Synthesis of carbazole-type D-π-A fluorescent dyes possessing solid-state red fluorescence properties

Article abstract of DOI:10.1002/ejoc.201200643

Carbazole-type donor-π-acceptor (D-π-A) fluorescent dyes (SO1 and SO2), each containing a diphenylamino system as an electron-donating group and a nitro moiety as an electron-accepting group, have been designed and synthesized, and their photophysical properties in solution and in the solid state have been investigated. The absorption and fluorescence properties of SO1 and SO2 in solution are similar, and both dyes exhibited moderate fluorescence quantum yields. In the solid state, however, the dye SO2, with a butyl substituent on the carbazole ring, exhibited red fluorescence at around 620 nm, whereas the dye SO1, with no substituent on the carbazole ring, did not exhibit these solid-state fluorescence properties. Furthermore, the dye SO2 exhibited weak mechanofluorochromic (MFC) properties: grinding of as-recrystallized dyes induces slight bathochromic shifts of the fluorescence excitation and emission maxima. To elucidate the effects of molecular and crystal structures on the solid-state fluorescence properties, we performed semiempirical molecular orbital calculations (PM3 and INDO/S) and single-crystal X-ray structural analysis. The X-ray crystal structures of SO1 and SO2 demonstrated that a continuous intermolecular π-stacking between the fluorophores was observable in the crystal structure of SO1, but not in that of SO2. The MO calculations revealed that SO1 and SO2 have similarly large dipole moments in the ground state (μ_g ≈ 8 D). The relationship between the observed solid-state photophysical properties and the molecular and crystal structures of the carbazole-type D-π-A fluorescent dyes are discussed on the basis of experimental results and MO calculations. It is found that the formation of a continuous intermolecular π-stacking between the fluorophores causes a drastic fluorescence quenching in the solid state and that D-π-A fluorescent dyes with very large dipole moments can reduce the MFC properties, due to strong dipole-dipole interactions between the fluorophores in the solid state. Copyright

Full text of DOI:10.1002/ejoc.201200643

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DOI: 10.1002/ejoc.201200643
Synthesis of Carbazole-Type D-π-A Fluorescent Dyes Possessing Solid-State
Red Fluorescence Properties
Yousuke Ooyama,*[a] Tetsuya Sugiyama,[a] Yuichiro Oda,[a] Yuta Hagiwara,[a]
Naoya Yamaguchi,[a] Eigo Miyazaki,[a] Hiroshi Fukuoka,[a] Tomonobu Mizumo,[a]
Yutaka Harima,[a] and Joji Ohshita*[a]
Keywords: Fluorescence / Dyes/pigments / Donor-acceptor systems / Carbazoles / Mechanofluorochromism /
Semiempirical calculations / Solid-state structures
Carbazole-type donor-π-acceptor (D-π-A) fluorescent dyes
(SO1 and SO2), each containing a diphenylamino system as
an electron-donating group and a nitro moiety as an elec-
tron-accepting group, have been designed and synthesized,
and their photophysical properties in solution and in the solid
state have been investigated. The absorption and fluores-
cence properties of SO1 and SO2 in solution are similar, and
both dyes exhibited moderate fluorescence quantum yields.
In the solid state, however, the dye SO2, with a butyl substit-
uent on the carbazole ring, exhibited red fluorescence at
around 620 nm, whereas the dye SO1, with no substituent on
the carbazole ring, did not exhibit these solid-state fluores-
cence properties. Furthermore, the dye SO2 exhibited weak
mechanofluorochromic (MFC) properties: grinding of as-
recrystallized dyes induces slight bathochromic shifts of the
fluorescence excitation and emission maxima. To elucidate
the effects of molecular and crystal structures on the solid-
state fluorescence properties, we performed semiempirical
molecular orbital calculations (PM3 and INDO/S) and single-
crystal X-ray structural analysis. The X-ray crystal structures
of SO1 and SO2 demonstrated that a continuous intermo-
lecular π-stacking between the fluorophores was observable
in the crystal structure of SO1, but not in that of SO2. The
MO calculations revealed that SO1 and SO2 have similarly
large dipole moments in the ground state (μg ≈ 8 D). The rela-
tionship between the observed solid-state photophysical
properties and the molecular and crystal structures of the carb-
azole-type D-π-A fluorescent dyes are discussed on the ba-
sis of experimental results and MO calculations. It is found
that the formation of a continuous intermolecular π-stacking
between the fluorophores causes a drastic fluorescence
quenching in the solid state and that D-π-A fluorescent dyes
with very large dipole moments can reduce the MFC proper-
ties, due to strong dipole–dipole interactions between the flu-
orophores in the solid state.
state fluorescence properties are closely associated with mo-
lecular packing structures, and many investigations into the
correlation between solid-state fluorescence properties and
molecular packing structures based on X-ray crystal struc-
tures have been conducted. It has been revealed that strong
intermolecular interactions such as π–π interaction and
intermolecular hydrogen bonding between neighboring flu-
orophores are principal factors affecting fluorescence
quenching in the solid state.[5–7] Consequently, the key point
in designing new strong solid-state emissive fluorophores is
to reduce the intermolecular interactions between fluoro-
phores leading to fluorescence quenching in molecular ag-
gregation states.
Introduction
Solid-state organic fluorescent dyes have received con-
siderable attention not only for fundamental use in solid-
state photochemistry research, but also for practical use in
the organic light-emitting diode (OLED) and optical sen-
sor[1–4] fields. In particular, the development of solid-state
blue-, green-, and red-emitting dyes is necessary for the fab-
rication of full-color OLED devices. However, organic fluo-
rescent dyes exhibiting strong fluorescence both in solution
and in the solid state are relatively uncommon, because
many organic fluorophores undergo fluorescence quench-
ing through molecular aggregation in the solid state. Solid-
In our previous study we reported the synthesis of vari-
ous types of novel heteropolycyclic donor-π-acceptor (D-π-
A) fluorescent dyes with substituents such as Me, Bu, Ph,
Bn, and 5-nonyl groups and their absorption and fluores-
cence properties in solution and in the solid state.[3,5,7] Dra-
matic substituent effects on the solid-state photophysical
properties were observed, and these have been elucidated
with the aid of X-ray crystallographic analysis. On the basis
[a] Department of Applied Chemistry, Graduate School of
Engineering, Hiroshima University
Higashi-Hiroshima 739-8527, Japan
Fax: +81-82-424-5494
E-mail: yooyama@hiroshima-u.ac.jp
jo@hiroshima-u.ac.jp
Homepage: http://home.hiroshima-u.ac.jp/orgmtrls/
Ohshita_Group/Ohshita_Group-Home.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200643.
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of this useful knowledge about the solid-state fluorescence electroluminescence devices. The dye SO2 exhibited weak
properties of D-π-A fluorescent dyes, we have achieved the mechanofluorochromic properties. To elucidate the effects
development of D-π-A fluorescent dyes exhibiting solid- of molecular and crystal structures on the solid-state fluo-
state blue or green fluorescence properties.[8]
rescence properties of these compounds we performed semi-
Organic fluorophores exhibiting strong solid-state red empirical molecular orbital calculations (PM3 and INDO/
emission, however, are rare.[9–11] Akkaya et al. reported the S) and single-crystal X-ray structural analysis. Here we dis-
solid-state red emissive BODIPY dyes with bulky substitu- cuss the relationship between the observed solid-state pho-
ents as spacers; introduction of bulky tert-butyl substituents tophysical properties and the molecular and crystal struc-
on the meso-phenyl groups results in more widely spaced tures of the carbazole-type D-π-A fluorescent dyes SO1 and
packing in the solid state, leading to highly luminescent SO2, on the basis of experimental results and MO calcula-
powders and films.[9] Chen et al., on the other hand, re- tions,.
ported that D-π-A fluorene derivatives with diarylamino
electron-donating groups, cyanovinyl electron-withdrawing
groups, and bulky 9,9-substituents (spiro-fused bifluorenes)
can effectively overcome the aggregation and so have high
solid-state red photoluminescence and electroluminescence
quantum efficiencies.[11] Therefore, in order to control the
solid-state fluorescence properties of organic fluorophores
better, it is necessary to obtain further useful information
about the effects of molecular and crystal structures on so-
lid-state fluorescence properties.
In order to develop organic fluorescent dyes possessing
solid-state red fluorescence properties, we have newly de-
signed and synthesized carbazole-type donor-π-acceptor
(D-π-A) fluorescent dyes (SO1 and SO2, Scheme 1, below),
each containing a diphenylamino system as an electron-do-
nating group and a nitro moiety as an electron-accepting
group, and have investigated their photophysical properties
in solution and in the solid state. The dye SO2, with a butyl
substituent on the carbazole ring, exhibited red fluores-
Results and Discussion
Synthesis of D-π-A Fluorescent Dyes SO1 and SO2
The carbazole-type D-π-A fluorescent dyes SO1 and
SO2 were synthesized according to the stepwise synthetic
protocol illustrated in Scheme 1. Compound 1 was pre-
pared from 4,4Ј-dibromo-2-nitrobiphenyl and 4-nitrophen-
ylboronic acid through Suzuki coupling. Buchwald–Hart-
wig C–N coupling of 1 with diphenylamine elded com-
pound 2, and Cadogan reductive cyclization of 2 gave the
dye SO1. The dye SO2 was prepared from SO1 and 1-iodo-
butane.
Photophysical Properties of SO1 and SO2 in Solution
The absorption and fluorescence spectroscopic data for
cence properties in the solid state, but the dye SO1, with no SO1 and SO2 in solution are summarized in Table 1, and
substituent on the carbazole ring, exhibited only feeble so- their spectra in 1,4-dioxane are shown in Figure 1. The ab-
lid-state fluorescence properties. Furthermore, we also in- sorption and fluorescence spectra of SO1 and SO2 re-
vestigated the mechanofluorochromic properties of SO1 semble each other very closely, showing that the effect of
and SO2. The recently discovered mechanofluorochromism N-alkylation of the carbazole ring on the photophysical
(MFC) is a change in fluorescent color induced by mechan- properties of the carbazole-type D-π-A fluorescent dyes is
ical stress on an organic crystal, accompanied by a rever- negligible. The dyes SO1 and SO2 each show two absorp-
sion to the original fluorescent color on heating or exposure tion maxima: one band, attributable to the local πǞπ*
to solvent vapor.[12–14] Mechanofluorochromic dyes have transition, appears at 310 nm, and the other, attributable
thus received considerable attention as a promising class of to intramolecular charge transfer (ICT) excitation from D
organic fluorescent dyes for rewritable photoimaging and (diphenylamino group) to A (nitrophenyl group), occurs at
Scheme 1. Synthesis of carbazole-type D-π-A fluorescent dyes SO1 and SO2.
2
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D-π-A Fluorescent Dyes with Solid-State Red Fluorescence Properties
around 400 nm. The corresponding fluorescence maxima SO2 in 1,4-dioxane are yellow, and the fluorescent colors
(λem) of SO1 and SO2 in 1,4-dioxane each occur at around of both dyes are yellowish-orange (Figure 2a, b).
580 nm, and the fluorescence quantum yields (ΦF) of SO1
and SO2 are 0.32 and 0.35, respectively. The absorption
Semiempirical MO Calculations (AM1, INDO/S)
maxima of the two dyes are almost independent of solvent
polarity, whereas the fluorescence maxima show large red-
shifts as the solvent polarity increases from 1,4-dioxane to
THF. The Stokes shift values in polar solvents therefore be-
come larger than those in nonpolar solvents. Moreover, sig-
nificant dependence of the fluorescence quantum yields on
the solvent polarity was also observed: the Φ values of SO1
and SO2 are reduced to ca. 13% (0.32 in 1,4-dioxane to
0.04 in THF) and 14% (0.35 in 1,4-dioxane to 0.05 in eth-
anol), respectively, with increasing polarity from 1,4-diox-
ane to THF (Table 1). The fluorescence of the two dyes was
strongly quenched in DMSO. The colors of both SO1 and
The photophysical properties of SO1 and SO2 were ana-
lyzed by means of semiempirical molecular orbital (MO)
calculations. The molecular structures were optimized by
the MOPAC/PM3 method,[15] and the INDO/S method[16]
was then used for spectroscopic calculations. The calculated
absorption wavelengths and the transition characters of the
absorption bands are listed in Table 2. The calculated ab-
sorption wavelengths and oscillator-strength values of the
two dyes are comparable to those observed in the spectra
in 1,4-dioxane; the effect of N-alkylation of the carbazole
ring on the photophysical properties of SO1 and SO2 is
negligible, consistent with the experimental results. The cal-
culations indicate that the longest excitation bands are
mainly attributable to the transition from HOMO to
LUMO, where the HOMO is mostly localized on the (di-
phenylamino)carbazole moiety, and the LUMO is mostly
localized on the nitrophenyl group. The HOMOs and
LUMOs of SO1 and SO2 are shown in Figure 3a and b.
The changes in the calculated electron density accompanied
by the first electron excitations for SO1 and SO2 are shown
Table 1. Spectroscopic properties of SO1 and SO2 in solution.
Dye
Solvent
λabs [nm]
λem [nm]
(ΦF)[a]
Stokes shift
(ε [m–1 cm–1])
νst [cm–1]
SO1 1,4-dioxane
THF
DMSO
SO2 1,4-dioxane
399 (31900)
400 (31800)
405 (23400)
399 (26000)
400 (29200)
405 (26400)
579 (0.32)
633 (0.04)
7791
9202
–
7791
9127
–
[b]
–
579 (0.35)
630 (0.04)
THF
DMSO
[b]
–
[a] Fluorescence quantum yields (Φf) were determined by use of a
calibrated integrating sphere system (λex = 400 nm). [b] Too weak.
Table 2. Calculated absorption spectroscopic data for SO1 and
SO2.
Compound
λmax [nm]
f[a]
CI component[b]
SO1
SO2
337
337
1.17
1.13
HOMOǞLUMO (41%)
HOMOǞLUMO (41%)
[a] Oscillator strength. [b] The transition is shown by an arrow from
one orbital to another, followed by its percentage CI (configuration
interaction) component.
Figure 1. Absorption and fluorescence spectra of SO1 and SO2 in
1,4-dioxane.
Figure 3. (a) HOMOs and (b) LUMOs of SO1 and SO2. The red
and blue lobes denote the positive and negative phases, respectively,
of the coefficients of the molecular orbitals. The size of each lobe is
proportional to the MO coefficient. (c) Calculated electron-density
changes accompanying the first electronic excitations of SO1 and
SO2. The black and white lobes signify decreases and increases,
respectively, in electron density accompanying the electronic transi-
tions. Their areas indicate the magnitudes of the electron-density
changes (light blue, green, blue, and red balls correspond to hydro-
gen, carbon, nitrogen, and oxygen atoms, respectively.).
Figure 2. Color (left) and fluorescence (right) images of (a) SO1
and (b) SO2 in 1,4-dioxane. Photographs of the solids of (c) SO1,
and (d) SO2 under room light (top) and under UV irradiation (bot-
tom) before and after grinding of as-recrystallized dyes.
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in Figure 3c and reveal a strong ICT nature from the (di- Table 3. Solid-state photophysical data for SO1 and SO2.
phenylamino)carbazole moiety to the nitrophenyl group
[a]
Dye
λex [nm]
λem [nm]
ΦF
upon light illumination. The values of the dipole moment
in the ground state (μg) are 7.6 D for both SO1 and SO2.
The differences between the dipole moments (Δμ) of the
first excited (HOMOǞLUMO) and the ground states are
17.5 D for SO1 and 17.9 D for SO2. These calculations
indicate that the dyes SO1 and SO2 have similarly large
dipole moments in their excited states, which explains our
finding that the two dyes show large redshifts in their fluo-
rescence maxima in polar solvents and that the Stokes shift
values for the two dyes in polar solvents are much larger
than those in nonpolar solvents.
[b]
SO1
SO2
557
549
564
618
618
625
–
0.03
0.03
SO2 (grinding)
[a] Fluorescence quantum yields (Φf) were determined by use of a
calibrated integrating sphere system (λex = 550 nm). [b] Too weak.
ex
dyes SO1 and SO2 in a mortar with a pestle, the λ
and
max
em
λ
values for SO2 are redshifted by 15 nm and 7 nm,
max
respectively (“grinding” in Table 3). However, no change in
the ΦF value was observed after grinding. The color and
fluorescent color changes of SO2 before and after grinding
of as-recrystallized dyes are shown in Figure 2d, and the
excitation and fluorescence spectral changes are also shown
in Figure 4. Unlike SO2, the dye SO1 did not exhibit ap-
Photophysical Properties of SO1 and SO2 in the Solid
State
ex
em
preciable changes in λ
or λ
after grinding (Figure 2c).
max
max
Figure 2c, d shows that the solid-state photophysical
properties of SO1 and SO2 are quite different from those
in solution. The dyes SO1 and SO2, when recrystallized
from mixed solvents (dichloromethane/n-hexane), were
orange and red solids, respectively. Interestingly, the dye
SO2 exhibited a red fluorescence emission in the solid state,
but the dye SO1 exhibited only feeble solid-state fluores-
cence properties. In order to investigate the difference in
the solid-state photophysical properties of the two dyes, we
measured the fluorescence excitation and emission spectra
of the crystals. As shown in Figure 4, the wavelengths of
the excitation and emission maxima of SO1 (λex = 557 nm,
λem = 618 nm) and of SO2 (λex = 549 nm, λem = 618 nm)
are redshifted, relative to those in 1,4-dioxane, by 158/
39 nm and 150/39 nm, respectively. The ΦF value of SO2 in
the solid state is 0.03, which is smaller than that in 1,4-
dioxane (Table 3). The precise evaluation of the Φ value of
SO1 was difficult, because the fluorescence of SO1 in the
solid state was strongly quenched. From this comparison of
photophysical properties between solution and solid state it
was found that the excitation and the emission maxima of
SO1 and SO2 in the crystalline state are greatly redshifted
relative to those in 1,4-dioxane, and the Φ values of the two
dyes in the crystalline state are much smaller than those in
1,4-dioxane.
Relationship between the Solid-State Photophysical
Properties and the Crystal Structures
To elucidate the effects of the molecular packing struc-
ture on the solid-state fluorescence properties, X-ray crystal
structures of SO1 and SO2 were determined. As shown in
Figure 5a, a continuous intermolecular π-stacking between
the fluorophores is observed in the crystal structure of SO1,
in which π-overlaps were observed between the nitrophenyl
group and the carbazole moiety in adjacent molecules. The
shortest distance for non-bonded overlapping atoms is
3.60 Å between N(1) and C(27)* (Figure 5b). The crystal
structure of SO2, on the other hand, is made up of dimer
units composed of pairs of fluorophores (Figure 6a). There
are 12 short interatomic contacts of less than 3.6 Å in a
pair of fluorophores, and the π-overlaps were observed over
the whole molecule from the nitrophenyl group to the carb-
azole moiety (Figure 6b). The interplanar distances are ca.
3.54 Å, which suggests intermolecular π–π interactions be-
tween the fluorophores in the dimer unit. The X-ray struc-
tural analysis therefore reveals that the formation either of
a continuous intermolecular π-stacking or of intermo-
lecular π–π interactions is responsible for large redshifts in
the absorption and fluorescence maxima and decreases in
the solid-state fluorescence for SO1 and SO2 on going from
1,4-dioxane to the solid state. However, the solid-state fluo-
rescence quantum yield of SO1 (ΦF ≈ 0) is much smaller
than that of SO2 (ΦF = 0.03). It was concluded that the
continuous intermolecular π-stacking between the fluoro-
phores is a principal factor leading to the drastic solid-state
fluorescence quenching of the crystal of SO1. These results
also show that the introduction of a bulky substituent on a
carbazole ring in a D-π-A fluorescent dye can effectively
prevent the formation of continuous intermolecular π-
stacking between fluorophores. On the other hand, for
MFC of D-π-A fluorescent dyes, our previous study had
Figure 4. Solid-state excitation (···) and emission (–) spectra of crys-
tals of SO1 and SO2 and of ground solid SO2.
Furthermore, the MFC characteristics of the carbazole- demonstrated that newly developed unsymmetrical hetero-
type D-π-A fluorescent dyes were investigated by the fol- polycyclic D-π-A fluorescent dyes with electron-with-
lowing procedure. After grinding of the as-recrystallized drawing substituents such as cyano and carboxylate ester
4
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D-π-A Fluorescent Dyes with Solid-State Red Fluorescence Properties
groups and thus relatively large dipole moments (μg ≈ 5– character (μg ≈ 8 D); that is, the strong dipole–dipole inter-
6 D) show pronounced MFC.[14] We ascribed the MFC to action between the fluorophores might inhibit a switching
reversible switching between crystalline and amorphous between crystalline and amorphous states on grinding.
states with changes in dipole–dipole interaction and inter-
molecular π–π interaction. Indeed, powder XRD measure-
ments with as-recrystallized SO2 exhibited diffraction
peaks attributable to a well-defined microcrystalline struc-
ture. These almost disappeared after grinding, indicating
that the crystal lattice was significantly disrupted (see the
Supporting Information). It was thus suggested that the
weak MFC for SO2 is attributable to the very large dipole
Conclusions
We have designed and synthesized carbazole-type D-π-A
fluorescent dyes (SO1 and SO2), each containing a di-
phenylamino system as an electron-donating group and a
nitro moiety as an electron-accepting group, as organic flu-
orescent dyes displaying solid-state red fluorescence proper-
ties. The dye SO2, with a butyl substituent on the carbazole
ring, exhibited red fluorescence emission in the solid state,
but the dye SO1, with no substituent on the carbazole ring,
did not exhibit solid-state fluorescence properties. Further-
more, the dye SO2 exhibited weak MFC properties. From
MO calculations and single-crystal X-ray structural analysis
it was found that the formation of continuous intermo-
lecular π-stacking between the fluorophores causes drastic
fluorescence quenching in the solid state and that very large
dipole moments can reduce the MFC properties of D-π-A
fluorescent dyes, due to strong dipole–dipole interactions
between the fluorophores in the solid state. This study also
demonstrates that the introduction of a bulky substituent
on the carbazole ring of such a D-π-A fluorescent dye can
effectively prevent the formation of continuous intermo-
lecular π-stacking between fluorophores.
Experimental Section
General: Melting points were measured with a Yanaco micro melt-
ing point apparatus MP model. IR spectra were recorded with a
Perkin–Elmer Spectrum One FT-IR spectrometer by the ATR
method. High-resolution mass spectrometric data were acquired
Figure 5. (a) Crystal packing and (b) continuous intermolecular π-
stacking of SO1. Dotted lines and circles show the non-bonded
overlapping atoms between N(1) and C(27)*.
1
with a Thermo Fisher Scientific LTQ Orbitrap XL instrument. H
NMR spectra were recorded with a Varian-400 (400 MHz) or a
Varian-500 (500 MHz) FT NMR spectrometer. Absorption spectra
were obtained with a Hitachi U-2910 spectrophotometer, and fluo-
rescence spectra were measured with a Hitachi F-4500 spectropho-
tometer. The fluorescence quantum yields in solution and in the
solid state were determined with a Hamamatsu C9920-01 instru-
ment equipped with CCD by use of a calibrated integrating sphere
system. Powder X-ray diffraction measurements were performed
with a Bruker D8 diffractometer and use of Cu-Kα radiation.
4-Bromo-2Ј,4ЈЈ-dinitro-1,1Ј:4Ј,1ЈЈ-terphenyl (1): Aqueous Na2CO3
(1 m, 2.5 mL) and DMF (10 mL) were added under argon to a mix-
ture of 4,4Ј-dibromo-2-nitrobiphenyl (1.07 g, 3.00 mmol), 4-ni-
trophenylboronic acid (500 mg, 3.00 mmol), and Pd(PPh3)4
(243 mg, 0.21 mmol), and the mixture was stirred at 90 °C for 18 h.
After concentration under reduced pressure, the resulting residue
was dissolved in dichloromethane and washed with water. The resi-
due was chromatographed on silica gel (dichloromethane/hexane,
4:1, as eluent) to give 1 (687 mg, yield 57%) as a yellow solid. M.p.
170–172 °C. 1H NMR (400 MHz, CDCl3): δ = 7.23 (d, J = 8.8 Hz,
2 H), 7.56 (d, J = 8.0 Hz, 1 H), 7.60 (d, J = 8.8 Hz, 2 H), 7.81 (d,
J = 9.2 Hz, 2 H), 7.89 (dd, J = 2.0, 8.0 Hz, 1 H), 8.14 (d, J =
2.0 Hz, 1 H), 8.38 (d, J = 9.2 Hz, 2 H) ppm. 13C NMR (500 MHz,
CDCl3): δ = 123.05, 123.1, 124.5, 128.0, 129.5, 131.0, 132.0, 132.7,
Figure 6. (a) Crystal packing and (b) dimer unit of SO2. Dotted
circles show the short interatomic contacts of less than 3.6 Å in a
pair of fluorophores.
135.4, 135.5, 139.4, 144.3, 147.9, 149.5 ppm. IR (ATR): ν = 1527,
˜
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1510, 1344 cm–1. HRMS (APCI): calcd. for C18H11BrN2O4 [M]–·
397.9908; found 397.9905.
EF). Experimental absorption spectra of the compounds were com-
pared with their absorption data by the semiempirical method
INDO/S (intermediate neglect of differential overlap/spectro-
scopic).[16] Dipole moments of the compounds were also evaluated
from INDO/S calculations. All INDO/S calculations were per-
formed by use of single excitation full SCF/CI (self-consistent field/
configuration interaction), which included the configurations with
one electron excited from any occupied orbital to any unoccupied
orbital, with 225 configurations considered [keyword CI (15 15)].
(2Ј,4ЈЈ-Dinitro-1,1Ј:4Ј,1ЈЈ-terphenyl-4-yl)diphenylamine (2): Toluene
(300 mL) was added under argon to a mixture of 1 (4.61 g,
11.54 mmol) and diphenylamine (3.91 g, 23.08 mmol), together
with Pd(OAc)2 (130 mg, 0.577 mmol),(tBu3P (10 wt.-% in n-hexane,
2.42 g, 1.20 mmol), and tBuONa (1.39 g, 14.48 mmol), and the
mixture was stirred at 100 °C for 21 h. After concentration under
reduced pressure, the resulting residue was dissolved in dichloro-
methane and washed with water. The residue was chromatographed
on silica gel (dichloromethane/hexane, 1:3, as eluent) to give 2
X-ray Crystallographic Studies: The reflection data were collected
at 23 Ϯ1 °C with a Rigaku RAXIS-RAPID Imaging Plate dif-
fractometer and use of graphite-monochromated Mo-Kα radiation
(λ = 0.71075 Å) at 50 kV and 40 mA. In all cases the data were
corrected for Lorentz and polarization effects. All calculations were
performed by use of the teXsan[17] crystallographic software pack-
age from Molecular Structure Corporation. CCDC-878842 (for
SO1) and -878843 (for SO2) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.au.uk/data_request/cif.
1
(4.85 g, yield 86%) as a dark orange powder. M.p. 183–186 °C. H
NMR (400 MHz, CDCl3): δ = 7.06–7.11 (m, 4 H), 7.15–7.21 (m, 6
H), 7.28–7.32 (m, 4 H), 7.61 (d, J = 8.0 Hz, 1 H), 7.80 (d, J =
9.2 Hz, 2 H), 7.85 (dd, J = 2.0, 8.0 Hz, 1 H), 8.05 (d, J = 2.0 Hz,
1 H), 8.37 (d, J = 9.2 Hz, 2 H) ppm. 13C NMR (500 MHz, CDCl3):
δ = 122.3, 122.8, 123.6, 124.5, 125.1, 127.8, 128.7, 129.1, 129.4,
130.6, 132.6, 136.1, 138.3, 144.6, 147.2, 147.7, 148.4, 149.7 ppm.
IR (ATR): ν = 1518, 1488, 1346 cm–1. HRMS (APCI): calcd. for
˜
C30H21N3O4 [M + H]+ 488.1605; found 488.1606.
[7-(4-Nitrophenyl)carbazol-2-yl]diphenylamine (SO1): o-Dichloro-
benzene (16 mL) was added under argon to a mixture of 2 (4.00 g,
8.21 mmol) and PPh3 (5.38 g, 20.51 mmol), and the mixture was
stirred at 160 °C for 18 h. After concentration under reduced pres-
sure, the residue was chromatographed on silica gel (dichlorometh-
ane/hexane, 3:1, as eluent) to give SO1 (1.69 g, yield 45%) as an
orange solid. M.p. 239–241 °C. 1H NMR (500 MHz, [D6]acetone):
δ = 6.96 (dd, J = 1.0, 8.5 Hz, 1 H), 7.04–7.07 (m, 2 H), 7.12 (d, 4
H), 7.17 (d, J = 1.0 Hz, 1 H), 7.31 (t, 4 H), 7.61 (dd, J = 1.0,
8.0 Hz, 1 H), 7.89 (d, J = 1.0 Hz, 1 H), 8.04 (d, J = 8.5 Hz, 2 H),
8.07 (d, J = 8.5 Hz, 1 H), 8.19 (d, J = 8.0 Hz, 1 H), 8.35 (d, J =
8.5 Hz, 2 H), 10.36 (s, 1 H, NH) ppm. 13C NMR (500 MHz, [D6]-
acetone): δ = 107.2, 110.3, 117.8, 119.2, 119.4, 121.0, 121.9, 123.6,
124.67, 124.74, 124.9, 128.6, 130.1, 135.9, 141.8, 142.9, 147.5,
Crystal Data of SO1: Crystals of SO1 were recrystallized from a
mixed dichloromethane/n-hexane solvent system as orange plates
(air-stable). The crystal structure was solved by direct methods with
use of SIR 92.[18] The structures were expanded by use of Fourier
techniques.[19] The non-hydrogen atoms were refined anisotropi-
cally. Some hydrogen atoms were refined isotropically; the rest were
fixed geometrically and not refined. Crystallographic data:
C30H21N3O2, M = 455.50, orthorhombic, a = 7.678(4), b =
13.231(8), c = 22.582(13) Å, V = 2294(2) Å3, ρcalcd. = 1.319 gcm–3,
T = 296.2 K, space group P212121 (no. 19), Z = 4, 17092 reflections
measured, 5214 unique (Rint = 0.045), which were used in all calcu-
lations; final R indices [IϾ2σ(I)]: R1 = 0.050, wR(F2) = 0.1356;
GOF = 0.96.
Crystal Data of SO2: Crystals of SO2 were recrystallized from a
mixed dichloromethane/n-hexane solvent system as red prisms (air-
stable). The crystal structure was solved by direct methods with
use of SIR 92.[18] The structures were expanded by use of Fourier
techniques.[19] The non-hydrogen atoms were refined anisotropi-
cally. Some hydrogen atoms were refined isotropically; the rest were
fixed geometrically and not refined. Crystallographic data:
C34H29N3O2, M = 511.62, monoclinic, a = 22.627(6), b = 8.805(3),
147.7, 149.06, 149.14 ppm. IR (ATR): ν = 1488, 1334 cm–1. HRMS
˜
(APCI): calcd. for C30H21N3O2 [M + H]+ 456.1707; found
456.1702.
[9-Butyl-7-(4-nitrophenyl)carbazol-2-yl]diphenylamine (SO2):
A
solution of SO1 (1.00 g, 2.20 mmol), 1-bromobutane (0.53 mL,
5.49 mmol), KOH (0.203 g, 3.62 mmol), and Bu4NBr (1.12 g,
2.20 mmol) in toluene (100 mL) was stirred under reflux for 3 h.
After concentration under reduced pressure, the resulting residue
was dissolved in dichloromethane and washed with water. The resi-
due was chromatographed on silica gel (dichloromethane/hexane,
3:1, as eluent) to give SO2 (1.02 g, yield 91%) as a red solid. M.p.
208–211 °C. 1H NMR (400 MHz, [D6]acetone): δ = 0.84 (t, J =
7.6 Hz, 3 H), 1.26–1.32 (m, 2 H), 1.76–1.80 (m, 2 H), 4.38 (t, J =
8.0 Hz, 2 H), 6.95 (dd, J = 2.0, 8.4 Hz, 1 H), 7.04–7.08 (m, 2 H),
7.12–7.14 (m, 4 H), 7.25 (d, J = 2.0 Hz, 1 H), 7.29–7.34 (m, 4 H),
7.63 (dd, J = 1.6, 8.4 Hz, 2 H), 7.99 (d, J = 1.6 Hz, 1 H), 8.07 (d,
J = 8.4 Hz, 1 H), 8.10 (d, J = 9.2 Hz, 2 H), 8.21 (d, J = 8.4 Hz, 1
H), 8.35 (d, J = 9.2 Hz, 2 H) ppm. 13C NMR (500 MHz, [D6]-
acetone): δ = 14.1, 20.9, 31.8, 43.0, 105.9, 108.7, 117.9, 119.0, 119.4,
121.2, 122.2, 123.6, 124.3, 124.8, 124.8, 128.9, 130.2, 136.2, 142.4,
c
= 27.315(9) Å, β = 94.77(1)°, V = =
5423(2) Å3, ρcalcd.
1.253 gcm–3, T = 296.2 K, space group C2/c (no. 15), Z = 8, 20576
reflections measured, 4842 unique (Rint = 0.040), which were used
in all calculations; final R indices [IϾ2σ(I)]: R1 = 0.083, wR(F2) =
0.318; GOF = 1.33.
Supporting Information (see footnote on the first page of this arti-
1
cle): H and 13C NMR spectra and powder X-ray diffraction data.
Acknowledgments
This work was supported by the Japan Society for the Promotion
of Science (JSPS) [Grants-in-Aid for Scientific Research (B)
(23350097) and (C) (24550225)]. Y. O. also acknowledges the DIC
Award in Synthetic Organic Chemistry, Japan.
143.4, 147.7, 147.8, 149.1, 149.3 ppm. IR (ATR): ν = 1492,
˜
1339 cm–1. HRMS (APCI): calcd. for C34H29N3O2 [M + H]+
512.2333; found 512.2331.
Computational Methods: The semiempirical calculations were car-
ried out with the WinMOPAC Version 3.9 package (Fujitsu, Chiba,
Japan). Geometry calculations in the ground state were performed
by the PM3 method.[15] All geometries were completely optimized
(keyword PRECISE) by the eigenvector following routine (keyword
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Received: May 14, 2012
Published Online: ᭿
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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7

Job/Unit: O20643
/KAP1
Date: 25-07-12 15:47:08
Pages: 8
Y. Ooyama, J. Ohshita et al.
FULL PAPER
Solid-State Red Fluorescence
Carbazole-type donor-π-acceptor (D-π-A)
fluorescent dyes (SO1 and SO2) each con-
taining a diphenylamino system as an elec-
tron-donating group and a nitro moiety as
an electron-accepting group have been de-
signed and synthesized, and their photo-
physical properties in solution and in the
solid state have been investigated.
Y. Ooyama,* T. Sugiyama, Y. Oda,
Y. Hagiwara, N. Yamaguchi, E. Miyazaki,
H. Fukuoka, T. Mizumo, Y. Harima,
J. Ohshita* ....................................... 1–8
Synthesis of Carbazole-Type D-π-A Fluor-
escent Dyes Possessing Solid-State Red
Fluorescence Properties
Keywords: Fluorescence / Dyes/pigments /
Donor-acceptor systems
Mechanofluorochromism /
/
Carbazoles
/
Semiempirical calculations
structures
/
Solid-state
8
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