Synthesis and properties of novel borondipyrromethene (BODIPY)-tethered triphenylamine conjugates

Article abstract of DOI:10.1071/CH15026

A series of novel donor-acceptor type borondipyrromethene (BODIPY)-tethered triphenylamine conjugates (BDP4-8) containing one or two BODIPY cores attached to a triphenylamine scaffold at the 4- or 4,4′- positions were successfully synthesised via a mild a

Full text of DOI:10.1071/CH15026

CSIRO PUBLISHING
Aust. J. Chem.
Full Paper
http://dx.doi.org/10.1071/CH15026
Synthesis and Properties of Novel Borondipyrromethene
(BODIPY)-Tethered Triphenylamine Conjugates
A B
,
B C
,
A B
,
A C
,
Yucai Wang,
Junxu Liao,
Bangying Wang,
Hongbiao Chen,
B
B
B
Hongbin Zhao, Min Peng, and Sujuan Fan
A
College of Chemistry, Xiangtan University, Hunan 411105, China.
College of Chemistry and Environmental Engineering, Dongguan University
of Technology, Guangdong 523808, China.
B
C
Corresponding authors. Email: liaojunxu503@sina.com; zhaohbhanlf@163.com
A series of novel donor–acceptor type borondipyrromethene (BODIPY)-tethered triphenylamine conjugates (BDP4–8)
containing one or two BODIPY cores attached to a triphenylamine scaffold at the 4- or 4,40- positions were successfully
synthesised via a mild and effective protocol. Their photophysical and electrochemical properties were investigated. The
absorption spectra indicated that the meso-substituted BODIPY with triphenylamine did not give rise to an intense
intramolecular charge transfer (ICT) and did not effectively extend the conjugated length compared with substitution at the
2,6- and 3,5-positions as previously reported. It is worth noticing that the asymmetric mono-BODIPY-tethered
triphenylamine conjugates (BDP5, BDP7) showed an electronic distribution imbalance due to the special 3D propeller
shape of triphenylamine resulting in twisted molecular space configurations. In contrast, the symmetric bis-BODIPY-
tethered triphenylamine conjugates (BDP4, BDP6, and BDP8) exhibited a balanced electronic distribution. The
photoluminescence spectra of these conjugates exhibited significant Stokes shifts (5300–6700 cmꢀ1), which caused
fluorescence emission spectra in near-infrared regions. Cyclic voltammograms reveal that the asymmetric mono-
BODIPY-tethered triphenylamine conjugates (BDP5, BDP7) have higher LUMO energy levels and lower HOMO energy
levels, thus resulting in larger bandgaps than the bis-BODIPY-tethered triphenylamine ones.
Manuscript received: 28 January 2015.
Manuscript accepted: 12 March 2015.
Published online: 22 April 2015.
small molecule solar cells.[26] The 2,6-position TPA-modified
dyes benefit from a strong intramolecular charge transfer (ICT),
with the absorption spectra exhibiting an obvious red-shift
to near-red regions. However, to our best knowledge, TPA-
BODIPY conjugates with structural diversity and their resulting
property differences have not been systematic studied.
In this paper, we designed and synthesised five novel D-A
type BODIPY-tethered TPA conjugates (Scheme 1, BDP4–8)
involving one and two BODIPY groups linked at the meso-
position to a TPA framework at the 4- and 4,40-positions,
respectively. This novel system was designed in consideration
of the following: (i) first, previous studies have shown that
functional attachment of BODIPY derivatives with TPA at the
3,5- and 2,6-positions readily result in an obvious ICT. Whether
the meso-modified ones possess similar features aroused our
interest. (ii) Second, TPA features a 3D propeller shape, whether
this structure affects the BODIPY-tethered TPA conjugates and
their photophysical and/or electrochemical properties upon
introducing different numbers of BODIPY units onto the TPA
scaffolding drew our attention.
Introduction
Derivatives of borondipyrromethene (BODIPY) form an impor-
tant class of dyes subject to considerable interest owing to a
unique combination of facile synthesis, stability, high absorption
coefficient, and high photoluminescence efficiency.[1,2] In addi-
tion, the spectroscopic and photophysical properties of BODIPY
derivatives can be fine-tuned by the attachment of ancillary
residues at the appropriate positions of the BODIPY core[3–6] by
carrying out various synthetic reactions on BODIPY derivatives.
Recently, they have been shown as promising for a variety
of applications including biological labelling,[7–9] as electrolu-
minescent devices, as tunable laser dyes,[10] as potential
candidatesfor solid-state solarconcentrators,[11–15] asfluorescent
switches[16–19] and fluorophores in sensors, and as potential
photosensitisers in photodynamic therapy of cancer.[20–23]
We have also focussed on triphenylamine (TPA) and its deriva-
tives, which are well known for their 3D propeller shapes, high
hole-transporting and good electron-donating capabilities, and
have been widely used for hole injecting/transporting materials
for organic light-emitting diodes (LEDs) and organic solar
cells.[24,25] Consequently, the combination of BODIPY dyes
with a TPA moiety to construct donor–acceptor (D-A) type TPA-
BODIPY conjugates for photoelectronic applications has attrac-
ted interest. Moreover, we have recently reported BODIPY dyes
modified with TPA at the 2,6-positions, which exhibit good
absorption and promising photovoltaic properties in organic
Results and Discussion
Synthesis and Characterisation
BODIPY-tethered TPA conjugates (BDP4–8) were synthesised
according to the route illustrated in Scheme 1. First, according to
Journal compilation Ó CSIRO 2015
www.publish.csiro.au/journals/ajc

B
Y. Wang et al.
1) TCQ, DCM, rt
Pyrrole
InCl3, rt
N
N
N
N
POCl3, DMF
1:1
2) BF3 OEt2, Et3N, rt
N
N
H
F
B
N
F
O
NH
BDP4
Br
1
2
3
Br
Br
Br
N
1) TCQ, DCM, rt
Pyrrole
InCl3, rt
N
N
N
POCl3, DMF
1:1
2) BF3 OEt2, Et3N, rt
N
N
H
F
B
O
N
F
NH
BDP5
Br
4
5
6
Br
N
Br
N
1) TCQ, DCM, rt
Pyrrole
InCl3, rt
N
4
POCl3, DMF
1:10
2) BF3 OEt2, Et3N, rt
N
N
N
N
H
F
F
B
H
O
B
F
O
N
N
F
NH
HN
BDP6
7
8
C8H17
C8H17
S
S
SnBu3
S
9
C8H17
SnBu3
C8H17
S
9
BDP5
BDP6
N
Pd(PPh3)4, toluene
90ꢀC, 15 h
N
Pd(PPh3)4, toluene
90ꢀC, 15 h
N
N
N
B
F
F
F
F
B
B
F
N
F
N
N
BDP8
BDP7
Scheme 1. Synthesis of BDP4–8 (rt: room temperature, TCQ: 2,3,5,6-tetrachloro-1,4-benzoquinone).
the previous literature,[27] mono-formylation of 1 and 4 with
POCl3 and DMF readily afforded aldehydes 2 and 5. Similarly,
dialdehyde 7 was prepared by a bis-formylation reaction from 4.
Subsequently, dipyrromethanes 3, 6, and 8 were synthesised
from the corresponding aldehydes 2, 5, and 7 in a mild way
which was reported by our group in 2010.[28] Finally, a chelating
reaction between the dipyrromethanes and BF3-OEt2 in the
presence of 2,3,5,6-tetrachloro-1,4-benzoquinone (TCQ) led to
the target BODIPY derivatives BDP4–6. The desired BDP7 and
BDP8 were obtained by Stille coupling reactions between
tributyl(5-octylthiophen-2-yl)stannane (9) and BDP5 and BDP6,
respectively. All these intermediates and the novel final
BODIPY-tethered TPA conjugates are readily available.
Table 1. Fig. 1 shows the UV-vis absorption spectra of the
BODIPY-tethered TPA conjugates (BDP4–8) in diluted CH2Cl2
solution (10ꢀ5 mol Lꢀ1) and as a thin film. All these conjugates
show two distinct absorption bands. The first absorption regions
from 250 to 350 nm and centred at 300 nm in BDP4–6 can be
identified as the n–p* electronic absorption bands of the TPA
moiety, while the first absorption regions from 250 to 400 nm
and centred at ,350 nm in BDP7–8 were ascribed to the p–p*
transition bands derived from the TPA and thiophene fragments.
The second absorption bands of these conjugates in the long
wavelength regions with labs,max at 498, 500, 502, 483
and 501 nm, respectively, can be attributed to the faint ICT
interaction between the donor (TPA units) and the acceptor
(BODIPY units). Compared with the TPA-BODIPY dyads of
structurally substituted BODIPY with TPA at the 2,6- and 3,5-
positions, which exhibited an apparent red-shift at ,500 nm in
absorption spectra, the conjugates featured here with BODIPY
units meso-tethered to the TPA moiety show a similar absorption
profile to that of a free BODIPY dye in solution. These results
can be explained in that the intense electronic couplings between
UV-Visible Absorption Spectroscopy
With these novel BODIPY derivatives in hand, we first used
UV-vis and fluorescence spectroscopy to investigate their
photophysical properties in dilute CH2Cl2 solution and in thin
films on quartz plates. The UV-vis and photoluminescence
properties of these BODIPY derivatives are summarised in

BODIPY-Tethered Triphenylamine Conjugates
C
80
60
40
20
0
Table 1. Photophysical properties of BDP4–8 at room temperature
BDP4
BDP5
BDP6
BDP7
BDP8
Entry
SolutionA
FilmB
lCabs,max [nm] log eD leEm,max [nm] lCabs,max [nm] loFnset [nm]
BDP7
BDP4
BDP5
BDP6
BDP7
BDP8
498
500
502
483
501
5.12
4.60
5.21
4.69
5.04
758
738
516
512
523
489
514
676
615
678
577
667
684
675, 800
682
BDP6
BDP8
BDP5
AIn CH2Cl2.
BDeposited onto quartz substrate from CH2Cl2 solution by the spin-coating
BDP4
technique.
Clabs,max: maximum absorption wavelength of BDPs in CH2Cl2 solution or
film.
Dlog e: logarithmic molar absorption coefficient of BDPs in CH2Cl2
solution.
400
500
600
700
800
900
Wavelength [nm]
Elem,max: maximum emission wavelength of BDPs in CH2Cl2 solution.
Flonset: absorption threshold from absorption spectra of BDPs in thin film.
Fig. 2. Normalised fluorescence spectra of BDP4–8 in dilute CH2Cl2
solution.
(a)
2.0
the TPA and BODIPY units did not occur. In other words, the
effective conjugated length was not obviously increased by
attachment of BODIPY to the TPA scaffolding.
BDP4
BDP5
BDP6
On the other hand, it is worth noticing that structurally
asymmetric BDP5 and BDP7 show the first absorption bands
at 300 and 350 nm, respectively, as main absorption bands,
while the other structurally symmetric derivatives BDP4, BDP6,
and BDP8 exhibited the second absorption bands as the main
band. This phenomenon is probably related to the asymmetric
molecular structures breaking the ICT of the donor and acceptor.
Since TPA has a 3D propeller shape configuration, substitution
at one phenyl ring of the TPA moiety with BODIPY distorted
the normal ICT in the total molecule, which decreased the
electronic transition probability, thus caused a hypochromic
effect. For example, in comparison to BDP4, the introduction of
Br onto another phenyl ring of the TPA moiety to give BDP5
led to a hypochromic effect, and the characteristic absorption
of BODIPY at ,500 nm was obviously weakened. Interestingly,
two BODIPY moieties tethered to TPA (BDP6) enables the
whole intermolecular electronic transition to recover to a bal-
anced state (Fig. 1). Similarly, the BODIPY-tethered TPA
conjugates BDP7 and BDP8, which feature installation of an
electron-rich thiophene unit in another phenyl ring of the TPA
framework, also exhibited the same results.
BDP7
BDP8
1.5
BDP6
BDP4
1.0
0.5
0
BDP8
BDP5
BDP7
300
400
500
600
Wavelength [nm]
(b)
BDP5
BDP7
1.0
0.8
0.6
0.4
0.2
0
BDP4
BDP6
BDP5
BDP6
BDP7
BDP8
In comparison with the absorption spectra of the BODIPY
derivatives in CH2Cl2 solutions, these dyes in solid film dis-
played broadened and red-shifted absorption peaks at 516, 512,
523, 489, and 514 nm, respectively (Fig. 1, Table 1). The results
indicated that the effective conjugated length increased for the
BODIPY derivatives through 3D p–p stacking.
BDP8
BDP4
Fluorescence Spectroscopy of the BODIPY Derivatives
The fluorescence properties of all these BODIPY-tethered
TPA conjugates (BDP4–8) were studied in CH2Cl2 solution
(c ¼ 10ꢀ7 mol Lꢀ1) at room temperature. The normalised fluo-
rescence spectra of them are shown in Fig. 2. To our surprise,
except for BDP7, the other BODIPY-tethered TPA conjugates
show a significant Stokes shifts (5300–6700 cmꢀ1) resulting in
maximum emission peaks at 758, 738, 684, and 682 nm,
respectively (Table 1 and Fig. 2). This can be explained on the
basis of a photoinduced energy transfer from the BODIPY p–p*
300
400
500
600
700
800
Wavelength [nm]
Fig. 1. Normalised UV-vis absorption spectra of BDP4–8 in (a) dilute
CH2Cl2 solution and (b) thin film.

D
Y. Wang et al.
excited state to the lower lying singlet excited state of TPA and/
or to the existence of new non-radiative pathways from the
BODIPY p–p* state to the ground state, and this process
increased phonon coupling.[29] The results show the promise
for practical applications of these BODIPY-tethered TPA
conjugates as near-infrared fluorescence emission materials.
BDP7 was also excited at the maximum absorption peak
(labs,max ¼ 483 nm), although there were two small emission
peaks at 675 and 800 nm, respectively, while an anti-Store shifts
phenomenon was observed to result in a maximum emission
peak at 404 nm (Fig. 2). This may be caused by the unbalance of
donor and acceptor moieties and the twisted molecular config-
uration, which inhibited the intramolecular electron transfer. On
the other hand, BDP4–8 gave low fluorescent quantum yields.
This could be attributed to the increased internal conversion
according to the energy gap law that states that the non-radiative
deactivation probability of S0–S1 increases as the energy gap of
S0–S1 decreases in a highly extended conjugating system.
(a)
100
BDP4
BDP5
BDP7
50
0
ꢁ50
ꢁ100
ꢁ150
ꢁ200
Fc
Electrochemical Properties of the BODIPY Derivatives
In order to investigate the electrochemical behaviours of these
BODIPY-tethered TPA conjugates, the electronic states of
compounds BDP4–8 were studied by cyclic voltammetry in
CH2Cl2 (Fig. 3) and the results are summarised in Table 2.
The potentials are reported versus ferrocene as an internal
standard and potentials were calibrated by addition of 0.63 eV to
the potential (versus scanning calomel electrode, SCE) versus
Fc/Fcþ. It can be seen that the E
and Eopx of the five conju-
ꢁ1.5
ꢁ1.0
ꢁ0.5
0
0.5
1.0
1.5
ox
onset
Potential [V]
gated dyes were all measured at around 1.16 and 1.27 eV,
respectively, except for BDP4 (Table 2), indicating that the
different groups substituted on the TPA moiety had an obvious
effect on the Eox. Their corresponding HOMO (highest occupied
(b)
100
50
BDP6
BDP8
molecular orbital) energy level was calculated as approximately
ox
ꢀ5.6 eV from the equation EHUMO ¼ E
þ 4.4 eV. The results
onset
suggest that these BODIPY-tethered TPA conjugates are actu-
ally located at a higher energy than we previously reported for
BODIPY derivatives substituted with TPA moieties at the 2,6-
positions (around ꢀ5.35 eV), implying that the HOMO level is
sensitive to the positions of the TPA substituent on the BODIPY
core of these dyes, which is consistent with the spectroscopic
analysis results above. By neglecting any entropy change during
light absorption, the reduction potential versus the normal
hydrogen electrode (NHE) (Ered), which corresponds to the
0
ꢁ50
ꢁ100
ꢁ150
ꢁ200
Fc
lowest unoccupied molecular orbital (LUMO versus NHE), can
ox
be obtained from E
onset
and Eg, and the calculation results are
ꢁ1.5
ꢁ1.0
ꢁ0.5
0
0.5
1.0
1.5
listed.
Potential [V]
Conclusion
Fig. 3. Cyclic voltammograms of (a) BDP4, BDP5, and BDP7 and (b)
BDP6 and BDP8 in CH2Cl2, containing 0.1 M n-Bu4NPF6 as the supporting
electrolyte recorded at a scan speed of 50 mV sꢀ1, Fcþ/Fc refers to the
ferricinium/ferrocene couple used as internal reference.
In summary, a series of novel BODIPY-tethered TPA con-
jugates (BDP4–8) containing one or two BODIPY cores
attached onto a TPA scaffold at the 4- and 4,40- positions were
Table 2. Solution electrochemical properties of BDP4–8
HOMO/LUMOE [eV]
ox
onset
Entry
Eg A [eV]
E
B [eV]
Eopx C [V]
Ered D [V] vs NHE
BDP4
BDP5
BDP6
BDP7
BDP8
1.83
2.01
1.83
2.15
1.86
1.25
1.35
1.27
1.26
1.31
1.27
ꢀ1.28
ꢀ1.32
ꢀ1.27
ꢀ1.30
ꢀ1.23
ꢀ5.65/ꢀ3.82
ꢀ5.57/ꢀ3.56
ꢀ5.54/ꢀ3.81
ꢀ5.59/ꢀ3.44
ꢀ5.55/ꢀ3.69
1.17
1.14
1.19
1.15
AEnergy bandgap, determined from UV-vis absorption spectra. At absorption maxima (Eg ¼ 1240/lonset).
B
ox
onset
E
, onset oxidation potential.
CEopx, oxidation peak potential.
DEred, the reduction potential.
EHOMO ¼ ꢀ(E
þ 4.4 eV); LUMO ¼ HOMO þ Eg eV.
ox
onset

BODIPY-Tethered Triphenylamine Conjugates
E
successfully synthesised. The absorption spectra indicated that
the meso-substituted BODIPY with TPA did not give rise to
an intense ICT and did not extend the effective conjugated
length obviously. It was worth noticing that the asymmetric
mono-BODIPY-tethered TPA conjugates (BDP5, BDP7)
showed an electronic distribution imbalance due to the special
3D propeller shape of the TPA which resulted in a twisted
molecular configuration. In contrast, the symmetric bis-
BODIPY-tethered TPA conjugates (BDP4, BDP6, and BDP8)
mixture was cooled to room temperature and poured into water
(10 mL). A yellow precipitate was then formed by adjustment of
the pH of the solution to 7 with saturated Na2CO3. This
suspension was filtered to give a yellow solid. Recrystallisation
from ethanol afforded a needle-like pale yellow solid (1.00 g,
yield 92 %). dH (400 MHz, CDCl3 TMS) 9.86 (s, 1H), 7.71–7.73
(d, J 8.0, 2H), 7.11–7.40 (m, 10H), 7.04–7.06 (d, J 8.2, 2H). The
characterisation data were consistent with the literature.
showed
a balanced electronic distribution. The photo-
4-((4-Bromophenyl)(phenyl)amino)benzaldehyde (5)
luminescence spectra of these conjugates exhibited significant
Stokes shifts (5300–6700 cmꢀ1) and caused fluorescence
emission spectra in near-infrared regions, as such they show
promise for practical applications in near-infrared fluorescence
emission materials. Cyclic voltammograms reveal that the
asymmetric mono-BODIPY-tethered TPA conjugates (BDP5,
BDP7) have higher LUMO energy levels and lower HOMO
energy levels than the bis-BODIPY-tethered TPA ones.
The aldehyde 5 was synthesised by a similar procedure to
prepare aldehyde 2 using 4 as a reactant. The desired compound
5 was obtained as a pale yellow solid in 89 % yield. dH
(400 MHz, CDCl3, TMS) 9.85 (s, 1H), 7.71 (d, J 8.0, 2H),
7.47 (d, J 8.0, 2H), 7.39–7.35 (m, 2H), 7.23–7.16 (m, 3H),
7.07–7.03 (m, 4H). dC (101 MHz, CDCl3) 190.4, 152.9, 145.9,
145.4, 132.8, 131.4, 130.2, 129.9, 127.4, 126.3, 125.4, 120.0,
117.7. The characterisation data were consistent with the
literature.[30]
Experimental
4,40-((4-Bromophenyl)azanediyl)dibenzaldehyde (7)
Materials
According to the literature,[31] to a solution of 4-bromo-N,N-
diphenylaniline (650 mg, 2 mmol) and DMF (5 mL) was added
POCl3 (9 mL, 20 mmol) dropwise at 08C with stirring, during
this process, a precipitate was formed. After addition was
completed, the mixture was warmed to 458C and stirred at this
temperature for 2 h. The mixture was cooled to room tempera-
ture, poured into water (20 mL), and extracted with CH2Cl2
(20 mL ꢁ 2). The organic extracts were washed with brine
(20 mL ꢁ 2) and water (20 mL ꢁ 2), dried with anhydrous
Na2SO4, and concentrated. The residue was purified by silica
gel column chromatography (petroleum ether/CH2Cl2, 10 : 1) to
give the desired 7 as a light yellow solid (618 mg, yield 81 %). dH
(400 MHz, CDCl3 TMS) 9.88 (s, 2H), 7.80–7.78 (d, J 8.0, 4H),
7.15–7.50 (m, 6H), 7.04–7.06 (d, J 8.2, 2H). The characterisa-
tion data were consistent with the literature.[31]
TPA, 4-bromo-N,N-diphenylaniline, tributyl(5-octylthiophen-
2-yl)stannan pyrrole, and phosphorus oxychloride were
purchased from Alfa Aesar. Dichloromethane, toluene, and
N,N-dimethylformamide (DMF) were dried by the accustomed
methods and distilled before use. Pyrrole was distilled over
CaH2 before use. All other chemical materials were of reagent
grade and used as received without further purification. All
chromatographic separations were carried out on silica gel
(300–400 mesh).
Instrumentation
1H and 13C NMR spectra were recorded on a Bruker Avance
spectrometer (400 and 101MHz, respectively) with tetra-
methylsilane (TMS) as the internal standard. Matrix-assisted
laser desorption–ionisation time of flight mass spectra (MALDI-
TOF-MS) were recorded on a Bruker Ultraflex-II spectrometer,
using an a-cyano-4-hydroxy-cinnamic acid (a-CHCA) matrix.
Absorption spectra were recorded on an SHIMADZU UV-2550
UV-Vis spectrophotometer and emission spectra were recorded
by using a Hitachi F-4500 instrument. Excitation and emission
spectra were fully corrected by reference to a standard lamp.
Electrochemical studies made use of cyclic voltammetry (CV)
with a conventional three electrode system using a BAS 100W
electrochemical analyser in deoxygenated and anhydrous
CH2Cl2 at room temperature. The potentials are reported versus
ferrocene as an internal standard and potentials are calculated
relative to SCE assuming E1/2 Fc/Fþc ¼ 0.63 V versus SCE using
a scan rate of 100 mV sꢀ1, a glassy carbon working electrode,
a Hg2Cl2/KCl reference electrode, a platinum counter electrode,
and the sample solutions contained 1.0ꢁ 10ꢀ3 M sample and
0.1 M tetrabutylammonium hexafluorophosphate as a supporting
electrolyte.
4-(Di(1H-pyrrol-2-yl)methyl)-N,N-diphenylaniline (3)
According to the literature,[28] a mixture of pyrrole (14 mL,
150 mmol) and 4-(diphenylamino)benzaldehyde (2) (546 mg,
2.0 mmol) was treated with InCl3 (44 mg, 0.2 mmol) at room
temperature under argon. After stirring for 2 h, powdered NaOH
(400 mg, 10 mmol) was added to terminate the reaction. The
literature procedure was then followed to give a brown solid
(750 mg). This solid was used directly for the next step without
further purification.
4-Bromo-N-(4-(di(1H-pyrrol-2-yl)methyl)phenyl)-N-
phenylaniline (6)
Dipyrromethane 6 was synthesised by a similar procedure for
preparing dipyrromethane 3. A mixture of pyrrole (14 mL,
150 mmol) and dialdehyde 5 (704 mg, 2 mmol) was treated with
InCl3 (44 mg, 0.2 mmol) at room temperature under argon. After
stirring for 2 h, powdered NaOH (400 mg, 10 mmol) was added
to terminate the reaction. Pyrrole was removed under reduced
pressure, and the residue was purified by silica gel column
chromatography (petroleum ether/CH2Cl2, 1 : 1) to give the
desired product 3 as a pale brown solid (935 mg, yield 91 %).
dH (400 MHz, DMSO) 7.95 (s, 2H), 7.31 (d, J 7.7, 2H), 7.24 (d, J
7.4, 2H), 7.09–7.07 (m, 3H), 7.04 (d, J 8.8, 2H), 6.99 (d, J 8.0,
2H), 6.93 (d, J 7.8, 2H), 6.70 (s, 2H), 6.16 (s, 2H), 5.93 (s, 2H),
Synthesis
4-(Diphenylamino)benzaldehyde (2)
According to the literature,[27] to a solution of TPA (980 mg,
4 mmol) and DMF (2 mL) was added POCl3 (1.8 mL, 4 mmol)
dropwise at 08C with stirring. During this process, a precipitate
was formed. After addition was completed, the mixture was
warmed to 458C, and was stirred at this temperature for 2 h. The

F
Y. Wang et al.
5.41 (s, 1H). dC (101 MHz, DMSO) 147.29, 146.93, 146.13,
136.80, 132.64, 132.22, 129.47, 129.32, 125.23, 124.54, 124.20,
123.40, 117.37, 114.90, 108.46, 107.24, 43.42. m/z (MALDI-
TOF-MS) 467.135. Calc. for C27H22BrN3: 467.100.
dH (400 MHz, CDCl3) 7.95 (s, 4H), 7.57–7.55 (m, 6H), 7.28 (d,
J 9.9, 4H), 7.18 (d, J 8.1, 2H), 7.05 (s, 4H), 6.58 (s, 4H). dC
(100 MHz, CDCl3, TMS) 149.24, 146.66, 145.11, 143.72,
134.75, 133.30, 132.36, 131.16, 128.84, 128.07, 122.82,
118.79, 118.40. m/z (MALDI-TOF-MS) 684.148 ([M ꢀ F]þ).
Calc. for C36H24B2BrF4N5: 703.13. HRMS m/z 684.1369
([M ꢀ F]þ); calc. for C36H24B2BrF4N5 684.1353 ([M ꢀ F]þ).
4-Bromo-N,N-bis(4-(di(1H-pyrrol-2-yl)methyl)phenyl)
aniline (8)
The dipyrromethane 8 was synthesised by a similar proce-
dure for preparing dipyrromethane 3 using dialdehyde 7 as
reactant. The desired product 8 was obtained as a pale brown
solid (yield 88 %). dH (400 MHz, DMSO) 7.95 (s, 4H), 7.31 (d,
J 8.1, 2H), 7.09 (d, J 7.5, 4H), 6.99 (d, J 7.5, 4H), 6.93 (d, J 7.9,
2H), 6.71 (s, 4H), 6.16 (s, 4H), 5.92 (s, 4H), 5.42 (s, 2H). dC
(101 MHz, CDCl3) 146.80, 146.02, 136.98, 132.59, 132.22,
129.34, 125.11, 124.37, 117.36, 114.90, 108.46, 107.24, 43.41.
BDP7
To a solution of BDP5 (200 mg, 0.39 mmol) and tributyl(5-
octylthiophen-2-yl)stannane (9) (200 mg, 0.41 mmol) in toluene
(20 mL) was added Pd(PPh3)4 (116 mg, 0.10 mmol). The mix-
ture was stirred at 908C for 15 h under an Ar atmosphere. The
reaction mixture was then cooled to room temperature, poured
into water (40 mL), and extracted with CH2Cl2 (20 mL ꢁ 2). The
organic layer was dried over anhydrous sodium sulfate and
concentrated under vacuum. The resultant residue was purified
by silica gel column chromatography (petroleum ether/ethyl
acetate, 15 : 1) to give the desired BDP7 as a purple solid
(186 mg, yield 76 %). Mp 93–958C. dH (400 MHz, CDCl3)
7.90 (s, 2H), 7.52 (d, J 8.5, 2H), 7.47 (d, J 8.7, 2H), 7.36 (t, J
7.8, 2H), 7.23 (d, J 7.6, 2H), 7.20–7.16 (m, 3H), 7.14 (d, J 8.7,
2H), 7.09 (d, J 3.5, 1H), 7.06 (d, J 3.8, 2H), 6.74 (d, J 3.4, 1H),
6.55 (d, J 2.3, 2H), 2.82 (t, J 7.5, 2H), 1.76–1.63 (m, 2H), 1.43–
1.21 (m, 10H), 0.88 (t, J 5.9, 3H). dC (101 MHz, CDCl3) 150.73,
146.33, 145.77, 145.26, 142.87, 140.92, 134.65, 132.38, 131.22,
131.09, 129.80, 129.75, 126.66, 126.50, 126.01, 125.93, 125.14,
124.89, 122.55, 120.38, 120.06, 118.07, 33.78, 31.90, 30.31,
29.27, 27.88, 26.88, 22.70, 14.15. m/z (MALDI-TOF-MS)
582.460 [M – 47]þ. Calc. for C39H38BF2N3S: 629.282. HRMS
m/z 610.2880 ([M ꢀ F]þ); calc. for C39H38BF2N3S 610.2864
([M ꢀ F]þ).
BDP4
The dipyrromethane 3 (750 mg, crude) was dissolved in
CH2Cl2 (50 mL), and to the solution was added TCQ (492 mg,
2 mmol) at room temperature. After stirring for 8 h, BF3-Et2O
(4 mL, 30 mmol) and Et3N (4 mL, 28 mmol) were added in that
order under a nitrogen flow and the reaction was allowed to
proceed at room temperature for 3 h. The reaction mixture was
then diluted with ethyl ether and repeatedly washed with water.
The organic layer was dried over anhydrous sodium sulfate,
concentrated under vacuum, and the residue was purified by
silica gel column chromatography (petroleum ether/CH2Cl2,
1 : 1) to give the final product as a purple solid with a metallic
luster (442 mg, yield 50 %). Mp 223–2248C. dH (400 MHz,
CDCl3 TMS) 7.90 (s, 2H), 7.45–7.47 (d, J 8.4, 2H), 7.06–7.36
(m, 14H), 6.55 (s, 2H). dC (100 MHz, CDCl3, TMS) 148.67,
147.73, 144.61, 135.62, 134.76, 133.67, 132.30, 130.36, 129.80,
128.47, 127.44, 127.28, 126.90, 122.76, 119.06, 117.25. m/z
(MALDI-TOF-MS) 435.329. Calc. for C27H20BF2N3: 435.040.
BDP8
The BDP8 was prepared according to a similar procedure for
preparing BDP7 using BDP6 as reactant. The desired product
BDP8 was obtained as a purple solid (yield 81 %). Mp
120–1228C. dH (400 MHz, CDCl3) 7.94 (s, 4H), 7.61 (d, J 8.5,
2H), 7.56 (d, J 8.6, 4H), 7.31 (d, J 8.6, 4H), 7.26 (d, J 6.9, 2H),
7.14 (d, J 3.5, 1H), 7.07 (d, J 4.0, 4H), 6.77 (d, J 3.4, 1H), 6.58 (d,
J 4.0, 4H), 2.84 (t, J 7.6, 2H), 1.75–1.69 (m, 2H), 1.45–1.22 (m,
10H), 0.87 (t, J 3.6, 3H). dC (101 MHz, CDCl3) 149.45, 146.82,
144.48, 143.52, 140.49, 134.71, 132.47, 132.32, 131.15, 128.49,
127.00, 126.94, 125.54, 125.20, 122.95, 122.67, 118.32, 33.52,
31.84, 30.27, 29.32, 28.74, 27.12, 22.63, 14.06. m/z (MALDI-
TOF-MS) 800.536 [M ꢀ F]þ. Calc. for C48H43B2F4N5S:
819.282. HRMS m/z 800.3406 ([M ꢀ F]þ); calc. for
C48H43B2F4N5S 800.3377 ([M ꢀ F]þ).
BDP5
The synthesis procedure of BDP5 was similar to BDP4. The
desired BDP5 was obtained as a purple solid with a metallic
luster with 58 % yield. Mp 208–2108C. dH (400 MHz, CDCl3)
7.91 (s, 2H), 7.47 (d, J 7.7, 2H), 7.45 (d, J 7.8, 2H), 7.36 (d, J
7.6, 2H), 7.21–7.19 (m, 3H), 7.11 (d, J 8.8, 2H), 7.09 (d, J 9.0,
2H), 7.05 (s, 2H), 6.56 (s, 2H). dC (101 MHz, CDCl3) 150.42,
146.16, 145.72, 143.08, 134.65, 133.42, 132.76, 132.34,
131.15, 129.90, 127.05, 126.85, 126.00, 125.09, 120.60,
118.16, 117.22. m/z (MALDI-TOF-MS) 494.159 ([M ꢀ F]þ).
Calc. for C27H19BBrF2N3: 513.081. HRMS m/z 494.0854
([M ꢀ F]þ); calc. for C27H19BBrF2N3 494.0839 ([M ꢀ F]þ).
BDP6
To a solution of 8 (306 mg, 0.5 mmol) in CH2Cl2 (50 mL)
was added TCQ (246 mg, 1 mmol) at room temperature. After
stirring for 8 h, BF3-Et2O (3 mL, 22 mmol) and Et3N (3 mL,
21 mmol) were added in that order under a nitrogen flow and the
reaction was allowed to proceed at room temperature for 3 h.
The reaction mixture was then diluted with ethyl ether and
repeatedly washed with water. The organic layer was dried over
anhydrous sodium sulfate. The crude product was then concen-
trated under vacuum and purified by silica gel column chroma-
tography (petroleum ether/CH2Cl2, 2 : 1). The red coloured
fraction was collected and the solvent was removed under
reduced pressure to give the final product as a purple solid
with a metallic luster (265 mg, yield 75 %). Mp 276–2788C.
Supplementary Material
1H and 13C NMR spectra and mass spectra for all unknown
compounds are available on the Journal’s website.
Acknowledgements
This work was supported by the Natural Science Foundation of Guangdong
Province (2014A030313630), the National Nature Science Foundation of
China (51476036, 21342003), Project for High-level Personnel of Univer-
sity in Guangdong Province ([2013]246), the University Science and
Technology Innovation Key Project of Guangdong Province (cxzd1148),
and the University and Scientific Research Institution Key Project of
Dongguan City (2012108101005).

BODIPY-Tethered Triphenylamine Conjugates
G
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