Branched triphenylamine-core compounds: Aggregation induced two-photon absorption

Article abstract of DOI:10.1039/c6ra09701d

Three branched molecules (T1-T3) were synthesized through simple step to realize or enhance two-photon absorption (2PA) in aggregates. Spectra data show that one- and two-branched molecules (T1 and T2) possessed remarkable AIE properties, which came from

Full text of DOI:10.1039/c6ra09701d

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Branched Triphenylamine-cored Compounds: Aggregation
Induced Two-photon Absorption
Received 00th January 20xx,
Accepted 00th January 20xx
a, ξ
a, b, ξ
a
a
a
a
Xin Zhang , Xiaoping Gan
, Shun Yao , Weiju Zhu , Jianhua Yu , Zhichao Wu , Hongping
a,
a
a
Zhou *, Yupeng Tian , Jieying Wu
DOI: 10.1039/x0xx00000x
Three branched molecules (T1-T3) were synthesized through simple step to realize or enhance 2PA in aggregates. Spectra
data showed that one- and two- branched molecule (T1 and T2) owned the remarkable AIE properties, which came from
the formation of J-aggregation because of their partial planarization in aggregation state. SEM and DLS illustrated that the
ordered aggregation and the small particle size had important influence on fluorescence emission. The open aperture Z-
scan experiments showed that T1 and T2 possessed excellent 2PA properties under aggregation state. The largest 2PA
cross section was 8314 GM for T2 in aggregates, which was higher about 13-fold than that in pure solution. All the results
displayed that the compounds could obtain the outstanding 2PA performance by adjusting their structure rationally or
changing state, which could provide reference for preparing the strong 2PA compounds.
www.rsc.org/
moderate 2PA cross sections (σ) in aggregates in the mixture
Introduction
solution of THF/H O, which made them the potential materials
for bioꢀphotonic applications. Wu and coꢀworkers reported a
series of amino substitutive styrene derivatives that showed
2
Organic compounds with excellent two photon absorption
(2PA) properties are very important for their real applications
such as optoelectronic materials and bioꢀsensors for metal ions,
good AIE performance in DMSO/H O mixture solution and
2
1
-3
anions, and neutral small molecules in cells and tissues
,
15
appropriate twoꢀphoton excited fluorescence (TPEF) .
which contributes to more focus on twoꢀphoton biological
fluorescent probe and commercially application of confocal
Consequently, these compounds were applied in twoꢀphoton
bioꢀimaging. However, the numbers of the reported 2PA
compounds with AIE or AIEE properties are very less, and the
structureꢀactivity relationship is not clear. Moreover, their 2PA
properties are slightly weak perhaps due to the contradiction
between the planarity of 2PA molecules and the twisted
conformation of AIE or AIEE molecules. So designing and
synthesis of strong 2PA molecule owning AIE or AIEE
properties is the key of twoꢀphoton bioꢀimaging and further
research is still in need.
4
-6
laser twoꢀphoton microscopes . In most case, typical πꢀπ
stacking interactions often lead to aggregationꢀcaused
7
, 8
quenching which seriously limits their applications . Hence,
aggregationꢀinduced emission (AIE) or aggregationꢀinduced
enhanced emission (AIEE) is proposed by Tang and coꢀworkers
9, 10
to overcome the disadvantage of ACQ
attracted the interest of researchers
, which has been
. Thus, a few of 2PA
1
1-13
materials with AIE or AIEE effects are synthesized, which
shows good twoꢀphoton bioꢀimaging ability in cell. For
example, Tian’ group reported a series of heterocycle replaced
It is well known that branched molecules usually possess the
synergetic enhancement effect on 2PA properties, while they
1, 4ꢀbisstyrylbenzene, which functionalized by cyano group in
16, 17
are not demand for the strict planar structure
. Based on the
double bond of styrene to produce steric hindrance and then
above, we selected triphenylamine as the molecule core to
construct branched molecules due to its excellent electron
1
4
activated AIE performance . These compounds possessed
1
8
donating ability (D) and variable propeller structure .
Meanwhile, we utilized ꢀnitrobenzene as an electron acceptor
A) to form an AꢀπꢀD model structure at each branch. The
p
a
College of Chemistry and Chemical Engineering, Anhui University and Key
Laboratory of Functional Inorganic Materials Chemistry of Anhui Province, Hefei
(
donor and acceptor were connected by carbonꢀcarbon double
bond as πꢀbridge, then we introduced cyano group to the double
bond as a multiꢀfunctional group due to its bulky volume and
abundant πꢀelectron density . Moreover, cyano group was also
an outstanding electron withdrawing group, which could adjust
the molecule dipole moment and enhance the intramolecular
2
30601, P. R. China.
b
*
School of Science, Anhui Agricultural University, 230036 Hefei, P. R. China.
Corresponding author. Fax: +86-551-63828106, Tel: +86-551-63828150. E-mail
address: zhpzhp@263.net
1
9
ξ
These authors contributed equally to this work and should be considered co-first
authors
†
Electronic Supplementary Information (ESI) available: Figures S2-S8, Tables S1-S3.
Crystallographic data have been deposited with the Cambridge Crystallographic
2
0
Data Centre as supplementary publication no. CCDC: 1428578 (for T1), 1437376 charge transfer (ICT)
.
(
for T2).
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Herein, linear AꢀπꢀD (T1), Vꢀshaped ((Aꢀπꢀ)
shaped ((Aꢀπꢀ) D) (T3) molecules (Scheme 1) have been emission peak located from 548 nm to 593 nm in different
synthesized, which used only twoꢀstep reaction to give the final polarity solvents, which was assigned to the ICT emission. As
products with high yields (over 90%). All compounds are shown in Table S and Fig b, with increasing the solvent
soluble in common organic solvents such as tetrahydrofuran polarity, the fluorescence maxima red shifted from 548 nm to
THF), acetone, ethyl acetate and dimethyl formamide (DMF) 593 nm with a relevant solvatochromic effect. From the Fig.S2-
but insoluble in water. We systematically researched their oneꢀ , it could be seen that the other two compounds had similar
2
D) (T2) and Yꢀ
The fluorescence spectrum of T1 (Fig. 1b) exhibited one
3
2
3
1
1
(
3
and twoꢀphoton optical properties in pure organic solution and feature in fluorescence spectra. Large stokes shifts were
waterꢀorganic mixture solution, which showed that T1 and T2 observed for the three compounds in five solvents due to strong
both possessed superior AIE performance in ethanol/water and solventꢀsolute dipoleꢀdipole interactions, which was
a
DMF/water solutions, respectively. Moreover, T1 and T2 were manifestation of the large dipole moment and orientational
all provided with excellent 2PA properties under aggregation polarizability. An increased dipoleꢀdipole interaction between
state, we successfully carried out the twoꢀphoton bioꢀimaging the solute and solvent generated a lower energy level. Stokes
applications based on the favorable biocompatibility.
shift were approximately proportional to the orientational
2
4, 25
polarizability.
fluorescence spectrum, LippertꢀMataga plots for T1
given in Fig. S and the calculation data were collected in
To discuss the effect of solvents on the
2
6
Results and discussion
ꢀT3 were
4
Synthesis
Table S
2
. The LippertꢀMataga equation was as follow:
The compounds
reported method.
Nitrophenylacetonitrile with the respective intermediates
and by the Knoevenagel reaction gave the target compounds
T1
and mass spectra (shown in ESI, Fig. S1
1
,
2
and
3
were prepared according with the
2
1
2ꢁf
2
Then the condensation of 4ꢀ
ꢁ
ν
=
(
ꢀe
−
ꢀg ) + b Eq. (1)
3
1
,
2
4
ε
2ε
πε hca
0
2
3
ꢀ
−1 n −1
ꢁf =
−
Eq.(2)
1
13
2
(
T3). All compounds were characterized by H, C NMR
+1 2n +1
)
in which ꢀν
=
ν
abs
–
ν
em stands for Stokes shift, νabs and νem are
ꢀ1
One-photon absorption and emission properties
absorption and emission (cm ),
the velocity of light in vacuum,
a constant. ꢀf is the orientation polarizability,
dipole moments of the emissive and ground states, respectively,
h
is the Planck constant,
is the Onsager radius and
and
c
b
is
is
a
The One photon absorption and fluorescence emission spectra
of T1 in five solvents of varying polarities were depicted in Fig.
ꢁ
e
ꢁ
g
are the
1. All the corresponding spectroscopic data were collected in
2
and
to the slope of the LippertꢀMataga plot.
As shown in Fig. S , the slopes of the fitting line for T1
0 e g
ε is the permittivity of the vacuum. (ꢁ ꢀꢁ ) is proportional
Table S . It could be seen from Fig. 1a that T1 had two
1
absorption peaks located at ~300 nm and ~430 nm, the former
was assigned to the πꢀπ* electronic transition caused by the
4
ꢀ
T3
10 , respectively.
The large slopes showed large dipole moment changes for these
4
4
4
2
2
were as high as 1.7×10 , 3.1 ×10 , and 1.9×
triphenylamine core whereas the latter was likely ascribed to
intramolecular charge transfer between the triphenylamine core
and the terminal group. From the Fig. S2-3, it could be seen
that the other two compounds had similar feature in absorption
spectra.
2
7
compounds with photoexcitation, which was consistent with
the significant solvatochromism effect measured by
experiment. However, the slope of T3 was smaller than that of
T2, the reason perhaps was that T3 owned larger Onsager
radius due to it has bulky molecule volume.
Aggregation-induced emissions
Considering the three compounds are insoluble in water but
soluble in organic solvents, we determine the absorption and
emission spectra of the T1
mixtures with different water fractions
ꢀ
T3 in organic/organicꢀwater
the volume
w
(f ,
percentage of water in organicꢀwater mixtures, that can adjust
the solvent polarity subtly). This is revealed by the images in
Scheme 1 Preparation of compounds T1, T2, T3
Fig.
recorded and shown in Fig.
absorption peaks in ethanol which located at ~293 nm and ~441
nm. Meanwhile, the spectra of the mixtures with high values
2
and Fig.
3
. The absorption spectrum of T1 has been
2
a. We can see that T1 shows two
f
w
start to show levelꢀoff tails in the long wavelength region
caused by the Mie scattering effect, which implies the
2
8
formation of nanoaggregates . Moreover, the two absorption
peaks of T1, T2 both red shift with the increasing of , which
ꢀ aggregation . As can be seen from the
f
w
2
9
Fig. 1 Linear absorption spectrum (a) and fluorescence spectrum (b) of T1 in five is the feature of the
organic solvents with different polarities at a concentration of 5×10 mol L .
J
-
5
-1
2
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Fig.
characteristic of absorption spectrum with T1
The fluorescence spectrum of T1 in the waterꢀethanol
mixture with different water contents were shown in Fig b,
which indicated obvious AIE properties when 50%. The
fluorescence intensity primarily decreased with increasing
when 50%, then increased with the increasing when
3a, T2 in organicꢀwater mixtures also shows similar
.
2
w
f ≥
f
w
Fig.4 Particle size distribution of T1 in mixtures with different water fractions: (a)
f
w
≤
f
w
f
w
≥
Water/Ethanol (30/70, v/v); (b) Water/Ethanol (50/50, v/v); (c) Water/Ethanol (95/5,
5
0%. The fluorescence intensity primarily decreased and the v/v). The inset depicts SEM images of T1 in Ethanol/Water mixtures with the same
water fractions as DLS
emission peak red shifted slightly with increasing
f
w
when fw
≤
5
0%, which could be attributed to the twisted intramolecular
3
0, 31,
To gain further insight into the influence of morphology and
particle size on AIE properties, we also carried on the scanning
electron microscope (SEM) and dynamic light scatting (DLS)
for T1 and T2 at different water fractions. The SEM images of
chargeꢀtransfer (TICT)
then the fluorescence intensity
increased and the emission peak showed remarkable redꢀshift
with the increasing when 50%, which could be ascribed to
the formation of a chargeꢀtransfer (CT) excited
formation of ꢀ aggregation. The inset depicts the changes of
integrated intensity with different water fractions. The
fluorescence spectrum of T2 in the waterꢀDMF mixtures with
f
w
w
f ≥
3
2, 33
and the
T1 were depicted in Fig.
aggregates were formed as a needleꢀlike nanoparticles in the
mixture solution when ≥ 30%, while a small globular
homogeneous nanoparticles formed immediately in the mixture
of = 95%, which implied the polarity of the solvent hold
4 (Inset), we could see that the
J
f
w
different water contents were shown in Fig.
that the fluorescence intensity of T2 was very weak and showed
almost no change as increases from 0% to 30%, while a
significant enhancement of fluorescence intensity was observed
in the waterꢀDMF mixture when > 30%, accompanying a
small redꢀshift in the spectrum. The highest fluorescence
intensity at = 50% was higher about 17.5ꢀfold than that in the
pure DMF solution. Subsequently, with increasing the water
fraction, the fluorescence intensity of T2 was slightly
decreased. This was also a typical AIE phenomenon but
different with that of T1, perhaps because of T1 itself owned
weak fluorescence in ethanol solution while T2 had no
fluorescence emission in pure DMF solution. But, T3 had no
AIE effect in various organic solvents mixed with different
proportions of water.
3b. We could see
f
w
important influence on the morphology of the aggregates. The
size distribution of T1 in the mixture solution with different
water fractions were conducted by DLS, which presented that
f
w
f
w
the average diameters (d) were 177.2 (
0%) and 67.8 ( = 95%) nm (Fig. 4), respectively. The results
showed that the orderly aggregates began to form with the
addition of water, the particle size increased when ≤ 50% and
decreased when 50%, thus led to the maximum
fluorescence intensity at = 95%. T2 also showed the similar
w w
f = 30%), 214.0 (f =
5
f
w
f
w
f
w
f
w
≥
f
w
size distribution influence on AIE properties in mixture solution
of DMF/water at different water fractions. The average
diameters (d) of T2 in different water fractions of DMF/water
mixtures were 172.4, 72.5 and 220.4 nm (Fig. S5), respectively.
The results were agreed with the fluorescence intensity changes
at different water fractions. All these results illustrated that the
particle size of aggregates had an important effect on their AIE
properties.
Mechanisms of emission enhancement
In order to better understand the relationship between the photo
physical properties and the molecular structure, single crystals
of T1 and T2 were obtained through slow evaporation of
methanol and acetonitrile solution at room temperature
respectively. The crystal structures of the two compounds were
Fig. 2 Absorption (a) and fluorescence (b) spectra of T1 in water/Ethanol mixtures with
-
5
fw at 5.0×10 M. The inset depicts the changes of fluorescence intensity with different
w
f .
shown in Fig.
5 and Fig. S6. Their crystallographic data were
summarized in Table S
3
.
Fig. 3 Absorption (a) and fluorescence (b) spectra of T2 in water/DMF mixtures with f
w
-
5
w
at 5.0×10 M. The inset depicts the changes of fluorescence intensity with different f .
Fig. 5 Crystal structure of T1 and T2, (a) single molecule structure of T1, (b) The 1D
linear structure of T1, (c) single molecule structure of T2, (b) The 1D linear structure of
T2.
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Open Z-scan experiment
To investigate the nonlinear optical (NLO) properties of T1
ꢀ
T3,
we conducted the open aperture Zꢀscan experiments by using a
femtosecond laser pulse in pure solution and in aggregates
respectively. While for Zꢀscan measurements, the quartzꢀglass
cell was 1.0 mm thick, and the average laser power was 500
mW. The results were showed in Fig.
8 and Fig. S7, the
Fig. 6 Proposed mechanism of enhanced emission in nanoparticles of T1
experimental data were illustrated in Table 1. The 2PA
coefficients (
β
)
for the three compounds were obtained
As shown in Fig. 5a and Fig. 5c, the dihedral angles between according to Eq. (4):
the plane of the terminal aromatic ring (P1) and the benzene
∞
m
[
−q (z)]
β I L
0 eff
ring (P2) of the triphenylamine was 1.858° for T1, and that of
the same position in T2 was 5.617°, while the dihedral angle of
another branch in T2 was 31.55°. The data indicated that T1
0
T(Z) =
,q (z) =
Eq.(4)
∑
3
0
2
2
2
(1+ z / z )a
0
m=0
(
m +1)
possessed good planarity in solid state excepting the other two Where
benzene rings while T2 only held the planarity in one branch. of the light at focus,
Their stacking structure were exhibited in Fig. 5b and Fig. 5d
is the linear absorption coefficient at the wavelength used.
it could be seen that multiple weak interactions including C8ꢀ Further, the molecular 2PA crossꢀsection could be
H8···π (ring: C13, C14, C15, C16, C17, C18) d= 3.12Å
determined through the Zꢀscan measurement by using the
and C18ꢀH18···O3 (d(H18···O3) =2.588Å, d(C18···O3) following Eq. (5):
3.246 Å, C18ꢀH18ꢀO3= 128.17º) played an important role
on molecular stacking. Benefit by these weak interactions and
partial planar structure, T1 and T2 both adopt the ꢀaggregation
Z
0
is the diffraction length of the beam,
I
0
is the intensity
L
eff is the effective length of the sample, a
,
(σ)
（
）
=
∠
3
σ
= hνβ ×10 / N d
Eq.(5)
A
J
Where
intensity,
concentration of the sample. From Table
all the three compounds possessed the enhanced 2PA properties
in aggregates compared with that in pure solution. It was
interesting that the 2PA property of T1 changed obviously from
pure solution to aggregates, which showed distinct aggregationꢀ
induced two photon absorption. Moreover, T2 displayed
remarkable enhancement of 2PA cross section that changed
from 947 GM in pure solution to 8314 GM in aggregates . All
these results illustrated that aggregation progress could be
applied in designing of 2PA materials especially for the
aggregation caused by branched compounds.
h
is Planck’s constant,
ν
is the frequency of input
with a head to tail model, which avoided strong πꢁꢁꢁπ stacking
and made for fluorescence emission in aggregation state. To
confirm these findings, we simulated the single molecule
structure of T1 and T2 in ethanol by theoretical calculation
N
A
is the Avogadro constant, and
d is the
1
, we could see that
3
4
(
Fig. 6 and Fig. 7) . Fig. 6 showed that T1 possessed extreme
distortion structure with a large dihedral angle (53.53°) between
the planes P1 and P2 in dilute ethanol solution. Compared with
that in crystal state, we could find that molecule aggregation
would result in the increment of the molecule planarity, which
enhanced ICT progress and was favourable for the formation of
ꢀaggregation. From Fig. 7, we could see that T2 had the
similar feature in dilute solution and in crystal. Thereby, we
could imagine that T3 also had the enhancement of planarity in
3
5
J
crystal but not tend to adopt Jꢀaggregation due to its steric
hindrance caused by threeꢀbranched substituent. In one words,
aggregation could enhance the molecule planarity and induce to
Cytotoxicity tests
Cytotoxicity was a potential side effect of compounds that must
be controlled when dealing with living cells or tissues.
Considering their application in cell imaging, the 3ꢀ(4, 5 ꢀ
dimethylthiazol ꢀ 2 ꢀ yl) ꢀ 2, 5 ꢀ diphenyltetrazolium bromide
form Jꢀaggregation，which could be explained the reason why
only T1 and T2 owned AIE properties while T3 did not. On the
other hand, T3 owned three nitro groups which possessed
strong electronꢀwithdrawing ability and always quenched
fluorescence. As a result, T3 did not reveal AIE behaviour due
to its rather weak fluorescence in aggregated state and in high
polar solvent such as DMF and ethanol.
3
6
(
MTT) assay was performed to ascertain the cytotoxic effect
of T1-T3 against HepG2 cells over a period of 24 h. Fig.
showed the cell viability for HepG2 cells treated with T1-T3 at
different concentrations. The results clearly indicated that no
9
Fig. 8 The open aperture Z-scan plot for T2 in aggregates (a) and in pure solution (b)
Fig. 7 Proposed mechanism of enhanced emission in nanoparticles of T2
4
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Table 1 2PA cross sections for T1-T3 in different states
ARTICLE
Compounds
T1
T2
820
T3
860
Wavelength(nm)
780
σ(GM) in pure solution
σ(GM) in aggregates
N/A
947
756
925
4986
8314
Fig. 10 (a1- a3) one-photon images of HepG2 cells incubated with T1-T3, (b1-b3) bright
field images of HepG2 cells with T1-T3, (c1-c3) two-photon images of HepG2 cells
incubated with T1-T3, (d1-d3) merged images of HepG2 cells incubated with T1-T3.
cytoplasm, which suggested that only the cell cytoplasm could
be labelled by these compounds.
Twoꢀphoton fluorescence microscopy provides key
advantages over oneꢀphoton fluorescence imaging, namely,
increased penetration depth, lower tissue autoꢀfluorescence and
selfꢀabsorption, and reduced photo damage and photo
3
7
bleaching . As shown in Fig. 10c, the two photon microscopy
images of HepG2 cells showed bright red fluorescence in
cytoplasm, but T2 owned better twoꢀphoton fluorescence
imaging ability than that of T1 and T3, which could be seen
from the Fig.10d, the merged pictures of oneꢀ and twoꢀphoton
microscopy. The photograph in Fig. 10d of T2 stained HepG2
cells showed obvious strong yellow fluorescence in cytoplasm,
while there was only partly yellow fluorescence in cytoplasm
stained by T1 and T3. The result could be explained by the
reason that the intracellular environment was water soluble
which led to aggregation of organic compounds easily, while
T1 and T2 possessed good AIE performance but T3 had no
AIE effect, hence T2 demonstrated excellent two photon bioꢀ
imaging performance.
Fig. 9 Cytotoxicity data obtained from the MTT assay in different concentrations for 24
h
obvious cell viability decreased, even when the concentrations
of the compounds reached up to 50 µM, the cell viability was
still greater than 90%. The low cytotoxicity of the target
compounds over a period of at least 24 h indicated it was
suitable for cellular imaging applications. This is an important
factor in further potential live cell imaging applications due to
their relatively low cytotoxicity.
Conclusion
One- and two-photon fluorescence microscopy cell imaging
To demonstrate the applicability of T1-T3 in cellular imaging, In this work, we reported a series of branched polar molecules
the bioꢀimaging experiments were carried out by confocal laser to realize 2PA and improve 2PA in aggregate through forming
scanning microscopy using HepG2 (human liver cancer cells)
Jꢀaggregation caused by the branched structure which
as an example, the tested compounds were dissolved in DMSO possessed partial planarity in one branch at solid state and fixed
and then serially diluted in complete culture medium. We steric hindrance in the other two branches. Their excellent 2PA
initially carried out timeꢀdependent twoꢀphoton fluorescence. and AIE properties made us successfully applied them in two
As a consequence, the three compounds all showed good photoꢀ photon bioꢀimaging. The structureꢀproperty relationship was
stability to laser power as the time went by, only ~15% signal summarized clearly and all the results displayed that the
deduction was observed (Fig. S
these compounds were very suitable for using in biological performance in aggregates by adjusting their structure
applications.
rationally and changing state, which could provide reference for
8
). The results indicated that branched compounds also possessed outstanding 2PA
Then we carried out bioꢀimaging studies in living HepG2 designing 2PA compounds.
cells stained with T1-T3 by both oneꢀ and twoꢀphoton
microscopy. The excitation wavelength was fixed at their Experimental section
maximum absorption wavelength in oneꢀphoton microscopy
Materials and measurements
imaging. As shown in Fig. 10a, bright green fluorescence with
similar intensity from the cells indicated that T1-T3 could be Chemicals were purchased and used as received. Every solvent
1
13
effectively internalized by HepG2 cells. The three compounds was purified as conventional methods beforehand. H,
C
all went through the membrane and localized uniformly in the
NMR were recorded on 400 MHz and 100 MHz NMR
instruments using DMSO as solvent. Chemical shifts were
reported in parts per million (ppm) relative to internal TMS (0
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ppm) and coupling constants in Hz. Splitting patterns were plated to ~70% confluence in 96ꢀwell plates 24 h before
described as singlet (s), doublet (d), triplet (t), quartet (q) or treatment. Prior to the compounds’ treatment, the dulbecco's
multiplet (m). The mass spectra were obtained on a Bruker modified eagle medium (DMEM) was removed and replaced
Autoflex III smart beam mass spectrometer. The Xꢀray with fresh DMEM, and aliquots of the compound stock
diffraction measurements were performed on a CCD area solutions (1 mM DMSO) were added to obtain final
detector using graphite monochromated MoKa radiation (
.71069 (Å) at 298 (2) K. The nonꢀhydrogen atoms were were incubated for 24 h at 37
refined anisotropically and hydrogen atoms were introduced Subsequently, the cells were treated with 5 mg / mL MTT (40
geometrically. Calculations were performed with SHELXTLꢀ97 µL/well) and incubated for an additional 4 h (37 , 5% CO ).
λ
=
concentrations of 5, 10, 20, 30 and 50 mM. The treated cells
0
℃
and under 5% CO .
2
℃
2
program package. Dynamic light scattering (DLS) Then, DMEM was removed, the formazan crystals were
measurements were conducted on a Malvern Zetasizer Nano dissolved in DMSO (150 µL/well), and the absorbance at 570
ZS90 size analyzer. The oneꢀphoton absorption (OPA) spectra nm was recorded. The cell viability (%) was calculated
were recorded on the UVꢀ3600 spectrophotometer. The oneꢀ according to the Eq. (5):
photon emission fluorescence (OPEF) spectra measurements
were performed using
spectrophotometer. The quartz cuvettes used were of 1 cm path
length. The slit pass width of emission spectra: 10 nm, Voltage:
a
Hitachi Fꢀ7000 fluorescence Cell viability(%) = OD570 (sample) ×100 Eq.(5)
OD570 (control)
Where OD570 (sample) represents the optical density of the
wells treated with various concentration of the compounds and
500 V. 2PA cross sections (σ) of the samples were obtained by
Open Aperture Zꢀscan method and Ti: sapphire system (680ꢀ OD570 (control) represents that of the wells treated with DMEM
1
080 nm, 80 MHz, 140 fs) as the light source.
+ 10% fetal calf serum (FCS). Three independent trials were
conducted, and the averages and standard deviations are
reported. The reported percent cell survival values are relative
to untreated control cells.
Synthesis
Synthesis of the intermediate 1-3. The compounds
1
,
2
and
3
were prepared according with the reported method.
Acknowledgments
Synthesis of compounds T1-3. Compound
1 (273 mg, 1
mmol) and 4ꢀNitrophenylacetonitrile (194 mg, 1.2 mmol) were This work was supported by The National Natural Science Fou
dissolved in 30 mL of absolute ethyl alcohol, then piperidine ndation of China (21271003, 21271004, 51432001 and 514720
was added in catalytic amount (1 mL) and the reaction mixture 02), Science and Technology Plan of Anhui Province (1604b06
was refluxed at 80 ºC for 2 h. After the reaction finished, the 02016), the Ministry of Education of the People’s Republic of
solvent was removed via vacuum filter and dried to give a red China, Higher Education Revitalization Plan Talent Project of
1
powder (379.44 mg, yield: 91%). T1: H NMR (DMSOꢀ
d
6
, 400 Anhui Province (2013).
MHz, ppm)
(
(
δ
: 6.95 (d,
t, 4H), 7.92 (d, = 8.4 Hz, 2H), 7.98 (d,
s, 1H), 8.32 (d,
: 103.70, 118.01, 119.21, 124.29, 125.10, 125.22,
25.96, 126.30, 129.94, 131.52, 140.84, 145.56, 145.69,
J
= 8.4 Hz, 2H), 7.17ꢀ7.23 (m, 6H), 7.42
J
J
= 8.4 Hz, 2H), 8.15 Notes and References
1
3
J
6
= 8.4 Hz, 2H). C NMR (DMSOꢀd , 100
1
2
J. L. Geng, C. C. Goh, N. D. Tomczak, J. Liu, R. R. Liu, L. Ma, L.
G. Ng, G.G. Gurzadyan and B. Liu, Chem. Mater., 2014, 26,
1874-1880.
X.Liu, Y. M. Sun, Y. H. Zhang, F. Miao, G. C. Wang, H. S. Zhao,
X. Q. Yu, H. Liu and W. Y. Wong, Org. Biomol. Chem., 2011, 9,
MHz, ppm)
δ
1
1
4
+
46.75, 150.37. MS (m/z): [M+H] , calcd: 418.1477; found,
18.1538.
3
615-3618.
T2 and T3 were obtained as red powders both over 90%
3
4
5
6
7
8
9
A. R. Morales, A. Frazer, A. W. Woodward, H. Y. A. White, A.
Fonari and K. D. Belfield, J Org. Chem., 2013, 78,1014-1025.
W. Huang, F. S. Tang, B. Li, J. H. Su and H. Tian, J.
Mater.Chem. C., 2014, 2, 1141-1148.
L. Kong, Y. P. Tian, Q. Chen, Q. Zhang, H. Wang, D. Tan, et al.
J. Mater. Chem. C, 2015, 3, 570-581.
T. Jiang, Y. Qu, B. Li, Y. Gao and J. Hua, RSC Adv., 2015, 5,
1
yield by following the similar procedure of T1
DMSOꢀ , 400 MHz, ppm) : 8.33ꢀ8.31 (d,
.21 (s, 2H), 8.01ꢀ7.98 (d, =8.4, 8H), 7.49ꢀ7.45 (t,
H), 7.32ꢀ7.29 (t, = 7.4 Hz, 1H), 7.23ꢀ7.21 (d,
.18ꢀ7.16 (d, = 8.0 Hz, 4H). C NMR (DMSOꢀ
: 148.88, 146.91, 145.27, 145.09, 140.47, 131.51,
30.24, 127.54, 126.69, 126.50, 126.01, 124.29, 122.56,
.
T2: H NMR
(
d
6
δ
J
= 8.0 Hz, 4H),
= 7.6 Hz,
=7.6, 2H),
, 100 MHz,
8
2
7
J
J
J
J
d
6
1
3
J
ppm)
δ
1
500-1506.
D. D. Li, Y. P. Zhang, Z. Y. Fan, J. Chen, J. H. Yu. Chem. Sci.,
2015, , 6097-6101.
1
+
117.71, 105.32. MS (m/z): [MH] , calcd: 590.1750; found
6
1
D. Zhang, Y. Gao, J. Dong, Q. Sun, W. Liu, S. Xue and W. Yang,
Dyes Pigments., 2015, 113, 307-311.
X. Zhang, X. Zhang, L. Tao, Z. Chi, J. Xu and Y. Wei, J. Mater.
Chem. B, 2014, 2, 4398–4414.
5
8
1
90.1750. T3
.34(d, = 8.4 Hz, 6H), 8.29(s, 3H), 8.08ꢀ8.02(q,
2H), 7.32ꢀ7.30(d,
：
H NMR (DMSOꢀ
d
6
,
400 MHz, ppm)
δ
: 8.36ꢀ
=7.4Hz,
=8.4 Hz, 6H). C NMR (DMSOꢀ , 100
J
J
1
3
J
d
6
MHz, ppm) δ: 106.35, 117.55, 124.33, 124.78, 126.75, 128.93, 10 Y. Hong, J. W. Y. Lam and B. Z. Tang, Chem. Soc. Rev., 2011,
+
1
31.64, 140.35, 145.22 147.11, 148.17. MS (m/z): [M+H] ,
40, 5361-5388.
1
1
1 C. W. T. Leung, Y. Hong, S. Chen, E. Zhao, J. W. Y. Lam and B.
Z. Tang, J. Am. Chem. Soc., 2013, 135, 62-65.
2 A. Qin, J. W. Y. Lam and B. Z. Tang, Prog. Polym. Sci., 2012,
37,
182-209.
calcd: 762.2023; found 762.9845.
Cytotoxicity assays in cells
To ascertain the cytotoxic effect of the three compounds, the
MTT assay was performed. HepG2 cells were trypsinized and
6
| J. Name., 2012, 00, 1-3
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Three branched dipole molecules (T1-T3) were designed and synthesized. Spectra
data showed that one- and two- branched molecule (T1 and T2) owned remarkable
AIE properties, which came from the formation of J-aggregation because of their
partial planarization in aggregation state. The open aperture Z-scan experiments
showed that T1 and T2 possessed excellent 2PA properties under aggregation state
and the largest 2PA cross section was 8314 GM for T2 in aggregates, which was
higher about 13-fold than that in pure DMF solution.