Helicity-induced two-layered Cd(II) coordination polymers built with different kinked dicarboxylates and an organodiimidazole

Article abstract of DOI:10.1016/j.poly.2009.09.005

A new ligand bis-(4-imidazol-1-yl-phenyl)-diazene (azim), incorporating an azo moiety at the center and two imidazole groups at the terminals has been designed and synthesized. Under solvothermal conditions, this ligand reacts with Cd(NO₃)

Full text of DOI:10.1016/j.poly.2009.09.005

Polyhedron 28 (2009) 3923–3928
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Helicity-induced two-layered Cd(II) coordination polymers built
with different kinked dicarboxylates and an organodiimidazole
*
Subhadip Neogi, Manish K. Sharma, Madhab C. Das, Parimal K. Bharadwaj
Department of Chemistry, Indian Institute of Technology, Kanpur 208016, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 May 2009
Accepted 4 September 2009
Available online 9 September 2009
A new ligand bis-(4-imidazol-1-yl-phenyl)-diazene (azim), incorporating an azo moiety at the center and
two imidazole groups at the terminals has been designed and synthesized. Under solvothermal condi-
tions, this ligand reacts with Cd(NO3)2ꢀ6H2O and different angular aromatic dicarboxylates to form lay-
ered coordination polymers: [Cd(azim)(bcp)]n (1) and {[Cd(azim)(oba)](H2O)}n (2) [bcpH2 = 1,3-bis-(40-
carboxy phenoxy)benzene; oba = 4,40-oxybis(benzoate)]. Both 1 and 2 have been characterized by sin-
gle-crystal X-ray diffraction technique, elemental analysis, PXRD and IR spectroscopy. The structure of
each polymer looks like 2D grid where two layers are interpenetrated in a ‘‘cloth-like” topology. Both
the structures contain single- and double-stranded helical coils where the pitches as well as the width
are controlled by the carboxylate co-ligands. The hydrogen-bonding interactions between adjacent layers
extend these structures to overall 3D supramolecular architectures.
Keywords:
Helical structure
Coordination polymer
Angular carboxylate ligand
Organodiimidazole ligand
Interpenetrated framework
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
types of entanglements of individual motifs, particularly in the
field of crystal engineering of coordination polymers, or metal–
Coordination polymers from relatively simple sub-units have
attracted considerable interest because of their potential applica-
tions such as materials for selective gas adsorption, catalysis,
desirable optical properties [1–14] and so on. Apart from different
coordination tendencies of metal ion, the modular construction of
coordination polymers can be systematically tuned by elaborate
selection of ligand bite angle, its length and relative orientation
of the donor atoms, which ultimately alters their pore size and
shape.
Aromatic polycarboxylates are by far the most extensively
used ligands to generate MOFs having different supramolecular
architectures. Aromatic group imparts rigidity to the ligand that
is necessary to prevent collapse of the structure formed. Besides,
coordination polymers built with carboxylates can be neutral that
can eliminate problems associated with presence of the counter
anions. A large variety of interpenetrating networks and entan-
gled extended arrays are currently shaped within the areas of
inorganic and coordination chemistry, especially due to the inten-
sive search for new functional materials. The analysis of these
species can be a difficult and time-consuming work because of
their ever growing number and for their increasing structural
complexity, as evidenced by the continuous finding of many
organic frameworks (MOFs) [1–14]. ‘Interpenetrating networks’
[15–17] are nowadays the more numerous entangled arrays, that
need for a classification of the topology of the individual nets
[18–26].
Interpenetrated or entangled networks [18–26] represent an
opportunity for achieving a 1D to 2D expansion through inter-
weaving 1D chain. In this report, we show that helicity in entan-
gled MOFs can be induced through proper selection of ligands.
These helical chains interweave to form 2D coordination poly-
meric networks. Helical coordination polymers themselves have
received great attention for potential applications in biomimetic
chemistry as well as understanding of molecular self-assembly
processes [27–29]. So far, much effort has been directed on the
exploitation of rod-like ligands [30–33]. However, there has been
comparatively little effort concentrated toward angular ligands
with an angle other than 180° [34–37]. In principle, the ex-
tended structures based on helical chains can be produced
through the twisted binding sites of bridging ligands, which
can also connect neighboring helices via cross-linking. In this re-
spect, our research has been focused towards designing of new
ligands and investigating the rational control of their self-assem-
bly with metal ions [38–42]. Herein, we describe the synthesis of
two different entangled 2D layer structures from a long ligand
incorporating imidazole at the terminals (Scheme 1) and one
of two different bent aromatic dicarboxylates under solvother-
mal condition.
* Corresponding author. Tel.: +91 512 2597304; fax: +91 512 2597436.
E-mail address: pkb@iitk.ac.in (P.K. Bharadwaj).
0277-5387/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2009.09.005

3924
S. Neogi et al. / Polyhedron 28 (2009) 3923–3928
N
F
HN
N
N
1Aq. NaOH
N
N
N
2. Zn-powder
DMF, K2CO3,
N
N
N
Reflux for 8 hrs
NO2
NO2
azim
Scheme 1. Synthetic scheme for ligand azim.
2.1.2. Synthesis of 1,3- bis-(40-carboxyphenoxy)benzene (bcpH2)
This ligand was prepared by following a method (Scheme 2) as
described below.
2. Experimental
2.1. Chemicals and reagents
All the metal salts and H2oba were procured from Aldrich and
used as received. All other chemicals were acquired from S.D. Fine
Chemicals, India. Solvents were purified prior to use. All solvother-
mal syntheses were performed in Teflon-lined stainless steel auto-
claves under autogenous pressure.
2.1.2.1. Synthesis of 1,3-bis-(40-cyanophenoxy)benzene (cpob). A mix-
ture of resorcinol (1.1 g, 10 mmol) and anhydrous K2CO3 (7 g) in
DMF (50 ml) was heated for 30 min under argon atmosphere. 4-
fluorobenzonitrile (2.4 g, 20 mmol) was added drop wise to this
and the reaction mixture was refluxed for 48 h. The resulting
brown solution was poured in 250 ml ice-cold water and kept
over-night. The light yellow crystalline compound was filtered,
washed several times with water and finally air-dried. Melting
point: 96 °C. FAB-MS, m/z (%): 335 (100) [cpob+]. 1H NMR
(400 MHz, DMSO-d6), TMS, 25 °C): d (ppm) 6.76 (t, 1H, Ph-H),
6.89 (m, 2H, Ph-H), 7.04 (m, 4H, Ph-H), 7.41 (t, 1H, Ph-H), 7.61
2.1.1. Synthesis of bis-(4-imidazol-1-yl-phenyl)-diazene (azim)
This ligand was prepared by following a method (Scheme 1) as
described below.
2.1.1.1. Synthesis of 1-(4-nitro-phenyl)-1H imidazole. A mixture of
imidazole (2.1 g; 31.18 mmol) and anhydrous K2CO3 (42.52 mmol)
in DMF (30 mL) was heated for 30 min with vigorous stirring. 4-
fluoronitrobenzene (4 g, 28.34 mmol) was added to this over a per-
iod of 15 min and the reaction mixture was refluxed for 8 h. The
reaction mixture was poured to ice-cold water and allowed to
stand overnight. The resulting yellow precipitate was filtered off,
washed with water and dried in air to get the pure compound in
85% yield. 1H NMR (CDCl3, 400 MHz): d 7.21(s, 1H, Har), 7.32 (s,
1H, Har), 7.52(d, J = 9.28 Hz, 2H, Har), 7.94(s, 1H, Har), 8.31(d,
J = 9.28 Hz, 2H, Har). Anal. Calc. for C18H22N4: C, 73.44; H, 7.53; N,
19.03. Found: C, 73.59; H, 7.41; N, 19.12%.
(m, 4H, Ph-H). IR (KBr, cmꢁ1, selected peak): 2210 (
m(CN)). Anal.
Calc. for C20H12N2O2: C, 76.91; H, 3.87; N, 8.97. Found: C, 76.83;
H, 3.84, N, 8.89%.
2.1.2.2.
Synthesis
of
1,3-
bis-(40-carboxyphenoxy)benzene
(bcpH2). Aqueous ethanolic solution of ligand cpob (3.12 g;
0.01 mol) was allowed to reflux with 6 N NaOH solution (50 mL)
until the smell of ammonia gas ceases. The reaction mixture was
cooled to room temperature and acidified with HCl (6 N) while
the temperature was maintained below 5 °C throughout. Colorless
crystalline product in 60% yield was isolated by filtration, washed
several times with water and dried in vacuum. Melting point:
210 °C. FAB-MS, m/z (%): 350 (100) [bcpH2þ]. 1H NMR (400 MHz,
DMSO-d6), TMS, 25 °C): d (ppm) 6.62 (t, 1H, Ph-H), 6.77 (m, 2H,
Ph-H), 7.19 (m, 4H, Ph-H), 7.22 (t, 1H, Ph-H), 7.96 (m, 4H, Ph-H).
2.1.1.2. Synthesis of bis-(4-imidazol-1-yl-phenyl)-diazene (azim). To
a suspension of 1-(4-nitro-phenyl)-1H imidazole (5 g, 26.45 mmol)
in 2-propanol, aqueous NaOH (12 g in 30 mL H2O) and Zn powder
(30 g) were added and the mixture was heated to reflux for 6 h.
After cooling the reaction mixture to room temperature, the insol-
uble materials were separated by filtration and the filtrate was re-
moved under reduced pressure to get orange oil and extracted with
chloroform. The organic layer was washed several times with
water and finally evaporated under reduced pressure to give a
bright orange solid in 72% yield.
IR (KBr, cmꢁ1, selected peaks): 3480 (
m(OH)), 1683 (m(CO)). Anal.
Calc. for C20H14O6: C, 68.57; H, 4.02. Found: C, 68.80; H, 3.98%.
2.1.3. Synthesis of [Cd(azim)(bcp)]n (1)
A
mixture of azim (1 mmol), bcpH2 (1 mmol) and
Cd(NO3)2ꢀ6H2O (2 mmol) was dissolved in 4 ml DMF. The mixture
was placed in a Teflon-lined stainless steel autoclave. The vessel
was sealed and heated to 110 °C for 72 h and then cooled to room
temperature at the rate of 1 °C per minute. Orange rectangular
crystals were collected in ꢂ50% yield from the reaction mixture.
Anal. Calc. for C38H26CdN6O6: C, 58.87; H, 3.38; N, 10.85. Found:
C, 58.58; H, 3.25; N, 11.03%.
1H NMR (CDCl3, 400 MHz): d 7.00 (s, 1H, Har), 7.31 (s, 1H, Har),
7.13(d, J = 8.56 Hz, 2H, Har), 7.56 (s, 1H, Har), 7.48 (d, J = 8.8 Hz,
2H, Har); IR (cmꢁ1
, KBr disk): 3103(m), 1599(s), 1515(m),
1305(w); MS(ESI); m/z (rel. intensity): 315(100); calculated
314.65. Anal. Calc. for C18H14N6: C, 42.83; H, 5.72; N, 1.85. Found:
C, 43.93; H, 5.09; N, 1.22%.
NC
F
O
O
O
O
1. 6(N) NaOH
2. 6(N) HCl
DMF, K2CO3,
HO
OH
Reflux for 48 hrs
CN
HO2C
NC
CO2H
cpob
bcpH2
Scheme 2. Synthetic scheme for ligand bcpH2.

S. Neogi et al. / Polyhedron 28 (2009) 3923–3928
3925
Table 1
resulting slurry was stirred at room temperature for 3 h. After
the orange precipitate had been filtered off, the solution was
heated to 110 °C in a Teflon-lined stainless steel autoclave for
60 h and then cooled to room temperature at the rate of 1 °C per
minute. Block-shaped orange crystals were collected in ꢂ60% yield
from the reaction mixture. Anal. Calc. for C32H24N6O6Cd: C, 54.83;
H, 3.45; N, 11.99. Found: C, 54.88; H, 3.42; N, 11.97%.
Crystal and structure refinement data for 1 and 2.
Empirical formula
Formula weight
Temperature (K)
C38H26CdN6O6 (1)
775.05
100(1)
C32H24CdN6O6 (2)
700.97
100(1)
Radiation, wavelength (Å) Mo K
a
, 0.71073
Mo Ka, 0.71073
Crystal system
Space group
a (Å)
b (Å)
c (Å)
monoclinic
P21/c
6.876(5)
26.827(5)
17.715(5)
90.00
94.337(5)
90.00
3258(3)
4
triclinic
ꢀ
P1
11.587(4)
11.855(4)
12.382(5)
72.234(6)
69.414(5)
70.131(5)
1463.7(9)
2
1.590
0.803
708
7376
2.2. Physical measurements
a
(°)
b (°)
Spectroscopic data were collected as follows: IR (KBr disk, 400–
4000 cmꢁ1) Perkin–Elmer Model 1320; X-ray powder pattern (Cu
c
(°)
U (Å3)
Ka radiation at a scan rate of 3°/min, 293 K) with either Siefert
Z
qcalc (Mg/m3)
1.580
0.730
1568
20272
ISODEBYEFLEX-2002 or Phillips PW 100 diffractometers; thermo-
gravimetric analysis (heating rate of 5 °C/min) Perkin–Elmer Pyris
6. Microanalyses for the compounds were obtained from the Cen-
tral Drug Research Institute, Lucknow, India. FAB-MS (positive ion)
data were recorded on a JEOL SX 102 /DA-6000 mass spectrometer
using argon as the FAB gas at 6 kV and 10 mA with an accelerating
voltage of 10 kV at 298 K. 1H NMR spectra recorded on a JEOL JNM-
LA400 FT (400 MHz) instrument in DMSO-d6 with Me4Si as internal
standard. Melting points were recorded with an electrical melting
point apparatus by PERFIT, India.
l
(mmꢁ1
)
F(0 0 0)
Reflections collected
Independent reflections
Refinement method
5778
4803
Full-matrix least-
squares on F2
1.066
R1 = 0.0645
wR2 = 0.1120
R1 = 0.1085
wR2 = 0.1928
Full-matrix least-
squares on F2
1.122
R1 = 0.0712
wR2 = 0.1745
R1 = 0.1039
wR2 = 0.2298
Goodness-of-fit (GOF)
Final R indices [I > 2
r(I)]
R indices (all data)
2.3. X-ray crystallography
Table 2
Selected bond distances (Å) and bond angles (°) in 1 and 2.
Single-crystal X-ray data on 1 and 2 were collected at 100 K on a
Bruker SMART APEX CCD diffractometer using graphite-monochro-
mated Mo Ka radiation (k = 0.71069 Å). The linear absorption coef-
1
Cd1–N6
Cd1–O1
2.229(6)
2.339(6)
Cd1–N1
Cd1–O2
2.237(6)
2.398(5)
Cd1–O5
Cd1–O6
2.254(5)
2.407(6)
ficients, scattering factors for the atoms, and the anomalous
dispersion corrections were taken from International Tables for
X-ray Crystallography. The data integration and reduction were
processed with SAINT [43] software. An empirical absorption correc-
tion was applied to the collected reflections with SADABS [44] using
XPREP [45]. The structure was solved by the direct method using
SHELXTL [46] and was refined on F2 by full-matrix least-squares tech-
nique using the SHELXL-97 [47] program package. The non-hydrogen
atoms were refined anisotropically unless otherwise mentioned.
The hydrogens were treated as riding atoms using SHELXL default
parameters. Each of the C atoms of (C18–C23) of one benzene ring
in the ‘azim’ ligand of complex 2 is disordered over two positions
with occupancy of 0.5. Similarly N5, N6, O5 are also disordered
over two positions. Atom Ow1 is disordered over three positions.
All of these disordered atoms were refined isotropically. Details
of the data collections, solutions and refinements for 1 and 2 are
N6–Cd1–N1 101.8(2)
N6–Cd1–O1 103.1(2)
N6–Cd1–O2 91.2(2)
O1–Cd1–O2 54.55(19) N6–Cd1–O6 156.53(18) N1–Cd1–O6 85.4(2)
O5–Cd1–O6 56.18(17) O1–Cd1–O6 87.5(3)
N6–Cd1–O5 101.22(19) N1–Cd1–O5 116.5(2)
N1–Cd1–O1 132.3(2)
N1–Cd1–O2 85.0(2)
O5–Cd1–O1 97.6(2)
O5–Cd1–O2 151.7(2)
O2–Cd1–O6 111.8(2)
2
Cd1–O2
Cd1–N1
2.235(5)
2.251(7)
Cd1–O4
Cd1–O5
2.239(6)
2.512(7)
Cd1–N4
Cd1–O3
2.244(6)
2.541(6)
O2–Cd1–O4 140.3(2)
O2–Cd1–N1 89.0(2)
O2–Cd1–O5 98.8(2)
N1–Cd1–O5 84.4(3)
N4–Cd1–O3 90.2(2)
O2–Cd1–N4 114.8(2)
O4–Cd1–N1 113.8(2)
O4–Cd1–O5 54.8(2)
O2–Cd1–O3 54.37(18)
N1–Cd1–O3 143.2(2)
O4–Cd1–N4 91.8(2)
N4–Cd1–N1 103.8(2)
N4–Cd1–O5 145.3(2)
O4–Cd1–O3 99.3(2)
O5–Cd1–O3 103.3(3)
2.1.4. Synthesis of {[Cd(azim)(oba)](H2O)}n (2)
mixture of azim (1 mmol), obaH2 (1 mmol) and
Cd(NO3)2ꢀ6H2O (2 mmol) was dissolved in DMF (4 mL) and the
A
Fig. 1. Coordination environment around Cd(II) centers in (a) 1 and (b) 2. All the H-atoms have been omitted for clarity.

3926
S. Neogi et al. / Polyhedron 28 (2009) 3923–3928
Fig. 2. (a) Perspective view of (a) the right-handed helical chains and (b) unprecedented 2D grid structure in 1. Two different layers are shown in two different shades of
grayscale.
Fig. 3. (a) Unprecedented 4fold network and (b) double helical chains built with [Cd(bcp)(azim)] units along the crystallographic a axis in 1.
given in Table 1 while their selective bond distances and bond an-
gles are summarized in Table 2.
bcp2ꢁ ligands as edges. As a result, large almost square-shaped cav-
ity (19.11 ꢃ 19.31 Å2) is produced. An interesting feature in 1 is the
independent interpenetration of two exactly similar square grids
within each other like a ‘‘one over/one under” clothlike topology
3. Results and discussion
Single-crystal X-ray diffraction study reveals that asymmetric
unit of 1 consists of one Cd(II) ion, one azim ligand and one bcp2ꢁ
ligand. Each metal is bonded to two imidazole nitrogen atoms from
two different azim ligands and four oxygen atoms from two differ-
ent cis-oriented bcp2ꢁ ligands (Fig. 1a). This binding mode forms a
distorted octahedral coordination geometry around each metal ion
with average Cd(II)ꢀ ꢀ ꢀN(imidazole) distance of 2.23 Å and average
Cd(II)ꢀ ꢀ ꢀO (carboxylate) distance of 2.344 Å which are slightly long-
er compared to reported [48] octahedral Cd(II) complexes.
Each bcp2ꢁ ligand in 1 adopts a bent structure with average C–
O–C bond angle of 118.95° at the substituted ring and each carbox-
ylate donates both its O atoms to a single Cd(II) ion. The resultant
neutral [Cd(bcp)]n units extend as an infinite right-handed –C–O–
Cd– helical chain along the crystallographic b axis with minimum
Cd(II)ꢀ ꢀ ꢀCd(II) separation of 19.11 Å. In the same direction, trans-
azim ligands join Cd(II) ions to form cationic {[Cd(azim)]2+
} units
n
as an infinite –C–N–Cd– right-handed helical chain where mini-
mum separation between metal ions is 19.31 Å (Fig. 2a). Top view
of [Cd(bcp)]n helix is oval-shaped while that of {[Cd(azim)]2+}n he-
lix is rectangular due to different steric requirements of the two li-
gands [49].
Both [Cd(bcp)]n and {[Cd(azim)]2+}n helical chains are intercon-
nected to each other through a common Cd(II) center and gener-
ates an unprecedented 2D grid structure (Fig. 2b). Each grid is
composed of four Cd(II) ions as corners and two azim and two
Fig. 4. Space filling view of 2D grid structure in 2.

S. Neogi et al. / Polyhedron 28 (2009) 3923–3928
3927
Fig. 5. (a) A perspective view of the interpenetrated structure and (b) the double-stranded helical structure along crystallographic a axis in 2. For clarity, all the H-atoms have
been omitted.
(Fig. 3a) [50–52], which can be designated as 4-fold ‘‘sql” stacking
[20] as ABAB along [0 0 1] direction. This interpenetration leads to
double helical chains built with [Cd(bcp)(azim)] units along the
crystallographic a axis (Fig. 3b). A deep insight into the structure
ecule is lost between 80 and 100 °C along with a steady weight loss
of ꢂ10% up to 350 °C. Complete decomposition is achieved soon
after. In comparison, 1 loses weight steadily beginning at ꢂ80 °C
and about 25% weight loss occurs up to 330 °C before complete
decomposition.
of 1 reveals that the double helix is stabilized by C–Hꢀ ꢀ ꢀ
p stacking
interactions involving aromatic H atoms of bcp2ꢁ ligand with near-
by benzene ring of azim ligand [49]. These 2D interwoven net-
works are stacked in a parallel manner along the crystallographic
c axis into a 3D network such that metal ions are not on top of each
other.
4. Conclusion
In conclusion, we have successfully prepared two 2D coordina-
tion polymers of different morphology using a long dimidazole li-
gand and different angular dicarboxylates with a molecular angle
less than 180°. This work demonstrates that extended structural
motifs can be constructed through neutral or cationic 1D helical
chains and assembly of mixed bridging organic ligands with metal
ions can afford a broader way to construct helical architecture than
using single bridging ligand. This is the first report of mixed-ligand
polymer comprising helical chains from previously unknown azim
and bcpH2 ligands. We believe that judicious variance of the con-
formational flexibility and donor disposition of long rigid or angu-
lar ligands is likely to exploit in the context of rational design of
coordination polymers.
Crystals of 2 are also obtained in high yield following solvother-
mal reaction of azim ligand with Cd(NO3)2ꢀ6H2O and V-shaped
obaH2 ligand. The asymmetric unit consists of one ligand each, a
Cd(II) ion and one water molecule. Here, the Cd(II) ion is distorted
octahedral with equatorial coordination from four O atoms from
two different oba2ꢁ ligands and axial coordination from two differ-
ent trans orientedazim ligands(Fig. 1b). Unlike in case of 1, here each
similar ligand is bonded in a trans-fashion in 2 and this difference in
bonding leads to different overall 2D structure (described later).
Similar to 1, both the average Cd(II)–O (2.381 Å) and Cd(II)–N
distances (2.247 Å) in this complex are slightly longer compared
[50–52] to published octahedral Cd(II) complexes. The oba2ꢁ li-
gand maintains its V-shape with the C–O–C bond angle showing
115.8°. Here, each Cd(II) ion serves as 4-connected node and linked
by oba2ꢁ and azim ligands to form rectangular grid corrugated
sheets (Fig. 4) of dimension (14.35 ꢃ 19.61 Å2). The average diago-
nal distance of each rectangle is 24.30 Å.
It is noteworthy that the metal ions in 2 are not coplanar but are
present in stair-like conformation. These stair-like layers are inter-
penetrated to each other, resulting in the formation of a doubly
interpenetrated 2D layered network (Fig. 5a). This type of inter-
penetration leads to the formation of double-stranded helical
structure along the crystallographic a axis (Fig. 5b). The 2D inter-
penetrated layers are stacked as ABAB fashion along [0 1 0] direc-
tion attaining a 2-fold ‘‘sql” net structure [20].
Acknowledgements
Financial support from the Department of Science and Technol-
ogy, New Delhi, India is gratefully acknowledged. S.N., M.K.S. and
M.C.D. thank the CSIR, India for SRF positions. We thank Prof.
J.A.R. Navarro for collecting the XRPD patterns and Prof. B.R. Srini-
vasan for TGA data.
Appendix A. Supplementary data
CCDC 686278 and 686279 contains the supplementary crystal-
lographic data for 1 and 2. These data can be obtained free of
charge via http://www.ccdc.cam.ac.uk/conts/retrieving.html, or
from the Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: de-
posit@ccdc.cam.ac.uk. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.poly.2009.09.005.
The interlayer aggregation is supplemented by relatively strong
C–Hꢀ ꢀ ꢀ
p interaction (ranging from 4.326–4.798 Å) between aro-
matic H atoms of azim benzene rings and benzene rings of oba2ꢁ
of the adjacent layer. These layers are also interdigitated via
p p interactions (3.618 Å) viewed down [1 0 1] direction where
ꢀ ꢀ ꢀ
the imidazole and benzene rings are parallels to each other. Neigh-
boring layers are related by crystallographic inversion centers with
average interlayer M–M contact distance 12.14 Å.
References
In spite of interpenetration in 2 there is still some void space
where one lattice water molecule is accommodated. The FTIR spec-
trum of as synthesized 2 shows a broad band centered on
3500 cmꢁ1 due to the O–H stretching frequency of the water mol-
ecule. Thermal analysis of 2 shows [49] that the lattice water mol-
[1] O. Sato, T. Iyoda, A. Fujishima, K. Hashimoto, Science 271 (1996) 49.
[2] S.S.-Y. Chui, S.M.-F. Lo, J.P.H. Charmant, A.G. Orpen, I.D. Williams, Science 283
(1999) 1148.
[3] O.R. Evans, R. Xiong, R. Wang, G.K. Wong, W. Lin, Angew. Chem., Int. Ed. 38
(1999) 536.
[4] M.C. Das, P.K. Bharadwaj, J. Am. Chem. Soc. 131 (2009) 10942.

3928
S. Neogi et al. / Polyhedron 28 (2009) 3923–3928
[5] O.M. Yaghi, H. Li, C. Davis, D. Richardson, T.L. Groy, Acc. Chem. Res. 31 (1998)
575.
[29] C. Piguet, G. Bernardinelli, G. Hopfgartner, Chem. Rev. 97 (1997) 2005.
[30] N.G. Pschirer, D.M. Ciurtin, M.D. Smith, U.H.F. Bunz, H.-C. zur Loye, Angew.
Chem., Int. Ed. 41 (2002) 583.
[31] M.B. Zaman, M.D. Smith, H.-C. zur Loye, Chem. Mater. 13 (2001) 3534.
[32] D. Hagrman, R.P. Hammond, R. Haushalter, A. Zubieta, J. Chem. Mater. 10
(1998) 2091.
[33] O.M. Yaghi, H.L. Li, T.L. Groy, Inorg. Chem. 36 (1997) 4292.
[34] A.N. Khlobystov, M.T. Brett, A.J. Blake, N.R. Champness, P.M.W. Gill, D.P. O’Neill,
S.J. Teat, C. Wilson, M.J. Schröder, J. Am. Chem. Soc. 125 (2003) 6753.
[35] M.B. Zaman, M.D. Smith, D.M. Ciurtin, H.-C. zur Loye, Inorg. Chem. 41 (2002)
4895.
[36] Y. Cui, H.L. Ngo, W. Lin, Inorg. Chem. 41 (2002) 1033.
[37] J. Lu, A. Mondal, B. Moulton, M.J. Zaworotko, Angew. Chem., Int. Ed. 40 (2001)
2113.
[6] P.J. Hagrman, D. Hagrman, J. Zubieta, Angew. Chem., Int. Ed. 38 (1999) 2638.
[7] S. Noro, S. Kitagawa, M. Kondo, K. Seki, Angew. Chem., Int. Ed. 39 (2000) 2081.
[8] M.-L. Tong, X.-M. Chen, B.-H. Ye, L.-N. Ji, Angew. Chem., Int. Ed. 38 (1999) 2237.
[9] M.-L. Tong, S.-L. Zheng, X.-M. Chen, Chem. Commun. (1999) 561.
[10] M.-L. Tong, H.-J. Chen, X.-M. Chen, Inorg. Chem. 39 (2000) 2235.
[11] M.-L. Tong, S.-L. Zheng, X.-M. Chen, Chem. Eur. J. 6 (2000) 3729.
[12] S.-L. Zheng, M.-L. Tong, R.-W. Fu, X.-M. Chen, S.W. Ng, Inorg. Chem. 40 (2001)
3562.
[13] L. Carlucci, G. Ciani, D.M. Proserpio, A. Sironi, J. Chem. Soc., Chem. Commun.
(1994) 2755.
[14] N.W. Ockwig, F.O. Delgado, M.O. Keeffe, O.M. Yaghi, Acc. Chem. Res. 38 (2005)
176.
[15] S.R. Batten, R. Robson, Angew. Chem., Int. Ed. 37 (1998) 1460.
[16] 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.
[17] L. Carlucci, G. Ciani, D.M. Proserpio, Coord. Chem. Rev. 246 (2003) 247.
[18] P. Metrangolo, F. Meyer, T. Pilati, D.M. Proserpio, G. Resnati, Chem. Eur. J. 13
(2007) 5765.
[38] S. Neogi, P.K. Bharadwaj, Cryst. Growth Des. 6 (2006) 433.
[39] S. Neogi, J.A.R. Navarro, P.K. Bharadwaj, Cryst. Growth Des. 8 (2008) 1554.
[40] S. Neogi, M.K. Sharma, P.K. Bharadwaj, J. Mol. Catal. A 299 (2009) 1.
[41] S. Neogi, P.K. Bharadwaj, Inorg. Chem. 44 (2005) 816.
[42] M.C. Das, S.K. Ghosh, E.C. Sañudo, P.K. Bharadwaj, Dalton Trans. (2009)
1644.
[19] V.A. Blatov, L. Carlucci, G. Ciani, D.M. Proserpio, CrystEngComm 6 (2004) 377.
[20] O.D. Friedrichs, M. O’Keeffe, O.M. Yaghi, Acta Crystallogr. A 59 (2003) 22.
[21] I.A. Baburin, V.A. Blatov, L. Carlucci, G. Ciani, D.M. Proserpio, J. Solid State
Chem. 178 (2005) 2452.
[22] M. O’Keeffe, M.A. Peskov, S.J. Ramsden, O.M. Yaghi, Acc. Chem. Res. 41 (2008)
1782.
[43] SAINT+, 6.02 ed., Bruker AXS, Madison, WI, 1999.
[44] G.M. Sheldrick, SADABS, Empirical Absorption Correction Program, University of
Göttingen, Germany, 1997.
[45] XPREP, 5.1 ed. Siemens Industrial Automation Inc., Madison, WI, 1995.
[46] G.M. Sheldrick, SHELXTLTM Reference Manual: Version 5.1, Bruker AXS, Madison,
WI, 1997.
[23] L. Carlucci, G. Ciani, D.M. Proserpio, in: D. Braga, F. Grepioni (Eds.), Making
Crystals by Design. Methods, Techniques and Applications, Wiley, VCH, 2007.
[24] L. Öhrström, K. Larsson, in: Molecule-Based Materials: The Structural Network
Approach, Elsevier, Amsterdam, 2005.
[47] G.M. Sheldrick, SHELXL-97: Program for Crystal Structure Refinement, University
of Göttingen, Göttingen, Germany, 1997.
[48] D.B. Oler, M. O’Keeffe, O.M. Yaghi, J. Am. Chem. Soc. 123 (2001) 8239.
[49] See Supplementary data.
[25] M. O’Keeffe, B.G. Hyde, in: Crystal Structures I. Patterns and Symmetry,
Mineralogical Society of America, Washington, DC, 1996.
[26] A.F. Wells, in: Structural Inorganic Chemistry, 5th ed., Oxford University Press,
Oxford, 1984.
[50] P.M. Van-Calcar, M.M. Olmstead, A.L. Balch, J. Chem. Soc., Chem. Commun.
(1995) 1773.
[51] L. Carlucci, G. Ciani, A. Gramaccioli, D.M. Proserpio, S. Rizzato, CrystEngComm
29 (2000) 1.
[27] M. Munakata, L.P. Wu, T. Kuroda-Sowa, Adv. Inorg. Chem. 46 (1999) 173.
[28] C.R. Woods, M. Benaglia, F. Cozzi, J.S. Siegel, Angew. Chem., Int. Ed. 35 (1996)
1830.
[52] I. Ino, J.C. Zhong, M. Munakata, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga, Y.
Kitamori, Inorg. Chem. 39 (2000) 4273.