Synthesis, structure and photoluminescence of a 2-D cadmium (II) metal-organic framework: [Cd(μ4-NIPH)(μ2-OH2)]n (NIPH = 5-nitroisophthalate)

Article abstract of DOI:10.1016/j.inoche.2006.04.017

A cadmium metal-organic framework [Cd(μ₄-NIPH)(μ₂-OH₂)]_n (1) has been prepared by reaction of H₂NIPH (H₂NIPH = 5-nitroisophthalic acid) with Cd (II) under hydrothermal condition and characterized by single-crystal X-ray diffraction and TGA analysis. Single crystal X-ray diffraction analysis indicated that 1 is a 2-D layer structure constructed from polynuclear cadmium chains and bridge NIPH ligands. Furthermore, the layers are connected into 3-D supramolecular network through hydrogen bonds. The framework 1 exhibits photoluminescence at room temperature.

Full text of DOI:10.1016/j.inoche.2006.04.017

Inorganic Chemistry Communications 9 (2006) 744–747
www.elsevier.com/locate/inoche
Synthesis, structure and photoluminescence of a 2-D cadmium(II)
metal-organic framework: [Cd(l4-NIPH)(l2-OH2)]n
(NIPH = 5-nitroisophthalate)
*
Junwei Ye, Ping Zhang, Kaiqi Ye, Weirong Yin, Ling Ye, Guangdi Yang, Yue Wang
Key Laboratory for Supramolecular Structure and Materials of Ministry of Education, College of Chemistry, Jilin University, Changchun,
Jilin 130012, PR China
Received 9 April 2006; accepted 20 April 2006
Available online 3 May 2006
Abstract
A cadmium metal-organic framework [Cd(l4-NIPH)(l2-OH2)]n (1) has been prepared by reaction of H2NIPH (H2NIPH = 5-nitroi-
sophthalic acid) with Cd (II) under hydrothermal condition and characterized by single-crystal X-ray diffraction and TGA analysis. Sin-
gle crystal X-ray diffraction analysis indicated that 1 is a 2-D layer structure constructed from polynuclear cadmium chains and bridge
NIPH ligands. Furthermore, the layers are connected into 3-D supramolecular network through hydrogen bonds. The framework 1
exhibits photoluminescence at room temperature.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Metal-organic framework; Crystal structure; Hydrogen bonding; Photoluminescence
The rational design and self-assembled construction of
novel functional supramolecular coordination polymers
or metal-organic frameworks (MOFs) has drawn consider-
able attention in the field of crystal engineering and mate-
rial chemistry [1]. This is due to their intriguing network
topologies and diverse potential for scientific and techno-
logical applications as selective absorption, separation,
catalysis, ion exchange, gas storage, optoelectronic and
magnetic materials [2–5]. To date, MOFs are usually built
up from metal–oxygen or metal–nitrogen molecular build-
ing blocks linked to each other through organic bridging
ligands [6]. For example, Yaghi and co-workers have
reported a series of extended metal-organic open frame-
works with rigid spacers and paddle-wheel building blocks
[M2(CO2R)4] which can be considered as square molecular
building blocks in polyhedral networks [7]. In an effort of
establishing strategies aimed at designing novel metal-
organic frameworks, some multidentate carboxylate
ligands, e.g., terephthalate, 1,3,5-benzenetricarboxylate
and 1,2,4,5-benzenetetracarboxylate, are usually chosen
to bind metal centers into metal–oxygen clusters, which
may act as secondary building units to construct supramo-
lecular architectures [8]. Recent studies have shown that 5-
nitroisophthalate (NIPH or nip) is a versatile ligand [9].
For example, in coordination polymer [Zn(l3-OH)2(nip)]n,
two carboxylate groups form covalent bonds with Zn cen-
ters while nitro group acts as hydrogen-bond acceptors
[9e]. In the present study, we report the preparation [10],
crystal structure [11] and properties of a novel 2-D cad-
mium (II) metal-organic framework [Cd(l4-NIPH)(l2-
OH2)]n (1).
The colorless crystals of the 1 were obtained by using the
hydrothermal synthesis method. The X-ray power diffrac-
tion pattern (XRD) of 1 was in good agreement with those
generated from single-crystal structure analysis result (see
Supplementary materials: Fig. S1). X-ray diffraction analy-
sis reveals that 1 is a 2-D layer framework. The asymmetric
unit consists of one crystallographically independent Cd
atom, one NIPH ligand and one coordinating water mole-
*
Corresponding author. Fax: +86 431 5193421.
E-mail address: yuewang@jlu.edu.cn (Y. Wang).
1387-7003/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2006.04.017

J. Ye et al. / Inorganic Chemistry Communications 9 (2006) 744–747
745
cule. The local coordination environment around the Cd
O
O
atom can be described as a slightly distorted pentagonal
bipyramidal formed by seven oxygen atoms from four
carboxylates of NIPH ligands and two coordination water
molecules (Fig. 1a). The Cd–O distances and O–Cd–O
N
˚
Cd
angles range from 2.2474(18) to 2.591(2) A and from
53.36(6)ꢁ to 162.06(6)ꢁ, respectively, which are in good
agreement with those found in other extended structures
constructed from NIPH ligand [9].
O
O
Cd
Each NIPH ligand in 1 displays a l4-bridging mode to
connect with four Cd atoms and the two carboxylic groups
adopt tridentate and bidentate-chelating coordination
mode, respectively (Scheme 1). Two cadmium atoms are
linked together by two carboxylate groups and two l2-
OH2 to form a dinuclear [Cd2(l2-OH2)2(CO2R)6] building
O
O
Cd
Cd
Scheme 1. The coordination modes of the carboxylic groups of NIPH
ligand in 1.
˚
cent chains are connected through NIPH ligands to form 2-
D layer framework (Fig. 2). In addition, there exist strong
O–HÁ Á ÁO hydrogen bonds between water molecules and
block (CdÁ Á ÁCd 3.46 A) (Fig. 1b). As a result, polynuclear
cadmium chain based on [Cd2(l2-OH2)2(CO2)6] building
blocks is formed through the oxygen atoms (O1 and its
equivalent atoms) of the l2-bridging tridentate carboxylate
groups (represented as an edge-sharing polyhedral, with
˚
NIPH ligands in layers [O(7)Á Á ÁO(4) 2.633(2) A]. Finally,
the whole 3-D supramolecular network (Fig. 3) is then sta-
˚
bilized by inter-layer strong O–HÁ Á ÁO and C–HÁ Á ÁO hydro-
Cd–Cd inter-chain separation 3.649 A, Fig. S2). The adja-
Fig. 1. Perspective view of coordination environment of Cd(II) (a) and building block [Cd2(l2-OH2)2(CO2R)6] (b) in 1.

746
J. Ye et al. / Inorganic Chemistry Communications 9 (2006) 744–747
Fig. 2. A polyhedral representation of the 2-D layer structure of polynuclear cadmium chains coordinated linking of organic ligands of NIPH.
Fig. 3. The 3-D supramolecular network formed by hydrogen bonds
packed along a-axis of 1.
300
350
400
450
500
550
600
gen bonds in which nitro groups as acceptor (see Supple-
mentary materials: Table S3 and Fig. S3).
Wavelength (nm)
Fig. 4. The emission spectrum of 1 at room temperature.
The framework 1 is stable in air at ambient temperature
and almost insoluble in common solvents, such as water,
chloroform, carbon tetrachloride, alcohol, acetone and ace-
tonitrile. The thermal behavior of 1 was examined by ther-
mogravimetric analysis (TGA) under atmosphere with the
heating rate of 10 ꢁC minÀ1. The TGA result indicates that
1 does not decompose up to 188 ꢁC. Due to the loss of water
molecules, the first weight loss of 5.11% occurs from 188 to
253 ꢁC, which is consistent with the calculated value 5.31%.
The second weight loss between 393 and 664 ꢁC is ascribed
to the loss of NIPH ligands. The remaining product is cad-
mium oxides CdO (38.20%), which is in agreement with the
calculated value (37.82%). 1 displays strong blue emission
with maximum intensity at 431 nm (kex = 308 nm). The
emission spectrum of 1 in the solid state at room tempera-
ture is presented in Fig. 4. It may be possible to develop high
stable luminescent materials based on 1.
together with carboxylate groups and l2-OH2 to form poly-
nuclear cadmium chains. The adjacent chains are connected
through NIPH ligands to form 2-D layer structure. Three-
dimensional supramolecular framework are further formed
via inter-layer hydrogen bonding interaction. 1 exhibits
strong blue photoluminescence at room temperature.
Acknowledgements
This work was supported by the National Natural Sci-
ence Foundation of China (50225313 and 50520130316),
the Major State Basic Research Development Program
(2002CB613401) and the Program for Changjiang Scholars
and Innovative Research Team in University (IRT0422).
Appendix A. Supplementary data
In summary, we have successfully synthesized a novel 2-
D
cadmium (II) metal-organic framework [Cd(l4-
Crystallographic data for 1 have been deposited at the
Cambridge Crystallographic Data Center with the deposi-
tion number of CCDC 603977. These data can be obtained
NIPH)(l2-OH2)]n (1) under hydrothermal conditions. In
1, two kinds of coordination mode for NIPH ligand have
been demonstrated. The cadmium atoms are linked

J. Ye et al. / Inorganic Chemistry Communications 9 (2006) 744–747
747
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