2,6-Bis(arylsulfonyl)anilines as fluorescent scaffolds through intramolecular hydrogen bonds: Solid-state fluorescence materials and turn-on-type probes based on aggregation-induced emission

Article abstract of DOI:10.1002/cplu.201300428

A series of 2,6-bis[aryl(alkyl)sulfonyl]anilines were synthesized by nucleophilic aromatic substitution of 2,6-dichloronitrobenzene with various aryl or alkyl thiolates (benzyl-, phenyl-, 2-naphthyl-, and 2-aminophenyl thiolate), followed by hydrogenation

Full text of DOI:10.1002/cplu.201300428

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DOI: 10.1002/cplu.201300428
2,6-Bis(arylsulfonyl)anilines as Fluorescent Scaffolds
through Intramolecular Hydrogen Bonds: Solid-State
Fluorescence Materials and Turn-On-Type Probes Based on
Aggregation-Induced Emission
Teruo Beppu, So Kawata, Naoya Aizawa, Yong-Jin Pu, Yasuyuki Abe,* Yoshihiro Ohba, and
Hiroshi Katagiri*[a]
A series of 2,6-bis[aryl(alkyl)sulfonyl]anilines were synthesized
by nucleophilic aromatic substitution of 2,6-dichloronitroben-
zene with various aryl or alkyl thiolates (benzyl-, phenyl-, 2-
naphthyl-, and 2-aminophenyl thiolate), followed by hydroge-
nation and subsequent oxidation. All prepared 2,6-bis-
[aryl-(alkyl)sulfonyl]anilines showed high fluorescence emis-
sions in the solid state; X-ray structures revealed well-defined
intramolecular hydrogen bonds, which served to immobilize
the rotatable amino group and generate a fluorescence en-
hancement in addition to improved photostability. Moreover,
absorption and fluorescence spectra showed redshifts in the
order of benzyl<phenyl<2-naphthyl in solution and the solid
state, and DFT calculations confirmed charge transfer from the
central aniline unit to the side aryl groups through the sulfonyl
bridges, which together indicated the push–pull effect with an
extended p-conjugated system comprising the 2,6-bis(arylsul-
fonyl)aniline unit. Furthermore, 2,6-bis(2-aminophenylsulfony-
l)aniline, with rotatable amino groups at the flanking aryl units,
was affected by fluorescence quenching in solution. This none-
missive state showed an enhanced environmental sensitivity to
solvent polarity and viscosity, along with a “turn-on” fluores-
cence response in frozen solvent and in the aggregated form.
2,6-Bis(2-aminophenylsulfonyl)aniline behaved as a turn-on
fluorescence probe for selective detection of DNA based on its
aggregation-induced emission.
Introduction
Organic luminophores have been widely studied for decades
and have been used in a variety of applications in which lumi-
nescence is desired.[1,2] In particular, although organic lumines-
cence has been extensively studied in solution for lumino-
phores in the monomeric form, the search for materials for
solid-state emissions has increased in importance for various
optoelectronic applications, such as organic light-emitting
diodes (OLEDs)[3] and dye lasers.[4,5] Aggregation-induced emis-
sion (AIE) has been recently utilized in advanced applications
by using the concept of a “turn-on” luminescence response in
chemosensors and bioprobes.[6] The underlying principle for
the observation of most organic luminophores in dilute condi-
tions is based on a molecular design that employs a flat and
rigid framework for effective extension of the p-conjugation
system. The p stacking of molecules at high concentrations
and in the solid state leads to subsequent quenching and low-
ered photosensitivity through intermolecular energy-transfer
processes;[7] a phenomenon widely known as “concentration
quenching,” which imposes limits on the effective application
of fluorescent probes and electroluminescent devices. In re-
sponse to this problem, the use of a bulky group or twisted
molecular geometry has been recently introduced to prevent
the intermolecular stacking of luminophores and generate
a solid-state emission.[8] This concept relies on the presence of
twisted rotatable bonds; in solution, free bond rotation ren-
ders the molecules nonemissive, whereas immobilization of
the relevant bonds in aggregation gives rise to emissive prop-
erties, which produce desirable phenomena, such as a turn-on
type of probe response.[6a,9,10] Therefore, unsurprisingly, the
design and synthesis of conceptually new scaffolds for solid-
state luminescence materials is a central research topic in
chemistry and materials science.
[a] T. Beppu, S. Kawata, N. Aizawa, Prof. Dr. Y.-J. Pu, Prof. Dr. Y. Abe,
Prof. Dr. Y. Ohba, Prof. Dr. H. Katagiri
Graduate School of Science and Engineering
Yamagata University, 4-3-16 Jonan, Yonezawa
Yamagata 992-8510 (Japan)
We report herein the preparation of 2,6-bis(arylsulfonyl)ani-
line (BArSA) as a novel scaffold for luminophores (Scheme 1).
The concept of the molecular design includes the following
two unique points for enhancement of the fluorescence prop-
erties: 1) barriers to rotation of amino groups are accom-
plished through intramolecular hydrogen-bonds motifs, and
2) amino and sulfonyl moieties are employed to improve fluo-
rescence through enhanced push–pull and p-conjugation ef-
Fax: (+81)238-26-3743
E-mail: y-abe@yz.yamagata-u.ac.jp
kgri7078@yz.yamagata-u.ac.jp
Supporting information for this article is available on the WWW under
1
http://dx.doi.org/10.1002/cplu.201300428. It contains H and 13C NMR
spectroscopy data, HRMS data for all new compounds, UV/Vis and fluo-
rescence spectra, MO calculation details, powder XRD data, and X-ray
crystallographic data and crystallographic files.
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Scheme 1. Schematic representation of the BArSAs: a) a comparison of the
structural properties between julolidine and BArSAs, and b) the similarity in
resonance forms between the arylsulfonyl moiety and the amide bond.
Scheme 2. Synthetic route to BArSA derivatives.
Validation of intramolecular hydrogen-bond formation
fects. On the first point, although the presence of an amino
group strongly increases the HOMO level of p-conjugated mol-
ecules by an electron-donating effect, the freely rotating CÀN
bond is not conducive to fluorescence owing to vibrational
quenching. This problem is addressed by employing a julolidine
framework, in which the amino group is made rigid by cova-
lent bonds; a strategy that has been widely used in fluorescent
architectures (e.g., Texas Red) to increase quantum yields and
enhance stabilities (Scheme 1a).[11] In contrast, the amino
group of BArSA is rigidified by intramolecular hydrogen bonds
in a similar manner to the structural immobilization of juloli-
dine, which is schematically represented in comparison to the
conjugation system of an amide bond in Scheme 1b. On the
second point, push–pull systems have also been applied to
a variety of luminophores because of marked increases in ob-
served molar extinction coefficients and longer wavelengths.[12]
The amino and sulfonyl groups of BArSAs would function as
strong electron donors and acceptors, respectively, to allow
the creation of an effective push–pull system.
The presence of intramolecular hydrogen bonds, which are the
key component theorized to stabilize the amino groups on
BArSAs, was established by comparison of the structural prop-
erties of BPSA and sulfide precursor 4b. In the crystal struc-
tures shown in Figure 1a, typical intramolecular hydrogen
Results and Discussion
Synthesis of BArSAs
All BArSA derivatives discussed herein, including 2,6-bis(phe-
nylsulfonyl)aniline (BPSA), 2,6-bis(2-naphthylsulfonyl)aniline
(BNSA), 2,6-bis(2-aminophenylsulfonyl)aniline (BASA), and alkyl
derivative 2,6-bis(2-benzylsulfonyl)aniline (BBSA) were synthe-
sized by the nucleophilic aromatic substitution of 2,6-dichloro-
nitrobenzene (2) with the corresponding aryl (or benzyl) thio-
lates (1a–d), followed by palladium-catalyzed hydrogenation
(to 4), and subsequent oxidation with meta-chloroperoxyben-
zoic acid (m-CPBA; Scheme 2). All new compounds were char-
Figure 1. Crystal structures of BPSA (left) and 4b (right): a) ORTEP drawing
of the side and top views with thermal ellipsoids at 50% probability, and
b) partial view focused on the amino groups and orbital hybridization at ni-
trogen atoms.
bonds were observed between the amino and sulfonyl groups
of BPSA; the obtained parameters indicate that these hydro-
gen bonds were especially strong: N1···O3=2.826(2) ꢁ, N1À
H1=0.85(2) ꢁ, H1···O3=2.15(2) ꢁ, and N1ÀH1···O3=136(2)8;
N1···O1=2.806(2) ꢁ, N1ÀH1A=0.86(2) ꢁ, H1A···O1=2.14(2) ꢁ,
and N1ÀH1A···O1=134(2)8. Moreover, the geometry around
the amino group of BPSA was clearly in the sp2 configuration,
1
acterized by H and 13C NMR spectroscopy and HRMS (see the
Supporting Information). Moreover, elemental analyses and
single-crystal X-ray structure determinations were performed
for 4b and all BArSAs.
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Table 1. Crystallographically determined bond lengths, 1H NMR chemical shifts, and IR absorption frequencies of BPSA and 4b.
[b]
NÀC [ꢁ]
SÀC [ꢁ]
CÀC [ꢁ]
dNH [ppm][a]
nNH [cmÀ1
]
BPSA
1.346(2)
1.761(2) [S1ÀC7]
1.761(2) [S2ÀC11]
1.775(2) [S1ÀC7]
1.773(2) [S2ÀC9]
1.421(2) [C12ÀC7]
1.423(2) [C12ÀC11]
1.412(2) [C8ÀC7]
1.419(2) [C8ÀC9]
6.77
3469, 3367
3469, 3363
4b
1.380(2)
4.98
[a] Measured in CDCl3 at 358C. [b] Measured in KBr matrix.
whereas that of 4b was sp3 geometry, as shown in Figure 1b
(mean plane (C12, H1, H1A)···N1=0.018(13) ꢁ in BPSA, and
mean plane (C8, H1, H1A)···N1=0.221(9) ꢁ in 4b). The CÀN dis-
tance in BPSA was shorter than that in 4b, whereas the SÀC
bonds were shorter and aromatic CÀC bonds were elongated
(Table 1). Finally, the appearance of an amine chemical shift
1
(dNH) in the H NMR spectrum of BPSA at d=6.77 ppm showed
characteristics of an amide functionality (Figure S20 in the Sup-
porting Information), whereas in 4b the analogous signal ob-
served at d=4.98 ppm corresponded to an ordinary aromatic
amine (Figure S12 in the Supporting Information). Analysis of
IR absorption spectra provided further evidence for hydrogen-
bond formation; the absorption band corresponding to the
amino group of BPSA was observed at a lower frequency than
that of 4b. Thus, all parameters noted in Table 1 are suggestive
of intramolecular hydrogen bonds, as shown in Scheme 1.
Absorbance and fluorescence properties of BBSA, BPSA, and
BNSA
BBSA, BPSA, and BNSA exhibited efficient emissions from l=
393–406 nm with high quantum yields in acetonitrile (Table 2
and Figure 2a).[13] With respect to the optical properties of
BPSA, it should be noted that the wavelength of maximum ab-
sorbance (lmaxabs) showed a redshift of 20 nm relative to sulfide
precursor 4b, and the molar extinction coefficient (emax) was
17% higher than that of 4b; this is indicative of the construc-
tion of an effective push–pull system between amino and sul-
fonyl groups. As another special feature of the BArSAs, both
absorption and fluorescence spectra exhibited a redshift rela-
tive to the extent of p conjugation, for example, BBSA<
Figure 2. a) Absorption and fluorescence spectra of BBSA (black), BPSA (red),
and BNSA (blue) in acetonitrile; b) solid-state absorption and fluorescence
spectra. Absorption spectra were measured by using the reflection method
in an integrating sphere with lamp-switching wavelengths of 330 (BPSA,
BNSA) or 350 nm (BBSA).
BPSA<BNSA (Figure 2a). Values of lmax
and lmax were
abs
em
themselves. Therefore, these redshifts can be ascribed to the
bis-arylsulfonyl unit; thus, the BArSAs appeared to possess
higher for BArSA derivatives than those of the respective
benzyl, phenyl, and 2-naphthyl sulfide precursors (4a,b,c)
a
flexible
p-conjugation
system.[14] As previously men-
tioned, luminophores construct-
ed based on the rigid flat design
are commonly nonemissive in
the solid state. In contrast, BBSA,
BPSA, and BNSA showed solid-
state emissions in the powder
form, with quantum yields of
F=0.31, 0.36, and 0.28, respec-
tively (Table 2 and Figure 2b).
Table 2. Absorption and luminescence properties of 4b, BBSA, BPSA, and BNSA.[a]
Solution [acetonitrile]
Solid state [powder]
lmax [nm]
emax [mÀ1 cmÀ1
]
lmax [nm][b]
F[c]
lmax [nm][d]
lmax [nm][e]
F[f]
abs
em
abs
em
4b
322
329
340
343
6800
6600
7900
7400
383
393
401
406
0.049
0.50
0.37
0.31
316
348
359
379
387
393
409
458
0.030
0.31
0.36
0.28
BBSA
BPSA
BNSA
[a] UV/Vis spectra recorded at 5.0ꢂ10À5 m for 4b and BArSAs; fluorescence spectra recorded at 2.5ꢂ10À5 m for
4b and 5.0ꢂ10À6 m for BBSA, BPSA, and BNSA. [b] Excitation at l=300 (4b, BBSA) and 320 nm (BPSA, BNSA).
[c] Determined relative to anthracene in benzene (F=0.29). [d] Reflection spectra in an integrating sphere.
[e] Excitation at l=300 (4b, BBSA) and 320 nm (BPSA, BNSA). [f] Determined in an integrating sphere.
The lmax of BBSA, BPSA, and
abs
BNSA in solid-state exhibited
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Figure 3. Crystal structures of a) BBSA, b) BPSA, and c) BNSA. Dimerized aromatics are illustrated as space-filling models and as partially cutaway views with
distances of interatomic CÀC contacts.
redshifts of 19, 19, and 36 nm, respectively, compared with
those in solution. In addition, the lmax values of BPSA and
em
BNSA were observed at longer wavelengths than those ob-
served in solution (8 and 52 nm, respectively). These results in-
dicate the presence of an intermolecular interaction between
the aromatic moieties of BBSA, BPSA, and BNSA. Specifically,
the central sulfonylaniline units of BBSA and BPSA participated
in dimeric structure formation (Figure 3a and b), and the naph-
thyl moieties of BNSA took part in p stacking in its dimer form
(Figure 3c). The dimerized aromatic rings adopted an antiparal-
lel formation with distances within the acceptable range of p–
p stacking interactions; the closest distances between carbon
atoms were 3.67(7), 3.40(0), and 3.54(4) ꢁ in BBSA, BPSA, and
BNSA, respectively. The long wavelength of solid-state absorp-
tion spectra in these BArSAs were thus attributed to a J-dimer
form;[7b,15] the bent shape of BArSAs is advantageous to solid-
state emission, which is quite different from ordinary rigid, flat
luminophores. To confirm the flexibility of the p-conjugation
system present in BArSAs, DFT calculations were performed on
BPSA and 4b at the B3LYP/6-31G(d) level. Optimizations were
performed by using the respective crystal structures as the ini-
tial geometries; the resulting conformations for both com-
pounds were in a good agreement with those of the crystal
structures. As shown in Figure 4, the HOMO of BPSA is located
at the central aniline unit and the LUMO extends through the
sulfonyl groups to the edge phenyl rings. On the other hand,
in 4b, the HOMO and LUMO are mainly located at the central
aniline unit. These results indicate that the BArSA framework
demonstrates charge transfer from aniline to the phenyl rings
through the sulfonyl bridges. Both the HOMO and LUMO
energy levels of BPSA were lower than those of 4b; this is as-
sumed to arise because of the strong electron-withdrawing
effect of the sulfonyl groups. More importantly, the HOMO–
Figure 4. HOMO and LUMO orbital representations for BPSA (left) and 4b
(right).
LUMO energy gap of BPSA showed a clear decrease from that
of 4b; this clearly indicates the construction of an effective
push–pull and p-conjugation system.
Fluorescence properties of BASA
The solid-state fluorescence properties of BArSAs prompted us
to explore an additional molecular framework, namely, the in-
troduction of amino groups in the form of a BArSA skeleton to
diminish fluorescence by using the rotatable amino moieties.
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Table 3. Absorption and emission properties of BASA in selected solvent-
s.[a]
Solvent
lmax [nm]
lmax [nm][b]
e [mÀ1 cmÀ1
]
F[c]
abs
em
THF
345
343
341
343
342
341
341
348
350
339[d]
432
450
454
457
456
473
468
478
491
396
12400
13300
12200
12100
11300
12500
12300
12800
13300
–
0.0080
0.0056
0.0053
0.0050
0.0029
0.0019
0.0018
0.0027
0.0020
0.15[e]
1-BuOH
2-PrOH
1-PrOH
EtOH
CH3CN
CH3OH
DMF
DMSO
powder
[a] UV/Vis spectra recorded at 5.0ꢂ10À5 m; fluorescence spectra recorded
at 2.5ꢂ10À5 m. [b] Excitation at l=340 nm. [c] Determined relative to an-
thracene in benzene. [d] Reflection spectra in an integrating sphere.
[e] Determined in an integrating sphere.
Figure 5. Fluorescence spectra of BASA: a) fluorescence spectra of BASA in
1-BuOH (black), 2-PrOH (green), 1-PrOH (light blue), EtOH (pink), and CH3OH
(orange); b) plot of fluorescence intensity at l=450 nm versus solution per-
mittivity; c) fluorescence spectra of BASA in CH3CN–PEG1000 (PEG=poly-
ethylene glycol) mixtures measured with different weight fractions of
PEG1000: 0 (red), 10 (orange), 20 (yellow green), 30 (light green) 40 (light
blue), 50 (cyan), 60 (blue), 70 (purple), 80 wt% (black); and d) plot of fluores-
cence intensity at l=464 nm versus solution viscosity.
Figure 6. Crystal structures of BASA: a) ORTEP drawing of the side and top
views with thermal ellipsoids at 50% probability, b) partial view focused on
the amino groups and orbital hybridization at nitrogen atoms, and c) pack-
ing structure with dimerized aromatics illustrated as space-filling models
and with partially cutaway views of an interatomic CÀC contact.
This strategy is based on a weak fluorescence originating from
the twisted intramolecular charge-transfer (TICT) states, which
is not an unusual phenomenon for rotatable amino groups.[16]
Thus, we thought that, if the nonemissive state could be
switched to an emissive state, turn-on-type probes would be
observed. BASA demonstrated low quantum yields in a variety
of common solvents (Table 3); the value of F was two orders
of magnitude lower than that of BPSA in acetonitrile (F=
0.0019 and 0.37 for BASA and BPSA, respectively). In addition,
BASA showed solvatochromic fluorescence and the value of
redshifts were observed to increase with increasing solvent po-
larity (e.g., lmaxem =432 and 491 nm in THF and in DMSO, re-
spectively; Table 3 and Figure S44e in the Supporting Informa-
tion); a significant correlation between solvent permittivity and
fluorescence intensity was found among the various alcohols
examined (R2 =0.95; Figure 5a and b). The emission intensity
of BASA also increased in viscous solvents prepared from ace-
tonitrile–PEG mixtures (Figure 5c),[17] with significant correla-
tion between solvent viscosity and fluorescent intensity (R2 =
0.98; Figure 5d). It should be noted that the resulting higher
emission intensities in nonpolar and viscous solvents are par-
ticularly seen in molecular rotors based on TICT princi-
ples.[17c,d,18] A significant feature present in BASA was that, in
contrast to the weak fluorescence intensities in solution, a sig-
nificant increase was discovered in the solid state (F=0.15). It
appears that the mechanism is due to immobilization of the
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Figure 7. a) Fluorescence spectra of BASA in mixtures of DMSO–H2O: water fraction of 0 (red), 10 (orange), 20 (yellow green), 30 (light green), 40 (light blue),
50 (cyan), 60 (blue), 70 (purple), 80 (gray), and 90% (black); b) plot of fluorescence intensity versus water volume fractions at l=491 nm as 0% peak maxi-
mum; and c) photographs of BASA in room temperature CH3CN (left) and frozen (right) illuminated with a UV lamp (l=365 nm).
rotatable CÀN bonds of amino groups. The X-ray structure of
BASA revealed the existence of intramolecular distances char-
acteristic of weaker hydrogen bonds between the side amino
groups and sulfonyl groups (Figure 6a), whereas parameters
for hydrogen bonds were particularly strengthened for the
central aniline unit. Both adjacent amino groups were ob-
served to adopt sp3-like hybridization (mean plane (C1, H1,
H1A)···N1=0.173(10) ꢁ), whereas the central amino group was
completely in an sp2 configuration (mean plane (C7, H2,
H2A)···N2=0.000(0) ꢁ; Figure 6b). Additionally, the C1ÀN1 dis-
tance of 1.375(2) ꢁ was longer than the C7ÀC2 distance of
0.351(2) ꢁ. These structural properties together indicated that
the hydrogen bonds on the adjacent amino moieties were in-
adequate for conjugation of an amide bond and resulted in ro-
tation in solution. Two sulfonyl groups on both sides are
hence definitely required to immobilize the amino groups.
The crystal packing of BASA revealed a dimeric structure
formed through interaction between the end aniline units (Fig-
ure 6c); however, the dimeric aniline units were in a parallel
form similar to an H dimer; the closest distance between
carbon atoms was 3.34(3) ꢁ, which corresponded to a higher
energy state than the monomeric form in the nonemissive
state.[7b,19] These results reflect that the solid-state absorption
and emission of BASA showed a blueshift with respect to that
found in solution. In further progress toward applying the
turn-on principle to BASA, we achieved fluorescence recoveries
under aggregation (AIE) in a mixture of DMSO–H2O (Figure 7a
and b) and in frozen acetonitrile (Figure 7c).[6a,18a,c,d] Both
frozen and aggregation emission wavelengths were similar to
those of solid-state emissions.
Photostability of BArSAs
We demonstrated the photostability of BArSAs in solution
(Figure 8 and Figure S47 in the Supporting Information). The
sulfonyl-bridged BPSA was slightly more stable than sulfur-
bridged 4b; this indicated that immobilization of the rotatable
amino moiety exerted an effect on the hydrogen bonds. All
BArSAs showed higher stability than that of ordinary fluores-
cent dyes,[11,20,21] such as 1,8-ANS and 7-diethylamino-4-methyl-
coumarin. Notably, the environmental turn-on probe BASA
showed the highest stability of all dyes studied herein. In par-
ticular, BASA showed higher stability than that of 1,8-ANS; a flu-
orescent molecule commonly used as a polarity-sensitive
probe.[22] The high stability of BASA allowed for the convenient
long-term storage of a stock solution in DMSO (more than four
weeks; see below).
Cell imaging
Amide-based molecules, such as Netropsin, Distamycin, and
pyrrole–imidazole (Py–Im) polyamides, have an affinity for
DNA.[23] BASA has similar resonance forms between the arylsul-
fonyl moiety and the peptide bond. To demonstrate the utility
of the fluorescent properties of BASA with respect to bioimag-
ing applications, we examined the use of BASA for the cell
imaging of bovine oocyte cells arrested at the metaphase II
(MII) stage, with two DNA fragments present in the cells. Con-
focal images of the MII oocyte cell stained with BASA clearly
revealed two fragments (Figure 9a and b). In particular, dot
images that characterized the chromosomes at the MII stage
were observed (Figure 9a, inset). Similar images were observed
when Hoechst 33342, which is a common nuclear stain, was
used (Figure 9c and d). These results indicate that BASA un-
Figure 8. Plot of decreased absorbance percentage versus irradiation time
for 4b (blue, open circle), BPSA (red, filled circle), BASA (black, square), 1,8-
ANS (green, rhombus), and a coumarin derivative (gray, triangle) obtained
by using a 150 W xenon lamp in CH3CN. 1,8-ANS: 8-anilino-1-naphthalene-
sulfonic acid ammonium salt; coumarin derivative: 7-diethylamino-4-methyl-
coumarin.
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lieve that various other BArSAs can be prepared from easily
available starting materials. This strategy, which is a significant
departure from conventional flat and rigid molecular design,
may provide a means to construct a wide variety of solid-state
fluorescent materials and bioimaging probes.
Experimental Section
General methods
All chemicals and solvents employed were of reagent grade unless
otherwise indicated. Ethanol was purified by a standard distillation
procedure by employing magnesium turnings and iodine prior to
use. THF was purified by a standard distillation procedure with
LiAlH4 prior to use. All reactions were performed in standard, dry
glassware under an inert atmosphere of nitrogen (N2). Column
chromatography was performed by using Kanto silica gel 60 N
(spherical neutral, 40–100 mm) and Fuji Silysia Chemical NH silica
gel (100–200 mesh). TLC was performed by using precoated alumi-
num sheets covered with 0.20 mm silica gel with fluorescent indi-
cator (l=254 nm) and Fuji Silysia Chemical NH TLC plates. Melting
points were determined with a Yanaco MP-500P apparatus. NMR
spectra were obtained on a JEOL JNM-ECX spectrometer operating
1
at 500 MHz for H or 125 MHz for 13C in deuterated chloroform or
deuterated DMSO with tetramethylsilane (TMS) as an internal refer-
ence (358C); chemical shifts (d) are reported in ppm. Elemental
analysis was obtained by using a PerkinElmer CHNS/O 2400II ana-
lyzer. IR spectroscopy was conducted by using a Horiba FTIR FREE-
XACT II FT-720 instrument on KBr (press) or NaCl (cast film). Field-
desorption mass spectra (FD-HRMS) were obtained on a JEOL JMS-
T100GCV instrument.
Figure 9. Imaging of bovine oocyte cells (MII stage) by BASA (200 mm;
upper) and Hoechst 33342 (10 mm; lower). Excitation wavelength: 405 nm,
emission filter: 420–520 nm. Best images obtained by confocal fluorescence
microscopy (a and c), and superposed confocal and phase contrast micros-
copy (b and d). e) Plot of signal-to-noise ratio of BASA and Hoechst 33342
(mean and standard error for n=25 independent experiments). Insets in a)
and c): Dot image characterization of the chromosomes at the MII stage.
Optical spectroscopy
UV/Vis spectra were measured on a Hitachi U-2810 spectrometer.
Reflection spectra were measured on a Jasco V670 instrument
(with an integrating sphere system). Fluorescence spectra of solu-
tions were measured on a Hitachi F-7000 instrument. Solid-state
fluorescence spectra were obtained with a Horiba Fluoromax 4 in-
strument. Solid-state fluorescence quantum yields were measured
with a Hamamatsu C9920-01 integral sphere system.
doubtedly behaves as a DNA-selective probe. In general, cell-
imaging contrast agents under short-wave UV excitation are
likely to be comparatively small owing to intrinsic fluorescence
and cell damage. Nevertheless, the 25 cell samples stained
with BASA were well contrasted and, in some cases, were su-
perior to Hoechst’s high-contrast images (Figure 9e).
Synthesis
Conclusion
2,6-Bis(benzylsulfanyl)nitrobenzene (3a): Benzyl mercaptan
(5.00 g, 40.3 mmol) was added to a solution of sodium (1.11 g,
48.3 mmol) in ethanol (70 mL) at room temperature. After 30 min
We have demonstrated the use of BArSAs as a novel fluores-
cent architecture. The most important feature of this system is
that the free amino group, when not immobilized, is effectively
utilized as a strong electron donor; a push–pull effect is ob-
served in concert with sulfonyl groups functioning as electron-
withdrawing groups within the fluorescent architecture. BPSA
and BNSA showed efficient fluorescence and good photostabil-
ity in both solution and solid state. Particularly, BASA, with
amino groups on the pendant phenyl rings, imparted a high
degree of fluorescence sensitivity toward polarity and viscosity;
furthermore, amino group addition afforded a turn-on phe-
nomenon in the solid state, frozen solution, and aggregation.
Finally, BASA exhibited extremely high fluorescence stability
and behaved as a DNA-selective probe with high contrast
based on AIE. Considering the simplicity of preparation, we be-
of stirring at ambient temperature, compound
2 (3.71 g,
19.3 mmol) was added. The resultant mixture was brought to
reflux for 5 h under N2, cooled to ambient temperature, and the re-
sultant precipitate was filtered. The residue was washed with etha-
nol (50 mL) and suspended in CH2Cl2 (150 mL). After filtration, the
solvent was removed by evaporation to yield an orange crystalline
material. The residue was purified by column chromatography on
silica gel (neutral; CH2Cl2/n-hexane=2:3) to give 3a as orange crys-
tals (1.86 g, 26%). M.p. 81.7–82.08C; IR (KBr): n˜ =3025 cmÀ1 (CH);
1H NMR (500 MHz, CDCl3): d=7.28–7.10 (m, Ar-H), 4.07 ppm (s,
-CH2-); 1H NMR (500 MHz, [D6]DMSO): d=7.51–7.44 (m, 3H;
phenyl), 7.29–7.23 ppm (m, 10H; phenyl), 4.28 (s, 4H; -CH2-);
13C NMR (125 MHz, CDCl3): d=154.5, 136.1, 132.1, 129.9, 129.5,
129.1, 128.6, 127.6, 40.2; HRMS (FD+): m/z calcd for C20H17NO2S2
[M+]: 367.07007; found: 367.07102.
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2,6-Bis(phenylsulfanyl)nitrobenzene (3b): Thiophenol (5.00 g,
45.3 mmol) was added to a solution of sodium (1.35 g, 58.9 mmol)
in ethanol (60 mL) at room temperature. After 30 min of stirring at
ambient temperature, compound 2 (4.26 g, 22.9 mmol) was added.
The resultant mixture was brought to reflux for 21 h under N2,
cooled to ambient temperature, and the resultant precipitate was
filtered. The residue was washed with ethanol (50 mL) and sus-
pended in CH2Cl2 (200 mL). After filtration, the solvent was re-
moved by evaporation to give 3b as a yellow powder (5.92 g,
77%). M.p. 116.9–117.98C; IR (KBr): n˜ =3058 cmÀ1 (CH); 1H NMR
(500 MHz, CDCl3): d=7.50–7.48 (m, 4H; phenyl), 7.39–7.38 (m, 6H;
phenyl), 7.07 (t, J=8.0 Hz, 1H; phenyl), 6.88 ppm (d, J=8.0 Hz, 2H;
phenyl); 13C NMR (125 MHz, CDCl3): d=147.9, 135.0, 134.3, 132.2,
130.8, 129.8, 129.2, 128.3 ppm; HRMS (FD+): m/z calcd for
C18H13NO2S2 [M+]: 339.03877; found: 339.03873.
117.3, 39.5 ppm; HRMS (FD+): m/z calcd for C20H19NS2 [M+]:
337.09589; found: 337.09485.
2,6-Bis(phenylsulfanyl)aniline (4b): 10 wt% Pd/C (500 mg) was
added to a solution of 3b (1.00 g, 2.95 mmol) in THF (30 mL) and
ethanol (30 mL) under N2. The reaction mixture was continuously
shaken under a hydrogen atmosphere (balloon pressure) for 24 h.
The black suspension was filtered and washed with CH2Cl2
(150 mL); the solvent was then removed under reduced pressure
to give 4b as a colorless solid (0.89 g, 89%). M.p. 73.4–73.78C; IR
1
(KBr): n˜ =3469 (NH), 3363 (NH), 3056 cmÀ1 (CH); H NMR (500 MHz,
CDCl3): d=7.54 (d, J=7.5 Hz, 2H; phenyl), 7.25–7.21 (m, 4H;
phenyl), 7.14–7.08 (m, 6H; phenyl), 6.73 (t, J=7.5 Hz, 1H; phenyl),
4.98 ppm (brs, 2H; -NH2); 13C NMR (125 MHz, CDCl3): d=152.2,
139.0, 136.0, 128.9, 126.4, 125.5, 117.8, 114.8 ppm; HRMS (FD+): m/
z calcd for C18H15NS2 [M+]: 309.06459; found: 309.06436; elemental
analysis calcd (%) for C18H15NS2: C 69.87, H 4.89, N 4.53, S 20.72;
found: C 69.73, H 4.89, N 4.40, S 20.74.
2,6-Bis(2-naphthylsulfanyl)nitrobenzene (3c): 2-Naphthalenethiol
(8.00 g, 49.9 mmol) was added to a solution of sodium (1.23 g,
54.9 mmol) in ethanol (100 mL) at room temperature. After 30 min
2,6-Bis(2-naphthylsulfanyl)aniline (4c): 10 wt% Pd/C (800 mg)
was added to a solution of 3c (1.30 g, 2.96 mmol) in THF (40 mL)
and ethanol (35 mL) under N2. The reaction mixture was continu-
ously shaken under a hydrogen atmosphere (balloon pressure) for
24 h. The black suspension was filtered and washed with CH2Cl2
(150 mL); the solvent was then removed under reduced pressure.
The crude product (1.41 g) was purified by column chromatogra-
phy on silica gel (NH silica gel; CH2Cl2) to give 4c as colorless crys-
tals (1.10 g, 91%). M.p. 158.7–159.28C; IR (KBr): n˜ =3436 (NH), 3340
(NH), 3050 cmÀ1 (CH); 1H NMR (500 MHz, CDCl3): d=7.74 (dd, J=
8.0, 2.0 Hz, 2H; naphthyl), 7.70 (d, J=8.0 Hz, 2H; phenyl), 7.62 (m,
4H; naphthyl), 7.49 (d, J=2.0 Hz, 2H; naphthyl), 7.43–7.37 (m, 4H;
naphthyl), 7.26–7.24 (m, 2H; Ar-H), 6.80 (t, J=8.0 Hz, 1H; phenyl),
5.04 ppm (brs, 2H; -NH2); 13C NMR (125 MHz, CDCl3): d=150.7,
139.1, 133.6, 133.4, 131.6, 128.6, 127.6, 126.9, 126.5, 125.5, 125.1,
124.6, 118.0, 115.1; HRMS (FD+): m/z calcd for C26H19NS2 [M+];
409.09589; found: 409.09431.
of stirring at ambient temperature, compound
2 (4.58 g,
23.8 mmol) was added. The resultant mixture was brought to
reflux for 4 h under N2, cooled to ambient temperature, and the re-
sultant precipitate was filtered. The residue was washed with etha-
nol (70 mL) and suspended in CH2Cl2 (200 mL). After filtration, the
solvent was removed by evaporation to give 3c as an orange
powder (6.51 g, 69%). M.p. 132.5–133.98C; IR (KBr): n˜ =3050 cmÀ1
(CH); 1H NMR (500 MHz, CDCl3): d=8.07 (d, J=2.0 Hz, 2H; naph-
thyl), 7.85–7.81 (m, 6H; naphthyl), 7.55–7.51 (m, 4H; naphthyl),
7.46 (dd, J=8.5, 2.0 Hz, 2H; naphthyl), 6.99 (t, J=8.0 Hz, 1H;
phenyl), 6.87 ppm (d, J=8.0 Hz, 2H; phenyl); 13C NMR (125 MHz,
CDCl3): d=147.9, 135.2, 134.2, 133.8, 133.2, 130.8, 130.5, 129.7,
129.5, 128.4, 127.88, 127.86, 127.3, 127.0 ppm; HRMS (FD+): m/z
calcd for C26H17NO2S2 [M+]: 439.07007; found: 439.06917.
2,6-Bis(2-aminophenylsulfanyl)nitrobenzene (3d): 2-Aminothio-
phenol (8.15 g, 65.1 mmol) was added to a solution of sodium
(1.65 g, 71.7 mmol) in ethanol (80 mL) at room temperature. After
30 min of stirring at ambient temperature, compound 2 (6.00 g,
31.25 mmol) was added. The resultant mixture was brought to
reflux for 5 h under N2, cooled to ambient temperature, and the re-
sultant precipitate was filtered. The residue was washed with etha-
nol (50 mL) and suspended in CH2Cl2 (300 mL). After filtration, the
solvent was removed by evaporation to give a dark-red powder.
The residue was washed with diethyl ether (50 mL) to give 3d as
orange crystals (4.96 g, 43%). M.p. 199.7–200.38C; IR (KBr): n˜ =
3473 (NH), 3367 (NH), 3054 cmÀ1 (CH); 1H NMR (500 MHz, CDCl3):
d=7.43 (d, J=8.0 Hz, 2H; phenyl), 7.28–7.26 (m, 2H; phenyl), 7.00
(t, J=8.0 Hz, 1H; phenyl), 6.79–6.75 (m, 4H; phenyl), 6.64 (d, J=
8.0 Hz, 2H; phenyl), 4.28 ppm (brs, 4H; -NH2); 13C NMR (125 MHz,
CDCl3): d=149.2, 145.3, 137.9, 135.8, 132.2, 131.3, 124.7, 119.1,
115.7, 112.7 ppm; HRMS (FD+): m/z calcd for C18H15N3O2S2 [M+]:
369.06057; found: 369.06161.
2,6-Bis(2-aminophenylsulfanyl)aniline
(4d):
10 wt%
Pd/C
(250 mg) was added to a solution of 3d (0.500 g, 1.35 mmol) in
ethyl acetate (50 mL) under N2. The reaction mixture was continu-
ously shaken under a hydrogen atmosphere (balloon pressure) for
24 h. The black suspension was filtered and washed with CH2Cl2
(150 mL); the solvent was then removed under reduced pressure
to give 4d as colorless crystals (0.46 g, quant). M.p. 132.8–133.28C;
IR (KBr): n˜ =3457 (NH), 3357 (NH), 3050 cmÀ1 (CH); 1H NMR
(500 MHz, CDCl3): d=7.20 (dd, J=8.5, 1.5 Hz, 2H; phenyl), 7.12–
7.09 (m, 4H; phenyl), 6.72–6.66 (m, 4H; phenyl), 6.58 (t, J=7.5 Hz,
1H; phenyl), 4.81 (brs, 2H; -NH2), 4.17 ppm (brs, 4H; -NH2);
13C NMR (125 MHz, CDCl3): d=145.9, 145.3, 132.8, 131.6, 128.6,
118.1, 117.7, 117.1, 115.6, 114.6 ppm; HRMS (FD+): m/z calcd for
C18H17N3S2 [M+]: 339.08639; found: 339.08631.
2,6-Bis(2-benzylsulfonyl)aniline (BBSA): m-CPBA (1.61 g, 65%,
6.07 mmol) was added to a cooled solution (08C) of 4a (0.50 g,
1.48 mmol) in CH2Cl2 (60 mL), and the resulting suspension was
stirred for 24 h at 08C. The reaction was quenched with a saturated
aqueous solution of Na2SO3 (5 mL), diluted with 3m NaOH (10 mL),
and the aqueous layer was extracted with CH2Cl2 (2ꢂ50 mL). The
combined organic layers were washed with water (3ꢂ100 mL) and
brine (50 mL). After drying over anhydrous Na2SO4, the solvent was
removed under reduced pressure to give BBSA as colorless crystals
(0.511 g, 86%). M.p. 153.3–153.88C; IR (KBr): n˜ =3455 (NH), 3359
(NH), 3021 (CH), 1455 (SO2), 1122 cmÀ1 (SO2); 1H NMR (500 MHz,
CDCl3): d=7.55 (d, J=8.0 Hz, 2H; phenyl), 7.33 (m, 2H; phenyl),
7.29–7.26 (m, 2H; phenyl), 7.09 (dd, J=7.5, 1.4 Hz, 2H; phenyl),
2,6-Bis(benzylsulfanyl)aniline (4a): 10 wt% Pd/C (250 mg) was
added to a solution of 3a (0.55 g, 1.50 mmol) in THF (30 mL) and
ethanol (30 mL) under N2. The reaction mixture was continuously
shaken under a hydrogen atmosphere (balloon pressure) for 24 h.
The black suspension was filtered and washed with CH2Cl2
(150 mL); the solvent was then removed under reduced pressure
to give 4a as a colorless oil (0.50 g, 98%). IR (NaCl): n˜ =3444 (NH),
1
3345 (NH), 3058 cmÀ1 (CH); H NMR (500 MHz, CDCl3): d=7.25–7.20
(m, 7H; phenyl), 7.14–7.11 (m, 5H; phenyl), 6.44 (t, J=7.5 Hz, 1H;
phenyl), 4.96 (brs, 2H; -NH2), 3.88 ppm (s, 4H; -CH2-); 13C NMR
(125 MHz, CDCl3): d=150.7, 138.2, 137.4, 128.9, 128.4, 127.1, 117.5,
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6.56 (t, J=8.0 Hz, 1H; phenyl), 6.40 (brs, 2H; -NH2), 4.32 ppm (s,
4H; -CH2-); 13C NMR (125 MHz, CDCl3): d=146.6, 137.9, 130.8, 129.2,
128.8, 127.4, 120.9, 115.7, 61.2; HRMS (FD+): m/z calcd for
C20H19NO4S2 [M+]: 401.07555; found: 401.07461; elemental analysis
calcd (%) for C20H19NO4S2: C 59.83, H 4.77, N 3.49, S 15.97; found: C
59.91, H 4.77, N 3.43, S 16.08.
7.5 Hz, 2H; phenyl), 7.66 (dd, J=8.5, 1.0 Hz, 2H; phenyl), 7.32–7.26
(m, 2H; phenyl), 6.79–6.75 (m, 3H; phenyl), 6.67–6.61 (m, 4H;
phenyl, -NH2), 4.99 ppm (brs, 4H; -NH2); 13C NMR (125 MHz, CDCl3):
d=146.0, 144.8, 135.4, 135.3, 129.5, 124.3, 121.0, 118.0, 117.9,
115.3 ppm; HRMS (FD+): m/z calcd for C18H17N3O4S2 [M+]:
403.06605; found: 403.06615; elemental analysis calcd (%) for
C18H17N3O4S2: C 53.58, H 4.25, N 10.41, S 15.89; found: C 53.58, H
4.19, N 10.39, S 15.87.
2,6-Bis(phenylsulfonyl)aniline (BPSA): m-CPBA (2.68 g, 65%,
10.87 mmol) was added to a cooled solution (08C) of 4b (0.82 g,
2.65 mmol) in CH2Cl2 (60 mL), and the resulting suspension was
stirred for 24 h at 08C. The reaction was quenched with a saturated
aqueous solution of Na2SO3 (10 mL), diluted with 3m NaOH
(10 mL), and the aqueous layer was extracted with CH2Cl2 (2ꢂ
50 mL). The combined organic layers were washed with water (2ꢂ
100 mL) and brine (50 mL). After drying over anhydrous Na2SO4,
the solvent was removed under reduced pressure to give BPSA as
colorless crystals (0.90 g, 92%). M.p. 160.2–161.28C; IR (KBr): n˜ =
3471 (NH), 3367 (NH), 3072 (CH), 1457 (SO2), 1143 cmÀ1 (SO2);
1H NMR (500 MHz, CDCl3): d=8.05 (d, J=8.0 Hz, 2H; phenyl), 7.86–
7.84 (m, 2H; phenyl), 7.61–7.58 (m, 2H; phenyl), 7.51–7.47 (m, 4H;
phenyl), 6.84 (t, J=8.0 Hz, 1H; phenyl), 6.77 ppm (brs, 2H; -NH2);
13C NMR (125 MHz, CDCl3): d=145.2, 140.8, 136.6, 133.7, 129.3,
126.9, 124.4, 116.4 ppm; HRMS (FD+): m/z calcd for C18H15NO4S2
[M+]: 373.04425; found: 373.04456; elemental analysis calcd (%)
for C18H15NO4S2: C 57.89, H 4.05, N 3.75, S 17.17; found: C 57.86, H
3.90, N 3.64, S 17.04.
X-ray crystallography
Details of the structures and their refinement are summarized in
the Supporting Information. CCDC 951159 (4b), 951160 (BBSA),
951161 (BPSA), 951162 (BNSA), and 951163 (BASA) contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif..
Preparation of powder samples
Powder samples for reflection spectra, fluorescence spectra, and
quantum yield measurements were obtained by grinding single
crystals; all powder XRD profiles obtained were the same as simu-
lations of 2D diffraction patterns from the corresponding single-
crystal data (Figure S43 in the Supporting Information).
2,6-Bis(2-naphthylsulfonyl)aniline (BNSA): m-CPBA (1.78 g, 65%,
7.21 mmol) was added to a cooled solution (08C) of 4c (0.72 g,
1.76 mmol) in CH2Cl2 (60 mL), and the resulting suspension was
stirred for 24 h at 08C. The reaction was quenched with a saturated
aqueous solution of Na2SO3 (5 mL), diluted with 3m NaOH (10 mL),
and the aqueous layer was extracted with CH2Cl2 (2ꢂ100 mL). The
combined organic layers were washed with water (3ꢂ150 mL) and
brine (100 mL). After drying over anhydrous Na2SO4, the solvent
was removed under reduced pressure to give a dark-yellow
powder (0.82 g). The crude product was purified by column chro-
matography on silica gel (NH silica gel; CH2Cl2) to give BNSA as
a pale-yellow powder (0.80 g, 96%). M.p. 177.5–178.48C; IR (KBr):
n˜ =3465 (NH), 3353 (NH), 3046 (CH), 1455 (SO2), 1126 cmÀ1 (SO2),
1H NMR (500 MHz, CDCl3): d=8.45 (d, J=1.5 Hz, 2H; naphthyl),
8.10 (d, J=8.0 Hz, 2H; phenyl), 7.91 (d, J=8.0 Hz, 2H; naphthyl),
7.86–7.84 (m, 4H; naphthyl), 7.72 (dd, J=9.0, 1.5 Hz, 2H; naphthyl),
7.66–7.56 (m, 4H; naphthyl), 6.89–6.85 ppm (m, 3H; -NH2, phenyl);
13C NMR (125 MHz, CDCl3): d=145.4, 137.7, 136.7, 135.3, 132.0,
129.8, 129.5, 129.4, 128.4, 128.0, 127.8, 124.6, 121.8, 116.5 ppm;
HRMS (FD+): m/z calcd for C26H19NO4S2 [M+]: 473.07555; found:
473.07707; elemental analysis calcd (%) for C26H19NO4S2: C 65.94, H
4.04, N 2.96, S 13.54; found: C 65.85, H 4.05, N 2.84, S 13.64.
Fluorescence spectra of BASA in a viscous environment and
AIE state
Fluorescence spectra of BASA in a viscous environment were mea-
sured in a mixture of various compositions of CH3CN–PEG1000
(1.0ꢂ10À5 m). The viscosity of each solution was measured by
using an A&D SV-10 Vibro viscometer instrument and the density
was measured to calculate the kinematic viscosity. Fluorescence
spectra for the AIE state of BASA were measured in mixtures of
various compositions of DMSO–water (2.5ꢂ10À4 m).
Photostability determination[21a]
Photostabilities of 4b, BPSA, BASA, 1,8-ANS, and 7-diethylamino-4-
methylcoumarin were investigated by using a 150 W xenon lamp
to obtain absorption spectra. UV/Vis spectra of compounds were
measured after alignment in acetonitrile (5.0ꢂ10À5 m, t=0 min),
followed by irradiation for 45 min. Absorption spectra were mea-
sured at regular time intervals (t=5, 10, 15, 30, 45 min). The mea-
surement cell was separated from the light source at 10 cm and
a clear cuvette with water was situated midway to avoid increases
in temperature.
2,6-Bis(2-aminophenylsulfonyl)aniline (BASA): m-CPBA (3.89 g,
65%, 15.7 mmol) was added to a cooled solution (08C) of 4d
(1.30 g, 3.83 mmol) in CH2Cl2 (120 mL), and the resulting suspen-
sion was stirred for 24 h at 08C. The reaction was quenched with
a saturated aqueous solution of Na2SO3 (20 mL), diluted with 3m
NaOH (30 mL), and the aqueous layer was extracted with CH2Cl2
(3ꢂ100 mL). The combined organic layers were washed with water
(3ꢂ100 mL) and brine (100 mL). After drying over anhydrous
Na2SO4, the solvent was removed under reduced pressure to give
a pale-gray powder (1.40 g). The crude product was purified by
chromatography over silica gel (NH silica gel; CH2Cl2/AcOEt=4:1)
and then recrystallized from CH2Cl2/n-hexane to give BASA as col-
orless crystals (1.20 g, 78%). M.p. 160.5–161.58C; IR (KBr): n˜ =3488
(NH), 3465 (NH), 3390 (NH), 3372 (NH), 3064 (CH), 1485 (SO2), 1462
(SO2), 1132 cmÀ1 (SO2); 1H NMR (500 MHz, CDCl3): d=7.96 (d, J=
Collection of bovine cumulus oocyte complexes (COCs)
Bovine offal ovaries were collected at a local slaughterhouse and
transported to the laboratory in a thermos flask at approximately
208C. COCs were then aspirated from visible follicles (2–8 mm in
diameter). After three washes, about 20 COCs each were cultured
for 22–23 h in droplets (200 mL) of a maturation medium consisting
of TCM199 supplemented with 10% fetal calf serum (FCS),
0.1 IUmLÀ1 follicle-stimulating hormone (FSH), 100 unitsmLÀ1 peni-
cillin G potassium (Meiji, Tokyo, Japan), and 100 mgmLÀ1 streptomy-
cin sulfate (Meiji, Tokyo, Japan) in a humidified atmosphere of 5%
CO2 in air at 38.58C under a layer of mineral oil. All chemicals were
purchased from Sigma–Aldrich (St. Louis, MO, USA), except for
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Rev. 2000, 100, 1973–2011; c) A. Loudet, K. Burgess, Chem. Rev. 2007,
107, 4891–4932.
those specifically described. The tissues and cells derived from ani-
mals used in this study were treated under the Guiding Principles
for the Care and Use of Research Animals established by Yamagata
University.
[8] M. Shimizu, T. Hiyama, Chem. Asian J. 2010, 5, 1516–1531.
[9] a) D. Ryu, E. Park, D.-S. Kim, S. Yan, J. Y. Lee, B.-Y. Chang, K. Y. Ahn, J. Am.
Chem. Soc. 2008, 130, 2394–2395; b) M. Wang, G. Zhang, D. Zhang, D.
Zhu, B. Z. Tang, J. Mater. Chem. 2010, 20, 1858–1867; c) N. B. Shustova,
B. D. McCarthy, M. Dinca˘, J. Am. Chem. Soc. 2011, 133, 20126–20129;
d) J. Wang, J. Mei, R. Hu, J. Z. Sun, A. Qin, B. Z. Tang, J. Am. Chem. Soc.
2012, 134, 9956–9966.
Observation of bovine oocyte stained by BASA
After culturing for in vitro maturation, the oocytes were denuded
of cumulus cells in a phosphate-buffered saline (PBS) containing
1 mgmLÀ1 polyvinyl alcohol and 1 mgmLÀ1 hyaluronidase by using
a fine-bore pipette. The cumulus-free oocytes were fixed in a paraf-
ormaldehyde solution (4% w/v in PBS) for more than 1 day. After
three washes, the fixed oocytes were stained with 10 mgmLÀ1
Hoechst 33342 in PBS or 200 mgmLÀ1 BASA in DMSO/PBS (3/7, v/v)
and incubated in darkness at room temperature for 30 or 120 min,
respectively. The stained oocytes were examined by confocal laser-
scanning microscopy (Olympus, FV10i; excitation wavelength,
405 nm; emission filter, 420–520 nm).
[10] For recent examples of bioimaging based on AIE, see: a) D. Ding, K. Li,
B. Liu, B. Z. Tang, Acc. Chem. Res. 2013, 46, 2441–2453; b) H. Shi, J. Liu,
J. Geng, B. Z. Tang, B. Liu, J. Am. Chem. Soc. 2012, 134, 9569–9572.
[11] a) K. Kolmakov, V. N. Belov, C. A. Wurm, B. Harke, M. Leutenegger, C.
Eggeling, S. W. Hell, Eur. J. Org. Chem. 2010, 3593–3610; b) K. Kolmakov,
C. Wurm, M. V. Sendev, M. L. Bossi, V. N. Belov, S. W. Hell, Photochem.
Photobiol. Sci. 2012, 11, 522–532.
[12] R. Gompper, H.-U. Wagner, Angew. Chem. 1988, 100, 1492–1511; Angew.
Chem. Int. Ed. Engl. 1988, 27, 1437–1455.
[13] Absorbance and fluorescent spectra of 4b and BArSAs in various sol-
vents and in the solid state (see Figures S44–46 in the Supporting Infor-
mation).
[14] For an example of a flexible p-conjugation system, see: a) T. Kajiwara, K.
Katagiri, M. Hasegawa, A. Ishii, M. Ferbinteanu, S. Takaishi, T. Ito, M. Ya-
mashita, N. Iki, Inorg. Chem. 2006, 45, 4880–4882; b) P. Chen, R. A. La-
lancette, F. Jꢄkle, J. Am. Chem. Soc. 2011, 133, 8802–8805.
[15] E. E. Jelley, Nature 1936, 138, 1009–1010.
Acknowledgements
We thank Prof. A. Masuhara (Yamagata University) for the oppor-
tunity to use and for technical support on the Jasco V-670 UV/
Vis/NIR spectrophotometer. This study was supported by the
Grant-in-Aid for Young Scientist (B) (19750104 to H.K.) from the
Ministry of Education, Culture, Sports, Science and Technology
(MEXT) and the Foundation for Japanese Chemical Research
(400(R) to H.K.).
[16] Z. R. Grabowski, K. Rotkiewicz, W. Rettig, Chem. Rev. 2003, 103, 3899–
4031.
[17] a) A. Jacobson, A. Petric, D. Hogenkamp, A. Sinur, J. R. Barrio, J. Am.
Chem. Soc. 1996, 118, 5572–5579; b) J. Zhou, X. Yuan, M. Jiang, Y.
Zhang, Macromol. Rapid Commun. 2000, 21, 579–582; c) M. A. Haidek-
ker, T. P. Brady, D. Lichlyter, E. A. Theodorakis, Bioorg. Chem. 2005, 33,
415–425; d) F. Zhou, J. Shao, Y. Yang, J. Zhao, H. Guo, X. Li, S. Ji, Z.
Zhang, Eur. J. Org. Chem. 2011, 4773–4787.
[18] a) K. A. Willets, S. Y. Nishimura, P. J. Schuck, R. J. Twieg, W. E. Moerner,
Acc. Chem. Res. 2005, 38, 549–556; b) M. A. Haidekker, E. A. Theodora-
kis, Org. Biomol. Chem. 2007, 5, 1669–1678; c) K. A. Willets, O. Ostrover-
khova, M. He, R. J. Twieg, W. E. Moerner, J. Am. Chem. Soc. 2003, 125,
1174–1175; d) S. J. Lord, Z. Lu, H. Wang, K. A. Willets, P. J. Schuck, H. D.
Lee, S. Y. Nishimura, R. J. Twieg, W. E. Moerner, J. Phys. Chem. A 2007,
111, 8934–8941.
[19] a) N. Kobayashi, A. B. P. Lever, J. Am. Chem. Soc. 1987, 109, 7433–7441;
b) K. Kameyama, M. Morisue, A. Satake, Y. Kobuke, Angew. Chem. 2005,
117, 4841–4844; Angew. Chem. Int. Ed. 2005, 44, 4763–4766.
[20] C. Eggeling, J. Widengren, R. Rigler, C. A. M. Seidel, Anal. Chem. 1998,
70, 2651–2659.
Keywords: aggregation
probes · hydrogen bonds · pi interactions
· biological activity · fluorescent
[1] B. Valeur, Molecular Fluorescence: Principles and Application, Wiley-VCH,
Weinheim, 2001.
[2] B. Valeur, Molecular Fluorescence: Principles and Application, Wiley-VCH,
Weinheim, 2012.
[3] K. Mꢃllen, U. Scherf, Organic Light Emitting Devices, Synthesis Properties
and Applications, Wiley-VCH, Weinheim, 2005.
[4] a) M. D. McGehee, A. J. Heeger, Adv. Mater. 2000, 12, 1655–1668; b) Y.
Taniguchi, J. Photopolym. Sci. Technol. 2002, 15, 183–184.
[5] I. D. W. Samuel, G. A. Turnbull, Chem. Rev. 2007, 107, 1272–1295.
[6] a) Y. Hong, J. W. Y. Lam, B. Z. Tang, Chem. Soc. Rev. 2011, 40, 5361–5388;
b) Y. Hong, J. W. Y. Lam, B. Z. Tang, Chem. Commun. 2009, 4332–4353;
c) R. Deans, J. Kim, M. R. Machacek, T. M. Swager, J. Am. Chem. Soc.
2000, 122, 8565–8566; d) B.-K. An, S.-K. Kwon, S.-D. Jung, S. Y. Park, J.
Am. Chem. Soc. 2002, 124, 14410–14415; e) Q. Zeng, Z. Li, Y. Dong, C.
Di, A. Qin, Y. Hong, L. Ji, Z. Zhu, C. K. W. Jim, G. Yu, Q. Li, Z. Li, Y. Liu, J.
Qin, B. Z. Tang, Chem. Commun. 2007, 70–72.
[21] a) G. L. Silva, V. Ediz, D. Yaron, B. A. Armitage, J. Am. Chem. Soc. 2007,
129, 5710–5718; b) E. Arunkumar, N. Fu, B. D. Smith, Chem. Eur. J. 2006,
12, 4684–4690.
[22] L. Stryer, J. Mol. Biol. 1965, 13, 482–495.
[23] a) S. Neidle, Nat. Prod. Rep. 2001, 18, 291–309; b) A. Y. Chen, C. Yu, B.
Gatto, L. F. Liu, Proc. Natl. Acad. Sci. USA 1993, 90, 8131–8135; c) T.
Bando, H. Sugiyama, Acc. Chem. Res. 2006, 39, 935–944.
Received: December 18, 2013
Published online on January 31, 2014
[7] a) O. Valdes-Aguilera, D. C. Neckers, Acc. Chem. Res. 1989, 22, 171–177;
b) A. Mishra, R. K. Behera, P. K. Behera, B. K. Mishra, G. B. Behera, Chem.
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