,
as well as p-p interactions, stabilize the interpenetrated struc-
ture and link the 2D sheets into a 3D structure (Fig. S2, ESI).
[Cd(IIMB)2Cl2]ꢀH2O, 2. When IIMB reacts with cadmium
chloride, instead of the sulfate salt, complex 2 was obtained.
II
Crystallographic study shows that the Cd center in 2 has a
Fig. 1 (a) A view of 1 showing the coordination environment around
II
the Cd center (ellipsoids at 30% probability). (b) A view of the double-
similar coordination environment as that in 1 except two
chloride ions, rather than sulfate anion and water molecule,
occupying the axial positions with a Cl1–Cd–Cl2 angle of
176.67(4)ꢁ [Fig. 3(a) and Table S1). The Cd1–N bond lengths
stranded 1D chain of 1. The hydrogen atoms and solvent molecules are
omitted for clarity.
˚
range from 2.313(3) to 2.371(3) A with Cd1–Nav of 2.343(29)
z CCDC reference numbers 204243–204244 and 225285–225289. See
http://www.rsc.org/suppdata/nj/b3/b315842j/ for crystallographic
data in .cif or other electronic format.
˚
A, which is slightly longer than that in compound
1
(Table S1). Complex 2 is also a hinged 1D chain containing
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8
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Fig. 3 (a) Crystal structure of compound 2 with atom numbering
scheme. The thermal ellipsoids are drawn at 30% probability. (b) Infi-
nite hinged 1D chain structure of 2. The hydrogen atoms and solvent
molecules are omitted for clarity.
24-membered rings with a Cdꢀ ꢀ ꢀCd intra-chain distance of
˚
12.91 A, which is longer than that in 1 [Fig. 3(b)]. However,
there are definite differences between complexes 1 and 2. In
contrast to the near perpendicular orientation of the benzene
ring planes to the chain plane in 1, the benzene ring planes
in 2 are nearly parallel to the chain plane since the dihedral
angles between the benzene ring plane and the chain plane
defined by cadmium and methylene carbon atoms are 13.0
and 11.5ꢁ, respectively. And the shortest Hꢀ ꢀ ꢀH distance
between two benzene rings within the 24-membered ring is
˚
2.94 A, which is too narrow for another ligand to pass through
Fig. 4 (a) Crystal structure of compound 3. (b) 2D network structure
the ring. As a result, the structure of 2 is a hinged 1D chain; no
interpenetration of 1D chains was observed. Instead, the 1D
chains are linked by two O–Hꢀ ꢀ ꢀCl, two C–Hꢀ ꢀ ꢀO and one
C–Hꢀ ꢀ ꢀCl hydrogen bonding interactions (Table S2) and weak
p-p interactions (the shortest centroid-centroid separation is
of 3 with hydrogen bonds indicated by the dashed lines. The IIMB
ligands that do not participate in the formation of O–Hꢀ ꢀ ꢀN hydrogen
bonds are omitted for clarity.
˚
to 2.998 A between the O atoms of water molecules or between
˚
4.26 A) to form a 3D structure (Fig. S3, ESI).
the O atoms of a water molecule and the O atom of a nitrate
anion indicate the formation of O–Hꢀ ꢀ ꢀO hydrogen bonds
(Table S2), although the hydrogen atoms of the water mole-
cules could not be found. The center-to-center distance of
4.17 A between the two nearest benzene ring planes indicates
the presence of weak p-p interactions in 3.
[Cd(IIMB)4(H2O)2](NO3)2ꢀ5H2O, 3. It is interesting that a
mononuclear complex 3 was obtained when cadmium nitrate
was used to react with IIMB. Fig. 4(a) shows a view of the
coordination environment of the metal atom in 3 with the
atom numbering scheme. It is clear that only the imidazole
group connected to the benzene ring through the methylene
˚
II
[Cd(IIMB)(OAc)2]ꢀH2O, 4. To further examine the impact
of the anion on the self-assembled structures, the reaction of
IIMB with cadmium acetate was carried out and a different
1D chain complex 4 was isolated. Fig. 5(a) exhibits the crystal
structure of 4 together with the atom numbering scheme. Each
group coordinates to the Cd atom, while the one connected
directly to the benzene ring is uncoordinated. In the complexes
1 and 2, each cadmium atom is coordinated by four N atoms,
two of which are from imidazole groups attached to the ben-
zene ring directly and the other two are from ones attached
to the benzene ring via the methylene group. The coordination
II
Cd atom is six-coordinated with a N2O4 , rather than N4O2 ,
donor set from two N atoms of imidazole groups from two dif-
II
geometry around the Cd atom is distorted octahedral with a
N4O2 binding set. The Cd1–N bond lengths range from
ferent IIMB ligands and two acetate anions in Z2-coordination
mode. Each IIMB ligand in turn links two Cd atoms to
generate a 1D sawtooth chain. The Cd1–N bond lengths
II
˚
˚
2.289(10) to 2.343(10) A [Cd1–Nav ¼ 2.318(23) A], and two
II
water molecules coordinated to the Cd atom are in a trans
˚
are 2.246(2) and 2.259(2) A, and the Cd1–O bond lengths
arrangement with bond lengths of Cd1–O1 ¼ 2.399(8), Cd1–
˚
are in the range of 2.311(2)–2.413(2) A with a Cd1–Oav of
˚
O2 ¼ 2.335(7) A (Table S1). Fig. 4(b) exhibits the infinite
˚
2.362(54) A. The crystal packing diagram of 4 shows that
2D network structure of 3 formed by intermolecular O–
Hꢀ ꢀ ꢀN hydrogen bonds, indicated by dashed lines, with
the 1D chains pack together through six C–Hꢀ ꢀ ꢀO hydrogen
bonds and two O–Hꢀ ꢀ ꢀO hydrogen bonds [Fig. 5(b) and
Table S2].
˚
Oꢀ ꢀ ꢀN distances of 2.76(1) A (Table S2). The oxygen and nitro-
gen atoms are from a coordinated water molecule and uncoor-
dinated imidazole group, respectively. The nitrate anions and
lattice water molecules are located in the voids formed between
two adjacent cationic layers, held there by eight C–Hꢀ ꢀ ꢀO
hydrogen bonds; the Cꢀ ꢀ ꢀO distances range from 3.02(2) to
[Mn(IIMB)2(SO4)(H2O)]ꢀ8.2H2O, 5. In addition to the
above mentioned cadmium(II) complexes, reactions of IIMB
with other metal salts were carried out to elucidate the
influence of the metal ion on the structures of the assemblies.
˚
3.440(14) A (Fig. S4 and Table S2). The distances of 2.099
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
1014
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8

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II
links two Mn centers to form a 1D chain with Mnꢀ ꢀ ꢀMn
˚
intra-chain distance of 12.04 A. The dihedral angles between
the benzene ring plane and the chain plane defined by manga-
nese and methylene carbon atoms are 86.5ꢁ and 84.3ꢁ, which
are similar to those observed in 1. The distance between the
˚
two benzene ring planes within the ring is 6.75 A, which is a
˚
little longer than that in 1 (6.65 A). There are many hydrogen
bonds stabilizing the interpenetrated structure and linking the
2D sheets into a 3D structure (Table S2). In addition, similar
face-to-face p-p interactions, with centroid-centroid separa-
˚
tions ranging from 3.63 to 3.88 A, were also detected for 5 such
as those in 1.
[Mn(IIMB)4(H2O)2]Cl2ꢀ5H2O, 6. When manganese chloride
was employed to react with IIMB, complex 6 was formed. The
X-ray crystallographic analysis revealed that the structure of 6
is mononuclear as that of 3, but different from that of 2. The
coordination environment and average bond length of Mn–
Nav are similar to those of the reported compound Mn(bix)3
(NO2)2ꢀ4H2O.5c The distorted octahedral Mn center with
II
N4O2 binding set is coordinated by four imidazole N atoms
connecting to the benzene group through the methylene groups
and two O atoms from two water molecules in a trans arrange-
ment. Complex 6 also forms a 2D network by an intermolecu-
lar O(coordinated water)–Hꢀ ꢀ ꢀN(uncoordinated imidazole
˚
group) hydrogen bond with an Oꢀ ꢀ ꢀN distance of 2.739(5) A.
The crystal packing diagram of 6 is illustrated in Fig. 7. Weak
overlap occurs between the benzene ring planes from two adja-
cent ligands, since the center-to-center distance between the
Fig. 5 (a) Infinite 1D chain structure of 4. The solvent molecules and
hydrogen atoms are omitted for clarity. (b) 3D structure of 4 linked by
hydrogen bonds.
˚
two nearest benzene ring planes is 4.17 A. The chloride anions
and lattice water molecules occupy the voids formed between
2D layers by forming hydrogen bonds (Table S2). No such
p-p interactions were reported in the related complex
Mn(bix)3(NO2)2ꢀ4H2O, which may be due to the greater
flexibility of bix compared to IIMB.5c
Complex 5 was obtained by reaction of IIMB with mangane-
se(II) sulfate and its structure, evidenced by crystallographic
analysis, is similar to that of 1 (Table 1), namely, a 2D polyca-
tenane composed of a slant interpenetrated 1D double-
II
stranded chains (Fig. 6). Each Mn center with distorted
octahedral geometry is coordinated by four imidazole groups
of four IIMB ligands with an average bond length of Mn1–
[Zn(IIMB)2]4(NO3)8ꢀ13.5H2O, 7. The crystal structure of
compound 7 is shown in Fig. 8. It is interesting that the zinc(II)
atom in 7 is four-coordinated rather than six-coordinated as
observed for the cadmium(II) and manganese(II) atoms in com-
˚
Nav ¼ 2.256(4) A, and by two O atoms from one water mole-
II
˚
cule and a sulfate anion. The Mn atom is displaced by 0.03 A
from the plane formed by the N4 donor set. Each IIMB ligand
II
plexes 1–6. Each Zn atom is coordinated by four N atoms of
four IIMB ligands with distorted tetrahedral geometry since
the N–Zn–N bond angles vary from 95.2(8)ꢁ to 123.3(4)ꢁ
II
(Table S1). This is similar to the Zn atoms in [Zn(bix)2
(NO3)2]ꢀ4.5H2O,5b in which the N–Zn–N bond angles vary
from 96.2(1)ꢁ to 125.0(1)ꢁ. It is noteworthy that there are four
II
zinc(II) atoms in one asymmetric unit of 7 [Fig. 8(a)]. Two Zn
atoms, e.g. Zn1 and Zn1B or Zn4A and Zn3B in Fig. 8(b),
are linked by two IIMB ligands to form a quadrangled
Fig. 6 A view of the 2D polycatenane network structure of 5 show-
ing the interpenetrated 1D chains with O–Hꢀ ꢀ ꢀO hydrogen bonds
indicated by the dashed lines.
Fig. 7 Crystal packing diagram of compound 6.
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8
1015

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Scheme 2 Schematic drawing of the structures of complexes 1 and 5,
2, and 7.
reported structures, the topology of interpenetration is that
the nodes of the nets lie in the centers of the rings, while
in the structures of 1 and 5, the links of the chains pass through
the rings of the interpenetrating chains.15 The doubled-
stranded 1D chains are interlaced with each other to form
the 2D network with angles of 85.1ꢁ and 78.1ꢁ between the
two inclined 1D chains for 1 and 5, respectively. The coordina-
tion of sulfate anions and water molecules may probably be
responsible for the formation of such a 2D polycatenated
structure. On one hand, compared with chloride or nitrate
anion, the sulfate anion has a large volume and its steric hin-
drance can subtly tune the orientation of the coordinated imi-
dazole groups around the metal atom as well as the orientation
of the benzene ring groups, which is different from those in
other complexes, e.g. in 2 and 6. On the other hand, the sulfate
anions and water molecules act as acceptors and donors of
hydrogen bonds. One O(coordinated water)–Hꢀ ꢀ ꢀO(sulfate
ion) hydrogen bond and one C(imidazole group)–Hꢀ ꢀ ꢀO
(sulfate ion) hydrogen bond play an important role in stabili-
zing the polycatenated structure. (2) The counter anions of com-
plex 2, namely two chloride ions, occupy the axial positions
of the metal atom and the structure of 2 is a 1D hinged chain,
which is similar to that of 1. But the relative orientations of the
benzene ring groups in the loop are different. The benzene ring
planes in complex 2 are nearly parallel to the chain plane with
dihedral angles of 13.0 and 11.5ꢁ, respectively. The corre-
sponding dihedral angles in complex 1 are 87.7 and 85.4ꢁ,
respectively, which indicates that the benzene ring planes are
almost perpendicular to the chain plane defined by the cad-
mium atoms and the methylene carbon atoms. As a result,
the space between the two benzene ring planes within the loop
in complex 1 is significantly larger than that in complex 2,
making room for another ligand to pass through. Thus, the
overall structures of 1 and 2 are obviously different (Scheme
2). (3) Complexes 3 and 6 are both discrete molecular com-
plexes with a monometallic core, though they have different
counter ions. The counter anions, nitrate ions (3) and chloride
ions (6), did not participate in the coordination with the metal
atoms and exist in the structure by forming hydrogen bonds.
(4) The acetate ions of complex 4 adopt a Z2 coordination
mode to coordinate to the metal atom, the structure is a single
1D chain. (5) The zinc(II) atom in complex 7 has a tetrahedral
coordination environment and is coordinated by four IIMB
ligands; the structure is a tubular 1D chain (Scheme 2).
Furthermore, it has been confirmed that the complexes can
be obtained under the same metal:ligand molar ratios of 1:2.
That is, the metal-to-ligand molar ratios did not affect the
structure greatly in this system. The different structures of
complexes 5 and 6, as well as 3 and 7, which were prepared
under the same experimental conditions, indicate that the nat-
ure of the counter anions and the geometric requirements of
the metal atoms play important roles in determining the struc-
ture and topology of MOFs.4e
Fig. 8 (a) Independent crystal structure of compound 7. (b) Two
independent tubular 1D chains of 7. The anions, solvent molecules
and hydrogen atoms are omitted for clarity.
24-membered ring similar to that observed in 2. Such macro-
cyclic rings are further interlinked by two IIMB ligands to
form an infinite 1D tube-like chain; four independent zinc
atoms in each asymmetric unit form two independent 1D
chains [Fig. 8(b)]. The 1D chain structure is similar to that
in the reported complex [(CuI)2(bpds)] [bpds ¼ bis(4-pyri-
1
dyl)disulfide],12 while the structure of [Zn(bix)2(NO3)2]ꢀ4.5H2O
is a 2D polyrotaxane, which may be attributed to the flex-
ibility of the bix ligand. The 1D chains are arranged in the
bc plane to form 2D sheets, which further stack together to
generate vacancies (Fig. S5 of the ESI), occupied by water
molecules and uncoordinated nitrate anions. There are many
C–Hꢀ ꢀ ꢀO and O–Hꢀ ꢀ ꢀO hydrogen bonds with Cꢀ ꢀ ꢀO and
˚
Oꢀ ꢀ ꢀO distances ranging from 2.812(14) to 3.490(17) A and
˚
from 2.312 to 2.991 A, respectively (Table S2) and weak p-p
interactions with centroid-centroid separations ranging from
˚
3.70 to 4.02 A.
Photoluminescence properties of the compounds
The photoluminescence properties of compounds 1–7 were stu-
died in the solid state at room temperature. The measurements
were carried out under the same experimental conditions and
the results are shown in Fig. S6 (see ESI). It is interesting that
compounds 1, 3 and 4 show luminescence with emission max-
ima at 455 ꢄ 2 nm upon excitation at 396 nm, while com-
pounds 2 and 7 exhibit photoluminescence with emission
maxima around 464 ꢄ 2 nm at the same excitation wavelength.
Though the structures of 5 and 6 are similar to complexes 1
and 3, respectively, no clear photoluminescence was observed
for 5 and 6 at room temperature. The luminescence emissions
of 5 and 6 are probably quenched by the Mn(II) ion. The emis-
sions observed in compounds 1, 2, 3, 4 and 7 are tentatively
assigned to the p-p* intraligand fluorescence due to their close
resemblance to the emission bands.13
Discussion
Seven new MOFs of ligand IIMB with different metal salts
were successfully synthesized. The X-ray crystallographic ana-
lysis revealed that these compounds have different structures.
(1) Both complexes 1 and 5 with a coordinated sulfate anion
have similar 2D polycatenated structures (Scheme 2). They
can be regarded as a completely new mode of 1D ! 2D
inclined interpenetration of double-stranded 1D chains, which
was predicted by Ciani et al. in a review.14 In the previously
In addition, in the complexes with six-coordinated metal
atoms, the four equatorial N atoms are from four distinct
IIMB ligands while the two axial positions are occupied by
two O atoms in 1, 3, 5 and 6 or by two chloride anions in 2,
T h i s j o u r n a l i s Q T h e R o y a l S o c i e t y o f C h e m i s t r y a n d t h e
C e n t r e N a t i o n a l d e l a R e c h e r c h e S c i e n t i f i q u e 2 0 0 4
1016
N e w . J . C h e m . , 2 0 0 4 , 2 8 , 1 0 1 0 – 1 0 1 8

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P. J. Stang, Chem. Rev., 2000, 100, 853; ( f ) G. F. Swiegers and
T. J. Malefetse, Chem. Rev., 2000, 100, 3483; (g) T. Okubo, S.
Kitagawa, M. Kondo, H. Matsuzaka and T. Ishii, Angew. Chem.,
Int. Ed., 1999, 38, 931; (h) I. Boldog, E. B. Rusanov, A. N.
Chernega, J. Sieler and K. V. Domasevitch, J. Chem. Soc., Dalton
Trans., 2001, 893; (i) E. Q. Gao, Z. M. Wang, C. S. Liao and
C. H. Yan, New J. Chem., 2002, 26, 1096.
Recent examples of MOFs: (a) O. M. Yaghi, M. O’Keeffe, N. W.
Ockwig, H. K. Chae, M. Eddaoudi and J. Kim, Nature (London),
2003, 423, 705; (b) M. Eddaoudi, D. B. Moler, H. L. Li, B. L.
Chen, T. M. Reineke, M. O’Keeffe and O. M. Yaghi, Acc. Chem.
Res., 2001, 34, 319; (c) H. Li, M. Eddaoudi, M. O’Keeffe and
O. M. Yaghi, Nature (London), 1999, 402, 276; (d ) M. Eddaoudi,
J. Kim, D. Vodak, A. Sudik, J. Wachter, M. O’Keeffe and O. M.
Yaghi, Proc. Natl. Acad. Sci. U. S. A., 2002, 99, 4900; (e) B. Chen,
M. Eddaoudi, S. T. Hyde, M. O’Keeffe and O. M. Yaghi, Science,
2001, 291, 1021; ( f ) M. Eddaoudi, J. Kim, N. Rosi, D. Vodak, J.
Wachter, M. O’Keefe and O. M. Yaghi, Science, 2002, 295, 469;
(g) M. Eddaoudi, H. Li and O. M. Yaghi, J. Am. Chem. Soc.,
2000, 122, 1391.
except for complex 4, which is different due to the coordination
of acetate anions in bidentate mode [Fig. 5(a)]. In complex 7
with four-coordinated Zn(II) atoms, all the coordinated N
atoms are from IIMB ligands with no coordination of O atoms
from water or nitrate anion. The structures of 1, 2, 5 and 7 are
schematically shown in Scheme 2, in which the axial ligands in
1, 2 and 5 were omitted for clarity. It is clear that there are
M2(IIMB)2 loops in these complexes. In 1, 2 and 5, the loops
are joined together by six-coordinated metal atoms to give
1D hinged chains, which are further interlaced with each other
to form a 2D polycatenane for 1 and 5. While in the case of 7,
the loops are connected by IIMB ligands to produce a 1D
chain and, as a result, each Zn(II) atom is coordinated by four
IIMB ligands, two of which form a loop and two of which link
the loops. The reactions of IIMB with other metal salts having
square planar or triangular coordination geometries are now
undergoing in our lab.
2
It is worthy to note that reactions of Zn(NO3)2ꢀ6H2O with
IIMB and bix generated complexes with 1D tubular chain
(7) and 2D polyrotaxane structures,5b respectively. The zinc(II)
atoms in both complexes have the same tetrahedral coordina-
tion geometry with a N4 donor set and the difference between
bix and IIMB is just that there is one more methylene group in
bix. The results imply that subtle changes in the ligand may
have a great impact on the structure of MOFs. In the case of
the Mn(II) complexes 5, 6 and Mn(bix)3(NO2)2ꢀ4H2O,5c all
the Mn(II) atoms in these three complexes are six-coordinated
with N4O2 binding set. However, they have different struc-
tures, which are attributed to the different structures of the
IIMB and bix ligands as well as different anions. Reaction of
manganese(II) perchlorate with bimb gave an infinite 1D chain
complex, in which the Mn(II) atom has a N6 , rather than
N4O2 , donor set and a snake-like 1D chain was obtained by
reaction of bimb with zinc(II) acetate, which is different from
the 1D chain of 4.6a,6b The differences between the complexes
of bimb and IIMB are considered to be caused by the greater
flexibility and larger biphenyl spacer group of bimb compared
with IIMB.
3
(a) S. R. Batten and R. Robson, Angew. Chem., Int. Ed. Engl.,
1998, 37, 1460; (b) M. Fujita, Acc. Chem. Res., 1999, 32, 53; (c)
D. B. Amabilino and J. F. Stoddart, Chem. Rev., 1995, 95,
2725; (d ) D. B. Amabilino, P. R. Ashton, S. E. Boyd, J. Y. Lee,
S. Menzer, J. F. Stoddart and D. J. Williams, Angew. Chem.,
Int. Ed. Engl., 1997, 36, 2070; (e) C. P. McArdle, S. Van, M. C.
Jennings and R. J. Puddephatt, J. Am. Chem. Soc., 2002, 124,
3959; ( f ) C. P. McArdle, M. J. Irwin, M. C. Jennings, J. J. Vittal
and R. J. Puddephatt, Chem.-Eur. J., 2002, 8, 723; (g) K. M. Park,
S. Y. Kim, J. Heo, D. Whang, S. Sakamoto, K. Yamaguchi and
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D. Whang, E. Lee, J. Heo and K. Kim, Chem.-Eur. J., 2002, 8,
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Mullins, B. Muller, K. Mullen and Y. Geerts, Macromolecules,
¨
¨
1999, 32, 1737.
4
(a) R. Robson, B. F. Abrahams, S. R. Batten, R. W. Gable, B. F.
Hoskins, J. Liu, Supramolecular Architecture, ACS Publications,
Washington, DC, 1992, p. 256; (b) H. Gudbjartson, K. Biradha,
K. M. Poirier and M. J. Zaworotko, J. Am. Chem. Soc., 1999,
121, 2599; (c) M. L. Tong, B. H. Ye, X. M. Chen and S. W.
Ng, Inorg. Chem., 1998, 37, 2645; (d ) W. Y. Sun, B. L. Fei,
T.-A. Okamura, W. X. Tang and N. Ueyama, Eur. J. Inorg.
Chem., 2001, 1855; (e) L. Carlucci, G. Ciani, D. W. Gudenberg,
D. M. Proserpio and A. Sironi, Chem. Commun., 1997, 631.
(a) B. F. Hoskins, R. Robson and D. A. Slizys, J. Am. Chem. Soc.,
1997, 119, 2952; (b) B. F. Hoskins, R. Robson and D. A. Slizys,
Angew. Chem., Int. Ed. Engl., 1997, 36, 2336; (c) H. Y. Shen,
D. Z. Liao, Z. H. Jiang, S. P. Yan, G. L. Wang, X. K. Yao
and H. G. Wang, Acta Chem. Scand., 1999, 53, 387; (d )
L. Carlucci, G. Ciani and D. M. Proserpio, Chem. Commun.,
2004, 380.
(a) B. L. Fei, W. Y. Sun, Y. A. Zhang, K. B. Yu and W. X. Tang,
J. Chem. Soc., Dalton Trans., 2000, 2345; (b) H. F. Zhu, W. Zhao,
T.-A. Okamura, B. L. Fei, W. Y. Sun and N. Ueyama, New J.
Chem., 2002, 26, 1277; (c) H. K. Liu, W. Y. Sun, D. J. Ma,
K. B. Yu and W. X. Tang, Chem. Commun., 2002, 591; (d ) J.
Fan, H. F. Zhu, T.-a. Okamura, W.-Y. Sun, W.-X. Tang and
N. Ueyama, Inorg. Chem., 2003, 42, 158.
5
6
7
Conclusions
We have assembled the first examples of 2D polycatenanes
formed by the interlocking of double-stranded 1D chains. A
series of relevant coordination compounds was successfully
synthesized and the structures were examined. X-Ray analyses
show that reactions of IIMB with seven kinds of metal salts
afford molecular, 1D and 2D coordination compounds. The
results indicate that the nature of counter anions, such as their
coordination ability, coordination mode and size, and the geo-
metric needs of the metal atoms can determine the topologies
and properties of coordination compounds. Furthermore, the
anions participating in coordination can greatly influence the
structure of the compounds.
For examples: (a) H.-K. Liu, W.-Y. Sun, W.-X. Tang, T.
Yamamoto and N. Ueyama, Inorg. Chem., 1999, 38, 6313; (b)
W.-Y. Sun, J. Xie, T.-a. Okamura, C.-K. Huang and N. Ueyama,
Chem. Commun., 2000, 1429; (c) W.-Y. Sun, J. Fan, T.-a.
Okamura, J. Xie, K.-B. Yu and N. Ueyama, Chem.-Eur. J.,
2001, 7, 2557; (d ) J. Fan, W.-Y. Sun, T.-a. Okamura, J. Xie,
W.-X. Tang and N. Ueyama, New J. Chem., 2002, 26, 199; (e)
J. Fan, B. Sui, T.-a. Okamura, W.-Y. Sun, W.-X. Tang and
N. Ueyama, J. Chem. Soc., Dalton Trans., 2002, 3868.
Acknowledgements
The authors are grateful to the National Natural Science
Foundation of China (Grant No. 20231020) for financial
support of this work.
8
9
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W. X. Tang, Inorg. Chim. Acta, 1999, 295, 129.
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1994, 27, 435.
10 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman, R. de
Gelder, R. Israel and Jan M. M. Smits, The DIRDIF-94 program
system, Crystallography Laboratory, University of Nijmegen,
The Netherlands, 1994.
11 (a) W. Y. Sun, J. Fan, T.-a. Okamura, W. X. Tang and N.
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Fei, T.-a. Okamura, Y. A. Zhang, T. Ye, W. X. Tang and N.
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