Discovery of Novel D-A and D-π-A Structured Carbazole-Based Formazan Dyes: Synthesis, Characterization, and Spectroscopic Studies

Article abstract of DOI:10.1002/jhet.3581

In the current study, new carbazole-based formazan dyes, D-A and D-π-A, were synthesized, and their spectroscopic properties were studied for the first time. For this aim, carbazole aldehyde compounds were modified by the derivatization of carbazole, a na

Full text of DOI:10.1002/jhet.3581

Month 2019 Discovery of Novel D-A and D-π-A Structured Carbazole-Based Formazan
Dyes: Synthesis, Characterization, and Spectroscopic Studies
*
Cevher Gundogdu Hizliates
Department of Chemistry, Faculty of Sciences, Dokuz Eylul University, Tınaztepe Campus, 35160 Buca, Izmir, Turkey
*E-mail: cevher.gundogdu@deu.edu.tr
Received September 21, 2018
DOI 10.1002/jhet.3581
Published online 00 Month 2019 in Wiley Online Library (wileyonlinelibrary.com).
In the current study, new carbazole-based formazan dyes, D-A and D-π-A, were synthesized, and their
spectroscopic properties were studied for the first time. For this aim, carbazole aldehyde compounds were
modified by the derivatization of carbazole, a natural electron-donor compound, from 3- and 9-position.
Then, hydrazone derivatives were synthesized from these aldehyde derivatives. Finally, D-A (5A–C) and
D-π-A (6A–C) carbazole–formazan dyes were obtained by the interaction of the hydrazone compounds with
p-substituted aniline. After characterization of the structures of these compounds, photophysical properties
of the carbazole–formazans were studied in the different polarity media (i.e., acetonitrile, toluene, and chlo-
roform) in order to detect the solvent effects. Because of the π-conjugated bridge and the electron acceptor
nitro group at the para position, D-π-A structured carbazole–formazan dye 6C showed the highest Stokes
shift of 155 nm.
J. Heterocyclic Chem., 00, 00 (2019).
INTRODUCTION
light-emitting diodes, and organic–inorganic hybrid
materials [4].
In recent days, design and development of second-order
nonlinear optical materials and two light-emitting
molecules that have high polarity and thermal stability,
good optical transparency in the visible region, good
compliance with high-performance polymer, and excellent
resolution are gaining importance with the increasing use
of two-photon technology in optoelectronics, photonics,
organic light-emitting diodes, optical power limiting,
photodynamic therapy, singlet oxygen production, the
three-dimensional micro-manufacturing, and storage of
data and three-dimensional fluorescence microscopy [1–3].
Organic π-conjugated molecules, which have both
electron donor (D) and electron acceptor group (A),
exhibit interesting optical and spectral properties with an
intramolecular charge transfer from acceptor group to the
donor. In these fluorophore molecules, the typical
embodiment is D-π-A form. It is determined that the
molecules that are designed by the binding of different
donor and acceptor groups with optimal π-conjugated
bridge show high hyperpolarization (β). This development
in β ensures the redshift of the maximum absorption
wavelength. These systems are often used in the nonlinear
optical system, the optical data storage devices, organic
Because of their biological and technological properties,
carbazole and formazans are very important compounds for
chemists. Carbazoles are well known conjugated, good
hole-transporting, electron-donor, and planar compounds
[5–8]. Carbazole derivatives are important optical
materials owing to their inherent electron-donating and
nonlinear optical properties, hole-transporting capabilities,
and high charge carrier mobilities, and high thermal and
photochemical stabilities [9,10]. Therefore, these
compounds are used in a wide range of electronic and
photonic applications such as photo-refractive materials
[11], photoconductors [12], nonlinear optical materials
[13,14], hole-transporting materials [15], and organic
light-emitting materials [16–20].
On the other hand, formazans have a wide application
range as dyes, ligands [21,22], and analytical reagents
because of their color changes in redox reactions like an
indicator [23]. Formazans are colored compounds due to
π–π* and n–π* transitions. Hausser et al. [24] have
shown that many formazans could be obtained in red and
yellow forms on exposure to visible light. Red formazan
molecules have hydrogen bridge show chelate, and the
yellow shows non-chelate form [25]. Formazans create
© 2019 Wiley Periodicals, Inc.

C. Gundogdu Hizliates
Vol 000
complexes and salts with transition metal ions such as
Zn, Co, Cu, Fe, Mn, and Pd(II) [26–32]. Formazans are
easily oxidized to colorless tetrazolium salts, and
tetrazolium salts are reduced back to formazans by
enzymes in the cell and stain the tissue. Because of
this feature, tetrazolium/formazan systems have been
used as indicators in marker of vitality, in screening of
anticancer drugs, and in determination of tumor cell
activity and sperm viability [33–35]. Also, it is well
known that formazans have antiviral, anti-inflammatory,
antitubercular, and antimicrobial activities [36,37].
In the present study, we intended to design and
synthesize D-A and D-π-A carbazole–formazan dyes
bearing electron-donor carbazole and electron acceptor
formazan moieties. After determination of their structural
analysis, their basic photophysical properties were
exhibited.
this indicated a weakening of the intramolecular hydrogen
bonding. In D-π-A structured compounds (6A–C), N–H
signals were observed in the downfield region at δ 15.23–
15.52 ppm, and it showed intramolecular hydrogen
bonding. In formazans, 5A–C where the carbazole ring
was substituted with –CH3 group from indole nitrogen
exhibited –NCH3 signals at δ 3.75–3.87 ppm. Methyl
hydrogens of 5B compound appeared at δ 2.46 ppm. For
5A–C and 6A–C compounds, aromatic hydrogens were
observed at their expected region. The chemical shifts of
the aromatic and –NH protons were caused by the
inductive and resonance effects of the type and position of
the substituents. From the 13C-NMR values of the
carbazole–formazans, it was observed that D-A structured
compounds 5A and 5C gave 26C and D-π-A structured
compounds 6A and 6C gave 31C peak. In compounds 5B
and 6B, one more C peak was observed because of the
p-CH3 substituent. The calculated mass and founded mass
obtained from HR–MS analyzes were determined as
compatible with each other.
The substituent effects were obtained by changing the
group at the para position of the phenyl ring, and the
solvent effect was investigated by using different polarity
solvents such as chloroform, acetonitrile, and toluene.
Photophysical properties of D-A and D-π-A structured
carbazole–formazan derivatives.
This work also
describes the photophysical characterization of carbazole–
formazans in different solvents with different polarities
such as acetonitrile, chloroform, and toluene for the
detection of solvent effect. Absorption, excitation, and
emission wavelength; molar extinction coefficients (ε),
singlet energy, Stokes’s shift, and quantum yields values
were recorded for 1 × 10ꢀ5M dye solutions; and results
were given in Table 1. Discussions were focused on λmax1
values of the carbazole–formazan derivatives, which are
characteristics of the formazan structures.
RESULTS AND DISCUSSION
Synthesis and structure.
Herein, novel D-A (5A–C)
and D-π-A (6A–C) structured carbazole-based formazan
dyes were prepared to combine the advantages of
carbazole and formazan moieties for the first time.
In this study, carbazole aldehyde phenylhydrazone (3, 4)
was obtained by the condensation reaction of carbazole
aldehyde (1, 2) and phenylhydrazine at pH 5–6. Then,
carbazole-based formazans were synthesized by coupling
of carbazole aldehyde phenylhydrazone (3, 4) with
benzene diazonium chloride derivatives at ꢀ5°C and at
pH 10–12. The synthetic route of the target compounds is
presented in Scheme 1.
In the IR spectra, N–H, C═N, and N═N stretching bands
are important for formazans. Shifting toward lower or
higher frequency of these bands determines the chelate or
non-chelate structure. For D-A derivatives, bands
observed at 3422–3425, 1590–1595, 1492–1518, and
1322–1325 and, for D-π-A derivatives, at 3422–3426,
1596–1598, 1449–1450, and 1226–1233 cmꢀ1 belonged
to N–H stretching, C═N stretching, N═N stretching, and
C–N stretching, respectively. Because of the charge
transfer from carbazole to the nitro group, 5C and 6C
decreased the vibration band of C═N group.
The fluorescence quantum yields of the carbazole–
formazan derivatives were calculated according to
formula 1, and fluorescein 27 standard in 0.1M NaOH
(Fstd: 0.95) was used as the reference standard [38]:
À
Á À
Á
Фf ¼ Фst FAst·ɳ2 = FstAɳ2
:
(1)
st
F is the area under the fluorescence emission curve; A is
the respective absorbance value at the excitation wave-
length; and ɳ is the refractive index of the medium solvent.
The spectra of carbazole–formazans (Figs 1 and 2)
exhibited three distinctive absorption bands (A, B, and
C). The first band (A) in the range of 292–304 nm was
observed because of the low π–π* energy transfer of the
phenyl group. The second band (B) was shown at 315- to
388-nm range, which corresponded to π–π* electronic
transitions of –N═N– group in the molecule.
The N–H signal of formazan in the NMR spectrum is
indicative in evaluating the structure. When N–H signals
of carbazole–formazan dyes were examined in the 1H-
NMR spectrum and the positions of their signals were
compared, D-A structured compounds (5A–C) exhibited
sharp NH signal in the upfield region at δ 8.68–8.84 ppm;
The third broad band that was observed at 478–547 nm
was characteristic of the formazan structure due to π–π*
and n–π* electronic transitions in formazan skeleton.
In this study, carbazole and formazan moieties were
chosen as an electron-donor group and an electron
acceptor group, respectively. Also, benzene ring was used
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Discovery of novel D-A and D-π-A structured carbazole based formazan dyes:
Synthesis, Characterization and Spectroscopic Studies
Scheme 1. The formation mechanism of formazans.
as a π-conjugated bridge for D-π-A compounds. On the
other hand, p-methyl and p-nitro aniline derivatives were
used for the synthesis of carbazole–formazans in order to
observe the substituent effect.
upon formazan molecule increased conjugation and the
photosensitization, and it also caused a bathochromic
effect upon emission wavelength for D-A 5C dye in
chloroform and for D-π-A 6C dye in acetonitrile when
compared with 5A and 6A. On the other hand, the
electron-donor methyl groups decreased the conjugation
When the UV–vis absorption spectra of the synthesized
carbazole–formazan derivatives were compared, it was
seen that all derivatives gave maximum absorption in the
lowest-polarity solvent toluene, because the polar solvents
stabilize the π* bond and increase the wavelength by
reducing the energy at the n–π* transition. It was
determined that absorption maxima of D-π-A derivatives
were redshifted in comparison with D-A derivatives
because of the increase of π–π* transitions and decrease
of energy.
While the D-A compounds showed excitation maxima
between 414 and 441 nm and emission maxima in the
477- and 533-nm range, D-π-A compounds showed
excitation maxima between 371 and 445 nm and emission
maxima between 466 and 553 nm (Figs 3 and 4). In
comparison with D-A and D-π-A carbazole–formazans,
6A–C dyes, which were D-π-A structured compounds,
showed bathochromic shift for emission maxima in more
polar acetonitrile media, and for 5A–C dyes, a redshift
was shown for fluorescence band in chloroform that is the
less polar solvent used in this study. This might be due to
the formation of π*–π transitions by increasing π-bonds in
the D-π-A derivatives. Owing to increased conjugation at
the p-position by the electron-withdrawing nitro group, 5C
dye gave the highest emission wavelength at 533 nm in
chloroform solution and 6C dye gave the highest emission
wavelength value at 553 nm in acetonitrile solution.
Therefore, the substitution of electron acceptor nitro group
and photosensitization, and they also caused
a
hypsochromic effect upon λmax values for D-A 5B dye
in chloroform and for D-π-A 6B dye in acetonitrile in
comparison with 5A and 6A.
The Stokes shift values were calculated for all
derivatives, and the highest values were obtained for
electron acceptor nitro group substituted 5C compound at
115 nm and for 6C compound at 155 nm, in comparison
with the values of methyl group substituted compounds
5B and 6B as electron acceptor. Intramolecular charge
transfer increased for D-π-A carbazole–formazan dyes
owing to π-conjugated bridge, and the highest Stokes
shift was observed for 6C dye. The Stokes shift values
were higher in chloroform for D-A derivatives and in
acetonitrile for D-π-A derivatives.
As shown in Table 1, the highest fluorescence quantum
yield values were obtained in toluene. Because of the
decrease in the polarity of media, some interactions can
be related and the quantum yield can increase.
EXPERIMENTAL
Reagents and apparatus.
All melting points were
measured in sealed tubes using an electrothermal digital
melting point apparatus (Gallenkamp). Fourier transform
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C. Gundogdu Hizliates
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Table 1
Absorption and fluorescence emission and excitation data for D-A and D-π-A structured carbazole–formazan compounds (λ, nm and ε, L molꢀ1 cmꢀ1),
Stokes shifts, Δλ (nm), singlet energy, Es (cal molꢀ1), and fluorescence quantum yield, ɸ, in solutions
ab
max
em
max
ex
λ
max
Type
D-A
Compound
Solvent
λ
ε
Es
λ
Δλ
ɸ
5A
Chloroform
485
315
293
499
315
294
495
318
295
485
340
292
500
331
293
491
342
294
478
325
293
500
328
293
494
327
294
519
302
543
304
535
304
537
278
543
292
520
295
504
388
297
547
382
301
532
388
301
32,100
72,900
77,100
10,900
25,500
32,400
16,800
38,900
42,200
78,300
100,700
121,400
8400
55,900
84,200
27,400
174,900
209,700
19,700
31,500
36,000
10,500
22,000
37,700
13,000
21,900
28,000
25,800
109,100
16,400
66,600
21,600
96,800
8500
5874
9048
9744
5717
9048
9694
5758
8976
9677
5870
8382
9760
5700
8610
9726
5804
8333
9710
5962
8769
9727
5706
8702
9727
5775
8728
9710
5491
9437
5249
9375
5327
9375
5307
9927
5253
9760
5481
9677
5655
7345
9596
5210
7471
9484
5362
7355
9484
524
482
523
515
485
505
533
477
513
428
441
439
426
424
425
418
420
414
96
0.0495
Toluene
Acetonitrile
Chloroform
Toluene
41
84
0.1585
0.0914
0.0121
0.2674
0.0607
0.0206
0.0853
0.0417
5B
89
61
Acetonitrile
Chloroform
Toluene
80
5C
115
57
Acetonitrile
99
D-π-A
6A
6B
6C
Chloroform
Toluene
471
502
504
468
466
501
521
380
445
371
375
391
380
385
91
57
0.0385
0.0503
0.0146
0.1616
0.2112
0.1197
0.1103
Acetonitrile
Chloroform
Toluene
133
93
218,300
7100
85,600
8900
75
Acetonitrile
Chloroform
121
92
95,900
44,900
74,200
127,800
24,400
41,000
72,500
33,000
53,600
92,200
Toluene
490
553
410
398
80
0.1124
0.0454
Acetonitrile
155
infrared spectroscopy analysis was studied with
PerkinElmer Spectrum BX-II Model FTIR
spectral data were measured by using a Shimadzu 164
UV-1601 spectrophotometer (Shimadzu Corp., Kyoto,
Japan), and fluorescence measurements were recorded
with Varian-Cary Eclipse Fluorescence spectrofluorome-
ter. Analytical and preparative thin-layer chromatogra-
phies were carried out using silica gel 60 HF-254
(Merck, Kenilworth, NJ). Column chromatography was
carried out by using 70–230 mesh silica gels (0.063–
0.2 mm, Merck).
spectrophotometer. NMR spectra were recorded and
obtained on Varian AS-400 NMR (Varian, Inc., Palo
1
Alto, CA) at 400 MHz for H-NMR and 100 MHz for
13C-NMR.
Mass spectra were determined on the electron impact
mode by direct insertion at 70 eV with a Micromass UK
Platform II LC–MS spectrometer. The absorption
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DOI 10.1002/jhet

Month 2019
Discovery of novel D-A and D-π-A structured carbazole based formazan dyes:
Synthesis, Characterization and Spectroscopic Studies
Figure 1. The absorption spectra of D-A structured carbazole–formazan dyes (5A–C) in (a) chloroform, (b) toluene, and (c) acetonitrile. [Color figure can
be viewed at wileyonlinelibrary.com]
Reagent and conditions.
(i) Phenylhydrazine,
(m, 2H, ArH), 7.36–7.38 (dd, 1H, ArH, J = 8.0 and
1.6 Hz), 7.54–7.61 (m, 3H, ArH), 7.71–7.81 (m, 3H,
ArH), 7.96 (s, 1H, CH=N). 13C-NMR (CDCl3
400 MHz δ (ppm)): 145.2 (C═N), 142.6 (NHC), 142.3,
141.9, 135.3, 130.0, 129.2 (2C), 127.8, 126.4, 124.8,
123.6, 123.2, 120.6, 120.2, 114.5 (2C), 109.2, 109.2,
29.3 (NCH3).
methanol, and acetic acid, reflux, 6 h. (ii) N,N-Dimethyl
formamide, pyridine, aniline, HCl, NaNO2, ꢀ5°C.
General procedure of synthesis of carbazole hydrazone
derivatives.
Carbazole aldehydes 1 and 2 (5 mmol)
synthesized according to literature [39,40] were dissolved
in methanol (50 mL) and acetic acid (1 mL), and then
phenylhydrazine (5 mmol) was added with constant
stirring at pH 5–6 within 30 min. The reaction mixture
was refluxed for 5 h, and resulting carbazole hydrazone
compound 9-methyl-3-((2-phenylhydrazono)methyl)-9H-
carbazole (3) and 9-(4-((2-phenylhydrazono)methyl)
phenyl)-9H-carbazole (4) were filtered and recrystallized
from methanol [41,42].
9-(4-((2-Phenylhydrazono)methyl)phenyl)-9H-carbazole
(4). Yellow solid; yield: 0.34 g (48%); mp: 185°C; IR
(KBr, cmꢀ1) ν: 3314 (NH), 1599 (C═N), 1506 (N–N),
1
1360 (C–N). H-NMR (CDCl3, 400 MHz δ (ppm)): 6.94
(t, 1H, ArH, J = 7.2 Hz), 7.16 (d, 2H, ArH, J = 7.6 Hz),
7.32–7.35 (m, 4H, ArH), 7.45–7.47 (m, 5H, ArH and
NH), 7.57–7.59 (dd, 2H, ArH, J = 1.6 and 4.8 Hz), 7.68
(s, 1H, N═CH), 7.84–7.87 (dd, 2H, ArH, J = 2.0 and
6.8 Hz), 8.18–8.20 (d, 2H, ArH, J = 7.6 Hz). 13C-NMR
(CDCl3, 400 MHz δ (ppm)): 145.4 (C═N), 142.5 (NHC),
140.6 (2C), 137.2, 134.2, 129.4 (2C), 129.2 (2C), 126.4
(2C), 124.7, 123.3 (2C), 120.7 (2C), 120.4 (2C), 114.5
(2C), 113.8 (2C), 110.0 (2C).
9-Methyl-3-((2-phenylhydrazono)methyl)-9H-carbazole
(3). Yellow solid; yield: 1.29 g (90%); mp: 168°C; IR
(KBr, cmꢀ1) ν: 3442 (NH), 1597 (C═N), 1476 (N═N),
1364 (C–N). 1H-NMR (CDCl3, 400 MHz δ (ppm)):
3.89 (s, 3H, CH3), 7.02–7.06 (td, 1H, ArH, J = 8.6
and 1.2 Hz), 7.07–7.19 (m, 3H, ArH, NH), 7.21–7.28
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C. Gundogdu Hizliates
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Figure 2. The absorption spectra of D-π-A structured carbazole–formazan dyes (6A–C) in (a) chloroform, (b) toluene, and (c) acetonitrile. [Color figure
can be viewed at wileyonlinelibrary.com]
General procedure of synthesis of D-A and D-π-A
carbazole–formazan derivatives.
9H-carbazol-3-yl)-1,5-diphenylformazan
(5A),
5-(4-
The
carbazole
methylphenyl)-3-(9-methyl-9H-carbazol-3-yl)-1-phenylfor
mazan (5B), 5-(4-nitrophenyl)-3-(9-methyl-9H-carbazol-3-
yl)-1-phenylformazan (5C), and D-π-A carbazole–
formazan derivatives such as 3-(4-(9H-carbazol-9-yl)
phenyl)-1,5-diphenylformazan (6A), 5-(4-methylphenyl)-
3-(4-(9H-carbazol-9-yl)phenyl)-1-phenylformazan (6B),
and 5-(4-nitrophenyl)-3-(4-(9H-carbazol-9-yl)phenyl)-1-
phenylformazan (6C).
hydrazones 3 and 4 (5 mmol) in N,N-dimethyl formamide
(50 mL) were added to pyridine (25 mL), which were
used for basic pH. In another flask, benzenediazonium
chloride solution was prepared using aniline (5 mmol),
concentrated HCl (5 mL), and sodium nitrite (5 mmol)
at ꢀ5°C. This solution was added to the carbazole
hydrazone 3 and/or 4 solution dropwise with constant
stirring to form carbazole-based formazans. The final
solution was stirred for 2 h at the same temperature, and
then 50-mL cold water was added to this mixture, and
the solid obtained was filtered [41–43]. All the other
formazans were synthesized by the same way. All the
compounds synthesized were chromatographed with ethyl
acetate-hexane (1:5) solvent mixture using silica gel for
purification. Organic solvents were evaporated to obtain
D-A carbazole–formazan derivatives such as 3-(9-methyl-
3-(9-Methyl-9H-carbazol-3-yl)-1,5-diphenylformazan
(5A). Cherry-red solid; yield: 0.40 g (50%); mp: 195°C;
IR (KBr, cmꢀ1) ν: 3423 (NH), 1595 (C═N), 1492 (N═N),
1
1322 (C–N). H-NMR (CDCl3, 400 MHz, δ (ppm)): 3.75
(s, 3H, –NCH3), 7.16–7.22 (m, 4H, ArH), 7.30–7.34 (t,
2H, ArH, J = 8.0 Hz), 7.30–7.42 (m, 5H, ArH), 7.62–
7.64 (d, 4H, ArH, J = 8.4 Hz,), 8.10–8.12 (d, 1H, ArH,
J = 8.0 Hz), 8.18–8.20 (d, 1H, ArH, J = 8.8 Hz), 8.73 (s,
1H, NH). 13C-NMR (CDCl3, 400 MHz, δ (ppm)): 155.0
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

Month 2019
Discovery of novel D-A and D-π-A structured carbazole based formazan dyes:
Synthesis, Characterization and Spectroscopic Studies
Figure 3. Emission and excitation spectra of D-A structured carbazole–formazan dyes (5A–C) in (a) chloroform, (b) toluene, and (c) acetonitrile. [Color
figure can be viewed at wileyonlinelibrary.com]
(C═N), 153.1 (N═N–C), 145.4 (NHC), 142.4, 141.9,
129.2 (3C), 129.2, 127.7, 126.8, 126.4, 126.2, 124.7
(2C), 123.4, 123.2, 122.2 (2C), 120.7, 120.4, 114.5 (2C),
109.4, 109.4, 29.3 (NCH3). HRMS (ESI+): analytically
calculated for (C26H21N5) 402.1719, found 402.1734.
(C═N), 150.5 (N═N–C), 145.7 (NHC), 142.5, 141.9,
132.5, 129.6 (2C), 128.9 (2C), 127.7, 126.9, 126.5,
126.2, 124.6, 123.4, 123.2, 122.3 (2C), 120.8, 120.4,
114.6 (2C), 109.4, 109.4, 29.3 (NCH3), 21.3 (Ar-CH3).
HRMS (ESI+): analytically calculated for (C27H23N5)
418.2032, found 418.2050.
5-(4-Methylphenyl)-3-(9-methyl-9H-carbazol-3-yl)-1-
phenylformazan (5B). Dark pink-red solid; yield: 0.23 g
5-(4-Nitrophenyl)-3-(9-methyl-9H-carbazol-3-yl)-1-
(32%); mp: 142°C; IR (KBr, cmꢀ1) ν: 3425 (NH), 1595
(C═N), 1494 (N═N), 1325 (C–N). 1H-NMR (CDCl3,
400 MHz, δ (ppm)): 2.46 (s, 3H, CH3), 3.87 (s, 3H,
NCH3), 7.18–7.21 (t, 1H, ArH, J = 7.6 Hz), 7.26–7.34
(m, 4H, ArH), 7.41–7.53 (m, 5H, ArH), 7.61–7.63 (d,
2H, ArH, J = 7.6 Hz), 7.75–7.77 (d, 2H, ArH,
J = 8.0 Hz), 8.21–8.23 (d, 1H, ArH, J = 7.6 Hz), 8.28–
8.31 (dd, 1H, ArH, J = 6.8 and 1.6 Hz), 8.84 (s, 1H,
NH). 13C-NMR (CDCl3, 400 MHz, δ (ppm)): 155.0
phenylformazan (5C).
Dark red solid; yield: 0.56 g
(75%); mp: 186°C; IR (KBr, cmꢀ1) ν: 3422 (NH), 1590
(C═N), 1590–1368 (NO2), 1518 (N═N), 1324 (C–N).
1H-NMR (CDCl3, 400 MHz, δ (ppm)): 3.77 (s, 3H,
NCH3), 7.23–7.38 (m, 6H, ArH), 7.46–7.55 (m, 4H,
ArH), 7.82–7.87 (m, 2H, ArH), 8.04–8.23 (m, 4H, ArH),
8.68 (s, 1H, NH). 13C-NMR (CDCl3, 400 MHz, δ
(ppm)): 155.4 (C═N), 150.5 (N═N–C), 145.5 (NHC),
143.3, 142.5, 141.9, 129.4 (2C), 127.7, 126.8, 126.4,
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C. Gundogdu Hizliates
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Figure 4. Emission and excitation spectra of D-π-A structured carbazole–formazan dyes (6A–C) in (a) chloroform, (b) toluene, and (c) acetonitrile.
[Color figure can be viewed at wileyonlinelibrary.com]
126.2, 124.7, 124.6 (2C), 123.4, 123.2, 122.3 (2C), 120.7,
120.5, 114.5 (2C), 109.6, 109.4, 29.4 (NCH3). HRMS (ESI
+): analytically calculated for (C26H20N6O2) 449.1726,
found 449.1771.
136.6, 129.5 (4C), 127.7 (2C), 127.2 (2C), 126.9 (2C),
126.0 (2C), 123.4 (2C), 120.3 (2C), 119.9 (2C), 118.9
(4C), 109.9 (2C). HRMS (ESI+): analytically calculated
for (C31H23N5) 466.2032, found 466.2032.
3-(4-(9H-Carbazol-9-yl)phenyl)-1,5-diphenylformazan
(6A). Red-brown solid; yield: 0.52 g (80%); mp: 212°C.
IR (KBr, cmꢀ1) ν: 3422 (NH), 1598 (C═N), 1450 (N═N),
5-(4-Methylphenyl)-3-(4-(9H-carbazol-9-yl)phenyl)-1-
phenylformazan (6B).
Dark purplish red solid; yield:
0.44 g (66%); mp: 225°C. IR (KBr, cmꢀ1) ν: 3422 (NH),
1598 (C═N), 1450 (N═N), 1233 (C–N). 1H-NMR
(CDCl3, 400 MHz, δ (ppm)): 2.46 (s, 3H, CH3), 7.22–7.24
(m, 2H, ArH), 7.31–7.35 (m, 4H, ArH), 7.44–7.49 (m, 4H,
ArH), 7.53–7.55 (d, 2H, ArH, J = 8.0 Hz), 7.64–7.67 (m,
3H, ArH), 7.75–7.77 (d, 2H, ArH, J = 8.0 Hz), 8.18–8.20
(d, 2H, ArH, J = 8.0 Hz), 8.38–8.40 (d, 2H, ArH,
J = 8.0 Hz), 15.23 (s, 1H, NH). 13C-NMR (CDCl3,
1226 (C–N). 1H-NMR (CDCl3, 400 MHz, δ (ppm)): 7.31–
7.35 (m, 4H, ArH), 7.43–7.54 (m, 8H, ArH and NH), 7.65–
7.67 (d, 2H, ArH, J = 8.4 Hz), 7.75–7.77 (dd, 4H, ArH,
J = 1.2 and 7.2 Hz), 8.18–8.20 (d, 2H, ArH, J = 8.0 Hz),
8.37–8.40 (dd, 2H, ArH, J = 1.6 and 5.2 Hz), 15.52(s,
1H, NH). 13C-NMR (CDCl3, 400 MHz, δ (ppm)): 153.1
(C═N), 147.8 (N═N–C and NHC), 140.8 (2C), 136.9,
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DOI 10.1002/jhet

Month 2019
Discovery of novel D-A and D-π-A structured carbazole based formazan dyes:
Synthesis, Characterization and Spectroscopic Studies
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400 MHz, δ (ppm)): 155.2 (C═N), 150.5 (N═N–C), 145.4
(NHC), 140.3 (2C), 137.2, 132.4, 131.8, 129.3 (2C), 128.9
(2C), 127.0 (2C), 126.2 (2C), 124.7, 123.6 (2C), 122.3
(2C), 120.8 (2C), 120.4 (2C), 114.5 (2C), 113.9 (2C),
110.0 (2C), 21.3 (ArCH3). HRMS (ESI+): analytically
calculated for (C32H25N5) 480.2188, found 480.2188.
195.
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5-(4-Nitrophenyl)-3-(4-(9H-carbazol-9-yl)phenyl)-1-
phenylformazan (6C).
Red-dark purple solid; yield:
0.60 g (85%); mp: 198°C. IR (KBr, cmꢀ1) ν: 3426 (NH),
1596 (C═N), 1449 (N═N), 1226 (C–N). 1H-NMR
(CDCl3, 400 MHz, δ (ppm)): 7.30–7.32 (m, 3H, ArH),
7.43–7.45 (m, 2H, ArH), 7.52–7.54 (d, 4H, ArH,
J = 8.8 Hz), 7.60–7.62 (m, 2H, ArH), 7.69–7.71 (d, 2H,
ArH, J = 8.4 Hz), 7.80–8.02 (m, 2H, ArH), 8.16–8.18 (d,
2H, ArH, J = 8.0 Hz), 8.28–8.31 (d, 2H, ArH,
J = 8.4 Hz), 8.36–8.38 (d, 2H, ArH, J = 8.4 Hz), 15.52
(s, 1H, NH). 13C-NMR (CDCl3, 400 MHz, δ (ppm)):
156.0 (C═N), 150.5 (N═N–C), 145.8 (NHC), 140.6 (2C),
140.5, 137.2, 131.7, 130.0 (2C), 126.5 (2C), 126.2 (2C),
125.2 (2C), 124.8, 123.6 (2C), 121.0 (2C), 121.0 (2C),
117.4 (2C), 114.9 (2C), 113.9 (2C), 109.8 (2C). HRMS
(ESI+): analytically calculated for (C31H22N6O2)
511.1882, found 511.1903.
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CONCLUSION
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With this study, first, carbazole-based new carbazole–
formazan compounds with D-A/D-π-A structures were
according to the literature. For this aim, carbazole–
formazan dyes were synthesized and characterized, and
then their spectrophotometric and spectrofluorimetric
properties were studied for 1 × 10ꢀ5M in the different
polarity solvents. According to Stokes’s shift calculation
of the compounds, D-π-A structured carbazole–formazan
dye 6C was shown the highest value owing to presence
of electron acceptor nitro group at the para position and
the π-conjugated bridge.
Considering the photophysical results of the newly
synthesized carbazole–formazan dyes, D-π-A structured
derivatives are expected to be used in dye industry that
develops every day.
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Acknowledgment.
I
acknowledge the Scientific and
Technological Research Council of Turkey (Türkiye Bilimsel ve
Teknolojik Arastirma Kurumu) for financial support (project
number is 215Z485).
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C. Gundogdu Hizliates
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SUPPORTING INFORMATION
Additional supporting information may be found online
in the Supporting Information section at the end of the
article.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet