film. The film exhibited monomeric absorption and an excimer
fluorescence emission, which is a typical behavior for PMO films.
Dye-doping of the film resulted in quenching of the emission from
the framework, while strong emission from the dye was promoted,
which confirmed light-harvesting antenna properties.
2,7-Dibromo-9-methylacridone. To a mixture of 9-methyl-
acridone (6.00 g, 28.7 mmol) in distilled DMF (280 mL) was
added dropwise a solution of N-bromosuccinimide (10.8 g,
60.7 mmol) in distilled DMF (80 mL) at 0 ꢁC. The reaction
ꢁ
mixture was stirred at 80 C for 18 h, and quenched with H2O.
The resulting solid was collected by filtration and thoroughly
washed with hexane to give the title compound as yellow solid
(6.57 g, 62%). The filtrated water phase was extracted with
chloroform, then washed with brine, dried over sodium sulfate,
and concentrated. The residue was washed with hexane to give
the title compound (3.80 g, total yield is 98%). dH (400 MHz,
CDCl3, Me4Si), 3.87 (3H, s, CH3), 7.41 (2H, d, J 9.2 Hz,
aromatic), 7.79 (2H, dd, J 2.6 and 9.2 Hz, aromatic), 8.62 (2H, d,
J 2.6 Hz, aromatic).
Experimental
Materials and general methods
All reagents and solvents were purchased from Aldrich, Tokyo
Chemical Industry, Wako Pure Chemical Industries, and Nacalai
Tesque and used without further purification. A poly(ethylene
oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide)
triblock copolymer (EO20–PO70–EO20, P123) (Aldrich) was used
as a nonionic template surfactant. Precursor 1 was synthesized
according to the literature.18 Nuclear magnetic resonance
(NMR) spectra were recorded on a Jeol JNM-EXC400P spec-
trometer (400 MHz for 1H and 100 MHz for 13C). Chemical shifts
are reported in d ppm referenced to an internal SiMe4 standard
2,7-Bis(triethoxysilyl)-9-methylacridone (2). To a mixture of
[Rh(CH3CN)2(cod)]BF4 (74.4 mg, 0.20 mmol), 2,7-dibromo-9-
methylacridone (1.20 g, 3.27 mmol), and n-Bu4NI (2.41 g,
6.52 mmol) were added distilled DMF (48 mL) and triethylamine
(2.74 mL, 19.7 mmol). After addition of triethoxysilane
(2.41 mL, 13.1 mmol), the reaction mixture was stirred at 80 ꢁC
for 2 h, then concentrated under vacuum to remove DMF. The
resulting mixture was treated with Et2O to give a solution of the
title compound in Et2O, which was filtered through a Celite plug
and charcoal, and the filter cake was rinsed with Et2O. The
combined filtrates were concentrated under vacuum to give
the title compound as yellow crystalline solid (1.72 g, 99%).
lmax(i-PrOH)/nm 314 (3/dm3 molꢀ1 cmꢀ1 10 800), 381 (6400) and
398 (7600); nmax(neat)/cmꢀ1 2971, 2925, 2887, 1641(C]O), 1599,
1479, 1176 and 958; dH (400 MHz, CDCl3, Me4Si), 1.28 (18H, t,
J 7.2 Hz, 6 ꢂ OCH2CH3), 3.92 (3H, s, CH3), 3.93 (12H, q, J 7.2
Hz, 6 ꢂ OCH2CH3), 7.55 (2H, d, J 8.7 Hz, aromatic), 8.02
(2H, dd, J 1.4 and 8.7 Hz, aromatic), 8.91 (2H, d, J 1.4 Hz,
aromatic); dC (100 MHz, CDCl3, CDCl3) 18.3, 33.6, 58.9, 114.3,
122.3, 123.4, 135.5, 139.7, 143.9, 178.0 (C]O); m/z (ESI)
533.2250 (M+. C26H39NO7Si2 requires 533.2265).
1
for H NMR and chloroform-d (d 77.0) for 13C NMR. Infrared
(IR) absorption measurements were conducted on a Thermo
Nicolet Avatar 360 FT-IR spectrometer using an attenuated
total reflection (ATR) attachment. Mass spectra were recorded
on a Bruker Daltonics Autoflex mass spectrometer (MALDI:
matrix-assisted laser desorption ionization). Optical microscopy
observations were performed using an Olympus BX51 micro-
scope. X-Ray diffraction (XRD) measurements were performed
on a Rigaku RINT-TTR diffractometer with Cu-Ka radiation
(50 kV, 300 mA). Ultraviolet-visible (UV-vis) absorption spectra
were measured using a Jasco V-670 spectrometer. Fluorescence
emission spectra were obtained using a Jasco FP-6500 spec-
trometer. Fluorescence quantum yields were determined using
a
photoluminescence quantum yield measurement system
equipped with a calibrated integrating sphere (Hamamatsu
Photonics, C9920-02). Optical measurements were carried out
for the films without extraction of the surfactant to suppress
fluorescence quenching by oxygen11 (Fig. S9 in ESI†) and
aggregation of dye molecules in the mesochannels.17
Preparation of organosilica films. The acridone- or 9-methyl-
acridone-bridged organosilane precursors (1 or 2, 60 mg) and
P123 (60 mg) were dissolved in EtOH (2.0 g), and then deionized
water (12.0 mL) and 2 M HCl aqueous solution (4.0 mL) were
added to the solution. The mixture was stirred at room temper-
ature for 3 h (for 1) or 24 h (for 2) to form the sol solution. After
passing through a membrane filter (0.20 mm), the sol solution was
coated on a quartz glass plate by spin-coating (4000 rpm, 30 s)
and dried under reduced pressure to give an organosilica film. In
case of the dye doping, the DCM dye (ethanol solution) was
added to the sol solution (the molar DCM/2 ratios of 0.5, 1 and
5 mol%) and then stirred for a few minutes at room temperature
just prior to spin-coating.
Synthesis
Precursor 2 was synthesized according to the synthetic route
shown in Scheme S1†.
9-Methylacridone. To a mixture of 9(10H)-acridone (6.00 g,
30.7 mmol) in distilled DMF (240 mL) was added NaH (3.07 g,
60% oil dispersion, 76.7 mmol) at 0 ꢁC. The reaction mixture was
stirred at 60 ꢁC for 30 min, then iodomethane (4.80 mL,
ꢁ
77.0 mmol) was added, and stirring was continued at 60 C for
18 h. The reaction mixture was quenched with H2O. The
resulting solid was collected by filtration and thoroughly washed
with ethanol to give title compound as light-yellow solid (4.77 g,
74%). The filtrated water phase was extracted with chloroform,
them washed with brine, dried over magnesium sulfate, and
concentrated to give the title compound (1.31 g, total yield is
95%). dH (400 MHz, CDCl3, Me4Si), 3.89 (3H, s, CH3), 7.29
(2H, dt, J 1.8 and 7.3 Hz, aromatic), 7.51 (2H, d, J 7.7 Hz,
aromatic), 7.72 (2H, dt, J 1.8 and 7.3 Hz, aromatic), 8.56 (2H, dd,
J 1.8 and 7.7 Hz, aromatic).
Removal of the template surfactant from organosilica films
In order to remove the template surfactant, the organosilica films
were exposed to the vapor of a 28% NH3 aqueous solution
at 60 ꢁC for 12 h, and then immersed in ethanol for 12 h at 60 ꢁC
to provide a surfactant-free sample. Complete removal of the
surfactant was confirmed by IR measurements (Fig. S4 in ESI†).
4402 | J. Mater. Chem., 2010, 20, 4399–4403
This journal is ª The Royal Society of Chemistry 2010