A luminescent cage-like complex constructed by bidentate pyridine-containing ligand and silver nitrate

Article abstract of DOI:10.1002/zaac.201200344

The cage-like complex, Ag₄L₄(NO₃) ₄ (1) [L = 1, 4-bis(pyridine-2-ylmethoxy)benzene] was synthesized by the reaction of the flexible bidentate ligand and silver nitrate. It was characterized by elemental analysis, IR spectroscopy, TG, and single-crystal X-ray analysis. Complex 1 is reported as the first cage-like cluster constructed by four nitrate anions bridging two [2+2] macrocycles. A blue luminescent emission and luminescent enhancement effect are observed in complex 1. Copyright

Full text of DOI:10.1002/zaac.201200344

ARTICLE
DOI: 10.1002/zaac.201200344
A Luminescent Cage-Like Complex Constructed by Bidentate Pyridine-
Containing Ligand and Silver Nitrate
Ying Liu,[a,b] Ying-Hui Yu, Yi-Fu Liu, Guang-Feng Hou,* Xiao-Dan Wang,
[a]
[a]
[a]
[a]
[a]
[a,c]
Bo Wen, and Jin-Sheng Gao*
Keywords: Cage-like complexes; Flexible bidentate ligand; Silver; Crystal structure
Abstract. The cage-like complex, Ag
4
L
4
(NO
3
)
4
(1) [L = 1,4-bis(pyrid-
Complex 1 is reported as the first cage-like cluster constructed by four
nitrate anions bridging two [2+2] macrocycles. A blue luminescent
emission and luminescent enhancement effect are observed in complex
1.
ine-2-ylmethoxy)benzene] was synthesized by the reaction of the flexi-
ble bidentate ligand and silver nitrate. It was characterized by elemen-
tal analysis, IR spectroscopy, TG, and single-crystal X-ray analysis.
Introduction
tures (Scheme 1). More recently, 1,4-bis(pyridine-2-ylmeth-
oxy)benzene and its derivatives as a new family of multi-
Design and assembly of metal-organic complexes (MOCs)
with definite organic ligands and d metal ions have been
widely studied in recent years, which endow them with poten-
pyridyl benzene ligands are investigated by many chemists and
1
0
us.[
24–27]
Many compositionally and geometrically different
but topologically identical assembly pairs, for example,
[1–3]
tial applications in fields such as photocatalysts,
lumines-
[28]
[29]
[30]
M L ,
and M L ,
and M4L
6
have been obtained by
[4]
4
2
4
4
cent-based chemical sensors,
organic light-emitting di-
deliberate combination of different metal ions and ligands. Su
odes,[ and solar-energy conversion. Among those metals,
5]
[6]
has reported the syntheses and structural characterization of
1
0
I
group 11 d metals especially Ag complexes are beginning
to receive particular attention, due to their interesting photolu-
minescence properties. In contrast to copper and gold, silver
has more potential application value in that it is more stable
than copper and cheaper than gold. Thus more and more silver
complexes with luminescent properties have been investi-
gated.[
[20]
trigonal M L and tetragonal M L molecular boxes.
To the
2
3
2 4
best of our knowledge, tetranuclear cage-like complexes built
I
by flexible bipyridyl ligand and Ag have been reported rarely
to date. In our attempt to synthesize the cage-like complex
I
based on angular bipyridyl benzene ligand and Ag , a novel
7–10]
It is well known that the flexible ligand can afford a good
opportunity to enrich the intrinsic diversity of MOCs and they
have been widely used in the construction of MOCs with fasci-
[11–13]
nating structures and attractive properties.
These ligands
with facile twisted conformations can give versatile topologies,
such as helical structures and interpenetrating networks.[
In addition, the flexible molecules modified by rigid center are
14–19]
apt to form macrocycles, cages, and macroporous frame-
works.[
20–23]
Multipyridyl benzene ligands are commonly em-
ployed building units for constructing many fascinating struc-
*
*
Dr. G.-F. Hou
E-Mail: hgf1000@163.com
Prof. Dr. J.-S. Gao
Fax: +86-451-86609151
E-Mail: gaojins@hlju.edu.cn
[
[
[
a] School of Chemistry and Materials Science
Heilongjiang University
Harbin 150080, P. R. China
b] School of Materials and Chemistry Engineering
Heilongjiang Institute of Technology
Harbin 150050, P. R. China
c] Engineering Research Center of Pesticide of Heilongjiang Univer-
sity
Heilongjiang University
Harbin 150050, P. R. China
Scheme 1.
Z. Anorg. Allg. Chem. 2013, 639, (1), 193–196
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
193

G.-F. Hou, J.-S. Gao et al.
ARTICLE
complex, Ag (L) (NO ) (1) [L = 1,4-bis(pyridine-2-ylme-
4
4
3 4
thoxy)benzene] with tetranuclear cage structure was obtained.
In addition, it also exhibits good luminescent properties.
Results and Discussion
Complex 1 was obtained as colorless block crystals by treat-
ment of silver nitrate with 1,4-bis(pyridine-2-ylmethoxy)benz-
ene[ in methanol/H O (10 mL, V:V = 1:1) binary solvent.
31]
[32]
2
X-ray structure analysis reveals that 1 crystallizes in the tri-
¯
[33]
clinic system, space group P1.
The asymmetric unit is com-
I
posed of two Ag cations, two ligands, and two nitrate anions.
Each silver atom adopts distorted trigonal pyramidal N O en-
2
2
vironment, and binds to two oxygen atoms from two NO3– and Figure 1. Molecular structure of complex 1 with thermal ellipsoids
two nitrogen atoms of different ligands, respectively [Ag–N: presented at the 50% probability level. Symmetry code: (I) 2–x, 1–y,
2–z.
2.196(2)–2.238(2) Å, Ag–O: 2.527(2)–2.637(2) Å]. In the
structure, two cis-conformation ligands link two silver cations
to form a [2+2] macrocycle. Furthermore, four nitrate anions
Interestingly, the cage-like unit may be described with
2
2
in a η :μ mode link two adjacent macrocycles to form a tetra-
nuclear cage-like structure with the shortest Ag···Ag distance
in complex 1 about 4.245(1) Å (Table 1, Table 2, Figure 1).
2
channels of 5.493(2)ϫ2.929(1) Å along the b axis and
2
2
.929(1)ϫ5.165(2) Å along the c axis, which is not an empty
void but filled with the pyridyl ring of a neighboring molecule,
thus resulting in a pretty close and dense packing. Similar π–
π interactions with the distances of 3.39–3.80 Å and hydrogen-
bonding interactions with the distances of 2.30–2.71 Å have
Table 1. Crystallographic data for complex 1.
Empirical formula
72 4 12 20
C H64Ag N O
been reported to be found in some polymeric silver(I) com-
Formula weight
Crystal system
Space group
a /Å
b /Å
c /Å
1848.83
triclinic
P1
[34]
plexes with aromatic ligands.
Similarly, the cage-like units
¯
are cohered together by π–π stacking interactions (3.663 Å)
between the terminal pyridine rings and middle benzene rings
from different ligands to generate the 1D chain (Figure 2a). In
addition, hydrogen-bonding interactions link the adjacent
chains into a 2D structure (Figure 2b). The hydrogen bonds
are formed by the hydrogen atoms from the ligand molecules
as donors and oxygen atoms in nitrate anions as acceptors
10.489(2)
11.076(2)
16.392(3)
104.54(3)
96.35(3)
100.35(3)
1789.1(6)
1
α /°
β /°
γ /°
V /Å3
Z
(
O ···H distances are 2.711 Å).
N L
T /K
291(2)
1.716
1.162
We also carried out powder X-ray diffraction (PXRD) ex-
–3
dcalcd /mg·m
–1
periments to investigate the purity of 1. The results of PXRD
show that the peak positions and their intensities of as-synthe-
sized solids are consistent with the simulated pattern from the
single-crystal X-ray diffraction data, which proved that the
powder sample has a single phase of complex 1 (Figure 3).
Thermogravimetric analysis was carried out to determine the
thermal stability of complex 1 (Figure 4). The TG curve re-
veals that the removal of water and solvent molecules starts at
room temperature and ends to 90 °C, which shows that the
μ /mm
F(000)
928
Reflections collected
17479
Reflections unique/ observed
8101 / 6301
0.0268
R
int
Data / restraints / parameters
8101 / 6 / 487
1.044
0.0323, 0.0773
0.0462, 0.0824
2
Goodness-of-fit on F
a)
b)
R
R
1
, wR
, wR
2
[I Ͼ 2σ(I)]
1
2
(all data)
2 2 1/2
a) R
1
o
c o 2 o c o
= (Σ||F |–|F |)/Σ|F |. b) wR –F ) ] .
= [Σw(F 2 2)2/Σw(F
Table 2. Selected bond lengths /Å and angles /° of complex 1.
Ag(1)–N(3)
Ag(1)–O(10)
Ag(2)–N(1)
Ag(2)–O(10)
N(3)–Ag(1)–N(2)#1
N(2)#1–Ag(1)–O(10)
N(2)#1–Ag(1)–O(7)
N(1)–Ag(2)–N(4)#1
N(4)#1–Ag(2)–O(10)
N(4)#1–Ag(2)–O(7)
2.210(2)
2.527(2)
2.196(2)
2.538(2)
146.05(7)
91.82(8)
92.46(8)
146.32(8)
109.02(8)
88.44(8)
Ag(1)–N(2)#1
Ag(1)–O(7)
Ag(2)–N(4)#1
Ag(2)–O(7)
N(3)–Ag(1)–O(10)
N(3)–Ag(1)–O(7)
O(10)–Ag(1)–O(7)
N(1)–Ag(2)–O(10)
N(1)–Ag(2)–O(7)
O(10)–Ag(2)–O(7)
2.238(2)
2.554(2)
2.219(2)
2.637(2)
118.20(8)
112.33(8)
68.45(7)
104.37(9)
100.77(8)
67.03(7)
Symmetry codes: #1 –x+2, –y+1, –z+2
1
94
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© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 193–196

Cage-Like Complex with Bidentate Pyridine-containing Ligand and Silver Nitrate
Figure 4. TGA curve of complex 1.
contrast to the free ligand, complex 1 exhibits an increase of
emission intensity with a maximum at 411 nm. The observed
emission of complex 1 is assigned to the intraligand and inter-
ligand π–π* transitions because a similar emission is observed
for the free ligand and complex 1. In our previous studies it
was also found that four Zn, Cd, and Hg complexes con-
Figure 2. (a) 1D chain formed by the macrocycles through π···π stack-
ing interactions (dotted lines) along the a axis; (b) The 1D chains are structed by two similar ligands, 1,3-bis(pyridine-4-ylmethoxy)-
connected into the infinite 2D layer structures by the C–H···O hydro- benzene and 1,3-bis(pyridine-2-ylmethoxy)benzene, showed
gen-bonding interactions (dotted lines).
enhanced intraligand fluorescenct emission with slightly red
shift probably due to the increase of the ligands conformational
rigidity caused by the coordination of metal ions.[
14,24]
The
strong maximum emission of complex 1 is located in the blue
region, which makes it potentially useful photoactive materi-
als.
Figure 3. Powder XRD patterns for 1 (upper line: calculated from sin-
gle-crystal X-ray diffraction data; bottom line: as-synthesized solids).
Figure 5. Photoluminescence emission spectra of complex 1 (solid)
and the ligand (dotted).
sample is not completely dry. Complex 1 is thermally stable
to 210 °C, and a sharp weight-loss step happened beyond this
temperature, which corresponds to the exothermic decomposi-
tion of the complex with a weight loss of 75.14% until 820 °C
Crystallographic data (excluding structure factors) for the structure in
this paper have been deposited with the Cambridge Crystallographic
Data Centre, CCDC, 12 Union Road, Cambridge CB21EZ, UK.
Copies of the data can be obtained free of charge on quoting the de-
(calcd: 76.59%). The observed final mass remnant of 23.95%
is likely ascribed to the deposition of Ag O (calcd: 23.41%).
2
The solid-state luminescent property of 1 was investigated
at room temperature. The ligand has shown a fluorescent emis- pository number CCDC-874928 (Fax: +44-1223-336-033; E-Mail:
sion peak with a maximum intensity at 409 nm (Figure 5). In deposit@ccdc.cam.ac.uk, http://www.ccdc.cam.ac.uk).
Z. Anorg. Allg. Chem. 2013, 193–196
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
195

G.-F. Hou, J.-S. Gao et al.
ARTICLE
[
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A novel cage-like complex, Ag L (NO ) (1) [L = 1,4-
bis(pyridine-2-ylmethoxy)benzene] was synthesized and struc-
turally characterized. In the tetranuclear structure, four nitrate
4
4
3 4
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3
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with a cavity of 5.493(2)ϫ5.165(2)ϫ2.929(1) Å . Complex 1
I
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exhibits luminescent enhancement spectra tuned by Ag cations
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[
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Acknowledgements
This research was supported by the Research Fund for the Doctoral
Program of Heilongjiang Institute of Technology (2011BJ11), the Spe-
cialized Research Funds for Science and Technology Planning Project
613–615.
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[31] Synthesis of the ligand L: A mixture of 1,4-dihydroxybenzene
(
resorcinol) (1.1 g, 10 mmol), 2-chloromethylpyridine hydrochlo-
ride (3.28 g, 20 mmol), and NaOH (1.6 g, 40 mmol) in acetoni-
trile (50 mL) was stirred at reflux in a nitrogen atmosphere for
2
4 h. After cooling to room temperature, the reactant was filtered,
and the residue was washed with acetonitrile for several times.
The mixed filtrate was pouring into water under constant stirring
to give raw product, which was purified by methanol/water to
give white solid substance. Yield: 2.51 g (88% based on resor-
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[
Received: July 23, 2012
Published Online: November 26, 2012
1
96
www.zaac.wiley-vch.de
© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2013, 193–196