Blue to red fluorescent emission tuning of a cadmium coordination polymer by conjugated ligands

Article abstract of DOI:10.1002/ejic.200300230

The hydrothermal hydrolysis reactions of Cd(ClO₄)₂·(6H₂O) with 4-[2-(2-pyridyl)ethenyl]benzonitrile (2-PEBN) and 2-[2-(4-cyanophenyl)ethenyl]-8-quinolinol (2-CEQH) afforded two coordination polymers aquabis{4-[2-(2-pyridyl)ethenyl]benzoate}cadmium(II) (1) and 2-[2-(4-carboxylato-phenyl)ethenyl]-8-quinolinolate(pyridine)cadmium(II) (2), respectively. Complexes 1 and 2 display strong blue and red fluorescent emission, respectively. Both 1 and 2 have a 2-D grid framework containing a dimer as the corner unit. Crystal data for 1: monoclinic, P2₁/c, a = 15.2411(2), b = 19.8651(2), c = 15.6929(1) A, α = β = 90, γ = 96.961(1)°; for 2: monoclinic, P2₁/c, a = 11.9219(1), b = 8.9515(1), c = 18.8204(1)A, α = γ = 90.00, β = 104.372(1)°. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejic.200300230

SHORT COMMUNICATION
Blue to Red Fluorescent Emission Tuning of a Cadmium Coordination Polymer
by Conjugated Ligands
Jing Zhang,[a] Yong-Rong Xie,[a] Qiong Ye,[a] Ren-Gen Xiong,*[a] Ziling Xue,[b] and
Xiao-Zeng You*[a]
Keywords: Cadmium / Fluorescence / Coordination polymers / Crystal Engineering / Hydrothermal synthesis
The hydrothermal hydrolysis reactions of Cd(ClO4)2·(6H2O)
with 4-[2-(2-pyridyl)ethenyl]benzonitrile (2-PEBN) and 2-[2-
(4-cyanophenyl)ethenyl]-8-quinolinol (2-CEQH) afforded
grid framework containing a dimer as the corner unit. Crystal
data for 1: monoclinic, P21/c, a = 15.2411(2), b = 19.8651(2),
˚
c = 15.6929(1) A, α = β = 90, γ = 96.961(1)°; for 2: monoclinic,
˚
two
coordination
polymers
aquabis{4-[2-(2-pyridyl)-
P21/c, a = 11.9219(1), b = 8.9515(1), c = 18.8204(1)A, α = γ =
ethenyl]benzoate}cadmium(II) (1) and 2-[2-(4-carboxylato- 90.00, β = 104.372(1)°.
phenyl)ethenyl]-8-quinolinolate(pyridine)cadmium(II) (2), re-
spectively. Complexes 1 and 2 display strong blue and red
fluorescent emission, respectively. Both 1 and 2 have a 2-D
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
rational design of suitable organic ligands is still a great
challenge since the introduction of special physical proper-
ties can be achieved through conjugation of the ligand,
combined with the crystal engineering strategy and hydro-
(solvo)thermal synthesis method.[6] Furthermore, 8-quinoli-
nolate complexes of, for example, Al3ϩ and Be2ϩ and their
derivatives have also attracted much attention due to their
potential application for full-color, flat-panel displays.[7] To
this end, the hydrolysis reactions of Cd(ClO4)2·(6H2O) with
4-[2-(2-pyridyl)ethenyl]benzonitrile (2-PEBN) and 2-[2-(4-
cyanophenyl)ethenyl]-8-quinolinol (2-CEQH) under hydro-
thermal reaction conditions afford two different emitting
color fluorescent coordination polymers, aquabis{4-[2-(2-
pyridyl)ethenyl]benzoate}cadmium() (1) and 2-[2-(4-car-
boxylatophenyl)ethenyl]-8-quinolinolate(pyridine)cad-
mium() (2) (Scheme 1), respectively. Complexes 1 and 2
display strong blue and red fluorescent emission, respec-
tively. Interestingly, both 1 and 2 have a 2-D grid frame-
work containing a dimer as corner unit. To the best of our
knowledge, 1 is the first example of a double-square grid
while 2 also has an unusual herringbone-type network with
a dimer as the connecting node. Herein we report their syn-
thesis, solid-state structures and fluorescent properties.
Introduction
Full-color electroluminescent displays require three color
components — green, blue and red. Stable blue or red me-
tal-organic coordination polymers useful in electrolumi-
nescent devices are still rare and challenging to prepare.
However, organic polymers, such as poly(p-phenylene vinyl-
ene) and polythiophenes etc., permit color tuning through
changes in their length, substitution, regioregularity, and
degree of conjugation.[1] A common approach to control
the emitted color of organic materials is to append fluor-
escent chromophores to a polymeric backbone or to blend
dyes into inert polymeric matrices.[2] Similarly, the emission
wavelength of most metal-organic complexes can be tuned
or changed by adjusting the length or conjugation of ligand
since fluorescent emission is mostly dominated by the coor-
dinated ligand transition.[3,4] In addition, metal-organic flu-
orescent coordination polymers have many more advan-
tages — such as high thermal stability, good mechanical
properties and relatively high emitting intensity — over
pure organic materials. These coordination polymers have
thus attracted much attention recently.[5] The synthesis and
[a]
Coordination Chemistry Institute, The State Key Laboratory of
Coordination Chemistry, Nanjing University,
210093 Nanjing, P. R. China
Results and Discussion
Fax: (internat.) ϩ86-25/331-4502
or (internat.) ϩ86-25/331-7761
E-mail: xiongrg@netra.nju.edu.cn
The coordination polymers 1 and 2 were prepared under
hydrothermal reaction conditions from Cd(ClO4)2·6H2O
[b]
Department of Chemistry, University of Tennessee,
Knoxville, Tennessee, 37996
2572
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejic.200300230
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577

Fluorescent Emission Tuning of a Cadmium Coordination Polymer
SHORT COMMUNICATION
Scheme 1
and 2-PEBN or 2-CEQH respectively. In these two reac-
tions, the cyano groups were hydrolyzed into carboxylates
to give 4-[2-(2-pyridyl)ethenyl]benzoate (2-PEBA) in 1 and
2-[2-(4-carboxylatephenyl)ethenyl]-8-quinolinolate
(2-
CEQA) in 2. The presence of the carboxylates was con-
firmed by the presence of two very strong peaks at 1600
and 1380 cmϪ1 for 1 and 1582 and 1405 cmϪ1 for 2 in the
IR spectra. No peak around 2100 cmϪ1 was found, suggest-
ing that the cyano groups are no longer present in 1 and 2.
TGA analysis showed an onset temperature for 1 at 300 °C
with a weight loss of 1.77%; 1 decomposes beyond 350 °C.
This weight loss at 300 °C corresponds to the removal of
one water molecule per formula unit (calcd. 1.58%) in 1.
An onset temperature of 280 °C was observed for 2.
The two-dimensional polymeric structures of 1 and 2
were revealed by X-ray single-crystal diffraction. The local
coordination environment around the Cd center in 1 can
best be described as a slightly distorted octahedron (Fig-
ure 1) in which each Cd center coordinates to two N atoms,
one O atom from the bridging water and three O atoms
from three different 2-PEBA ligands. Thus there are two
kinds of 2-PEBA ligands, with one acting as a tridentate
spacer to link three Cd centers and the other as a bidentate
spacer to bridge two Cd centers, resulting in the formation
of a 2-D rectangular grid network (Figure 2a). A simplified
network representation (Figure 2b) clearly shows that each
Figure 1. The asymmetric unit representation of 1 showing the lo-
˚
cal geometry around the Cd center; key bond lengths (A):
Cd1ϪO1A 2.213(2), Cd1ϪO3 2.253(2), Cd1ϪO8A 2.356(2),
Cd1ϪO9 2.420(2), Cd1ϪN1 2.465(3), Cd1ϪN2A, 2.375(3),
net shares eight 2-PEBA ligands as a rhombic side and four Cd2ϪO2A 2.389(3), Cd1ϪO5A 2.226(3), Cd1ϪO7A 2.211(2),
dimers as a connecting node. Thus, 1 can be considered as
Cd1ϪO9 2.413(2), Cd1ϪN3 2.374(3), Cd2ϪN4 2.461(3)
a double-rectangular grid network with a dimer as con-
necting node. To the best of our knowledge, 1 is the first
such network example in supramolecular motifs.[8,9]
Like 1, the local coordination geometry around each Cd ters, resulting in the formation of a 2-D rectangular grid
center in 2 can also be described as a slightly distorted octa- network (Figure 4a). A simplified network representation of
hedron (Figure 3), in which each Cd center coordinates to 2 (Figure 4b) clearly demonstrates that each rectangular
two O atoms from a chelating, bridging 2-CEQA ligand and grid shares four 2-CEQA ligands as a rhombic side and four
to two O atoms from the chelating carboxylate group of a dimers as connecting node resulting in the formation of a
different 2-CEQA ligand; the coordination sphere is com- 2-D herringbone-type network. The structural feature in 2
pleted by two N atoms, one from the chelating, bridging is unusual as most supramolecular motifs with a herring-
quinolinolate and one from pyridine. Thus, each 2-CEQA bone net contain only one metal center as the connecting
ligand acts as a pentadentate spacer to bridge three Cd cen- node.[8,9]
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2573

J. Zhang, Y.-R. Xie, Q. Ye, R.-G. Xiong, Z. Xue, X.-Z. You
SHORT COMMUNICATION
Figure 2. (a) 2-D grid network representation of 1; (b) a simplified network representation of 1 in which the straight line is the 4-[2-(2-
pyridyl)ethenyl]benzene group
The most important feature in the structures of 1 and 2 as Zn(Norf)2·4(H2O) (Norf ϭ norfloxacin).[3] The solid-
is that both have a 2-D condensed polymeric structure; this state diffuse reflectance UV/Vis spectra of 1 and 2 show
unique structure perhaps leads to significant enhancement two intense bands at 381 and 239 nm for 1 and 337 and
of the fluorescent intensities, which are approximately two 220 nm for 2, which are assigned to intraligand π-π*
to three times larger than those of free 2-PEBA and 2- transitions of 2-PEBA (388 and 246 nm) and 2-CEQA (338
CEQA. These enhancements are perhaps a result of coordi- and 215 nm). These bands match well with those in the
nation of those ligands to CdII, which increases the ligands’ excitation spectra of 1, 2 and the free ligands (λmax
ϭ
conformational rigidity, thereby reducing the non-radiative 391 nm for 2-PEBA and λmax ϭ 348 nm for 2-CEQA). The
1
decay of the intraligand (π-π*) excited state. Similar en- emissions of 1 [λmax ϭ 418 nm, τ (lifetime) ϭ 1.8 ns, Φem
hancement of the intraligand fluorescence has also been re- (quantum efficiency) ഠ 0.34; the short lifetime suggests that
ported for [Zn(terpyridine)2]2ϩ and [Zn(L)2(OAc)2] (L ϭ luminescence should be assigned to fluorescence] and 2
[10]
N,NЈ-bisbenzyl-2,7-diamino-1,8-naphthyridine)
as well (λmax ϭ 600 nm, τ ϭ 1.9 ns, Φem ഠ 0.46; Figure 5), are
2574
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577

Fluorescent Emission Tuning of a Cadmium Coordination Polymer
SHORT COMMUNICATION
be tuned by ligand conjugation. Due to the low solubility
of compounds 1 and 2 in common solvents such as water,
ethanol, benzene, chloroform, ethyl acetate, acetone and
acetonitrile, a film can be prepared by the spin-coating
method.
In conclusion, through tuning of ligand length and con-
jugation, complexes 1 and 2 display a strong fluorescent
emission at different wavelengths, and may be used as excel-
lent advanced materials for blue- or red-light-emitting diode
devices. These polymeric structures show high thermal sta-
bility and their low solubility in most common solvents me-
ans that they could be used in LED devices.
Experimental Section
Synthesis of Cd(2-PEB)2·(H2O) (1): Hydrothermal treatment of
Cd(ClO4)2·6H2O (1.0 mmol), PEBN (2.0 mmol), pyridine (0.6 mL)
and water (0.6 mL) for 2 days at 120 °C yielded pale-yellow, crystal-
line blocks of 1 with only one pure phase. The yield of 1 was about
(0.313 g) 55% based on PEBN. C56H40Cd2N4O9 (1137.8): calcd. C
59.07, H 3.52, N 4.92; found C, 59.07, H 3.45, N 5.03. IR (KBr):
ν˜ ϭ 3400 cmϪ1 (br., w), 3008 (w), 1600 (s), 1551 (m), 1480 (m),
1420 (w), 1380 (s), 1180 (w), 1160 (m), 1010 (w), 960 (m), 850 (w),
793 (m), 742 (w), 700 (w), 681 (w), 640 (w), 532 (w), 434 (w).
Figure 3. The asymmetric unit representation of 2 showing the lo-
˚
cal geometry around the Cd center; key bond lengths (A): Cd1ϪO1
2.253(2), Cd1ϪO2B 2.369(3), Cd1ϪO3B 2.356(3), Cd1ϪN1
2.317(3), Cd1ϪN2 2.367(3)
Synthesis of Cd(2-CEQA)(Py) (2): The procedure with 2-CEQB was
similar to that for 1. Yellow block crystals (one phase) of 2 were
harvested in 0.312 g (65%) yield based on 2-CEQB. C23H16CdN2O3
(480.8): calcd. C 57.41, H 3.33, N 5.82; found C, 57.60, H 3.42, N
5.90. IR (KBr): ν˜ ϭ 3424 cmϪ1 (br., w), 1583 (s), 1532 (s), 1504
(w), 1445 (s), 1405 (s), 1371 (sh, w), 1278 (w), 1101 (m), 1035 (w),
1010 (w), 958(w), 833 (w), 779 (w), 739 (w), 703 (w), 616 (w), 417
(w).
Table 1. Crystal data and structure refinement for 1 and 2
1
2
Empirical formula
Mol. wt.
T (K)
C56H40N4O9Cd2
1137.72
293(2)
C23H16N2O3Cd
480.78
293(2)
Crystal system
Space group
monoclinic
P21/c
15.2411(2)
19.865(2)
15.6929(1)
90.00
96.961(1)
90.00
4716.25(8)
4
1.602
9.67
2288
0.946
monoclinic
P21/c
11.9219(1)
8.9515(1)
18.8204(1)
90.00
104.372(1)
90.00
1945.64(3)
4
1.641
11.490
960
0.944
X-ray Crystallographic Determinations of 1 and 2: Data were col-
lected at room temperature from epoxy-coated crystals mounted
on a glass fiber. All measurements were made on a CCD Smart
diffractometer with graphite-monochromated Mo-Kα radiation
˚
a, A
˚
b, A
˚
c, A
α, Deg
β, Deg
γ, Deg
˚
(λ ϭ 0.71073 A). Empirical absorption corrections were applied in
each case. The relevant crystallographic data are presented in
Table 1. The structure was solved by direct methods using the pro-
gram SHELXTL (Sheldrick, 1997).[11] All the non-hydrogen atoms
were located from the trial structure and then refined aniso-
tropically with SHELXTL using full-matrix least-squares pro-
cedure. The hydrogen atom positions were fixed geometrically at
calculated distances and allowed to ride on the parent carbon
atoms. The final difference Fourier map was found to be featureless.
CCDC-167840 (1) and CCDC-167841 (2) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
[or from the Cambridge Crystallographic Data Centre, 12, Union
Road, Cambridge CB2 1EZ, UK; Fax: (internat.) ϩ44-1223/336-
033; E-mail: deposit@ccdc.cam.ac.uk].
3
˚
V, A
Z
ρ (cald), g/cm3
µ (Mo-Kα), cmϪ1
F(000)
GOF
R1, wR2 [I Ͼ 2σ(I)][a]
(all data)
0.0449, 0.0970
0.0790, 0.1062
0.0426, 0.1004
0.0566, 0.1058
[a]
2
2 2
2 2 1/2
R1 ϭ Σ||Fo| Ϫ |Fc||/Σ|Fo|. wR2 ϭ [Σw(Fo Ϫ Fc ) /Σw(Fo ) ]
.
neither MLCT (metal-to-ligand charge transfer) nor LMCT
(ligand-to-metal charge transfer) in nature, and can be ten-
tatively assigned to the intraligand fluorescent emission
since a similar weak emission (2-PEBA for λmax ϭ 420 nm,
τ ϭ 1.0 ns, Φem ഠ 0.11) and (2-CEQA for λmax ϭ 604 nm,
τ ϭ 1.0 ns, Φem ഠ 0.16) is also observed for the free ligands.
Acknowledgments
This work was funded by The Major State Basic Research Develop-
ment Program (Grant No. G2000077500), the National Natural
Science Foundation of China, and National Science Foundation of
Thus, the emitting color of a Cd coordination polymer can the U.S.A.
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2575

J. Zhang, Y.-R. Xie, Q. Ye, R.-G. Xiong, Z. Xue, X.-Z. You
SHORT COMMUNICATION
Figure 4. (a) 2-D grid network representation of 2; (b) a simplified network representation of 1 in which the straight line is the 2-[2-(4-
carboxylatephenyl)ethenyl]quinoline group
[1] [1a]
H. S. Joshi, R. Jamshidi, Y. Tor, Angew. Chem. Int. Ed.
[1b]
[1c]
1999, 38, 2722.
S. A. Jenekhe, Adv. Mater. 1995, 7, 309.
F. Hide, M. A. B. Diaz-Garcia, J. Schartz, A. J. Heeger, Acc.
[1d]
Chem. Res. 1997, 30, 430.
A. Kraf, A. C. Grimsdale, A. B.
Holmes, Angew. Chem. Int. Ed. 1998, 37, 402. [1e] R. D. McCul-
[1f]
lough, Adv. Mater. 1998, 10, 93.
T. Noda, H. Ogawa, N.
Noma, Y. Shirota, Adv. Mater. 1997, 9, 720.
[2]
[2a] M. Berggren, O. Inganas, G. Gustafsson, J. Rasmusson, M.
R. Andersson, T. Hjertberg, O. Wennerstrom, Nature 1994,
372, 444. [2b] M. Aguiar, F. E. Karasz, L. Akcelrud, Macromol-
ecules 1995, 28, 4598. [2c] S.-J. Chung, J.-I. Jin, K.-K. Kim, Adv.
Mater. 1997, 9, 551.
Stumpflen, H. Wendorff, Adv. Mater. 1997, 9, 219.
Dottinger, M. Hohloch, J. L. Segura, E. Steinhuber, M. Han-
[2d]
T. Christ, A. Greiner, R. V. Sander, J.
[2e]
S. E.
[2f]
ack, A. Tompert, D. Oelkrug, Adv. Mater. 1997, 9, 233.
M. Girotto, M.-A. De Paoli, Adv. Mater. 1998, 10, 790.
E.
D.
[2g]
E. Biller, H. Baumgartel, Angew. Chem. Int. Ed. 1998, 37, 646.
[3] [3a]
R.-G. Xiong, J.-L. Zuo, X.-Z. You, B. F. Abrahams, Z.-P.
[3b]
Bai, C.-M. Che, H.-K. Fun, Chem. Commun. 2000, 2061.
R.-G. Xiong, J.-L. Zuo, X.-Z. You, H.-K. Fun, S. S. S. Raj,
Organometallics 2000, 19, 4183. [3c] H.-K. Fun, S. S. S. Raj, R.-
Figure 5. Fluorescence spectra of 1 and 2 in the solid state at
room temperature
2576
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577

Fluorescent Emission Tuning of a Cadmium Coordination Polymer
SHORT COMMUNICATION
G. Xiong, J.-L. Zuo, Z. Yu, X.-Z. You, J. Chem. Soc., Dalton
S. Minakoshi, A. Asami, K. Seki, S. Kitagawa, Chem. Mater.
[3d]
[8f]
Trans. 1998, 1915.
J. Zhang, W. Lin, Z.-F. Chen, R.-G.
Xiong, B. F. Abrahams, H.-K. Fun, J. Chem. Soc., Dalton
2000, 12, 1288.
J. K. Bera, K. R. Dunbar, Angew. Chem.
Int. Ed. 2002, 41, 4453. [8g] Y. H. Kiang, G. B. Gardner, S. Lee,
[3e]
[8h]
Trans. 2001, 1804.
Z.-F. Chen, R.-G. Xiong, J. Zhang, X.-
Z.-T. Xu, J. Am. Chem. Soc. 2000, 122, 6871.
Angew. Chem. Int. Ed. Engl. 1997, 36, 1431.
[9] [9a]
C. Janiak,
T. Chen, Z.-L. Xue, X.-Z. You, Inorg. Chem. 2001, 40, 4075.
[3f]
R.-X. Yuan, R.-G. Xiong, Z.-F. Chen, X.-Z. You, S.-M.
M. J. Zaworotko, Chem. Soc. Rev. 1994, 23, 284 and refer-
[9b]
Peng, G.-H. Lee, Inorg. Chem. Commun. 2001, 4, 430.
ences therein.
Chem. Int. Ed. 1999, 38, 1018 and references therein.
Cotton, L. M. Daniels, C. Lin, C. A. Murillo, J. Am. Chem.
L. R. MacGillivrary, J. L. Atwood, Angew.
[4a] D. M. Ciurtin, N. G. Pschirer, M. D. Smith, U. H. F. Bunz,
F. A.
[4]
[9c]
H.-C. zur Loye, Chem. Mater. 2001, 13, 2743 and references
[4b]
[9d]
therein.
J. E. Fiscus, S. Shotwell, R. C. Layland, M. D.
Soc. 1999, 121, 4538.
O. M. Yaghi, H. Li, C. Davis, D.
Smith, H.-C. zur Loye, U. H. F. Bunz, Chem. Commun. 2001,
24, 2674. [4c] O. Teichert, W. S. Sheldrick, Z. Anorg. Allg. Chem.
1999, 625, 1860.
Richardson, T. L. Groy, Acc. Chem. Res. 1998, 31, 474 and
[9e]
references therein.
D. Hagrman, C. Zubieta, D. J. Rose, J.
Zubieta, R. C. Haushalter, Angew. Chem. Int. Ed. Engl. 1997,
[5] [5a]
[9f]
K. Y. Ho, W. Y Yu, K. K. Cheung, C. M. Che, Chem.
36, 873.
G. B. Gardner, D. Venkataraman, J. S. Moore, S.
[5b]
Commun. 1998, 2101.
C. M. Che, J. Chem. Soc., Dalton Trans. 1999, 1581.
K. Y. Ho, W. Y. Yu, K. K. Cheung,
Lee, Nature 1995, 374, 792. [9g] J. Lu, C. Yu, T. Niu, T. Paliwala,
[5c]
Y. G.
G. Gisci, F. Somosa, A. J. Jacobson, Inorg. Chem. 1998, 37,
[9h]
Ma, H. Y. Chao, Y. Wu, S. T. Lee, W. Y. Yu, C. M. Che, Chem.
Commun. 1998, 2491.
4637.
H. Miyasaka, C. S. Campos-Fernandez, R. Clerac,
K. R. Dunbar, Angew. Chem. Int. Ed. 2000, 39, 3831. [9i] R. W.
Saalfrank, H. Maid, N. Mooren, F. Hampel, Angew. Chem. Int.
Ed. 2001, 41, 304.
[6] [6a]
O. R. Evans, R.-G. Xiong, Z. Wang, G. K. Wong, W. Lin,
[6b]
Angew. Chem. Int. Ed. 1999, 38, 536.
W. Lin, O. R. Evans,
R.-G. Xiong, Z. Wang, J. Am. Chem. Soc. 1998, 120, 13272. [6c]
W. Lin, Z. Wang, L. Ma, J. Am. Chem. Soc. 1999, 121, 11249.
N. W. Alcock, P. R. Barker, J. M. Haider, M. J. Hannon,
C. L. Painting, Z. Pikramenou, E. A. Plummer, K. Rissanen,
P. Saarenketo, J. Chem. Soc., Dalton Trans. 2000, 1447. [10b] C.-
[10] [10a]
[7] [7a]
C. W. Tang, S. A. Van Slyke, Appl. Phys. Lett. 1987, 51,
[7b]
913.
Y. Hamada, T. Sano, M. Fujita, T. Fujii, Y. Nishino,
M. Che, C.-W. Wan, K.-Y. Ho, Z.-Y. Zhou, New J. Chem. 2001,
[10c]
K. Shibata, Chem. Lett. 1993, 905.
25, 62.
X. Xue, X.-S. Wang, L.-Z. Wang, R.-G. Xiong, B.
[8] [8a]
J.-M. Lehn, Supramolecular Chemistry; VCH Publishers:
F. Abrahams, X.-Z. You, Z. Xue, C.-M. Che, Inorg. Chem.
2002, 41, 6544. [10d] R. G. Xiong, X. Xue, H. Zhao, X.-Z. You,
B. F. Abrahams, Z. Xue, Angew. Chem. Int. Ed. 2002, 41, 3800.
G. M. Sheldrick, (1997). SHELXTL V5.1 Software Reference
Manual, Bruker AXS, Inc., Madison, Wisconsin, USA.
Received April 22, 2003
[8b]
New York, 1995.
Int. Ed. 1998, 37, 1460 and references therein.
S. R. Batten, R. Robson, Angew. Chem.
[8c]
S. Leininger,
[11]
B. Olenyuk, P. J. Stang, Chem. Rev. 2000, 100, 853 and refer-
ences therein. [8d] M. Fujita, Chem. Soc. Rev. 1998, 27, 417 and
[8e]
references therein.
M. Kondo, M. Shimamura, S.-I. Noro,
Eur. J. Inorg. Chem. 2003, 2572Ϫ2577
www.eurjic.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2577