Synthesis, two-photon absorption and optical limiting properties of multi-branched styryl derivatives based on 1,3,5-triazine

Article abstract of DOI:10.1002/asia.201000536

Five new multi-branched two-photon absorption triazine chromophores (T1-T5) with different donor strength, conjugation length, and direction of charge transfer have been designed and synthesized. The one-photon fluorescence, fluorescence quantum yields, and two-photon properties have been investigated. The two-photon absorption (2PA) cross sections measured by the open aperture Z-scan technique were determined to be 447, 854, 1023, 603, and 766GM for T1, T2, T3, T4, and T5, respectively. This result indicates that their 2PA cross section values (I?) increase with increasing electron-donating strength of the end group, extending the conjugation length of the system, and introducing electron-withdrawing perfluoroalkyl as side groups to the end donor. In addition, the I? value of T5 is also larger than that of T1, which provides evidence that the I? value is relative to the direction of charge transfer (from the ends to the center of the molecule or from the center to the ends). Moreover, significant enhancement of the two-photon absorption cross section was achieved by introducing a thiophene moiety to a conjugated Ci￡?C bond. At the same time, the optical limiting behavior for these chromophores was studied by using a focused 800nm laser beam with pulses of 140fs duration. It was found that these molecules also exhibit good optical limiting properties. These initial results clearly demonstrate that multi-branched triazine chromophores are a highly suitable class of two-photon absorbing materials. Limiting the power! A series of new octupolar triazine molecules (T1-T5) containing multibranched styryl derivative moieties have been designed and synthesized. The two-photon absorption cross section values increase with increasing electron-donating strength of the end group, extending the conjugation length of the system, introducing electron-withdrawing perfluoroalkyl as side groups to the end donor, and making charge transfer from the center of the triphenylamine to the triazine ends possible. Copyright

Full text of DOI:10.1002/asia.201000536

DOI: 10.1002/asia.201000536
Synthesis, Two-Photon Absorption and Optical Limiting Properties of Multi-
branched Styryl Derivatives Based on 1,3,5-Triazine
Yihua Jiang,[a] Yaochuan Wang,[b] Bing Wang,[a] Jiabao Yang,[a] Nannan He,[a]
Shixiong Qian,[b] and Jianli Hua*[a]
Abstract: Five new multi-branched
two-photon absorption triazine chro-
mophores (T1–T5) with different
donor strength, conjugation length, and
direction of charge transfer have been
designed and synthesized. The one-
group, extending the conjugation
length of the system, and introducing
electron-withdrawing perfluoroalkyl as
side groups to the end donor. In addi-
tion, the s value of T5 is also larger
than that of T1, which provides evi-
dence that the s value is relative to the
direction of charge transfer (from the
ends to the center of the molecule or
from the center to the ends). More-
over, significant enhancement of the
two-photon absorption cross section
was achieved by introducing a thio-
phene moiety to a conjugated C=C
bond. At the same time, the optical
limiting behavior for these chromo-
phores was studied by using a focused
800 nm laser beam with pulses of
140 fs duration. It was found that these
molecules also exhibit good optical lim-
iting properties. These initial results
photon
fluorescence,
fluorescence
quantum yields, and two-photon prop-
erties have been investigated. The two-
photon absorption (2PA) cross sections
measured by the open aperture Z-scan
technique were determined to be 447,
854, 1023, 603, and 766 GM for T1, T2,
T3, T4, and T5, respectively. This result
indicates that their 2PA cross section
values (s) increase with increasing
electron-donating strength of the end
clearly
demonstrate
that
multi-
branched triazine chromophores are a
highly suitable class of two-photon ab-
sorbing materials.
Keywords: donor–acceptor
systems · multi-branched triazine ·
optical limiters · perfluoroalkyl ·
two-photon absorption
Introduction
tionships.[2] The significant issue is how to synthesize the ma-
terials with large 2PA cross section. Some efficient molecu-
lar design strategies were put forward to provide guidelines
for the development of materials with large two-photon ab-
sorption cross sections (s), including donor–acceptor–donor
(D–A–D)-type molecules, donor–p-bridge–acceptor (D–p–
A)-type molecules, donor–p-bridge–donor (D–p–D)-type
molecules, macrocycles, dendrimers, polymers, and multi-
branched molecules. These studies reveal that extending the
molecular conjugated system for charge transfer or incorpo-
rating multi-dipole or quadrupole chromophores into a mo-
lecular structure will increase the s value of a compound
while retaining the linear transparency over wide spectral
range.[3] Also, this is a beneficial feature especially for the
broadband optical limiting applications based on 2PA. Opti-
cal limiting is a significant area to protect human eyes and
delicate optical instruments from intense laser beams. An
ideal optical limiting material should strongly attenuate in-
tense and potentially dangerous laser beams, while exhibit-
ing high transmittance for low intensity ambient light. Up to
now, a number of organic materials have been found to ex-
The promising applications of organic two-photon absorp-
tion (2PA) materials in optical limiting, up-converted lasing,
microfabrication, 3D optical data storage, bioimaging, and
photodynamic therapy[1] have attracted considerable atten-
tion in the last decade. The applications of 2PA materials
stimulated substantial research on structure–property rela-
[a] Y. Jiang, B. Wang, J. Yang, N. He, J. Hua
Key Laboratory for Advanced Materials
Institute of Fine Chemicals and Department of Chemistry
East China University of Science and Technology
130 Meilong Road, Shanghai 200237 (China)
Fax : (+86)-21-64252758
E-mail: jlhua@ecust.edu.cn
[b] Y. Wang, S. Qian
Department of Physics
Fudan University
Shanghai 200433 (China)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201000536.
Chem. Asian J. 2011, 6, 157 – 165
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157

FULL PAPERS
hibit large 2PA cross section and excellent optical limiting
properties.[4] Thus, new compounds with strong two-photon
activities are crucially desired in order to realize full poten-
tial applications.
Triphenylamine has been widely used in opto- and elec-
tro-active materials for its good electron donating and trans-
porting capability, as well as its special propeller starburst
molecular structure.[5] N,N-dimethylbenzenamine can en-
hance the extent of electron delocalization and ability to
donate electrons of the 2PA compound. Structurally, the
thienyl group has richer p-electron density than the phenyl
group and higher chemical and thermal stability than the
furan or pyrrole groups, so the introduction of a thiophene
moiety was expected to enrich the p-electron density of the
system and improve the optoelectronic properties. It is well-
known that perfluoroalkyl groups of a strongly electron-
withdrawing nature can significantly decrease the energy
level of the lowest unoccupied molecular orbital (LUMO),
which enhances the materialsꢁ electron-accepting ability.
Also strong hydrophobic perfluoroalkyl groups lead to an
extended charge separation, in which large two-photon ab-
sorption cross-sections have often been associated with the
extent of conjugation length. However, to the best of our
knowledge, only a few examples of perfluoroalkyl substitut-
ed 2PA compounds have been reported in the past few
years.[6] On the other hand, 1,3,5-triazine-based compounds
show good optical and electrical properties owing to their
high electron affinity and symmetrical structure. In particu-
lar, octupolar molecules consisting of a strong triazine elec-
tron-accepting center and an electron-donating end group
linked through a p-conjugated bridge have been shown to
be excellent TPA materials.[7] In our previous work, we stud-
ied multibranched triarylamine end-capped triazines with
large two-photon absorption cross-sections.[8] To enrich the
research field of triarylamine derivatives with triazine ac-
ceptor and to gain more information about their structure–
property relationships, in this work, we have synthesized a
series of octupolar triazine molecules (T1–T5, Scheme 1)
containing multibranched styryl derivative moieties and in-
vestigated their optical properties.
Scheme 1. Structures of multibranched-triazine-based compounds (T1–
T5).
worth–Emmons reaction gave the target compounds (T1–
T4). Similarly, T5 was achieved by the condensation reaction
of 4,4’,4’’-nitrilotribenzaldehyde and dimethyl 4-(4,6-diACHTUNGTRENNUNG(p-
tolyl)-1,3,5-triazin-2-yl) benzylphosphonate (5). The final
compounds were purified by column chromatography and
recrystallization and characterized by 1H NMR, 13C NMR,
and HRMS, and they were obtained selectively as their E-
3
isomers as shown by the JH–H coupling constant of approxi-
mately 16.0 Hz between all vinylic protons.
One-Photon Absorption and Emission Properties
The UV/Vis absorption spectra of target compounds (T1–
T5) in CHCl3 at dilute concentration are shown in Figure 1.
Results and Discussion
Synthesis
The targeted compounds (T1–T5) were synthesized accord-
ing to Scheme 2. Bromination of 2,4,6-triACTHNUTRGNE(UNG p-tolyl)-1,3,5-tria-
zine afforded 2,4,6-tris(4-(bromomethyl)phenyl)-1,3,5-tria-
zine, followed by reaction with trimethyl phosphate, yielding
triazine derivative 1.[8] The important aldehyde 3 containing
perfluoroalkyl unit was synthesized similar to reported liter-
ature.[9] The intermediate aldehyde 4 was synthesized effi-
ciently by Suzuki coupling reactions between 4-bromo-N,N-
diphenylaniline and 5-formylthiophen-2-ylboronic acid.[10]
Finally, condensation of the respective aldehyde, 4-(N,N-di-
phenylamino)benzaldehyde,
hyde, 3, and 4 with triazine moiety (1) by the Horner–Wads-
4-(dimethylamino)benzalde-
Figure 1. Normalized one-photon absorption spectra of target compounds
in CHCl3.
158
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Multi-branched Styryl Derivatives Based on 1,3,5-Triazine
connected by a different mode
(such as T5 and T1), they show
two major prominent bands, ap-
pearing at 280–350 nm and at
400–480 nm, respectively. The
former is ascribed to a localized
multi-triazine aromatic p–p*
transition and the latter is of
charge-transfer character, in
which the absorption maximum
of T5 at 437 nm is red-shifted
by 16 nm compared with that of
T1 at 421 nm. It should be
noted that T2 exhibits the same
absorption maximum at 421 nm
as T1, although T1 has the
stronger
electron-donating
group of N,N-dimethylaniline.
This suggests that their UV/Vis
absorption was not only attrib-
uted to a strong ICT effect but
also the delocalization of intra-
molecular charge in the system.
Comparing the single-photon
absorption maximum of T1, T4
is blue-shifted with increasing
electron-withdrawing perfluor-
oalkyl as side groups to the end
triphenylamine donor, in which
a
stronger electron acceptor
would help to stabilize the
charge-separated excited state
of the molecule.
One-photon excited fluores-
cence spectra for these com-
pounds were recorded on
a
Varian Cary Eclipse fluores-
cence spectrophotometer using
dilute chloroform solutions and
the data are summarized in
Table 1. All the compounds
have strong one-photon fluores-
cence. As shown in Figure 2,
T1–T5 show an emission maxi-
mum at 535, 544, 575, 490, and
536 nm, respectively, whereby
Scheme 2. Synthetic routes to target compounds T1–T5.
the Stokes shifts vary from 4226
The corresponding data are presented in Table 1. All of the
compounds show their absorption maximum in the range of
370–450 nm as a result of p–p* transitions with the order
(T3>T5>T2=T1>T4). In general, the extension of the p-
systems exerts an important influence on the absorption
spectra. For example, the absorption maximum of T3 at
441 nm is red-shifted by 20 nm relative to that of T1, as T3
containing a thiophene moiety has a larger conjugation
length than T1. In addition, for some other compounds with
the same electron-donating and electron-accepting group
to 5370 cmꢀ1, which are also in agreement with the order of
the extension of the p-systems and the increase of electron-
donating ability of the donors: N,N-dimethylaniline>triphe-
nylamine>N,N-bis(4-(perfluorobutyl)phenyl)aniline. Differ-
ent from UV/Vis absorption, T2 shows a more red-shifted
maximum emission than T1 as a result of the stronger N,N-
dimethylaniline electron-donating ability, while T5 and T1
exhibits nearly the same emission maximum (e.g., T5,
436 nm; T1, 435 nm) owing to their same donor and accept-
or. The fluorescence quantum yields (Ff) of these molecules
Chem. Asian J. 2011, 6, 157 – 165
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J. Hua et al.
FULL PAPERS
Table 1. One-photon and two-photon properties of T1–T5.
Electrochemical Properites
T1
T2
T3
T4
T5
Figure 3 shows the cyclic voltammetry (CV) diagrams of the
compounds using 0.1m tetrabutylammonium hexafluoro-
phosphate as supporting electrolyte in THF solution with
labs,max [nm]
eꢂ10ꢀ4 mꢀ1 cmꢀ1
lem,max [nm]
Ff[a]
421
12.71
535
0.27
2.16
1.25
3.38
447
421
10.21
544
0.37
2.22
1.66
2.84
854
441
13.16
575
0.25
2.06
1.21
3.64
1023
580
395
15.01
490
0.86
1.83
4.69
0.77
603
437
9.95
536
0.32
2.23
1.43
3.05
766
542
t [ns][b]
[c]
Kr [108 sꢀ1
]
[c]
K
nr [108 sꢀ1
]
sTPA(GM)[d]
lTPF (nm)[e]
545
555
510
[a] The PL quantum yield (Ff) was estimated with rhodamine B in etha-
nol as a standard. [b] fluorescence lifetime (t). [c] Rate constants for ra-
diative (kr) and nonradiative (knr) decay. [d] Two-photon absorption
(TPA) cross section excited at 800 nm (140 fs) in 10ꢀ50 cm4 s per photon
(GM). [e] The maximum two-photon fluorescence (TPF) excited at
800 nm.
Figure 3. Cyclic voltammograms of T1–T5 in THF containing 0.1 molLꢀ1
of tetrabutylammonium hexafluorophosphate (TBAPF6).
platinum button working electrodes, a platinum wire coun-
ter electrode, and an SCE reference electrode. The SCE ref-
erence electrode was calibrated using a ferrocene/ferroceni-
um (Fc/Fc+) redox couple as an external standard. The elec-
trochemical properties as well as the energy level parame-
ters of T1–T5 are listed in Table 2. It can be observed from
Figure 2. Normalized one-photon emission spectra of target compounds
in CHCl3.
were measured with reference to rhodamine B in ethanol
and listed in Table 1. Interestingly, the Ff value of T4 is very
high (86%), suggesting that the flexible perfluorohexyl
chains not only function as solubilizing groups but also help
suppress the nonradiative decay pathways. In order to con-
firm the comment, we have measured the fluorescence life-
time (t) and determined the decay rate constants, in which
the rate constants for radiative (kr) and nonradiative (knr)
decays can be estimated from the fluorescence quantum
yields and lifetimes[11] using Equations (1) and (2) and are
included in Table 1:
Table 2. Electrochemical properties of T1–T5.
Compound
EHOMO[a] [eV]
E0ꢀ0[b] [eV]
ELUMO[c] [eV]
T1
T2
T3
T4
T5
ꢀ5.54
ꢀ5.34
ꢀ5.50
ꢀ5.61
ꢀ5.63
2.61
2.58
2.46
2.80
2.56
ꢀ2.93
ꢀ2.76
ꢀ3.04
ꢀ2.81
ꢀ3.07
[a] EHOMO were measured in THF with 0.1m tetrabutylammonium hexa-
fluorophosphate (TBAPF6) as electrolyte (working electrode: Pt; refer-
ence electrode: SCE; calibrated with ferrocene/ferrocenium (Fc/Fc+) as
an external reference. Counter electrode: Pt wire). [b] E0ꢀ0 was estimated
from the intercept of the normalized absorption and emission spectra.
[c] ELUMO is estimated by subtracting E0ꢀ0 to HOMO.
Kr
ð1Þ
Ffl ¼
Kr þ Knr
and
Figure 3 that the first half-wave potentials (Eox) of T1–T5
were 0.84, 0.64, 0.80, 0.91, and 0.93 V, respectively. There-
fore, the ground state oxidation potential corresponding to
the HOMO energy levels are ꢀ5.54, ꢀ5.34, ꢀ5.50, ꢀ5.61,
and ꢀ5.63 (vs vacuum), respectively, according to the equa-
t ¼ ðKr þ KnrÞꢀ1
ð2Þ
The value of knr for molecule T4 is lower than those of
the other compounds. The emission spectra for T4 exhibits a
blue shift with the introduction of electron-withdrawing per-
fluorohexyl chains, implying that the energy gap between
ground and excited states increases and electron recombina-
tion of the two states is more difficult. Thus T4 shows a rela-
tively low knr value.
tion HOMO=ꢀe
(Eox+4.7) (eV).[12] It is clear that the
ACHTUNGTRENNUNG
HOMO levels of T2 are higher than other compounds,
which is caused by the stronger electron-donating ability of
N,N-dimethylaniline. T1 and T3 showed a similar HOMO
energy level owing to their identical donor and acceptor.
However, T4 and T5, containing electron-withdrawing per-
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Chem. Asian J. 2011, 6, 157 – 165

Multi-branched Styryl Derivatives Based on 1,3,5-Triazine
fluoroalkyl and three triazine
moieties, respectively, possessed
relatively low HOMO energy
levels. Generally, the stronger
electron-donating ability of the
donor resulted in
a higher
HOMO energy level. On the
other hand, the introduction of
three triazine groups into T5
lowers the LUMO energy level
of the compound by increasing
the electron affinity.
Two-Photon Absorption
Properties
2PA cross sections of the T1–T5
were determined by the femto-
second open aperture Z-scan
technique according to a previ-
ously described method.[13] Fig-
ure 4a1–e1 shows the open-
aperture Z-scan data of T1–T5,
and the 2PA coefficient is ob-
tained by fitting of the data.
The 2PA cross section (s) can
be calculated by using the equa-
tion
s ¼ hnb=N0,
where
N0 ¼ NAC is the number densi-
ty of the absorption centers, NA
is the Avogadro constant and C
represents the solute molar
concentration. The values of s
for T1–T5 are 447, 854, 1203,
607, and 766 GM at 800 nm, re-
spectively (Table 1). The 2PA
cross section of T2 (854 GM) is
larger than T1 (447 GM), be-
cause the N,N-dimethylaniline
groups in compound T2 have a
stronger electron-donating abil-
ity compared with the triphe-
nylamine group in T1. It is
well-known that
strength electron acceptor/
donor will cause greater
degree of charge transfer in
a
higher
a
Figure 4. ACHTNUTRGNEUNG(a1–e1) Open aperture Z-
scan results for T1–T5 solutions in
CHCl3, respectively, using 800 nmfs
pulses (scattered circle experimental
data, straight line theoretic fitted
data). (a2–e2) TPF intensities of com-
pound T1–T5 under different excita-
tion power density, respectively. Inset
is TPF intensity versus the square of
the excitation power density.
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161

J. Hua et al.
FULL PAPERS
donor–acceptor systems, resulting in a higher nonlinear opti-
cal response.[14] The larger 2PA cross section of T3
(1023 GM) arises from the introduction of a thiophene
group in the p bridge, which extends the conjugate system
by importing hetero atoms. Interestingly, the s value of T4
is higher than that of T1, suggesting that the magnitude of s
can thus be controlled through the modification of the mo-
lecular structure in such a way as to affect the amount of in-
tramolecular charge transfer. In addition, the s value of T5
is also larger than that of T1, which provides evidence that
the s value is relative to the direction of charge transfer
(from the ends to the center of the molecule or from the
center to the ends). These results show that the strategy
through increasing electron-donating strength of the end
group, extending the conjugation length of the system, intro-
ducing electron-withdrawing perfluoroalkyl as side groups
to the end donor, and changing the direction of charge
transfer are effective approaches for enhancing 2PA cross
section of styryl derivatives-1,3,5-triazine-based star-shaped
molecules. Moreover, among these approaches, extending
the conjugation length by addition of a heterocycle is the
most effective way to increase the s value.
large 2PA at 800 nm, we investigated the relationship be-
tween the output intensity and the input intensity using
these five chromophores. The optical limiting properties of
five compounds, at concentrations of 0.0052 molLꢀ1,
0.00085 molLꢀ1, 0.00055 molLꢀ1, 0.0064 molLꢀ1, and
0.0021 molLꢀ1 for T1–T5, respectively, dissolved in CHCl3
solutions, were investigated by using the open-aperture Z-
scan technique, with 800 nm laser pulses of 140 fs pulse du-
ration. The measured relationships between the incident and
output fluence for these compounds are shown in Figure 5.
Figure 5. Measured output intensity versus input intensity of the 800 nm
laser pulses based on chromophores T1–T5; The points are the experi-
mental data, while the solid lines are the theoretical fits.
Under the excitation of 140 fs, 800 nm pulses, target com-
pounds in CHCl3 emit intense frequency up-converted fluo-
rescence with the maxima located in the range from 510 to
580 nm. (Table 1) The fluorescence could even be seen by
the naked eye under excitation of unfocused laser pulses
with energy of several mJ. The two-photon fluorescence
spectrum of the compounds T1–T5 under different laser in-
All these five compounds are shown to exhibit an optical
limiting behavior. At low incident energy, all five com-
pounds show a linear response of transmitted energy in ac-
cordance with Beerꢁs law, but the transmission deviates sig-
nificantly from linearity as the incident fluence increases.
We chose a power to carry out the measurement at which
pure CHCl3 solvent shows no detectable optical limiting be-
havior, indicating that the solvent contribution is negligible,
so the observed optical limiting properties can be assigned
solely to the compounds. Besides, it should be noted that
the concentrations in our measurements are relatively low
owing to the limit of solubility; hence, lower threshold
values could be attained if higher concentrations are used or
the compounds are deposited as thin films.
From the characteristic curves in Figure 5, one can see
why a two-photon absorbing medium can be used to stabi-
lize the laser pulse fluctuation. When the incident fluence
increase from ~0.0010 Jcmꢀ2 to ~0.042 Jcmꢀ2 (an increase
of about 42 times), the transmitted output fluences only
show 20-fold, 25-fold, 29-fold, 35-fold, and 35-fold increase
for compound T4, T1, T5, T2, and T3, respectively, which
fits the theoretically predicted optical limiting behavior
(solid lines) based on the 2PA. These results suggest that
this series of multi-branched compounds would provide at-
tractive potential in the optical limiting field owing to an en-
hanced two-photon response.
tensity is shown in Figure 4ACTHNURGTNE(UNG a2–e2). The linear dependence
of fluorescence intensity on the square of the excitation in-
tensity, as shown in the inset, confirms that 2PA is the main
excitation mechanism of the intense fluorescence emission.
Intense two-photon fluorescence was even observed at an
excitation intensity of about 1 GWcmꢀ2 (T4), indicating the
large 2PA cross section and high two-photon fluorescence
quantum yields. This is an important prerequisite for 2PA-
based applications such as fluorescence microscopy and up-
converted lasing. It should be noted that for the compounds
T1–T5, the two-photon excitation studies were performed at
one wavelength (800 nm), which is closer to the 2-fold labs,max
of T4. We can not measure the 2PA cross section profile at
different wavelengths at present because of the limit of our
laser apparatus. The cross sections for the other compounds
would be better conducted at their relative 2-fold labs,max
.
2PA-based Optical Limiting Properties
For some laser-based applications, such as optical communi-
cation, optical fabrication, and manufacturing, the intensity
or energy stability of the utilized laser beam is important.
This is because random intensity or power fluctuations may
be troublesome, especially from the standpoint of reproduci-
bility, for these applications. However, a strongly multi-
photon absorbing medium could be one of the approaches
used to reduce such fluctuation and stabilize the pulsed
laser signals.[2g] Since these chromophores have relatively
Conclusions
In conclusion, a series of new multi-branched triazine chro-
mophores containing styryl derivatives have been synthe-
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Multi-branched Styryl Derivatives Based on 1,3,5-Triazine
1H NMR (CDCl3, 400 MHz, TMS): d=8.71 (d, 6H, J=8.0 Hz), 7.51 (m,
6H), 3.61 (d, 18H, J=10.8 Hz), 3.30 ppm (d, 6H, J=22.0 Hz); 13C NMR
(CDCl3, 100 MHz, TMS): d=171.3, 136.3, 136.2, 135.0, 135.0, 130.1,
130.1, 129.3, 129.2, 53.1, 53.0, 33.9, 32.5 ppm; HRMS (EI) (m/z) calcd for
C30H36N3O9P3: 675.1664 [M]; found: 675.1663.
sized and characterized. Their linear and nonlinear optical
properties were investigated. One-photon absorption and
emission spectra revealed that the Stokes shifts for these
chromophores increased with an increasing extension of the
p-systems and increase of electron-donating ability of the
donors, whereas the fluorescence quantum yield exhibited
large increases with the introduction of electron-accepting
perfluoroalkyl as side groups to the end donor. Investigation
of the 2PA properties of these chromophores reveals that
their 2PA cross section values increase with increasing elec-
tron-donating strength of the end group, extending the con-
jugation length of the system, introducing electron-accepting
perfluoroalkyl, and making charge transfer from the center
of the triphenylamine to the triazine ends possible. In con-
junction with the increased fluorescence quantum yield, we
believe that the multi-branched triazine chromophore with
perfluoroalkyl moiety will provide a potential application in
two-photon fluorescence bioimaging. These molecules also
exhibit good optical limiting properties and make them po-
tential candidates for optical limiters in the photonics field.
4-[N,N-Bis(4-iodophenyl)amino]benzaldehyde (2). A modified version of
a previously reported method[8] was used. In a 500 mL three-necked
round-bottom flask, 4-(N,N-diphenylamino)benzaldehyde (14.00 g,
51.28 mmol), potassium iodide (11.43 g, 68.85 mmol), acetic acid
(210 mL), and water (20 mL) were heated to 808C. After stirring for 1 h,
potassium iodate (10.97 g, 51.26 mmol) was added and the reaction was
stirred at 808C for 4 h. The solution was allowed to cool and the solid
was collected, washed with water, and recrystallized from DCM/ethanol
(1:5) giving the product as a yellow powder (20.05 g, 75%). 1H NMR
(CDCl3, 400 MHz, TMS): d=9.89 (s, 1H), 7.75 (d, 2H, J=9.0 Hz), 7.67
(d, 4H, J=9.0 Hz), 7.09 (d, 2H, J=9.0 Hz), 6.93 ppm (d, 4H, J=9.0 Hz);
MS(EI) (m/z) calcd for C19H13I2NO: 524.9 [M]; found: 525.2.
4-(bis(4-(perfluorobutyl)phenyl)amino)benzaldehyde (3). In
a 100 mL
three-necked round-bottom flask, 2 (1.05 g, 2 mmol), copper powder
(3.64 g, 56.8 mmol), and 20 mL DMF were heated to 1258C under an
argon atmosphere. Then, perfluorobutyl iodide (4.43 g, 12.8 mmol) was
added and the reaction was stirred at 1258C for 2 h. The reaction was
stopped by adding water (20 mL). The mixture was filtered and washed
with water and ether. The combined organic phases were dried over an-
hydrous MgSO4 and concentrated using a rotary evaporator. The residue
was purified by column chromatography on silica (petroleum ether/di-
chloromethane=2:1, v/v) to yield the product as
a yellow powder
Experiment Section
(850 mg, yield: 60%). 1H NMR (CDCl3, 400 MHz, TMS): d=9.93 (s,
1H), 7.82 (d, 2H, J=8.4 Hz), 7.54 (d, 4H, J=8.4 Hz), 7.25 (d, 4H, J=
8,4 Hz), 7.19 ppm (d, 2H, J=8.4 Hz); 13C NMR (CDCl3, 100 MHz,
TMS): d=190.5, 151.6, 149.3, 132.0, 131.5, 128.6, 124.9, 124.7, 123.3 ppm;
19F NMR (CDCl3, 376 MHz, TMS): d=ꢀ81.89 (t, 18F, J=ꢀ7.52 Hz),
ꢀ111.48 (t, 12F, J=ꢀ11.28 Hz), ꢀ123.55 (d, 12F, J=ꢀ7.52 Hz),
ꢀ126.50 ppm (t, 12F, J=ꢀ11.28 Hz); MS (EI) (m/z) calcd for
C27H13F18NO: 709.1 [M]; found: 709.1.
Materials and Methods
Tetrahydrofuran (THF) was pre-dried over 4 ꢃ molecular sieves and dis-
tilled under argon atmosphere from sodium benzophenone ketyl immedi-
ately prior to use. Triethylamine was distillated under normal pressure
and dried over potassium hydroxide. N,N-dimethyl formamide (DMF)
and dichloromethane (DCM) were refluxed with calcium hydride and
distilled before used. Starting materials 2,4,6-triACTHNUGRTNEUNG(p-tolyl)-1,3,5-triazine
5-(4-(diphenylamino)phenyl)thiophene-2-carbaldehyde (4). In a 100 mL
three-necked round-bottom flask, 4-bromo-N,N-diphenylaniline (340 mg,
1 mmol), K2CO3 (1.38 g, 10 mmol), PdACTHNUGTRNEUNG(PPh3)4 (50 mg, 0.05 mmol), water
and 4-bromo-N,N-diphenyl-benzenamine were prepared according to
published procedures.[7c,10] All other chemicals were purchased from Al-
drich and used as received without further purification.
(5 mL), and THF (15 mL) were heated to 458C for 1 h under an argon
atmosphere. Then, 5-formylthiophen-2-ylboronic acid (187 mg, 1.2 mmol)
dissolved in 5 mL THF was added and the reaction was stirred at 458C
for 4 h. The mixture was washed with water and chloroform. The com-
bined organic layer was dried over anhydrous MgSO4 and concentrated
using a rotary evaporator. The resident was purified by column chroma-
tography on silica (petroleum ether/dichloromethane=1:1, v/v) to yield
Instrumentation
1H and 13C NMR spectra were recorded on a Bruker AM-400 spectrome-
ter using [D]chloroform as solvent and tetramethylsilane (d=0) as inter-
nal reference. The UV/Vis spectra were recorded on a Varian Cary 500
spectrophotometer with 2 nm resolution at room temperature. The fluo-
rescence spectra were taken on a Varian Cary fluorescence spectropho-
tometer. The cyclic voltammograms of compounds were obtained with a
Versastat II electrochemical workstation (Princeton applied research)
using a normal three-electrode cell with a Pt working electrode, a Pt wire
counter electrode, and saturated calomel electrode (SCE) reference elec-
trode in saturated KCl solution. TPA cross sections of T1--T5 were mea-
sured by femtosecond open-aperture Z-scan technique according to the
previously described method.[12] Two-photon excited fluorescence (TPF)
was excited by femtosecond pulses with different intensities at a wave-
length of 800 nm. The repetition rate of the laser pulses is 1 kHz and the
pulse duration is 140 fs.
the product as
a
yellow powder (300 mg, yield: 42%).1H NMR
(400 MHz, CDCl3): d=9.85 (s, 1H), 7.72 (d, 1H, J=4.00 Hz), 7.61 (d,
2H, J=8.40 Hz), 7.52 (d, 1H, J=4.00 Hz), 7.27–7.31 (m, 4H), 7.10–7.16
(m, 6H), 6.89 ppm (d, 2H, J=8.40 Hz).
4,4’,4’’-2,2’,2’’-(4,4’,4’’-(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))tris-
(ethene-2,1-diyl)tris(N,N-diphenylaniline) (T1). In
a 100 mL three-
necked round-bottom flask, 1 (267 mg, 0.35 mmol), 4-(diphenylamino)-
benzaldehyde (288 mg, 1.05 mmol), tBuOK (236 mg, 2.1 mmol), and di-
chloromethane (50 mL) were added and the reaction was stirred at 458C
for 4 h. The mixture was washed with water and chloroform. The com-
bined organic layers were dried over anhydrous MgSO4 and concentrated
using a rotary evaporator. The resident was purified by column chroma-
tography on silica (petroleum ether/dichloromethane=3:1, v/v) to yield
the product as a yellow powder (160 mg, yield: 40%). 1H NMR (CDCl3,
400 MHz, TMS): d=8.72 (d, 6H, J=8.4 Hz), 7.69 (d, 6H, J=8.4 Hz),
7.45 (d, 6H, J=8.4 Hz) 7.29 (d, 3H , J=16.0 Hz), 7.28–7.23 (m, 12H),
7.14–7.12 (m, 12H), 7.11 (d, 3H , J=16.0 Hz), 7.09-7.03 ppm (m, 12H);
13C NMR (CDCl3, 100 MHz, TMS): d=171.8, 148.5, 148.1, 142.4, 135.8,
131.7, 130.8, 130.4, 130.0, 128.4, 127.1, 127.0, 125.8, 125.4, 124.0, 123.9,
120.0, 111.4, 100.9 ppm; HRMS (ESI) (m/z) calcd for C81H60N6:
1117.4957 [M]; found: 1117.5000.
Synthesis
(4,4’,4’’-(1,3,5-Triazine-2,4,6-triyl)tris(benzene-4,1-diyl))tris(methylene)tri-
phosphonate (1). In a 100 mL round-bottom flask, 2,4,6-triACTHNUTRGNE(NUG p-tolyl)-1,3,5-
triazine (3.51 g, 0.01 mol), N-bromosuccinimide (NBS) (5.34 g, 0.03 mol),
and benzoyl peroxide (BPO) (0.3 g, 1.2 mmol) were dissolved into chlor-
obenzene (50 mL) and heated at 1108C for 7 h. The mixture was filtered
and the solvent was removed using a rotary evaporator. The resident was
dissolved into trimethyl phosphite (10 mL) and refluxed for 9 h. The ex-
cessive trimethyl phosphite was removed under vacuum. The residue was
purified by column chromatography on silica (ethanol/dichloromethane=
1:10, v/v) to afford the product as a white powder (5.3 g, yield: 78%).
4,4’,4’’-2,2’,2’’-(4,4’,4’’-(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-diyl))tris-
(ethene-2,1-diyl)tris(N,N-dimethylaniline) (T2). In
a
100 mL three-
Chem. Asian J. 2011, 6, 157 – 165
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
163

J. Hua et al.
FULL PAPERS
necked round-bottom flask, 1 (267 mg, 0.35 mmol), 4-(dimethylamino)-
benzaldehyde (156 mg, 1.05 mmol), tBuOK (236 mg, 2.1 mmol), and di-
chloromethane (50 mL) were added and the reaction was stirred at 458C
for 4 h. The mixture was washed with water and chloroform. The com-
bined organic layer was dried over anhydrous MgSO4 and concentrated
using a rotary evaporator. The resident was purified by column chroma-
tography on silica (petroleum ether/dichloromethane=3:1, v/v) to yield
the product as a yellow powder (82 mg, yield: 31%).1H NMR (CDCl3,
400 MHz, TMS): d=8.76 (d, 6H, J=8.4 Hz), 7.69 (d, 6H), 7.51 (d, 6H,
J=8.8 Hz), 7.26 (d, 3H, J=16.4 Hz), 7.05 (d, 3H, J=16.4 Hz), 6.77 (d,
6H, J=8.8 Hz), 3.04 ppm (s, 18H); 13C NMR (CDCl3, 100 MHz, TMS):
d=171.8, 151.1, 143.0, 135.3, 131.5, 130.0, 128.6, 126.8, 126.1, 124.4, 113.1,
41.1 ppm; HRMS (ESI) (m/z) calcd for C51H48N6: 744.5402 [M]; found:
745.4045.
nitrilotribenzaldehyde (115 mg, 0.35 mmol), tBuOK (236 mg, 2.1 mmol),
and 50 mL dichloromethane were added and the reaction was stirred at
458C for 4 h. The mixture was washed with water and chloroform. The
combined organic layer was dried over anhydrous MgSO4 and concen-
trated using a rotary evaporator. The resident was purified by column
chromatography on silica (petroleum ether/dichloromethane=3:1, v/v) to
yield the product as a yellow powder (133 mg, yield: 29%). 1H NMR
(CDCl3, 400 MHz, TMS): d=8.75 (d, 6H, J=8.4 Hz), 8.66 (d, 12H, J=
8.0 Hz), 7.69 (d, 6H, J=8.4 Hz), 7.52 (d, 6H, J=8.4 Hz), 7.38 (d, 12H,
J=8.0 Hz), 7.26. (d, 3H, J=16.0 Hz), 7.17 (d, 6H, J=8.4 Hz), 7.15 (d,
3H, J=16.0 Hz), 2.48 ppm (s, 18H); 13C NMR (CDCl3, 100 MHz, TMS):
d=172.1, 171.7, 147.6, 143.6, 142.2, 136.0,134.4, 132.8, 130.6, 130.0, 129.6,
128.5, 127.6, 127.2, 125.0, 22.4 ppm. HRMS (ESI) (m/z) calcd for
C93H72N10: 1329.6019 [M]; found: 1329.5973.
4,4’,4’’-(5,5’,5’’-2,2’,2’’-(4,4’,4’’-(1,3,5-triazine-2,4,6-triyl)tris(benzene-4,1-
diyl))tris(ethene-2,1-diyl)tris(thiophene-5,2-diyl))tris(N,N-diphenylani-
line) (T3). In a 100 mL three-necked round-bottom flask, 1 (267 mg,
Acknowledgements
0.35 mmol),
5-(4-(diphenylamino)phenyl)thiophene-2-carbaldehyde
(373 mg, 1.05 mmol), tBuOK (236 mg, 2.1 mmol), and dichloromethane
(50 mL) were added and the reaction was stirred at 458C for 4 h. The
mixture was washed with water and chloroform. The combined organic
layer was dried over anhydrous MgSO4 and concentrated using a rotary
evaporator. The resident was purified by column chromatography on
silica (petroleum ether/dichloromethane=3:1, v/v) to yield the product
as a yellow powder (204 mg, yield: 43%). 1H NMR (CDCl3, 400 MHz,
TMS): d=8.71 (d, 6H, J=7.4 Hz), 7.63 (d, 6H, J=7.4 Hz), 7.48 (d, 6H,
J=7.4 Hz), 7.35 (d, 3H, J=16 Hz), 7.30–7.26 (m, 12H), 7.14–7.05 (m,
30H), 6.98 ppm (d, 3H, J=16 Hz); 13C NMR (CDCl3, 100 MHz, TMS):
d=171.7, 148.2, 148.1, 144.6, 141.9, 141.8, 135.9, 130.1, 129.2, 128.7, 127.9,
127.7, 127.2, 127.0, 126.3, 125.9, 125.5, 125.4, 124.6, 124.1, 124.0,
123.5 ppm; HRMS (ESI) (m/z) calcd for C93H66N6S3: 1363.4511 [M];
found: 1363.4522.
This work was supported by NSFC/China (20772031), the Fundamental
Research Funds for the Central Universities (WJ0913001), PhD pro-
grams Foundation of Ministry of Education of China (200900741100004),
and the Scientific Committee of Shanghai (10520709700).
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0.35 mmol), 4-(bis(4-(1,1,3,3,4,4,4-heptafluorobutyl)phenyl) amino)ben-
zaldehyde (668.8 mg, 1.05 mmol), tBuOK (236 mg, 2.1 mmol), and di-
chloromethane (50 mL) were added and the reaction was stirred at 458C
for 4 h. The mixture was washed with water and chloroform. The com-
bined organic layers were dried over anhydrous MgSO4 and concentrated
using a rotary evaporator. The resident was purified by column chroma-
tography on silica (petroleum ether/dichloromethane=3:1, v/v) to yield
the product as a yellow powder (552 mg, yield: 71%). 1H NMR (CDCl3,
400 MHz, TMS): d=8.78 (d, 6H, J=8.4 Hz), 7.72 (d, 6H, J=8.4 Hz),
7.57 (d, 6H, J=8.4 Hz), 7.48 (d, 12H, J=8.4 Hz), 7.27 (d, 3H, J=
16.4 Hz), 7.21 (d, 12H, J=8.4 Hz), 7.19 (d, 3H, J=16.4 Hz), 7.16 ppm (d,
9H, J=8.4 Hz); 13C NMR (CDCl3, 100 MHz, TMS): d=172.8, 151.6,
147.4, 1423.0, 137.2, 135.7, 131.2, 131.1, 129.9, 129.8,128.4, 127.8, 124.9,
124.7, 124.5, 120.3, 115.4 ppm; 19F NMR (CDCl3, 376 MHz, TMS): d=
ꢀ81.91 (t, 18F, J=ꢀ7.52 Hz), ꢀ111.26 (t, 12F, J=ꢀ11.28 Hz), ꢀ123.59 (d,
12F, J=ꢀ7.52 Hz), ꢀ126.50 ppm (t, 12F, J=ꢀ11.28 Hz); HRMALDI-
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100 mL round-bottom flask, 2,4,6-triAHCUTNGTRENNUNG
ACHTUNGTRENNUNG
0.01 mol), NBS (1.78 g 0.01 mol), and BPO (0.1 g, 0.4 mmol) were dis-
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ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Chem. Asian J. 2011, 6, 157 – 165
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemasianj.org
165