J. Phys. Chem.
B 2005, 109, 19627-19633 19627
Dibenzosuberenylidene-Ended Fluorophores: Rapid and Efficient Synthesis,
Characterization, and Aggregation-Induced Emissions
Zixing Wang, Hongxia Shao, Jianchuan Ye, Lei Tang, and Ping Lu*
Chemistry Department, Zhejiang UniVersity, Hangzhou, 310027, P. R. China
ReceiVed: June 9, 2005; In Final Form: August 11, 2005
A series of π-conjugated compounds ending with dibenzosuberenylidene were synthesized efficiently. Their
luminescence efficiencies were well-tuned by structural modification. Moreover, relative emission intensities
were strongly affected by their existing appearances and exhibited aggregation-induced emission (AIE) behavior.
Thus, emissions from nanoparticles, films, or powders were found to be more efficient than those from solutions.
It demonstrated that these synthesized compounds might be practically used as fluorescent materials for potential
optoelectronic applications.
Introduction SCHEME 1: Synthesis of Conjugated Compounds
During the past decade, many studies on organic light-
emitting materials have been focused on developing efficient,
stable, and high color purity materials since the first efficient
molecule-based organic light-emitting diodes (OLEDs) fabri-
cated by Tang and VanSlyke in 1987.1 However, ordered regions
resulted in strong interchain coupling and lowered emission
quantum yields in the case of polymer LEDs.2 To address the
above problems, studies on light-emitting materials with tetra-
hedral structure,3 cross-linked oligofluorene network,4 and Si-
containing hyperbranched architecture3f,5 have been completed.
Nevertheless, there still existed a serious problem of photolu-
minescence (PL) in solid states, which mostly exhibited lower
efficiency compared with its performance in solution and limited
its real utility. Therefore, it would be ideal if a molecule could
emit intense light in its solid state. Swager and co-workers
elegantly observed this unusual phenomenon that the PL
quantum yield (ΦF) of an aggregated film of a poly(p-
phenylenethynylene) (PPE) was 3.5 times that of its solution.6
Similar phenomena about aggregation-induced emissions (AIE)
were further reported.7 AIE-active materials were thereby found
to be promising emitters for fabrication of highly efficient
LEDs.8 Thus, it is necessary to create molecular structures with
AIE-active features.
Here, we wish to report the simple and efficient synthesis of
a series of compounds ending with dibenzosuberenylidene
groups. It is based on our continued research on non-benzenoid
aromatic systems with specific optoelectronic properties.9 On
the basis of optical studies of synthesized compounds, their PL
efficiencies in thin films or in powders were strongly enhanced
compared to those in solutions. AIE behavior was observed.
By investigating solvent, temperature, and concentration effects
individually, a conclusion has been made that AIE behavior may Wittig-Horner reaction was selected to synthesize 1a and 1b
be attributed to J-type aggregation with restricted intramolecular in 86% and 88% yields, respectively. Intermediate 2 was
rotation in solid states. obtained in 82% yield by a similar procedure. Subsequent
treatment of 2 with trimethylsilylacetylene, followed by desi-
Results and Discussion lylation, led to intermediate 4 in 91% yield.10 The Sonagoshira
reaction11 provided an effective way to build π-systems with
Synthesis. Synthetic routes to compounds ending with triple bonds. Thus, 4 was used as a substrate to react with 2,7-
dibenzosuberenylidene groups were shown in Scheme 1. The diiodo-9,9′-dialkylfluorene,12 and 3,6-diiodo-9-alkyl carbazole13
under Sonagoshira reaction conditions. A series of compounds
* pinglu@zju.edu.cn. (5, 6) were synthesized in moderate yields. The Hay coupling
10.1021/jp053113j CCC: $30.25 © 2005 American Chemical Society
Published on Web 10/05/2005
19628 J. Phys. Chem. B, Vol. 109, No. 42, 2005 Wang et al.
TABLE 1: Optical Properties of Compounds
absorption λmaxabs (nm) photoluminescence λmaxPL (nm)c quantum yield ΦF (%)e
a b a d b
compd solution nanosuspension solution film powder nanosuspension solutiona filmc
1a 333 337 (70%) 445 (371) 440 465 450 (70%) 0.0048 0.72
1b 339 378 (70%) 429 (358) 444 456 453 (70%) 0.012 0.71
5a 370 429 (70%) 409, 428 (361) 435 503 494 (70%) 0.065 0.67
5b 370 419 (50%) 408, 425 (361) 454 509 499 (50%) 0.084 0.73
5c 370 410 (50%) 412, 486 (361) 453 513 480 (50%) 0.083 2.1
5d 370 403 (50%) 409, 447 (361) 436 498 466 (50%) 0.073 1.2
6 358 396 (60%) 407, 431 (372) 428 448 439 (60%) 0.015 0.43
7 356 399 (70%) 415, 444 (378) 441 473 472 (70%) 0.023 0.99
a
Measured in THF. b Water fractions are given in parentheses. c Excited wavelengths are given in parentheses. d Dispersed in PMMA films.
e
Quantum yields were calculated on the basis of 9,10-diphenylanthracene as standard (Φ ) 0.95 in hexane; Φ ) 0.83 in PMMA).
reaction14 generated 7 in 85% yield. All synthesized compounds
were characterized by 1H NMR, 13C NMR, and high-resolution
mass spectroscopy (HRMS) matrix-assisted laser desorption
ionization (MALDI).
Absorption and Emission Measurement. Compounds were
soluble in common organic solvents, such as tetrahydrofuran
(THF), toluene, chloroform , and so forth. Absorption and
emission spectra in solution were measured in THF (5 × 10-6
M). Nanoparticles were formed by adding a large quantity of
water into dilute 1,4-dioxane solution. Thin films were prepared
by doping a certain amount of fluorophores in poly(methyl
methacrylate) (PMMA) (concentration < 0.1 wt %). Absorption
and emission properties in different appearances were sum-
marized in Table 1. Normalized UV-vis absorption and
fluorescence spectra for 1 and 5-7 in solutions, in thin films,
and in powders are available in the Supporting Information.
Figure 1. Absorption and emissions of 5a.
Absorption Properties in Solutions. Maximum absorption
wavelength of 1a was found at 333 nm. In comparison to 1a,
in individual diphenylacetylene moieties. However, the delo-
maximum absorption wavelengths of 1b and 5-7 were all
calization of the triplet wave function in 5a is well-extended
bathochromically shifted as the conjugated length increased.
through the fluorene core (resembling p-biphenyl).16 This is also
Maximum Emission Wavelengths vs Their Existing Ap-
in accordance with studies on polyphenyl molecules. For
pearances. Maximum emission wavelength of 1a was found to
p-polyphenyl molecules, the conjugated system is delocalized
be 445 nm in dilute solution and 440 nm in thin film when
along the longest molecular axis, and for m-polyphenyl mol-
both were excited at 371 nm. Emissions of 1b and 5-7 were
ecules, the triplet state is localized at every composing biphenyl
all blue-shifted compared to 1a, except for 5c and 5d in solutions.
structure (Scheme 3).17
Maximum emission wavelengths from thin films with low
concentrations (<0.1 wt %) of fluorophores were similar to those Quantum Yields vs Their Existing Appearances. In
in solutions. When powder samples were measured for emission comparison to emission in solution, emission from solid should
properties, maximum emission wavelengths were all red-shifted, be more attractive and practical, because the real state of the
typically for those with fluorene cores (5a-5d). Furthermore, emitter fabricated in an optoelectronics device should be solid.
maximum emission wavelengths observed for nanoparticles It was observed that quantum yields of all synthesized com-
were similar to those in powders. For example, 5a emitted at pounds (1, 5-7) in films were higher than those in solutions
503 nm in powder (PLP), which was 68 nm red-shifted to its (Table 1). For instance, the quantum yield of 1a in film was
emission wavelength in thin film (PLF), and 75 nm red-shifted 150 times that in solution.
to its emission wavelength in solution (PLS) (Figure 1). The cause might be exciton diffusion and rotational deactiva-
Quantum Yields vs Molecular Structures. Quantum yields tion in solution, which increased the number of nonradiative
were calculated on the basis of 9,10-diphenyl anthracene (Φ ) routes and decreased the luminescence efficiency7b,8b in solution.
0.95 in hexane, Φ ) 0.83 in PMMA).15 As we designed As to powder or film, intramolecular rotation was highly
molecular structures for better optical performance, 5 showed restricted because of molecular stacking. This result could also
the highest quantum yields in solutions. The quantum yield of be clearly seen from Table 1. By structural analysis, 1a f 1b
1b was 2.5 times that of 1a due to longer conjugation. The f 7 f 5b (Scheme 2), 1a has the smallest molecular size with
quantum yield of 7 was 1.9 times that of 1b due to planarization the fastest movement in solution. To the solid state, molecular
of 7 by inserting diyne into two phenyl rings to release torsional movement is restricted. Therefore, incremental increases of
strain. When a fluorene core was introduced between two triple quantum yield for 1a from solution to thin film is the largest.
bonds, longer conjugation was constructed. Thus, the quantum Experimental data supported this postulation. The quantum yield
yield of 5b was 3.7 times that of 7. Luminescent efficiency was of 1a in film was 150 times that in solution, while only 60, 43,
well-tuned by structural modification (Scheme 2). and 9 orders of magnitude incremental increases were observed
Although 6 had a similar planar core as 5, a relatively lower by changing the state from solution to thin film for 1b, 7, and
quantum yield was observed for 6. The reason might be that 5b, respectively.
the delocalization of the triplet wave function in 6 is not limited Restricted Intramolecular Rotation vs Temperature. It is
to the carbazole core (resembling m-biphenyl), but is limited well-known that the rotational deactivation of an exciton was
Dibenzosuberenylidene-Ended Fluorophores J. Phys. Chem. B, Vol. 109, No. 42, 2005 19629
SCHEME 2: Emission Efficiency Tuned by Structural Modification
SCHEME 3: Chemical Structure of 6 (top) and 5a
(bottom)a
a
For compound 6, the longest poly(p-phenylacetylene) chain is
diphenylacetylene, while for compound 5a, the chain is through biphenyl
core.
highly dependent on solution temperature. Cooling-enhanced
emissions as evidence for restricted intramolecular rotation were
shown in Figure 2a. When dilute solutions of 1a, 5a, and 7 in
1,4-dioxane were cooled from 15 °C to -82 °C, solutions were
gradually changed into a glassy solid. By recording emission
spectra, it was found that emission efficiencies were increased
as the temperature decreased. For instance, emission efficiency
was amplified 13 times when the solution temperature changed
from 15 °C to -82 °C (Figure 2b). It indicated that the rotation
of heavy dibenzosuberenylidene groups was effectively limited
when the temperature decreased. Restricted molecular rotation
resulted in the enhanced emission efficiency.
Emission Efficiency vs Concentration. Emission efficiency
Figure 2. (a) Temperature effect on PL peak intensities of 1a, 5a, and
was dependent not only on the temperature, but on the 7 in 1,4-dioxane. (b) PL spectra of diluted solution of 5a (30 µM) in
concentration also. As the concentration of 5a in PMMA films 1,4-dioxane with changing temperature.
increased, emission efficiency increased (Figure 3). That could
be explained by aggregation-induced emission behavior. Except might be that 5a dispersed in film might exist in its J-type
for this significant efficiency change, noticeable red-shifted aggregation state at high concentration.
emission were observed in this case. When the fluorophore Aggregation-Induced Emission. Emission enhancement
concentration reached 15.5wt % in thin film, the maximum resulting from fluorescent nanoparticle formation is the alterna-
emission wavelength of 5a reached 491 nm, and finally tive way to prove AIE behavior.7 Nanoparticles could be
resembled its powder emission (λmax ) 503 nm). The reason prepared by a simple reprecipitation without surfactants.18 When
19630 J. Phys. Chem. B, Vol. 109, No. 42, 2005 Wang et al.
Figure 3. Emission spectra of 5a in films with certain concentrations
(wt %).
Figure 5. UV absorption spectra (a) and PL spectra (b) of 5b in water/
1,4-dioxane mixture with different volume fractions of water; concen-
Figure 4. Changes of PL peak intensities of 1 and 5-7 vs solvent tration of 5b, 20µM.
compositions of the water/1,4-dioxane mixtures.
a large quantity of water was added into a dilute 1,4-dioxane methods in good yields. Their luminescent efficiencies were
solution of fluorophore, emission spectra were recorded. As well-tuned by structural modification. The synthesized com-
shown in Figure 4, turning points were observed in each case. pounds exhibited enhanced fluorescence emissions in solid
Beyond these points, a dramatic increase in emission efficiency states. Emission efficiencies could be enhanced by adding water
was observed. to induce nanoparticle formation, by lowering temperature to
A typical example of this scenario was shown in Figure 5. form a glassy solid, or by doping in PMMA to restrict
When dilute solution of 5b was added with a large quantity of intramolecular rotation. Synthesis of these organic emitters
water, luminescence efficiency was increased 25 times when systematically has proven to be an efficient way to produce
the water fraction reached 70%. As the water fraction reached excellent candidates for the potential utility in optoelectronics
80%, the vessel was still visually clear and macroscopically applications.
homogeneous. Their aggregation must be nanodimensional.
Transmission electron microscopy (TEM) showed nanoparticle Experiment Section
size (80-200 nm) and distributions (Figure 6).
By recording UV absorption spectra of 5b in water and 1,4- General. Tetrahydrofuran and 1,4-dioxane for UV-vis and
dioxane with different ratios, red-shifted absorption was seen fluorescence spectroscopic measurements were redistilled. Dis-
in this case as the water fraction increased (Figure 5). The red- tilled water was filtered through a membrane with 0.22-µm pore
shifted absorption spectra indicated that J-type aggregation size. Commercially available reagents were used without further
occurred in this case.7a,19 Further, the ability to red-shift reflected purification unless otherwise stated. Melting points were
the aggregation degree of the fluorophore. By investigation UV recorded on a BÜCHI 535. 1H NMR and 13C NMR spectra were
absorption spectra, only a 4-nm red-shift was observed for 1a obtained on a Bruker AVANCE DMX500 spectrometer in
with the shortest conjugated linkage, while a 59-nm red-shift CDCl3 as solvent with tetramethylsilane (TMS) as internal
was found for 5a with the longest conjugated linkage. Moreover, standard. UV-vis absorption spectra were recorded on a
as for compounds 5 with different lengths of alkyl groups at Shimadzu UV-2450 spectrophotometer. Fluorescence spectra
nine positions, absorption spectra of 5b, 5c, and 5d showed less were recorded on a Shimadzu RF-5301PC spectrofluoropho-
red-shift (∆λ ) 49, 40, and 33 nm, respectively) than that of 5a tometer. MALDI mass spectra were obtained on an Ionspec 4.7
because of decreasing stacking efficiencies resulting from T FTMS mass spectrometer and ESI mass spectra were obtained
increasing lengths of side chains. on a Bruker Esquire 3000 Plus with Bruker Daltonics DataAnal-
In conclusion, a series of π-conjugated compounds ending ysis 3.0 instrument. TEM micrographs were obtained on a JEM-
with dibenzosuberenylidene groups were synthesized by general 200CX transmission electron microscope. All reactions were
Dibenzosuberenylidene-Ended Fluorophores J. Phys. Chem. B, Vol. 109, No. 42, 2005 19631
Figure 6. The TEM micrographs of 1, 5, 6, and 7 nanoparticles obtained from nanoparticles’ suspension with corresponding water fraction (vol
%) in 1,4-dioxane.
carried out under N2. All samples for UV-vis and fluorescence 4-(Dibenzosuberenylidenemethyl)-iodobenzene (2) was pre-
spectroscopic measurements were recrystallized from hexane/ pared by a similar method as above except that the residue was
chloroform. purified by recrystallization from chloroform/ethanol. Yield
Synthesis. 2,7-Diiodo-9,9′-dialkylfluorene12 and 3,6-diiodo- 82%, mp 167-168.5 °C. 1H NMR (CDCl3): δ 6.4 (1H, s), 6.63
9-ethylcarbazole13 were prepared by literature procedures. (2H, d, J ) 8.0 Hz), 6.92 (1H, d, J ) 12.0 Hz), 6.97 (1H, d, J
General Procedures for Synthesis of 1,4-Bis(dibenzosuber- ) 12.0 Hz), 7.07 (1H, d, J ) 7.5 Hz), 7.18 (1H, dd, J ) 7.5
enylidenemethyl)benzene (1a) and 4,4′-Bis(dibenzosuberenyliden- Hz), 7.27-7.30 (3H, m), 7.38-7.42 (4H, m), 7.50, (1H, d, J )
emethyl)biphenyl (1b). Diethyl bis(arylmethyl)phosphonate (1 7.0 Hz). 13C NMR (CDCl3): δ 92.43, 127.05, 127.40, 127.72,
mmol) and dibenzosuberenone (2 mmol) were dissolved in 40 128.62, 129.12, 129.17, 131.19, 131.32, 131.66, 134.42, 135.04,
mL anhydrous THF under nitrogen. The mixture was refluxed 136.67, 137.21, 142.33, 143.51. MS (ESI): m/z 406.8 ([M +
under stirring. To this solution, solid potassium tert-butoxide H]+).
(3 mmol) was added in one portion. After refluxing for 3 h, 4-Trimethylsilylethynyl(dibenzosuberenylidenemethyl)-
solvent was removed by rotary evaporation. The residue was benzene (3) was prepared from 2 by literature procedure.10 A
purified by column chromatography (silica gel) using n-hexane/ mixture of 2 (406 mg, 1 mmol), trimethylsilylacetylene (150
dichloromethane (6:1 by volume) as eluent. In this way, 1a and mg, 1.5 mmol), CuI (20 mg, 0.1 mmol), PPh3 (26.2 mg, 0.1
1b were obtained as a yellow solid, respectively. mmol), and Pd(PPh3)2Cl2 (10 mg, 0.013 mmol) in Et3N (40 mL)
1a: yield 86%, mp 210.5-211.7 °C. 1H NMR (CDCl3): δ was refluxed for 40 h. After cooling to room temperature, the
6.38 (s, 0.84H), 6.39 (s, 1.16H), 6.64 (s, 1.70H), 6.67 (s, 2.25H), solvent was removed by evaporation. The residue was purified
6.87 (d, 2H, J ) 12.0 Hz), 6.92 (d, 2H, J ) 12.0 Hz), 7.06- by column chromatography as above. In this way, 362 mg of 3
7.16 (m, 4H), 7.21-7.28 (m, 6H), 7.33-7.38 (m, 4H), 7.45- was obtained in 96% yield as a yellowish solid. Mp 122.9-
7.47 (m, 2H) ppm. 13C NMR (CDCl3): δ 127.14, 127.18, 124.1 °C. 1H NMR (CDCl3): δ 0.21 (s, 9H), 6.46 (s, 1H), 6.82
127.21, 127.50, 128.54, 128.57, 128.89, 128.98, 129.01, 129.09, (d, 2H, J ) 8.0 Hz), 6.90, (d, 1H, J ) 12.0 Hz), 6.96 (d, 1H,
129.12, 129.30, 129.45, 131.42, 131.45, 131.62, 132.26, 132.35, J ) 12.0 Hz), 7.04 (d, 1H, J ) 7.5 Hz), 7.14 (dd, 1H, J ) 7.5
134.54, 135.03, 135.03, 135.61, 137.68, 137.73, 142.32, 142.52, Hz), 7.18-7.20 (m, 2H), 7.24-7.31 (m, 3H), 7.37-7.41 (m,
142.75 ppm. HRMS (MALDI): calcd for C38H26, 482.2; found, 2H), 7.49, (d, 1H, J ) 8.0 Hz) ppm. 13C NMR (CDCl3): δ
482.2 (M+). 0.22, 94.82, 105.48, 121.38, 127.12, 127.38, 127.68, 128.63,
1b: yield 88%, mp 262.9-264.4 °C. 1H NMR (CDCl3): δ 129.06, 129.12, 129.17, 129.24, 129.31, 131.40, 131.64, 131.73,
6.50 (s, 2H), 6.92-6.94 (m, 6H), 6.99 (d, 2H, J ) 12.0 Hz), 131.89, 134.49, 135.08, 137.34, 137.54, 142.39, 143.58 ppm.
7.14-7.30 (m, 4H), 7.27-7.20 (m, 10H), 7.39-7.43 (m, 4H), MS (ESI): m/z 377.0 ([M + H]+).
7.53 (d, 2H, J ) 7.5 Hz) ppm. 13C NMR (CDCl3): δ 126.33, 4-(Dibenzosuberenylidenemethyl)phenylacetylene (4) was
126.36, 127.14, 127.21, 127.53, 128.56, 129.01, 129.05, 129.11, also prepared from 3 by literature procedure17 in 95% yield.
129.35, 129.80, 131.40, 131.64, 132.07, 134.54, 135.13, 137.69, Mp 145.5-146.2 °C. 1H NMR (CDCl3): δ 3.04 (s, 1H) 6.47
138.85, 138.93, 142.61, 142.75 ppm. HRMS (MALDI): calcd (s, 1H), 6.85 (d, 2H, J ) 8.5 Hz), 6.92 (d, 1H, J ) 12.0 Hz),
for C44H30, 558.2; found, 558.2 (M+). 6.97 (d, 1H, J ) 12.0 Hz), 7.07 (d, 1H, J ) 7.5 Hz), 7.17 (dd,
19632 J. Phys. Chem. B, Vol. 109, No. 42, 2005 Wang et al.
1H, J ) 7.0 Hz), 7.21-7.24 (m, 2H), 7.26-7.32 (m, 3H), 7.38- 22.83, 23.93, 29.47, 30.23, 32.02, 40.58, 55.43, 90.18, 91.21,
7.42 (m, 2H), 7.50 (d, 1H, J ) 7.5 Hz) ppm. 13C NMR 120.15, 121.65, 122.19, 126.14, 127.13, 127.38, 127.70, 128.64,
(CDCl3): δ 77.80, 84.06, 120.44, 127.17, 127.48, 127.81, 129.07, 129.11, 129.18, 129.34, 129.42, 130.91, 131.32, 131.40,
128.70, 129.16, 129.21, 129.25, 129.31, 129.38, 131.44, 131.72, 131.67, 131.93, 134.51, 135.11, 137.26, 137.41, 140.87, 142.47,
131.80, 131.97, 134.53, 135.13, 137.34, 137.89, 142.43, 143.81 143.52, 151.32 ppm. HRMS (MALDI): calcd for C77H70, 994.5;
ppm. MS (ESI): m/z 304.9 ([M + H]+). found, 994.5 (M+.).
Synthesis of Compounds 5-6. 2,7-Bis(4-dibenzosuber- 3,6-Bis(4-dibenzosuberenylidenemethylphenyl)ethynyl-9-eth-
enylidenemethylphenyl)ethynyl-9,9′-diethylfluorene (5a). A mix- ylcabarzole (6) was prepared by a similar method as 5a in 78%
ture of 2,7-diiodo-9,9′-diethylfluorene (237 mg, 0.5 mmol), 4 yield. Mp 185.7-187.3 °C. 1H NMR (CDCl3): δ 1.42 (t, 3H,
(456 mg, 1.5 mmol), CuI (20 mg, 0.1 mmol), PPh3 (26.2 mg, J ) 7.0 Hz), 4.32 (q, 2H, J ) 7.0 Hz), 6.51 (s, 2H), 6.90 (d,
0.1 mmol), and Pd(PPh3)2Cl2 (10 mg, 0.013 mmol) in Et3N/ 4H, J ) 8.5 Hz), 6.94 (d, 2H, J ) 12 Hz), 7.00 (d, 2H, J ) 12
benzene (40/10 mL) was refluxed for 40 h. After cooling to Hz), 7.13 (d, 2H, J ) 7.5 Hz), 7.20 (dd, 2H, J ) 7.5 Hz), 7.29-
room temperature, the solvent was removed by evaporation. The 7.34 (m, 12H), 7.40-7.44 (m, 4H), 7.53 (d, 4H, J ) 7.5 Hz),
residue was purified by column chromatography as above. In 7.60 (d, 2H, J ) 8.0 Hz), 8.21 (s, 2H). 13C NMR (CDCl3): δ
this way, 330 mg of 5a was obtained in 80% yield as yellow 14.08, 38.08, 88.26, 91.39, 108.98, 114.19, 122.15, 122.82,
solid. Mp 146.3-147.8 °C. 1H NMR (CDCl3): δ 0.32 (t, 6H, 124.37, 127.16, 127.35, 127.69, 128.63, 129.11, 129.15, 129.18,
J ) 6.5 Hz), 2.03 (q, 4H, J ) 6.5 Hz), 6.52 (s, 2H), 6.91 (4H, 129.37, 129.41, 129.96, 131.23, 131.44, 131.66, 132.05, 134.53,
d, J ) 8.0 Hz), 6.94 (d, 2H, J ) 12.0 Hz), 7.01 (d, 2H, J ) 135.11, 136.85, 137.49, 140.14, 142.56, 143.28. HRMS (MAL-
12.0 Hz), 7.13 (d, 2H, J ) 7.5 Hz), 7.20 (dd, 2H, J ) 7.5 Hz), DI): calcd for C62H41N, 799.3; found, 799.3 (M+.).
7.30-7.32 (m, 10H), 7.41-7.55 (m, 10H), 7.65 (d, 2H, J ) 1,4-Bis(4-dibenzosuberenylidenemethylphenyl)buta-1,3-
8.0 Hz) ppm. 13C NMR (CDCl3): δ 8.59, 32.93, 56.48, 90.24, diyne (7). To a mixture of 4 (304 mg, 1 mol), Pd(PPh3)2Cl2 (10
91.13, 120.15, 121.64, 122.24, 126.25, 127.13, 127.39, 127.71, mg, 0.01 mmol), CuI (10 mg, 0.05 mmol), I2 (126 mg, 0.5
128.64, 129.09, 129.16, 129.18, 129.33, 129.43, 130.99, 131.33, mmol), and Et3N (20 mL) were added. The mixture was stirred
131.41, 131.67, 131.92, 132.24, 134.45, 134.50, 134.56, 135.09, at room temperature for 3 h and then poured into 50 mL of
137.25, 137.41, 141.27, 142.47, 143.52, 150.50 ppm, HRMS water with some sodium bisulfite. The mixture was extracted
(MALDI): calcd for C65H46, 826.4; found, 826.4 (M+.). by dichloromethane (20 mL × 3). Solvent was removed by
2,7-Bis(4-dibenzosuberenylidenemethylphenyl)ethynyl-9,9′- evaporation. The residue was purified by column chromatog-
dibutylfluorene (5b) was prepared by a similar method as 5a in raphy using n-hexane/dichloromethane to give 256 mg of 7
85% yield. Mp 133.8-135.2 °C. 1H NMR (CDCl3): δ 0.54- (yield, 85%). Mp 249.3-250.2 °C. 1H NMR (CDCl3): δ 6.47
0.60 (m, 4H), 0.67 (t, 6H, J ) 7.0 Hz), 1.07 (q, 4H, J ) 7.0 (s, 2H), 6.86 (d, 4H, J ) 8.0 Hz), 6.93 (d, 2H, J ) 12 Hz),
Hz), 1.94-1.97 (m, 4H), 6.51 (s, 2H), 6.90 (4H, d, J ) 8.0 6.98 (d, 2H, J ) 12 Hz), 7.09 (d, 2H, J ) 7.5 Hz), 7.19 (dd,
Hz), 6.94 (d, 2H, J ) 12.0 Hz), 7.00 (d, 2H, J ) 12.0 Hz), 2H, J ) 7.5 Hz), 7.23 (d, 4H, J ) 8.0 Hz), 7.28-7.33 (m, 6H),
7.40-7.43 (m, 4H), 7.52 (d, 2H, J ) 7.5 Hz). 13C NMR
7.11 (d, 2H, J ) 7.5 Hz), 7.18 (dd, 2H, J ) 7.5 Hz), 7.28-
(CDCl3): δ 74.49, 82.04, 119.80, 126.81, 127.18, 127.56,
7.32 (m, 10H), 7.41-7.48 (m, 8H), 7.53 (d, 2H, J ) 8.0 Hz),
128.38, 128.86, 128.93, 129.15, 131.10, 131.40, 131.99, 134.19,
7.63 (d, 2H, J ) 8.0 Hz) ppm. 13C NMR (CDCl3): δ 14.06,
134.77, 136.96, 137.99, 142.07, 143.84. HRMS (MALDI):
23.28, 26.40, 40.44, 55.36, 90.20, 91.19, 120.17, 121.63, 122.20,
calcd for C48H30, 606.2; found, 606.2 (M+.).
126.16, 127.13, 127.38, 127.70, 128.64, 129.08, 129.16, 129.19,
Film Preparation. In a typical experiment, a certain amount
129.34, 129.43, 130.92, 131.33, 131.41, 131.68, 131.92, 134.51,
of fluorophore was added into a certain volume of 10% PMMA
135.12, 137.28, 137.41, 140.88, 142.47, 143.53, 151.31 ppm.
in THF. Solids could be easily dissolved in this solution. The
HRMS (MALDI): calcd for C69H54, 882.4; found, 882.4 (M+.).
resulting mixture was pasted on the glass slide to produce a
2,7-Bis(4-dibenzosuberenylidenemethylphenyl)ethynyl-9,9′- wet film. The wet film was dried under atmosphere. By this
dihexanylfluorene (5c) was prepared by a similar method as 5a method, films could be fabricated, and the concentrations could
in 83% yield. Mp 119.0-121.0 °C. 1H NMR (CDCl3): δ 0.54- be controlled by the amounts of fluorophores.
0.60 (m, 4H), 0.76 (t, 6H, J ) 7.0 Hz), 1.0-1.04 (m, 8H), 1.10 Nanoparticle Preparation. Distilled water filtered by mem-
(m, 4H), 1.93-1.96 (m, 4H), 6.51 (s, 2H), 6.90 (4H, d, J ) 8.0 brance with 0.22 µm pore size was added dropwise into the
Hz), 6.93 (d, 2H, J ) 12.0 Hz), 6.99 (d, 2H, J ) 12.0 Hz), dilute solution of fluorophore in 1,4-dioxane with vigorous
7.11 (d, 2H, J ) 7.5 Hz), 7.18 (dd, 2H, J ) 7.5 Hz), 7.28- stirring at room temperature. In all cases, the concentrations of
7.33 (m, 10H), 7.40-7.47 (m, 8H), 7.52 (d, 2H, J ) 8.0 Hz), fluorophores were constant after distilled water was completely
7.62 (d, 2H, J ) 8.0 Hz) ppm. 13C NMR (CDCl3): δ 14.18, added. For the TEM observations, sample solutions were kept
22.80, 23.89, 29.89, 31.72, 40.58, 55.37, 90.13, 91.15, 120.11, for 10 days without stirring. Several drops of solution were place
121.58, 122.12, 126.08, 127.07, 127.32, 127.65, 128.58, 129.02, on a 200-mesh copper grid covered with a carbon film. Excess
129.10, 129.12, 129.27, 129.37, 130.85, 131.27, 131.35, 131.61, solutions were removed with filter paper. The resultant grid was
131.86, 134.44, 135.04, 137.19, 137.34, 140.81, 142.40, 143.47, air-dried for 5 h. The TEM micrographs were obtained on a
151.25 ppm. HRMS (MALDI): calcd for C73H62, 938.5; found, JEM-200CX instrument.
938.5 (M+.).
2,7-Bis(4-dibenzosuberenylidenemethylphenyl)ethynyl-9,9′- Acknowledgment. Ping Lu thanks National Nature Science
dioctanylfluorene (5d) was prepared by a similar method as 5a Foundation of China (20374045), Nature Science Foundation
in 87% yield. Mp 103.5-107.0 °C. 1H NMR (CDCl3): δ 0.53- of Zhejiang Province and Ministry of Education of China for
0.61 (m, 4H), 0.81 (t, 6H, J ) 7.0 Hz), 1.03-1.13 (m, 16H), financial support. Helpful discussion with Dr. F. M. Kong is
1.17-1.21 (m, 4H), 1.93-1.96 (m, 4H), 6.51 (s, 2H), 6.90 (d, greatly appreciated.
4H, J ) 8.0 Hz), 6.93 (d, 2H, J ) 11.5 Hz), 6.99 (d, 2H, J )
11.5 Hz), 7.11 (d, 2H, J ) 7.5 Hz), 7.18 (dd, 2H, J ) 7.5 Hz), Supporting Information Available: UV-vis absorption
7.28-7.30 (m, 10H), 7.40-7.48 (m, 8H), 7.53 (d, 2H, J ) 8.0 spectra and PL spectra of compounds in solutions, in thin films,
Hz), 7.63 (d, 2H, J ) 8.0 Hz) ppm. 13C NMR (CDCl3): δ 14.32, and in powders are available. Full characterizations (1H NMR,
Dibenzosuberenylidene-Ended Fluorophores J. Phys. Chem. B, Vol. 109, No. 42, 2005 19633
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