New coumarin-based disperse disazo dyes: Synthesis, spectroscopic properties and theoretical calculations

Article abstract of DOI:10.1016/j.molliq.2016.08.008

5-Amino-4-arylazo-3-methyl-1H-pyrazoles (3a-l) have been diazotised and coupled with 4-hydroxycoumarin to give rise to the coumarin-based disperse disazo dyes (3a-l). The newly synthesized twelve coumarin-based disperse disazo dyes have been characterized by using the elemental analysis and the spectral methods. The solvatochromic behavior of these dyes in various solvents is evaluated. Substituent, acid and base effects on the visible absorption spectra of the dyes substituted with electron-withdrawing and electron-donating groups at their o-, m-, p-position are also reported in detail. Molecular geometries and spectroscopic properties of the compounds considered in this work are also analyzed by using ab initio calculation methods based on the density functional theory (DFT) in the ground state. The theoretical results obtained from DFT are compatible with the experimental results.

Full text of DOI:10.1016/j.molliq.2016.08.008

New coumarin-based disperse disazo dyes: Synthesis, spectroscopic proper-
ties and theoretical calculations
Fati Yıldırım, Aykut Demirc¸alı, Fikret Karcı, Alpaslan Bayrakdar, Pınar
Tunay Tas¸lı, H.Hu¨seyin Kart
PII:
DOI:
Reference:
S0167-7322(16)30537-2
doi: 10.1016/j.molliq.2016.08.008
MOLLIQ 6167
To appear in:
Journal of Molecular Liquids
Received date:
Accepted date:
4 March 2016
1 August 2016
Please cite this article as: Fati Yıldırım, Aykut Demir¸calı, Fikret Karcı, Alpaslan Bayrak-
dar, Pınar Tunay Ta¸slı, H.Hu¨seyin Kart, New coumarin-based disperse disazo dyes: Syn-
thesis, spectroscopic properties and theoretical calculations, Journal of Molecular Liquids
(2016), doi: 10.1016/j.molliq.2016.08.008
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ACCEPTED MANUSCRIPT
New coumarin-based disperse disazo dyes: synthesis, spectroscopic
properties and theoretical calculations
Fati Yıldırıma, Aykut Demirçalıb, Fikret Karcıb*, Alpaslan Bayrakdarc, Pınar Tunay Taşlıc
H.Hüseyin Kartc,
aDepartment of Chemistry and Chemical Processing Technologies, Pamukkale University,
Denizli, Turkey
bDepartment of Chemistry, Faculty of Science-Arts, Pamukkale University,
Denizli, Turkey
cDepartment of Physics, Faculty of Science-Arts, Pamukkale University, Denizli, Turkey
Abstract
5-amino-4-arylazo-3-methyl-1H-pyrazoles (3a-l) have been diazotised and coupled with 4-
hydroxycoumarin to give rise to the coumarin-based disperse disazo dyes (3a-l). The newly
synthesized twelve coumarin-based disperse disazo dyes have been characterized by using the
elemental analysis and the spectral methods. The solvatochromic behavior of these dyes in
various solvents is evaluated. Substituent, acid and base effects on the visible absorption
spectra of the dyes substituted with electron-withdrawing and electron-donating groups at
their o-, m-, p-position are also reported in detail. Molecular geometries and spectroscopic
properties of the compounds considered in this work are also analyzed by using ab initio
calculation methods based on the density functional theory (DFT) in the ground state. The
theoretical results obtained from DFT are compatible with the experimental results.
Keywords: Coumarin, Pyrazole, Disperse dyes, Disazo dyes, Solvatochromism, DFT
*Corresponding author. Phone: +90 258 2963598 Fax: +90 258 2963535
*E-mail address: fkarci@pau.edu.tr

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Introduction
4-Hydroxycoumarin is an important component of numerous synthetic and natural
products with wide-ranging biological activities, including anticoagulant, insecticidal,
anthelminthic, hypnotic, antifungal, phytoalexin, and HIV protease inhibition [1-4]. These
special properties of 4-hydroxycoumarin have stimulated considerable interest in this class of
compounds. 4-hydroxycoumarin also finds application in dyes [5-8]. 4-hydroxycoumarin in
these dyes uses as a heterocyclic coupling component.
Fused pyrazoles are important compounds having many derivatives with a wide range
of interesting properties such as antihyperglycemic, analgestic, anti-inflammatory, anti-
pyretic, anti-bacterial, hypoglycaemic and sedative-hypnotic activity. Recently, some
pyrazoles have been reported to have nonnucleoside HIV-1 reverse transcriptase inhibitory
activity [9-14]. Some azopyrazole derivatives also find application in dyes, biological and
pharmacological studies and complexes [15-20].
The use of heterocyclic intermediates in the synthesis of azo disperse dyes is well
established and the resultant dyes exhibit good tinctorial strength and brighter dyeing than
those derived from aniline-based diazo components. For instance, amino-substituted thiazole,
benzothiazole [21-24] and benzoisothiazole [25] compounds afford higly electronegative
diazo components and consequently, provide a pronounced bathochromic effect compared to
the corresponding benzoid compounds.
We have reported the synthesis, spectroscopic properties and theoretical calculations
of some heterocyclic azo dyes in our previous works [26-28]. We report in this work the
synthesis, spectroscopic properties and theoretical calculations of a series of new disperse
disazo dyes based on coumarin ring.
Recently, theoretical calculations of chemical compounds have attracted increasing
attention due to their interesting electronic and geometrical features in connection with their
applications [29]. In this study, the molecular structure, vibrational and NMR spectra of the
disazo dyes 3a–l are calculated by using the quantum chemistry methods based on DFT level
with the basis set of 6-311G(d,p). Comparisons of the experimental and theoretical
calculations can be very useful in making correct assignment and understanding the basic
vibrational, NMR spectra and molecular structure.

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Experimental
General
The chemical materials used for the synthesis of the compounds have been obtained
from Aldrich and Merck Chemical Company without further purification. The used solvents
are of spectroscopic grade.
IR spectra have been determined by using a Mattson 1000 Fourier Transform-infrared
(FT-IR) spectrophotometer on a KBr disc. Nuclear magnetic resonance (1H NMR) spectra
have been recorded on a Bruker-Spectrospin Avance DPX 400 Ultra-Shield in deuterated
dimethylsulphoxide (DMSO-d6) by using tetramethylsilane (TMS) as the internal reference;
chemical shifts () is given in the unit of ppm. Ultraviolet-visible (UV-vis) absorption spectra
have been recorded on a Schimadzu UV-1601 double beam spectrophotometer at the
wavelength of maximum absorption (max) in a range of solvents, i.e. DMSO, DMF,
acetonitrile, methanol, acetic acid and chloroform at the various concentrations (1x 10-6-10-8).
Melting points have been determined on an Electrothermal 9100 melting point apparatus and
they are uncorrected. Elemental analysis has been done on a Leco CHNS-932 analyzer.
Characterizations data are given in Table 1, 2 and 3, respectively.
Synthesis of 2-arylhydrazono-3-ketiminobutyronitriles (1a-l) and 5-amino-4-arylazo-3-
methyl-1H-pyrazoles (2a-l)
2-Arylhydrazone-3-ketiminobutyronitriles (1a-l) and 5-amino-4-arylazo-3-methyl-1H-
pyrazoles (2a-l) have been prepared according to the procedures following in the literatures
[30,31]. The general procedure for the synthesis of 2-arylhydrazono-3-ketiminobutyronitriles
and 5-amino-4-arylazo-3-methyl-1H-pyrazoles is given in Scheme 1.
Scheme 1 here about
Synthesis of coumarin-based disperse disazo dyes (3a–l)
5-Amino-4-arylazo-3-methyl-1H-pyrazoles (0.01 mol) have been dissolved in a
mixture of glacial acetic acid and concentrated hydrochloric acid (20 ml, ratio 1:1) and the
solution is then cooled to 0–5 °C. Sodium nitrite (0.69 g, 0.01 mol) in water (10 ml) is then
added to this solution dropwise with vigorous stirring, about 1 h, while cooling at 0–5 °C.
Then the resulting diazonium solution is added in portions over 30 min to a vigorously stirred
solution of 4-hydroxycoumarin (1.62 g, 0.01 mol) in Na2CO3 (1.06 g, 0.01 mol) and water (20

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ml) between 0 and 5 °C, maintaining the pH at 7–8 by simultaneous addition of sodium
acetate solutions. The mixture is then stirred for 2 h between 0 and 5 °C. The precipitated
product is separated upon dilution with water (50 ml) and then filtered off, washed with water
several times, dried and crystallized from DMF–H2O, respectively. The general procedure for
the synthesis of disazo dyes 3a–l is given in Scheme 2.
Scheme 2 here about
Computational Method
The theoretical calculations for the disazo dyes 3a–l molecules have been performed
by using the Density Functional Theory (DFT) based on B3LYP (Becke’s three-parameter
hybrid model using the Lee–Yang–Parr correlation functional) hybrid functional with 6-
311G(d,p) basis set [32,33]. Theoretically based studies have been performed by utilizing the
GAUSSIAN 09W package software by using quantum chemical calculation techniques [34].
The DFT method has been displayed a rather satisfying performance in terms of the desired
sensitivity, computation time and power [35]. The DFT calculations based on B3LYP level
produce much more sensitive results in predicting structural and electronic characteristics than
HF methods [36].
The most stable optimal structure of the title molecule has been determined through an
optimization by using the B3LYP/6-311G(d,p) level. The optimized geometric structure of the
title compound is given in Fig 1.
Fundamental vibration modes of the molecule have been calculated with the help of
vibration spectrum analysis that is performed by following the optimized structure of title
molecule. Vibrational data which are calculated from DFT method theoretically have been
scaled by 0.967 to compare them with the experimental data [37]. All of the wave numbers
obtained as a result of calculations have been found to be positive. This fact shows the success
of the optimization of title molecule. The data obtained from theoretical studies have been
assigned with the GAUSSVIEW 5.0.8 and the VEDA 4 program [38,39].
1
The H-NMR chemical shift values of the molecules considered in this work have
been predicted by using the same level method via the Gauge-Including Atomic Orbital
(GIAO) method [40]. The obtained theoretical data are compared with experimental results.
1
The H-NMR chemical shift calculations are analyzed by taking Tetramethylsilane (TMS) as
a reference.

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Fig. 1 here about
HOMO-LUMO molecular orbitals have been calculated by performing the frontier
molecular orbital analysis to determine their chemical reactivity. For each of the Tautomer
structures, the electronic absorption spectrum are calculated with the Time Dependent Self-
Consistent Field (TD-SCF) and B3LYP/6-311G(d,p) level and then compared with the
experimental results. Contributions from molecular orbitals to electronic transitions have been
determined by using the GaussSum 3.0 software [41].
Results and Discussion
Vibrational analysis
Coumarin-based disperse disazo dyes titled as 3a-l can exist in six possible tautomeric
forms, namely the disazo-enol forms T1 and T3, the azo-hydrazo-keto form T2, the hydrazo-
azo-enol forms T4 and T6 and the dishydrazo-keto form T5 as shown in Scheme 3. The FT-
IR spectra of dyes 3a-l shows broad hydroxy (OH) bands at 3498-3467 cm-1, intense carbonyl
(C=O) bands at 1764-1712 cm-1 and C-O bands at 1108-1083 cm-1. The other max values of
3212-3127 cm-1 (N-H), 3096-3060 cm-1 (aromatic C-H), 2993-2971 cm-1 (aliphatic C-H) and
1467-1440 cm-1 (-N=N-) are recorded. These suggest that coumarin-based disperse disazo
dyes 3a-3l are predominantly in disazo-enol forms T1 and T3 or hydrazo-azo-enol forms T4
and T6 as opposed to the other tautomeric forms T2 and T5 in the solid state.
The theoretical FT-IR spectra of the 3a-l tautomer structures have been calculated by
utilizing the DFT method based on B3LYP/6-311G(d,p) level. According to these
calculations, all of the molecular structures have the C1 point group symmetry. As their
molecular structures are non-planar, each structure has the 3N-6 fundamental vibration mode.
Because 3i has 44 atoms in its molecular structure, for instance, it has 126 fundamental
vibration modes. In the 3a-l tautomer structures of the FT-IR spectrum, all the vibrations are
active (all the fundamental vibrations are active in IR spectra). The fundamental vibration
modes belonging to the C=O, C-O, N=N, N-H, OH, Ali-H and Aro-H specific functional
groups of the 3a-l structures are marked and compared with the values experimentally
obtained, and are presented in Table 2. The correlations between these experimental and
theoretical data for each molecule as given in Table 2 are also calculated. As can be seen in
Table 2, the biggest of these correlation values is 0.9826 for 3j while the smallest value for

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the 3a structure is calculated to be 0.9716. Among these correlation values, those
experimental observations are found to be very compatible with the theoretical data.
The N-H stretching vibrations normally occur at the 3500-3200 cm-1 region of the
spectrum [42]. But they are observed at the 3250-3650 cm-1 region in the infrared spectrum by
Ganiyat et al [43]. In this study, for the 3a-l structures, the N-H stretching vibration is
observed at the 3690-3624 cm-1 range although it was theoretically marked at the range of
3550-3543 cm-1. PED analysis shows that this mode is almost pure N-H stretching vibration
(PED, 100%) for all structure.
O-H groups make stretching vibrational motions. If the molecular structure contains a
free hydroxy group or if it does not contain a hydrogen bond, it is at the 3550-3700 cm-1
strong stretching band [44]. If the structure contains a phenol group and a hydrogen bond,
then the O-H stretching band is decreased towards the 3200-3550 cm-1 region [45,46]. In this
study, all of the 3a-l structures have a hydrogen bond. In this study, the O-H stretching
vibrations are recorded at the range of 3498-3433 cm-1 in the FT-IR spectrum while they are
marked at the range of 3446-3433 cm-1 in theoretical calculations. PED analysis shows that
this mode is almost pure O-H stretching vibration (PED, 99%) for all structure.
The C=O vibration band is one of the most distinctive functional groups. The C=O
band makes a strong stretching motion into regions at the range between 1600 cm-1 and 1800
cm-1 [47,49]. For the 3a-l structures, in this study, the C=O group vibrational band in the FT-
IR spectrum is observed at the range of 1765-1712 cm-1 and this vibrational band is marked at
the range of 1779-1771 cm-1 for the level of B3LYP/6-311G(d,p) in our calculations. PED
analysis indicates that this mode is almost pure N-H stretching vibration (PED, 89-90%) for
all structure.
The N=N bond is one of the strongest types of bonds and it displays vibrational mode
stretching motion. In the current study, the value of the N=N stretching vibrational mode is
observed at the range of 1467-1440 cm-1 while the calculations recorded the range of 1483-
1462 cm-1 for the level of B3LYP/6-311G(d,p).
The Aro-H stretching vibrations display a weak stretching band in the FT-IR spectrum
at the range of 3100-3000 cm-1 [47,50]. They are experimentally observed at the range of
3075-3063 cm-1. They are also marked at the range of 3074-3064 cm-1 in the theoretical study.
The Ali-H alkenes stretching vibrations normally occur at the range of 3000-2850 cm-1
in the spectrum [46]. In the current study, the aliphatic C-H stretching vibrations are
experimentally observed at the range of 2990-2953 cm-1 and they are marked at the range of
2993-2988 cm-1 in the theoretical calculation.

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1H-NMR analysis
1H-NMR spectra of dyes 3a-l shows three broad peaks at 16.19-15.65 ppm (tautomeric
NH), 14.76-14.22 ppm (pyrazole NH) and 13.69-13.41 ppm (OH), respectively. The other δ
values of 2.70-2.58 ppm (CH3) and 8.69-6.91 ppm (aromatic H) are recorded. On the other
1
hand, theoretical H NMR data (dye 3a-3l) obtained from B3LYP/6-311G(d,p) level by
utilizing GIAO method are collected in Table 3 as well as experimental data. These results
suggest that dyes 3a-l are present in the mixture of the tautomeric forms T1, T2 and T3 as
opposed to the other tautomeric forms T4, T5 and T6 in DMSO.
Scheme 3 here about
Frontier Molecular Orbitals
The highest of the molecular orbitals which represent the electron donation capability
of a molecule and which are filled by electrons is called the HOMO orbital. The lowest
molecular orbitals which represent the electron acceptance capability are described as the
LUMO orbital [51]. The HOMO-LUMO orbitals are also known as the frontier molecular
orbitals. The frontier molecular orbital analysis is very important for determining the optical
and electrical characteristics of molecules [52]. The difference between the HOMO-LUMO
orbitals is known as the HOMO-LUMO band gap. The energy difference between these
orbitals helps us easily to understand molecular interaction mechanisms with other molecules.
This energy range also enables to determine a molecule's kinetic stability, its chemical
reactivity and chemical hardness-softness [53,54]. A bigger HOMO-LUMO gap means that
less electron flow will occur in high-energy situations. In this situation, the molecule will be
harder and less reactive. A smaller HOMO-LUMO gap means that electrons easily pass to
high-energy situations. In this case, the molecule will be softer and more reactive. For 3a-l
structures, a frontier molecular orbital analysis is performed by the DFT method by
employing the level of B3LYP/6-311G(d,p) to determine the HOMO-LUMO orbitals. By
using these data, the structures (3a-l) are characterized by calculating the ionization potential
(I), electron affinity (A), global electronegativity (χ), global electrophilicity (ω), total hardness
(η), chemical potential (μ) and global softness (S). The data obtained from the frontier
molecular orbital are presented in Table 4.
As can be seen in Table 4, the lowest energy gap is shown in 3b as a 2.715 eV
followed by 3j with 2.776 eV while the highest energy gap belongs to the 3b structure with

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3.060 eV. This situation tells us that the structure 3e is chemically softer and has higher
chemical reactivity compared with others.
Solvent effects on UV-vis spectra
The UV-vis absorption spectra of dyes 3a-l are recorded over the range of  between
300-700 nm, using a variety of solvents in concentrations (10-6-10-8 M) and the results are
summarized in Table 5. The visible absorption spectra of the dyes do not correlate with the
polarity of solvent.
Dyes 3a-l give two maximum absorption peaks in all used solvents. This result
suggests that dyes 3a-l is present in two tautomeric forms in all used solvents.
It is observed that in DMSO, DMF, acetonitrile, methanol and acetic acid especially
second max (max at longer wavelength) of dyes 3a-l shifts hypsochromically with respect to
the max in chloroform (e.g. for dye 3l max are 340 and 467 nm in chloroform, 338 and 442
nm in DMSO, 337 and 440 nm in DMF) (Fig.2). It is also observed that absorption spectra of
dyes 3a-l in DMSO, DMF, acetonitrile, methanol and acetic acid are similar.
The UV-vis spectrum of 3a-l is analyzed both experimentally and theoretically.
Experimentally, the UV-vis spectra of the compounds are measured in six different solutions
(acetonitrile, acetic acid, methanol, chloroform, DMF and DMSO). The absorption of maxima
of the compounds is calculated by the Time Dependent Self-Consistent Field (TD-SCF)
method utilizing the level of B3LYP/6-311G(d,p) and they are listed in Table 5. In this study,
the UV-vis absorption spectrum of the 3a-l compounds are recorded by using the
concentrations of various solutions in the k region that is located at the range of 300 and 700
nm (1 × 10−6 –1 × 10−8 M).
The major and minor contributions from the HOMO, LUMO orbitals to transitions
have been determined with the help of the GaussSum 3.0 software by using the output file of
the Gaussian 09W package software. It can be seen from Table 5 that, according to the
calculated absorption spectra, contributions are made to the electronic transitions in the
absorption wavelength of the 3e dye including a major contribution from HOMO to LUMO
by 81% and from HOMO-1 to LUMO by 13% and a minor contribution from HOMO-4 to
LUMO by 5%. Table 5 also shows other wavelengths and the major and minor contributions
corresponding to the electronic transitions in those wavelengths. The chloroform solution of

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the dye is chosed as reference while wave’s contribution corresponding to electronic
transitions in absorption spectra is calculated.
Fig. 2 here about
Acid and base effects on UV-vis spectra
The effects of acid and base on the absorption of dye solutions have been investigated
and the results are shown in Table 6. The absorption spectra of the dyes in methanol is also
quite sensitive to the addition of base (potassium hydroxide, 0.1 M), with max of dyes 3a-l
showing bathochromic shifts and absorption curves of the dyes resembled those in chloroform
except for dye 3f. When potassium hydroxide (0.1 M) is added to dye 3f solution in methanol,
absorption spectra gives three maximum absorption peaks (Fig. 3). This result suggests that
these dyes are present in a different tautomeric form in methanol + KOH than that in
methanol and this tautomeric form resembled those in chloroform.
Fig. 3 here about
When hydrochloric acid (0.1 M) is added to dye solutions in methanol, max of dyes
3a-l showing little bathochromic shifts with respect to the max in methanol and the absorption
spectra of dyes resembled those in acetic acid (Fig. 3).
When piperidine is added to dye solutions in chloroform, max of dyes 3a-l shows little
bathochromic shifts with respect to the max in chloroform (Fig. 4).
Fig. 4 here about
Conclusions
A series of twelve novel coumarin-based disperse disazo dyes 3a-l have been
synthesized by coupling reaction to 4-hydroxycoumarin. Solvent and acid-base influences on
the wavelength of maximum absorption have been studied. In the present paper, coumarin-
based disperse disazo dyes shows solvatochromic effects. The absorption maxima of dyes
shows bathochromic shifts in chloroform than the other five solvents. It is also observed that

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the absorption spectra of these disperse disazo dyes in methanol are quite sensitive to the
addition of base.
The experimental and theoretical investigations of the dyes 3a-l are successfully
performed by using FT-IR, NMR spectra and quantum chemical calculations. Ab initio
calculations based on the density functional theory (DFT) for dyes 3a-l compounds are
presented in this work for the first time. Characterizations data are shown in Table 1. The
recorded FT-IR and the calculated vibrational wavenumbers, along with their relative
intensities and probable assignments are given in the Table 2. The vibration frequencies,
optimized molecular structure and corresponding vibration assignment of dyes 3a-l have been
calculated using DFT method with the level of 6-311G(d,p) basis set and the calculated results
have been compared with the experimental data. Theoretical electronic absorption spectra of
title compound (absorption wavelength
) by using TD-DFT/B3LYP/6-311G(d,p) method,
in experimental, solvent (chloroform) and gas phase, are given in Table 3. HOMO and
LUMO energy gap propounds that the energy gap reflects the chemical activity of the
molecule. The electronic properties are also calculated and the experimental electronic
spectrum is recorded with the help of UV–Vis spectrometer.
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[38] R. D. Dennington, T. A. Keith, J. M. Millam, GaussView 5, Gaussian Inc., 2008.
[39] M. H. Jamroz, Vibrational Energy Distribution Analysis VEDA 4, Warsaw, 2004.
[40] R. Ditchfiled, J. Chem. Phys. 56 (1972) 5688–5691.
[41] N. M. O’Boyle, PhD. Thesis, Dublin City University, 2004.
[42] D. L. Pavia, G. M. lampman, G. S. Kris, Introduction to spectroscopy, second ed.,
Harcourt Brace College, 1996. pp. 28–31.
[43] G. K. Oloyede, P. A. Onocha, J. M. Oke, American-Eurasian Journal of Scientific
Research (2011) 116-122.
[44] A. Teimouri, A.N. Chermahini, K. Taban, H. A. Dabbagh, Spectrochim. Acta A 72
(2009) 369–377.
[45] D. Mahadevan, M. Karabacak, S. Periandy, S. Ramalingam, Spectrochim. Acta A 86
(2012) 139-151.

ACCEPTED MANUSCRIPT
13
[46] G. Varsanyi, Vibrational Spectra of Benzene Derivatives, Academic Press, New York,
1969.
[47] G. Socrates, Infrared and Raman Characteristic Group Wave Numbers-Tables and
Charts, Third ed., John Wiley and Sons, New York, 2001.
[48] A. Atac, M. Karabacak, E. Kose, C. Karaca, Spectrochim. Acta A 83 (2011) 250-258.
[49] V. Krishnakumar, N. Prabavathi, Spectrochim. Acta A 72 (2009) 743–747.
[50] A. M. Asiri, M. Karabacak, M. Kurt, K. A. Alamry, Spectrochim. Acta A 82 (2011) 444–
455.
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[52] I. Fleming, Frontier Orbitals and Organic Chemical Reactions, Wiley, London, 1976.
[53] B. Kosar, C. Albayrak, Spectrochim. Acta A 78 (2011) 160–167.
[54] A. M. Asiri, M. Karabacak, M. Kurt, K. A. Alamry, Spectrochim. Acta A 82 (2011) 444-
455.

ACCEPTED MANUSCRIPT
14
Scheme Captions
Scheme 1 Synthesis of aminoarylazopyrazoles (2a-l)
Scheme 2 Synthesis of coumarin-based disperse disazo dyes 3a-l
Scheme 3 Tautomeric equilibriums of dyes 3a-l
Figure Captions
Fig. 1 The calculated optimized structures of dyes 3a-l
Fig. 2 Absorption spectra of dye 3l in various solvents
Fig. 3 Absorption spectra of dye 3f in acidic and basic solutions
Fig. 4 Absorption spectra of dye 3f in acidic and basic solutions
Table Captions
Table 1 Elemental analysis of dyes 3a-l
Table 2 FT-IR data for dyes 3a-l
Table 3 1H-NMR data for dyes 3a-l
Table 4 Frontier Orbital Analysis
Table 5 Theoretical electronic absorption spectra of title compound (absorption wavelength
using TD-DFT/B3LYP/6-311G(d,p) method in experimental, solvent
(chloroform) and gas phase.
Table 6 Absorption maxima of dyes 3a-l in acidic and basic solutions

ACCEPTED MANUSCRIPT
15
CN
NC
H
NH2
CH3
NH
_
H2NNH2H2O
+
C
C
N2 Cl
N
N
C
NH2
N
N
C
+
H
CH3
X
X
X
NH
(1a-l)
H3C
N
(2a-l)
i, X : o-NO2
e, X : m-NO2
a, X : p-NO2
j, X : o-OCH3
f, X : m-OCH3
b, X : p-OCH3
k, X : o-Cl
l, X : o-CH3
g, X : m-Cl
h, X : m-CH3
c, X : p-Cl
d, X : p-CH3
Scheme 1 Synthesis of aminoarylazopyrazoles (2a-l)

ACCEPTED MANUSCRIPT
16
O
N
O
O
O
_
+
N2
N
N
N
Cl
N
N
N
N
NH2
OH
X
NaNO2/HCl
CH3COOH
X
OH
X
NH
NH
H3C
NH
N
H3C
N
H3C
N
(3a-3l)
(2a-2l)
Scheme 2 Synthesis of coumarin-based disperse disazo dyes 3a-l

ACCEPTED MANUSCRIPT
17
HO
N
O
O
O
N
O
O
O
N
O
H
N
N
N
N
N
N
N
N
N
X
OH
X
X
KT
NH
KT
H3C
NH
NH
N
H3C
H3C
N
N
disazo-enol
(T3)
disazo-enol
(T1)
azo-hydrazo-keto
(T2)
KT
KT
HO
O
O
O
H
O
O
N
O
H
H
N
H
N
N
N
N
N
N
N
N
N
N
X
O
X
OH
N
X
KT
KT
N
H3C
N
N
H3C
N
H3C
N
hydrazo-azo-enol
(T6)
dishydrazo-keto
(T5)
hydrazo-azo-enol
(T4)
Scheme 3 Tautomeric equilibriums of dyes 3a-l

ACCEPTED MANUSCRIPT
18
Fig. 1 The calculated optimized structures of dyes 3a-l

ACCEPTED MANUSCRIPT
19
Fig. 2 Absorption spectra of dye 3l in various solvents

ACCEPTED MANUSCRIPT
20
Fig. 3 Absorption spectra of dye 3f in acidic and basic solutions

ACCEPTED MANUSCRIPT
21
Fig. 4 Absorption spectra of dye 3f in acidic and basic solutions

ACCEPTED MANUSCRIPT
22
Table 1 Elemental analysis of dyes 3a-l
Dye Molecular formula
m.p.a (oC)
Yield
(%)
91
Elemental analysis: calc. (found)
no
(m. wt)
(colour)
C
H
N
C19H13N7O5 (419.3)
290-291 (red)
54.42
3.12
23.38
3a
(54.79)
59.40
(3.19)
3.99
(23.17)
20.78
C20H16N6O4 (404.3)
276-277 (red)
288-289 (red)
289-290 (red)
84
87
73
86
77
79
65
89
81
86
71
3b
3c
3d
3e
3f
(59.63)
55.82
(4.08)
3.21
(20.61)
20.56
C19H13ClN6O3
(408.7)
(55.67)
61.85
(3.13)
4.15
(20.74)
21.64
C20H16N6O3 (388.3)
(61.93)
54.42
(4.27)
3.12
(21.57)
23.38
C19H13N7O5 (419.3)
C20H16N6O4 (404.3)
300-301
(yellow)
(54.71)
59.40
(3.04)
3.99
(23.22)
20.78
274-275 (red)
(59.78)
55.82
(4.12)
3.21
(20.63)
20.56
C19H13ClN6O3
(408.7)
293-294 (red)
279-280 (red)
3g
3h
3i
(55.58)
61.85
(3.09)
4.15
(20.69)
21.64
C20H16N6O3 (388.3)
(61.77)
54.42
(4.22)
3.12
(21.85)
23.38
C19H13N7O5 (419.3)
C20H16N6O4 (404.3)
282-283
(orange)
(54.82)
59.40
(3.17)
3.99
(23.49)
20.78 (20.
69)
261-262 (red)
3j
(59.70)
55.82
(4.05)
3.21
C19H13ClN6O3
(408.7)
269-270
(orange)
266-267
(orange)
20.56
3k
3l
(55.61)
61.85
(3.17)
4.15
(20.49)
21.64
C20H16N6O3 (388.3)
(61.63)
(4.07)
(21.48)
a Recrystallization from DMF/H2O

ACCEPTED MANUSCRIPT
Table 2 FT-IR data for dyes 3a-l
Dye
no
Correlation
value
O-H
N-H
Aro-H
Al-H
C=O
N=N
C-O
Calc.
Exp.
3475
3498
3492
3481
3470
3486
3486
3476
3467
3482
3495
3482
Calc.
3543
3547
3546
3547
3545
3546
3546
3546
3546
3550
3546
3548
Exp.
3209
3190
3209
3197
3127
3206
3212
3203
3178
3212
3171
3181
Calc.
Exp.
3069
3069
3060
3072
3069
3066
3063
3069
3069
3063
3096
3063
Calc.
Exp.
2974
2993
2977
2989
Calc.
Exp.
1712
1740
1725
1748
1716
1720
1723
1721
1759
1718
1764
1761
Calc.
Exp.
1462
1448
1464
1451
1463
1447
1455
1462
1462
1463
1440
1467
Calc.
Exp.
1103
1088
1083
1085
1108
1097
1101
1100
1085
1096
1085
1087
3446
3434
3441
3436
3445
3436
3441
3435
3444
3433
3440
3436
3074
3072
3073
3072
3073
3071
3073
3073
3073
3064
3068
3067
2991
2987
2988
2988
2992
2988
2990
2988
2993
2988
2991
2993
1776
1779
1777
1778
1470
1780
1769
1462
1471
1465
1467
1469
1483
1483
1483
1478
1158
1091
1091
1090
1158
1090
1091
1090
1091
1158
1091
1091
0.9716
0.9779
0.9815
0.9799
0.9722
0.9806
0.9821
0.9812
0.9792
0.9826
0.9754
0.9781
3a
3b
3c
3d
3e
3f
2984 1775
2990
2977
2971
2988
3974
2987
2987
1779
1777
1779
1772
1774
1771
1775
3g
3h
3i
3j
3k
3l

ACCEPTED MANUSCRIPT
Table 3 1H-NMR data for dyes 3a-l
Dye
no
B3LYP, 1H NMR (ppm) (IEFPCM
model, in DMSO) TMS B3LYP/6-
311++G(d,p) GIAO
1H NMRa (, ppm, in DMSO-d6)
Aro.-H
6.92-8.48
(8H, m)
Alip.-H
2.70 (3H, s,
CH3)
X-H
13.69 (br, OH)
14.72 (1H, br, NH)
16.10 (br, tautomeric
NH)
Aro.-H
7.49 -8.60
(8H,m)
Alip.-H
2.45 -2.85 (3H,
CH3)
X-H
9.70 (1H,
OH)
9.66 (1H,
NH)
3a
3b
3c
3d
3e
3f
6.92-8.15
(8H, m)
2.64 (3H, s,
CH3)
3.84 (3H, s, p-
OCH3)
13.41 (br, OH)
14.76 (1H, br, NH)
16.14 (br, tautomeric
NH)
6.99–8.30
(8H,m)
2.41–2.95 (3H,
CH3)
3.75–4.12 (3H, p-
OCH3)
9.36 (1H,
OH)
9.29 (1H,
NH)
6.92-8.16
(8H, m)
2.62 (3H, s,
CH3)
13.56 (br, OH)
14.72 (1H, br, NH)
16.10 (br, tautomeric
NH)
7.45–8.60
(8H,m)
2.43–2.84 (3H,
9.20 (1H,
OH)
9.42 (1H,
NH)
CH3)
6.92-8.07
(8H, m)
2.65 (3H, s,
CH3)
2.39 (3H, s, p-
CH3)
13.46 (br, OH)
14.75 (1H, br, NH)
16.10 (br, tautomeric
NH)
7.48–8.32
(8H,m)
2.43–2.98 (3H,
CH3)
2.11–2.61 (3H, p-
CH3)
9.38 (1H,
OH)
9.34 (1H,
NH)
6.92-8.69
(8H, m)
2.66 (3H, s,
CH3)
13.66 (br, OH)
14.73 (1H, br, NH)
16.19 (br, tautomeric
NH)
7.49 - 8.78
(8H,m)
2.46–2.87 (3H,
9.73 (1H,
OH)
9.64 (1H,
NH)
CH3)
7.08-8.02
(8H, m)
2.61 (3H, s,
CH3)
3.89 (3H, s, m-
OCH3)
13.50 (br, OH)
14.70 (1H, br, NH)
16.05 (br, tautomeric
NH)
7.03–8.32
(8H,m)
2.45–3.01 (3H,
CH3)
3.69–4.08 (3H, m-
OCH3)
9.38 (1H,
OH)
9.35 (1H,
NH)
6.92-8.14
(8H, m)
2.65 (3H, s,
CH3)
13.59 (br, OH)
14.70 (1H, br, NH)
16.06 (br, tautomeric
NH)
-7.49–8.33
(8H,m)
2.45–2.99 (3H,
9.38 (1H,
OH)
9.41 (1H,
NH)
3g
3h
3i
CH3)
6.93-8.08
(8H, m)
2.65 (3H, s,
CH3)
2.38 (3H, s, m-
CH3)
13.49 (br, OH)
14.71 (1H, br, NH)
16.08 (br, tautomeric
NH)
7.49–8.33
(8H,m)
2.45–3.02 (3H,
CH3)
2.01–2.59 (3H, m-
CH3)
9.38 (1H,
OH)
9.20 (1H,
NH)
6.91-8.09
(8H, m)
2.59 (3H, s,
CH3)
13.67 (br, OH)
14.40 (1H, br, NH)
15.90 (br, tautomeric
NH)
7.51–8.35
(8H,m)
2.30–2.70 (3H,
9.38 (1H,
OH)
9.40 (1H,
NH)
CH3)
7.03-8.27
(8H, m)
2.59 (3H, s,
CH3)
3.98 (3H, s, o-
OCH3)
13.46 (br, OH)
14.22 (1H, br, NH)
15.65 (br, tautomeric
NH)
7.07–8.32
(8H,m)
2.44–2.98 (3H,
CH3)
3.71–4.21 (3H, o-
OCH3)
9.40 (1H,
OH)
9.38 (1H,
NH)
3j
7.57-8.28
(8H, m)
2.58 (3H, s,
CH3)
13.44 (br, OH)
14.37 (1H, br, NH)
15.89 (br, tautomeric
NH)
7.46–8.33
(8H,m)
2.50–3.02 (3H,
9.37 (1H,
OH)
9.42 (1H,
NH)
3k
3l
CH3)
7.34-8.27
(8H, m)
2.60 (3H, s,
CH3)
2.35 (3H, s, o-
CH3)
13.52 (br, OH)
14.30 (1H, br, NH)
15.80 (br, tautomeric
NH)
7.50–8.33
(8H,m)
2.47–2.92 (3H,
CH3)
2.29–2.88 (3H, o-
CH3)
9.39 (1H,
OH)
9.36 (1H,
NH)
a Abbreviations: s, singlet, m, multiplet; b, broad.

ACCEPTED MANUSCRIPT
25
Table 4 Frontier Orbital Analysis
Dye
no
ω (eV-
ELUMO
(eV)
EHOMO
(eV)
∆EHOMO-
LUMO (eV)
1
I (eV)
A (eV)
χ (eV)
 (eV)
S (eV-1)
μ (eV)
)
495-
3a
-3.467 -6.408 2.941 6.408 3.467 4.937 1.470 0.340 -4.937 578
452-
3b
3c
3d
3e
3f
-2.972 -5.687 2.715 5.687 2.972 4.330 1.358 0.368 -4.330 522
443-
-3.205 -6.092 2.887 6.092 3.205 4.648 1.443 0.346 -4.648 496
444-
-3.045 -5.891 2.846 5.891 3.045 4.468 1.423 0.351 -4.468 490
482-
-3.368 -6.342 2.975 6.342 3.368 4.855 1.487 0.336 -4.855 554
452-
-3.058 -5.932 2.874 5.932 3.058 4.495 1.437 0.348 -4.495 498
440-
3g
3h
3i
-3.237 -6.172 2.936 6.172 3.237 4.704 1.468 0.341 -4.704 492
438-
-3.065 -5.948 2.883 5.948 3.065 4.506 1.442 0.347 -4.506 498
438-
-3.270 -6.330 3.060 6.330 3.270 4.800 1.530 0.327 -4.800 478
561-
3j
-2.943 -5.718 2.776 5.718 2.943 4.330 1.388 0.360 -4.330 501
438-
-3.139 -6.067 2.928 6.067 3.139 4.603 1.464 0.342 -4.603 475
444-
3k
3l
-3.055 -5.946 2.891 5.946 3.055 4.500 1.445 0.346 -4.500 490

ACCEPTED MANUSCRIPT
Table 5 Theoretical electronic absorption spectra of title compound (absorption wavelength using TD-DFT/B3LYP/6-311G(d,p) method
in experimental, solvent (chloroform) and gas phase.
Dye DMSO
no
DMF
A.nitril
Methanol
A.acid
Chloroform
Chloroform
Major
Minor
Exp. Calc.
Exp. Calc.
Exp. Calc.
Exp. Calc.
Exp. Calc.
Exp. Calc.
contributiona
contributiona
362,
460
570
359,
460
576
354,
438
570
317,
427
569
348,
439
570
365,
482
572
H-1->LUMO
(14%), HOMO- (5%)
>LUMO (79%)
H-4->LUMO
3a
354,
460
519
481
353,
449
520
475
349,
450
517
485
349,
431
517
475
349,
453
521
480
353,
486
525
478
HOMO-
>LUMO (91%) (3%)
H-3->LUMO
3b
3c
341,
453
340,
458
332,
440
333,
433
332,
443
341,
472
H-3->LUMO
(12%), HOMO- (4%), H-1-
>LUMO (75%) >L+1 (4%)
H-1->LUMO
337,
445
473
338,
444
475
332,
443
470
331,
429
462
331,
444
474
340,
476
482
H-4->LUMO
(13%), H-1-
>LUMO
H-1->L+1
(3%), HOMO-
>L+1 (3%)
3d
(12%), HOMO-
>LUMO (65%)
337,
454
552
490
337,
454
553
493
333,
447
547
494
307,
434
548
493
325,
427
552
498
347,
477
558
501
H-1->LUMO
(13%), HOMO- (5%)
>LUMO (81%)
H-4->LUMO
3e
3f
339,
451
338,
445
330,
439
328,
422
326,
443
336,
470
H-4->LUMO
(11%), HOMO- (3%)
>LUMO (78%)
H-2->LUMO

ACCEPTED MANUSCRIPT
27
339,
452
473
480
457
498
450
338,
448
470
468
455
495
451
332,
438
468
483
455
497
450
331,
427
470
486
451
493
451
330,
440
469
483
453
501
452
338,
465
475
478
457
504
458
H-3->LUMO
(14%), HOMO- (3%), H-1-
>LUMO (72%) >L+1 (5%)
H-1->LUMO
3g
3h
3i
337,
451
336,
444
330,
440
329,
421
328,
441
335,
465
H-4->LUMO
(11%), HOMO- (3%), H-1-
>LUMO (77%) >L+1 (3%)
H-1->LUMO
340,
446
341,
460
333,
438
333,
434
331,
435
340,
465
H-3->LUMO
(16%), HOMO- (6%), H-1-
>LUMO (68%) >L+2 (2%)
H-1->L+1
344,
441
351,
435
339,
435
350,
426
334,
436
347,
476
H-1->LUMO
(10%), HOMO- (5%)
>LUMO (80%)
H-4->LUMO
3j
338,
442
337,
440
332,
436
330,
435
330,
438
340,
467
H-3->LUMO
(22%), H-1-
>LUMO
H-4->LUMO
(2%), HOMO-
>L+1 (7%)
3k
(23%), HOMO-
>LUMO (37%)
334,
438
474
339,
434
478
326,
432
468
321,
426
473
325,
432
472
331,
463
477
H-4->LUMO
(13%), H-1-
>LUMO
H-1->L+1
(3%), HOMO-
>L+1 (3%)
3l
(12%), HOMO-
>LUMO (65%)
a H: Homo, L: Lumo

ACCEPTED MANUSCRIPT
Table 6 Absorption maxima of dyes 3a-l in acidic and basic solutions

max (nm)
Methanol
+
Methanol
+
Chloroform
+
Dye no
3a
3b
3c
Methanol
317, 427
349, 431
333, 433
331, 429
307, 434
328, 422
331, 427
329, 421
333, 434
350, 426
330, 435
321, 426
Chloroform
365, 482
353, 486
341, 472
340, 476
347, 477
336, 470
338, 465
335, 465
340, 465
347, 476
340, 467
331, 463
Acetic acid
348, 439
349, 453
332, 443
331, 444
325, 427
326, 443
330, 440
328, 441
331, 435
334, 436
330, 438
325, 432
KOH
372, 497
HCl
342, 438
piperidine
368, 495
353, 490
364, 495
348, 480
351, 502
350, 457
335, 441
330, 445
320, 430
362, 494
362, 498
341, 482
348, 507
340, 479
345, 484
341, 472
344, 486
350, 488
342, 475
337, 477
3d
3e
350, 399, 482 320, 446
3f
342, 488
340, 477
340, 482
352, 491
339, 472
332, 476
330, 438
330, 437
335, 437
338, 439
332, 440
320, 430
3g
3h
3i
3j
3k
3l

ACCEPTED MANUSCRIPT
29
Graphical abstract
O
N
O
O
O
_
+
N
N
N
Cl
N
N
N2
N
N
NH2
OH
X
NaNO2/HCl
CH3COOH
X
OH
X
NH
NH
H3C
NH
N
H3C
N
H3C
N