Double alkylene-strapped diphenylanthracene as a photostable and intense solid-state blue-emitting material

Article abstract of DOI:10.1021/jo302621k

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives 3a-c (a: C6 strap, b: C7 strap, c: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is pro

Full text of DOI:10.1021/jo302621k

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Double Alkylene-Strapped Diphenylanthracene as a Photostable and
Intense Solid-State Blue-Emitting Material
Yutaka Fujiwara,† Ryota Ozawa,† Daiki Onuma,† Kengo Suzuki,‡ Kenji Yoza,§ and Kenji Kobayashi*,†
†Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
‡Hamamatsu Photonics K. K., 812 Joko-cho, Higashi-ku, Hamamatsu 431-3196, Japan
§Bruker AXS, 3-9-B Moriya, Kanagawa-ku, Yokohama 221-0022, Japan
S
* Supporting Information
ABSTRACT: We report the synthesis and photochemical and
photophysical properties of double alkylene-strapped 9,10-diphenylan-
thracene derivatives 3a−c (a: C6 strap, b: C7 strap, c: C8 strap) in
which the reactive central aromatic ring of the anthracene moiety is
protected by the double alkylene straps. Thus, 3a−c were much more
resistant to photochemical reactions than the parent 9,10-diphenylan-
thracene (DPA). Furthermore, 3b in C6H12 as well as in a cast film and
the powder state showed the highest fluorescence quantum yields
among 3a, 3b, quadruple triethylsilyl-protected DPA 4, and DPA, wherein the C7 strap in 3b effectively serves to block
fluorescence self-quenching.
Chart 1. Structures of 1, 2, Double Alkylene-Strapped DPAs
3a−c, Quadruple Triethylsilyl-Protected DPA 4, and DPA
INTRODUCTION
■
Anthracene, 9,10-diphenylanthracene (DPA), and their deriv-
atives are highly fluorescent materials. They are useful building
blocks for optoelectronics such as organic electroluminescent
devices1 and two-photon absorption fluorescent dyes2 and for
organic semiconductors such as organic field-effect transistors3,4
and organic photoconductors.5 However, it is well-known that
anthracene derivatives react under photoirradiation to afford
photodimerization and/or photooxidation products.6 These
photochemical reactions of anthracene derivatives are dis-
advantageous for the purpose of uses related to photo-
luminescence and optoelectronics. Another problem of
anthracene derivatives is fluorescence self-quenching in the
solid state, caused by self-absorption with a small Stokes’ shift
and/or self-aggregation.7 Recently, two main strategies for
molecular designs to overcome these problems have been
reported. One is a supramolecular encapsulation strategy,8,9 and
the other is a steric protection strategy.7,8a Yamaguchi et al.
reported intense solid-state blue emission of a DPA derivative
by an intramolecular π-stacking protection based on steric
protection as well as rigidification of the conformation, which
would suppress the nonradiative decay process from the excited
state and make the radiative process more dominant.7 An
alkylene-strap method10−12 may be another effective and
simpler approach to steric protection as well as conformational
rigidification of DPA. Herein, we report the synthesis and
photochemical and photophysical properties of double
alkylene-strapped 9,10-diphenylanthracene (DPA) derivatives
3a−c (Chart 1; a, C6 strap; b, C7 strap; c, C8 strap) that are
resistant to photochemical reactions in solution and fluo-
rescence self-quenching in the solid state.
RESULTS AND DISCUSSION
■
Synthesis. Double alkylene-strapped DPAs 3a−c (a, C6
strap; b, C7 strap; c, C8 strap) were synthesized following a
four-step or three-step procedure (Scheme 1). The reaction of
anthraquinone with 2,6-dimethoxyphenyllithium13 followed by
the dehydroxy aromatization of the resulting diol with NaI−
NaH2PO2−AcOH14 or the Suzuki−Miyaura cross-coupling
reaction13 of 9,10-dibromoanthracene with 2,6-dimethoxyphe-
nylboronic acid gave 9,10-bis(2,6-dimethoxyphenyl)anthracene
Received: December 1, 2012
Published: January 16, 2013
© 2013 American Chemical Society
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a
Scheme 1. Synthesis of 1, 2, 3a−c, and 4
Figure 2. Molecular structures of (a) 3a, (b) 3b, (c) 3c, (d) 4, and (e)
DPA in the X-ray crystal structures. For 3a−c, two kinds of
conformers with different dihedral angles between the anthracene
and benzene rings exist in the unit cell,17 and each one of them is
shown here.
a
Key: (a) 2,6-dimethoxyphenyllithium, THF, −78 °C to rt; (b) NaI,
NaH2PO2·H2O, AcOH, 120 °C; (c) 2,6-dimethoxyphenylboronic acid,
Pd(OAc)2, SPhos,13 K3PO4, THF−H2O, 60 °C; (d) BBr3, CH2Cl2,
−78 °C to rt; (e) 1,n-Dibromoalkane (a: n = 6, b: n = 7, c: n = 8),
K2CO3, DMF, 40−80 °C; (f) Et3SiOTf, i-Pr2NEt, CH2Cl2, 0 °C to rt.
(1).15 The demethylation of 1 with BBr3 gave 9,10-bis(2,6-
dihydroxyphenyl)anthracene (2). Finally, the reaction of 2 with
1,n-dibromoalkanes (a, n = 6; b, n = 7; c, n = 8) in the presence
of K2CO3 afforded 3a, 3b, and 3c in 26%, 66%, and 55% yields,
respectively. The reaction of 2 with Et3SiOTf gave quadruple
triethylsilyl-protected DPA 4 in 82% yield.16
neither cofacial π-stacking nor herringbone packing structures
were observed, whereas DPA formed a herringbone-like
packing structure. The TG−DTA analysis indicated that
sublimation begins at around 300 °C for 1, 3a−c, and 4 and
at around 250 °C for DPA without thermal decomposition
(Figure S19, Supporting Information).17
UV−vis Absorption Spectra and DFT Calculations. The
UV−vis spectra of 1, 3a−c, and 4 in THF (or C6H12) were
similar to that of DPA (Figure S20, Supporting Information),17
wherein the longest wavelength absorption maxima (λmax(abs))
of 1, 3a−c, and 4 in THF (or C6H12) were only slightly red-
shifted by 0−4 (0−5) nm relative to the λmax(abs) of DPA
(Table S6, Supporting Information).17 DFT calculations at the
B3LYP/6-31G(d) level indicated that the introduction of the
double alkylene straps in DPA raises both the HOMO and
LUMO energy levels by 0.29 and 0.24 eV for 3a, 0.36 and 0.33
eV for 3b, and 0.25 and 0.21 eV for 3c relative to those of DPA
(Figure S21, Supporting Information).17 However, the
HOMO−LUMO gaps of 3a, 3b, and 3c were only slightly
reduced by 0.05, 0.03, and 0.04 eV, respectively, relative to that
of DPA.
1H NMR Spectra and X-ray Crystal Structures. Figure 1
shows the 1H NMR spectra of 3a−c, wherein the signals of the
1
Photostability. The photochemical stability of 1, 3a−c, 4,
and DPA was studied under the irradiation of an 18 W
fluorescent light (room light) or a 500 W ultrahigh-pressure
Figure 1. H NMR spectra of (a) 3a, (b) 3b, and (c) 3c in CDCl3.
1
C3H (C4H) of the alkylene strap for 3a, the C4H for 3b, and
the C4H (C5H) for 3c are shifted upfield by 1.33, 0.44, and
0.37 ppm, respectively, relative to those of the corresponding
1,n-alkanediols, attributable to the ring-current effect of the
anthracene ring of 3a−c. Finally, the molecular structures of
3a−c and 4 were confirmed by single-crystal X-ray diffraction
analyses (Tables S1−S5, Supporting Information).17 Figure 2
shows that the double alkylene straps in 3a−c protect the
reactive central aromatic ring of the anthracene moiety of DPA,
especially the 9,10-positions, and also rigidify the conformation
of the diphenyl groups on the DPA. For 4, quadruple
triethylsilyl groups overhang the anthracene moiety. The X-
ray packing structures of 3a−c, 4, and DPA18 are shown in
Figures S10−S18, Supporting Information.17 For 3a−c and 4,
mercury lamp and air in THF-d8 or THF, monitored by H
NMR (2 mM) or UV−vis absorption (0.04 mM) spectros-
copies.
1
Figure 3a shows plots of the H NMR signal integration
changes of 3b, 4, and DPA in THF-d8 upon exposure to air and
an 18 W fluorescent light. Parts Ab,c and Bb,c of Figure 4 also
show the 1H NMR spectra for the photochemical changes of 3b
and DPA, respectively, under the same conditions. The double
alkylene-strapped DPA 3b was extremely stable and remained
completely intact even after 10 days, and the quadruple
triethylsilyl-protected DPA 4 was also fairly stable and
remained 79% intact after 10 days. In marked contrast, DPA
completely disappeared and changed to the photooxidation
product, 9,10-endoperoxide, after 2 days (see also Figure S27B,
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1
Figure 3. (a) Plots of H NMR signal integration changes (Int−t/
Int−0) of 3b (purple), 4 (light blue), and DPA (blue) (2 mM each) in
THF-d8 as a function of irradiation time (days) upon exposure to air
and an 18 W fluorescent light. (b) Plots of the longest wavelength
absorption maxima changes (Abs−t/Abs−0) of 1 (green line), 3a (red),
3b (purple), 3c (orange), 4 (light blue), and DPA (blue) (0.04 mM
each) in THF as a function of irradiation time (hours) upon exposure
to air and light of a 500 W ultrahigh-pressure mercury lamp.
Supporting Information).6b,c Upon exposure to air and the light
of a 500 W ultrahigh-pressure mercury lamp, 3b in THF-d8
remained almost intact after 1 h (Figure 4Ad) and 56% intact
after 6 h irradiation (Figure 4Af). In contrast, DPA almost
completely changed to the 9,10-endoperoxide after 1 h (Figure
4Bd), which was completely decomposed to unidentified
products after 6 h irradiation (Figure 4Bf). Thus, 3b was
much more resistant to photochemical reactions than DPA,
based on the steric protection of the reactive central aromatic
ring of the anthracene moiety of 3b by the double alkylene
straps. The detailed 1H NMR spectral changes for the
photochemical reactions of 1, 3a−c, 4, and DPA (2 mM
each) in THF-d8 are shown in Figures S22−S27 (Supporting
Information).17
The photochemical stabilities of 1, 3a−c, 4, and DPA at high
dilution (0.04 mM in THF) upon exposure to air and the light
of a 500 W ultrahigh-pressure mercury lamp, monitored by
UV−vis absorption spectroscopy (Figure 3b and Figure S28,
Supporting Information),17 were somewhat different from the
results under higher concentration conditions (2 mM in THF-
d8) as mentioned above. At high dilution, the photooxidation of
DPA was slower because of reduced opportunities for
bimolecular reactions. The alkylene straps with ether bonds
in 3a−c proved to be not necessarily so robust and 3a−c were
completely decomposed to unidentified products after 6 h
irradiation. Nevertheless, 3a−c were much more resistant to
photochemical reactions than DPA. The photochemical
stability in air after 2 h irradiation by the light of a 500 W
ultrahigh-pressure mercury lamp was in the order DPA < 4 < 1
≈ 3a ≈ 3c < 3b (Figure 3b).
1
Figure 4. H NMR spectra for the photochemical changes of (A) 3b
and (B) DPA (2 mM in THF-d8) upon exposure to air and light:
irradiation of an 18 W fluorescent light for (a) 0 h, (b) 1 d, and (c) 10
d; irradiation of a 500 W ultrahigh-pressure mercury lamp for (d) 1 h,
(e) 3 h, and (f) 6 h.
Tables 1 and 2, respectively. The absolute fluorescence
quantum yields (ΦF) were determined by a calibrated
integrating sphere system.19 The fluorescence decays and
lifetimes (τs) were measured with a time-correlated single
photon counting fluorimeter.
In C6H12, the shortest and the second wavelength
fluorescence emission maxima (λmax(em)) of 1 and 3a−c
were only slightly blue-shifted relative to that of DPA (Figure
5a and Table 1). The Stokes’ shift values of 810, 860, 930,
1050, and 910 cm−1 of 1, 3a, 3b, 3c, and 4, respectively, were
slightly smaller than the 1230 cm−1 of DPA (Table S6,
Supporting Information),17 probably reflecting the degree of
their conformational rigidity between the anthracene ring and
the diphenyl groups at the 9,10-positions. The ΦF values in
C6H12 increased in the order 3a (ΦF = 0.93) ≤ 1 (0.94) ≤ 3c
(0.95) ≤ 4 (0.96) ≤ DPA (0.97)7,19 ≤ 3b (0.98) (Figure 6a
and Table 2).
There are four significant features in the fluorescence
properties of 1, 3a−c, 4, and DPA in the solid states (cast
film, powder, and single crystals).20,21
Item 1. In all cases, the λmax(em) values were red-shifted in
the order in C6H12 < cast film < powder < single crystals
Fluorescence Emission Properties. The fluorescence
spectra, absolute quantum yields (ΦF), lifetimes (τs), and
spectral data of 1, 3a−c, 4, and DPA in C6H12, cast film,
powder, and single crystals are shown in Figures 5 and 6a,b and
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Figure 6. (a) Fluorescence absolute quantum yields (ΦF) and (b)
fluorescence lifetimes (τs) of 1, 3a−c, 4, and DPA in C6H12 (blue),
cast film (red), powder (green), and single crystals (orange).
Table 1. Fluorescence Emission Maxima (λmax(em)) of 1,
3a−c, 4, and DPA in C6H12, Cast Film, Powder, and the
a
Single Crystals
λmax(em)/nm
in C6H12
λmax(em)/nm
in cast film
λmax(em)/nm
in powder
λmax(em)/nm
in crystals
compd
1
406, 425,
(449)
434, 454
436, 455
436, 460
3a
3b
3c
4
411, 429, 453 (417), 433, 459
409, 427, 451 (417), 433, 458
411, 429, 453 (415), 431, 457
413, 432, 457 (414), 431, 457
436, 460
436, 459
436, 457
433, 456
445, 463
441, 460
439, 457
439, 455
436, 455
453, 466
DPA 413, 430,
(456)
440, (466)
a
For sample preparations, see the Experimental Section.
Item 3. For 3a−c, in all solid states of cast film, powder, and
single crystals, the ΦF increased in the order 3c < 3a < 3b
(Figure 6a and Table 2). This result would be related to the
nature of the double alkylene straps: the C7 strap in 3b is not
tighter than the C6 strap in 3a, which may strain the excited
state of 3a, and is not looser than the C8 strap in 3c, which
would cause a thermal vibrational deactivation of the excited
state of 3c. In the cast film and the powder state, 3b showed the
highest ΦF of 0.87 and 0.93, respectively, among 1, 3a−c, 4,
and DPA. Thus, the C7 strap in 3b effectively blocks
fluorescence self-quenching. Surprisingly, in the single crystals,
DPA exhibited the highest ΦF among them of 0.95, whereas 3b
showed ΦF of 0.85. At this stage, it is not easy to elucidate the
reason for the paramount ΦF of DPA in the single crystals, and
we must wait for further studies.
Item 4. The τs values of 3a in the single crystals and of both
3b and DPA in the powder state and the single crystals
exceeded 11 ns; these values were greater than those in C6H12
(Table 2). In particular, 3b in the powder state and DPA in the
single crystals showed kf/knr = >10, indicating that the radiative
process is dominant, similar to that of the emission in C6H12.
Figure 5. Fluorescence emission spectra of 1 (green line), 3a (red), 3b
(purple), 3c (orange), 4 (light blue), and DPA (blue) in (a) C6H12,
(b) cast film, (c) powder, and (d) single crystals.
(Figure 5, Table 1, and Figure S29, Supporting Information),17
reflecting the exciton coupling in the condensed phase. The
difference between the shortest λmax(em) in the single crystals
and the second λmax(em) in C6H12 decreased in the order DPA
(Δλmax(em) = 23 nm) > 3a = 3b (12 nm) ≥ 1 (11 nm) ≥ 3c
(10 nm) > 4 (4 nm).22 This result reflects the difference in the
stacking mode between DPA and other derivatives because of
steric hindrance of the substituents at the 2′,6′-positions of the
diphenyl groups on DPA.
Item 2. Compounds 1 and 4 in the solid states showed low
ΦF. τs of 1 and 4 were shorter than those of 3a−c and DPA in
the respective solid state except for 3c in the powder state.
Furthermore, in contrast to 3a−c and DPA, the radiative rate
constants (kf) of 1 and 4 were smaller than their nonradiative
rate constants (knr) (Table 2 and Figure S30, Supporting
Information).17 These results would arise from a thermal
vibrational deactivation of the excited states of 1 and 4 with
flexible methoxy and triethylsilyloxy groups, respectively.
CONCLUSION
We have demonstrated the synthesis and photochemical and
photophysical properties of double alkylene-strapped 9,10-
■
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diphenylanthracene (DPA) derivatives 3a−c (a: C6 strap, b:
C7 strap, c: C8 strap). In 3a−c, the reactive central aromatic
ring of the anthracene moiety (especially the 9,10-positions of
the anthracene ring) is protected by the double alkylene straps.
Thus, 3a−c were much more resistant to photochemical
reactions than the parent DPA. The C7 strap in 3b was not
tighter than the C6 strap in 3a and was not looser than the C8
strap in 3c. This nature of the C7 strap reflects the chemical
yield, photostability, and fluorescence quantum yield (ΦF) of
3b. Thus, 3b exhibited the best performance for photostability
in solution and for ΦF in C6H12, a cast film, and the powder
state among 1, 3a−c, 4, and DPA investigated here, although
DPA exhibited the highest ΦF among them in single crystals.
The application of 3b as a building block for optoelectronics is
currently being studied.
EXPERIMENTAL SECTION
■
General Methods. THF and CH2Cl2 were distilled from sodium-
benzophenone ketyl and CaH2, respectively, under an argon
atmosphere. The other solvents and all commercially available reagents
1
were used without any purification. H and 13C NMR spectra were
recorded at 400 and 100 MHz, respectively. HRMS measurements
were performed by EI-TOF-MS. Photoirradiation was conducted with
a 500 W ultrahigh-pressure mercury lamp through a heat-absorbing
filter.
9,10-Bis(2,6-dimethoxyphenyl)anthracene (1). Method A. A
solution of 2,6-dimethoxyphenyllithium,13 which was prepared by the
reaction of 1,3-dimethoxybenzene (4.6 mL, 35.1 mmol) in dry THF
(80 mL) with a n-BuLi hexane solution (1.57 M, 22 mL, 34.5 mmol)
at 0 °C for 0.5 h and then at room temperature for 3 h under Ar, was
added to a suspension of anthraquinone (2.00 g, 9.61 mmol) in dry
THF (40 mL) at −78 °C under Ar. The reaction mixture was allowed
to warm to room temperature with stirring overnight and then
quenched with H2O (20 mL) and then 1 M HCl (40 mL) at 0 °C. The
precipitate was filtered and washed with H2O, MeOH, and EtOAc to
give 9,10-bis(2,6-dimethoxyphenyl)-9,10-dihydroxyanthracene (pre-1)
(4.48 g, 96% yield) as a white solid: 1H NMR (CDCl3, 50 °C) δ 7.35
(dd, J = 3.4 and 5.9 Hz, 4H), 7.21 (s, 2H), 7.20 (t, J = 8.3 Hz, 2H),
7.10 (dd, J = 3.4 and 5.9 Hz, 4H), 6.60 (d, J = 8.3 Hz, 4H), 3.62 (brs,
12H).
To a mixture of pre-1 (4.45 g, 9.18 mmol), NaI (9.65 g, 64.4
mmol), and NaH2PO2·H2O (9.73 g, 91.8 mmol) was added AcOH
(230 mL).14 The resulting mixture was stirred at 120 °C for 4 h under
Ar and light shielding. After the mixture was cooled to room
temperature, the precipitate was filtered and washed with H2O and
MeOH to give 1 (4.01 g, 97% yield) as a white solid: mp 287−288
°C;15 1H NMR (CDCl3) δ 7.62 (dd, J = 3.4 and 6.8 Hz, 4H), 7.51 (t, J
= 8.3 Hz, 2H), 7.27 (dd, J = 3.4 and 6.8 Hz, 4H), 6.83 (d, J = 8.3 Hz,
4H), 3.58 (s, 12H); 13C NMR (CDCl3) δ 159.1, 130.4, 129.9, 129.4,
126.7, 124.6, 116.0, 104.3, 56.0; HRMS (EI+) calcd for C30H26O4
450.1831, found 450.1841.
Method B. To a mixture of 9,10-dibromoanthracene (208 mg, 0.619
mmol), 2,6-dimethoxyphenylboronic acid (450 mg, 2.47 mmol),
Pd(OAc)2 (7.0 mg, 0.031 mmol), SPhos (12.8 mg, 0.031 mmol),13
and K3PO4 (527 mg, 2.48 mmol) under Ar were added THF (20 mL)
and H2O (3.2 mL). The resulting mixture was stirred at 60 °C for 69 h
under light shielding. After evaporation of solvents, the residue was
partitioned between CH2Cl2 and H2O. The organic layer was washed
with H2O and brine and dried over Na2SO4. After evaporation of
solvent, the residue was purified by column chromatography on silica
gel eluted with CH2Cl2−hexane (1:3) followed by reprecipitation with
CH2Cl2−hexane to give 1 (180 mg, 65% yield) as a white solid.
9,10-Bis(2,6-dihydroxyphenyl)anthracene (2). To a solution of
1 (2.59 g, 5.75 mmol) in dry CH2Cl2 (280 mL) at −78 °C under N2
and light shielding was added dropwise a solution of BBr3 (2.3 mL,
23.9 mmol) in dry CH2Cl2 (20 mL) over a period of 5 min. The
reaction mixture was allowed to warm to room temperature with
stirring overnight. After additional stirring at room temperature for 24
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h, the reaction mixture was poured into ice-cold water and neutralized
with NaHCO3. After evaporation of most of the CH2Cl2, the mixture
was extracted with EtOAc. The organic layer was washed with H2O
and brine and dried over Na2SO4. After evaporation of solvents, the
residue was purified by reprecipitation with THF−hexane to give 2
and DPA and from hexane−EtOH for 4. Single crystals were prepared
by recrystallization from a hot benzene−hexane solution for 1, 3a−c,
and DPA and recrystallization by slow diffusion of EtOH into a hexane
solution of 4. These manipulations were carried out under the
extinction of room light.
1
X-ray Data Collection and Crystal Structure Determination
of 3a−c, 4, and DPA. The data were measured by using a CCD area
detector, using Mo−Kα graphite monochromated radiation (λ =
0.71073 Å). The structures were solved by direct methods using the
program SHELXS-97.23 The refinements and all further calculations
were carried out by using SHELXL-97.23 The H-atoms were included
in calculated positions and treated as riding atoms by using the
SHELXL default parameters. The non-H atoms were refined
anisotropically, using weighted full-matrix least-squares on F2. Crystal
data and structure refinements are listed in Tables S1−S5 (Supporting
Information), and ORTEP views are shown in Figure S9 in the
Supporting Information. Crystallographic data (excluding structure
factors) for the structure in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary publication
nos. CCDC 911869 for 3a, CCDC 911870 for 3b, CCDC 911871 for
3c, CCDC 911872 for 4, and CCDC 911873 for DPA.
(2.00 g, 88% yield) as a pale yellow solid: mp 322 °C dec; H NMR
(DMSO-d6, 80 °C) δ 8.98 (s, 4H), 7.58 (dd, J = 3.4 and 6.8 Hz, 4H),
7.29 (dd, J = 3.4 and 6.8 Hz, 4H), 7.15 (t, J = 8.3 Hz, 2H), 6.57 (d, J =
8.3 Hz, 4H); 13C NMR (DMSO-d6, 80 °C) δ 156.9, 130.6, 130.1,
128.9, 126.8, 124.3, 111.9, 106.4; HRMS (EI+) calcd for C26H18O4
394.1205, found 394.1239.
Typical Procedure for the Synthesis of Double Alkylene-
Strapped Diphenylanthracenes (3): C7 Strap DPA (3b). To a
mixture of 2 (240 mg, 0.608 mmol) and K2CO3 (420 mg, 3.04 mmol)
were added DMF (120 mL) and 1,7-dibromoheptane (220 μL, 1.29
mmol). The reaction mixture was stirred at 40 °C for 24 h and then at
80 °C for 48 h under Ar and light shielding. After evaporation of
solvent, the residue was partitioned between CH2Cl2 and H2O. The
organic layer was washed with H2O and brine and dried over Na2SO4.
After evaporation of solvent, the residue was purified by column
chromatography on silica gel eluted with CH2Cl2−hexane (1:3)
followed by reprecipitation with CH2Cl2−hexane to give 3b (235 mg,
1
66% yield) as a white solid: mp 279−281 °C; H NMR (CDCl3) δ
ASSOCIATED CONTENT
* Supporting Information
■
7.65 (dd, J = 3.4 and 6.8 Hz, 4H), 7.46 (t, J = 8.3 Hz, 2H), 7.28 (dd, J
= 3.4 and 6.8 Hz, 4H), 6.86 (d, J = 8.3 Hz, 4H), 3.76 (t, J = 5.4 Hz,
8H), 1.10 (quint, J = 5.4 Hz, 8H), 0.60 (br quint, J = 6.8 Hz, 4H), 0.43
(quint, J = 7.3 Hz, 8H); 13C NMR (CDCl3) δ 159.0, 130.4, 130.1,
129.3, 126.8, 124.2, 119.5, 108.1, 69.9, 29.0, 27.8, 24.8; HRMS (EI+)
calcd for C40H42O4 586.3083, found 586.3056.
S
Additional spectral data of 1, 3a−c, 4, and DPA and ORTEP
views, crystal packing structures, and X-ray crystallographic data
(CIF) of 3a−c, 4, and DPA. This material is available free of
charge via the Internet at http://pubs.acs.org.
1
C6 Strap DPA (3a): white solid; 26% yield; mp 286−288 °C; H
AUTHOR INFORMATION
Corresponding Author
*E-mail: skkobay@ipc.shizuoka.ac.jp.
NMR (CDCl3) δ 7.68 (dd, J = 3.4 and 6.8 Hz, 4H), 7.47 (t, J = 8.3 Hz,
2H), 7.35 (dd, J = 3.4 and 6.8 Hz, 4H), 6.97 (d, J = 8.3 Hz, 4H), 3.61
(t, J = 5.4 Hz, 8H), 1.00 (quint, J = 5.4 Hz, 8H), 0.11 (br quint, J = 2.9
Hz, 8H); 13C NMR (CDCl3) δ 159.2, 130.3, 130.2, 129.7, 126.8,
125.0, 123.0, 113.2, 72.3, 30.1, 25.6; HRMS (EI+) calcd for C38H38O4
558.2770, found 558.2747.
■
Notes
The authors declare no competing financial interest.
1
C8 Strap DPA (3c): white solid; 55% yield; mp 277−279 °C; H
ACKNOWLEDGMENTS
This work was supported in part by a Grant-in-Aid from JSPS
(No. 22350060).
NMR (CDCl3) δ 7.64 (dd, J = 3.4 and 6.8 Hz, 4H), 7.45 (t, J = 8.3 Hz,
2H), 7.23 (dd, J = 3.4 and 6.8 Hz, 4H), 6.76 (d, J = 8.3 Hz, 4H), 3.85
(t, J = 5.4 Hz, 8H), 1.21 (m, 8H), 0.96 (m, 8H), 0.58 (m, 8H); 13C
NMR (CDCl3) δ 158.7, 130.3, 129.8, 129.1, 127.2, 123.9, 115.5, 104.0,
68.5, 28.8, 26.9, 23.4; HRMS (EI+) calcd for C42H46O4 614.3396,
found 614.3375.
■
REFERENCES
■
(1) (a) Kim, Y.-H.; Shin, D.-C.; Kim, S.-H.; Ko, C.-H.; Yu, H.-S.;
Chae, Y.-S.; Kwon, S.-K. Adv. Mater. 2001, 13, 1690−1693. (b) Hung,
L. S.; Chen, C. H. Mater. Sci. Eng., R 2002, 39, 143−222. (c) Kim, Y.-
H.; Jeong, H.-C.; Kim, S.-H.; Yang, K.; Kwon, S.-K. Adv. Funct. Mater.
2005, 15, 1799−1805. (d) Lyu, Y.-Y.; Kwak, J.; Kwon, O.; Lee, S.-H.;
Kim, D.; Lee, C.; Char, K. Adv. Mater. 2008, 20, 2720−2729.
(e) Vinyard, D. J.; Su, S.; Richter, M. M. J. Phys. Chem. A 2008, 112,
8529−8533. (f) Moorthy, J. N.; Venkatakrishnan, P.; Natarajan, P.;
Huang, D.-F.; Chow, T. J. J. Am. Chem. Soc. 2008, 130, 17320−17333.
(g) Nakanishi, W.; Hitosugi, S.; Piskareva, A.; Shimada, Y.; Taka, H.;
Kita, H.; Isobe, H. Angew. Chem., Int. Ed. 2010, 49, 7239−7242.
(2) (a) Yang, W. J.; Kim, C. H.; Jeong, M.-Y.; Lee, S. K.; Piao, M. J.;
Jeon, S.-J.; Cho, B. R. Chem. Mater. 2004, 16, 2783−2789. (b) Yang,
W. J.; Seo, M. S.; Wang, X. Q.; Jeon, S.-J.; Cho, B. R. J. Fluoresc. 2008,
18, 403−411. (c) Ji, S.; Wu, W.; Wu, W.; Guo, H.; Zhao, J. Angew.
Chem., Int. Ed. 2011, 50, 1626−1629.
9,10-Bis[2,6-bis(triethylsilyloxy)phenyl]anthracene (4). To a
suspension of 2 (180 mg, 0.456 mmol) in dry CH2Cl2 (12 mL) at 0 °C
under Ar and light shielding were added i-Pr2NEt (700 μL, 4.02
mmol) and Et3SiOTf (620 μL, 2.74 mmol). The reaction mixture was
stirred at 0 °C for 2 h and then at room temperature for 48 h. The
resulting mixture was quenched with H2O at 0 °C and extracted with
CH2Cl2. The organic layer was washed with H2O and brine and dried
over Na2SO4. After evaporation of solvent, the residue was purified by
column chromatography on silica gel eluted with CH2Cl2−hexane
(1:10) to give 4 (318 mg, 82% yield) as a white solid: mp 130−131
°C; 1H NMR (CDCl3) δ 7.67 (dd, J = 3.4 and 6.8 Hz, 4H), 7.28−7.20
(m, 6H), 6.68 (d, J = 8.3 Hz, 4H), 0.55 (t, J = 7.8 Hz, 36H), 0.35 (q, J
= 7.8 Hz, 24H); 13C NMR (CDCl3) δ 155.7, 130.2 (two coincident
resonances), 128.3, 127.5, 123.8, 121.2, 111.1, 6.3, 4.9; HRMS (EI+)
calcd for C50H74O4Si4 850.4664, found 850.4660.
Fluorescence Studies. The absolute fluorescence quantum yields
(ΦF) were determined by a calibrated integrating sphere system.19 The
fluorescence decays and lifetimes (τs) were measured with a time-
correlated single photon counting fluorimeter.
Before measurements, 1, 3a−c, 4, and DPA were purified by
column chromatography on silica gel, then by recycle preparative
HPLC using a polystyrene gel column, and finally by reprecipitation.
The sample preparation methods were as follows.21 In a N2-saturated
C6H12, the concentration was 1.0 × 10−5 M for 1 and 2.4 × 10−5 M for
3a−c, 4, and DPA. Drop cast films were prepared from one drop of a
100 μL microsyringe of a 1 mM CH2Cl2 solution of sample. Powders
were prepared by reprecipitation from CH2Cl2−hexane for 1, 3a−c,
(3) (a) Ito, K.; Suzuki, T.; Sakamoto, Y.; Kubota, D.; Inoue, Y.; Sato,
F.; Tokito, S. Angew. Chem., Int. Ed. 2003, 42, 1159−1162. (b) Meng,
H.; Sun, F.; Goldfinger, M. B.; Gao, F.; Londono, D. J.; Marshall, W. J.;
Blackman, G. S.; Dobbs, K. D.; Keys, D. E. J. Am. Chem. Soc. 2006,
128, 9304−9305. (c) Zhao, Q.; Kim, T. H.; Park, J. W.; Kim, S. O.;
Jung, S. O.; Kim, J. W.; Ahn, T.; Kim, Y.-H.; Yi, M. H.; Kwon, S.-K.
Adv. Mater. 2008, 20, 4868−4872.
(4) For FET property of DPA, see: (a) Tripathi, A. K.; Heinrich, M.;
Siegrist, T.; Pflaum, J. Adv. Mater. 2007, 19, 2097−2101. (b) Zhang,
X.; Yuan, G.; Li, Q.; Wang, B.; Zhang, X.; Zhang, R.; Chang, J. C.; Lee,
C.-S.; Lee, S.-T. Chem. Mater. 2008, 20, 6945−6950.
2211
dx.doi.org/10.1021/jo302621k | J. Org. Chem. 2013, 78, 2206−2212

The Journal of Organic Chemistry
Featured Article
(5) Marrocchi, A.; Silvestri, F.; Seri, M.; Facchetti, A.; Taticchia, A.;
Marks, T. J. Chem. Commun. 2009, 1380−1382.
(6) (a) Bouas-Laurent, H.; Castellan, A.; Desvergne, J.-P.;
Lapouyade, R. Chem. Soc. Rev. 2001, 30, 248−263. (b) Aubry, J.-M.;
Pierlot, C.; Rigaudy, J.; Schmidt, R. Acc. Chem. Res. 2003, 36, 668−
675. (c) Zehm, D.; Fudickar, W.; Linker, T. Angew. Chem., Int. Ed.
2007, 46, 7689−7692.
(7) Iida, A.; Yamaguchi, S. Chem. Commun. 2009, 3002−3004 and
references cited therein.
(8) For protection of photoreactive organic dyes and an anthracene
derivative by rotaxane encapsulations, see: (a) Frampton, M. J.;
Anderson, H. L. Angew. Chem., Int. Ed. 2007, 46, 1028−1064.
(b) Stone, M. T.; Anderson, H. L. Chem. Commun. 2007, 2387−2389.
(9) For protection of anthracene derivatives by the encapsulation in
self-assembled capsules, see: (a) Kaanumalle, L. S.; Gibb, C. L. D.;
Gibb, B. C.; Ramamurthy, V. J. Am. Chem. Soc. 2005, 127, 3674−3675.
(b) Nishimura, N.; Kobayashi, K. J. Org. Chem. 2010, 75, 6079−6085.
(10) For alkylene-strapped porphyrins, see: (a) Konishi, K.; Yahara,
K.; Toshishige, H.; Aida, T.; Inoue, S. J. Am. Chem. Soc. 1994, 116,
1337−1344. (b) Sugiyasu, K.; Takeuchi, M. Chem.Eur. J. 2009, 15,
6350−6362. (c) Lee, C.-H.; Galoppini, E. J. Org. Chem. 2010, 75,
3692−3704.
(11) For alkylene-strapped π-conjugated ladder polymers, see:
(a) Schluter, A.-D.; Loffler, M.; Enkelmann, V. Nature 1994, 368,
̈
̈
831−834. (b) Fiesel, R.; Huber, J.; Scherf, U. Angew. Chem., Int. Ed.
Engl. 1996, 35, 2111−2113.
(12) For double alkylene-strapped bithiophene and its polymer, see:
(a) Sugiyasu, K.; Honsho, Y.; Harrison, R. M.; Sato, A.; Yasuda, T.;
Seki, S.; Takeuchi, M. J. Am. Chem. Soc. 2010, 132, 14754−14756.
(b) Ouchi, Y.; Sugiyasu, K.; Ogi, S.; Sato, A.; Takeuchi, M. Chem.-
Asian J. 2012, 7, 75−84.
(13) Barder, T. E.; Walker, S. D.; Martinelli, J. R.; Buchwald, S. L. J.
Am. Chem. Soc. 2005, 127, 4685−4696.
(14) Kaur, I.; Miller, G. P. New J. Chem. 2008, 32, 459−463.
(15) Zweig, A.; Maurer, A. H.; Roberts, B. G. J. Org. Chem. 1967, 32,
1322−1329.
(16) The reaction of 2 with t-BuMe2SiOTf and i-Pr3SiOTf did not
produce quadruple trialkylsilyl-protected DPAs.
(17) See the Supporting Information.
(18) For the X-ray crystallographic analysis of DPA, see also:
(a) Langer, V.; Becker, H.-D. Z. Kristallogr. 1992, 199, 313−315. (b)
Reference 4.
(19) Suzuki, K.; Kobayashi, A.; Kaneko, S.; Takehira, K.; Yoshihara,
T.; Ishida, H.; Shiina, Y.; Oishi, S.; Tobita, S. Phys. Chem. Chem. Phys.
2009, 11, 9850−9860.
(20) For size dependence of fluorescence quantum yield in the
crystalline state, see: (a) Reference 7. (b) Katoh, R.; Suzuki, K.;
Furube, A.; Kotani, M.; Tokumaru, K. J. Phys. Chem. C 2009, 113,
2961−2965.
(21) The polarizing microscope observations suggested that the cast
film and powdery samples are amorphous or polycrystal. The quantum
yields in the cast film, powder state, and single crystals were
reproduced within
0.02 under the sample preparation conditions
mentioned in the Experimental Section.
(22) In all cases, the shortest λmax(em) in C6H12 were almost absent
in the solid states, as shown in Figure 5. A similar phenomenon is
known for DPA in C6H12, wherein the intensity of the shortest
λmax(em) of DPA in C6H12 decreases with increasing the
concentration.19
(23) Sheldrick, G. M. SHELXS-97 and SHELXL-97, University of
Gottingen, Gottingen, Germany, 1997.
̈
̈
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