Structural, absorption, and molecular properties of o,o'-dihydroxyazo resorcinol dyes bearing an acryloyloxy group

Article abstract of DOI:10.1016/j.molstruc.2017.07.099

To the best of our knowledge, this is the first study reporting the synthesis and characterization of o,o′-dihydroxyazo dyes bearing an acryloyl group. The o,o′-dihydroxyazo dyes were synthesized through coupling of resorcinol with the diazonium salts of 2-amino-4-methylphenol, 2-aminophenol, 2-amino-4-chlorophenol, and 2-amino-4-nitrophenol. Their acryloyl derivatives were synthesized using metallic sodium and acryloyl chloride under an inert atmosphere. Characterization of the compounds was conducted using infrared (IR), ultraviolet–visible (UV–vis), proton nuclear magnetic resonance (¹H NMR), and carbon nuclear magnetic resonance (¹³C NMR) spectroscopic methods. The tautomerism of the synthesized compounds' was also evaluated. The results were compared with theoretical results obtained by density functional theory (DFT). The DFT calculations were performed to obtain ground-state optimized geometries and calculate the relevant electronic and chemical reactivity parameters. Furthermore, possible tautomers deduced from the UV–vis spectra were investigated using theoretical calculations. Both the IR and NMR spectral data showed that azo tautomers predominate in the solid state and DMSO solvent. The effects of pH, solvent, and substituent on the predominant tautomers were further investigated through UV–vis spectroscopy. The results indicate that hydrazone tautomers were dominant at pH 12 in dimethylformamide (DMF), whereas azo tautomers were dominant at pH 2 in EtOH or CHCl₃.

Full text of DOI:10.1016/j.molstruc.2017.07.099

Accepted Manuscript
Structural, absorption, and molecular properties of o,o'-dihydroxyazo resorcinol dyes
bearing an acryloyloxy group
Sevil Özkınalı, M. Serdar Çavuş, Abdullah Ceylan, Mahmut Gür
PII:
S0022-2860(17)31043-8
10.1016/j.molstruc.2017.07.099
MOLSTR 24126
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 27 March 2017
Revised Date: 27 July 2017
Accepted Date: 28 July 2017
Please cite this article as: S. Özkınalı, M.S. Çavuş, A. Ceylan, M. Gür, Structural, absorption, and
molecular properties of o,o'-dihydroxyazo resorcinol dyes bearing an acryloyloxy group, Journal of
Molecular Structure (2017), doi: 10.1016/j.molstruc.2017.07.099.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

1
ACCEPTED MANUSCRIPT
Structural, Absorption, and Molecular Properties of o,o'-Dihydroxyazo Resorcinol
Dyes Bearing an Acryloyloxy Group
Sevil Özkınalı1*, M. Serdar Çavuş2, Abdullah Ceylan1, Mahmut Gür3
1Department of Chemistry, Faculty of Science and Literature, Hitit University, Çorum,
Turkey
2Biomedical Engineering Department, Faculty of Engineering and Architecture,
Kastamonu University, Kastamonu, 37100, Turkey
3Department of Forest Industrial Engineering, Faculty of Forestry, Kastamonu
University, Kastamonu, Turkey
*Corresponding Author.
Tel: +903642267000-1636;
Fax: +903642277005
e-mail: sevilozkinali@hitit.edu.tr
Abstract
To the best of our knowledge, this is the first study reporting the synthesis and
characterization of o,o′-dihydroxyazo dyes bearing an acryloyl group. The o,o′-
dihydroxyazo dyes were synthesized through coupling of resorcinol with the diazonium
salts of 2-amino-4-methylphenol, 2-aminophenol, 2-amino-4-chlorophenol, and 2-
amino-4-nitrophenol. Their acryloyl derivatives were synthesized using metallic sodium
and acryloyl chloride under an inert atmosphere. Characterization of the compounds
was conducted using infrared (IR), ultraviolet–visible (UV–Vis), proton nuclear
magnetic resonance (1H NMR), and carbon nuclear magnetic resonance (13C NMR)
spectroscopic methods. The tautomerism of the synthesized compounds’ was also

2
ACCEPTED MANUSCRIPT
evaluated. The results were compared with theoretical results obtained by density
functional theory (DFT). The DFT calculations were performed to obtain ground-state
optimized geometries and calculate the relevant electronic and chemical reactivity
parameters. Furthermore, possible tautomers deduced from the UV–Vis spectra were
investigated using theoretical calculations. Both the IR and NMR spectral data showed
that azo tautomers predominate in the solid state and DMSO solvent. The effects of pH,
solvent, and substituent on the predominant tautomers were further investigated through
UV–Vis spectroscopy. The results indicate that hydrazone tautomers were dominant at
pH 12 in dimethylformamide (DMF), whereas azo tautomers were dominant at pH 2 in
EtOH or CHCl3.
Keywords: o,o′-dihydroxyazo dyes, DFT, azo–hydrazone, tautomerism, resorcinol
Graphical Abstract
Highlights
° Novel o,o'-dihydroxyazo dyes containing an acryloyl moiety were synthesized
and characterized.
° The azo–hydrazone tautomerism was investigated using UV–Vis spectroscopy
and DFT calculations.
° These compounds are useful for synthesizing novel organic dyes.

4
ACCEPTED MANUSCRIPT
1. Introduction
Azo dyes have been extensively used in various fields such as textiles, paper, leather,
gasoline, food, additives, cosmetics, analytical chemistry, photography, therapeutic
agents, and drug delivery [1–5]. Such dyes are pertinent to photography, xerography,
laser printing, and write once-read many times memory systems due to their fastness
properties, low production costs, and useful applications [1,6,7]. Azo dyes are also
pertinent to the medical and pharmaceutical industries owing to their antiseptic,
antibacterial, antitumor, antioxidant, antineoplastic, and antidiabetic properties [2,8,9].
In particular, azo resorcinol dyes have been studied for their significant antioxidant and
antimicrobial activities [10]. Resistance of bacteria to modern antibiotics has recently
become a clinical crisis. Medicinal chemists are developing new antibiotics and
synthetic antimicrobial agents to conquer drug-resistant strains [10]. For example, 4-n-
butyl resorcinol has been used in skin creams and lotions due to its antimicrobial and
bleaching action efficacy [11,12]. Moreover, due to their phenolic moiety and hydroxyl
groups, azo resorcinol dyes are commonly used as colorimetric reagents for metal ions
[13–15].
Azo–hydrazone tautomerism occurs within azo compounds bearing, at a minimum, a
protic group in conjugation with the azo groups [16]. In particular, o,o'-dihydroxyazo
dyes can exhibit azo–hydrazone tautomerism. The tautomeric equilibrium primarily
depends on structural factors, solvent polarity, and pH of the medium [17–18].
Kishimoto et al. [19] demonstrated that the azo group (-N=N-) is an electron-accepting
group; thus, electron-donating groups stabilize the azo tautomer. Hydrazones bearing
electron-acceptor groups such as imino (-NH-N=) are stabilized via electron-donor
groups. [19]. Dakiky et al. [20] noted solvent effects on tautomerism. High-polarity

5
ACCEPTED MANUSCRIPT
solvents favor hydrazone tautomers, whereas low-polarity solvents prefer azo tautomers
[20]. Pertinent to tautomeric characterization is the fact that the absorption bands of
hydrazo tautomers are at longer wavelengths relative to the corresponding azo
tautomers [21]. Azo dye tautomerism is pertinent to optical, technical, and
environmental applications [22–23]. Numerous recent studies have investigated the
molecular properties of azo dyes using density functional theory (DFT) calculations
[24–30].
The aim of this study was to analyze the tautomers of eight novel azo resorcinol
compounds that belong to the class of o,o'-dihydroxyazo dyes. The compounds were
characterized using spectroscopy and DFT calculations to further understand azo–
hydrazone tautomerism. The experimental results were validated using theoretical
calculations. Although resorcinol dye synthesis and spectroscopic properties have been
previously reported, no study has examined o,o′-dihydroxyazo resorcinol dyes bearing
an acryloyl moiety nor have they implemented DFT [12,20]. DFT calculations illustrate
the extent to which experimental results match theoretical predictions.
1
The azo derivatives reported herein were characterized by IR, UV–Vis, H NMR, and
13C NMR spectroscopies. DFT calculations with different basis sets were used to
evaluate the structural and chemical properties of the compounds. Tautomerization was
examined using experimental and theoretical UV–Vis studies. The molecular geometry,
optimized parameters, and UV–Vis absorption values were calculated, and the
calculated spectral data were compared with the experimental results.
2. Experimental

6
ACCEPTED MANUSCRIPT
Chemicals and solvents were purchased from Aldrich (USA) and Merck Chemical
Company (Germany) and used without further purification. The IR spectra were
obtained using a Thermo Scientific Class 1 Laser Product FTIR (USA)
spectrophotometer in the ATR mode. The absorption spectra in chloroform, ethanol,
and DMF were obtained using a Thermo Scientific Genesys 10S UV–VIS (UK)
1
13
spectrophotometer. Elemental, H NMR, and C NMR analyses were conducted in the
Instrumental Analysis Laboratory at METU Research Center. Nuclear magnetic
resonance spectra were obtained on a Bruker (Germany) AC 400 Fourier Transform
Spectrometer operating at 400 MHz in deuterated dimethylsulfoxide (DMSO-d6) using
tetramethylsilane (TMS). Substance purity and reaction progress were monitored by
TLC using TLC aluminum sheets with silica gel 60 F254 (Merck). Preparative TLC
chromatography was performed on 20 × 20 cm glass plates covered by silica gel 60
GF254 (Merck) or Al2O3 type G (Fluka (Switzerland)). Column chromatography was
performed using silica gel 60 (Merck).
2.1. General procedure for the synthesis of acryloyl derivatives of azo dyes
First, o,o'-dihydroxyazo dyes were synthesized via a coupling reaction of resorcinol
with diazonium salts of 2-hydroxy-4-methyl phenol, 2-aminophenol, 2-amino-4-choloro
phenol, and 2-amino-4-nitro phenol [31–32]. Then, for the synthesis of acryloyl
derivatives of o,o'-dihydroxyazo dyes, reaction of these compounds with metallic
sodium and acryloyl chloride was conducted under a N2 atmosphere at a 1:1 molar ratio.
Figure 1 illustrates the general synthesis method and the structures of compounds 1–8.
2.1.1. Synthesis of 4-[(E)-(2-hydroxy-5-methylphenyl)diazenyl]benzene-1,3-diol, (1)

7
ACCEPTED MANUSCRIPT
A cold solution of NaNO2 (0.69 g; 0.01 mol) was added dropwise into a mixture of 2-
amino-4-methylphenol (1.23 g; 0.01 mol) dissolved in concentrated hydrochloric acid
and water (20 mL) at 0–5°C. The solution was then stirred for 30 min to complete the
diazotation. Diazonium salt was added dropwise into an ice-cold solution of 1,3-
benzenediol (1.10 g; 0.01 mol) with a mixture of NaAc (7.5 g, 0.09 mol) and DMF (20
mL) at 0–5°C. After stirring for 3 h at 0–5°C, the solution acidity was adjusted to pH 4–
5 using 1 mol.L-1 HCl. The synthesized compounds were precipitated by maintaining a
temperature range of 0–5°C. The reaction solution was then filtered and washed with
water and purified from ethanol/water. Melting Point (m.p.) 153-155 °C. Yield 78 %. IR
(cm-1): 3277 (OH), 3067, 2976, 2916 (C-H), 1621 (>C=C<), 1178 (Ar-O) 1H NMR (500
MHz, d6-DMSO, ppm): 12.81 (s,1H), 11.08 (s,1H), 10.47 (s, 1H), 7.68 (d, 1H, J =7.00),
7.55 (s, 1H), 7.12 (d, 1H, J=5.50 Hz), 6.92 (d, 1H, J=7.0 Hz), 6.47 (d, 1H, J=5.50 Hz),
13
6.37 (s, 1H), 2.27 (s, 3H) C NMR (125 MHz, d6-DMSO, ppm) 162.9, 157.3, 151.4,
137.03, 132.7, 132.4, 128.9, 128.5, 121.4, 117.8, 109.4, 103.5, 20.5. Analysis by
calculation for C13H12N2O3: C, 63.93; H, 4.95; N, 11.47 %. Found: C, 62.25; H, 5.14; N,
10.84%
2.1.2. Synthesis of 4-[(E)-(2-hydroxyphenyl)diazenyl]benzene-1,3-diol, (2)
The same procedure was used for the synthesis of compound 1 and compound 2. The
product was recrystallized from ethanol/water, yielding a product with a melting point
(m.p.) in the range of 136–138°C. Yield 78 %. IR (cm-1): 3488, 3199 (OH), 3095 (C-H),
1623 (>C=C<), 1167 (Ar-O) 1H NMR (500 MHz, d6-DMSO, ppm): 12.68 (s,1H), 11.42
(s,1H), 10.49 (s, 1H), 7.74 (d, 1H, J =5.50), 7.69 (d, 1H, J=6.50 Hz ), 7.30 (t, 1H,
J=5.50 Hz), 7.03 (d, 1H, J=7.0 Hz), 6.96 (t, 1H, J=6.50 Hz), 6.48 (d, 1H, J= 7.0 Hz),
13
6.38 (s, 1H) C NMR (125 MHz, d6-DMSO, ppm) 163.1, 157.4, 153.5, 137.5, 132.4,

8
ACCEPTED MANUSCRIPT
131.9, 128.0, 122.1, 120.1, 118.0, 109.5, 103.5 Analysis by calculation for C12H10N2O3:
C, 62.60; H, 4.38; N, 12.17 %. Found: C, 61.32; H, 4.53; N, 10.54%
2.1.3. Synthesis of 4-[(E)-(5-chloro-2-hydroxyphenyl)diazenyl]benzene-1,3-diol, (3)
The same procedure was used for the synthesis of compound 1 and compound 3. The
product was recrystallized from ethanol/water to give an orange dye with a m.p. in the
range of 190–192°C. Yield 78 %. IR (cm-1): 3447, 3184 (OH), 3080 (C-H), 1627
(>C=C<), 1169 (Ar-O), 980 (C-Cl) 1H NMR (500 MHz, d6-DMSO, ppm): 12.65 (s,1H),
11.18 (s,1H), 10.61 (s, 1H), 7.75 (s, 1H), 7.72 (d, 1H, J=7.50 Hz), 7.31 (d, 1H, J=8.20
13
Hz), 7.05 (d, 1H, J= 7.50 Hz), 6.49 (d,1H, J=8.20 Hz), 6,37 (s, 1H) C NMR (125
MHz, d6-DMSO, ppm) 163.8, 157.8, 152.7, 138.3, 132.8, 131.1, 129.0, 124.1, 119.6,
119.3, 109.9, 103.6. Analysis by calculation for C12H9ClN2O3: C, 54.46; H, 3.43; N,
10.58 %. Found: C, 53.25; H, 3.59; N, 10.14%
2.1.4. Synthesis of 4-[(E)-(2-hydroxy-5-nitrophenyl)diazenyl]benzene-1,3-diol, (4)
The same procedure was used for the synthesis of compound 1 and compound 4. The
product was recrystallized from ethanol/water to give a red dye, yielding a product with
a m.p. in the range of 152–156°C. Yield 72 %. IR (cm-1): 3492, 3404 (-OH), 3093 (C-
1
H), 1621 (>C=C<), 1516,1338 (NO2), 1182 (Ar-O) H NMR (500 MHz, d6-DMSO,
ppm): 12.79 (s,1H), 12.36 (s,1H), 10.77 (s, 1H), 8.49 (s, 1H), 8.15 (d, 1H, J=5.00 Hz),
7.76 (d, 1H, J=7.50 Hz), 7.21 (d, 1H, J= 7.50 Hz), 6.51 (d,1H, J=5.00 Hz), 6,38 (s, 1H)
13C NMR (125 MHz, d6-DMSO, ppm) 164.4, 159.6, 158.3, 140.6, 137.0, 132.9, 129.5,
126.4, 118.4, 114.9, 110.2, 103.4 Analysis by calculation for C12H9N3O5: C, 52.37; H,
3.30; N, 15.27 %. Found: C, 53.08; H, 3.73; N, 15.46%

9
ACCEPTED MANUSCRIPT
2.1.5. Synthesis of 3-hydroxy-4-[(E)-(2-hydroxy-5-methylphenyl)diazenyl]phenyl
prop-2-enoat, (5)
4-[(E)-(2-Hydroxy-5-methylphenyl)diazenyl]benzene-1,3-diol (549.0 mg; 2.25 mmol)
and fresh metallic sodium (51.74 mg; 2.25 mmol) in dry THF (20 mL) were mixed and
stirred under a N2 atmosphere for 24 h. Then, acryloyl chloride (0.189 mL; 2.25 mmol)
was added dropwise and stirred into a mixture under a dry nitrogen atmosphere. After
stirring for 4 h, the reaction mixture was filtered and the desired product was
precipitated from the dried THF. The final product was recrystallized from THF/water,
yielding a product with a m.p. in the range of 116–118°C. Yield 58 %. IR (cm-1): 3198
1
(OH), 3072, 2922 (C-H), 1742 (C=O), 1624, 1601 (>C=C<), 1240, 1160 (Ar-O) H
NMR (500 MHz, d6-DMSO, ppm): 12.84 (s, 1H) 11.09 (s, 1H), 7.67 (d, 1H, J=7.0),
7.54 (s, 1H), 7.35-7.16 (m, 1H), 7.10 (d, 1H, J=5.50), 6.92 (d,1H, J=7.0), 6.58-6.50
13
(m,1H), 6.48 (d, 1H, J=5.50), 6.33 (s, 1H), 6.22-6.17 (m, 1H), 2.27 (s, 3H) C NMR
(125 MHz, d6-DMSO, ppm) 164.6, 155.4, 153.8, 152.5, 138.3, 134.7, 134.5, 129.2,
128.5, 127.9, 124.9, 123.7, 118.7, 114.1, 111.4, 21.0 Analysis by calculation for
C16H14N2O4: C, 64.42; H, 4.73; N, 9.39 %. Found: C, 63.79; H, 4.48; N, 9.49%
2.1.6. Synthesis of 3-hydroxy-4-[(E)-(2-hydroxyphenyl)diazenyl]phenyl prop-2-
enoat, (6)
The same procedure was used for the synthesis of compound 5 and compound 6. The
product was then recrystallized from THF/water, yielding a product with a m.p. in the
range of 113–115°C. Yield 72 %. IR (cm-1): 3202 (OH), 3064, 2922, 2853 (C-H), 1740
(C=O), 1615, 1581 (>C=C<), 1241, 1125 (Ar-O) 1H NMR (500 MHz, d6-DMSO, ppm):
12.80 (s, 1H) 11.46 (s, 1H), 7.88 (d, 1H, J=7.5), 7.73 (d, 1H, J=6.5), 7.67 (d, 1H, J=7.5),
7.29 (t, 1H, J=6.5), 7.06 (d, 1H, J=4.0), 6.95 (t, 1H, J=6.5), 6.87-6.85 (m, 1H), 6.49 (d,

10
ACCEPTED MANUSCRIPT
1H, J= 4.0), 6.37 (s,1H), 6.22-6.15 (m, 1H) 13C NMR (125 MHz, d6-DMSO, ppm)
164.5, 162.3, 155.4, 154.3, 138.7, 137.8, 136.0, 132.1, 128.1, 121.8, 120.3, 118.9,
118.8, 109.6, 103.6 Analysis by calculation for C15H12N2O4: C, 63.38; H, 4.25; N, 9.85
%. Found: C, 63.06; H, 4.08; N, 9.13%
2.1.7. Synthesis of 3-hydroxy-4-[(E)-(5-chloro-2-hydroxyphenyl)diazenyl]phenyl
prop-2-enoat, (7)
The same procedure was used for the synthesis of compound 5 and compound 7. The
product was then recrystallized from THF/water, yielding a product with a m.p. in the
range of 180–182°C. Yield 54 %. IR (cm-1): 3082 (-OH), 2970, 2852 (C-H), 1746
(>C=O), 1622, 1595 (>C=C<), 1256, 1158 (Ar-O), 979 (C-Cl) 1H NMR (500 MHz, d6-
DMSO, ppm): 12.65 (s, 1H) 11.18 (s, 1H), 7.75 (s, 1H), 7.71 (d, 1H, J=10.0), 7.58-7.40
(m, 1H), 7.31 (d, 1H, J=10.0), 7.06 (d, 1H, J=10.0), 6.93 (d, 1H, J=10.0), 6.60-6.45 (m,
1H), 6.37 (s, 1H), 6.25-6.16 (m, 1H) 13C NMR (125 MHz, d6-DMSO, ppm) 164.4,
157.3, 152.2, 145.5, 143.2, 137.8, 134.6, 131.5, 127.4, 126.8, 123.6, 118.7, 116.7,
109.3, 102.9 Analysis by calculation for C15H11ClN2O4: C, 56.53; H, 3.48; N, 8.79 %.
Found: C, 56.26; H, 3.40; N, 8.76%
2.1.8. Synthesis of 3-hydroxy-4-[(E)-(2-hydroxy-5-nitrophenyl)diazenyl]phenyl
prop-2-enoat, (8)
The same procedure was used for the synthesis of compound 2 and compound 8. The
product was then recrystallized from THF/water, yielding a product with a m.p. in the
range of 116–118°C. Yield 62 %. IR (cm-1): 3178 (-OH), 3100, 2918, 2853 (C-H), 1749
1
(C=O), 1623, 1578 (>C=C<), 1527, 1343 (NO2), 1211, 1112 (Ar-O) ) H NMR (500
MHz, d6-DMSO, ppm): 13.15 (s, 1H) 11.98 (s, 1H), 8.70 (s, 1H), 8.15-8.12 (m, 1H),

11
ACCEPTED MANUSCRIPT
7.95 (d, 1H, J=7.50), 7.78-7.71 (m, 1H), 7.60 (d, 1H, J=7.50), 6.98-6.78 (m, 1H), 6.57-
6.48 (m,1H), 6.30 (s, 1H), 6.13-6.07 (m, 1H) 13C NMR (125 MHz, d6-DMSO, ppm)
164.9, 159.0, 157.8, 150.9, 146.1, 142.7, 135.1, 133.3, 127.3, 124.9, 117.9, 114.5,
112.0, 109.7, 102.9. Analysis by calculation for C15H11N2O6: C, 54.72; H, 3.37; N,
12.76 %. Found: C, 54.42; H, 3.40; N, 12.05%
2.2. Computational Methods
Structural optimization of compounds was performed by DFT calculations using
suitable basis sets without any geometric constraints. The Kohn–Sham density
functional theory [33–34] was used to calculate the compounds’ ground-state
geometries and excitation energies. Molecular structures of the compounds in the
ground state were optimized using the M06 method (which is a set of four meta-hybrid
GGA DFT functionals) with 3-21G basis set; the B3LYP method (Becke3–Lee–Yang–
Parr hybrid functional) with 6-311++G and 6-311++G(2d,2p) basis sets; and the
PBE1PBE method (which is the generalized-gradient-approximation exchange–
correlation functional of Perdew, Burke, and Ernzerhof) with cc–pvtz basis set in
chloroform, dimethylformamide, and ethanol solvents.
In order to determine the minimum energy level configuration of the compounds,
compound 1 was dihedrally scanned around the N=N bond with a step size of 18° for a
total of 20 steps (Figure 2). The most suitable dihedral angle that gives the minimum
energy level of the compound between the phenyl rings was calculated as 7.74°.
Calculations for geometric optimization of the remaining compounds followed the
aforementioned protocol. In the calculations, the compounds’ minimum molecular

12
ACCEPTED MANUSCRIPT
energies were obtained by the level 6-311++G(2d,2p) basis set using the B3LYP
method. The optimized geometries were used in UV–Vis-based molecular calculations.
The self-consistent reaction field (SCRF) method and the conductor-polarizable
continuum model (CPCM) were used for such calculations. The frontier molecular
orbitals (FMOs) energies were also calculated as per the same methods and basis sets.
FMO energy eigenvalues were used to calculate global chemical reactivity parameters
such as chemical hardness, chemical softness, and electronegativity. Dipole moment
and molecular electrostatic potential (MEP) surfaces of the optimized molecular
structures were examined using the theoretical results. All calculations in the study were
performed using the GAUSSIAN 09 software package program [35].
3. Results and Discussion
3.1. Synthesis
Figure 1 shows the synthetic route toward the azo dyes and previously unreported
acryloyl derivatives. All the compounds were synthesized as described previously [36].
Aromatic amines were effectively diazotized at 0–5°C using sodium nitrite and
hydrochloric acid. Esters were derived satisfactorily by adding acryloyl chloride to the
sodium salts of the resorcinol dyes in an inert atmosphere, and purification was
performed in EtOH. Dye purity was verified using TLC with a chloroform:methanol
(4:1) solvent system. Azo dyes and their acryloyl derivatives were identified through IR,
UV–Vis, 1H NMR, and 13C NMR spectroscopies.
3.2. IR spectral analysis

13
ACCEPTED MANUSCRIPT
Two hydroxyl peaks were determined in the IR spectra of the resorcinol dyes. The first
peak was at 3387–3095 cm–1 for the compounds containing an intramolecular hydrogen
bond between the phenolic and azo groups. The second and narrow peak was observed
at 3540–3489 cm–1, attributable to free hydroxyl groups. The absorption band
corresponding to the free hydroxyl group was not observed in the IR spectra of the
acryloyl derivatives. These observations indicate a successful reaction. On comparing
the spectra of the azo dyes and their acryloyl derivatives, strong carbonyl peaks were
observed in the 1740–1749 cm−1 range (Table 1 and Fig. 3). The peaks between 2970
and 2852 cm–1 were assigned to the –C-H stretching frequency of the ethenyl (–
CH=CH2) moiety of the acryloyl derivatives. The remaining stretching bands at 1623–
1578 cm–1, 1279–1236 cm–1, and 1167–1110 cm–1 were attributed to ethenyl (CH2=CH-
), aromatic (-C=C-), -C(O)-O- and Ar-O-, respectively. After acryloyl derivative
esterification, the stretching frequencies of the–C(O)-O- group appeared as a broader
and stronger peak with Ar-O stretches in the same region. An–NH peak originating
from hydrazone enantiomers, which would appear in the same region of the hydroxyl
peak, was not observed. Azo–hydrazone tautomerization occurs via proton transfer from
the hydroxyl group to the azo group. In the literature, NH peaks are seen in the vicinity
of 3109 cm–1 as a weak peak [37]. Therefore, the absence of –NH peaks indicates that
the compounds are azo tautomers in solid state.
3.3. UV–Vis spectral analysis
UV–Vis spectral data were recorded in various solvents such as CHCl3, EtOH, and
DMF. The effect of pH on the absorption spectra of compounds (1–8) was investigated
in DMF by adjusting the pH to 2 and 12 using 0.1 mol.L-1 HCl and 0.1 mol.L-1 NaOH.
Table 2 shows the UV–Vis absorption bands pertinent to compounds 1–8.

14
ACCEPTED MANUSCRIPT
The absorption maxima (λmax) for compounds 1–8 were measured in ethanol as 395–403
nm and 415–469 nm, in chloroform as 335–401 nm and 423–436 nm, in DMF as 392–
428 nm and 435–529 nm, in DMF at pH 2 as 396–431 nm and 441–511 nm, and in
DMF at pH 12 as 360–450 nm and 495–510 nm. This indicates a high molar
absorptivity attributable to the π→π* and n→π* transitions. Figure 4 shows the UV–
Vis spectrum of compound 7. These results are elaborated and explained next.
The λmax of the dyes and their acryloyl derivatives in DMF with pH 12 showed a
slightly bathochromic shift compared with EtOH and CHCl3. Azo dye 1, bearing an
electron-donor substituent exhibited a bathochromic shift in EtOH. In contrast, azo
compounds 3 and 4, bearing electron-acceptor substituents, exhibited a hypsochromic
shift compared with unsubstituted azo compound 2. Resorcinol azo dyes 1–4 featured a
hypsochromic shift compared to the corresponding acryloyl derivatives (5–8) in all
solvents because of the electron-withdrawing effect of the acryloyl group. As a result of
the observed bathochromic shifts, pH 12 DMF favors the hydrazone tautomers.
Theoretical predictions of the hydrazone tautomers A–E of compounds 1–8 were
undertaken to analyze in detail the tautomeric equilibrium observed in the experimental
UV–Vis data (Figure 5 and Section 3.5).
3.4. NMR spectral analysis
1
1H NMR and 13C NMR chemical shifts were recorded in d6-DMSO. In the H NMR
spectra of the azo dyes, peaks of three hydroxyl groups were observed as a singlet peak
at 12.81–12.65 ppm, 12.36–11.08 ppm, and 10.90–10.47 ppm. The protons of the two
hydroxyl groups in the esterified products were determined between 11.95 and 11.08
ppm (and in the case of hydrogen bonding, from 10.90 to 10.47 ppm). The third peak,

15
ACCEPTED MANUSCRIPT
which resonated in the range of 12.81–12.65 ppm, disappeared as expected after
esterification. In Dyes 1 and 5, which bear a methyl group on the diazo unit, methyl
protons resonated as a singlet peak at 2.27 ppm. The peaks between 8.70 and 6.07 ppm
were attributed to the signals of aromatic and vinyl protons (Table 3 and Fig. 6). The
13C NMR spectra of acryloyl derivatives showed a low field signal at 164 ppm, which
can be attributed to the carbon atom of the >C=O group. Compounds 1–4 may be
expected to favor the azo tautomer in DMSO solvent since the carbonyl groups
expected for the hydrazone tautomer were not detected. The vinyl peaks of the acryloyl
derivatives resonated in the range of 162.3–102.9 ppm, close to the aromatic carbon
atom region (Table 4). The peaks appearing at 21 ppm of compounds 1 and 5 are
attributed to the carbon atom of the methyl group. The NMR data obtained in this study
are consistent with the literature [38].
3.5. Theoretical Results
The results of the B3LYP method with the 6-311 ++ G (2d, 2p) basis set were used in
this study due to experimental pertinence. The Appendix (supplementary data) shows
the data obtained from other methods and basis sets. The experimental UV–Vis
absorptions obtained in chloroform and ethanol compare favorably with theoretical
calculations. The absorption wavelengths of compounds 1–8 were calculated to be
between 411 nm and 443 nm in chloroform and between 411 nm and 431 nm in ethanol
(Table 5).
The UV–Vis theoretical calculations indicate that the bonding of the acryloyl group to
the resorcinol derivatives caused shifts to longer wavelengths. Considering the
resorcinol derivatives, the absorption wavelengths of the CH3, Cl, and NO2 substituents

16
ACCEPTED MANUSCRIPT
on the m-position of the phenyl ring are as follows: ꢀꢁꢂꢃ(ꢄ) > ꢀꢁꢂꢃ(ꢅ) > ꢀꢁꢂꢃ(ꢆ). Thus,
the m-CH3 leads to an enhanced bathochromic shift in comparison to m-Cl and m-NO2.
This ꢀꢁꢂꢃ trend is the same for CH3, Cl, and NO2 derivatives of acryloyl compounds 5,
7, and 8.
The absorption maxima in DMF shifted to longer wavelengths in the experimental
studies than that in chloroform and ethanol. Experimental UV studies showed that all
compounds absorbed in the 495–510 nm range at pH = 12 and in the 490–529 nm range
in DMF (not pH-adjusted). These shifts can be ascribed to the conversion of the azo
compounds and their acryloyl derivatives to hydrazone tautomers, as a function of
solvent and acidity. However, it is difficult to evaluate tautomerization through
experimental UV–Vis spectra. In order to clarify this interpretation, theoretical
calculations were performed with the B3LYP method with 6-311++G(2d,2p) basis set
for all possible hydrazone tautomeric structures in DMF. Figure 6 shows the possible
tautomers. Theoretical results obtained for hydrazones C and E are most pertinent to the
experimental results (Table 6). The calculated UV absorption values for the tautomers
were obtained in the range of 486–513 nm for B3LYP/bs3. Both the experimental and
theoretical results showed that the UV–Vis absorptions of the resorcinol derivative,
considering the possible tautomers, manifest at shorter wavelengths than their acryloyl
derivatives.
The molecular energy of compounds 1–8 obtained using the B3LYP method with 6-
311++G(2d,2p) was calculated to be lower than that of the other methods and basis sets.
In the calculations, the minimum molecular energies of the resorcinol derivative
compounds were calculated to be as follows: –1.258.324 au for m-Cl (molecule 3), –
1.003.271 au for m-NO2 (molecule 4), –838.030 au for m-CH3 (molecule 1), and –

17
ACCEPTED MANUSCRIPT
798.701 au for the unsubstituted derivative (compound 2). A similar sequence of energy
values was also observed for acryloyl derivatives 7, 8, 5, and 6. Furthermore, the m-NO2
substituted compounds 4 and 8 have a much larger dipole moment than the other
compounds. In comparison, m-Cl substituted compounds 3 and 7 have a larger dipole
moment than the remaining compounds (1, 2, 5, and 6). Therefore, bonding of the
acryloyl group to the resorcinol derivatives caused a decrease in the energy gap (∆E=
ELUMO − EHOMO) and molecular hardness but caused an increase in electronegativity.
The highest ∆E and chemical hardness (η) values were observed for m-NO2 substituted
compounds 4 and 8 (Table 7). Appendix 1–3 provides additional data.
Calculations for the azo–hydrazone tautomers provided remarkable results. The
molecular energies of the hydrazones should be lower than those of the azo compounds.
It is obvious that theoretical calculations gave results that support this expectation
(Table 8). However, the relationship between the calculated minimum molecular energy
levels of possible tautomers may not be the only indication of which tautomers are
present over the course of the experiment. Theoretical calculations indicate that the
compound with the lowest molecular energy for the azo–hydrazo compounds is the
possible hydroazo tautomer A, and the proposed tautomeric structure D for acryloyl
group molecules has lower molecular energies than those of the remaining possible
structures (Appendix 4). However, when the calculated energy gap (∆E) of possible
tautomers is examined, one encounters an interesting result: within the proposed
tautomeric structures, the energy gap of C and E, which compare favorably with the
experiments, is markedly smaller than that of other possible situations. Similarly, the
chemical hardness values of compounds C and E are also calculated to be quite small
compared to other possible situations.

18
ACCEPTED MANUSCRIPT
Tautomerization affected LUMO energies more than HOMO energies, and
consequently the difference between the HOMO–LUMO energies decreased (Figure 7
for compounds 1 and 5; Appendices 5a and 5b show other HOMO–LUMO and ESP
maps of the azo–hydrazone tautomers). The chemical hardness for the ground state of
an N electronic system is defined as
2
1 ꢉ ꢊ
ꢇ =
ꢈ
ꢌ
ꢍ(ꢎ)
,
(1)
2
2
ꢉꢋ
ꢏꢏꢐ
where E is the electronic energy, N is the number of electrons, and ꢍ(ꢎꢐ) is the constant
external potential. Equation 1 can be expressed using the finite difference
approximation
ꢇ = 12 (ꢑ− ꢒ),
(2)
where I and A can be approximated in terms of the energies of the FMOs; i.e., ꢑ =
−ꢊꢓꢔꢕꢔ and ꢒ = −ꢊꢖꢗꢕꢔ [39]. From Equations 1 and 2, the hydrazone tautomers are
more likely to be chemically reactive than the azo tautomers. In other words,
hydrazones are chemically softer than azo tautomers.
In addition, a noticeable increase in dipole moments of the hydrazone tautomers was
observed. In particular, the dipole moments of compounds 4 and 8 bearing m-NO2 were
higher than those of other molecules. An interesting situation pertains to the correlation
between the energy gap of possible hydrazone and azo tautomers. The Pearson
correlation coefficient R of the relationship between the energy gaps of hydrazones C
and E and the azo tautomers of compounds 1–8 was calculated to be 0.4988. For a
combination of hydrazones A, B, and D, the correlation coefficients were calculated to
be 0.7809 for A–D and 0.8209 for B, D (Graphic 1).

19
ACCEPTED MANUSCRIPT
The HOMO–LUMO energies of hydrazones C and E, which compare more favorably
with the experimental UV–Vis values, changed in a less-correlated fashion than those of
the other hydrazones. In other words, if there is a higher correlation between the
hydrazone and azo tautomers, the molecular electronic configurations of the compounds
are more protected; i.e., more resistant to a configurational change. Therefore, these
structures contribute less to the tautomerism.
4. Conclusion
In this research, o,o'-dihydroxy azo dyes that bear an acryloyl moiety were synthesized
through a reaction between o,o'-dihydroxy azo dyes and acryloyl chloride in a 1:1 molar
1
ratio. The structures of these compounds were characterized using IR, UV–Vis, H
NMR, and 13C NMR. In the UV–Vis spectra, the absorptions of compounds 1-8 in DMF
revealed significant shifts in acidic and basic conditions compared with neutral pH and
other solvents. After esterification, free hydroxyl peaks did not appear in the IR spectra
as expected. In the 13C NMR spectra of the acryloyl compounds in d6-DMSO, a
carbonyl peak was observed in the vicinity of 164 ppm. Both IR and NMR
spectroscopies showed that azo tautomers of azo and acryloyl derivatives were
dominant in the solid state and DMSO solvent.
The tautomerism proposed from experimental UV–Vis data was studied in detail by
quantum chemical calculations. Consequently, the Pearson correlation and energy gap,
∆E, was useful to determine the dominant tautomers. Although the energy gaps of
structures C and E were smaller than other hydrazones, the Pearson correlation
coefficient (R) of the relationship between structures C and E and the azo structures was

20
ACCEPTED MANUSCRIPT
lower than that of other correlations. The chemical hardness of hydrazones C and E was
calculated to be lower than that of other hydrazones. To the best of our knowledge, this
report is the first example of o,o'-dihydroxy resorcinol azo dyes bearing an acryloyl
moiety.
Acknowledgement
This study was supported by Scientific Research Council of Hitit University (Project No:
FEF 19001.14.005).
References
[1] A. Hassanzadeh, A. Zeini-Isffahani, M.H. Habibi, M.R.A. Poor Heravi, M.
1
Abdollahi-Alibeik, H, 13C, N-H, H-H, C-H COSY, H-H NOESY NMR and Uv-Vis
studies of Solophenyl red 3BL dye azo-hydrazone tautomerism in various solvents.
Spectrochimica Acta Part A. 63 (2006) 247-254.
[2] C. J. Patil, C. A. Nehete, The azo derivatives of salicylic acid, International Journal
of Pharmaceutical Sciences Review and Research 33(2) (2015) 248-256.
[3] C. T. K. Kumara, J. Keshavayya, T. Rajesh, S. K. Peethambarb, R. A. S. Alı,
Synthesis, characterization and antimicrobial activity of heterocyclic azodyes derived
from thiadiazole, Chemical Science Transactions 2(4) (2013) 1346-1351.
[4] P. Patel, D. Gor, P. S. Patel, Design, synthesis and pharmacological evaluation of
new series of pyrazolines based thiazolidin-4-one derivatives, Chemical Science
Transactions 2(4) (2013) 1089-1093.

21
ACCEPTED MANUSCRIPT
[5] S. Shahab, F. H. Hajikolaee, L. Filippovich, M. Darroudi, V. A. Loiko, R. Kumar,
M. Y. Borzehandani, Molecular structure and UV-Vis spectral analysis of new
synthesized azo dyes for application in polarizing films, Dyes and Pigments 129 (2016)
9-17.
[6] H. Valizadeh, A. Shomali, J. Ghorbani, S. Noorshargh, Synthesis of a nitrite
functionalized star-like poly ionic compound as a highly efficient nitrosonium source
and catalyst for the diazotization of anilines and subsequent facile synthesis of azo dyes
under solvent-free conditions, Dyes and Pigments 117 (2015) 64-71.
[7] M. Özkütük, E. İpek, B. Aydıner, S. Mamaş¸ Z. Seferoğlu, Synthesis, spectroscopic,
thermal and electrochemical studies on thiazolyl azo based disperse dyes bearing
coumarin, Journal of Molecular Structure 1108 (2016) 521-532.
[8] H. G. Garg, C. Prakash, Preparation of 4-arylazo-3,5-disubstituted-(2H)-1,2,6-
thiadiazine 1,1-dioxides, Journal of Medicinal Chemistry 15(4) (1972) 435-436.
[9] A. H. Shridhar, J. Keshavayya, S. K. Peethambar, H. Joy Hoskeri, Synthesıs of
1,3,4-oxadıazole incorporated azo dye derivatives as a potent biological activity
molecules, International Journal of Pharmacy and Pharmaceutical Sciences 4 (12)
(2012) 386-390.
[10] D. K. Sureja, K. R. Vadalia, POCl3 catalyzed, one-step, solvent-free synthesis of
some novel thieno[2,3-d]pyrimidin-4(3H)-one derivatives as antimicrobial agent,
Journal of Saudi Chemical Society http://dx.doi.org/10.1016/j.jscs.2016.07.004
[11] S. K. Paidesetty, S. K. Rout, J. Sahoo, Antimicrobial and antioxidant activities of
some newly synthesized benzene-1, 3-diol congeners and their characterization,
International Journal of Pharmacy and Pharmaceutical Sciences 7 (7) (2015) 427-433.

22
ACCEPTED MANUSCRIPT
[12] I. H. Pandya, R. N. Jadeja, K. J. Ganatra, Spectral characterization and biological
evaluation of Schiff bases and their mixed ligand metal complexes derived from 4,6-
diacetylresorcinol, Journal of Saudi Chemical Society 18 (2014) 190-199.
[13] N. Leopold, L, Szabó, A. Pîrnau, M. Aluas, L. F. Leopold, V. Chis, O. Cozar,
Raman spectroscopic and DFT theoretical study of 4-(2-pyridylazo)resorcinol and its
complexes with zinc(II) and copper(II), Journal of Molecular Structure 919 (2009) 94–
99.
[14] F. Karipcin, E. Kabalcilar, S. Ilican, Y. Cağlar, M. Cağlar, Synthesized some 4-(2-
thiazolylazo)resorcinol complexes: Characterization, thermal and optical properties,
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy,
Spectrochimica Acta Part A 73 (2009) 174–180.
[15] D. M. Patel, T. S. Patel, B. C. Dixit, Synthesis, characterization and dyeing
performance of new bisazo–bisazomethine disperse dyes, Journal of Saudi Chemical
Society 17 (2013) 203-209.
[16] R. A. Bawa, E. M. Alzaraide, Study of the Azo Hydrazone Tautomerism in the 4-
(9-Anthrylazo) Phenol, World Academy of Science, Engineering and Technology,
International Journal of Chemical, Molecular, Nuclear, Materials and Metallurgical
Engineering 8 (3) (2014) 241-243.
[17] A. Ünal, B. Eren, E. Eren, Investigation of the azo-hydrazone tautomeric
equilibrium in an azo dye involving the naphthalene moiety by UV–vis spectroscopy
and quantum chemistry, Journal of Molecular Structure 1049 (2013) 303-309.
[18] J. Dostanic, D. Mijin, G. Uscumlic, D.M. Jovanovic, M. Zlatar, D. Loncarevic.
Spectroscopic and quantum chemical investigations of substituent effects on the azo-

23
ACCEPTED MANUSCRIPT
hydrazone tautomerism and acid-base properties of arylazo pyridine dyes, Spectro
Chimica Acta Part A 123 (2014) 37-45.
[19] P. Ball, C. H. Nicholist, Azo hydrazone tautomerism of hydroxyazo compounds-A
Review, Dyes and Pigments 3 (1982) 5-26.
[20] M. Dakiky, K. Kanan, M., Khamis, Aggregation of o,o′-dihyroxyazo dyes II.
Interaction of 2-hydroxy-4-nitrophenylazoresorcinol in DMSO and DMF. Dyes and
Pigments 41 (1999) 199-209.
[21] H. Kocaokutgen, İ. E. Gümrükçüoğlu, Synthesis and characterization of some
novel azo dyes containing tert-butyl groups, Turkish Journal of Chemistry 19 (1995)
219-223.
[22] B. Babür, N. Seferoğlu, E. Aktan, T. Hökelek, E. Şahin, Z. Seferoğlu,
Phenylazoindole dyes 3: Determination of azo-hydrazone tautomers of new
phenylazoindole dyes in solution and solid state Journal of Molecular Structure 1081,
2015, 175-181
[23] A. Bayrakdar, H.H. Kart, S Elcin, H Deligoz, M Karabacak, Synthesis and DFT
calculation of a novel 5, 17-di (2-antracenylazo)-25, 27-di (ethoxycarbonylmethoxy)-
26, 28-dihydroxycalix [4] arene, Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy 136 (2015) 607-617.
[24] N. A. Wazzana, O. S. Al-Qurashia, H. M. Faidallaha, DFT/ and TD-DFT/PCM
calculations of molecular structure, spectroscopic characterization, NLO and NBO
analyses of 4-(4-chlorophenyl) and 4-[4-(dimethylamino) phenyl]-2-oxo-1,2,5,6-
etrahydrobenzo[h]quinoline-3-carbonitrile dyes, Journal of Molecular Liquids 223
(2016) 29–47.

24
ACCEPTED MANUSCRIPT
[25] R. P. Tayade, N. Sekar, Benzimidazole-thiazole based NLO phoric styryl dyes with
solid state emission – Synthesis, photophysical, hyperpolarizability and TD-DFT
studies, Dyes and Pigments 128 (2016) 111–123.
[26] S. Poorhaji, M.Pordel, S. Ramezani, New heterocyclic green, blue and orange dyes
from indazole: Synthesis, tautomerism, alkylation studies, spectroscopic
characterization and DFT/TD-DFT calculations, Journal of Molecular Structure 1119
(2016) 151–156.
[27] A. Georgieva, E. Bubeva, D. Dimovb, D. Yanchevac, I. Zhivkovb, J. Krajčovičd,
M. Valad, M. Weiterd, M. Machkovaa, Synthesis, structure, spectral properties and
DFT quantum chemical calculations of 4-aminoazobenzene dyes. Effect of
intramolecular hydrogen bonding on photoisomerization, Spectrochimica Acta Part A:
Molecular and Biomolecular Spectroscopy 175 (2017) 76–91.
[28] F. Bassala, A. D. Laurenta, B. Le Guennicb, D. Jacquemin, Exploring the excited-
states of squaraine dyes with TD-DFT, SOS-CIS(D) and ADC(2), Dyes and Pigments
138 (2017) 169–175.
[29] A. Regtia, H. B. E. Ayouchiab, M. R. Laamaria, S. E. Stiriba, H. Ananeb, M. El
Haddad, Experimental and theoretical study using DFT method for the competitive
adsorption of two cationic dyes from wastewaters, Applied Surface Science 390 (2016)
311–319.
[30] N. Şener, A. Bayrakdar, H. H. Kart, İ. Şener, A combined experimental and DFT
investigation of disazo dye having pyrazole skeleton, Journal of Molecular Structure
1129 (2017) 222–230.

25
ACCEPTED MANUSCRIPT
[31] H. Berber, C. Öğretir, E. Ç. S. Lekesiz, E. Ermis, Spectroscopic Determination of
Acidity Constants of Some Monoazo Resorcinol Derivatives, Journal of Chemical &
Engineering Data 53 (2008) 1049–1055.
[32] H. Kocaokutgen, S. Özkınalı, Characterisation and applications of some o,o'-
dihydroxyazo dyes containing a 7-hydroxy group and their chromium complexes on
nylon and wool, Dyes and Pigments 63 (2004) 83-88.
[33] P. Hohenberg, W. Kohn, Inhomogeneous electron gas, Physical Review 136 (1964)
B864–B871.
[34] W. Kohn, L. Sham, Self-consistent equations including exchange and correlation
effects, Physical Review 140 (1965) A1133–A1138.
[35] Gaussian 09, Revision B.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E.
Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.
A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J.
Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J.
Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A
Montgomer, J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N.
Kudin, V. N. Staroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A.
Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam,
M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R.
Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P.
Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, O. Farkas, J. B. Foresman,
J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian, Inc., Wallingford CT, 2010.

26
ACCEPTED MANUSCRIPT
[36] M. Gür, H. Kocaokutgen, M. Taş, Synthesis, spectral, and thermal characterisations
of some azo-ester derivatives containing a 4-acryloyloxy group, Dyes and Pigments 72
(2007) 101-108.
[37] X. L. You, C. R. Lu, Z. L. Huang, D. C. Zhang, IR, 1H NMR, 13C NMR and X-ray
structure
determination
of
1-(2′-chloro-4′-nitrophenylazo)-2,4-benzenediol,
intramolecular proton transfer between oxygen and nitrogen atoms, π…π interaction and
H-bonds, Dyes and Pigments. 63 (2004) 217-223.
[38] S. Özkınalı, Spectroscopic and thermal properties of newly mixed azocalix[4]arene
ester derivatives, Dyes and Pigments. 107 (2014) 81-89.
[39] G. Makov, Chemical Hardness in Density Functional Theory, J. Phys. Chem., 99
(23) (1995) 9337–9339.

ACCEPTED MANUSCRIPT
Table 3. 1H NMR spectral results of compounds 1-8
R
2
H
12
R
2
1
1
HO
6
H
13
HO
6
O
O
7
3
N
7
3
N
8
OH
N
4
H
N
11
4
OH
10
9
5
OH
10
9
5
R= CH3 (5), -H (6), -Cl (7), NO2 (8)
R= CH3 (1), -H (2), -Cl (3), NO2 (4)
Compound
OH
Azo Phenyl -H
Resorcinole-H
H9
Acryloyl-H
H11
H5
H6
H8
H3
H2 H1
H4
H10
H7
H12
H13
12.81 (s) 11.08 (s) 10.47(s)
12.68 (s) 11.42 (s) 10.49(s)
12.65 (s) 11.18 (s) 10.61(s)
12.79 (s) 12.36 (s) 10.77(s)
7.68 (d)
J=7.0
7.30 (d)
J=5.5
7.72 (d)
J=7.5
8.15 (d)
J=5.0
7.67 (d)
J=7.0
7.29 (t)
J=6.5
7.71 (d)
J=10.0
8.15-8.12
(m)
2.27 (s) 7.55 (s) 6.92 (d)
J=7.0
6.96 (t) 7.74 (d) 7.69 (d)
7.12 (d)
J=5.5
7.03 (d)
J=7.0
7.31 (d)
J=8.2
7.76 (d)
J=7.5
7.10 (d)
J=5.5
7.88 (d)
J=7.5
7.31 (d)
J=10.0
6.47 (d) 6.37 (s)
J=5.5
6.48 (d) 6.38 (s)
J=7.0
6.49 (d) 6.37 (s)
J=8.2
7.21 (d) 6.38 (s)
J=7.5
6.48 (d) 6.33 (s) 7.35-7.16 (m)
J=5.5
7.06 (d) 6.37 (s) 6.87-6.85 (m)
J=4.0
-
-
-
-
-
-
-
-
-
-
-
1
2
3
4
5
6
7
8
J=6.5
J=7.0
J=6.5
7.75 (s) 7.05 (d)
J=7.5
-
8.49 (s) 6.51 (d)
J=5.0
-
-
12.84 (s) 11.09 (s)
12.80 (s) 11.46 (s)
12.65 (s) 11.18 (s)
13.15 (s) 11.98 (s)
-
-
-
-
2.27(s) 7.54 (s) 6.92 (d)
J=7.0
6.96 (t) 7.67 (d) 7.73 (d)
6.58-6.50 (m)
6.22-6.17 (m)
6.22-6.15 (m)
6.25-6.16 (m)
6.13-6.07 (m)
6.49 (d)
J=6.5
J=7.5
J=6.5
J=4.0
7.75 (s) 7.06 (d)
6.93 (d) 6.37 (s) 7.58-7.40 (m)
J=10.0
7.60 (d) 6.30 (s) 6.98-6.78 (m)
J=7.5
6.60-6.45 (m)
-
J=10.0
8.70 (s) 7.78-7.71 7.95 (d)
(m) J=7.5
6.57-6.48 (m)
-

ACCEPTED MANUSCRIPT
Table 4. 13C NMR spectral results of compounds 1-8
R
5
6
HO
O
O
15
1
9
8
4
N
13
14
10
7
N
3
2
R= CH3 (1,5), -H (2,6), -Cl (3,7), NO2 (4,8)
OH
12
11
Compound
C13
C10
C8
C2
C15
C4
137.0
137.5
138.3
129.5
134.7
138.7
137.8
124.9
C14
C5
132.7
122.1
129.0
132.9
124.9
132.1
126.8
127.3
C6
132.4
128.0
131.1
137.0
127.9
136.0
127.4
133.3
C12
128.9
132.4
124.1
126.4
128.5
121.8
123.6
114.5
C1
128.3
131.9
132.8
140.6
134.5
118.9
131.5
146.1
C7
121.4
120.1
119.6
118.4
123.7
120.3
118.7
117.9
C3
117.8
118.0
119.3
114.9
118.7
118.8
116.7
112.0
C11
109.4
109.5
109.9
110.2
114.1
109.6
109.3
109.7
C9
103.5
103.5
103.6
103.4
111.3
103.6
102.9
102.9
R
20.5
-
162.9
163.1
163.8
164.4
155.4
162.3
157.3
159.0
157.3
157.4
157.8
159.6
153.8
155.4
152.2
150.9
151.4
153.5
152.7
158.3
152.5
154.3
145.5
157.8
-
-
-
-
-
1
2
3
4
5
6
7
8
-
-
-
-
-
-
-
-
-
164.6
164.5
164.4
164.9
138.3
137.8
143.2
142.7
129.2
128.1
134.6
135.1
21.0
-
-
-

ACCEPTED MANUSCRIPT
1
TABLES
IR spectral results of compounds 1-8
Table 1.
Table 2.
Table 3
Table 4
The UV-Vis data of the compounds (1-8)
1H NMR spectral results of compounds 1-8
13C NMR spectral results of compounds 1-8
Table 5. The UV-Vis data of azo forms calculated by some method and basis sets (BS1,
BS2 and BS3) in solvents (S1, S2 and S3)
Table 6
Theoretical UV-Vis results for possible tautomeric structures in DMF solvent
Table 7. Theoretical calculations of molecules 1-8 (B3lyp/6-311++g(2d,2p))
Table 8. Theoretical calculations of possible hydrazone C and E (by method B3LYP with 6-
311++g(2d,2p) basis set)

ACCEPTED MANUSCRIPT
2
Table 1. IR spectral results of compounds 1-8
Compound
Other functional
groups
2976 and
2916 (CH3)
-
νO-H
ν C-H
Arom.
ν C-H
Alkene
νC=O
νC=C
1621
1623
1627
1621
νAr-O
1178
1167
1169
1182
1
2
3
4
5
6
7
8
3277
3067
-
-
3488
3199
3447
3187
3492
3404
3198
3095
3080
3093
3072
3064
3082
3100
-
-
-
-
980 (C-Cl)
-
-
1516 and
1338 (NO2)
2922 (CH3)
2922
1742
1740
1746
1749
1624
1601
1615
1581
1622
1595
1623
1578
1240
1160
1241
1125
1256
1158
1211
1112
3202
3082
3178
2922
2853
2970
2852
2918
2853
-
979 (C-Cl)
1527 and
1343 (NO2)
Table 2. The Uv-Vis data of the related compounds (1-8)
Wavelength [λmax(nm)] (logε (L/mol.cm))
(pH= 1-2)
(DMF)
Compound
1
CHCl3
EtOH
DMF
(pH= 12) (DMF)
400s (4.73)
429 (4.77)
397s (4.62)
421 (4.61)
407s (4.77)
423 (4.73)
402 (4.74)
413s (4.73)
399s (4.70)
415 (4.69)
428 (4.60)
496s (4.36)
400 (4,64)
435s (4.59)
491s (4.26)
425 (4.75)
516s (4.29)
415 (4.61)
510 (4.63)
408 (4.52)
523s (4.11)
402 (4.56)
428s (4.53)
490s (4.25)
360 (3.94)
505 (4.22)
435 (4.61)
401 (4.43)
396 (4.51)
431s (4.45)
500s (4.06)
408 (4.59)
423s (4.58)
400s (4.59)
428 (4.64)
497 (4.63)
2
408s (4.46)
436 (4.53)
401s (4.75)
431 (4.83)
401s (4.46)
430 (4.50)
497 (4.70)
450s (4.68)
504 (4.72)
3
4
5
404 (4.54)
420 (4.46)
484s(4.12)
412 (4.42)
433s (4.39)
511s (4.02)
503 (4.58)
393 (4.59)
423s (4.60)
343s(4.51)
400 (4.54)
431s(4.58)
395 (4.76)
421s (4.72)
498 (4.58)
6
412 (4.57)
501s (4.32)
392s (4.31)
502 (4.58)
529s (4.53)
407 (4.52)
431s (4.49)
403 (4.79)
495 (4.66)
7
420 (4.54)
469s (4.44)
399 (4.43)
441s(4.37)
449s (4.46)
510 (4.50)
396 (4.82)
8
s: Shoulder peaks