Construction, photoluminescence, and catalytic reactivity study of Cd(II) complexes containing amide ligand with hydrogen-bond capable backbone: 1-Dimensional looped chain

Article abstract of DOI:10.1016/j.inoche.2010.08.025

Three new Cd(II) complexes containing 3-bpdb ligands with amide moiety as hydrogen-bond capable backbone, formulated as [Cd(3-bpdb)X₂] _n (3-bpdb = N,N′-dipyridin-3-ylpyridine-2,6-dicarboxamide, X = Cl (1), Br (2), and I (3)), have been synthesized. All three compounds show 1-dimensional looped chain structures, and intra- and inter-molecular hydrogen bonding interactions provide 2-dimensional sheets. Among three pausible conformers of ligand 3-bpdb, all three halide compounds show only anti-anti conformation to provide 1-dimensional looped chains. In addition, emissions of compounds 1 and 2 were observed at 424 nm and 431 nm, respectively, suggesting that they might be a good candidate for a potential hybrid inorganic-organic photoactive material. Moreover, compounds 1-3 carried out an efficient transesterification of vinyl acetate.

Full text of DOI:10.1016/j.inoche.2010.08.025

Inorganic Chemistry Communications 13 (2010) 1493–1496
Contents lists available at ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
Construction, photoluminescence, and catalytic reactivity study of Cd(II) complexes
containing amide ligand with hydrogen-bond capable backbone: 1-Dimensional
looped chain
a
a
a
a
a
a,
Tae Geum Lee , Ju Hoon Lee , Min Young Hyun , Seung Pyo Jang , Hong Gyu Lee , Cheal Kim ⁎,
b,
b
Sung-Jin Kim ⁎, Youngmee Kim
a
Department of Fine Chemistry, Seoul National University of Technology, Seoul 139-743, Republic of Korea
Department of Chemistry and Nano Science, Ewha Womans University, Seoul 120-750, Republic of Korea
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Three new Cd(II) complexes containing 3-bpdb ligands with amide moiety as hydrogen-bond capable backbone,
Received 13 July 2010
Accepted 23 August 2010
Available online 6 September 2010
2 n
formulated as [Cd(3-bpdb)X ] (3-bpdb=N,N′-dipyridin-3-ylpyridine-2,6-dicarboxamide, X=Cl (1), Br (2), and
I (3)), have been synthesized. All three compounds show 1-dimensional looped chain structures, and intra- and
inter-molecular hydrogen bonding interactions provide 2-dimensional sheets. Among three pausible conformers of
ligand 3-bpdb, all three halide compounds show only anti–anti conformation to provide 1-dimensional looped
chains. In addition, emissions of compounds 1 and 2 were observed at 424 nm and 431 nm, respectively, suggesting
that they might be a good candidate for a potential hybrid inorganic–organic photoactive material. Moreover,
compounds 1–3 carried out an efficient transesterification of vinyl acetate.
Keywords:
Cd(II) complexes
N,N′-dipyridin-3-ylpyridine-2,6-dicarboxamide
Photoluminescence
1-Dimensional looped chain
© 2010 Elsevier B.V. All rights reserved.
Catalytic reactivity
Luminescent coordination compounds with nitrogen-containing
ligands have attracted much attention recently due to their good per-
formance in sensor technologies and luminescent devices [1]. In addi-
tion, there has been growing interest in the cadmium(II) complexes
possessing one-, two-, or three-dimensional infinite frameworks due
to their photoluminescence, nonlinear optical (NLO) and other func-
tional properties [2,3]. Cadmium(II) with d10 configuration can adopt a
variety of coordination geometries, which can range within tetrahedral,
trigonal bipyramidal, square pyramidal and octahedral and are par-
ticularly useful for the construction of coordination frameworks [3].
On the other hand, hydrogen bonding plays a crucial role in the
construction of coordination polymers [4]. Combination of both
metal–ligand covalent bonding and hydrogen bonding in designing
the coordination polymers has been considered an attractive design
strategy because of the possibility of structural variations and guest
entrapment induced by specific hydrogen bonding interactions. This
may be achieved using ligands with hydrogen-bond capable back-
bones such as amide and urea which are known for their well-studied
hydrogen bonding interactions [5]. These building blocks contain
multi-oxygen and nitrogen atoms and can coordinate with metal ions
in different ways, resulting in the formations of various coordination
polymers with specific topologies and useful properties.
In the present study, we explored the ligands with multiple
hydrogen bonding sites; having more than one hydrogen bonding
functionalities in the backbone [5], it is expected that the backbone
will be involved in hydrogen bonding interactions with the counter
anions, with itself and with the entrapped or metal bound solvents.
Therefore, it can coordinate with metal ions in multi-coordinated
ways to form a series of the coordination polymers with interesting
properties.
In our efforts to construct the coordination polymers with lumi-
nescent properties and catalytic reactivity [6], and to investigate
the design and control of the self-assembly of an organic/inorganic
supramolecular motif with angular bridging ligands having amide
moieties, N,N′-dipyridin-3-ylpyridine-2,6-dicarboxamide (3-bpdb)
has attracted our attention in connection with structural control of
discrete or divergent coordination networks [7].
Herein we report the synthesis, crystal structures, photolumines-
cence, and catalytic activity of Cd-containing polymeric compounds
formed by the reaction of the ligand N,N′-dipyridin-3-ylpyridine-2,
6-dicarboxamide (3-bpdb) [7] and CdX
2
salts (X=Cl, Br, I). More-
over, the thermal stabilities of these complexes were also examined.
⁎
Corresponding authors. C. Kim is to be contacted at Department of Fine Chemistry,
Seoul National University of Technology, Seoul 139-743, Republic of Korea. Tel.: +82 2
70 6693; fax: +82 2 973 9149. S.-J. Kim, Department of Chemistry and Nano Science,
9
We present, for the first time, three new Cd(II) complexes con-
Ewha Womans University, Seoul 120-750, Republic of Korea. Tel.: +82 2 3277 3589;
fax: +82 2 3277 2384.
taining 3-bpdb ligands, formulated as [Cd(3-bpdb)X
2 n
] (X=Cl (1),
E-mail addresses: chealkim@snut.ac.kr (C. Kim), sjkim@ewha.ac.kr (S.-J. Kim).
Br (2), and I (3)). Compounds 1–3 were prepared by a direct diffusion
1387-7003/$ – see front matter © 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2010.08.025

1494
T.G. Lee et al. / Inorganic Chemistry Communications 13 (2010) 1493–1496
technique where an aqua solution of the CdX
methanol solution of 3-bpdb ligands [8]. Thermal gravimetric analysis
TGA) of compounds 1–3 showed that all three compounds are stable
2
is carefully layered by a
(
below 300 °C, which indicates their good thermal stability (Fig. S1).
The three compounds are isostructural [9], and there is an in-
version center on a Cd(II) ion. 3-bpdb ligands bridge Cd(II) ions to
provide 1-dimensional looped chains (Fig. 1). The geometry of a Cd(II)
ion of each compound is distorted octahedral constructed from four
nitrogen atoms of 3-bpdb and two halides. There are water solvent
molecules inside the looped chains. There are intra-molecular hydro-
gen bonding interactions between amido hydrogen atoms and pyridyl
nitrogen atoms (green dotted lines), and inter-molecular hydrogen
bonding interactions between water hydrogen atoms and halide ligands
(
green dotted lines) (Fig. 2(a)), and between water hydrogen atoms and
neighboring carbonyl oxygen atoms (red dotted lines) (Fig. 2(b)). These
hydrogen bonding interactions provide 2-dimensional sheets as shown
in Fig. 2(b). The Cd–N bond distances are 2.435(3) and 2.479(3) Å, and
the Cd–Cl distance is 2.5703(9) Å for 1. The Cd–N bond distances are
2
.416(2) and 2.494(2) Å, and theCd–Brdistanceis 2.7172(3) Å for 2. The
Cd–N bond distances are 2.383(3) and 2.521(3) Å, and the Cd–I distance
is 2.9133(3) Å for 3.
Similar conformationally flexible bis-pyridyl-bis-amide ligand (N,
N′-bis-(3-pyridyl)isophthalamide) has been studied since it is
expected to display conformation dependent ligating topologies due
to the meta-positioning of the pyridyl N atoms. There are 10 pausible
conformars depending on the relative orientation of the amide and
pyridyl moieties [10]. In this 3-bpdb ligand, the middle pyridyl group
increased rigidity of the ligand because of inter-molecular hydrogen
bonds between middle nitrogen atom and amide hydrogen atoms
(
(
Fig. 2(a)). So, there are only 3 pausible conformers in this system
Scheme 1). All three halide compounds show 3-bpdb ligands bridged
Fig. 2. (a) Intra-molecular hydrogen bonds for 1 between the middle pyridyl nitrogen
atoms and the amido hydrogen atoms, and inter-molecular hydrogen bonds between
water hydrogen atoms and chlorides (green dotted lines). (b) 2-Dimensional sheet of 1
containing intra- and inter-molecular hydrogen bonds (green dotted lines) and inter-
molecular hydrogen bonds (red dotted lines). See the Supplementary Information for
hydrogen bond distances.
Cd(II) ions with anti–anti conformation (conformar a in Scheme 1)
to provide 1-dimensional looped chains. The amide hydrogen atoms
capture a water molecule through hydrogen bonds, and hydrogen
bonds between water hydrogen atoms and neighboring carbonyl
oxygen atoms provide 2-dimensional sheet.
Coordination polymers, especially ones with d10 metal centers,
are of great current interest because of their various applications in
2 2 n
Fig. 1. 1-Dimensional looped chain, [Cd(3-bpdb) X ] (X=Cl for 1, Br for 2, and I for 3).

T.G. Lee et al. / Inorganic Chemistry Communications 13 (2010) 1493–1496
1495
Scheme 1. 3 pausible conformers of 3-bpdb.
chemical sensors, photochemistry, and electroluminescent display
1–3]. Therefore, the emission spectra of Cd(II) complexes 1–3,
the use of Cd-containing polymeric compounds for the transester-
ification reaction [6a,b].
[
together with that of the ligand 3-bpdb were measured in the solid
state at room temperature (see Fig. 3). Emissions of compounds 1, 2,
and ligand were observed at 424 nm (λex =326 nm) for 1, 431 nm
In summary, we have synthesized three new Cd(II) complexes
containing 3-dpdb ligands with amide moiety as hydrogen-bond
capable backbone, formulated as [Cd(3-bpdb)X ] (3-bpdb=N,N′-
2 n
(
λ
ex =326 nm) for 2, and 431 nm (λex =326 nm) for 3-bpdb, respec-
dipyridin-3-ylpyridine-2,6-dicarboxamide, X=Cl (1), Br (2), and
I (3)). All three compounds show 1-dimensional looped chain struc-
tures, and intra- and inter-molecular hydrogen bonding interactions
provide 2-dimensional sheets.
Luminescent properties of 1 and 2 indicate that they may be a good
candidate for luminescent metal compounds with potential applica-
tions in optoelectronic devices. The catalytic activity of compounds 1–
3 for transesterification of vinyl acetate suggests that this catalytic
system can be useful for preparing various esters by transesterifica-
tion under the neutral conditions.
tively, but complex 3 exhibited a very weak emission band at the same
position (λex =326 nm) as 2 and the ligand. These results indicate
that the emission intensities of the complexes 1–3 were dependent
on the anions used, ClNBrNI, which can be explained by a heavy-atom
quenching effect [11]. On the other hand, such emissions of complexes
1
and 2 can be tentatively assigned to the intraligand transition of
ligand, since the similar emissions were observed for the ligands
12]. These results suggest that 1 and 2 may be a good candidate for a
[
potential hybrid inorganic–organic photoactive material [13].
Transesterification reaction, one of the effective methods for ester
synthesis, is important in industrial organic synthesis as well as in
academic laboratory scale reactions [14]. There are many catalysts
available for transesterification, and the most common procedure is
to reflux the ester with a catalytic amount of Ti(O-i-Pr)
cohol solvent [15]. Other Lewis acid catalysts such as BuSn(OH)
Al(OR) also catalyze this conversion [16], but require higher reaction
Acknowledgments
Financial support from Korea Ministry Environment “ET-Human
resource development Project”, Korean Science & Engineering Founda-
tion (R01-2008-000-20704-0 and2009-0074066), ConvergingResearch
Center Program through the National Research Foundation of Korea
4
in an al-
3
and
3
temperature and acidic conditions. These drawbacks experienced
with these catalysts make worthwhile the search for new catalysts
that operate under milder conditions. Thus, we examined the catalytic
activity of the polymeric compounds 1–3 for transesterification of
ester vinyl acetate. Treatment of vinyl acetate (50 mmol) and meth-
anol in the presence of 1–3 (1 mmol) at room temperature quan-
titatively produced methyl acetate within 2 day by 1, 2 day by 2, and
(
(
NRF) funded by the Ministry of Education, Science and Technology
2009-0082832), and the SRC program of MOST/KOSEF through the
Center for Intelligent Nano-Bio Materials at Ewha Womans University
R11-2005-008-00000-0) is gratefully acknowledged.
(
Appendix A. Supplementary Material
3
day by 3, suggesting that this catalytic system can be useful for
CCDC 777825–777827 contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
preparing various esters by transesterification under the neutral
conditions. Little transesterification occurs without the polymeric
compounds. To the best of our knowledge, this is the third report on
Supplementary materials related to this article can be found online
at doi:10.1016/j.inoche.2010.08.025.
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1
6
702(s), 1588(m), 1539(s), 1487(m), 1431(s), 1339(w), 1001(w), 804(m), 748(m),
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2
3
−
1
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1
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