3, 3,5 and 2,6 Expanded Aza-BODIPYs Via Palladium-Catalyzed Suzuki-Miyaura Cross-Coupling Reactions: Synthesis and Photophysical Properties

Article abstract of DOI:10.1007/s10895-020-02646-4

Novel symmetrical aza-borondipyrromethene (aza-BODIPY) compounds bearing 4-methoxyphenyl, 4-methoxybiphenyl, 2,4-dimethoxybipheny, 4-bromophenyl and N,N-diphenyl-4-biphenylamine groups on the 3, 3,5 and 2,6 positions of aza-BODIPY core were synthesized vi

Full text of DOI:10.1007/s10895-020-02646-4

Journal of Fluorescence
https://doi.org/10.1007/s10895-020-02646-4
ORIGINAL ARTICLE
3
, 3,5 and 2,6 Expanded Aza-BODIPYs Via Palladium-Catalyzed
Suzuki-Miyaura Cross-Coupling Reactions: Synthesis
and Photophysical Properties
1
2
1
Halil Yılmaz
& Gökhan Sevinç
& Mustafa Hayvalı
Received: 9 September 2020 /Accepted: 30 October 2020
Springer Science+Business Media, LLC, part of Springer Nature 2020
#
Abstract
Novel symmetrical aza-borondipyrromethene (aza-BODIPY) compounds bearing 4-methoxyphenyl, 4-methoxybiphenyl, 2,4-
dimethoxybipheny, 4-bromophenyl and N,N-diphenyl-4-biphenylamine groups on the 3, 3,5 and 2,6 positions of aza-BODIPY
core were synthesized via Suzuki-Miyaura coupling reactions while unsymmetrical analogues were obtained from the starting
mono Br-substituted aza-BODIPY material which was obtained from nitrosolated pyrrole derivative. The characterizations were
1
13
performed by means of H-NMR, C-NMR, FTIR and HRMS-TOF-ESI techniques. The spectral properties of the aza-BODIPY
derivatives were investigated using absorption and fluorescence spectroscopy. The novel compounds with extended conjugation
have broadband absorption in near infrared region and show significant shifts on their absorption and fluorescence spectra
compared to unsubstituted analogues. The highest bathochromic shifts were observed π-extended and strong electron donating
groups at 3,5 positions of the aza-BODIPY scaffold. Depend on substitution positions of attached groups to the indacene core, the
fluorescence quantum yields of chromophores were determined to be drastic changes. The singlet oxygen generation capability
of the compounds were evaluated and 2,6-bromine substituted compounds AA1 and CC1 showed high singlet oxygen quantum
yields (71% and 74%, respectively). Enhanced photophysical properties such as intense absorption, extended conjugation and
singlet oxygen production make the investigated aza-BODIPYs promising candidates for photodynamic therapy applications and
organic photovoltaic cells in NIR region.
.
.
.
.
Keywords Aza-BODIPY Unsymmetrical aza-BODIPY Azadipyrromethenes Suzuki-Miyaura coupling NIR region dyes
Introduction
advantageous features. Sharp absorption and fluorescence
bands, large molar extinction coefficients, high fluorescence
quantum yields and high photostability [3–5] all contribute to
the appeal of these interesting compounds. Aza-BODIPY
compounds are well-known NIR dyes because of their large
NIR region absorption (700–1100 nm) [6]. This property de-
pends on a large scale 1,3,5,7 aryl substituents. Particularly
electron donating groups on 3,5-aryl substituents increase ex-
tinction coefficients and absorption maximum, however on
1,7-aryl substituted electron donating groups show minor ef-
fects. Furthermore, 2,6-substituted (β-pyrrole) groups may
cause hypsochromic shifts on the absorption wavelength and
quench fluorescence intensity of aza-BODIPY dyes [7].
Currently, aza-BODIPY dyes are used in diverse applications,
such as photodynamic therapy (PDT) [8–10], NIR-emitting
chemosensors for heavy metal determination [11], in telecom-
munication applications with strong two-photon absorption
(TPA) properties [12–14], as a chromophore group in pH
sensors [15, 16], photosensitized singlet oxygen generation
Although, the first reaction of tetraarylazadipyrromethenes
with boron (Aza-BODIPY) occurred in the early 1990s [1]
these dyes have been recognized by the studies of the
O’Shea group since 2002 [2].Aza-BODIPY dyes are aza-
analogous of difluorobora-diaza-s-indacenes (BODIPY) and
known as attractive fluorophores because of their
Supplementary Information The online version contains
supplementary material available at https://doi.org/10.1007/s10895-020-
0
2646-4.
*
Mustafa Hayvalı
Mustafa.Hayvali@science.ankara.edu.tr
1
2
Department of Chemistry, Faculty of Science, Ankara University,
Anadolu, 06100 Ankara, Turkey
Department of Chemistry, Faculty of Science and Literature, Bilecik
Şeyh Edebali University, 11230 Bilecik, Turkey

J Fluoresc
[
17, 18], organic photovoltaic cells [19, 20] and NIR fluores-
open capillares using Barnstead Electrothermal IA9100.
Fluorimetric measurements were applied on Perkin Elmer
LS55 Spectrometer and electronic excitation spectra were re-
corded on Shimadzu UV1800 spectrophotometer. Mass spec-
tral analyses were performed on an Agilent 6224 HRMS spec-
cent imaging probes [21, 22].
Photodynamic therapy (PDT) is an effective and applicable
treatment for various types of cancers and also it has been
researched for other diseases. Photosensitizer, light and oxy-
gen are essential components for PDT treatments.
Photosensitizers are specific chromophores that produces bi-
1
trometer. H-NMR spectra were recorded on VARIAN
1
Mercury 400 MHz spectrometer. H NMR chemical shifts
1
3
ological cytotoxic singlet oxygen ( O ) from the O using the
(δ) are given in ppm down fieldfrom Me Si, determined by
2
2
4
1
3
light. This makes the chromophores prominent investigating
area for the improvement of PDT applications. So that, there
have been many research papers for dye molecules such as
porphyrin derivatives [23, 24]. Porphyrins were the first pho-
tosensitizers for using clinic treatment [25], which has several
disadvantageous. First, absorption and emission wavelength
aren’t tunable with bonding side groups. Second, photons do
not penetrate tissue beyond a few millimeters due to short
absorption wavelength and low absorption leading to skin
photosensitivity and low excretion rate [26–28]. Because of
these disadvantages it has been designed new generation dyes
that have intense absorption in near IR region like BODIPY
chloroform (δ = 7.26 ppm. C NMR spectra were recorded
on VARIAN Mercury 100 MHz spectrometer. C NMR
1
3
chemical shifts (δ) are reported in ppm with the internal
CDCl δ 77.0 ppm as standard. Perkin–Elmer 100 spectrom-
3
eter (equippedwith ATR unit) was used for FT-IR spectra of
−1
the compounds in the range 650–4000 cm .
Determination of Fluorescence Quantum Yields (ΦF)
In order to determine the fluorescence quantum yields of the
dyes, comparative method (Eq. 1) [36] was applied.
[
29–31] and aza-BODIPY [17, 18] derivatives.
Herein, we present new red/NIR absorbing aza-BODIPY
2
F:AStd:n
Φ ¼ Φ ðStdÞ
ð1Þ
F
F
2
Std
series which are decorated with 4-methoxyphenyl, 2,4-
dimethoxy phenyl and triphenylamine (TFA) precursors via
Palladium-catalyzed Suzuki-Miyaura cross-coupling reactions.
Due to mild reaction conditions and commercial availability of
starting boronic acid reagents, we preferred the Suzuki-Miyaura
coupling. In addition diverse boronic acids in commercial cat-
alogs are safer than the other organometallic reagents [32]. The
Suzuki–Miyaura coupling has been successfully employed on
FStd:A:n
Where Φ (Std) is the fluorescence quantum yield of BF
Chelate of (3,5-Diphenyl-1H-pyrrol-2-yl)(3,5-
diphenylpyrrol-2-ylidene) amine (Φ = 0.34 in chloroform)
7]. F and FStd denote the areas under the fluorescence emis-
sion curves of samples and the standard, respectively. A and
AStd are the respective absorbances of the samples and stan-
dard compound at the excitation wavelengths, respectively.
The refractive indices, n and nStd of the solvents were applied.
The concentration of the dilute solutions at the excitation
F
2
F
[
3
, 3,5 and 2,6 positions of aza-BODIPY core. 3 and 3,5
substituted aza-BODIPY dyes showed absorption and emission
in the NIR region. On the other hand 2,6 substituted aza-
BODIPY derivatives showed quenching fluorescence intensity
and hypsochromic shifts compared to unsubstituted form.
Electron donating groups and extended conjugations dramati-
cally have changed photophysical properties of aza-BODIPY
core depending on substitution position. As a consequence,
these compounds seem to display enhanced photophysical
properties, which will be helpful for developing novel versatile
apparatus for organic solar cells, cellular imaging, PDT and two
photon absorption applications in longer wavelengths in chem-
ical and biological fields.
−6
wavelengths fixed at 5 × 10 M in CHCl . All spectra were
recorded at 25 °C on non-deaerated samples.
3
The Parameters for Singlet Oxygen Quantum Yields
(Φ )
Δ
To study the singlet oxygen production properties of com-
pounds, experiments were carried out in CH Cl with 1,3-
diphenyl isobenzofuran (DPBF) as a chemical singlet oxygen
trap [37]. The absorbance of DPBF was tuned around 1.0 at
2
2
414 nm and the absorbance of the sensitizers was tuned be-
tween from 0.2 to 0.3 in CH Cl . A solution of the aza-
2
2
Experimental
BODIPY derivatives and DPBF was irradiated with a
30 nm Perkin Elmer L5S55 fluorescent light and the de-
6
Materials and Characterization
crease in the absorption band of DPBF was monitored at the
intervals of 2 s. Singlet oxygen quantum yields (Φ ) were
Δ
Compounds 1a, 2a, 3a, 1b, 2b, A, B and B1 were prepared
according to a literature procedures [14, 33–35]. All solvents
were purchased from common commercial sources. The melt-
ing points of the synthesized compounds were determined in
calculated using the standard, methylene blue (MB) (Φ =
Δ
0.57 in CH Cl ), by plotting the ΔOD of DPBF against the
2
2
irradiation time. The quantum yield Φ was calculated by the
Δ
following equation [37]:

J Fluoresc
ꢀ
ꢁꢀ
ꢁ
msam
mstd
Fstd
solution was added concentrated HCl(1.40 mL), and followed
by a drop wise addition of aqueous NaNO (560 mg,
.05 mmol, in 14 mL of H O). The reaction mixture was
ΦΔsam¼ΦΔstd
ð2Þ
Fsam
2
8
2
Where sam and std. designate the aza-BODIPY photo-
sensitizer and methylene blue (MB), respectively. m is the
slope of difference in change in absorbance of DPBF
stirred for 30 min and cooled to 0 °C, and another portion of
concentrated HCl (7.00 mL) was added. The solution was
allowed to stir for 1 h, and the resulting red solid was collected
(
414 nm) with the irradiation time, F is the absorption
by filtration and washed with Et O. The solid was dissolved in
2
-
OD
correction factor, which is given by F = 1–10 . The
photosensitizers were irradiated with monochromatic light
at the peak absorption wavelength for 2 s. Absorbance
was measured for several times after each irradiation.
The slope of the graph of absorbance maxima of DPBF
at 414 nm versus the photoirradiation time for each pho-
tosensitizer was calculated.
minimal EtOH, an excess of aqueous NaOAc and ice was
added, and the solution was stirred for 1 h. The resulting solid
was collected by filtration and purified by chromatography on
silica (1:1, EtOAc/hex), resulting the product as a green solid
1
(
1.68 g, %78), mp. 186–187 °C. HNMR (400 MHz, CDCl ) δ
3
8
7
3
.11 (d, J = 8.8 Hz, 2H), 7.83 (d, J = 8.8 Hz, 2H), 7.07 (s, 1H),
.01 (d, J = 8.8 Hz, 2H), 6.99 (d, J = 8.4 Hz, 2H), 3.89 (s, 3H),
1
3
.87 (s, 3H). CNMR (100 MHz, CDCl ) δ 162.61, 161.08,
3
Synthesis
130.83, 129.08, 124.39, 122.17, 114.85, 114.32, 113.79,
−
1
5
5.53, 55.38. IR (ATR, cm ) 3228.8, 3012.8, 2841.1,
Synthesis of 2-(4-Bromophenyl)-4-(4-Methoxyphenyl)
1600.9, 1246.0. HRMS (TOF-ESI): Calcd (C H N O )
[M + H] : m/z = 309.12394; found, m/z = 309.12540.
1
8 16 2 3
+
-
1H-Pyrrole (3b)
1
-(4- bromophenyl)-4-nitro-3-(4- methoxyphenyl)butan-1-
Synthesis of BF Chelate of [3,5-Bis(4-Methoxyphenyl)
2
one (2b) (7.02 g, 18.6 mmol) was dissolved in 180 mL
MeOH/THF (1:1) mixture at room temperature. A stirred
solution was treated with KOH (5.24 g, 93.45 mmol).
After 1 h the mixture was added drop wise to a solution of
-1H-Pyrrol-2-Yl]-3,5-Bis(4- Methoxyphenyl)Pyrrol-2-Ylidene]
Amine (A1)
A solution of [3,5-bis(4-methoxyphenyl)-1H-pyrrol-2-yl]-
3,5-bis(4-methoxyphenyl)pyrrol-2-ylidene]amine (A)
(2.00 g, 3.90 mmol) in dry CH Cl (300 mL) was treated
2
00 mL %33 H SO /MeOH (v/v) at 0 °C and the solution
2 4
was stirred for further 1 h at room temperature. Water
250 mL) and ice (250 mL) were added and the mixture
2
2
(
with N,N-diisopropylethylamine (6.08 mL, 39.0 mmol) and
the mixture was stirred for 10 min at room temperature.
Then, boron trifluoride diethyl etherate (7.22 mL,
58.5 mmol) was added and the reaction mixture was stirred
at room temperature for 24 h. The mixture was washed with
water, and the organic layer dried over sodium sulfate.
Removal of solvent gave a residue, which was purified by
column chromatography on silica eluting with hexane/
was neutralized with aqueous 5 M NaOH and extracted with
CHCl (100 mL × 3). The solvent was evaporated in vacuo
3
and obtained oil was held in vacuum drying over the night.
The oil was treated with acetic acid (174 mL) and NH OAc
4
(
1
14.41 g, 0.19 mol) and the solution was heated at 100 °C for
h. The reaction mixture was cooled to room temperature,
ice (340 mL) was added, and the mixture carefully neutral-
ized with aqueous 5 M NaOH. The resulting solid was col-
lected by filtration, washed with distilled water, dried and
EtOAc (2:1, V/V) resulting the product as a dark blue solid
1
(1.84 g, 76%), mp 265–266 °C. HNMR (400 MHz, CDCl )
3
crystallized from CH Cl, resulting the product as a light
δ 8.05 (t, J = 8.2 Hz, 4H), 6.99 (d, J = 8.0 Hz, 2H), 6.98 (d,
3
blue solid (3.45 g, %56), mp228–231 °C (from chloroform).
HNMR (400 MHz, DMSO) δ 11.42 (s, 1H), 7.61 (d, J =
J = 8.0 Hz, 2H), 6.91 (s, 1H), 3.88 (s, 3H), 3.87 (s, 3H)
1
13
CNMR (100 MHz, CDCl ) δ 161.68, 160.87, 157.78,
3
8
.0 Hz, 2H), 7.50 (d, 2H), 7.23 (s, 1H), 6.89 (s, 1H), 6.88 (d,
145.14, 144.65, 142.74, 131.49, 131.45, 131.40, 130.73,
125.49, 124.38, 117.09, 117.08, 114.13, 114.08, 55.40,
1
3
J = 8.0 Hz, 2H), 3.73 (s, 3H). CNMR (100 MHz, DMSO)
δ 157.11, 131.93, 131.39, 130.76, 128.18, 125.49, 125.19,
1
cm ) 3437.1, 3014.7, 2835.4, 1242.1. HRMS (TOF-ESI):
Calcd (C H BrNO) [M + H] : m/z = 328.03371; found,
−
1
55.38. IR (ATR,m ) 3005.1, 2837.3, 1597.1, 1384.9,
1251.8. HRMS (TOF-ESI): Calcd (C H BF N O )
24.74, 118.02, 116.16, 113.93, 103.62, 54.93. IR (ATR,
3
6
30
2
3
4
−
1
+
[M] : m/z = 617.22976; found, m/z = 617.23289.
+
1
7
14
m/z = 328.03328.
Synthesis of BF Chelate of [4-Bromo-3-(4-Methoxyphenyl)
2
-5-(4- Methoxyphenyl)-1H-Pyrrol-2-Yl]
Synthesis of 3,5-Bis(4-Methoxyphenyl)-2-Nitroso-1H-Pyrrole
-[4-Bromo-3-(4-Methoxyphenyl)-5-(4-Methoxyphenyl)
Pyrrol-2-Ylidene]Amine (AA1)
(
4a)
2
7
,4-bis(4-methoxyphenyl)-1H-pyrrole (3a) (1.95 g,
.00 mmol) was dissolved in EtOH (70 mL). To a stirred
A solution of BF chelate of [3,5-bis(4-methoxyphenyl)-
1H-pyrrol-2-yl]-3,5-bis(4-methoxyphenyl)pyrrol-2-
2

J Fluoresc
ylidene]amine (A1)(1.23 g, 2.00 mmol) in dry CH Cl2
Synthesis of BF Chelate
2
2
(
(
100 mL) was added to N-bromosuccinimide (NBS)
0.78 g, 4.40 mmol), and the mixture was stirred at room
of [4-N,N-Diphenylaminophenyl-3-(4-Methoxyphenyl)
-5-(4-Methoxyphenyl)-1H-Pyrrol-2-Yl]
temperature for 24 h. After the reaction was completed,
the solvent was evaporated in vacuo. Afterwards, the res-
idue was washed with water, and dried over sodium sul-
fate. The residual was purified by column chromatogra-
phy on silica eluting with hexane/EtOAc (2:1) which gave
-[4-N,N-Diphenylaminophenyl-3-(4-Methoxyphenyl)
-5-(4-Methoxyphenyl)Pyrrol-2-Ylidene]Amine (A4)
Compound A4 was prepared from BF Chelate of [4-Bromo-
2
3-(4-methoxyphenyl)-5-(4-methoxyphenyl)-1H-pyrrol-2-
y l ] - [ 4 - b r o m o - 3 - ( 4 - m e t h o x y p h e n y l ) - 5 - ( 4 -
methoxyphenyl)pyrrol-2-ylidene]amine (AA1) (0.19 g,
0.25 mmol), 4-(diphenylamino)phenylboronic acid
(173.5 mg, 0.60 mmol), Pd(PPh ) (13 mg, 0.0012 mmol)
the product as a dark brown solid (1.31 g, 84%), mp >
1
3
2
6
50 °C. HNMR (400 MHz, CDCl ) δ 7.90 (d, J = 8.0 Hz,
3
H), 7.76 (d, J = 8.8 Hz, 2H), 6.98 (d, J = 9.2 Hz, 2H),
.98 (d, J = 9.2 Hz, 2H), 3.88 (s, 3H), 3.85 (s, 3H).
CNMR (100 MHz, CDCl ) δ 161.55, 160.80, 157.14,
3
4
1
3
and K CO (0.23 g, 1.66 mmol) according to the method for
2 3
3
1
1
3
44.01, 141.99, 141.98, 132.40, 132.36, 131.38, 123.51,
21.98, 113.59, 113.52, 55.38, 55.27. IR (ATR, cm )
A2. The residual was purified by column chromatography on
−
1
silica eluting with toluene which gave the product as a purple
1
003.2, 2835.4, 1599.0, 1379.1, 1249.9. HRMS (TOF-
solid (53 mg, 19%) mp > 350 °C. HNMR (400 MHz, CDCl )
3
+
ESI): Calcd (C36H28BBr F N O ) [M + H] : m/z =
δ 7.53 (d, J = 8.8 Hz, 2H), 7.46 (d, J = 8.8 Hz, 2H), 7.25 (t, J =
2
2
3
4
7
76.05657; found, m/z = 776.06088.
8.0 Hz, 4H), 7.07 (d, J = 7.2 Hz, 2H), 7.01 (t, J = 7.4 Hz, 2H),
6
8
.89 (d, J = 8.8 Hz, 2H), 6.84 (d, J = 8.4 Hz, 2H), 6.83 (d, J =
.4 Hz, 2H), 6.80 (d, J = 8.4 Hz, 2H), 3.84 (s, 3H), 3.81 (s,
1
3
Synthesis of BF Chelate
3H); CNMR (100 MHz, CDCl ) δ 160.68, 159.78, 157.89,
2
3
of [4-Methoxyphenyl-3-(4-Methoxyphenyl)
147.48, 146.66, 145.16, 139.78, 132.44, 129.21, 127.36,
124.76, 124.58, 124.44, 123.26, 123.04, 122.97, 113.23,
113.14, 55.24, 55.14. IR (ATR, cm ) 3032.1, 2835.4,
-
-
-
5-(4-Methoxyphenyl)-1H-Pyrrol-2-Yl]
[4-Methoxyphenyl-3-(4-Methoxyphenyl)
5-(4-Methoxyphenyl)Pyrrol-2-Ylidene]Amine (A2)
−
1
1599.0, 1375.2, 1251.8. HRMS (TOF-ESI): Calcd
+
(
C H BF N O ) [M] : m/z = 1103.43936; found, m/z =
7
2
56
2 5 4
A mixture of BF2 chelate of [4-bromo-3-(4-
methoxyphenyl)-5-(4-methoxyphenyl)-1H-pyrrol-2-yl]-[4-
bromo-3-(4-methoxyphenyl)-5-(4-methoxyphenyl)pyrrol-
1103.44170.
2
-ylidene]amine (AA1) (0.23 g, 0.30 mmol), 4-
Synthesis of BF Chelate of [5-(4-Methoxyphenyl)
2
methoxyphenylboronic acid (105 mg, 0.69 mmol),
Pd(PPh ) (15.6 mg, 0.0014 mmol) and K CO (0.28 g,
-3-(4-Methoxybiphenyl)-1H-Pyrrol-2-Yl]
-[5-(4-Methoxyphenyl)-3-(4-Methoxybipheny)
Pyrrol-2-Ylidine]Amine (B2)
3
4
2
3
2
.00 mmol) were added to a round bottomed flask, and
then degassed argon for 10 min. The mixture of toluene
4 mL), ethanol (2 mL) and water (2 mL) were injected
under argon atmosphere. The solution was stirred at
5 °C for 24 h. After cooling to room temperature, the
(
A mixture of [3-(4-methoxyphenyl)-5-(4-bromophenyl)-1H-
pyrrol-2-yl][3-(4-methoxyphenyl)-5-(4-bromophenyl)pyrrol-
2-yl iden]am ine (B) (0. 23 g, 0. 30 mmol), 4-
methoxyphenylboronic acid (105 mg, 0.69 mmol),
Pd(PPh ) (15.6 mg, 0.0014 mmol) and K CO (0.28 g,
8
mixture was washed with water and extracted with
CH Cl (75 mL × 2). The solvent was evaporated under
2
2
3 4
2
3
reduced pressure. Afterwards, the residual was purified
by column chromatography on silica eluting with tolu-
2.00 mmol) were added to a round bottomed flask, and then
degassed argon for 10 min. The mixture of toluene (4 mL),
ethanol (2 mL) and water (2 mL) were injected under argon
atmosphere. The solution was stirred at 85 °C for 24 h. After
cooling to room temperature, the mixture was washed with
water and extracted with CH Cl (75 mL × 2). The solvent
ene, which gave the product as a purple solid (82 mg,
1
3
3%) mp > 350 °C. HNMR (400 MHz, CDCl ) δ 7.46
3
(
d, J = 8.8 Hz, 2H), 7.41 (d, J = 8.4 Hz, 2H), 6.90 (d,
J = 8.8 Hz, 2H), 6.79 (d, J = 8.8 Hz, 2H), 6.77 (d, J =
2
2
9
3
1
1
1
2
.2 Hz, 2Hı), 6.74 (d, J = 8.4 Hz, 2H), 3.81 (s, 3H),
was evaporated under reduced pressure. The residual was car-
ried into the next stage without further purification. The
resulting solid was dissolved in dry CH Cl (100 mL). Then,
t h e r e a c t i on m i x t u r e w a s t r e a t e d w i t h N , N -
diisopropylethylamine (0.54 mL, 3.00 mmol) and the mixture
was stirred for 10 min at room temperature. Afterwards, boron
trifluoride diethyl etherate (0.45 mL, 4.50 mmol) was added
and the reaction mixture was stirred at room temperature for
1
3
.78 (s, 6H); CNMR (100 MHz, CDCl ) δ 160.57,
3
59.73, 158.61, 157.86, 155.85, 155.81, 145.13, 139.93,
38.46, 132.44, 132.34, 131.78, 125.76, 124.72, 123.38,
2
2
−
1
13.25, 113.22, 55.20, 55.11. IR (ATR, cm ) 3034.0,
835.4, 1599.0, 1373.3, 1247.9. HRMS (TOF-ESI):
+
Calcd (C H BF N O ) [M + H] : m/z = 830.32133;
found, m/z = 830.31900.
5
0
42
2
3
6

J Fluoresc
2
4 h. The mixture was washed with water, and the organic
was purified by column chromatography on silica eluting with
layer dried over sodium sulfate.
The solvent is removed in vacuo to obtain a residue, which
was purified by column chromatography on silica eluting with
toluene which gave the product as a cobalt blue solid (178 mg,
1
57%), mp > 350 °C. HNMR (400 MHz, CDCl ) δ 8.15 (d,
3
J = 8.4 Hz, 2H), 8.07 (d, J = 8.8 Hz, 2H), 7.69 (d, J = 8.4 Hz,
2H), 7.54 (d, J = 8.8 Hz, 2H), 7.29 (t, J = 7.8 Hz, 4H), 7.15 (d,
J = 7.6 Hz, 4H), 7.13 (d, J = 8.8 Hz, 2H), 7.06 (t, J = 7.4 Hz,
toluene, resulting the product as a dark brown solid (61 mg,
1
2
6%), mp 279–280 °C. HNMR (400 MHz, CDCl ) δ 8.14 (d,
3
1
3
J = 8.8 Hz, 2H), 8.07 (d, J = 8.8 Hz, 2H), 7.67 (d, J = 8.4 Hz,
2H), 7.01 (s, 2H), 6.99 (s, 1H),3.90 (s, 3H). CNMR
2
2
H), 7.60 (d, J = 8.8 Hz, 2H), 7.00 (s, 1H), 7.00 (d, J = 8.8 Hz,
H), 6.99 (d, J = 8.8 Hz, 2H), 3.90 (s, 3H), 3.86 (s, 6H).
(100 MHz, CDCl ) δ 160.83, 158.06, 147.83, 147.47,
3
145.62, 143.13, 142.68, 133.58, 130.85, 130.16, 130.12,
130.08, 130.04, 129.32, 127.78, 126.53, 125.42, 124.72,
1
3
CNMR (100 MHz, CDCl ) δ 160.84, 159.67, 158.22,
3
−
1
1
1
1
45.57, 143.28, 143.25, 142.85, 137.25, 132.62, 130.85,
30.14, 130.10, 130.05, 129.99, 128.23, 126.64, 125.41,
25.27, 117.50, 114.32, 114.16, 109.99, 55.43, 55.35. IR
123.33, 123.21, 117.53, 114.16, 55.43. IR (ATR, cm )
3034.0, 2835.4, 1587.4, 1386.8, 1251.8. HRMS (TOF-ESI):
+
Calcd (C H BF N O ) [M + H] : m/z 1044.42605; found,
7
0
52
2 5 2
−
1
(
ATR, cm ) 3111.2, 2833.4, 1597.1, 1383.0, 1244.1.
m/z = 1044.42421.
+
HRMS (TOF-ESI): Calcd (C H BF N O ) [M] : m/z =
4
8
38
2 3 4
7
69.29236; found, m/z = 769.29487.
Synthesis of [5-(4-Methoxyphenyl)-3-(4-Methoxyphenyl)
1H-Pyrrol-2-Yl]-[5-(4-Methoxyphenyl)-3-(4-Bromophenyl)
-
Synthesis of BF Chelate of [5-(4-Methoxyphenyl)
Pyrrol-2-Ylidene]Amine (C)
2
-
-
3-(2,4-Dimethoxybiphenyl)-1H-Pyrrol-2-Yl]
[5-(4-Methoxyphenyl)-3-(2,4-Dimethoxybipheny)
3,5-bis(4-methoxyphenyl)-2-nitroso-1H-pyrrole (4a) (1.54 g,
5.0 mmol) and 2-(4-bromophenyl)-4-(4-methoxyphenyl)-1H-
pyrrole (3b) (1.64 g, 5.00 mmol) were dissolved in AcOH
(25 mL). The reaction mixture was added acetic anhydride
(5 mL) and heated to 100 °C for 1 h. Ice (100 mL) and 5 M
NaOH (100 mL) was added and the mixture was stirred for
30 min, extracted with CH Cl (100 mL × 3). The combined
Pyrrol-2-Ylidine]Amine (B3)
B3 was prepared from[3-(4-methoxyphenyl)-5-(4-
bromophenyl)-1H-pyrrol-2-yl][3-(4-methoxyphenyl)-5-(4-
bromophenyl)pyrrol-2-yliden]amine (B) (0.23 g, 0.30 mmol),
2
,4-dimethoxyphenylboronic acid (125.6 mg, 0.69 mmol),
2
2
Pd(PPh ) (15.6 mg, 0.0014 mmol) and K CO (0.28 g,
organics were dried over Na SO and the solvent was re-
3
4
2
3
2
4
2
.00 mmol) according to the method for B2.The obtained
moved under reduced pressure. The crude product was puri-
fied on a silica gel column chromatography (1:2, EtOAc/hex),
residue was purified by column chromatography on silica
eluting with toluene which gave the product as a purple solid
resulting the product as a dark green solid (2.98 g, %96), mp >
1
1
(
85 mg, 34%), mp 273–274 °C. HNMR (400 MHz, CDCl ) δ
350 °C. HNMR (400 MHz, CDCl ) δ 8.02 (d, J = 8.8 Hz,
3
3
8
8
8
3
1
1
1
.11 (d, J = 8.4 Hz, 2H), 8.07 (d, J = 8.8 Hz, 2H), 7.65 (d, J =
.4 Hz, 2H), 7.33 (d, J = 8.0 Hz, 1H), 7.01 (s, 1H), 7.01 (d, J =
.8 Hz, 2H), 6.60–6.58 (m, 2H), 3.91 (s, 3H), 3.86 (s, 6H),
2H), 7.99 (d, J = 9.2 Hz, 2H), 7.95 (d, J = 8.0 Hz, 2H), 7.68
(d, J = 8.4 Hz, 2H), 7.62 (d, J = 9.2 Hz, 2H), 7.14 (s, 1H), 7.05
(d, J = 8.0 Hz, 2H), 6.96 (s, 1H), 6.95 (d, J = 8.0 Hz, 2H), 3.92
(s, 3H), 3.88 (s, 3H), 3.85 (s, 3H). IR (ATR, cm-1) 3074.5,
2831.8, 1589.0, 1246.0. HRMS (TOF-ESI): Calcd
1
3
.83 (s, 6H). CNMR (100 MHz, CDCl ) δ 160.78, 160.73,
3
58.50, 157.71, 145.54, 143.11, 142.36, 140.88, 131.34,
30.82, 129.73, 129.50, 129.31, 129.27, 125.49, 122.65,
17.69, 114.14, 109.99, 104.81, 99.01, 55.53, 55.43. IR
+
(C H BrN O ) [M + H] : m/z = 620.13720; found, m/z =
3
5
28
3 3
620.13950.
−
1
(
ATR, cm ) 3117.0, 2831.5, 1600.9, 1379.1, 1259.5.
+
HRMS (TOF-ESI): Calcd (C H BF N O ) [M + H] :
Synthesis of BF Chelate of [5-(4- Methoxyphenyl)-3-(4-
5
0
42
2
3
6
2
m/z = 830.32133; found, m/z = 830.32234.
Methoxyphenyl)-1H-Pyrrol-2-Yl]-[5-(4-Methoxyphenyl)
-3-(4-Bromophenyl)Pyrrol-2-Ylidine]Amine (C1)
Synthesis of BF Chelate of [5-(4-Methoxyphenyl)
2
-
-
3-(4-N,N-Diphenylaminobiphenyl)-1H-Pyrrol-2-Yl]
[5-(4-Methoxyphenyl)-3-(4-N,N-Diphenylaminobiphenyl)
C1 was prepared from [5-(4-methoxyphenyl)-3-(4-
methoxyphenyl)-1H-pyrrol-2-yl]-[5-(4-methoxyphenyl)-
3-(4-bromophenyl)pyrrol-2-ylidene]amine (C) (1.08 g,
Pyrrol-2-Ylidine]Amine (B4)
1
.75 mmol), N,N-diisopropylethylamine (3.05 mL,
B4 was prepared from [3-(4-methoxyphenyl)-5-(4-
bromophenyl)-1H-pyrrol-2-yl][3-(4-methoxyphenyl)-5-(4-
bromophenyl)pyrrol-2-yliden]amine (B) (0.23 g, 0.30 mmol),
17.5 mmol),boron trifluoride diethyl etherate (3.24 mL,
26.25 mmol) and dry CH Cl (300 mL) according to the meth-
od for B1.The residual was purified by column chromatogra-
2
2
4
-(diphenylamino)phenylboronic acid (199.5mg, 0.69mmol),
phy on silica eluting with hexane/EtOAc (2:1, v/v) which gave
Pd(PPh ) (15.6 mg, 0.0014 mmol) and K CO (0.28 g,
the product as a dark brown solid (1.02 g, 87%), mp 245–
3
4
2
3
1
2
.00 mmol) according to the method for B2.The residual
246 °C. HNMR (400 MHz, CDCl ) δ 8.09 (d, J = 9.2 Hz,
3

J Fluoresc
2
H), 8.06 (d, J = 9.2 Hz, 2H), 8.02 (d, J = 9.2 Hz, 2H), 7.88 (d,
8.4 Hz, 4H), 8.06 (d, J = 9.2 Hz, 2H), 8.05 (d, J =
8.8 Hz, 2H), 7.66 (d, J = 8.4 Hz, 2H), 7.60 (d, J =
8.8 Hz, 2H), 7.00 (d, J = 8.0 Hz, 4H), 6.99 (d, J =
8.4 Hz, 4H), 6.96 (s, 1H), 6.96 (s, 1H), 3.89 (s, 6H),
J = 8.4 Hz, 2H), 7.59 (d, J = 8.4 Hz, 2H), 7.01 (d, J = 8.8 Hz,
2
2
3
1
1
1
1
2
H), 6.99 (d, J = 8.8 Hz, 2H), 6.99 (t, 1H), 6.98 (d, J = 8.8 Hz,
H), 6.84 (s, 1H), 3.90 (s, 3H), 3.89 (s, 3H), 3.88 (s,
1
3
13
H). CNMR (100 MHz, CDCl ) δ 162.35, 161.10, 160.65,
3.87 (s, 3H), 3.86 (s, 3H); CNMR (100 MHz, CDCl3)
3
60.38, 154.90, 131.89, 131.84, 131.79, 131.67, 131.19,
30.96, 130.85, 130.80, 130.76, 130.68, 125.58, 125.02,
24.71, 123.72, 117.96, 117.93, 116.43, 114.32, 114.19,
δ 161.98, 160.85, 160.63, 159.61, 158.99, 156.85,
145.74, 144.97, 143.54, 143.52, 142.49, 142.35, 142.33,
137.86, 132.71, 131.71, 131.66, 131.61, 130.85, 130.73,
130.26, 130.01, 129.96, 129.92, 129.02, 128.20, 126.59,
125.59, 125.28, 124.10, 117.50, 117.15, 117.10, 117.09,
114.31, 114.21, 114.12, 114.10, 55.40, 55.34. IR (ATR,
−
1
14.14, 55.45, 55.43, 55.41. IR (ATR, cm ) 3003.2,
835.4, 1597.1, 1379.1, 1253.7. HRMS (TOF-ESI): Calcd
+
(
C H BBrF N O ) [M] : m/z = 666.13753; found, m/z =
35
27
2 3 3
−
1
6
66.13917.
cm ) 3032.1, 2833.4, 1599.0, 1384.9, 1251.8. HRMS
+
(
TOF-ESI): Calcd (C H BF N O ) [M + H] : m/z =:
42 34 2 3 4
Synthesis of BF Chelate of [4-Bromo-3-(4-Methoxyphenyl)
694.26888; found, m/z = 694.27082.
2
-
-
5-(4-Methoxyphenyl)-1H-Pyrrol-2-Yl]
[4-Bromo-3-(4-Methoxyphenyl)-5-(4-Bromophenyl)
Synthesis of BF Chelate of [5-(4-Methoxypheny)
2
Pyrrol-2-Ylidene]Amine (CC1)
-3-(4-Methoxypheny)-1H-Pyrrol-2-Yl]-[5-(4-Methoxypheny)
-3-(2,4-Dimethoxybiphenyl)Pyrrol-2-Ylidine]Amine (C3)
CC1 was prepared from BF2 chelate of [5-(4-
methoxyphenyl)-3-(4- methoxyphenyl)-1H-pyrrol-2-
yl]-[5-(4-methoxyphenyl)-3-(4-bromophenyl)pyrrol-2-
ylidine]amine (C1) (0.40 g, 0.60 mmol), N-bromosuccinimide
C3 was prepared from [5-(4-methoxyphenyl)-3-(4-
methoxyphenyl)-1H-pyrrol-2-yl]-[5-(4-methoxyphenyl)-
3-(4-bromophenyl)pyrrol-2-ylidene]amine (C) (0.18 g,
0.30 mmol), 2,4-dimethoxyphenylboronic acid (60.05 mg,
0.33 mmol), Pd(PPh ) (7.80 mg, 0.0007 mmol) and K CO
(
NBS) (0.22 g, 1.26 mmol) and CH Cl (150 mL) according
2 2
to the method for AA1. The residual was purified by column
3
4
2
3
chromatography on silica eluting with hexane/EtOAc (2:1, V/
(0.28 g, 2.00 mmol) according to the method for B2.The ob-
tained residue was purified by column chromatography on
silica eluting with toluene which gave the product as a dark
V) which gave the product as a dark brown solid (0.41 g,
1
8
3%), mp 292–293 °C. HNMR (400 MHz, CDCl ) δ 7.90
3
1
(
9
d, J = 8.8 Hz, 4H), 7.88 (d, J = 9.2 Hz, 4H), 7.77 (d, J =
.2 Hz, 2H), 7.59 (s, 4H), 6.99 (d, J = 8.8 Hz, 4H), 6.98 (d,
J = 9.2 Hz, 2H), 3.89 (s, 3H), 3.88 (s, 3H), 3.86 (s, 3H).
brown solid (89 mg, 41%), mp 228–229 °C. HNMR
(400 MHz, CDCl ) δ 8.09 (d, J = 9.2 Hz, 2H), 8.07 (t, J =
3
8.6 Hz, 4H), 8.06 (d, J = 9.2 Hz, 2H), 7.64 (d, J = 8.8 Hz,
2H), 7.33 (d, J = 8.4 Hz, 1H), 7.00 (d, J = 8.8 Hz, 2H), 6.99
(d, J = 8.8 Hz, 4H), 6.61–6.57 (m, 2H), 6.98 (s, 1H), 6.96 (s,
1H), 3.90 (s, 6H), 3.88 (s, 3H), 3.87 (s, 3H), 3.83 (s, 3H).
1
3
CNMR (100 MHz, CDCl ) δ 162.01, 161.11, 160.80,
3
1
1
1
5
1
59.54, 154.22, 144.92, 144.91, 143.37, 143.36, 141.17,
41.16, 132.53, 132.48, 132.33, 131.96, 131.26, 128.81,
25.11, 123.52, 123.19, 121.52, 113.68, 113.64, 55.40,
1
3
CNMR (100 MHz, CDCl ) δ 161.90, 160.81, 160.70,
3
−
1
5.38, 55.33. IR (ATR, cm ) 3001.2, 2835.4, 1599.0,
160.84, 157.69, 157.03, 154.03, 132.51, 131.62, 131.61,
131.55, 131.33, 130.82, 130.74, 129.91, 129.46, 129.23,
129.20, 129.11, 125.36, 124.19, 120.37, 117.41, 117.36,
114.19, 114.13, 114.11, 109.99, 104.79, 99.01, 55.53,
3 7 7 . 2 , 1 2 4 6 . 0 . H R M S ( T O F - E S I ) : C a l c d
+
(
C H BBr F N O ) [M + H] : m/z = 823.95650; found,
3
5
25
3 2 3 3
m/z = 823.95874.
−
1
5
5.48, 55.43, 55.40. IR (ATR, cm ) 3066.8, 2835.3,
Synthesis of BF Chelate of [5-(4-Methoxypheny)
1597.0, 1383.0, 1271.1. HRMS (TOF-ESI): Calcd
2
+
-
-
3-(4-Methoxypheny)-1H-Pyrrol-2-Yl]-[5-(4-Methoxypheny)
3-(4-Methoxybiphenyl)Pyrrol-2-Ylidine]Amine (C2)
(C H BF N O ) [M + Na] : m/z = 746.26140; found,
4
3
36
2
3
5
m/z = 746.26448.
C2 was prepared from[5-(4-methoxyphenyl)-3-(4-
methoxyphenyl)-1H-pyrrol-2-yl]-[5-(4-methoxyphenyl)-
Synthesis of BF Chelate of [5-(4-Methoxypheny)
2
-3-(4-Methoxypheny)-1H-Pyrrol-2-Yl]-[5-(4-Methoxypheny)
-3-(4-N,N-Diphenylaminobiphenyl)Pyrrol-2-Ylidine]Amine
(C4)
3
0
0
-(4-bromophenyl)pyrrol-2-ylidene]amine (C) (0.18 g,
.30 mmol), 4-methoxyphenylboronic acid (51.47 mg,
.33 mmol), Pd(PPh ) (7.80 mg, 0.0007 mmol) and
3
4
K CO (0.28 g, 2.00 mmol) according to the method for
B2.The obtained residue was purified by column chroma-
tography on silica eluting with toluene, which gave the
C4 was prepared from[5-(4-methoxyphenyl)-3-(4-
methoxyphenyl)-1H-pyrrol-2-yl]-[5-(4-methoxyphenyl)-
3-(4-bromophenyl)pyrrol-2-ylidene]amine (C) (0.18 g,
0.30 mmol), 4-(diphenylamino)phenylboronic acid
(95.41 mg, 0.33 mmol), Pd(PPh3 )4 (7.80 mg,
2
3
product as a purple solid (106 mg, 50%), mp
1
2
61 °C. HNMR (400 MHz, CDCl ) δ 8.10 (t, J =
3

J Fluoresc
0
.0007 mmol) and K CO (0.28 g, 2.00 mmol) according
Results and Discussion
2
3
to the method for B2. The obtained residue was purified
by column chromatography on silica eluting with toluene
Synthesis and Coupling Reactions
which gave the product as a dark brown solid (113 mg,
1
4
5%),mp > 350 °C. HNMR (400 MHz, CDCl ) δ 8.13 (d,
Symmetrical aza-BODIPY compounds were initially synthe-
sized successfully by condensation of acetophenone and aro-
matic aldehyde derivatives. Then, unsymmetrical analogues
were obtained by pyrrole-nitrosolated pyrrole coupling reac-
tions to compare the photophysical properties of the different
substitution patterns as shown in Schemes 1 and 2. Diverse
electron donor groups are directly attached at the −2, −3, −5
and − 6 position of aza-BODIPYs. O’Shea’s procedures [2, 7]
were used in the synthesis of symmetrical aza-BODIPY com-
pounds A1 and B1. Unsymmetrical azadipyrromethene com-
pound C was synthesized by condensation of 2-(4-
bromophenyl)-4-(4-methoxyphenyl)-1H-pyrrole(3b) and 3,5-(4-
methoxyphenyl)-2-nitroso-1H-pyrrole (4a) and afforded in high
(96%) yield. The compounds A1 and C1 compounds were treated
with 2.1 equiv. of N-bromosuccinimide (NBS) in CH Cl at room
3
J = 8.4 Hz, 2H), 8.10 (d, J = 9.6 Hz, 2H), 8.07 (d, J =
8
8
8
.8 Hz, 2H), 8.06 (d, J = 9.2 Hz, 2H), 7.68 (d, J =
.8 Hz, 2H), 7.54 (d, J = 8.4 Hz, 2H), 7.29 (t, J =
.0 Hz, 4H), 7.17–7.14 (m, 4H), 7.13 (s, 1H), 7.06 (t,
J = 7.4 Hz, 2H), 7.01 (d, J = 9.2 Hz, 4H), 7.00 (d, J =
.8 Hz, 4H), 6.97 (s, 1H), 3.90 (s, 6H), 3.88 (s, 3H).
8
1
3
CNMR (100 MHz, CDCl ) δ 162.76, 161.97, 160.87,
3
1
1
1
1
60.85, 147.50, 142.37, 137.61, 136.59, 135.78, 135.69,
31.64, 131.60, 131.34, 130.29, 130.05, 129.99, 129.94,
29.31, 127.76, 126.51, 125.60, 125.32, 124.70, 123.38,
23.18, 114.22, 114.14, 114.12, 55.43, 55.41. IR (ATR,
cm ) 3032.1, 2833.4, 1589.4, 1386.8, 1251.8. HRMS
TOF-ESI): Calcd (C53H41BF N O ) [M] : m/z =
−
1
+
(
8
2
4
3
30.32400; found, m/z = 830.32609.
2
2
temperature. AA1 and CC1 were obtained with 83% and 84%
yields, respectively. -3, −3,5, −2,6 aryl bromine substituted
azadipyrromethene ligands and aza-BODIPY complexes were de-
signed as starting materials for Suzuki-Miyaura coupling reactions.
Reactions were performed with 4-methoxyphenylboronic acid,
2 , 4 - D i m e t h o x y p h e n y l b o r o n i c a c i d ,
4-(diphenylamino)phenylboronic acid as electron donating groups
in the presence of tetrakis(triphenylphosphine)palladium(0)
[Pd(PPh ) ] in H O/EtOH/Toluene (1:1:2, by volume) mixture at
Synthesis of BF Chelate
of [4-Methoxyphenyl-3-(4-Methoxyphenyl)
2
-
-
5-(4-Methoxyphenyl)-1H-Pyrrol-2-Yl]
[4-Methoxyphenyl-3-(4-Methoxyphenyl)-5-(4-Bromophenyl)
Pyrrol-2-Ylidene]Amine (CC2)
CC2 was prepared from BF chelate of [4-Bromo-3-(4-
2
3 4
2
methoxyphenyl)-5-(4-methoxyphenyl)-1H-pyrrol-2-yl]-[4-
bromo-3-(4-methoxyphenyl)-5-(4-bromophenyl)pyrrol-2-
ylidene]amine (CC1) (0.21 g, 0.25 mmol), 4-
methoxyphenylboronic acid (136.8 mg, 0.95 mmol),
Pd(PPh ) (19.5 mg, 0.0018 mmol) and K CO (0.35 g,
85 °C for 24 h. Compounds B2-B4 and C2-C4 were obtained by
one pot synthesis using aryl bromine substituted
azadipyrromethene ligands. Compounds A2, A4 and CC2 were
synthesized 2,6-dibromine, 2,6-dibromine and 3,4-bromophenyl
substituted aza-BODIPY derivatives (Schemes 1 and 2). All reac-
tions have been monitored by TLC analysis and reaction mixture
chromatographed by using silica gel.
3
4
2
3
2
.50 mmol) according to the method for A2.The obtained
residue was purified by column chromatography on silica
eluting with toluene which gave the product as a dark
The yields of the coupling reactions were found to change
depending on the reactivity of 3, 3,5 and 2,6 positions of the
aza-BODIPY core (Scheme 3). 3 positions of the aza-
BODIPY compounds C2, C3 and C4 have been obtained with
50, 41 and 45% yields, respectively. 3,5 positions of com-
pound B4 has been obtained higher yield in 57%. On the other
hand 3,5 position analogue compounds B2 and B3 have been
obtained a relatively smaller yield of 26 and 34%. It was
observed that the lower yields arise from the poor solubility
of the compounds in reaction solvents. Similarly, coupling
reactions on the 2,6 substituted aza-BODIPY compounds
A2 and A4 gave the relatively poor yields (33% and 19%,
respectively). The poor coupling yields may also be attributed
to steric hindrance of the 2,6 positions of the indacene core
caused by the existence of 1,7 phenyl groups on the indacene
core. Apart from that, when the Suzuki-Miyaura coupling re-
action has been performed with 2,3,6 tri-bromine substituted
compound CC1 with excess boronic acid derivative, no all
1
brown solid (48 mg, 21%) mp > 350 °C. HNMR
(
400 MHz, CDCl ) δ 7.48 (d, J = 9.2 Hz, 2H), 7.46 (d,
3
J = 8.4 Hz, 2H), 7.42 (d, J = 8.8 Hz, 2H), 7.38, J = 8.4 Hz,
2
6
H), 7.31 (d, J = 8.8 Hz, 2H), 6.90 (d, J = 8.8 Hz, 4H),
.88 (d, J = 8.8 Hz, 2H), 6.79 (d, J = 8.8 Hz, 2H), 6.78 (d,
J = 8.8 Hz, 2H), 6.75 (d, J = 8.8 Hz, 2H), 6.74 (d, J =
8
3
1
1
1
1
1
5
1
.8 Hz, 2H), 3.81 (s, 6H), 3.79 (s, 3H), 3.78 (s, 3H),
1
3
.78 (s, 3H). CNMR (100 MHz, CDCl ) δ 161.01,
3
60.39, 160.00, 159.79, 158.79, 158.65, 154.7, 154.65,
46.05, 144.43, 141.14, 139.43, 139.40, 139.39, 132.51,
32.42, 132.11, 131.74, 131.68, 131.12, 131.07, 131.04,
30.92, 130.15, 129.02, 128.20, 125.36, 125.34, 125.28,
24.72, 124.36, 122.75, 113.92, 113.88, 113.32, 55.22,
−
1
5.16, 55.12. IR (ATR, cm ) 3072.6, 2837.3, 1599.0,
3 6 5 . 6 , 1 2 4 6 . 0 . H R M S ( T O F - E S I ) : C a l c d
+
(
C H BBrF N O ) [M + H] : m/z = 880.21922; found,
4
9
39
2
3
5
m/z = 880.22060.

J Fluoresc
3 4 2 3 2 3 2 2 2
Scheme 1 Synthetic pathway of the symmetrical aza-BODIPY Dyes (i) Pd(PPh ) , K CO , ArB(OH) , 85 °C, 24 h. (ii) BF OEt , DIEA, CH Cl , rt.,
2
4 h
target products have been obtained. Only 2,6 4-
methoxyphenyl substituted aza-BODIPY compound has been
isolated from this reaction and afforded in 21% yield
7.46, compared to 2,6 unsubstituted aza-BODIPY com-
pounds. These results show that the electronic properties of
aza-BODIPY core at 2,6 positions could be changed markedly
1
(
Scheme 3). This may indicates the region selectivity in cou-
[40]. Interestingly, HNMR of 3 bromine substituted aza-
pling reactions on 2,6 positions compared to 3 or 3,5 positions
on the aza-BODIPY scaffold [38, 39].
BODIPY compound CC1 was observed only one sharp sin-
glet peak in 7.59 ppm corresponding to four aryl protons
(Fig. 1). Similar singlet peak was observed our previous study
Spectroscopy and Photophysical Properties
at 2,3,5,6 bromine substituted aza-BODIPY compounds [41].
This effect can be observed in para-disubstituted benzene hav-
ing two identical substituents, because all of the hydrogens are
magnetically equivalent stemming from the symmetry in the
molecule.
1
Identification of the compounds was performed through H-
1
3
1
NMR, C-NMR, FTIR and HRMS. In HNMR of symmet-
rical aza-BODIPYs, the 2,6 pyrrole protons appear as a singlet
between 6.91 to 7.00 ppm. However, unsymmetrical aza-
BODIPY compounds, the pyrrole protons appear as two sin-
glet signals in different ppm and these protons were disap-
peared in 2,6 phenyl or bromine substituted aza-BODIPY
compounds. 1,3,5,7 aryl protons of compounds A1, B1, B2,
B3, B4, C2, C3, C4 were observed between 8.05 to 8.15 ppm.
On the other hand, 2,6 phenyl substituted A2, A4 and CC2
compounds were monitored to upfield shift between 7.53 to
High resolutions mass spectra (HRMS-ESI-TOF) of the
compounds A1, A4, B2, C1 and A, A2, B3, B4,C, C2-C4
showed molecular and protonated molecular ion peaks, re-
+
spectively and compound C3 gave [M-Na] molecular ion
peaks. Isotope peaks were observed depending on the number
of bromine atoms to bromine substituted aza-BODIPY com-
pounds consisted with the assigned formulations. For in-
stance, the spectrum for compound CC1 consisting of three

J Fluoresc
3 4 2 3 2 3 2 2 2
Scheme 2 Synthetic pathway of the unsymmetrical aza-BODIPY dyes (i) Pd(PPh ) , K CO , ArB(OH) , 85 °C, 24 h. (ii) BF OEt , DIEA, CH Cl , rt.,
2
4 h
bromine atoms was revealed M, M + 2, M + 4 and M + 6 peak
groups as shown in Fig. 2.
positions (AA1 and CC1) involves 12 and 11 nm
hypsochromic shift compared to A1 and C1. Owing to the
introduction of methoxyphenyl and triphenylamine groups
onto the 2 and 6 positions in the aza-BODIPY moiety, com-
pounds A2 and A4 shows lower hypsochromic shift compared
to A1. However, 10 nm bathochromic shift was observed
when compared to AA1 compound. In emission spectra, all
2,6-substituted compounds gave reduced fluorescence quan-
tum yields. Besides, quenched fluorescence was observed for
the compound A4 due to the strong electron donating behav-
ior of directly linked triphenylamine group to the aza-
BODIPY core.
The photophysical parameters, measured in CHCl solu-
3
tion (5 × 10− M), are reported in Table 1. The absorption
spectra of all aza-BODIPY derivatives exhibited two intense
peaks, In the UV region (between 311 to 351 nm, correspond-
ing to the π → π*transitions and the major characteristic ab-
sorption bands in the NIR region (between 672 to 718 nm,
S → S transitions) (Fig. 3). The extinction coefficients for
6
0
1
newly synthesized series are high, in the range of 20,400–
1
−1
5
4
1,600 M− cm for high energy region and in the range of
−1
−1
6,600–147,600 M cm for the low energy region.
The Stokes shifts for these new series are generally narrow
600–1045 cm ), except for the compound B4 (1443cm ).
Furthermore, substitution of bromine atoms in the 2,6
The 3 and 3,5 π-extended aza-BODIPYs (B2-B4 and C2-
C4) containing electron donating groups showed significant
bathochromic shifts on both absorption and emission spectra
−1
−1
(
Scheme 3. Synthesis of the compound CC2

J Fluoresc
1
Fig. 1 H NMR spectra of the compound CC1
1
−1
depicted in Figs.3 and 4, respectively. 3,5 substituted series
B2/B3 (24 and 22 nm) and 3 substituted series compound C2/
C3 (12 and 11 nm) showed systematic bathochromic shifts
compared to reference compounds B1 and C1, respectively.
The largest red-shift in the series was observed for the com-
pound B4 (λabs = 718 nm), which has two strong electron-
donating and π-extended triphenylamine groups attached to
the 3,5positions of the aza-BODIPY moiety. Additionally, the
absorption bands of the triphenylamine substituted com-
pounds relatively broader and the Stokes shifts are larger com-
pared to those of methoxy substituted counterparts.
Compounds C2, C3 and C4 have electron donating groups
on 3 position of the aza-BODIPY core that exhibited red
shifted absorption maxima compared to unsubstituted com-
pound C1. Note that, the highest molar absorption coefficient
was observed 3 π-extended and 2,4-dimethoxyphenyl
substituted unsymmetrical aza-BODIPY compound C3 (ε
=147,000 M− cm ). And also unsymmetrical compound
C2 showed the highest fluorescence quantum yield (Φ =
F
0.44).
It’s clear from the graphs that the triphenylamine group as
an electron donor forms a charge transfer state [14].The
triphenylamine substituted compounds have lower molar ab-
sorption coefficients and quantum yields. Conversely, the aza-
BODIPY derivatives with weaker electron donating groups or
unsubstituted aza-BODIPYs have higher values (see Table 1).
Note that, the fluorescence quantum yields of the compounds
A1, B1 and C1 which have only difference on the 3 position
of the core structure as bromine and methoxy group don’t
differ greatly. This may be explained by the equally capable
of donating electrons of relevant ones to the aza-BODIPY
core when the appended to 3,5 positions of the core. As a
general result, compared to unsubstituted analogues, the
bathochromic shifts between 40 and 50 nm both in absorption
Fig. 2 HRMS-ESI-TOF spectra
of the compound CC1

J Fluoresc
Table 1 Summary of the
ε[M− cm ]
1
−1
FWHM (nm)
Stokes Shifts (cm−1)
Φ
Compound
λ
abs(nm)
λ
em(nm)
F
photophysical properties of the
aza-BODIPY dyes. All spectra
were measured in chloroform
A
324/628
336/692
680
–
46,400/60200
20,400/89400
61,600
60/90
51
–
–
A1
AA1
A2
A4
B
722
718
738
–
600
77
0.360
0.015
0.004
–
57
690
46,600
83
943
–
311/690
315/615
330/674
344/698
315/696
351/718
318/619
331/683
672
42,000/52600
54,200/54400
20,200/62400
22,800/77400
27,400/75200
51,600/61000
33,800/39600
24,800/72600
85,800
130
46/90
63
–
–
–
B1
B2
B3
B4
C
708
744
738
801
–
712
886
819
1443
–
0.310
0.430
0.410
0.010
–
66
66
91
63/97
54
C1
CC1
C2
C3
C4
CC2
714
711
729
733
735
732
636
816
671
767
660
1045
0.360
0.004
0.440
0.230
0.036
0.001
58
339/695
310/694
344/701
680
21,400/68800
43,400/147600
41,600/83000
66,200
59
58
73
89
and emission spectra were provided by coupling reactions for
the new dyes.
In order to determine the singlet oxygen production fea-
tures of the novel compounds, singlet oxygen generation
study with 1,3-diphenylisobenzofuran (DPBF) scavenger
was carried out in solution (Figs. 5 and 6).
The formation of triplet state by intersystem crossing (ISC)
in emissive molecules causes the fluorescence quenching that
makes them potential candidates in singlet oxygen production.
In this regard, singlet oxygen generation was expected to ob-
tain only non-emissive compounds [42]. Therefore, com-
pounds A1, B1-B3 and C1-C3 were not expected any singlet
oxygen efficiency due to the high fluorescence quantum
yields (Table 1). Thus, we have tested non-emissive symmet-
rical and asymmetrical compounds which substituted 3, 3,5
and 2,6 π-extended and electron donating groups (A2, A4,
B4, C4 and CC2). Our singlet oxygen determination studies
shows that compounds A2, A4, B4, C4 and CC2 have not
changed singlet oxygen efficient of aza-BODIPY dyes, al-
though these compounds have showed weak emission fea-
tures. This may due to radiationless decay to the ground state
instead of energy or electron transfer to the triplet state of
designed aza-BODIPY dyes [43]. However, 2,6 dibromine
substituted aza-BODIPY compounds AA1 and CC1 were
showed high singlet oxygen quantum yields because of the
heavy atom effect of bromine atoms [7, 41]. So that com-
pounds AA1 and CC1 solution with DPBF were observed
decrease in absorption spectra at 414 nm (Figs. 5 and 6,
respectively). The Singlet oxygen quantum yields of the com-
pounds AA1 and CC1 were calculated 71% and 74% in DCM
against methylene blue which was used as standard, respec-
tively. Based on the results from literature, halogenated aza-
BODIPY compounds generally show higher singlet oxygen
production values about %70 (ΦΔ =0.70 in DCM) [8, 10, 44].
From this point, it can be concluded that the compounds AA1
and CC1 also have to some degree elevated singlet oxygen
Fig. 3 Normalized absorption spectra of aza-BODIPY dyes (5 × 10−6 M, in CHCl
)
3

J Fluoresc
Fig. 4 Emission spectra of the aza-BODIPY dyes (5 × 10−6 M, in CHCl
)
3
production capabilities. Note that, even the compounds have
close features in the production of singlet oxygen, novel com-
pounds could be excited with lower energy. In this respect,
extending the π-electron system and asymmetric structure of
the aza-BODIPYs via Suzuki-Miyaura coupling do not make
them efficient sensitizer in photodynamic therapy
applications.
reactions effect of photophysical and spectroscopic properties.
2,6 substituted aza-BODIPY compounds showed drastically
change in the electronic properties as well as fluorescence,
absorption intensities and stokes shifts were altered dramati-
cally. And also these series were synthesized with poor yields
compared to 3 and 3,5 positions because of the steric hin-
drance. The highest bathochromic shifts were observed π-
extended and strong electron donating groups at 3,5 positions.
Our previous work indicated that extended π-conjugation and
strong electron donating groups cause increased two-photon
absorption properties of aza-BODIPY dyes at telecommuni-
cation wavelengths. Furthermore, 2,6-dibromine substituted
aza-BODIPY compounds AA1 and CC1 were exhibited sig-
nificantly high singlet oxygen quantum yields were found to
be 71 and 74% respectively. These data may open an effective
perspective and these compounds could be good candidates
for diverse applications such as photodynamic therapy (PDT)
and two photon absorption (2PA). In particular, synthesized
compounds may be applicable for n-type semiconductors on
Conclusions
In summary, we prepared 3, 3,5 and 2,6 substituted symmet-
rical and unsymmetrical aza-BODIPY dyes via Pd-catalyzed
Suzuki-Miyaura cross coupling reactions. The Suzuki-
Miyaura coupling reactions on aza-BODIPY derivatives in
3
,5 [44–46] and 2,6 [40] positions are very limited and also
3
positions reactions of the unsymmetrical aza-BODIPY com-
pounds were the first example in the literature. In this paper,
we reported that at 3, 3,5 and 2,6 positions Suzuki-Miyaura
Fig. 5 5Absorption spectra of DPBF upon irradiation in the presence of the compound AA1 for 14 s (recorded at 2 s interval) and plot of change in
absorbance of DPBF at 414 nm vs irradiation time (λex = 630 nm) against methylene blue (MB) as the standard in CH Cl
2
2

J Fluoresc
Fig. 6 Absorption spectra of DPBF upon irradiation in the presence of the compound CC1 for 14 s (recorded at 2 s interval) and plot of change in
absorbance of DPBF at 414 nm vs irradiation time (λex = 630 nm) against methylene blue (MB) as the standard in CH Cl
2 2
8
.
Gallagher WM, Allen LT, O'Shea C, Kenna T, Hall M, Gorman A,
Killoran J, O'Shea DF (2005) A potent nonporphyrin class of pho-
todynamic therapeutic agent: cellular localisation, cytotoxic poten-
tial and influence of hypoxia. Br J Cancer 92:1702–1710
organic photovoltaic cells (OPVs) due to the several desirable
characteristics, for instance, long wavelength absorption, high
FWHM and high molar absorption coefficients, as a subject of
future study.
9. McDonnell SO, Hall MJ, Allen LT, Byrne A, Gallagher WM,
O'Shea DF (2005) Supramolecular photonic therapeutic agents. J
Am Chem Soc 127:16360–16361
Funding This research did not receive any specific grant from funding
agencies in the public, commercial, or not-for-profit sectors.
10. O'Connor AE, Mc Gee MM, Likar Y, Ponomarev V, Callanan JJ,
O'Shea DF, Byrne AT, Gallagher WM (2012) Mechanism of cell
2
death mediated by a BF -chelated tetraaryl-azadipyrromethene
photodynamic therapeutic: dissection of the apoptotic pathway
in vitro and in vivo. Int J Cancer 130:705–715
Compliance with Ethical Standards
Conflicts of Interest/Competing Interests The authors declare that they
have no known competing financial interests or personal relationships
that could have appeared to influence the work reported in this paper.
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