The synthesis, characterization, crystal structure and photophysical properties of a new meso-BODIPY substituted phthalonitrile

Article abstract of DOI:10.1007/s10895-015-1609-y

A new highly fluorescent difluoroboradipyrromethene (BODIPY) dye (4) bearing an phthalonitrile group at meso-position of the chromophoric core has been synthesized starting from 4-(4-meso-dipyrromethene-phenoxy)phthalonitrile (3) which was prepared by the

Full text of DOI:10.1007/s10895-015-1609-y

J Fluoresc
DOI 10.1007/s10895-015-1609-y
ORIGINAL ARTICLE
The Synthesis, Characterization, Crystal Structure
and Photophysical Properties of a New Meso-BODIPY
Substituted Phthalonitrile
1
2
2
3
4
Pinar Sen & Göknur Yaşa Atmaca & Ali Erdoğmuş & Necmi Dege & Hasan Genç
&
5
1
Yusuf Atalay & S. Zeki Yildiz
Received: 2 April 2015 /Accepted: 30 June 2015
Springer Science+Business Media New York 2015
#
A b s t r a c t A n e w h i g h l y f l u o r e s c e n t
difluoroboradipyrromethene (BODIPY) dye (4) bearing an
phthalonitrile group at meso-position of the chromophoric
core has been synthesized starting from 4-(4-meso-
dipyrromethene-phenoxy)phthalonitrile (3) which was pre-
pared by the oxidation of 4-(2-meso-dipyrromethane-
phenoxy)phthalonitrile (2). The structural, electronic and
photophysical properties of the prepared dye molecule were
investigated. The final product exhibit noticeable spectroscop-
ic properties which were examined by its absorption and fluo-
rescence spectra. The original compounds prepared in the re-
action pathway were characterized by the combination of FT-
obtained as single crystal which crystallized in the triclinic
space group P-1 with a=9.0490 (8) Å, b=10.5555 (9) Å, c=
11.7650 (9) Å, α=77.024 (6)°, β=74.437 (6)°, γ=65.211 (6)°
and Z=2. The crystal structure has intermolecular C—H···F
weak hydrogen bonds. The singlet oxygen generation ability
of the dye (4) was also investigated in different solvents to
determine of using in photodynamic therapy (PDT).
.
.
.
Keywords Bodipy Synthesis Crystal structure
.
.
.
Phthalonitrile Fluorescence Electronic spectra
photodynamic therapy
1
13
IR, H and C NMR, UV–vis and MS spectral data. It has
been calculated; molecular structure, vibrational frequencies,
Introduction
1
13
H and C NMR chemical shifts and HOMO and LUMO
energies of the title compound by using B3LYP method with
-311++G(dp) basis set, as well. The final product (4) was
The advancement of emissive dyes for applications in organic
fluorescent areas is steadily growing in recent years.
B o r a d i a z a i n d a c e n e s ( B O D I P Y d y e s , B D P s ,
difluoroboradipyrromethenes, etc.) are well known fluores-
cent dyes with many distinctive and desirable properties.
They have high molar absorption coefficients which emit rel-
atively sharp fluorescence peaks with high quantum yield and
long excited singlet state life time [1]. Among the large variety
of known highly fluorescent organic compounds BODIPY
derivatives have been recognised as very convenient
fluorophores in many applications such as fluorescent labeling
of biomolecules [2], energy transfer cassettes [3], photosensi-
tizer in photodynamic therapy [4], fluorescence probes as
chemosensors for the selective and efficient detection of
chemically and biologically important ionic species [5], fluo-
rescent switches [6] and drug delivery agents [7]. Because of
these fluorescence properties, various BODIPY dyes are also
commercially available for protein labelling [8].
6
Electronic supplementary material The online version of this article
doi:10.1007/s10895-015-1609-y) contains supplementary material,
which is available to authorized users.
(
*
S. Zeki Yildiz
szy@sakarya.edu.tr
1
2
3
4
5
Faculty of Arts and Sciences, Department of Chemistry, Sakarya
University, 54187 Sakarya, Turkey
Faculty of Arts and Sciences, Department of Chemistry, Yıldız
Technical University, 34210 Esenler, Istanbul, Turkey
Faculty of Arts and Sciences, Department of Physics, Samsun
Ondokuz Mayıs University, 55139 Samsun, Turkey
Fatih Faculty of Education, Primary Science Education Department,
Karadeniz Technical University, 61300 Sogutlu, Akcaabat, Turkey
So far, several reviews were published explaining most of
the knowledge about BODIPY dyes [9]. A BODIPY
Faculty of Arts and Sciences, Department of Physics, Sakarya
University, 54187 Sakarya, Turkey

J Fluoresc
chromophore is composed of two units of pyrrole which are
connected by a methene bridge in the 2-position and a boron
atom which is coordinated by the heteroatoms.
irradiations for singlet oxygen determination were measured
using a General Electric quartz line lamp (300 W). A 600 nm
glass cut off filter (Schott) and a water filter were used to filter
off ultraviolet and infrared radiations respectively. An inter-
ference filter (Intor, 700 nm with a bandwidth of 40 nm) was
additionally placed in the light path before the sample. Light
intensities were measured with a POWER MAX5100 (Mol
electron detector incorporated) power meter. Mass spectra
were recorded on a AB SCIEX 4000 QTRAP LC-MS/MS
spectrometer and Waters SYNAPT MS system HRMS
(High Resolution Mass Spectrometer) in electrospray positive
ion mode. The elemental analyses were performed on a
Costech ECS 4010 instrument.
Small modifications in the chromophoric core of these dyes
enable tuning of their spectroscopic / photophysical properties
in the way of altering of electron releasing / withdrawing
groups on the pyrrole core [10], central meso position [11]
and the boron substituents [12] of BODIPY framework. This
kind of substitutions can have a strong influence on the posi-
tion of the absorption and emission maxima which range from
at about 500 nm to over 700 nm depending on their location
on the BODIPY core [13, 14].
In this study, we report the synthesis and characterization of
new meso-substituted BODIPY derivative. We have also stud-
ied the absorption, fluorescence spectroscopic properties and
the singlet oxygen production capacity of the fluorophore
which is the fluorescence materials. The crystal structure of
the prepared BODPY dye was also investigated.
Computational Procedure
The molecular structure of BODIPY in the ground state (in
vacuo) is computed by performing the density functional the-
ory (DFT) by a hydrid functional B3LYP functional (Becke’s
three parameter hybrid functional using the LYP correlation
functional) methods [17, 18] at 6-311++G(d,p) level. The op-
Experimental
1
13
timized geometrical structure, IR spectra, H and C NMR
chemical shifts and HOMO and LUMO energies of BODIPY
in this study are carried out by using Gauss-View molecular
visualization program [19] and Gaussian 09 W program pack-
age [20]. Additionally, harmonic vibrational frequencies for
the title compound are calculated with these methods and then
scaled by 0.9615 [21] and these results were compared with
the experimental data.
Materials and Measurements
Pyrrole, 4-hydroxybenzaldehyde was purchased from Sigma-
Aldrich Company. The deuterated chloroform (CDCl ) for
3
NMR spectroscopy and the following chemicals were obtain-
ed from Sigma-Aldrich; TEA, TFA, benzene, hexane, MeOH,
THF, DMSO, AcOH, CH Cl (DCM), Chloroform (CHCl ),
2
2
3
2
,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), BF3-
OEt and FeCl .6H O. All other reagents and solvents were
Synthesis
2
3
2
reagent grade quality and were obtained from commercial
suppliers. All solvents were dried and purified as described
by Perrin and Armarego [15] and the solvents stored over
molecular sieves (4A°). K CO were dried over 120 °C and
used as anhydrous. 4-nitrophthalonitrile was prepared
according to literature procedure [16]. Oxygen free inert
atmosphere was supplied by argon through dual-bank
vacuum-gas manifold system. Thin-Layer chromatography
4-(4-formylphenoxy) Phthalonitrile (1)
4-nitrophthalonitrile (1.00 g, 5.78 mmol) and 4-
hydroxybenzaldehyde (0.71 g, 5.78 mmol) were dissolved in
N,N-dimethylformamide (15 mL) and degassed with argon in
a dual-bank vacuum-gas manifold system. After stirring for
15 min, finely ground anhydrous potassium carbonate (2 g,
14.45 mmol) was added portion-wise within 2 h period with
the efficient stirring. The progress of the reaction was moni-
tored by TLC using DCM / hexane (3/1) solvent system. The
stirring of the suspension was maintained at room temperature
for further 24 h. The resulting mixture was poured into an
iced-water/acetone mixture (5/1: v/v). The occured precipitate
was collected by filtration, washed several times with ethanol
and dried in vacuo. The desired pure compound (1) was ob-
tained as a yellowish powder in sufficient purity. Yield 1.30 g,
2
3
(
TLC) was performed using silica gel 60 HF254 as an adsor-
bent. Column chromatography was performed with silica gel
(
Merck grade 60).
Melting points (m.p.) were determined using a Barnstad-
Electrotermel 9200 apparatus and are uncorrected. Electronic
spectra were recorded on a Shimadzu’s UV-2700 with quartz
cell of 1 cm. Infrared spectra were recorded on a Perkin Elmer
Spectrum two FT-IR spectrophotometer equipped with Perkin
Elmer UATR-TWO diamond ATR and corrected by applying
the atr-correction function of Perkin Elmer Spectrum soft-
TM
90 %. m.p. 154 °C. FT-IR (PIKE MIRacle ATR) ν max/
1
13
−1
ware. H and C NMR spectra were recorded a Varian
Mercury Plus 300 MHz spectrometer. Fluorescence spectra
were measured using a Varian Eclipse spectrofluorometer
using 1 cm path length cuvettes at room temperature. Photo-
cm : 3105-3041(Ar, C-H), 2805–2764 (OC-H), 2237 (C≡N),
1691 (C=O), 1587–1506 (Ar, C=C), 1489–1309 (C-C), 1255
(Ar-O-Ar), 1209, 1155, 1111, 1087, 950, 858, 839, 821. H-
1
NMR (CDCl ) δ (ppm) : 10.03 (s, 1H, OCH)), 8.01 (d, 2H,
3

J Fluoresc
ArH), 7.81 (d, 1H, ArH), 7.41–7.34(m, 2H, ArH), 7.23 (d, 2H,
4-(4-meso-BOBIPY-phenoxy)phthalonitrile (4)
1
3
ArH). C-NMR (CDCl ) δ (ppm): 190.7, 160.3, 159.1,
3
1
35.9, 134.1, 132.6, 123.0, 122.9, 120.59, 118.2, 115.3,
A s o l u t i o n o f 4 - ( 4 - m e s o - d i p y r r o m e t h e n e -
114.9, 110.6.
phenoxy)phthalonitrile 3 (0.40 g, 1.02 mmol) in toluene
(15 mL) was purged with Ar. To the solution, 10 equiv of
TEA (1.45 mL, 10.2 mmol) was added and heated to 70 °C
for 0.5 h. Then, 15 equiv of BF -OEt (2 mL, 15.3 mmol) was
4
-(4-meso-dipyrromethane-phenoxy)phthalonitrile (2)
3
2
added and the reaction mixture was heated to reflux tempera-
ture for 3.5 h. After completion of the reaction the reaction
mixture was cooled to room temperature, washed with 0.1 M
NaOH solution (3×25 mL) and the layers were separated off.
The organic layer was dried with anhydrous Na SO , filtered
4
-(4-formylphenoxy)phthalonitrile (1) (1.00 g, 4.03 mmol)
was dissolved in freshly distilled pyrrole (7 mL, 0.10 mol).
The mixture was degassed by bubbling with Ar for 15 min.
TFA (30.8 μL, 0.40 mmol, 0.1 equiv based on the benzalde-
hyde) was added to the solution and the mixture was stirred
under Ar for 25 min. at room temperature until no starting
aldehyde detected by TLC (THF/Hexan-1/3). The mixture
was diluted with dichloromethane (50 mL) and than washed
with 0.1 M NaOH solution (50 mL) and sufficient amount of
water, respecively. The organic phase was dried with Na SO ,
filtered and the solvent was evaporated under reduced pres-
sure. Column chromatography (on silica gel, THF/ hexane/
TEA-25/75/1) was applied to yield 0.90 g (61 %) of pure
dipyrromethane 2, m.p. 93 °C. FT-IR (PIKE MIRacle
ATR) ν max/cm : 3381 (N-H), 3101–3039 (Ar, C-H),
2
4
and the solvent was removed under reduced pressure. The res-
idue was chromatographed on silica gel eluting with THF/
Hexan-2/3 to obtain pure BODIPY derivative 4 (0.35 g,
TM
74 %). m.p., 205 °C. FT-IR (PIKE MIRacle ATR) ν max/
−1
cm : 3115–3038 (Ar, C-H), 2232 (C≡N), 1685 (C=N), 1590–
1537 (Ar, C=C), 1481–1386 (C-C and C-H def.), 1250 (Ar-O-
2
4
1
Ar), 1110 (N-B), 1077 (B-F), 977, 777. H-NMR (CDCl ) δ
3
(ppm): 7.97 (s, 2H, ArH), 7.83 (d, 1H, ArH), 7.69 (d, 2H, ArH),
7.43–7.37 (m, 2H, ArH), 7.27–7.25 (m, 2H, PyrH), 6.97 (d,
TM
13
2H, PyrH), 6.60 (d, 2H, PyrH). C-NMR (CDCl ) δ (ppm):
3
−
1
160.7, 159.2, 145.6, 144.9, 135.9, 135.02, 133.1, 131.7, 122.5,
122.6 120.4, 119.2, 119.1, 118.2, 115.4, 115.01, 110.2.
2
1
7
1
6
2
1
961–2855 (Alip. C-H), 2231 (C≡N), 1685 (C=N), 1607–
500 (Ar, C=C), 1484–1421 (C-C), 1248 (Ar-O-Ar), 1088,
1
17. H-NMR (CDCl ) δ (ppm): 8.03 (br, 2H, NH), 7.71 (d,
3
Table 1 Crystal data and structure refinement for the title compound
H, ArH), 7.32–7.23 (m, 4H, ArH), 7.02 (d, 2H, ArH), 6.74-
.72 (m, 2H, PyrH), 6.19-6.16 (m, 2H, PyrH), 5.92-5.89 (m,
H, PyrH), 5.51 (s, 1H, AlipH). C-NMR (CDCl3) δ (ppm):
61.9, 152.5, 140.8, 135.7, 132.2, 130.8, 121.7, 121.7, 120.9,
Chemical formula
Color/shape
23 2 4
C H13BF N O
1
3
Firebrick/prism
Triclinic
Crystal system
Space group
117.9, 117.8, 115.7, 115.2, 109.0, 108.8, 107.7, 43.6.
P −1
Temperature
296 K
Unit cell dimensions
a=9.0490(8) Å
b=10.5555(9) Å
c=11.7650(9) Å
α=77.024(6)°
β=74.473(6)°
γ=65.211(6)°
4
-(4-meso-dipyrromethene-phenoxy)phthalonitrile (3)
4
2
-(4-meso-dipyrromethane-phenoxy) phthalonitrile 2 (0.75 g,
.05 mmol) was dissolved in benzene (10 mL). A solution of
DDQ (0.58 mg, 2.5 mmol) dissolved in benzene (10 mL) was
added and the mixture stirred for 1 h at room temperature until
no starting molecule was detected by TLC (THF/Hexan-1/3).
The black precipitate formed during the reaction was filtered-
off, washed with benzene and the filtrate was purified by col-
umn chromatography (silica gel, THF/hexane/TEA-25/75/1)
to give 3 as orange solid (0.55 g, 72 %), m.p. 180 °C. FT-IR
3
Volume
974.70(15) Å
Z
2
1.398 Mg m−
0.71073 Å
10,815
3
Density (calculated)
Wavelength
Reflections collected
Independent reflections
4041
TM
−1
(
3
PIKE MIRacle ATR) ν max/cm : 3286 (N-H), 3106–
035 (Ar, C-H), 2232 (C≡N), 1679 (C=N), 1591–1500 (Ar,
Absorption correction
Δρmax, Δρmin (e Å−3)
Integration X-RED
0.17, −0.25
1.01
1
C=C), 1485–1354 (C-C), 1247 (Ar-O-Ar), 1209, 726. H-
S
NMR (CDCl ) δ (ppm) : 8.38 (d,1H, ArH), 8.30 (s, 1H,
3
Rint
0.046
NH), 7.81–7.59 (m,3H, ArH), 7.41 (d, 1H, ArH), 7.37–7.15
θ range for data collection (°)
Absorbtion coefficient (μ)
Final R indices [I>2r(I)]
h/k/l
2.1≤θ≤26.5
0.10 mm
(
m, 3H, PyrH), 6.98 (s, 1H, PyrH), 6.62–6.43 (m, 2H, PyrH).
−1
1
3
C-NMR (CDCl ) δ (ppm): 163.5, 162.0, 156.2, 145.4,
3
R
1
=0.050, wR
2
=0.121
1
1
35.4, 134.4, 133.36, 131.2, 128.1, 123.4, 123.4, 122.5,
21.8, 119.82, 118.3, 117.4, 115.8, 115.5, 112.1, 108.9, 107.9.
−10, 11/ −13, 13/ −14, 14

J Fluoresc
recorded absorption maxima and given as Log ε.
Correspondingly, the excitation and emission wavelengths
were listed in the table, as well. The Stokes shifts were calcu-
lated as the differences from the recorded absorption and
emission bands. The concerned results were discussed in the
results part.
X-ray Crystal Structure Determination
3
A firebrick single crystal sized (0.17×0.36×0.49) mm was
chosen and mounted on a glass fiber then carefully mounted
on goniometer of a STOE IPDS II diffractometer and used for
the structure determination for the crystallographic study. All
difraction measurements were collected on an Stoe IPDS II
diffractometer with graphite monochromatized Mo Kα radia-
tion (λ=0.71073 Å) using the ω scan method. A total of 11,
Scheme 1 Reagent and conditions: (i). 4-nitrophthalonitrile, DMF,
CO3, (90 %); (ii). freshly distilled pyrrole, TFA, rt, 20 min., (61 %);
iii). benzene, DDQ, rt, 1 h, (72 %); (iv). Toluene, TEA, BF -OEt , rt→
0 °C→130 °C, 2,5 h, (74 %)
1
2
30 independent reflections were collected, among which
599 reflections were considered as observed [I>2σ(I)] and
K
(
7
2
3
2
used for the structure refinement. Usual Integration X-RED 32
absorption corrections were applied. All diffraction measure-
ments were performed at 296 K using monochromated Mo
Kα radiation.
Electronic Spectra Measurements
The absorption spectra of compound 4 were recorded in dif-
ferent solvents altering from non-polar to polar. The stock
Data Collection
solutions were prepared in DCM, CHCl , THF, EtOH, DMF
3
−4
and DMSO at around 1×10 M concentration depending of
the weights. The prepared solutions were stored in dark, and
diluted to 1×10− M concentration for the measurements. The
freshly diluted solutions were used for absorption, excitation
and emission measurements. The molar absorptivity coeffi-
cients presented in Table 6 were calculated from the related
Single-crystal X-ray data were collected on a Stoe IPDS II
[22] single crystal diffractometer using monochromated
MoKα radiation at 296 K. For the title compound (4) data
colleciton: X-AREA; cell refinement: X-AREA [22]; data re-
duction: X-RED32 [18, 23]. The structure was solved by di-
rect methods followed by fourier synthesis using SHELXS-
7
Table 2 Experimental and
theoretical vibrational bands of
the BODIPY compound
Assigments
FT-IR
B3lyp
Freq
Assigments
Freq
FT-IR
B3lyp
Freq
Freq
Intensity
Freq
Intensity
υS(CH)
3115–3038
3151
3150
3138
3137
3126
3125
3099
3097
3092
3084
3081
3072
3068
2188
2184
1456
2.601
4.554
1.844
3.608
3.554
4.577
1.270
0.606
2.390
3.306
3.089
3.857
8.813
6.705
31.21
55.01
υ(C=C)
1590–1537
1582
1567
1552
1536
1529
1485
1471
1457
1391
1376
1218
1107
1034
933
2.866
272.6
121.3
173.9
379.2
111.6
154.9
4.183
24.95
229.2
406.5
350.8
192.7
165.1
18.78
υS(CH)
υ(C=C)
υAS(CH)
υAS(CH)
υAS(CH)
υAS(CH)
υS(CH)
υ(C=C)
υ(C=C)
υ(C=C)
υ(C=C)+β(CH)
υ(C=C)+β(CH)
υ(C=C)+β(CH)
υ(C=C)+β(CH)
υ(C=C)+β(CH)
υ(CO)
1481–1386
υAS(CH)
υS(CH)
υAS(CH)
υAS(CH)
υAS(CH)
υAS(CH)
υ(C≡N)
1250
1110
1077
977
υ(NB)
υ(BF)
2232
1685
υ(BF)
υ(C≡N)
υ(C=N)
υ(BF)
777
764

J Fluoresc
2
014 [19, 24] and refined on F2 by full-matrix least-squares
methods using SHELXL-2014 [24] and molecular figures:
ORTEP-3 for Windows version 2014.1 implemented in
WinGX 2014 [25–27] program suit. The general-purpose
crystallographic tool PLATON [28] were used for the struc-
ture analysis and used to prepare material for publication. All
non-hydrogen atoms were refined anisotropically. All hydro-
gen atoms were generated geometrically and allowed to ride
on their parent carbon atoms. All H atoms attached to C atoms
were fixed geometrically and treated as riding with C―H=
0
.93 Å and Uiso(H)=1.2 Ueq(C). Details of the data collec-
tion conditions and parameters of refinement process are giv-
en in Table 1.
Fig. 1 a Theoretical calculated structure of title compound, b Ortep
diagram of the title compound, showing the atomic numbering scheme.
Displacement ellipsoids are drawn at the 50 % probability level
Result and Discussion
Synthesis
nitrophthalonitrile using K CO as catalyst in DMF with stir-
2
3
The synthetic route used to obtain BODIPY derivative (4) is
presented in Scheme 1.
The meso-substituted BODIPY dye (4) was obtained as
purple crystaline solid from a serial reaction described as fol-
lows. The reaction of 4-hydroxybenzaldehyde and 4-
ring at room temperature for 24 h gave 4-(4-formylphenoxy)
phthalonitrile (1). The dipyrromethane derivative 2 was pre-
pared in 61 % yield by the condensation of the benzaldehyde
derivative 1 with 25 equivalent of freshly distilled pyrrole in
the presence of catalytic amount of trifluoroacetic acid (TFA)
at room temperature as described by Lindsey for meso-
substituted dipyrromethane [29]. The subsequent oxidation
was applied in benzene with 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ) at room temperature to yield (72 %)
dipyrromethene derivative 3 as orange solid. The complexa-
tion of compound 3 with triethylamine and boron trifluoride
etherate in refluxing toluene gave the chelated product 4 as
purple solid after isolating by the column chromatography
13
1
Table 3 Theoretical and experimental C and H isotropic chemical
shifts with respect to TMS all values in ppm
Atoms Experimental B3LYP Atoms Experimental B3LYP
1
H
13C
C1
H37
H30
H8
7.97
7.15
7.14
6.77
6.71
6.57
6.53
6.46
6.07
5.72
5.71
5.64
5.58
5.52
160.7
159.2
145.6
162.07
157.3
147.6
146.9
142.3
135.5
135.2
135.2
135.1
132.8
131.7
129.9
129.8
121.4
121.0
119.7
119.2
118.6
118.0
116.9
116.8
112.9
C13
C35
C29
C25
C10
C38
C39
C5
7.83
(silica gel, eluent: THF/Hexan-2/3) in 74 % yield.
H16
H19
H9
7.69
Characterization of the products was carried out by a com-
7.43–7.37
144.9
135.9
135.0
1
13
bination of methods including FT-IR, H NMR, C-NMR,
melting point, UV–vis and Mass spectroscopy. All the spectral
data are in accordance with the proposed structures.
H17
H18
H34
H7
7.27–7.25
W h e n c o m p a r e d t h e F T- I R s p e c t r a o f p -
hydroxybenzaldehyde and 1, the disappearance of –OH
133.1
C11
C15
C26
C32
C12
C6
H28
H36
H30
6.97
6.60
131.7
122.5
122.6
120.4
119.2
119.1
118.2
C3
C14
C33
C27
C2
115.4
115.01
110.2
C22
C4
Fig. 2 Crystal packing diagram for the title molecule

J Fluoresc
Table 4 Hydrogen-bond geometry (Å, °)
appearance of new peaks in aromatic region were the evidence
of the formation of phthalonitrile derivative 1 has occurred.
The H-NMR spectrum of 2 was very obvious in the view of
D—H···A
D—H
H···A
D···A
D—H···A
1
i
C23—H23···F1
0.93
0.93
2.45
2.35
3.348 (3)
3.189 (2)
163
150
conversion of aldehyde group of compound 1 to the
dipyrromethane, which was relevant to the disappearance of
aldehyde proton at 10.03 ppm and the appearance of NH
ii
C3—H3···F2
Symmetry codes: (i)−x+1, −y+2, −z; (ii) x+1, y−1, z+1
1
protons of pyrrole groups at 8.03 ppm. Similarly, in H-
NMR spectrum of 3, the appearance of NH protons of pyrrole
groups at 8.30 ppm was attributed to conversion of
dipyrromethane to dipyrromethene. On the other hand, the
vibration at 3158 cm−1 and the appearance of new absorption
−1
bands at 2237 and 1255 cm belonging to the -C≡N and Ar-
O-Ar respectively, clearly indicate the formation of 1.
In the FT-IR spectrum of 2, the C=O vibration at 1691 cm-1
1
disappearance of this NH proton at the H-NMR spectrum
of 4 showed that the chelation was occurred, as well. Also in
−1
and the aldehyde C-H vibrations at 2805–2764 cm of com-
pound 1 disappeared. However the existence of NH groups
1
13
this study, the H and C NMR spectra were calculated using
B3LYP method with 6-311++G(dp) basis set, given in
Table 3.
−1
appeared at 3381 cm was clearly indicated the formation of
the compound 2. The similar characteristics were observed in
the FT-IR spectrum of 3 except the peak attributed to N-H
13
In the C-NMR spectrum of 1, the presence of the signals
at 115.3 and 114.9 ppm attributed to the nitrile carbon atoms is
the obvious difference from p-hydroxybenzaldehyde.
−1
stretching shifted to 3286 cm . The formation of Boron-
dipyrrin complex (4) with the complexation of free donor sites
was confirmed by the lack of N-H vibration and the precence
13
However, the C NMR data accord with the expected struc-
tures of 2, 3 and the Boron-dipyrrin complex 4 exhibit sym-
metric carbon signals in their spectra.
−1
of B-F stretching band at 1077 cm . The B-F band was cal-
−1
culated at: 1034 cm using B3LYP method with 6-311++
G(dp) basis set. In the rest of the spectrum, the stretching
−
1
vibrations at 2232 cm for -C≡N, between 1579 and
Description of the Crystal Structure
1
−1
1
537 cm− for aromatic -C=C-, and 1250 cm for Ar-O-Ar
were very similar to that of 3. The other vibration bands of
Theoretical calculated structure of the title compound, meso-
BOBIPY substituted phthalonitrile (4) is presented at Fig. 1b.
The calculated molecular structure was compared with molec-
ular shape obtained from the collected X-ray data and present-
ed as the ortep diagram in Fig. 1a. Both molecules were
matched for bond angles and bond distances.
BODIPY given in Table 2.
1
13
The H-NMR and C-NMR data gave satisfactory infor-
1
mation about the proposed structures. When compared the H-
NMR spectra of p-hydroxybenzaldehyde and 1, the disappear-
ances of OH proton signal of p-hydroxybenzaldehyde and the
Table 5 Some experimental and
Exp.
B3LYP
Exp.
B3LYP
theoretical bond distances and
angles (Å, deg) of the BODIPY
molecule
C1—O1
1.368 (2)
1.365
C12—C15
1.474 (3)
1.368 (3)
1.391 (3)
1.533 (3)
1.539 (3)
110.7 (2)
109.58 (19)
110.7 (2)
109.8 (2)
106.54 (16)
121.28 (15)
−169.2 (2)
7.6 (3)
1.485
C4—C7
1.437 (3)
1.427
B1—F2
1.411
C7—N1
1.136 (3)
1.155
B1—F1
1.433
C8—N2
1.137 (3)
1.154
B1—N4
1.603
C9—O1
1.388 (2)
1.392
B1—N3
1.604
O1—C1—C2
O1—C1—C6
N1—C7—C4
N2—C8—C5
C14—C9—O1
C10—C9—O1
F2—B1—F1
115.29 (17)
123.41 (18)
177.6 (3)
115.97
123.72
178.4
F2—B1—N4
111.70
107.92
107.96
111.72
106.97
120.54
−148.09
18.65
F1—B1—N4
F2—B1—N3
178.6 (3)
178.05
120.19
118.45
110.36
−178.97
176.41
161.18
−10.42
−25.54
95.9
F1—B1—N3
115.81 (19)
122.73 (19)
109.46 (19)
−178.72 (18)
172.98 (19)
172.3 (2)
N4—B1—N3
C1—O1—C9
N4—B1—N3—C19
N4—B1—N3—C16
F1—B1—N4—C23
N3—B1—N4—C23
F2—B1—N4—C20
F1—B1—N4—C20
N3—B1—N4—C20
O1—C1—C2—C3
O1—C9—C10—C11
C20—C15—C16—C17
C12—C15—C16—C17
F2—B1—N3—C19
F1—B1—N3—C19
−62.6 (3)
178.7 (2)
−130.6 (2)
108.6 (2)
−10.2 (3)
−25.54
148.13
−159.96
78.50
−5.5 (3)
−48.8 (3)
72.2 (3)
−18.48

J Fluoresc
1
Chloroform
DMSO
3
00
DMSO
DMF
0
0
0
0
0
0
0
0
0
.9
.8
.7
.6
.5
.4
.3
.2
.1
0
Dichloromethane
DMF
THF
EtOH
200
100
Chloroform
DCM
EtOH
THF
0
4
00
500
600
700
Wavelenght (nm)
Fig. 5 Emission spectra of compound 4 in different solvents.
Concentration: 1×10
−5
M
respectively. BODIPY group substituted at C15 phenyl ring
with phthalonitrile group at O1, respectively. Phenyl rings are
essentially planar but BODIPY group is non planar. All rings
are not coplanar. The maximum deviation of the A ring and
the B ring from planarity are 0.167 Å for atom C4 and
3
10
360
410
460
510
560
Wavelength (nm)
Fig. 3 UV–vis spectra of compound 4 in different solvents.
Concentration: 1×10−
7
M
0
.0067 Å for atom C12, respectively. The plane of the pheno-
late ring makes dihedral angles of 67.365 (0.062) with the
planes of rings A.
The molecular structure, an ORTEP-III [27] and the theo-
retical geometry views of which are shown Fig. 1, crystallizes
in the Triclinic space group P −1 with two molecules in the
unit cell. The crystal structure analysis shows that the title
molecule contain a 4,4-difluoro-4-bora-3a,4a-diaza-s-
indacene (BODIPY), a phthalonitrile and a dioxolane seg-
ments in the asymmetric unit. Figure 1a shows the molecular
structure of the title compound with the atomic numbering
scheme. The title compound (4) contains two phenyl rings
In the title compound (4), while the B―F bond distances
are 1.391 (3) Å for B1―F1 and 1.368 (3) Å for B1―F2 and
this bond calculated at: 1.433 and 1.411 Å, using B3LYP
method with 6-311++G(dp) basis set, respectively. The
B―N bond distances are found at: 1.539 (3) Å for B1―N3
and 1.533 (3) Å for B1―N4, this bond were calculated at:
1
.604 and 1.603 Å, respectively. The F1―B1―N3,
F1―B1―N4 and F1―B1―F2 bond angles are found at:
10.7 (2)°, 109.58 (19)° and 109.46 (19)°, respectively.
These bond angles are calculated at: 111.72°, 107.92° and
10.36° using B3LYP method with 6-311++G(dp) basis set,
(
ring A: C1/C2/C3/C4/C5/C6 and ring B: C9/C10/C11/C12/
1
C13/C14) with two acetonitrile group (C7/N1 and C8/N2)
substituted at C4, C5 in ring A, and one BODIPY group
C15/C16/C17/18/C19/N3/B1/F1/F2/N4/C20/C21/C22/C23,
1
respectively. These bond distances and bond angles are con-
sistent with the literature [30, 31, 36]. For the aromatic rings,
the C―C bond distances range from 1.375 (3) Å to 1.399 (3)
Å and the aromatic rings belong to molecule are essentially
planar (r.m.s. deviations are 0.0122 Å for ring A and 0.0044 Å
for ring B).
The phthalonitrile group exhibits normal geometry and is
planar. The two cyano groups deviate from this plane by
0
.0870(15) and −0.0711(17) Å at atoms N1 and N2,
3 2 2
Table 6 Fluorescence properties of 4 in CHCl , CH Cl , DMSO,
DMF, THF and EtOH
Solvent
S
0
→S
1
Excitation Emission
Ex. (nm) Em. (nm)
Stokes shift
ΔStokes (nm)
Φ
F
λmax.(nm)
λ
λ
THF
501
501
501
501
502
499
503
505
528
528
530
525
523
524
27
27
28
26
20
10
0.124
0.170
0.166
0.121
0.271
0.369
DMF
DMSO 502
EtOH
DCM
499
503
505
CHCl
3
Fig. 4 The HOMO and LUMO orbitals of the BODIPY molecule

J Fluoresc
in Chloroform
[N1—C7—C4=177.6(3)° and N2—C8—C5=178.6(3)°] are
1
.5
0
almost linear and in a good agreement with previously report-
ed values by [36–39]. In our calculation these angles were
calculated as 178.4° and 178.05 for using B3LYP method,
respectively.
The crystal packing (Fig. 2) of the title compound (4) is
stabilized by one intermolecular C23—H23⋅⋅⋅F1 and one
C3—H3⋅⋅⋅F2 hydrogen bonds with the geometric parameters
Emission
Absorption
0
4
00
500
600
700
2.45 Å, 3.348(3) Å, 162.9° and 2.35 Å, 3.489(2) Å, 150.4°,
Wavelenght (nm)
respectively. The geometric parameters belong to these hydro-
gen in Table 4. Some selected optimized geometric parameters
Fig. 6 Absorption and emission spectra of compound 4 in CHCl
3
(
bond lengths, bond angles and dihedral angles) of the title
respectively. The C≡N bond lengths [N1≡C7=1.136(3) Å
and N2≡C8=1.137(3) Å] bonds show N≡C triple bond char-
acter and are in good agreement with the literature compare
values reported in the literature [32–35]. At the same time, the
C≡N bond lengths have been calculated using B3LYP method
with 6-311++G(dp) basis set and this bonds were found as:
compound are listed in Table 5.
Electronic Spectral Characterization
The ground state electronic absorption spectra and emission
1
.155 Å and 1.154 Å, respectively. If the cyano groups are
spectra of the compound 4 have been recorded in different
considered in the molecule, the C―C―N bond angles can be
seen that near-linear. As expected, the N—C—C angles
solvents such as DCM, CHCl , THF, EtOH, DMF and
DMSO at 1×10 M concentration. Generally, BODIPYs
3
−
7
a
b
in DMF
in DMSO
0
5
1
1
sec
sec
0
5
1
1
2
sec
sec
1
.5
0
1
.5
0
0
5
sec
sec
0
5
0
sec
sec
sec
20 sec
25 sec
30 sec
0
0
25 sec
sec
3
0
3
00
400
500
600
300
400
500
600
Wavelenght (nm)
Wavelenght (nm)
c
d
in EtOH
in THF
1
1
0
sec
sec
sec
5
1
1
2
2
3
0
5
1
1
sec
0
5
0
5
0
sec
sec
sec
sec
sec
0 sec
5 sec
0.5
0
.5
20 sec
2
5 sec
0 sec
3
0
0
3
00
400
500
600
300
400
500
600
Wavelenght (nm)
Wavelenght (nm)
Fig. 7 Typical spectra for the determination of singlet oxygen quantum yield of the complex 4 in different solvents

J Fluoresc
exhibit one intense visible S →S absorption band at
(DPBF) as a quencher for singlet oxygen. Different solvents
(DMSO, DMF, THF and EtOH) were also used for compari-
son. The absorption bands of compound 4 in all solvents did
not show any changes when the absorption band of DPBF at
416 nm reduced by light irradiation (Fig. 7). These results
indicate that compound 4 did not decompose during singlet
oxygen studies under irradiation. The compound 4 in THF and
EtOH produced more singlet oxygen compared to DMSO and
DMF. The singlet oxygen generation spectra of 4 in DMSO,
DMF, THF and EtOH were given in Fig. 6.
0
1
~
500 nm [39]. Figure 3 shows the absorption spectra of the
compound 4 in the mentioned solvents for examining of their
spectroscopic properties. It is clearly understood from the ab-
sorption spectra that the BODIPY compound 4 has a sharp
strong band at the range of 499–505 nm. From the comparison
of electronic spectra of the Bor-Dipyrrin derivative
fluorophore (4), the shortest wavelength absorption was ob-
served in EtOH solution and the longest wavelength absorp-
tion in Chloroform solution. The highest occupied molecular
orbital (HOMO, −6.600 eV) and the lowest unoccupied mo-
lecular orbital (LUMO, −3.533 eV) are the main orbital taking
part in chemical reaction. The HOMO energy characterizes
the ability of electrongiving, the LUMO characterizes the abil-
ity of electron accepting, and the gap between HOMO and
LUMO characterizes the molecular chemical stability [40].
Theenergy gap(ΔE=3.067 eV) is calculated as seen Fig. 4.
Conclusion
BODIPY derivative 4 is important in relation to the synthesis
of novel and useful fluorescent material that there are some
possible application such as fluorescent labeling of biomole-
cules [2] and fluorescent probes for as selective sensor [42]
which was the motivation of this work. In the present study,
we have reported the synthesis of a BODIPY class dye with a
phthalonitrile subunit as the core compound (4) and charac-
Photophysical and Photochemical Studies
Fluorescence Quantum Yields
1
13
terized by standard methods (FT-IR, H and C-NMR spec-
troscopy, electronic spectroscopy and mass spectra). The sin-
gle crystal X-ray structure of the title compound was predicted
and its structural properties were also studied and reported in
the present work. The theoretical calculations were also per-
formed to confirm the proposed structure.
Fluorescence quantum yields (Φ ) were determined by com-
parative method [41], Eq. (1)
F
F:AStd:n2
Φ ¼ Φ
F
ð1Þ
FðStdÞ
FStd:A:n2
Std
The absorption, the fluorescence and singlet oxygen gen-
eration properties of 4 were investigated. Increased singlet
oxygen production was investigated for 4 in DMSO, DMF,
THF and EtOH. This feature may be useful for PDT applica-
tion of these dyes.
The title compound (4) is also open to prepare further
BODIPY substituted oligomeric molecules via on it. As the
phthalonitrile substituted derivative of the dye class, com-
pound 4 may be helpful in fundamental research for the syn-
thesis of BODIPY substituted phthalocyanines because of the
key starting compound of this oligomeric class. This is one of
the pioner reports in the field and we have attempted to fill this
gap in the literature.
where F and FStd are the areas under the fluorescence curves of
the BODIPY derivative (4) and the reference, respectively. A
and AStd are the absorbances of sample and reference at the
2
2
excitation wavelength, and n and n
are the refractive in-
Std
dices of solvents (nDCM :1.424, nchloroform:1.445, nTHF : 1.407,
nDMSO:1.480, nDMF :1.430, nEtOH:1.361) used for the sample
and the reference measurements, respectively . Fluorescein
was used as a standard; =0.79 in ethanol [30]. The sample
and the standard were excited at the same relevant wave-
length. The solvent effect on the quantum yield was studied
for DCM, CHCl , THF, DMSO, DMF and EtOH and the
3
emission spectra of compound 4 in these solvents were also
compared with the reference under the same conditions
(
Fig. 5). The calculated quantum yields (Φ ) in the used sol-
F
vents are different from each other; in DMSO 0.166, in DMF
.170, in THF 0.124, in DCM 0.271,in CHCl 0.369 and in
EtOH 0.121 (Table 6), respectively. Comparing these results,
Acknowledgments This work was supported by Ministry of Science,
Industry and Technology of Turkey (SANTEZ project no.
0
3
0
182.STZ.2013-1) and Research Fund of Sakarya University (project
no. 2014-02-04 007).
the highest value obtained in CHCl (Fig. 6) and the yields in
3
all solvents are lower than the fluorescein quantum yield in
ethanol.
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