96
Z. Zhang et al. / Dyes and Pigments 118 (2015) 95e101
relatively bulky naphthyl group also can be used as substituent
groups in the construction of AIE luminogens, but the fluorescence
quantum yield of tetra(naphthalen-2-yl)ethene in aggregation
state is much lower than that of TPE owning to the formation of
dichloromethane (50 mL) and then oxalyl chloride (1.7 mL,
20 mmol) were added dropwise in 20 min at 15 C. 8 mL dry and
ꢁ
deaerated dichloromethane solution of 4,5,9,10-tetrahydropyrene
(2.06 g, 10 mmol) was added into the mixture dropwise in 1 h.
The reaction mixture was warmed to room temperature and stirred
for 1 h. A second equivalent 4,5,9,10-tetrahydropyrene (2.06 g,
10 mmol) in dry and deaerated dichloromethane was introduced
portionwise over 10 min. After stirring overnight, the reaction
mixture was chilled in an ice/water bath, and water (40 mL) was
added dropwise over 10 min. The organic layer was extracted with
dichloromethane, and the combined organic layers were washed
with a saturated brine solution and water, and dried over anhy-
drous magnesium sulfate. After filtration and solvent evaporation,
the residue was purified by silica-gel column chromatography us-
ing hexane/dichloromethane as eluent. The ketone, as a white solid,
strong
reflects the fact that common aromatics with expanded
gation possess a bulky planar structure, which tends to suffer from
-stacking interactions. We wondered whether a tetra(polycyclic
p
-stacking interaction between naphthalene rings. This case
p-conju-
p
aryl)ethene with excellent solid-state emission can be obtained by
adopting carefully selected PAHs as substituent groups which not
only have an enlarged
p-conjugation system but also have effective
steric hindrance to restrict the formation of
p-stacking. To verify
this thought, three PAHs were selected to build tetra(polycyclic
aryl)ethene as substituent groups. Biphenyl has twisted structure
which can hinder the formation of
pep interactions to a certain
ꢁ
ꢀ1
extent but lead to relative poor electron communication between
was obtained in 68% yield. Mp: 265e267 C. IR (KBr, cm ): 3056,
the two phenyl rings. On the contrary, fluorene, a typical planar
2392, 2883, 2832, 1642, 1596, 1425, 1437, 1296, 1182, 783, 774, 736.
1
aromatic, has expanded
hindrance. 4,5,9,10-tetrahydropyrene is the ideal PAH which pos-
sesses both enlarged -conjugation and certain steric hindrance.
p
-conjugation but lacks effective steric
3
H NMR (400 MHz, CDCl ), d (TMS, ppm): 7.60 (s, 4H), 7.25e7.20 (m,
13
2H), 7.17e7.13 (d, 4H, J ¼ 7.15 Hz), 2.97 (m, 16H). C NMR (400 MHz,
p
CDCl ), (TMS, ppm): 196.62, 136.52, 136.17, 135.27, 134.60, 129.94,
3
d
Based on these PAHs, three new tetra(polycyclic aryl)ethenes were
synthesized and the emission behavior of the resultant molecules
were investigated in detail.
128.24, 127.81, 126.18, 28.27, 28.19. MALDI-TOF MS: m/z 438.328
þ
(M ). Anal. Calcd for C33H26O: C, 90.38; H, 5.98. Found: C, 90.24; H,
6.02.
2
. Experimental section
2.3. 2,2'-difluorenyl ketone (2)
2.1. General
The procedure was analogous to that described for compound 1.
The ketone, as a white solid, was obtained with the yield of 72%.
ꢁ
ꢀ1
All reactions were carried out under a nitrogen atmosphere. All
reagents were purchased from commercial sources as analytically
Mp: 281e283 C. IR (KBr, cm ): 3077, 2923, 1645, 1608, 1421, 1394,
1
1309, 1297,1275, 741. H NMR (400 MHz, CDCl
3
), d (TMS, ppm): 8.08
pure grade. Dichloromethane was dried and purified by distillation
(s, 2H), 7.95e7.88 (m, 6H), 7.65e7.61 (d, 2H, J ¼ 7.63 Hz), 7.49e7.38
13
before use from CaH
2
. THF was distilled from sodium benzophe-
3
(m, 4H), 4.02 (s, 4H). C NMR (400 MHz, CDCl ), d (TMS, ppm):
none ketyl under dry nitrogen immediately prior to use. 4,5,9,10-
tetrahydropyrene was prepared by a method reported in the liter-
ature [10].
196.83, 145.77, 144.41, 143.12, 140.65, 136.52, 129.57, 127.94, 127.09,
126.77, 125.28, 120.82, 119.40, 36.97. MALDI-TOF MS: m/z 358.250
þ
(M ). Anal. Calcd for C27
H18O: C, 90.47; H, 5.06. Found: C, 90.39; H,
1H and 13C NMR spectra were measured on a Bruker AV 400 or
5.12.
6
00 spectrometer in CDCl
3
using tetramethylsilane (TMS;
d
¼ 0) as
internal reference. Mass spectra were obtained on a Bruker Ultra-
flextreme MALDI TOF/TOF mass spectrometer or an IonSpec HiR-
esMALDI FT mass spectrometer. IR spectra were recorded on KBr
pellets using a Nicolet 7199B FT/IR spectrophotometer in the region
of 4000e400 cm . C, H, and N analyses were obtained on an Ele-
mentar Vario El instrument. UVeVis spectra were recorded on
2.4. 4,4'-diphenyl ketone (3)
The procedure was analogous to that described for compound 1.
The ketone, as a white solid, was obtained in 63% yield. Mp:
ꢀ1
ꢁ
ꢀ1
239e240 C. IR (KBr, cm ): 3073, 2923, 1639, 1400, 1318, 1297, 736,
1
3
692. H NMR (400 MHz, CDCl ), d (TMS, ppm): 7.94e7.98 (d, 4H,
Shimadzu UV-3600 with
Emission spectra were performed on a Hitachi fluorimeter (F-
600). Concentrated solutions of the three compounds were drop-
casted on quartz plate to prepare films [9], and values of the
amorphous films were determined by FM-4P-TCSPC Transient State
Fluorescence Spectrometer using an integrating sphere. The crystal
data was collected on a Bruker APEX II CCD diffractometer using
a
UVeVISeNIR spectrophotometer.
J ¼ 7.96 Hz), 7.78e7.73 (d, 4H, J ¼ 7.76 Hz), 7.73e7.65 (d, 4H,
J ¼ 7.69 Hz), 7.48e7.55 (t, 4H, J ¼ 7.53 Hz), 7.47e7.42 (t, 2H,
1
3
4
J ¼ 7.45 Hz). C NMR (400 MHz, CDCl
3
), d (TMS, ppm): 195.94,
F
F
145.22, 140.03, 136.43, 130.68, 128.99, 128.20, 127.33, 127.02.
þ
MALDI-TOF MS: m/z 334.272 (M ). Anal. Calcd for C25
89.79; H, 5.43. Found: C, 89.77; H, 5.51.
H18O: C,
graphite monochromatized Mo-K
a
radiation (
l
¼ 0.71073 Å) with
2.5. Tetrakis(4,5,9,10-tetrahydropyren-2-yl)ethene (4)
u
-scan techniques at 123 K. The structure is solved by direct
methods using the SHELXS-97 [11] computer program and refined
with full-matrix least-squares methods. Cyclic voltammetry ex-
periments were performed with a CHI660A electrochemical work
To a solution of compound 1 (0.877 g, 2 mmol), zinc dust (0.39 g,
6 mmol) in dry THF (80 mL) was added dropwise titanium (IV)
ꢁ
chloride (0.58 g, 3 mmol) under nitrogen at ꢀ78 C. After stirring
station using 0.1 M n-Bu
4
NPF
6
in dichloromethane as supporting
for 20 min, the reaction mixture was warmed to room temperature
and then heated to reflux for 12 h. The reaction mixture was cooled
to room temperature and poured into water. The organic layer was
extracted with dichloromethane and the combined organic layers
were washed with saturated brine solution and water, and dried
over anhydrous magnesium sulfate. After filtration and solvent
evaporation, the residue was purified by silica-gel column chro-
matography using hexane/dichloromethane as eluent. Compound 4
electrolyte. All measurements were carried out at room tempera-
ture with a conventional three-electrode configuration consisting
of a platinum disk working electrode, a platinum auxiliary elec-
trode and a calomel reference electrode.
2.2. 2,2'-bis-(4,5,9,10-tetrahydropyrenyl) ketone (1)
1
Aluminum chloride (2 g, 15 mmol) was introduced into a
was obtained as a yellow-green solid in 52% yield. H NMR
Schlenk flask and deaerated under vacuum. Dry, deaerated
3
(600 MHz, CDCl ), d (TMS, ppm): 7.09e7.12 (m, 4H), 7.06e7.03 (d,