Syntheses, crystal structures and luminescent properties of two new 1D d10 coordination polymers constructed from 2,2′-bibenzimidazole and 1,4-benzenedicarboxylate

Article abstract of DOI:10.1016/j.jssc.2005.07.035

Two novel interesting d¹⁰ metal coordination polymers, [Zn(H₂bibzim)(BDC)]_n (1) and [Cd(H₂bibzim)(BDC) ]_n (2) [H₂bibzim=2,2′-bibenzimidazole, BDC=1,4-benzenedicarboxylate] have been synthesized under solvothermal conditions and structurally characterized. Both 1 and 2 are constructed from infinite neutral zigzag-like one-dimensional (1D) chains. The π-π interactions and interchain hydrogen-bonding interactions further extend the 1D arrangement to generate a 3D supramolecular architecture for 1 and 2. Both complexes have high thermal stability and display strong blue fluorescent emissions in the solid state upon photo-excitation at 365 nm at room temperature. They are the first two examples that 2,2′-bibenzimidazole has been introduced into the d¹⁰ coordination polymeric framework.

Full text of DOI:10.1016/j.jssc.2005.07.035

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Journal of Solid State Chemistry 178 (2005) 3336–3341
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Syntheses, crystal structures and luminescent properties of two new 1D
d10 coordination polymers constructed from 2,20-bibenzimidazole and
1,4-benzenedicarboxylate
Ã
Lili Wen, Yizhi Li, Dongbin Dang, Zhengfang Tian, Zhaoping Ni, Qingjin Meng
State Key Laboratory of Coordination Chemistry, Coordination Chemistry Institute, Nanjing University, 210093 Nanjing, PR China
Received 11 May 2005; received in revised form 25 July 2005; accepted 31 July 2005
Available online 27 September 2005
Abstract
Two novel interesting d10 metal coordination polymers, [Zn(H2bibzim)(BDC)]n (1) and [Cd(H2bibzim)(BDC)]n (2) [H2bibzim ¼ 2,20-
bibenzimidazole, BDC ¼ 1,4-benzenedicarboxylate] have been synthesized under solvothermal conditions and structurally characterized.
Both 1 and 2 are constructed from infinite neutral zigzag-like one-dimensional (1D) chains. The p–p interactions and interchain
hydrogen-bonding interactions further extend the 1D arrangement to generate a 3D supramolecular architecture for 1 and 2. Both
complexes have high thermal stability and display strong blue fluorescent emissions in the solid state upon photo-excitation at 365 nm at
room temperature. They are the first two examples that 2,20-bibenzimidazole has been introduced into the d10 coordination polymeric
framework.
r 2005 Elsevier Inc. All rights reserved.
Keywords: 2,20-Bibenzimidazole; X-ray structure; Zn(II) complex; Cd(II) complex
1. Introduction
gen-bonded networks [8]. In the formally neutral form, two
nitrogen donors in coplanar rings can adopt a syn
orientation, which is similar to the chelate mode of 2,20-
bipyridine. However, H2bibzim differs from bipyridine by
the presence of five-membered rings, which change the bite
angle for chelate, resulting in the formation of a rich
Recently, the field of crystal engineering and rational
design of novel inorganic–organic hybrid materials have
attracted great interest from chemists [1,2] and consider-
able efforts have been focused on the design, synthesis and
characterization of novel multidimensional structures [3,4],
not only because of their intriguing variety of architectures
and topologies, but also because of their versatile potential
applications as ion exchange, catalysis and for the
development of optical, electronic and magnetic devices
[5,6]. The ligand 2,20-bibenzimidazole(H2bibzim) contains
multiple nitrogen-donor sites with the possibility of
reversible protonation and deprotonation properties [7]
and can be coordinated to a transition metal in non-
deprotonated (neutral, H2bibzim), mono-deprotonated
(monoanion, Hbibzim–) and di-deprotonated (dianion,
bibzim2–) forms, which has been utilized in supramolecular
chemistry for the preparation of multidimensional hydro-
variety of oligomericor polymericstrutcures
[9,10]. In
addition, the residual N–H entities form particular hydro-
gen-bond interactions from which supramolecular assem-
blies can be constructed. As a rigid and versatile bridging
ligand, 1,4-benzenedicarboxylate (BDC) has been exten-
sively studied for designing new inorganic–organic hybrid
materials, which is also a good candidate bearing a
complementary functional group linked to N–H entities
[11,12]. Therefore, with the aim of preparing novel
materials with beautiful architecture and good physical
properties, we start to synthesize new coordination
polymers constructed from 2,20-bibenzimidazole and 1,4-
BDC (Scheme 1). In the present paper, we report the
syntheses, structural characterizations, and photolumines-
cence properties of two new one-dimensional coordination
polymer [Zn(H2bibzim)(BDC)]n (1) and [Cd(H2bibzim)
Ã
Corresponding author. Fax: +86 25 83314502.
E-mail address: mengqj@nju.edu.cn (Q. Meng).
0022-4596/$ - see front matter r 2005 Elsevier Inc. All rights reserved.
doi:10.1016/j.jssc.2005.07.035

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L. Wen et al. / Journal of Solid State Chemistry 178 (2005) 3336–3341
3337
H
N
H
N
1299 (w), 1148 (m), 1034 (m), 1014 (m), 898 (m), 843 (s),
765 (m), 735 (s), 621 (w), 579 (w), 531 (m), 423 (w).
O
O
O
O
N
N
2.3. X-ray crystal structure determinations
2,2′-bibenzimidazole
1,4-benzenedicarboxylate
Intensities of complexes 1 and 2 were collected on a
Siemens SMART-CCD diffractometer with graphite-
monochromatic MoKa radiation (l ¼ 0:71073 A) using
Scheme 1.
(
(BDC)]n (2). To the best of our knowledge, they are the first
two examples that 2,20-bibenzimidazole has been introduced
into the d10 coordination polymers.
the SMART and SAINT programs [14]. The structures
were solved by direct methods and refined on F2 using full-
matrix least-squares methods with SHELXTL version 5.1
[15]. Anisotropicthermal parameters were refined for the
non-hydrogen atoms. Hydrogen atoms attached to carbon
and nitrogen were positioned geometrically (C–H ¼
0.93 A, N–H ¼ 0.86 A), and included in the refinement in
a riding model approximation with an isotropicthermal
displacement parameter fixed at 1.2 times Ueq of the atom
to which they are attached. Crystallographic data and
other pertinent information for 1 and 2 are summarized in
Table 1. Selected bond lengths and bond angles with their
estimated standard deviations are listed in Table 2.
2. Experimental
The reagents and solvents employed were commercially
available and used as received without further purification.
Ligand H2bibzim was prepared according to the previously
reported procedure [13]. The C, H, and N microanalyses
were carried out with a Perkin-Elmer 240 elemental
analyzer. The IR spectra were recorded on KBr discs
on
a Bruker Vector 22 spectrophotometer in the
4000–400 cmꢀ1 region. Luminescence spectra for the solid
samples were recorded with a Hitachi 850 fluorescence
spectrophotometer. Thermogravimetric analysis was per-
formed on a simultaneous SDT 2960 thermal analyzer.
Powder samples of complexes 1 and 2 were heated from
room temperature to 800 1C under flowing N2 at a heating
rate of 10 1C/min. Powder X-ray diffraction patterns were
recorded on a RigakuD/max-RA rotating anode X-ray
diffractometer with graphitemonochromatic CuKa
3. Results and discussion
3.1. Crystal structures of [Zn(H2bibzim)(BDC)]n (1) and
[Cd(H2bibzim)(BDC)]n (2)
The crystal structure of 1 is constructed from neutral
zigzag-like 1D chain consisting of [Zn(H2bibzim)(BDC)]
entities. Each Zn2+ ion adopts a distorted trigonal
(
(l ¼ 1:542 A) radiation at room temperature.
2.1. Preparation of [Zn(H2bibzim)(BDC)]n 1
Table 1
Crystallographicdata for 1 and 2
A mixture of Zn(NO3)2 ꢁ 6H2O (0.5 mmol, 148.8 mg),
H2bibzim (0.5 mmol, 117.3 mg), H2BDC (0.5 mmol,
82.4 mg), NaOH (1.0 mmol, 40.3 mg) and CH3CN/H2O
(12 mL, V/V ¼ 1:2) was placed in a parr Teflon-lined
stainless steel vessel (25 cm3), and then the vessel was sealed
and heated at 120 1C for 3 days. After the mixture was
slowly cooled to room temperature, yellow crystals of 1
were obtained (yield: 84% based on Zn). Anal. Calcd for
C22H14N4O4Zn: C 56.98, H 3.04, N 12.08. Found: C 56.93,
H 2.98, N 12.04%. IR spectrum (cmꢀ1): 3328 (m), 3074
(m), 1618 (m), 1560 (s), 1507 (m), 1407 (s), 1395 (s), 1353
(m), 1298 (m), 1148 (m), 1039 (m), 1012 (m), 896 (m), 847
(s), 765 (s), 738 (s), 621 (m), 584 (m), 532 (m), 427(w).
Complex
1
2
Empirical formula
Formula weight
Crystal system
Space group
a (A)
C22H14N4O4Zn
463.74
C22H14CdN4O4
510.77
Monoclinic
P21/c
Monoclinic
P21/c
7.3216(9)
21.936(3)
11.603(1)
97.663(3)
1846.9(4)
4
7.4326(14)
22.175(4)
11.752(2)
93.961(4)
1932.3(6)
4
b (A)
c (A)
b (deg)
V(A3)
Z
Dc (g/cm3)
1.668
1.371
944
1.756
1.170
1016
m (mmꢀ1
F(000)
)
Crystal size (mm3)
0.15 ꢂ 0.15 ꢂ 0.10 0.15 ꢂ 0.10 ꢂ 0.10
2y max (deg)
Index ranges
54.00
52.00
2.2. Preparation of [Cd(H2bibzim)(BDC)]n 2
ꢀ9php9
ꢀ27pkp17
ꢀ14plp14
10637
ꢀ8php9
ꢀ27pkp27
ꢀ12plp14
10310
The synthesis was similar to that described for 1 except
using CdCl2 ꢁ 2H2O (0.5 mmol) instead of Zn(NO3)2 ꢁ
6H2O, and yellow crystals of 2 were obtained (yield: 54%
based on Cd). Anal. Calcd for C22H14CdN4O4: C 51.73, H
2.76, N 10.97. Found: C 51.71, H 2.79, N 10.93%. IR
spectrum (cmꢀ1): 3448 (m), 3134 (m), 3103 (m), 1618 (m),
1577 (m), 1560 (s), 1545 (s), 1405 (s), 1395 (s), 1376 (s),
Reflns collected
Indep reflns
GOF on F2
4005
1.10
3784
1.12
R1 [I42s (I)]
wR2
Residual electron density (e Aꢀ3
0.0505
0.0995
0.0468
0.0889
)
ꢀ0.61, 0.29
ꢀ0.67, 0.50

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3338
Table 2
Selected bond lengths (A) and bond angles (deg) for 1 and 2
prismaticcoordination geometry of {ZnN 2O4}, defined by
two nitrogen donors from one non-deprotonated bidentate
H2bibzim ligand, four oxygen donors from two different
BDC anions, as indicated in Fig. 1a. The Zn–N bond
lengths are 2.086(2) and 2.107(2) A, which are comparable
to those detected in [Zn(H2biim)(H2O)](OAc)2 ꢁ
OHCH2CH2OH [16] and slightly shorter than the
apical distance (2.184(5)–2.265(5) A) in [Zn2(m-H2Biim)
(H2Biim)4](ClO4)4 ꢁ 3H2O [17]. Meanwhile, the Zn–O bond
distances fall in the range from 2.092(2) to 2.235(2) A. The
N–Zn–N angle is 79.69(9)1 whereas the O–Zn–O angles
formed by chelating carboxylate range between 60.68(8)1
and 150.88(8)1 (Table 3).
[Zn(H2bibzim)(BDC)] (1)
Zn1–O1
Zn1–O2
2.168(2)
2.154(2)
2.106(2)
60.87(8)
60.69(8)
Zn1–N4
2.086(2)
2.092(2)
2.235(2)
79.68(9)
Zn1–O3a
Zn1–O4a
N1–Zn1–N4
Zn1–N1
O1–Zn1–O2
O3a–Zn1–O4a
[Cd(H2bibzim)(BDC)] (2)
Cd1–O1
Cd1–O2
2.306(3)
Cd1–N4
Cd1–O3b
2.270(3)
2.329(4)
2.313(3)
56.04(10)
2.353(3)
2.311(3)
56.16(10)
73.72(12)
Cd1–N1
O1–Cd1–O2
N1–Cd1–N4
Cd1–O4b
O3b–Cd1–O4b
Compound 2 is isostructural to compound 1; each Cd2+
ion adopts similar distorted trigonal prismaticocordina-
tion geometry of {CdN2O4}. The Cd–N bond lengths are
2.270(3) and 2.311(3) A, which are consistent with the
reported distances for [CdBr2(H2biim)]n [18], with the
N–Cd–N angle of 73.7(1)1. The Cd–O bond distances are
in the range from 2.306(3) to 2.353(3) A with the O–Cd–O
angles varying from 56.04(10)1 to 151.34(9)1.
aEquivalent atoms generated by 1+x,1/2ꢀy,1/2+z.
bEquivalent atoms generated by 1+x, 3/2ꢀy, 1/2+z.
The two carboxylate groups are out of the plane of
correspondingly linking phenyl rings, with the dihedral
angles between them being ca. 131 and 1591 for 1 as well as
being ca. 14 and 301 for 2, respectively. These distortions
are reflected upon the 1D-arrangment, which maintains a
zigzag conformation along the growing axis, as depicted in
Fig. 1b. Each BDC anion connects two zinc centers with
the Zn?Zn separations of 10.524(1) A. The Zn–Zn–Zn
angles defined by the orientation of the two adjacent BDC
anions in the [Zn(H2bibzim)(BDC)] building units are 901,
which are far away from the ideal value of 1201. Similarly,
for 2, the Cd?Cd separations bridged by BDC anion are
10.905(1) A. The Cd–Cd–Cd angles are 901, which are
identical to those observed in 1.
For H2bibzim ligand, ring closure induces in-plane
distortions to improve the overlap between the metal
orbitals and the ligand d lone pairs, leading to a large
difference between the N1–C1–C2 and N2–C1–C2 angles
Table 3
Distances (A) and angles (deg) of hydrogen bonding for complexes 1 and 2
D–H?A
d(D–H)
d(H?A)
d(D?A)
o (D–H?A)
[Zn(H2bibzim)(BDC)] (1)
N2–H2A?O1a
N3–H3A?O3b
C17–H17?O3c
0.8600
0.8600
0.9300
2.0100
2.1200
2.5300
2.769(3)
2.799(3)
3.328(4)
147.00
136.00
144.00
[Cd(H2bibzim)(BDC)] (2)
N2–H2A?O4d
N3–H3A?O1e
C18–H18–O1f
0.8600
0.8600
0.9300
2.0500
2.0500
2.5400
2.768(4)
2.788(4)
3.338(4)
141.00
143.00
144.00
aEquivalent atoms generated by ꢀx, 1ꢀy, 2ꢀz.
bEquivalent atoms generated by ꢀx, 1/2+y, 3/2ꢀz.
cEquivalent atoms generated by x,1/2ꢀy,1/2+z.
dEquivalent atoms generated by ꢀx, ꢀ1/2+y, 1/2ꢀz.
eEquivalent atoms generated by ꢀx, 1ꢀy, 1ꢀz.
fEquivalent atoms generated by x, 3/2ꢀy, ꢀ1/2+z.
Fig. 1. (a) Coordination environment of Zn(II) metal ion in 1. (b) A 1D
zigzag conformation of 1 with hydrogen atoms omitted for clarity. (c)
Crystal packing diagram for complex 1 on bc plane with hydrogen bonds
indicated by dashed lines.

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3339
(ꢃ1171 versus ꢃ1291) for 1. Obviously, for 2, the difference
between the two angles (ꢃ1191 versus ꢃ1271) is somewhat
smaller than that in 1. The central C1–C2 bond length
found for 1 is 1.468(3) A and for 2 is 1.447(5) A, which is
slightly longer than those observed in free biimidazole [19]
and [Ni(H2biim)2(H2O)2](NO3)2 [20] (1.423, and 1.441 A,
respectively). For both compounds, although the two
independent benzimidazole rings remain individually pla-
nar, the H2bibzim molecule is bent slightly about the
C1–C2 bond, leading to a dihedral angle of 4.61 for 1 and
4.11 for 2 between these benzimidazole rings. The 1D
systems run in an almost parallel alignment to each other,
allowing face-to-face p–p interactions between adjacent
benzene rings (3.748 A for 1, 3.722 A for 2) and imidazole
rings (3.745 A for 1, 3.657 A for 2) to sustain the 2D-
assembly extended in the ab plane, as illustrated in Fig. 2.
As anticipated, the couple of N–H groups of each
bibenimidazole molecule are involved in hydrogen bonds
with the carboxylate oxygen atoms. For 1, the N2?O1a
distance of 2.769(3) A and N3?O3b distance of 2.799(3) A
correspond to strong interactions. The four atoms N(2),
O(1), N(3), and O(3) are almost coplanar, with a mean
deviation of 0.0122 A. Furthermore, the O3 atom also has
weak interaction with C17 atom via a nonclassical
hydrogen bond, C17–H17?O3c distance of 3.328(4) A.
As a consequence, the p–p interactions and interchain
hydrogen-bonding interactions further extend the 1D
arrangement to generate a 3D supramolecular architecture
(Fig. 1c).
strong interactions. The four atoms N(2), O(4), N(3), and
O(1) are not coplanar, with a mean deviation of 0.4795 A,
which is distinctly larger than those in 1. In addition, there
also exist interlayer weak hydrogen bond interactions with
C18–H18?O1f distance of 3.338(4) A. Doubtless, the
combination of p–p overlap and interchain hydrogen-
bonding interactions further extend the 1D chain to afford
a 3D framework, as displayed in Fig. S1.
3.2. IR spectra
The broad absorption bands of 3328 and 3074 cmꢀ1 for 1
and the 3448, 3134 and 3103 cmꢀ1 for 2 in the IR spectra
can be assigned to the n(N–H) stretching vibrations [17,21].
The coordination fashion of the H2BDC moiety to the
metal atom in 1 and 2 is proved by the shifts of the
stretching vibrations nas and ns of the carboxyl group. The
difference between naꢀs(1OCO) (1560 cmꢀ1) and ns(OCO)
(1407 cmꢀ1) is 153 c m for 1, which is indicative of a
chelating carboxyl group. For 2, the difference between
nas(OCO) (1545 cmꢀ1
)
and ns(OCO) (1405 cmꢀ1
)
is
140 cmꢀ1 also indicative of a chelating one [22], which
are consistent with the crystal structures. For the two
compounds, the difference in the increment extent of the
ligand conformational rigidity and conjugation due to their
coordination to different metal ions may exert a little
influence on their stretching modes.
For 2, the N2?O4d distance is 2.768(4) A and N3?O1e
distance is 2.788(4) A with the N–H?O systems not
deviated much from linearity (ꢃ1431), also indicating
3.3. XRD spectra and thermogravimetric analyses
The purity of complexes 1 and 2 was confirmed by X-ray
power diffraction analyses, in which the experimental
spectra of both compounds are almost consistent with
their simulated spectra (Figs. S2 and S3).
Complexes 1 and 2 are air stable. The TG data of 1
shows that the complex is stable up to 163 1C; decomposi-
tion of 2 begins from 271 1C, which has higher thermal
stability than 1, as indicated in Fig. 3.
1.0
0.8
0.6
0.4
0.2
200
400
600
800
Temperature (°C)
Fig. 2. Face-to-face p–p interactions between adjacent benzene rings and
imidazole rings from two nearest 1D zigzag chains for 2.
Fig. 3. TG curve of 1 (dashed line) and 2 (full line).

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3340
3.4. Photoluminescence properties
emissions described above for 1 and 2 to LLCT (ligand–
ligand charge transfer) excited states. The shift of the
emission bands for the two complexes is probably due to
the differences of metal ions [25].
The emission spectra of complexes 1 and 2 in the solid
state are investigated at room temperature. Excitation at
365 nm leads to strong blue-fluorescent emission band at
454 nm for 1 while intensely strong blue-fluorescent
emission bands are observed at 442 and 480 nm for 2
under the same conditions, as indicated in Figs. 4 and 5.
These emissions are neither metal-to-ligand charge transfer
(MLCT) nor ligand-to-metal transfer (LMCT) in nature
since the Zn2+ or Cd2+ ions are difficult to oxidize or to
reduce due to their d10 configuration [23]. For the free
H2BDC ligand, the emission band at 387 nm
(lex ¼ 351 nm) can be assigned to p–p* transition. In
addition, for the free H2bibzim, the emission bands at 499,
535, 580 nm (lex ¼ 491 nm) are assigned to the intraligand
1(p2)–1(p, p*) transition [24]. Therefore, we assign the
4. Supplementary materials
Fig. S1 illustrated a 3D framework for 2 and Figs. S2
and S3 indicated the experimental and simulated XRD
spectra for both compounds are included. Crystallographic
data (excluding structure factors) for the structure(s)
reported in this paper have been deposited with the
Cambridge CrystallographicData Centre as supplemen-
tary publication numbers: CCDC 259379 (1), CCDC
249725 (2). Copies of the data can be obtained free of
charge on application to CCDC, 12, Union Road, Cam-
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
320
330
340
350
360
370
380 390
Wavelength (nm)
1.4
400
420
440
460
480
500
520
Wavelength (nm)
Fig. 4. Solid-state excitation and emission spectra of 1 at room temperature.
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
320
330
340
350
360
370
380
390
Wavelength (nm)
360
380
400 420 440 460
480
500 520
540
Wavelength (nm)
Fig. 5. Solid-state excitation and emission spectra of 2 at room temperature.

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bridge CB2 1EZ, UK (fax: +44 1223 336 033; E-mail:
deposit@ccdc.cam.ac.uk).
[7] T. Akutagawa, G. Saito, M. Kusunoki, K. Sakaguchi, Bull. Chem.
Soc. Jpn. 69 (1996) 2487.
[8] M. Tadokoro, K. Nakasuji, Coord. Chem. Rev. 198 (2000) 205 and
references cited therein.
Acknowledgment
[9] S. Fortin, A.L. Beauchamp, Inorg. Chem. 39 (2000) 4886.
[10] C.A. Hester, R.G. Baughman, H.L. Collier, Polyhedron 16 (1997)
2893.
We thank the National Nature Science Foundation of
China (No. 20490218); Jiangsu Science & Technology
Department and the Center of Analysis and Determining
of Nanjing University for the financial support.
[11] (a) H. Li, M. Eddaoudi, O.M. Yaghi, Nature 402 (1999) 276;
(b) R.H. Groenman, L.R. MacGillivaray, J.L. Atwood, Chem.
Commun. (1998) 2735.
˜
[12] R. Atencio, M. Chacon, T. Gonzalez, A. Briceno, G. Agrifoglio, A.
´ ´
Sierraalta, J. Chem. Soc., Dalton Trans. (2004) 505.
[13] B.F. Fieselmann, D.N. Hendrickson, G.D. Stucky, Inorg. Chem. 17
(1978) 2078.
Appendix A. Supplementary data
[14] SMART and SAINT, Area Detector Control and Integration
Software, Siemens Analytical X-ray Systems, Inc., Madison, WI,
1996.
Supplementary data associated with this article can be
found in the online version at doi:10.1016/j.jssc.2005.
07.035
[15] G.M. Sheldrick, SHELXTL V5.1, Software Reference Manual,
Bruker AXS, Inc., Madison, WI, 1997.
References
[16] B.H. Ye, F. Xue, G.Q. Xue, L.N. Ji, T.C.W. Mak, Polyhedron 18
(1999) 1785.
[17] C. Kirchner, B. Krebs, Inorg. Chem. 26 (1987) 3569.
[18] C.A. Hester, H.L. Collier, R.G. Baughman, Polyhedron (1996)
4255.
[1] J.M. Lehn, Supramolecular Chemistry: Concepts and Perspectives,
VCH, New York, 1995.
[2] G.R. Desiraju, Crystal Design: Structure and Function, Perspectives
in Supramolecular Chemistry, vol. 6, Wiley, Chichester, 2003.
[3] (a) M. Eddaoudi, D.B. Moler, H.L. Li, B.L. Chen, T.M. Reineke, M.
O’Keeffe, O.M. Yaghi, Acc. Chem. Res. 34 (2001) 319;
(b) S.L. James, Chem. Soc. Rev. 32 (2003) 276;
[19] D.T. Cromer, R.R. Ryan, C.B. Storm, Acta Crystallogr., Sect. C 43
(1987) 1435.
[20] A.D. Mighell, C.W. Reiman, F.A. Maver, Acta Crystallogr., Sect. B
25 (1969) 60.
[21] A. Maiboroda, G. Rheinwald, H. Lang, Eur. J. Inorg. Chem. (2001)
2263.
(c) A.N. Khlobystov, A.J. Blake, N.R. Champness, D.A. Leme-
novskii, A.G. Majouga, N.V. Zyk, M. Schroder, Coord. Chem.
¨
[22] G.B. Deacon, R.J. Phillips, Coord. Chem. Rev. 33 (1980)
227.
Rev. 222 (2001) 155.
[4] L. Carlucci, G. Ciani, D.M. Proserpio, Coord. Chem. Rev. 246 (2003)
247.
[23] W. Zhao, H.F. Zhu, T.-A. Okamura, W.Y. Sun, N. Ueyama,
Supramolecular Chemistry (2003) 345.
[5] B. Moulton, M.J. Zaworotko, Chem. Rev. 101 (2001) 1629.
[6] (a) K. Inoue, H. Imai, P.S. Ghalsasi, K. Kikuchi, M. Ohba,
H. Okawa, J.V. Yakhmi, Angew. Chem., Int. Ed. 40 (2001) 4242;
[24] B.C. Tzeng, D. Li, S.M. Peng, C.M. Che, J. Chem. Soc. Dalton
Trans. (1993) 2365.
(b) J. Ramo
´
n, G. Mascaro
´
s, K.R. Dunbar, Angew. Chem., Int. Ed.
[25] Z.Y. Fu, X.T. Wu, J.C. Dai, S.M. Hu, W.X. Du, H.H. Zhang, R.Q.
Sun, Eur. J. Inorg. Chem. (2002) 2730.
42 (2003) 2289.