Propeller-like D-π-A architectures: Bright solid emitters with AIEE activity and large two-photon absorption

Article abstract of DOI:10.1039/c4tc00933a

Two novel molecules TABzPA and TATpPA with D-π-A structure and large π-conjugation have been synthesized via Wittig reaction. Unlike common molecules, which exhibit the aggregation-caused quenching (ACQ) phenomenon, TABzPA and TATpPA exhibit aggregation-induced emission enhancement (AIEE) activity: weak luminescence in common solvents but strong emission when aggregated as nanoparticles and solid powders. Due to their intramolecular charge transfer (ICT) attribution and AIEE features, TABzPA and TATpPA display bathochromic effects. Combining ICT and AIEE features, these molecules are intensely yellow solid emitters with high quantum efficiencies of about 23.2% and 24.1%. Moreover, TABzPA and TATpPA have excellent two-photon absorption (2PA) properties owing to good planarity and large π-conjugation. The values of 2PA cross sections at 800 nm are 7590 GM and 7648 GM. The excellent optical properties of TABzPA and TATpPA pave the way for future potential applications in biophotonics and optoelectronics. This journal is the Partner Organisations 2014.

Full text of DOI:10.1039/c4tc00933a

Journal of
Materials Chemistry C
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PAPER
Propeller-like D–p–A architectures: bright solid
emitters with AIEE activity and large two-photon
absorption†
Cite this: J. Mater. Chem. C, 2014, 2,
6843
a
a
b
c
a
a
*
*
Wei Huang, Huan Wang, Lu Sun, Bo Li, Jianhua Su and He Tian
Two novel molecules TABzPA and TATpPA with D–p–A structure and large p-conjugation have been
synthesized via Wittig reaction. Unlike common molecules, which exhibit the aggregation-caused
quenching (ACQ) phenomenon, TABzPA and TATpPA exhibit aggregation-induced emission
enhancement (AIEE) activity: weak luminescence in common solvents but strong emission when
aggregated as nanoparticles and solid powders. Due to their intramolecular charge transfer (ICT)
attribution and AIEE features, TABzPA and TATpPA display bathochromic effects. Combining ICT and
AIEE features, these molecules are intensely yellow solid emitters with high quantum efficiencies of
about 23.2% and 24.1%. Moreover, TABzPA and TATpPA have excellent two-photon absorption (2PA)
properties owing to good planarity and large p-conjugation. The values of 2PA cross sections at 800 nm
are 7590 GM and 7648 GM. The excellent optical properties of TABzPA and TATpPA pave the way for
future potential applications in biophotonics and optoelectronics.
Received 6th May 2014
Accepted 24th June 2014
DOI: 10.1039/c4tc00933a
www.rsc.org/MaterialsC
tetraphenylethylene (TPE), which have been shown recently to
exhibit signicant enhancement of their light emission upon
Introduction
aggregation. The phenomenon was called aggregation-induced
emission (AIE).10 They thought the reason was that the intra-
molecular vibrational and rotational motions of the molecule
were restricted in the solid state.11 Therefore, some special 2PA
materials that both have large two-photon activity and over-
come uorescence quenching in aggregation have been
designed and synthesized. Recently, Prasad et al. have synthe-
sized aggregation-enhanced uorescence and 2PA materials
due to the hindering of molecular internal rotation.7,12 Tang
also found luminogenic polymers and nanoparticles of AIE and
2PA based on tetraphenylethene.13 Our group designed and
synthesized signicant AIE and 2PA compounds with triaryl-
amine as donor and cyano unit as acceptor.14
In recent years, organic materials with large two-photon
absorption (2PA) have drawn much attention due to their
photonic and biophotonic applications, such as 3D data
storage,1 up-converted lasing,2 power limiting materials,3 two-
photon bioimaging4 and so forth. A series of new compounds
with large 2PA cross sections (s) have been investigated both
experimentally and theoretically to realize their full potential
applications.5 Resulting from the hard work of scientists in the
past een years, the p-conjugated molecules with various
archetypes including quasi-linear, multibranched and dendritic
geometries have displayed good 2PA.6 The solvent polarity,
molecular planarity and hydrogen bonding also can
enhance 2PA.7
Triphenylamine is widely used as a donor in electroactive
materials, because of its good electron-donating and -trans-
porting capabilities, as well as its special propeller starburst
molecular structure.15 In recent decades, 2PA materials with
triphenylamine as donor have attracted much attention. Based
on recent work, we have synthesized two novel compounds
using 1,3,5-triazine as acceptor, triphenylamine as donor, and a
changing p-bridge with thiophene instead of benzene (see
Scheme 1). The high electron affinities and symmetrical struc-
ture of triazine have resulted in compounds with good optical
and electrical properties. Also, the thiophene bridge has given
the compounds a red shi16 in their absorption and the 2PA
values are higher than our previous work.17 These compounds
could be expected to have good potential applications in elec-
trical materials.18
However, it is necessary for the 2PA materials to be soluble or
dispersible and remain highly uorescent in aqueous media for
biophotonic applications.8 However, high efficiency 2PA mate-
rials have suffered from low uorescence efficiency or aggre-
gation-quenched emission (AQE).9 To solve this problem, Tang
et al. have found
a series of compounds containing
aKey Laboratory for Advanced Materials and Institute of Fine Chemicals, East China
University of Science & Technology, Shanghai, 200237, China. E-mail: tianhe@
ecust.edu.cn; Fax: +86-21-64252756; Tel: +86-21-64252756
bDepartment of Theoretical Chemistry, School of Biotechnology, Royal Institute of
Technology, S-10691 Stockholm, Sweden
cKey Laboratory of Polar Materials and Devices, Ministry of Education, East China
Normal University, Shanghai 200241, China
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c4tc00933a
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Scheme 1 Molecular structures of TABzPA and TATpPA.
Fig. 1 One-photon absorption spectra of TABzPA and TATpPA in THF
at a concentration of 1 ꢀ 10ꢁ5 M.
Results and discussion
Synthesis
The synthetic routes of compounds TABzPA and TATpPA are
shown in Scheme 2. The molecules were prepared via Wittig
reaction.19 The key intermediate compounds 1b and 2a were
synthesized according to the literature.17 All of the target
compounds were characterized by proton and carbon nuclear
magnetic resonance spectroscopy (1H NMR, 13C NMR) and
matrix-assisted laser desorption/ionization-time of ight mass
spectroscopy (MALDI-TOF) (see the ESI†).
Normalized absorption
Fig. 2 Normalized emission spectra of TABzPA (a), and TATpPA (b) in
different solvents excited at 428 nm and 450 nm at a concentration of
1 ꢀ 10ꢁ5 M, respectively.
The one-photon absorption spectra of TABzPA and TATpPA in
THF are displayed in Fig. 1. The peak wavelengths of the
compounds are at 426 nm and 445 nm, respectively. The
wavelength of TATpPA is red shied by 19 nm compared to
TABzPA, owing to the p-bridge of thiophene.
solvent effects of TABzPA and TATpPA. We used different
solvents by increasing the polarity from cyclohexane to tetra-
hydrofuran (THF) (losing emission in DMF). For example, the
emission of TABzPA peaked at 570 nm in cyclohexane and had a
bathochromic shi to 628 nm in THF. This solvatochromic
behaviour is typical for compounds with an internal charge
transfer upon excitation and has been fully documented for
numerous compounds containing D–p–A structure.20 A similar
phenomenon is observed for TATpPA. These solvatochromic
results indicate that signicant ICT effect exists in these
compounds.
Solvent effect
The solvent effect also can be usually observed in D–p–A
structural molecules. The effects of TABzPA and TATpPA were
investigated by changing the solvent polarity. Fig. 2 shows the
AIEE properties
To further investigate the aggregation-induced optical proper-
ties of TABzPA and TATpPA, we employed anhydrous THF as
good solvent and water as poor solvent, which are commonly
used in the study of AIE or AIEE behaviour. The dispersions of
nano-aggregates of TABzPA and TATpPA were prepared by the
precipitation method, adding water to a THF solution of the two
molecules. For compound TABzPA, concentration was kept at
1 ꢀ 10ꢁ5 M. As seen in Fig. 3a, uorescence is weak at water
fraction (fw) # 30%. When the fw > 30%, an obvious enhance-
ment is observed, which is related to the aggregated formation.
Finally, when fw ¼ 80% the photoluminescence (PL) intensity is
boosted to maximum with the peak located at 602 nm, which is
similar to the situation when fw ¼ 90%. This can indicate that
Scheme 2 Synthetic route of compounds TABzPA and TATpPA.
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Fig. 4 SEM images of TABzPA (a), and TATpPA (b), nano-aggregates
were prepared in fw ¼ 90% at a concentration of 1 ꢀ 10ꢁ5 M,
respectively.
different mixtures are shown in Fig. 5. For TABzPA, the PL
intensity increases when the cyclohexane fraction (fCYH) $ 30%
and the wavelength of emission (lem) is blue-shied with the
increase of fCYH (from 585 nm to 531 nm). It signies that the
polarity of the solution decreases when cyclohexane is added,
and the nano-aggregates are formed at a high fCYH. Both the
above mechanisms give signicant effects for the enhanced
emission. For the DMF–ethanol mixture, the PL intensity is very
low when ethanol fraction (fEtOH) < 80%; this is because DMF is
a strong polarity solvent. When the nano-aggregates are abso-
lutely formed in fEtOH ¼ 90%, the mixture gives a strong emis-
sion. A similar phenomenon also can be observed with TATpPA.
For biophotonic applications, the bioimages of HeLa cells
have been taken. Fig. 6 shows the cell imaging carried out by
confocal laser scanning microscopy (CLSM). It indicates that
bulky molecules are suitable for biophotonic applications.
However, TATpPA has better cell imaging ability than TABzPA.
This is because of the smaller size of nanoparticles when
aggregated in water (see SEM images Fig. 4). Moreover, such
bulky molecules encapsulated in a mixture of DSPE-PEG2000 and
DSPE-PEG5000-Folate can be applied in targeted cancer cell
imaging.29
Fig. 3 (a and d) The PL spectra of TABzPA and TATpPA excited at
428 nm and 450 nm, respectively, in different water fractions (fw) at a
concentration of 1 ꢀ 10ꢁ5 M. (b and e) Plot of (I/I0) values versus water
content of the solvent mixture for TABzPA and TATpPA. (c and f) The
absorptions of TABzPA and TATpPA in THF and fw ¼ 90% at
concentration of 1 ꢀ 10ꢁ5 M.
when fw ¼ 80%, all the nano-aggregates have been formed.
Denitely, the emission of TABzPA is induced by aggregation,
thus verifying its AIEE nature. In aggregated state, the intra-
molecular rotations are restricted, blocking the non-radiative
decay path and activating the radiative decay. Therefore, the dye
gives a strong emission. However, rotations of the diphenyl-
amine peripheries against the benzene core may effectively
deactivate the radiative decay in the excited state, resulting in
low emission when in the pure solvent.11 Possibly due to crys-
tallization of the dye, a strong and blue-shied emission of the
aggregates was exhibited.21
Fig. 3c shows the absorption of TABzPA in solution and
aggregation. In the nano-aggregate form (fw ¼ 90%), the
absorption is obviously broadened (lmax ¼ 442 nm) and is red-
shied by 17 nm compared with the solution (lmax ¼ 425 nm). A
quantitative I/I0 is made by calculating the integrands of the PL
spectra in different fws. The PL intensity of TABzPA is weak
when fw < 20%, but increases swily when fw > 20%. At fw ¼ 90%,
the intensity reached the highest value, with a 53-fold increase
(see Fig. 3b). The formation of the nano-aggregates can be
veried by scanning electron microscopy (SEM) (see Fig. 4). It
reveals that a nano-aggregated structure of the molecule has
been formed in high water content. A similar phenomenon is
observed for TATpPA and they show AIEE performance.
To further investigate the solvent effect of AIEE, the aggre-
gated states were studied in the other two conditions (THF–
cyclohexane and DMF–ethanol). The emission spectra in
Fig. 5 Emission spectra of TABzPA and TATpPA (excited at 428 nm
and 450 nm, respectively) in different mixtures (a, c THF–cyclohexane
and b, d DMF–ethanol) at a concentration of 1 ꢀ 10ꢁ5 M, Inset is the
plot of (I/I0) values in different ratios of poor solvent for TABzPA and
TATpPA at a concentration of 1 ꢀ 10ꢁ5 M, respectively.
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Fig. 6 Cell imaging of TABzPA (top) and TATpPA (bottom) in HeLa
cells: (a) 450 nm excitation; (b) overlap of image a and b; (c) bright field.
Fig. 8 (a and c) The 2PF emission spectra of TABzPA and TATpPA
under different excited power densities using a pulse at an 800 nm
wavelength in THF. (b and d) The relationship between the square of
the excited power density (I2) and the 2PF intensity.
Optical properties of solids
Vivid images of the solid powders can intuitively demonstrate
that they manifest the AIEE attribute. Fig. 7 shows the emission
spectra of compounds TABzPA and TATpPA in the solid state.
The solid powders were recrystallized from toluene. Both dyes
exhibit intense uorescence under 365 nm light illumination
(see insert images in Fig. 7) with peaks located at 595 nm and
612 nm, respectively. To quantitatively evaluate the uorescent
materials, the quantum efficiencies (FF) of the solids were
investigated. The values of FF were determined to be 23.2% and
24.1%, respectively. The high FF values make them potential
candidates in OLEDs.22
is a linear relationship between the square of power density (I2)
and the uorescence intensity. It proves that the phenomenon
is a process of 2PF.24 Fig. 9 shows the data tting of the open-
aperture Z-scan. The 2PA cross section values of TABzPA and
TATpPA are 7590 GM and 7648 GM, respectively, at a wave-
length of 800 nm. These values are higher than those of many
other materials.25 Otherwise, we have previously reported a
molecule, 3c (see SI Fig. 8†), whose value is 5782 GM. The
increase of the 2PA value is due to the improvement of the
donor and p bridges of the molecular structures.
Two-photon absorption properties
For a better explanation of the large 2PA cross sections, we
have calculated the molecular structures. The optimized
geometry is achieved through density functional theory (DFT) at
the B3LYP level together with a minor basis set 3-21 G. Fig. 10
shows the calculated dihedral angle of the molecules. The angle
between triazine and thiophene of TATpPA is 0.01ꢂ, which is
The 2PA cross sections of TABzPA and TATpPA were determined
by femtosecond open aperture Z-scan technique according to a
previously described method and calculated using the equation
s ¼ hvb/N0, where N0 ¼ NAC is the number density of the
absorption centers, NA is the Avogadro constant, and C is the
concentration of the solution.23 Fig. 8 shows the two-photon
uorescence (2PF) under different excited power densities.
Attributed to the AIEE effect, the intensity is low; however, there
Fig. 9 (a and c) Open-aperture Z-scan trace of TABzPA and TATpPA
(scattered circles ¼ experimental data, red lines ¼ theoretical fitted
Fig. 7 The normalized emission spectra of TABzPA and TATpPA as data). (b and d) The TPF emission spectra of TABzPA and TATpPA,
solid powders. Insert images are TABzPA and TATpPA as solid powders respectively, in mixed solution (fw ¼ 90%) at a concentration of 1 ꢀ
under 365 nm light illumination.
10ꢁ5 M excited by an 800 nm laser.
6846 | J. Mater. Chem. C, 2014, 2, 6843–6849
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due to the AIEE and ICT attributes. The good planarity and large
p-conjugation makes all molecules exhibit aggregation-
enhanced two-photon uorescence (2PF) and excellent two-
photon absorption (2PA). Their 2PA cross-section values at
800 nm are 7590 GM and 7648 GM. The excellent 2PA and solid
quantum efficiencies pave the way for use in potential uores-
cence materials.
Experimental section
Instruments
Fig. 10 Dihedral angles of TATpPA and 3c by calculation.
1H and 13C NMR spectra were measured on a Bruker AM-400
spectrometer using D-chloroform as solvent and tetramethylsi-
lane (TMS, d ¼ 0 ppm) as internal standard. The UV/Vis spectra
were recorded on a Nicolet CARY 100 spectrophotometer. The
PL spectra were taken on a Varian-Cary uorescence spectro-
photometer. The quantum yield for solid powders was
measured by Quanta-4 F-3029 Integrating Sphere. Further, the
2PA cross sections were measured by a femtosecond open-
aperture Z-scan technique according to a previously described
method. TPF was achieved using femtosecond pulses with
different intensities at a wavelength of 800 nm. The repetition
rate of the laser pulses was 250 KHz, and the pulse duration was
80 fs.
Fig. 11 (a) The one-photon fluorescence (OPF) emission photos of
TABzPA and TATpPA, respectively, at a concentration of 1 ꢀ 10ꢁ5 M, in
different ratios of water in THF under 365 nm light illumination. (b) The
two-photon emission (TPF) emission images of TABzPA and TATpPA,
respectively, in different ratios of water in THF excited by a 800 nm
laser.
Materials
THF was pre-dried over sodium for 24 h and then redistilled
under argon atmosphere with sodium benzophenone ketyl
prior to use. DMF was reuxed with calcium hydride and
distilled before use. Starting materials bis(4-uorophenyl)
methanone and diphenylamine were obtained from commer-
cial sources (J&K, Aldrich) and used without further purica-
tion. The key intermediate compounds were prepared
according to the previous published procedures.28
similar to 3c (the angle between triazine and benzene is 0.28ꢂ).
However, the angle of the p-bridge is different: the angle of
TATpPA between thiophene and the ethylenic bond is 15.5ꢂ,
which is smaller than 3c (the angle of 3c is 24.3ꢂ). The small
angle means that TATpPA has better planarity than 3c, so
TATpPA has a better 2PA cross section value.26 Moreover, due to
the better electronic ability and larger p-conjugated system,
TABzPA shows a larger 2PA cross section value.27 Two-photon
uorescence (TPF) has been examined for investigating the
aggregation effect on the two-photon activity (see Fig. 9). All
dyes exhibit yellow uorescence with peaks located at 611 nm
and 615 nm in mixed solvent (fw ¼ 90% THF and water) under
an excitation of 80 fs, 800 nm pulse. Fig. 11 shows the one- and
two-photon emission images in different water fractions of
solution. There is weak emission in pure THF, while in the
solutions of fw ¼ 90%, the dyes irradiate yellow emission. Due to
the limitation of our laser apparatus, only irradiation at the
wavelength of 800 nm was used to carry out the two-photon
excitation experiment. The 2PA cross sections for TABzPA and
TATpPA would be better at other wavelengths.
Synthesis
Bis(4-(diphenylamino)phenyl)methanone. In a three-neck
ask, diphenylamine 6.2 g (36.7 mmol) and sodium tert-bu-
toxide 5.28 g (55 mmol) were dissolved in 100 ml anhydrous
DMF;
a solution of bis(4-uorophenyl) methanone 4 g
(18.3 mmol) in 50 ml anhydrous DMF was slowly dropped into
the mixture under N2 atmosphere over 1 h. The reaction mixture
was reuxed for 10 h, upon cooling the mixture was poured into
200 ml ice water, then a deep yellow solid precipitate was
ltered off and washed with ethanol. Aer vacuum drying,
7.85 g yellow solid was obtained. Yield: 83%; 1H NMR (400 MHz,
CDCl3, TMS), d ¼ 7.74 (m, 4H), 7.35 (m, 8H), 7.22 (m, 8H), 7.14
(m, 4H), 7.02 (d, J ¼ 8.8 Hz, 4H).
(4-Bromophenyl)(4-(diphenylamino)phenyl)methanone. In a
250 ml three-neck ask, 6.7 g (27 mmol) was dissolvꢂed in 60 ml
Conclusion
Combining arylamines and triazine in typical propeller-like D– CS2. AlCl3 4.6 g (34.5 mmol) was slowly added at 0 C, and the
p–A architectures, two novel molecules TABzPA and TATpPA mixture was stirred for 30 min under N2 atmosphere. 4-Bro-
have been synthesized. Both compounds display the AIEE mobenzoyl chloride 5 g (22.8 mmol) was dissolved in 50 ml CS2
ꢂ
phenomenon; they have practically weak luminescence when then dropped into the ask. Aer reacting for 8 h at 0 C, the
dissolved in solvents but emit intensely upon aggregate mixture was poured into 200 ml water and extracted with DCM
formation. The solid quantum efficiencies are 23.2% and 24.1% (50 ml ꢀ 3). The combined organic layers were washed with
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water and dried with anhydrous MgSO4. The residue was puri- (5.4 mmol), 5.34 g NBS (17.1 mmol) and BPO (0.3 g, 1.2 mmol)
ꢂ
ed by column chromatography on silica (PE : DCM ¼ 3 : 1) to were dissolved into 50 ml chlorobenzene and heated at 110 C
give a yellow solid 7.41 g. Yield: 76%; 1H NMR (400 MHz, CDCl3, for 8 h. The mixture was ltered, and the solvent was removed
TMS), d ¼ 7.72 (m, 5H), 7.33 (t, J ¼ 7.8 Hz, 5H), 7.18 (d, J ¼ 7.5 under vacuum. The residue was dissolved into 10 ml triethyl
Hz, 6H), 7.00 (d, J ¼ 8.8 Hz, 2H).
phosphite and reuxed for 10 h. The excessive trimethyl phos-
4,40,400-(2-(4-Bromophenyl)ethene-1,1,2-triyl)tris(N,N-diphe- phite was removed under vacuum. In addition, the residue was
nylaniline). In a 100 ml three-neck ask, Zꢂn 1.5 g (23 mmol) was puried by column chromatography on silica with EA to afford
added to 40 ml anhydrous THF. At ꢁ10 C, 2.5 ml (23 mmol) the product as a white powder 2.43 g. Yield: 58%; 1H NMR (400
TiCl4 was injected under N2 atmosphere. The mixture was MHz, CDCl3, TMS), d ¼ 8.10 (d, J ¼ 12.1, 3H), 7.10 (t, J ¼ 3.6, 3H),
stirred for 3 h under reux, then bis(4-(diphenylamino) phenyl) 4.12 (dt, J ¼ 14.3, 7.1, 12H), 3.43 (d, J ¼ 21.5, 6H), 1.31 (t, J ¼ 7.1,
methanone 3 g (5.8 mmol) mixed with (4-bromophenyl) 18H).
(4-(diphenylamino) phenyl) methanone 1 g (2.3 mmol) in a THF
TABzPA. In a 25 ml ask, 600 mg (0.74 mmol) 1a, 170 mg
solution was slowly dropped into the mixture. The reaction (0.22 mmol) 1b, 124 mg (1.11 mmol) t-BuOK and 18-crown-6 (20
mixture was reuxed for 4 h; upon cooling, the mixture was mg, 0.08 mmol), and 100 ml DCM were ꢂplaced under N2
poured into 150 ml ice water. Aer ltering, the ltrate was atmosphere. The mixture was stirred at 45 C for 12 h. Upon
washed with DCM. The combined organic layers were washed cooling, the mixture was poured into water and extracted with
with water and dried over anhydrous MgSO4. The residue was DCM (30 ml ꢀ 3). The combined organic layers were washed
puried by column chromatography on silica (PE : DCM ¼ 4 : 1) with water and dried over anhydrous MgSO4, then concentrated
to give a light yellow solid 1.01 g. Yield: 48%; 1H NMR (400 MHz, using a rotary evaporator. The residue was puried by column
CDCl3, TMS), d ¼ 7.31–7.16 (m, 13H), 7.12–6.93 (m, 23H), 6.90– chromatography on silica (PE : DCM ¼ 4 : 1 v/v) to give a deep
6.76 (m, 10H). HRMS (m/z): [M]+ calcd for C62H47N3Br, 912.2953; yellow solid 285 mg. Yield: 45%; 1H NMR (400 MHz, CDCl3,
found, 912.2957.
TMS), d ¼ 8.78 (d, J ¼ 8.4, 6H), 7.71 (d, J ¼ 8.4, 6H), 7.38 (d, J ¼
4-(1,2,2-Tris(4-(diphenylamino)phenyl)vinyl)benzaldehyde (1a). 8.3, 6H), 7.25–7.20 (m, 36H), 7.14 (d, J ¼ 8.2, 6H), 7.07 (t, J ¼ 7.2,
In a 50 ml Schlenk reactor, 1.01 g (1.1 mmol) 4,40,400-(2-(4-bro- 36H), 7.03–6.91 (m, 42H), 6.89–6.81 (m, 18H). 13C NMR (CDCl3,
mophenyl)ethene-1,1,2-triyl)tris(N,N-diphenylaniline) was dis- 100 MHz, TMS), 121.07, 122.81, 122.99, 123.08, 123.54, 124.48,
solved in 30 ml anhydrous THF at ꢁ78 ꢂC. Aer 30 min, 0.6 ml 124.60, 125.89, 127.11, 128.34, 129.28, 129.91, 130.83, 131.27,
2.4 mol lꢁ1 n-BuLi in hexane was injected. Furthermore, aer 1 134.08, 134.42, 136.86, 138.14, 139.02, 142.39, 147.14, 147.44,
h, 0.23 g (3.3 mmol) anhydrous DMF was added, and the 147.52, 147.59, 149.73, 168.90, 170.56. MALDI-TOF: [M] calcd
mixture was stirred for 2 h under N2 atmosphere. Then the for C213H156N12: 2881.2576, found: 2881.2582.
mixture was taken out of the reactor and stirred overnight at
TATpPA. In a 25 ml ask, 618 mg (1 mmol) 2a, 257 mg
room temperature. The mixture was poured into water and (0.33 mmol) 2b, 168 mg (1.5 mmol) t-BuOK and 18-crown-6 (20
extracted with DCM (30 ml ꢀ 3). The combined organic layers mg, 0.08 mmol), and 100 ml DCM were placed under N2
ꢂ
were washed with water and dried over anhydrous MgSO4 and atmosphere. The mixture was stirred at 45 C for 12 h. Upon
concentrated using a rotary evaporator. The resident was puri- cooling, the mixture was poured into water and extracted with
ed by column chromatography on silica (PE : DCM ¼ 2 : 1) to DCM (30 ml ꢀ 3). The combined organic layers were washed
give a yellow solid 0.71 g. Yield: 75%; 1H NMR (400 MHz, CDCl3, with water dried over anhydrous MgSO4, then concentrated
TMS), d ¼ 9.82 (s, 1H), 7.92–7.79 (m, 4H), 7.24–7.13 (m, 20H), using a rotary evaporator. The residue was puried by column
6.81–6.69 (m, 24H).
chromatography on silica (PE : DCM ¼ 4 : 1 v/v) to give a deep
2,4,6-Tris(5-methylthiophen-2-yl)-1,3,5-triazine. To a 250 ml yellow solid 365 mg. Yield: 51%; 1H NMR (400 MHz, CDCl3), d ¼
three-neck ask, 0.81 g (33.8 mmol) Mg, 15 ml anhydrous THF 8.14 (d, J ¼ 3.9, 3H), 7.37–7.30 (m, 21H), 7.24–7.27 (m, 10H),
and a grain of iodine were added. 5 g (28.1 mmol) 2-bromo-5- 7.23–6.99 (m, 74H), 6.91 (s, 3H). 13C NMR (CDCl3, 100 MHz,
methylthiophene was dissolved in 50 ml anhydrous THF, and a TMS), 121.10, 122.84, 123.01, 123.57, 124.63, 125.92, 126.30,
few drops of this solution were added to the ask. All of the 127.13, 128.37, 129.31, 130.86, 131.29, 132.52, 134.11, 134.45,
solution was dropped slowly under N2 atmosphere aer the 136.89, 138.17, 139.05, 142.41, 147.18, 147.47, 147.55, 147.62,
reaction began. Aer stirring for 2 h at RT, 1.73 g (9.37 mmol) 149.75, 168.93, 170.56. MALDI-TOF: [M] calcd for C153H111N9S3:
2,4,6-trichloro-1,3,5-triazine dissolved in 50 anhydrous THF was 2169.8125, found: 2169.8143.
dropped, and the mixture was reuxed for 10 h. The mixture
was poured into water and extracted with DCM (50 ml ꢀ 3). The
Acknowledgements
combined organic layers were washed with water and dried over
anhydrous MgSO4, then concentrated using a rotary evaporator.
This work was supported by NSFC/China and the National Basic
The residue was puried by column chromatography on silica
Research 973 Program.
(PE : DCM ¼ 3 : 1) to give a light solid 2.8 g. Yield: 81%; 1H NMR
(400 MHz, CDCl3, TMS), d ¼ 8.05 (d, J ¼ 3.7, 3H), 6.88 (d, J ¼ 3.5,
3H), 2.58 (s, 9H).
Notes and references
Hexaethyl((5,50,500-(1,3,5-triazine-2,4,6-triyl)tris(thiophene-5,2-
diyl))tris(methylene))tris(phosphonate) (2b). In a 100 ml round-
bottom ask, 2,4,6-tris(5-methylthiophen-2-yl)-1,3,5-triazine 2 g
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