Periodic mesoporous organosilica derivatives bearing a high density of metal complexes on pore surfaces

Article abstract of DOI:10.1002/anie.201104063

Periodic mesoporous organosilica derivatives (PMOs) that bear a high density of Ru and Ir complexes on pore walls were synthesized using a unique two-step approach: 1) synthesis of PMO containing phenylpyridine bridging groups in the pore walls, and 2) po

Full text of DOI:10.1002/anie.201104063

DOI: 10.1002/anie.201104063
Organosilica Derivatives
Periodic Mesoporous Organosilica Derivatives Bearing a High Density
of Metal Complexes on Pore Surfaces
Minoru Waki, Norihiro Mizoshita, Takao Tani, and Shinji Inagaki*
Periodic mesoporous organosilicas (PMOs) synthesized from
alkoxysilane precursors bridged with organic moieties, R[Si-
(OR’)3]n, n ꢀ 2, R = organic group, R’ = CH3, C2H5, etc. by
surfactant-directed self-assembly are a new class of functional
materials that have well-defined nanoporous structures and
highly functional organic groups in the silica walls.[1] It is
preferable to incorporate organic groups in the pore walls
rather than to graft them on the wall surfaces because in the
former case the organic groups offer little resistance to the
diffusion of molecules and ions in the mesochannels and are
quite resistant to leaching. Many PMOs containing bridging
organic groups (R) that range from aliphatic and aromatic
hydrocarbons to heterocycles and metal complexes have been
reported.[2,3] Incorporating metal complexes into PMO frame-
works is particularly important because metal
plexes have been attracting interest because of their photo-
physical properties and they have been widely utilized for
dye-sensitized solar cells,[8] organic light emitting devices,[9]
and photocatalysts.[10] Typical ligands for the d6 metal com-
plexes are bipyridine and 2-phenylpyridine (PPy).[11] Thus, the
synthesis of PMO containing such chelating ligands in the
framework is important for the formation of highly functional
d6 metal complexes on the pore surface.
Herein, we report the synthesis of a novel PMO contain-
ing PPy moieties in the PMO framework (PPy–PMO) and the
successful formation of a high density of Ru or Ir polypyridine
complexes on the pore surfaces (Scheme 1). The PPy ligands
in the pore walls of the obtained PPy–PMOs exhibit
molecular-scale periodicity, in which their molecular axes
complexes possess unique features such as cata-
lytic activity, luminescence emission, redox prop-
erties, and excited-state reactivity.[4]
PMOs with metal complexes are usually
prepared by co-condensation of a metal-com-
plex-bridged alkoxysilane precursor and a large
amount (typically over 90%) of tetraethoxysi-
lane. This is due to general difficulties in pro-
ducing PMOs from just a precursor with a bulky
metal complex because of weak interaction
between hydrolyzed precursors and surfactants.[5]
An alternative approach is to form metal com-
plexes on a pore surface after synthesis by using
bridging organic groups in the framework as
Scheme 1. Two-step synthesis of periodic mesoporous organosilicas (PMOs) with a
high density of Ru and Ir polypyridine complexes on their pore surfaces.
metal ligands. Matsuoka and co-workers at-
tached the organometallic fragments {Cr(CO)3}
and {Mo(CO)3} to the phenyl ring of phenyl-
ene(Ph)-bridged PMO.[6] Recently, Polarz and
co-workers reported the coordination of transition-metal
cations to Ph–PMOs functionalized with carboxylic, dithio-
carboxylic, acetylacetonate, and amine groups.[7] This
approach has the advantage that bulky metal complexes can
be densely and selectively integrated on the pore surface of
highly ordered PMOs. However, these metal complexes
attached to a PMO framework have limited functionalities
mainly because of the poor ligand ability of these PMOs.
Recently, octahedral d6 metal complexes such as polypyr-
idine-coordinated ruthenium (RuII) and iridium (IrIII) com-
are aligned in parallel to the channel direction, with a high
À
degree of freedom to rotate about the Si C axis. The unique
environment of the PPy ligands in the walls was found to
realize efficient cyclometalation to form [RuII(bpy)2(ppy)]+
or [IrIII(ppy)3] complexes by a post-synthesis treatment of
PPy–PMO with metal complex precursors. PMOs with a high
density of metal complexes on the pore surface have great
potential in applications such as for efficient heterogeneous
catalysts and sensors because the metal complexes hardly
hinder the facile diffusion of molecules and ions in the
mesochannels compared with conventional metal-complex-
functionalized mesoporous silicas with organic linkers.
[*] Dr. M. Waki, Dr. N. Mizoshita, Dr. T. Tani, Dr. S. Inagaki
Toyota Central R&D Labs., Inc., CREST/JST
Nagakute, Aichi 480-1192 (Japan)
The PPy-bridged alkoxysilane precursor, 2-(4-triethoxysi-
lylphenyl)-5-triethoxysilylpyridine 1, was synthesized from
2,5-dibromopyridine and 4-(trimethylsilyl)phenylboronic acid
by a four-step reaction. The detailed procedure is described in
the Supporting Information. PPy–PMO powder was obtained
E-mail: inagaki@mosk.tytlabs.co.jp
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.201104063.
Angew. Chem. Int. Ed. 2011, 50, 11667 –11671
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
11667

Communications
by basic hydrolysis and polycondensation of the precursor in
adsorption–desorption isotherms were type IV isotherms,
typical of mesoporous materials (Figure 1b). The Brunauer–
Emmett–Teller (BET) surface area was 649 m2 gÀ1, the pore
volume was 0.39 cm3 gÀ1, and the DFT pore diameter was
3.7 nm. The pore wall thickness was estimated to be 1.7 nm
from the structural parameters by assuming 2D hexagonal
symmetry; this thickness corresponds to approximately four
layers of the PPy moieties.
the presence of a cationic surfactant, octadecyltrimethylam-
monium chloride (C18TMACl; Scheme 1). The surfactant was
removed from the as-synthesized PPy–PMO by solvent
extraction using a mixture of aqueous HCl and ethanol. The
complete removal of the surfactant was confirmed by infrared
absorption (IR) measurements (Figure S1 in the Supporting
Information).
The X-ray diffraction (XRD) profile of the as-made PPy–
PMO (Figure 1a, gray) contains a signal at a low scattering
angle of 2q ꢁ 1.888 (d spacing of 4.7 nm), which suggests the
The solid-state 29Si magic angle spinning (MAS) NMR
spectrum of PPy–PMO showed two resonances at À71.3 and
À80.9 ppm, which were assigned to T2 and T3 [Tn:
SiC(OH)3Àn(OSi)n] species, respectively, but no signals
around À100 ppm because of Qn [Si(OH)4Àn(OSi)n] species
(Figure S2A in the Supporting Information). The 13C cross-
polarization MAS NMR spectrum showed four resonances
at 117, 125, 133, and 139 ppm, which are primarily in
consistency with those of the precursor (Figure S2B in the
Supporting Information). The IR spectrum showed absorp-
=
=
tion bands assignable to C C and C N of the PPy group
À1
À1
À1
À
À
(1352–1585 cm ), Si C (1149 cm ), and Si O (1030 cm
Figure S1 in the Supporting Information). These results
;
À
indicate that both the Si C bonds and the PPy moieties are
preserved during synthesis and extraction.
Cyclometalation of the PPy ligands in PPy–PMO was
performed by heating PPy–PMO powder in an ethylene
glycol solution of [Ru(bpy)2Cl2]·2H2O or a glycerol solu-
tion of [Ir(ppy)2Cl]2 in the presence of K2CO3 at 1208C for
24 h and subsequent washing with solvents to remove any
unreacted precursor (Scheme 1). The obtained powders are
denoted Ru–PPy–PMO and Ir–PPy–PMO, respectively.
UV/Vis spectra of Ru–PPy–PMO showed new absorp-
tion bands at 372, 416, 497, and 550 nm in addition to the
original band at 305 nm caused by PPy–PMO (Figure 2a,
black). The new bands were assignable to metal-to-ligand
charge transfer (MLCT) transitions, which have been
previously observed for [RuII(bpy)2(ppy)]+ complexes.[13]
For further confirmation, the UV/Vis spectrum was com-
pared to that of a model complex, [RuII(bpy)2(TMS-ppy)]+,
in which the PPy ligand was trimethylsilylated (TMS) at the
para-positions, similar to the Ru complexes in Ru–PPy–PMO
(Figure 2b); the spectra are similar to each other. In addition,
the UV/Vis spectrum differs from that of the precursor,
[Ru(bpy)2Cl2]·2H2O, which contains only two absorption
bands at 379 and 557 nm (Figure S3 in the Supporting
Information). This result suggests that the precursor under-
went a reaction during treatment with PPy–PMO. These
results indicate the successful formation of the [RuII(bpy)2-
(ppy)]+ complex on the PMO surface through cyclometala-
tion of the PPy ligands in the framework.
Figure 1. a) XRD profiles, b) nitrogen adsorption isotherms, c) transmis-
sion electron microscopy image, and d) structural model of PPy-PMO.
Insets in (b) and (c) show DFT pore size distribution and an enlarged
TEM image, respectively.
existence of a mesoscopically ordered structure. The XRD
pattern also contained five other signals at medium scattering
angles (2q = 5–408) with d spacings of 1.17, 0.59, 0.39, 0.30,
and 0.23 nm. These signals are assigned to a molecular scale
periodicity of 1.17 nm and its higher-order reflections. The
low- and medium-angle reflections remained after extracting
the surfactant (Figure 1a, black). TEM observations revealed
a bundle structure of one-dimensional channels with a
periodicity of 4–5 nm and many lattice fringes with an interval
of 1.1–1.2 nm running perpendicular to the mesochannels
(Figure 1c). These results indicate that the PPy moieties in
the walls are aligned with their molecular axes parallel to the
channel direction to form alternating organic and silica belt-
like layers with an interval of 1.17 nm (Figure 1d); this
structure is similar to those of crystal-like PMOs with
aromatic moieties such as benzene, biphenyl, divinylbenzene,
napthalene, and divinylpyridine.[12] However, PPy–PMO is
the first example of crystal-like PMO possessing a chelating
ligand in the framework. The successful formation of crystal-
like PPy–PMO enables us to fabricate highly functional d6
metal complexes on the periodic pore walls. The nitrogen
On the other hand, Ir–PPy–PMO exhibited broad absorp-
tion bands at longer wavelengths in addition to the original
band at 305 nm (Figure 2c). The band at 380 nm corresponds
to the 1MLCT transition and the shoulder around 480 nm can
3
be assigned to the MLCT transition according to previous
reports.[14] Ir–PPy–PMO showed a strong emission (phos-
phorescence) at 550 nm with a luminescence quantum yield of
0.03 (Figure 2d). The lifetime measurement indicated that the
emission decayed with two time constants of 250 ns and 1.0 ms,
respectively (Figure S4 in the Supporting Information). These
11668 www.angewandte.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2011, 50, 11667 –11671

Similarly, Ir/PPy = 0.02 was obtained for Ir–PPy–PMO (Fig-
ure S9 in the Supporting Information). Since the pore walls of
PPy–PMO are composed of four PPy layers and only the
outer two PPy layers (denoted by PPy*) are available for
cyclometalation, Ru/PPy* and Ir/PPy* are 0.2 and 0.04,
respectively. The lower amount of Ir than Ru may be due to
the lower reactivity of [Ir(ppy)2Cl]2 with PPy ligands than
[Ru(bpy)2Cl2]·2H2O.[11b]
Figure 3a and b, respectively, show computer graphic
images of the pore surface and the cross-section of the
mesochannels for Ru–PPy–PMO, assuming that Ru/PPy* =
Figure 2. a) UV/Vis diffuse reflectance spectra of Ru–PPy–PMO (black)
and PPy–PMO (gray) are depicted with Kubelka–Munk absorption
coefficient (K/S); b) UV/Vis absorption spectrum of the model com-
pound [Ru(bpy)2(TMS-ppy)]+ in CH2Cl2 (1.0ꢀ10À5 m); c) UV/Vis diffuse
reflectance spectra of Ir–PPy–PMO (black) and PPy–PMO (gray);
d) photoluminescence spectra of Ir–PPy–PMO excited at 300 and
380 nm (black) and of PPy–PMO excited at 300 nm (gray).
optical properties, such as the broad MLCT band shapes, the
low quantum yield, and the short emission lifetime are typical
for a meridional isomer of an [IrIII(ppy)3] complex,[15] and are
suggestive of the successful formation of [IrIII(ppy)3] on the
pore walls. The formation of the meridional isomer is
reasonable because it is usually formed in low-temperature
cyclometalation (< 1408C).[16]
Figure 3. Computer graphic images of Ru–PPy–PMO; a) Ru complexes
[RuII(bpy)2(ppy)]+ on pore surfaces of PPy–PMO with Ru/PPy*=0.2;
Ru complex and PPy–PMO are shown as CPK and ball-and-stick
models; b) cross-section of a mesochannel in Ru–PPy–PMO; c) sche-
matic image for light-harvesting of Ir–PPy–PMO.
TEM observations confirm the preservation of the meso-
and molecular-scale periodicities for both Ru–PPy–PMO and
Ir–PPy–PMO, although XRD measurements indicate some
reduction in the mesoscale structural order (Figure S5 and S6
in the Supporting Information). Nitrogen adsorption experi-
ments reveal that the surface area and the pore volume of
PPy–PMO decrease to 462–564 m2 gÀ1 and 0.26–0.31 cm3 gÀ1,
respectively, during complex formation on the pore surface
0.2 and that the Ru complexes are homogeneously distrib-
uted. These figures indicate that the Ru complexes are
densely accumulated on the pore surface and cause little pore
blockage that would hinder diffusion of molecules and ions in
the mesochannels. A molecular mechanics simulation of PPy–
PMO reveals that the average PPy–PPy distance in the silicate
layers is approximately 0.44 nm (Figure 3a), which is longer
than the usual p–p stacking distance of aromatic compounds.
Thus, the PPy moieties have a high degree of freedom to
(Figure S5 and S6 in the Supporting Information). 29Si and 13
C
MAS NMR and IR spectra indicate the preservation of both
À
Si C bonds and PPy moieties during cyclometalation (Fig-
ure S7 in the Supporting Information).
À
The loaded amounts of Ru and Ir in Ru–PPy–PMO and
Ir–PPy–PMO, respectively, were carefully determined by
energy-dispersive X-ray spectroscopy (EDS), which was
performed using an EDS attachment to the TEM system.
EDS elemental analysis of many different areas on the Ru–
PPy–PMO sample with various spot sizes (40–2500 nm) gave
an atomic ratio Ru/Si of 0.05 (thus, Ru/PPy = 0.1) in almost all
areas and Ru/Si = 0.04 or 0.06 in a few areas, which suggests
that Ru was almost homogeneously distributed in the
mesochannels (Figure S8 in the Supporting Information).
rotate about the Si C axis, as pointed out by Sozzani and co-
workers in their study of molecular rotors in Ph- and
biphenyl-PMOs.[17] This high degree of rotational freedom
of the PPy ligands may permit efficient cyclometalation with
Ru complexes despite the PPy moieties being fixed in the
rigid silicate framework.
Ir–PPy–PMO exhibited unique light-harvesting-antenna
properties. The emission at 550 nm from [IrIII(ppy)3] was
greater for excitation at 300 nm than at 380 nm, as shown in
Figure 2c. This result is thought to be caused by the more
Angew. Chem. Int. Ed. 2011, 50, 11667 –11671
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 11669

Communications
at 77 K on silica, cylindrical pores, nonlinear density functional theory
(NLDFT) equilibrium model). Pore volumes were estimated by the t-
plot method. TEM observations were performed using a Jeol JEM-
EX2000 operating at 200 kV. IR spectra were collected on a Thermo
Fisher Scientific Nicolet Avatar-360 FT-IR spectrometer using an
attenuated total reflection (ATR) attachment. UV/Vis absorption
and fluorescence emission spectra were obtained using Jasco V-670
and FP-6500 spectrometers, respectively.
Time-resolved phosphorescence measurements were performed
using nanosecond 355 nm laser pulses by third-harmonic generation
(THG) of a Nd3+:YAG laser (Continuum, NY-81) for the excitation
light source. The phosphorescence from the sample was focused on
the slit of a monochromator (Ritsu, MC-10N). The output of the
monochromator was monitored using an avalanche photodiode
(Hamamatsu Photonics, S5343). The signal from the detector was
recorded on a digital oscilloscope (Tektronix, TDS3032B). The entire
system was controlled with a personal computer through a GP–IB
interface. The observed decay curves were analyzed using commer-
cially available software (Wave Metrics, IGOR Pro).
Ru–PPy–PMO: PPy–PMO (0.15 g) was added to a mixture of
K2CO3 (0.62 g, 4.5 mmol), [Ru(bpy)2Cl2]·2H2O (0.23 g, 0.45 mmol),
and ethylene glycol (15 mL) under an argon atmosphere. The
suspension was stirred and heated at 1208C for 24 h. The resulting
precipitate was filtered and washed with DMSO and EtOH to remove
any unreacted [Ru(bpy)2Cl2]·2H2O, affording Ru–PPy–PMO.
Ir–PPy–PMO: PPy–PMO (0.15 g) was added to a mixture of
K2CO3 (6.2 mg, 0.045 mmol), [Ir(ppy)2Cl]2 (0.015 g, 0.014 mmol), and
glycerol (15 mL) under an argon atmosphere. The suspension was
stirred and heated at 1208C for 24 h. The resulting precipitate was
filtered and washed with distilled water and CHCl3 to remove any
unreacted [Ir(ppy)2Cl]2, affording Ir–PPy–PMO.
efficient absorption of 300 nm light by the large amount of
PPy moieties in the PMO framework and the light energy is
transferred to the small amount of [IrIII(ppy)3] complexes
through Fçrster resonance energy transfer (FRET), which
enhances emission relative to the emission due to direct
excitation of the small amount of [IrIII(ppy)3] by 380 nm light
(Figure 3c). The almost complete quenching of the emission
from the PPy moieties at 420 nm for Ir–PPy–PMO suggests
efficient energy transfer from the PPy moieties to the
[IrIII(ppy)3] complex. The system presented is the first light-
harvesting system for energy funneling into the acceptor (Ir
complex) located on the pore walls, although we reported
some PMO-based light-harvesting systems, in which acceptors
such as dye molecules[18,19] and rhenium complexes[20] are
placed in the mesochannels. Ru–PPy–PMO showed almost no
emission because of the very low luminescence quantum yield
of [RuII(bpy)2(ppy)]+. However, efficient energy transfer
from the PPy moieties to [RuII(bpy)2(ppy)]+ should occur
owing to an efficient overlap of the absorption band of
[RuII(bpy)2(ppy)]+ with the emission band of PPy–PMO
(Figure 2a and d). This result suggests that the antenna effect
of PPy–PMO can enhance the photochemical properties of
the Ru complex such as the redox property and the excited-
state reactivity. The present light-harvesting systems with
acceptors on the pore walls have the advantage that pore
space can be fully utilized for further functionalization and as
reaction fields.
In conclusion, novel crystal-like PPy–PMO was success-
fully synthesized. The PPy moieties in the pore walls were
confirmed to function as ligands for cyclometalation, forming
highly functionalized RuII and IrIII complexes on the pore wall
while maintaining the mesoporous structure. The RuII com-
plexes are considered to be densely arranged on PPy–PMO,
whereas Ir–PPy–PMO exhibited light-harvesting properties.
The present PMOs can be further functionalized by incorpo-
rating functional molecules in the mesopores and/or coordi-
nating other metal complexes. They are thus highly promising
as a new class of functional hybrids and are suitable for
constructing various photochemical and photophysical sys-
tems.
Received: June 14, 2011
Revised: October 5, 2011
Published online: October 21, 2011
Keywords: mesoporous materials · metalation · phenylpyridine ·
.
sol–gel processes · solid-state structures
[1] a) S. Inagaki, S. Guan, Y. Fukushima, T. Ohsuna, O. Terasaki, J.
Am. Chem. Soc. 1999, 121, 9611 – 9614; b) T. Asefa, M. J.
MacLachlan, N. Coombs, G. A. Ozin, Nature 1999, 402, 867 –
871; c) B. J. Melde, B. T. Holland, C. F. Blanford, A. Stein, Chem.
Mater. 1999, 11, 3302 – 3308.
[2] a) W. J. Hunks, G. A. Ozin, J. Mater. Chem. 2005, 15, 3716 – 3724;
b) F. Hoffmann, M. Cornelius, J. Morell, M. Frçba, Angew.
Chem. 2006, 118, 3290 – 3328; Angew. Chem. Int. Ed. 2006, 45,
3216 – 3251; c) S. Fujita, S. Inagaki, Chem. Mater. 2008, 20, 891 –
908.
[3] a) W. Wang, J. E. Lofgreen, G. A. Ozin, Small 2010, 6, 2634 –
2642; b) N. Mizoshita, T. Tani, S. Inagaki, Chem. Soc. Rev. 2011,
40, 789 – 800.
[4] a) Applied Homogeneous Catalysis with Organometallic Com-
pounds (Eds.: B. Cornils, W. A. Hermann), VCH, Weinheim,
1996; b) Homogeneous Photocatalysis (Ed.: M. Chanon), Wiley,
New York, 1997; c) Transition Metal and Rare Earth Compounds
III (Ed.: H. Yersin), Springer, Heidelberg, 2004.
[5] a) P. N. Minoofar, R. Hernandez, S. Chia, B. Dunn, J. I. Zink, A.-
C. Franville, J. Am. Chem. Soc. 2002, 124, 14388 – 14396; b) C.
Peng, H. Zhang, J. Yu, Q. Meng, L. Fu, H. Li, L. Sun, X. Guo, J.
Phys. Chem. B 2005, 109, 15278 – 15287; c) B. Lei, B. Li, H.
Zhang, S. Lu, Z. Zheng, W. Li, Y. Wang, Adv. Funct. Mater. 2006,
16, 1883 – 1891; d) E. Besson, A. Mehdi, C. Reyꢀ, R. J. P. Corriu,
J. Chem. Mater. 2006, 16, 246 – 248; e) J. Font, P. d. March, F.
Busquꢀ, E. Casas, M. Benitez, L. Teruel, H. Garcꢁa, J. Mater.
Chem. 2007, 17, 2336 – 2343; f) E. Rossinyol, A. Prim, E. Pellicer,
Experimental Section
General: All reagents and solvents were commercially available and
were used without further purification. 1H and 13C NMR spectra were
obtained using a Jeol ECX-400 spectrometer operating at 400 and
100 MHz, respectively. 29Si dipolar decoupling (DD) and
13C CP MAS NMR measurements were performed at 79.49 and
100.6 MHz, respectively, at a sample spinning frequency of 4 kHz
using a Bruker Avance 400 spectrometer with a 7 mm zirconia rotor.
For the 29Si DD MAS NMR measurements, the repetition delay was
80 s and the pulse width was 4.5 ms. For the 13C CP MAS NMR
measurements, the repetition delay was 5 s, the contact time was
1.75 ms, and the pulse width was 4.5 ms (1H 908 pulse). Chemical shifts
were referenced to tetramethylsilane and glycine for 29Si and
13C NMR, respectively. XRD profiles were recorded on a Rigaku
RINT–TTR diffractometer using CuKa radiation (50 kV, 300 mV).
Nitrogen adsorption and desorption isotherms were measured using a
Yuasa Nova3000e sorptometer. BET surface areas were calculated
from the linear sections of BET plots (P/P0 = 0.1–0.2). Pore-size
distributions were calculated using the DFT method (DFT kernel: N2
11670 www.angewandte.org
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2011, 50, 11667 –11671

J. Arbiol, F. Hernꢂndez-Ramꢁrez, F. Peirꢃ, A. Cornet, J. R.
Morante, I. A. Solovyov, B. Tian, T. Bo, D. Zhao, Adv. Funct.
Mater. 2007, 17, 1801 – 1806; g) L.-N. Sun, H.-J. Zhang, J.-B. Yu,
S.-Y. Yu, C.-Y. Peng, S. Dang, X.-M. Guo, J. Feng, Langmuir
2008, 24, 5500 – 5507; h) Q. Yang, J. Liu, L. Zhang, C. Li, J. Mater.
Chem. 2009, 19, 1945 – 1955; i) A. Zamboulis, N. Moitra, J. J. E.
Moreau, X. Cattoꢄn, M. W. C. Man, J. Mater. Chem. 2010, 20,
9322 – 9338; j) J. Huang, F. Zhu, W. He, F. Zhang, W. Wang, H.
Li, J. Am. Chem. Soc. 2010, 132, 1492 – 1493; k) B. Karimi, D.
Elhamifar, J. H. Clark, A. J. Hunt, Chem. Eur. J. 2010, 16, 8047 –
8053.
[11] a) M. I. Bruce, Angew. Chem. 1977, 89, 75 – 89; Angew. Chem.
Int. Ed. Engl. 1977, 16, 73 – 86; b) M. Albrecht, Chem. Rev. 2010,
110, 576 – 623.
[12] a) S. Inagaki, S. Guan, T. Ohsuna, O. Terasaki, Nature 2002, 416,
304 – 307; b) M. P. Kapoor, Q. Yang, S. Inagaki, J. Am. Chem.
Soc. 2002, 124, 15176 – 15177; c) A. Sayari, W. Wang, J. Am.
Chem. Soc. 2005, 127, 12194 – 12195; d) M. Cornelius, F.
Hoffmann, M. Frçba, Chem. Mater. 2005, 17, 6674 – 6678; e) N.
Mizoshita, Y. Goto, M. P. Kapoor, T. Shimada, T. Tani, S.
Inagaki, Chem. Eur. J. 2009, 15, 219 – 226; f) M. Waki, N.
Mizoshita, T. Tani, S. Inagaki, Chem. Commun. 2010, 46, 8163 –
8165.
[13] E. C. Constable, J. M. Holmes, J. Organomet. Chem. 1986, 301,
203 – 208.
[14] P. J. Hay, J. Phys. Chem. A 2002, 106, 1634 – 1641.
[15] a) W. J. Finkenzeller, H. Yersin, Chem. Phys. Lett. 2003, 377,
299 – 305; b) T. Kobayashi, N. Ide, N. Matsusue, H. Naito, Jpn. J.
Appl. Phys. 2005, 44, 1966 – 1969.
[6] T. Kamegawa, T. Sakai, M. Matsuoka, M. Anpo, J. Am. Chem.
Soc. 2005, 127, 16784 – 16785.
[7] A. Kuschel, M. Luka, M. Wessig, M. Drescher, M. Fonin, G.
Kiliani, S. Polarz, Adv. Funct. Mater. 2010, 20, 1133 – 1143.
[8] a) K. Kalyanasundaram, M. Grꢅtzel, Coord. Chem. Rev. 1998,
177, 347 – 414; b) T. Bessho, E. Yoneda, J.-H. Yum, M.
Guglielmi, I. Tavernelli, H. Imai, U. Rothlisberger, M. K.
Nazeeruddin, M. Grꢅtzel, J. Am. Chem. Soc. 2009, 131, 5930 –
5934.
[9] a) M. A. Baldo, S. Lamansky, P. E. Burrows, M. E. Thompson,
S. R. Forrest, Appl. Phys. Lett. 1999, 75, 4 – 6; b) M. A. Baldo,
M. E. Thompson, S. R. Forrest, Nature 2000, 403, 750 – 753; c) T.
Tsutsui, M. Yang, M. Yahiro, K. Nakamura, T. Watanabe, T.
Tsuji, Y. Fukuda, T. Wakimoto, S. Miyaguchi, Jpn. J. Appl. Phys.
1999, 38, L1502 – L1504.
[10] a) K. Kalyanasundaram, Coord. Chem. Rev. 1982, 46, 159 – 244;
b) J. I. Goldsmith, W. R. Hudson, M. S. Lowry, T. H. Anderson,
S. Bernhard, J. Am. Chem. Soc. 2005, 127, 7502 – 7510; c) A.
Juris, V. Balzani, F. Barigelletti, S. Campagna, P. Belser, A. V.
Zelewsky, Coord. Chem. Rev. 1988, 84, 85 – 277; d) D. A.
Nicewicz, D. W. C. MacMillan, Science 2008, 322, 77 – 80; e) K.
Okeyoshi, R. Yoshida, Chem. Commun. 2011, 47, 1527 – 1529.
[16] A. B. Tamayo, B. D. Alleyne, P. I. Djurovich, S. Lamansky, I.
Tsyba, N. N. Ho, R. Bau, M. E. Thompson, J. Am. Chem. Soc.
2003, 125, 7377 – 7387.
[17] a) S. Bracco, A. Comotti, P. Valsesia, B. F. Chmelka, P. Sozzani,
Chem. Commun. 2008, 4798 – 4800; b) A. Comotti, S. Bracco, P.
Valsesia, M. Beretta, P. Sozzani, Angew. Chem. 2010, 122, 1804 –
1808; Angew. Chem. Int. Ed. 2010, 49, 1760 – 1764.
[18] S. Inagaki, O. Ohtani, Y. Goto, K. Okamoto, M. Ikai, K.
Yamanaka, T. Tani, T. Okada, Angew. Chem. 2009, 121, 4102 –
4106; Angew. Chem. Int. Ed. 2009, 48, 4042 – 4046.
[19] a) H. Takeda, Y. Goto, Y. Maegawa, T. Ohsuna, T. Tani, K.
Matsumoto, T. Shimada, S. Inagaki, Chem. Commun. 2009,
6032 – 6034; b) Y. Maegawa, N. Mizoshita, T. Tani, S. Inagaki, J.
Mater. Chem. 2010, 20, 4399 – 4403.
[20] H. Takeda, M. Ohashi, T. Tani, O. Ishitani, S. Inagaki, Inorg.
Chem. 2010, 49, 4554 – 4559.
Angew. Chem. Int. Ed. 2011, 50, 11667 –11671
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org 11671