Synthesis and second-order nonlinear optical properties of push-pull BODIPY derivatives

Article abstract of DOI:10.1016/j.tet.2012.08.033

A series of boron dipyrromethene derivatives bearing an electron-donating 4-(dimethylamino)phenylethynyl group and an electron-withdrawing 4-nitrophenylethynyl group in the opposite 2- and 6-positions have been synthesized by Knoevenagel condensation followed by sequential Sonogashira coupling reactions. The compounds have been fully characterized with various spectroscopic methods. Their electrochemical properties have also been studied by cyclic voltammetry in CH₂Cl₂. It has been found that expansion of the π systems by introduction of the 4-dodecyloxystyryl or 4-(dimethylamino)phenylethynyl group results in lowering of the first oxidation potential, while the first reduction potential remains relatively unaffected. The second-order nonlinear optical properties of these compounds have also been studied by electric-field-induced second-harmonic generation method in CHCl ₃. The values of the dot product μ·β are in the range from 94×10^-48 to 330×10^-48 esu at 1907 nm, depending the substituents at the 3- and 5-positions.

Full text of DOI:10.1016/j.tet.2012.08.033

Tetrahedron 68 (2012) 8712e8718
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis and second-order nonlinear optical properties of push-pull BODIPY
derivatives
,
Wen-Jing Shi a, Pui-Chi Lo a, Anu Singh b, Isabelle Ledoux-Rak b, Dennis K.P. Ng a
*
a Department of Chemistry and Center of Novel Functional Molecules, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, China
Laboratoire de Photonique Quantique et Moleculaire UMR CNRS 8537, Institut d’Alembert, ENS Cachan, 61 Aveneue du President Wilson, 94235 Cachan, France
b
ꢀ
ꢀ
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 June 2012
Received in revised form 29 July 2012
Accepted 10 August 2012
Available online 16 August 2012
A series of boron dipyrromethene derivatives bearing an electron-donating 4-(dimethylamino)phenyl-
ethynyl group and an electron-withdrawing 4-nitrophenylethynyl group in the opposite 2- and 6-
positions have been synthesized by Knoevenagel condensation followed by sequential Sonogashira
coupling reactions. The compounds have been fully characterized with various spectroscopic methods.
Their electrochemical properties have also been studied by cyclic voltammetry in CH2Cl2. It has been
found that expansion of the
p systems by introduction of the 4-dodecyloxystyryl or 4-(dimethylamino)
Keywords:
phenylethynyl group results in lowering of the first oxidation potential, while the first reduction po-
tential remains relatively unaffected. The second-order nonlinear optical properties of these compounds
have also been studied by electric-field-induced second-harmonic generation method in CHCl3. The
Boron dipyrromethene
Pushepull chromophores
Donoreacceptor systems
Nonlinear optics
values of the dot product
m
$
b
are in the range from 94ꢀ10ꢁ48 to 330ꢀ10ꢁ48 esu at 1907 nm, depending
the substituents at the 3- and 5-positions.
Cross-coupling
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
pushepull systems as second-order NLO materials. Boron dipyr-
romethene (BODIPY) derivatives, which can be regarded as half-
porphyrins, represent another versatile class of functional dyes.11
As part of our continued interest in these compounds as sensors
for metal ions,12 photosensitizers for photodynamic therapy,13 and
components for artificial photosynthetic models,14 we believed that
these compounds, by having strong electron-donor and -acceptor
groups at the opposite 2- and 6-positions, can also serve as second-
Since the optical second-harmonic generation was first ob-
served in the early 1960s, nonlinear optics has become a vibrant
field of research.1 The development was particularly rapid in the
late 1970s when various tools were developed to accurately mea-
sure and calculate hyperpolarizabilities, and a better understanding
was achieved on the origin of nonlinear optical (NLO) phenomena
and the structureeproperty relationships of NLO chromophores.2
Organic NLO materials, which can be modulated and processed
readily, are of much contemporary interest because of their po-
tential applications in modulation of optical signals, micro-
fabrication and imaging, laser technology, data storage, telecom-
munication, etc.2,3 To achieve second-order NLO effects, the chro-
order NLO materials. The
p-skeleton can be further modulated by
introducing the substituents at the 3- and 5-positions. To our
knowledge, only a few pushepull BODIPY derivatives have been
reported, focusing on their spectroscopic and electrochemical
properties, but their second-order NLO response has not been
studied so far.15 We report herein the preparation of a series of
BODIPY derivatives bearing an electron-donating 4-(dimethyla-
mino)phenylethynyl group and an electron-withdrawing 4-
nitrophenylethynyl group in the opposite 2- and 6-positions. The
second-order NLO properties of these pushepull BODIPY de-
rivatives are also reported for the first time.
mophores generally contain a conjugated
p system with strong
electron-donor and -acceptor groups preferably at the opposite
ends, thereby creating a large dipole in the molecule.4 Octupolar
molecules are a well-known exception, which exhibit nonzero
molecular first hyperpolarizabilities (b
) despite being nonpolar.5
Solid thin films with highly ordered molecular assemblies can
also exhibit enhanced NLO susceptibility.6 A number of conjugated
frameworks, such as merocyanines,7 porphyrins,8 phthalocya-
nines,9 and graphenes10 have been employed to construct
2. Results and discussion
The preparation of these compounds is shown in Scheme 1.
Knoevenagel condensation of BODIPY 116 with 1 equiv of benzal-
dehyde 217 gave the monostyryl BODIPY 3 in 27% yield, while the
use of 4 equiv of 2 led to the isolation of the distyryl BODIPY 4 in
* Corresponding author. E-mail address: dkpn@cuhk.edu.hk (D.K.P. Ng).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2012.08.033

W.-J. Shi et al. / Tetrahedron 68 (2012) 8712e8718
8713
Scheme 1. Synthesis of pushepull BODIPY derivatives 11e14.
49% yield. These compounds could be purified readily by column
chromatography followed by size exclusion chromatography with
Bio-Beads S-X1 beads. The dodecyl chains were introduced to en-
hance the solubility of these compounds. Without these chains,
purification of the subsequent products was found to be difficult.
Compounds 1, 3, and 4 then underwent palladium-catalyzed
Sonogashira cross-coupling reaction with 4-(dimethylamino)-
phenylethyne (5) using diisopropylethylamine (DIEA) as the base to
give the corresponding BODIPY derivatives. As expected, treatment
of the unsymmetrical BODIPY 3 with 5 gave two products (7 and 8),
which fortunately could be separated by column chromatography.
The two compounds could be distinguished by comparing their 1H
NMR spectra. As shown in Fig. 1, the two doublets for the vinylic
protons (labeled as a and b) of 7 are significantly downfield-shifted
compared with those for 8, which are almost identical with those of
the parent compound 3. The downfield shift could be attributed to
the deshielding effect by the neighboring alkynyl group. A further
cross-coupling reaction of 6e9 with 4-nitrophenylethyne (10)
afforded the respective pushepull BODIPY derivatives 11e14 in
good yield. In contrast to the first coupling reactions, which
Fig. 1. 1H NMR spectra of 3, 7, and 8 in CDCl3.

8714
W.-J. Shi et al. / Tetrahedron 68 (2012) 8712e8718
proceeded smoothly at room temperature, the second coupling
reactions required a refluxing condition, which is probably due to
the lower reactivity of alkyne 10 compared with 5. All the new
compounds were characterized with various spectroscopic
methods.
The electronic absorption and fluorescence data of all these
compounds were measured in CH2Cl2 and are compiled in Table 1.
Fig. 2a shows the absorption spectra of the pushepull BODIPY
derivatives 11e14. Compound 11 exhibited a broad Q band at
574 nm, which was significantly red-shifted compared with that of
6 (555 nm) and 1 (533 nm) (Figs. S1 and S2 in Supplementary data),
0.20
0.15
0.10
0.05
(a)
11
12
13
14
showing the effect of stepwise expansion of the
p system. The
monostyryl and distyryl BODIPY derivatives also followed the same
trend. For the monostyryl analogues 7 and 8, their Q bands
appeared at the same position (619 nm). However, after the in-
troduction of the 4-nitrophenylethynyl group, the Q band of 12 was
0.00
300
400
500
600
700
800
more intense and red-shifted than that of 13 [638 nm (log
vs 626 nm (log
¼4.84)]. This observation indicated that in-
troduction of this strong electron-acceptor on the opposite side of
the styryl group exerts larger perturbation to the system. This can
3
¼4.90)
3
Wavelength (nm)
p
(b)
1.0
0.8
0.6
0.4
0.2
0.0
be rationalized by examining the structure of 12, which contains
the electron-donating 4-(dimethylamino)phenylethynyl and 4-
dodecyloxystyryl groups on one side and the electron-
withdrawing 4-nitrophenylethynyl group on the other side,
thereby imparting a greater intramolecular charge-transfer char-
acter to 12. Fig. 2b shows the steady-state fluorescence spectra of
11e14 in CH2Cl2. The emission position followed the trend of the Q-
band position: 14 (699 nm)>12 (640 nm)y13 (633 nm)>11
(587 nm), and the fluorescence quantum yield (FF) generally de-
creased upon conjugation with the alkynyl moieties (Table 1). In
addition, the mono-alkynyl compounds 7e9 and dialkynyl ana-
logues 12e14 showed a relatively small Stokes shift (2e7 nm)
11
12
13
14
550
600
650
700
750
800
compared with the other less
as shown in Table 1.
p-expanded derivatives (12e19 nm)
Wavelength (nm)
Table 1
Fig. 2. (a) Electronic absorption (all in 2
of 11e14 in CH2Cl2.
mM) and (b) normalized fluorescence spectra
Absorption and fluorescence data for the BODIPY derivatives in CH2Cl2
Comp.
lmax/nm (log
3 )
lem/nm
Stokes shift/nm
FF
Table 2
1
3
4
6
385 (4.00), 533 (4.89)
347 (4.38), 597 (4.96)
380 (4.52), 663 (4.82)
309 (4.48), 382 (4.09),
455 (4.08), 555 (4.64)
373 (4.53), 333 (4.52),
500 (3.96), 619 (4.78)
315 (4.55), 497 (4.09),
619 (4.76)
393 (4.64), 687 (4.85)
310 (4.58), 397 (4.31),
468 (4.13), 574 (4.76)
374 (4.59), 512 (4.03),
638 (4.90)
548
614
682
567
15
17
19
12
0.08a
1b
Electrochemical data for the BODIPY derivativesa
0.20c
0.04a
Compound
Eox/V
Ered/V
1
3
4
6
7
8
9
11
12
13
14
þ1.25b
þ0.98b
þ0.87b
þ0.80c
þ0.77c
þ0.73c
þ0.73c
þ0.79c
þ0.77c
þ0.72c
þ0.72c
ꢁ1.10b
ꢁ1.05b
7
8
624
623
5
4
0.02b
0.01b
ꢁ0.91b
ꢁ1.15b
ꢁ1.05b
ꢁ1.04b
9
11
689
587
2
13
0.006c
0.03a
ꢁ0.94b
ꢁ1.16b
ꢁ1.01,b ꢁ1.18b
ꢁ1.00,b ꢁ1.14b
ꢁ0.95,b ꢁ1.16b
12
13
14
640
633
699
2
7
3
0.007b
0.04b
333 (4.59), 333 (4.59),
501 (4.10), 626 (4.84)
329 (4.55), 388 (4.68),
696 (4.98)
a
Recorded with [Bu4N][PF6] as the electrolyte in CH2Cl2 (0.1 M) at ambient
temperature with a scan rate of 50 mV sꢁ1. Potentials are expressed as the half-wave
potentials (E1/2) (for quasi-reversible couples) or the cathodic or anodic potentials
(Epc or Epa) (for irreversible processes) in volts vs SCE using ferrocene as an internal
reference [E1/2 (Fc/Fcþ)¼þ0.38 V vs SCE].
0.005c
a
With reference to rhodamine B in ethanol (FF¼0.49).18
b
Due to the very different emission positions of these compounds, it was difficult
b
Quasi-reversible.
Irreversible.
to find an appropriate reference. Hence, the relative fluorescence intensities are
c
reported.
c
With reference to zinc(II) phthalocyanine in DMF (FF¼0.28).19
and significant decrease in the potential to þ0.98 V (for 3) and
þ0.87 V (for 4). Introduction of the electron-donating 4-(dime-
thylamino)phenylethynyl group (in compounds 6e9) greatly re-
duced the first oxidation potential of these compounds to
þ(0.73e0.80) V, while the first reduction potential was not signif-
icantly affected. However, a further introduction of the electron-
withdrawing 4-nitrophenylethynyl group (in compounds 11e14)
did not exert a significant influence on both processes. Fig. 3, which
The electrochemical properties of these compounds were also
studied by cyclic voltammetry in CH2Cl2 and the data are compiled
in Table 2. BODIPY 1 showed a quasi-reversible oxidation and
a quasi-reversible reduction at þ1.25 V and ꢁ1.10 V, respectively,
relative to the saturated calomel electrode (SCE). Introduction of
the 4-dodecyloxystyryl group (in compounds 3 and 4) facilitated
both processes, particularly the oxidation as shown by the gradual

W.-J. Shi et al. / Tetrahedron 68 (2012) 8712e8718
8715
Fc/Fc+
yield generally decreases upon conjugation with the alkynyl moi-
eties. Electrochemical studies have shown that introduction of the
electron-donating 4-dodecyloxystyryl and 4-(dimethylamino)
phenylethynyl groups facilitates the first oxidation of these com-
pounds, but their first reduction is not significantly affected. These
6
4
1
6
11
2
compounds exhibit moderate
m
$b
values [(94e330)ꢀ10ꢁ48 esu] as
determined by EFISH at 1907 nm, which can be modulated by the
peripheral substituents. Generally, by putting the electron-
donating and electron-withdrawing groups on the opposite side
of BODIPY core, this can promote the charge-transfer character of
these compounds and enhance their second-order NLO properties.
This structureeproperty relationship would be useful in further
studies of BODIPY-based NLO materials.
0
-2
-4
-6
-8
4. Experimental
4.1. General
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
Potential (V)
Fig. 3. Cyclic voltammograms of 1, 6, and 11 in CH2Cl2 containing 0.1 M [Bu4N][PF6]
All the reactions were performed under an atmosphere of ni-
trogen. Tetrahydrofuran (THF), toluene, and CH2Cl2 were distilled
from sodium benzophenone ketyl, sodium, and calcium hydride,
respectively. Chromatographic purifications were performed on
silica gel (Macherey-Nagel 230e400 mesh) columns with the in-
dicated eluents. Size exclusion chromatography was carried out on
Bio-Beads S-X1 beads (200e400 mesh) with THF as the eluent. All
other solvents and reagents were of reagent grade and used as
received. Compounds 116 and 217 were prepared as described.
1H and 13C{1H} NMR spectra were recorded on a Bruker AVANCE
III 400 spectrometer (1H, 400; 13C, 100.6 MHz) in CDCl3. Spectra
with a scan rate of 50 mV sꢁ1. Ferrocene (Fc) was added as an internal reference.
shows the voltammograms of 1, 6, and 11, is given as an example to
illustrate the effects of these substituents.
The second-order NLO properties of the pushepull BODIPY
derivatives 11e14 were measured by EFISH in CHCl3 at 1907 nm
and their dipole moments (
empirical code included in the MOPAC2009 package.20 The values
of the dot product and mcalcd, as well as derived from these
data are listed in Table 3. Disperse Red 1, a common benchmark for
m) were calculated using the PM3 semi-
m
$b
b
were referenced internally using the residual solvent (1H:
solvent (13C:
77.2) resonances relative to SiMe4. Electrospray
d 7.26) or
NLO chromophores,21 was used as the reference, which has a
m$b
d
value of 363ꢀ10ꢁ48 esu under the same experimental conditions.
ionization (ESI) mass spectra were recorded on a Thermo Finnigan
MAT 95 XL mass spectrometer. Elemental analyses were performed
by the Shanghai Institute of Organic Chemistry, Chinese Academy of
Sciences, China. UVevis and steady-state fluorescence spectra were
taken on a Cary 5G UVevis-NIR spectrophotometer and a Hitachi F-
4500 spectrofluorometer, respectively. The fluorescence quantum
The
b values were not corrected for resonance enhancement be-
cause the second-harmonic signal (954 nm) lies far from the elec-
tronic absorptions. Related pushepull porphyrins have been
reported,22 but a direct comparison of the
b values is difficult be-
cause of different experimental conditions. Qualitatively, these
BODIPY derivatives have lower hyperpolarizabilities. The values
depend on the nature and position of the substituents at the 3- and
5-positions. Compound 12, which has the electron-donating 4-
(dimethylamino)phenylethynyl and 4-dodecyloxystyryl groups on
yields of the samples [FF(sample)] were determined by the equation:
23
FFðsampleÞ ¼ ðFsample=Fref ÞðAref =AsampleÞðn2sample=nr2ef
Þ ,
FFðrefÞ
where F, A, and n are the measured fluorescence (area under the
emission peak), the absorbance at the excitation position, and the
refractive index of the solvent, respectively. Rhodamine B in etha-
nol was used as the reference [FF(ref)¼0.49] for compounds 1, 6, and
11.18 The unsubstituted zinc(II) phthalocyanine in DMF was used as
the reference [FF(ref)¼0.28] for compounds 4, 9, and 14.19
the same side, shows the largest
expected, its calculated dipole moment is also the largest (10.9 D).
m
$
b
value (330ꢀ10ꢁ48 esu). As
By contrast, compound 13, in which these two substituents are on
the opposite side, exhibits the smallest
m$b and b values. These
observations suggest that charge transfer is an important factor for
the second-order NLO properties, which is governed by the position
of these substituents.
Electrochemical measurements were carried out on a BAS CV-
50W voltammetric analyzer. The cell comprised inlets for a plati-
num-sphere working electrode, a platinum-wire counter elec-
trode, and
a
silver-wire pseudo-reference electrode. All
Table 3
measurements were carried out in deoxygenated CH2Cl2 with 0.1 M
[Bu4N][PF6] as the supporting electrolyte with a scan rate of
50 mV sꢁ1. Ferrocene was added as an internal standard, of which
the E1/2 value was set as þ0.38 V vs SCE.
Dipole moments and hyperpolarizabilities of 11e14
Comp.
11
12
10.9
330
30
13
7.8
94
12
14
10.3
308
30
a
mcalcd (D)
9.2
m
$
b
b (ꢀ10ꢁ48 esu)
233
25
b
c (ꢀ10ꢁ30 esu)
4.2. Monostyryl BODIPY 3
a
b
c
Calculated by the MOPAC2009 package.
With reference to Disperse Red 1 (
Calculated by dividing with mcalcd.
m
$b
¼363ꢀ10ꢁ48 esu).
A
mixture of dodecyloxy substituted BODIPY 1 (200 mg,
m$
b
0.26 mmol), benzaldehyde 2 (76.4 mg, 0.26 mmol), piperidine
(1.2 mL), acetic acid (1.0 mL), and a small amount of Mg(ClO4)2 in
toluene (50 mL) was refluxed for 50 min. The water formed during
the reaction was removed azeotropically with a DeaneStark ap-
paratus. The volatiles were removed under reduced pressure. The
residue was purified by column chromatography using CH2Cl2/
hexane (1:1, v/v) as the eluent followed by size exclusion chro-
matography with THF as the eluent. The desired product 3 was
3. Conclusion
In summary, a series of novel pushepull BODIPY derivatives
have been synthesized by Knoevenagel condensation followed by
sequential Sonogashira coupling reactions. Expansion of the
system by these two reactions results in significant red-shift of the
absorption and fluorescence bands. The fluorescence quantum
p
obtained as a brown solid (73.2 mg, 27%). 1H NMR:
d 8.12 (d,

8716
W.-J. Shi et al. / Tetrahedron 68 (2012) 8712e8718
J¼16.8 Hz, 1H, CH]CH), 7.57 (d, J¼8.4 Hz, 2H, ArH), 7.53 (d,
J¼16.8 Hz, 1H, CH]CH), 7.13 (d, J¼8.4 Hz, 2H, ArH), 7.02 (d,
J¼8.4 Hz, 2H, ArH), 6.91 (d, J¼8.4 Hz, 2H, ArH), 3.98e4.04 (m, 4H,
CH2), 2.68 (s, 3H, CH3), 1.76e1.86 (m, 4H, CH2), 1.50 (s, 3H, CH3), 1.46
(s, 3H, CH3), 1.46e1.50 (m, 4H, CH2), 1.28 (br s, 32H, CH2), 0.87e0.90
7.37 (d, J¼8.8 Hz, 2H, ArH), 7.15 (d, J¼8.8 Hz, 2H, ArH), 7.01 (d,
J¼8.8 Hz, 2H, ArH), 6.90 (d, J¼8.4 Hz, 2H, ArH), 6.67 (d, J¼8.8 Hz, 2H,
ArH), 3.98e4.04 (m, 4H, CH2), 3.00 (s, 6H, CH3), 2.69 (s, 3H, CH3),
1.76e1.87 (m, 4H, CH2), 1.60 (s, 3H, CH3), 1.42e1.54 (m, 7H, CH2 and
CH3), 1.28 (br s, 32H, CH2), 0.87e0.91 (m, 6H, CH3). 13C{1H} NMR:
(m, 6H, CH3). 13C{1H} NMR:
d
160.5, 160.3, 156.5, 150.7, 146.4, 145.0,
d 160.5, 160.1, 154.8, 153.3, 150.3, 145.6, 143.3, 140.2, 139.6, 132.5,
140.4, 139.2, 132.8, 132.4, 129.4, 129.3, 126.9, 116.6, 115.5, 115.0, 86.0,
82.3, 68.4, 68.3, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.9, 17.8, 17.3,
16.3, 14.3 (some of the signals are overlapped). MS (ESI): m/z 1032
(100%, [M]þ). HRMS (ESI): m/z calcd for C50H69BF2I2N2O2 [M]þ:
1032.3512, found 1032.3511. Anal. Calcd for C50H69BF2I2N2O2: C,
58.15; H, 6.73; N, 2.71. Found: C, 58.13; H, 6.73; N, 2.27.
132.3, 129.7, 129.5, 129.4, 126.9, 116.7, 115.3, 115.0, 112.1, 110.3, 99.7,
85.0, 81.7, 68.4, 68.3, 40.4, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.8,
17.1, 16.1, 14.3, 13.7 (some of the signals are overlapped). MS (ESI):
m/z 1051 (100%, [MþH]þ). HRMS (ESI): m/z calcd for
C60H80BF2IN3O2 [MþH]þ: 1050.5351, found 1050.5351. Anal. Calcd
for C60H79BF2IN3O2: C, 68.63; H, 7.58; N, 4.00. Found: C, 68.57; H,
7.81; N, 3.72. Compound 8: 1H NMR:
d
8.08 (d, J¼16.4 Hz, 1H, CH]
4.3. Distyryl BODIPY 4
CH), 7.58 (d, J¼8.8 Hz, 2H ArH), 7.54 (d, J¼16.4 Hz,1H, CH]CH), 7.34
(d, J¼8.8 Hz, 2H, ArH), 7.15 (d, J¼8.4 Hz, 2H, ArH), 7.02 (d, J¼8.4 Hz,
2H, ArH), 6.91 (d, J¼8.8 Hz, 2H, ArH), 6.63 (d, J¼8.8 Hz, 2H, ArH),
3.98e4.04 (m, 4H, CH2), 2.98 (s, 6H, CH3), 2.74 (s, 3H, CH3),
1.76e1.87 (m, 4H, CH2), 1.56 (s, 3H, CH3), 1.51 (s, 3H, CH3), 1.42e1.49
(m, 4H, CH2), 1.28 (br s, 32H, CH2), 0.87e0.91 (m, 6H, CH3). 13C{1H}
According to the above procedure, BODIPY
1 (100 mg,
0.13 mmol) was treated with benzaldehyde 2 (153 mg, 0.53 mmol),
piperidine (1.2 mL), acetic acid (1.0 mL), and a small amount of
Mg(ClO4)2 in refluxing toluene (40 mL) for 1.5 h to give 4, which
was purified by column chromatography with CH2Cl2/hexane (2:3,
v/v) as the eluent followed by size exclusion chromatography with
NMR:
d 160.3, 160.1, 159.2, 150.2, 150.1, 149.8, 145.0, 143.7, 140.6,
138.3, 133.1, 132.6, 132.1, 129.6, 129.5, 129.2, 126.9, 117.9, 116.7, 115.4,
114.9, 112.1, 112.0, 110.4. 110.3, 98.1, 81.6, 79.5, 79.4, 68.4, 68.3, 40.4,
32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.9, 17.6, 14.3, 14.1, 13.9 (some
of the signals are overlapped). MS (ESI): m/z 1051 (100%, [MþH]þ).
HRMS (ESI): m/z calcd for C60H80BF2IN3O2 [MþH]þ: 1050.5351,
found 1050.5362. Anal. Calcd for C60H79BF2IN3O2: C, 68.63; H, 7.58;
N, 4.00. Found: C, 67.85; H, 7.60; N, 3.99.
THF as the eluent (83.7 mg, 49%). 1H NMR:
d
8.13 (d, J¼16.8 Hz, 2H,
CH]CH), 7.60 (d, J¼8.8 Hz, 4H, ArH), 7.59 (d, J¼16.8 Hz, 2H, CH]
CH), 7.15 (d, J¼8.8 Hz, 2H, ArH), 7.03 (d, J¼8.8 Hz, 2H, ArH), 6.94 (d,
J¼8.8 Hz, 4H, ArH), 3.99e4.05 (m, 6H, CH2), 1.77e1.86 (m, 6H, CH2),
1.55 (s, 3H, CH3), 1.51 (s, 3H, CH3), 1.42e1.51 (m, 6H, CH2), 1.28 (br s,
48H, CH2), 0.87e0.90 (m, 9H, CH3). 13C{1H} NMR:
d 160.5 160.3,
150.5, 145.8, 139.2, 138.8, 133.4, 129.7, 129.6, 129.4, 127.2, 116.8,
115.5, 115.0, 82.7, 68.4, 68.3, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2,
22.9, 17.9, 14.3 (some of the signals are overlapped). MS (ESI): m/z
1305 (100%, [M]þ). HRMS (ESI): m/z calcd for C69H97BF2I2N2O3
[M]þ: 1304.5644, found 1304.5642.
4.6. Distyryl BODIPY 9
According to the procedure described for 6, distyryl BODIPY 4
(201 mg, 0.15 mmol) was treated with PdCl2(PPh3)2 (5.2 mg,
7.4 mmol), CuI (3.0 mg, 15.8 mmol), alkyne 5 (33.4 mg, 0.23 mmol),
4.4. BODIPY 6
and DIEA (4 mL) in THF (10 mL) at room temperature for 12 h to
give 9, which was purified by column chromatography using
CH2Cl2/hexane (1:1 to 3:1, v/v) as the eluent (87.3 mg, 43%). 1H
A mixture of BODIPY 1 (301 mg, 0.40 mmol), PdCl2(PPh3)2
(14.4 mg, 20.5
m
mol), CuI (7.6 mg, 40
m
mol), 4-(dimethylamino)
NMR:
d
8.53 (d, J¼16.4 Hz, 1H, CH]CH), 8.09 (d, J¼16.4 Hz, 1H,
phenylethyne (5) (63.4 mg, 0.44 mmol), and DIEA (5 mL) in THF
(10 mL) was stirred at room temperature for 12 h. The volatiles were
removed in vacuo, then the dark purple residue was subjected to
column chromatography using CH2Cl2/hexane (1:1 to 3:2, v/v) as the
eluent. The product was collected as a dark purple solid (102 mg,
CH]CH), 7.71 (d, J¼16.4 Hz, 1H, CH]CH), 7.58e7.63 (m, 5H, ArH
and CH]CH), 7.37 (d, J¼8.8 Hz, 2H, ArH), 7.17 (d, J¼8.4 Hz, 2H, ArH),
7.02 (d, J¼8.8 Hz, 2H, ArH), 6.95 (d, J¼8.8 Hz, 2H, ArH), 6.92 (d,
J¼8.4 Hz, 2H, ArH), 6.67 (d, J¼8.8 Hz, 2H, ArH), 3.99e4.04 (m, 6H,
CH2), 3.00 (s, 6H, CH3), 1.77e1.88 (m, 6H, CH2), 1.60 (s, 3H, CH3), 1.51
(s, 3H, CH3), 1.42e1.50 (m, 6H, CH2), 1.28 (br s, 48H, CH2), 0.87e0.90
33%). 1H NMR:
d
7.33 (d, J¼8.8 Hz, 2H, ArH), 7.13 (d, J¼8.8 Hz, 2H,
ArH), 7.02 (d, J¼8.8 Hz, 2H, ArH), 6.63 (d, J¼8.8 Hz, 2H, ArH), 4.02 (t,
J¼6.8 Hz, 2H, CH2), 2.98 (s, 6H, CH3), 2.70 (s, 3H, CH3), 2.64 (s, 3H,
CH3), 1.84 (quintet, J¼6.8 Hz, 2H, CH2), 1.56 (s, 3H, CH3), 1.44e1.54
(m, 2H, CH2),1.46 (s, 3H, CH3),1.28 (br s,16H, CH2), 0.87e0.90 (m, 3H,
(m, 9H, CH3). 13C{1H} NMR:
d 160.5, 160.2, 160.1, 153.3, 150.2, 149.2,
145.1, 144.2, 139.7, 138.6, 138.0, 133.5, 133.2, 132.3, 129.8, 129.5,
129.2, 127.2, 117.0, 115.3, 115.0, 114.9, 112.1, 110.4, 99.9, 81.8, 68.4,
68.3, 40.3, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.8, 17.6, 14.3, 13.7
(some of the signals are overlapped). MS (ESI): m/z 1323 (100%,
[MþH]þ). HRMS (ESI): m/z calcd for C79H108BF2IN3O3 [MþH]þ:
1322.7491, found 1322.7496. Anal. Calcd for C79H107BF2IN3O3: C,
71.75; H, 8.16; N, 3.18. Found: C, 71.49; H, 8.12; N, 2.92.
CH3). 13C{1H} NMR:
d 160.2, 159.2, 155.4, 150.2, 144.3, 144.1, 142.0,
132.6, 132.2, 131.5, 129.3 126.6, 117.6, 115.4, 112.0, 110.3, 97.9, 84.8,
79.3, 68.4, 40.4, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.8, 17.1, 16.0,
14.3, 13.9 (some of the signals are overlapped). MS (ESI): m/z 778
(100%, [MþH]þ). HRMS (ESI): m/z calcd for C41H52BF2IN3O [MþH]þ
778.3218, found 778.3224. Anal. Calcd for C41H51BF2IN3O: C, 63.33;
H, 6.61; N, 5.40. Found: C, 63.04; H, 6.67; N, 5.13.
4.7. BODIPY 11
A mixture of compound 6 (50.0 mg, 64.3
mmol), PdCl2(PPh3)2
4.5. Monostyryl BODIPY 7 and 8
(2.3 mg, 3.3 mol), CuI (1.4 mg, 7.4 mol), 4-nitrophenylethyne (10)
m
m
(18.9 mg, 0.13 mmol), and DIEA (2 mL) in THF (4 mL) was refluxed
for 12 h. The volatiles were removed in vacuo, then the dark blue
residue was chromatographed using CH2Cl2/hexane (3:2 to 2:1, v/v)
as the eluent. The product was collected as a dark blue solid
According to the procedure described for 6, monostyryl BODIPY
3 (200 mg, 0.19 mmol) was treated with PdCl2(PPh3)2 (6.8 mg,
9.7 mmol), CuI (3.7 mg, 19.4 mmol), alkyne 5 (28.2 mg, 0.19 mmol),
and DIEA (5 mL) in THF (10 mL) at room temperature for 12 h. The
crude product was purified by column chromatography using
CH2Cl2/hexane (1:1 to 3:2, v/v) as the eluent. The first two blue
bands were collected to give 7 (37.2 mg, 18%) and 8 (45.3 mg, 22%),
(40.4 mg, 79%). 1H NMR:
d
8.18 (d, J¼8.8 Hz, 2H, ArH), 7.55 (d,
J¼8.8 Hz, 2H, ArH), 7.33 (d, J¼8.8 Hz, 2H, ArH), 7.17 (d, J¼8.8 Hz, 2H,
ArH), 7.04 (d, J¼8.8 Hz, 2H, ArH), 6.63 (d, J¼8.8 Hz, 2H, ArH), 4.03 (t,
J¼6.4 Hz, 2H, OCH2), 2.98 (s, 6H, CH3), 2.72 (s, 3H, CH3), 2.71 (s, 3H,
CH3), 1.84 (quintet, J¼6.4 Hz, 2H, CH2), 1.58 (s, 6H, CH3), 1.46e1.54
(m, 2H, CH2), 1.33e1.43 (m, 2H, CH2), 1.28 (br s, 14H, CH2),
respectively. Compound 7: 1H NMR:
CH), 7.65 (d, J¼16.4 Hz, 1H, CH]CH), 7.58 (d, J¼8.4 Hz, 2H, ArH),
d
8.50 (d, J¼16.4 Hz, 1H, CH]

W.-J. Shi et al. / Tetrahedron 68 (2012) 8712e8718
8717
0.87e0.90 (m, 3H, CH3). 13C{1H} NMR:
d
160.3, 160.2, 156.8, 150.3,
ArH), 6.64 (d, J¼8.8 Hz, 2H, ArH), 4.03 (t, J¼6.4 Hz, 4H, CH2), 3.87 (t,
J¼6.4 Hz, 2H, CH2), 2.99 (s, 6H, CH3), 1.78e1.85 (m, 6H, CH2),
1.47e1.52 (m, 12H, CH2 and CH3), 1.29 (br s, 48H, CH2), 0.87e0.91
146.7, 144.6, 143.4, 142.8, 132.6, 131.8, 131.3, 130.8, 129.2, 126.2,
123.8, 118.2, 115.4, 114.1, 111.9, 110.0, 98.4, 94.7, 88.4, 79.1, 68.4, 40.4,
32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.8, 14.3, 13.9, 13.7. MS (ESI):
m/z 797 (100%, [MþH]þ). HRMS (ESI): m/z calcd for C49H56BF2N4O3
[MþH]þ: 797.4416, found 797.4425. Anal. Calcd for C49H55BF2N4O3:
C, 73.86; H, 6.96; N, 7.03. Found: C, 73.55; H, 7.02; N, 6.80.
(m, 9H, CH3). 13C{1H} NMR:
d 160.7, 160.5, 160.0, 153.4, 151.2, 150.2,
146.5, 145.0, 144.4, 139.8, 139.1, 137.9, 133.9, 132.9, 132.3, 131.2,
130.7, 129.8, 129.7, 129.6, 129.2, 126.7, 123.8, 116.8, 115.4, 115.1, 112.0,
111.5, 110.3, 100.2, 96.3, 90.7, 81.7, 68.4, 68.3, 40.3, 32.1, 29.9, 29.8,
29.7, 29.6, 29.5, 29.4, 26.3, 26.2, 22.9, 14.3, 13.6, 13.4. MS (ESI): m/z
1342 (100%, [MþH]þ). HRMS (ESI): m/z calcd for C87H112BF2N4O5
[MþH]þ: 1341.8688, found 1341.8679.
4.8. Monostyryl BODIPY 12
According to the procedure described for 11, monostyryl BODIPY
7 (37.1 mg, 35.3
mmol) was treated with PdCl2(PPh3)2 (1.2 mg,
4.11. NLO measurements
1.7 mol), CuI (0.7 mg, 3.7
m
m
mol), alkyne 10 (15.5 mg, 0.11 mmol),
and DIEA (3 mL) in THF (6 mL) to give 12, which was purified by
The m$b values of 11e14 were measured in CHCl3 by the EFISH
column chromatography using CH2Cl2/hexane (1:2 to 2:1, v/v) as
method. The experimental set up is shown in Fig. S3 in
Supplementary data. The measurements were made by using
a commercial (SAGA from Thales Laser) Q-switched Nd3þ:YAG
the eluent (28.3 mg, 75%). 1H NMR:
d
8.53 (d, J¼16.4 Hz, 1H, CH]
CH), 8.16 (d, J¼8.8 Hz, 2H, ArH), 7.65 (d, J¼16.4 Hz, 1H, CH]CH),
7.59 (d, J¼8.8 Hz, 2H, ArH), 7.53 (d, J¼8.8 Hz, 2H, ArH), 7.36 (d,
J¼8.8 Hz, 2H, ArH), 7.19 (d, J¼8.8 Hz, 2H, ArH), 7.02 (d, J¼8.8 Hz, 2H,
ArH), 6.92 (d, J¼8.8 Hz, 2H, ArH), 6.66 (d, J¼8.8 Hz, 2H, ArH),
3.98e4.03 (m, 4H, CH2), 2.99 (s, 6H, CH3), 2.74 (s, 3H, CH3),
1.77e1.86 (m, 4H, CH2), 1.59 (s, 3H, CH3), 1.56 (s, 3H, CH3), 1.45e1.52
(m, 4H, CH2), 1.28 (br s, 32H, CH2), 0.87e0.91 (m, 6H, CH3). 13C{1H}
nanosecond laser operating at
l
¼1064 nm with a repetition rate of
10 Hz and pulse duration of 9 ns. The 1064 nm laser beam then
entered into the 50 cm long hydrogen Raman cell with a high
pressure (55 atm). The fundamental beam was shifted to
l
¼1910 nm (only the back scattered 1910 nm Raman emission was
collected at a 45ꢂ incidence angle by the use of a dichroic mirror to
eliminate most of the residual 1064 nm pump photons). A Schott
RG 1000 filter was used to filter out the remaining visible light from
the laser flash lamp. Suitable attenuators were used to control the
power of the incident beam. The light was then focused into the
EFISH cell with a lens with a focal length of 20 cm.
NMR:
d 160.7, 160.2, 156.2, 154.1, 150.3, 146.6, 145.8, 142.4, 140.8,
140.3, 133.6, 132.3, 131.7, 130.9, 129.6, 129.5, 126.6, 123.8, 116.5,
115.5, 115.3, 115.0, 114.0, 112.0, 110.2, 100.1, 94.9, 88.8, 81.5, 68.4,
68.3, 40.3, 32.1, 29.8, 29.7, 29.6, 29.5, 29.4, 26.2, 22.8, 14.3, 13.9, 13.7,
13.6 (some of the signals are overlapped). MS (ESI): m/z 1069 (100%,
[M]þ). HRMS (ESI): m/z calcd for C68H83BF2N4O4 [M]þ: 1068.6470,
found 1068.6462. Anal. Calcd for C68H83BF2N4O4: C, 76.39; H, 7.82;
N, 5.24. Found: C, 75.65; H, 7.86; N, 4.94.
The measurements were carried out with a wedge-shaped cell
(with a volume of 4 mL) comprised of two quartz windows, which
were assembled with an appropriate angle on a stainless steel
support. The inter-electrode distance was 2 mm, giving a static
electric field. The whole cell was translated horizontally relative to
the incident beam to produce a periodic second-harmonic gener-
ation signal. In this technique, the molecules in the solutions were
aligned using a high-voltage DC pulse (5 kV with a pulse width of
4.9. Monostyryl BODIPY 13
According to the procedure described for 11, monostyryl BODIPY
8 (45.0 mg, 42.9
mmol) was treated with PdCl2(PPh3)2 (1.5 mg,
2.1 mol), CuI (0.8 mg, 4.2
and DIEA (3 mL) in THF (6 mL) to give 13, which was purified by
m
m
mol), alkyne 10 (18.9 mg, 0.13 mmol),
200
The fundamental radiation (
second-harmonic radiation (2
which was connected to a high-speed boxcar integrator card. The
signals were processed by a home-made computer program to
calculate the interfringe distance and the fringe amplitude. These
m
s and a delay of 1890
m
u
s) synchronized with the laser pulse.
) was removed by filters, while the
reached the photomultiplier,
column chromatography using CH2Cl2/hexane (1:1 to 2:1, v/v) as
u
)
the eluent (37.2 mg, 82%). 1H NMR:
d
8.22 (d, J¼16.4 Hz, 2H, CH]
CH), 8.20 (d, J¼8.8 Hz, 2H, ArH), 7.62 (d, J¼16.4 Hz, 1H, CH]CH),
7.57 (d, J¼8.8 Hz, 2H, ArH), 7.56 (d, J¼8.8 Hz, 2H, ArH), 7.33 (d,
J¼8.8 Hz, 2H, ArH), 7.18 (d, J¼8.4 Hz, 2H, ArH), 7.00 (d, J¼8.4 Hz, 2H,
ArH), 6.93 (d, J¼8.8 Hz, 2H, ArH), 6.63 (d, J¼8.8 Hz, 2H, ArH), 4.01 (t,
J¼6.4 Hz, 4H, CH2), 2.98 (s, 6H, CH3), 2.75 (s, 3H, CH3), 1.77e1.87 (m,
4H, CH2), 1.60 (s, 3H, CH3), 1.56 (s, 3H, CH3), 1.42e1.54 (m, 4H, CH2),
data were then used to calculate the m$b values of the samples.
Acknowledgements
1.28 (br s, 32H, CH2), 0.87e0.90 (m, 6H, CH3). 13C{1H} NMR:
d 160.5,
This work was financially supported by a strategic investments
160.2, 159.8, 152.0, 150.3, 146.8, 145.1, 143.8, 141.2, 138.3, 132.9,
132.6,132.3,131.5,130.8,129.5,129.2,126.5,124.0,118.1,116.5,115.4,
115.1, 112.0, 111.5, 110.1, 98.4, 96.1, 90.4, 79.3, 68.4, 40.4, 32.1, 29.8,
29.6, 29.5, 29.4, 26.2, 22.9, 14.3, 14.1, 13.9, 13.5 (some of the signals
are overlapped). MS (ESI): m/z 1070 (100%, [MþH]þ). HRMS (ESI):
m/z calcd for C68H84BF2N4O4 [MþH]þ, 1069.6559, found 1069.6569.
scheme administered by The Chinese University of Hong Kong.
Supplementary data
Electronic absorption and fluorescence spectra of 1, 3, 4, and 6e9
in CH2Cl2, a schematic diagram showing the set up for EFISH mea-
surements, and 1H and 13C{1H} spectra of all the new compounds.
Supplementary data associated with this article can be found in the
online version, at http://dx.doi.org/10.1016/j.tet.2012.08.033.
4.10. Distyryl BODIPY 14
According to the procedure described for 11, distyryl BODIPY 9
(50.0 mg, 37.8
m
mol) was treated with PdCl2(PPh3)2 (1.3 mg,
mol), alkyne 10 (16.7 mg, 0.11 mmol),
References and notes
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m
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