A combined experimental and DFT investigation of mono azo thiobarbituric acid based chalcone disperse dyes

Article abstract of DOI:10.1016/j.dyepig.2020.108887

A number of monoazo dyes were synthesized by the reaction of 4-aminoacetophenone with different substituted benzaldehydes to give a new series of chalcone derivatives. The diazonium salts of these chalcones then allowed to react with thiobarbituric acid to produce the appropriate azo dye. The structures of the newly synthesized dyes were assigned by IR, NMR spectral data. IR study confirmed the existence of azo-dioxothioxo tautomer in the solid phase while ¹H NMR study indicated the predominance of azoenol-oxothioxo or hydrazo-dioxothioxo tautomers. The geometries of the azo and hydrazo tautomeric forms and their electronic absorption of the dyes were optimized at B3LYP/6-311G level of theory. All the azo compounds were evaluated for their dyeing performance on polyester fibers, and PET. All the synthesized dyes gave moderate to excellent fastness properties on PET fiber. The effects of the nature of the substituents on the color and dyeing properties of these dyes have been evaluated. The mechanism of dyeing polyester fiber was discussed.

Full text of DOI:10.1016/j.dyepig.2020.108887

Dyes and Pigments 185 (2021) 108887
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: http://www.elsevier.com/locate/dyepig
A combined experimental and DFT investigation of mono azo thiobarbituric
acid based chalcone disperse dyes
,
Alaa Z. Omara *, Mona N. Mahmouda, Samir K. El-Sadanya, Ezzat A. Hameda,
,
b
Mohamed A. El-atawya
a Chemistry Department, Faculty of Science, Alexandria University, P.O. 426 Ibrahemia, Alexandria, 21321, Egypt
b Chemistry Department, Faculty of Science, Taibah University, Yanbu, 46423, Saudi Arabia
A R T I C L E I N F O
A B S T R A C T
Keywords:
A number of monoazo dyes were synthesized by the reaction of 4-aminoacetophenone with different substituted
benzaldehydes to give a new series of chalcone derivatives. The diazonium salts of these chalcones then allowed
to react with thiobarbituric acid to produce the appropriate azo dye. The structures of the newly synthesized dyes
were assigned by IR, NMR spectral data. IR study confirmed the existence of azo-dioxothioxo tautomer in the
solid phase while 1H NMR study indicated the predominance of azoenol-oxothioxo or hydrazo-dioxothioxo
tautomers. The geometries of the azo and hydrazo tautomeric forms and their electronic absorption of the
dyes were optimized at B3LYP/6-311G level of theory. All the azo compounds were evaluated for their dyeing
performance on polyester fibers, and PET. All the synthesized dyes gave moderate to excellent fastness properties
on PET fiber. The effects of the nature of the substituents on the color and dyeing properties of these dyes have
been evaluated. The mechanism of dyeing polyester fiber was discussed.
Disperse dye
Azo dye
Thiobarbituric acid
Chalcone
DFT
Fastness properties
1. Introduction
antitumor agent [17].
The C5–H bond in thiobarbituric acid is sufficiently acidic where in
The synthetic colors are widely applied in many fields of modern
industries, such as textiles, leather, paper and in the production of food
and hair dye [1]. The most common synthetic azo dyes used for dyeing
presence of base, it couples with diazonium salts, most often aqueous
sodium acetate [18]. Azo colorants containing amino and hydroxyl
substituents ortho or para to the azo groups can exist as a mixture of azo
and hydrazo tautomers. While azo–hydrazo tautomers are quite inter-
esting from a theoretical viewpoint as the two tautomers have different
technical properties [18]. The aim of the present study is attempting to
design azo thiobarbituric acid based chalcone derivatives with some
application to dye fiber and predict the mechanism of dyeing if any. The
study will extend to compute the absorption of the synthesized dyes
using the Density Functional Theory (DFT).
fabrics and textiles were usually strongly colored due to π-delocalization
i.e. the color intensity as well as the interaction of azo dyes with fibers
depend on the structure of dyes and the dyed materials [2–7]. Disperse
dyes contain azo chromophore are substantially water-insoluble i.e.
non-ionic dyes and generally applied to hydrophobic fibers e,g, poly-
ester, cellulose acetate, and nylon [8].
It has been reported that the introduction of the chalcone group to
the azo compound will increase the conjugation and gave brighter hues
on acetate, nylon and polyester fibers [3] but they didn’t applicable on
cotton fiber. It has been found that thiobarbituric acid derivatives have
more pharmacological activity due to the presence of sulphur. Because
of the simple application and of the acid character, the thiobarbiturates
were used as valuable reagents in organic syntheses of biological activity
[9–11] such as antiallergic [12], antifungal [13,14], antibacterial,
antichlamydial, antiviral and immunomodulating activity [15,16] and
2. Results and discussion
2.1. Chemistry
The chalcones azo thiobarbituric acid derivatives were synthesized
by condensation of 4-aminoacetophenone 1 with some arylaldehyde 2a-
k to give 1-(4-aminophenyl)-3-arylprop-2-enone 3a-k, followed by
* Corresponding author.
E-mail addresses: Alaazaki@alexu.edu.eg (A.Z. Omar), mona.nabih@alexu.edu.eg (M.N. Mahmoud), Samir.elsadany@alexu.edu.eg (S.K. El-Sadany), ezzat.awad@
alexu.edu.eg (E.A. Hamed), mohamed.elatawi@alexu.edu.eg (M.A. El-atawy).
https://doi.org/10.1016/j.dyepig.2020.108887
Received 19 May 2020; Received in revised form 31 August 2020; Accepted 24 September 2020
Available online 28 September 2020
0143-7208/© 2020 Elsevier Ltd. All rights reserved.

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
diazotization which then coupled with thiobarbituric acid to give the
water insoluble disperse dyes Chalcone Azo Thiobarbituric acid (CAT)
4a-k, Scheme 1.
thiophene ring.
The 1H NMR spectra of CAT dyes 4a-k show characteristic two
doublet signals for α, β-protons which coalesced with aromatic protons.
As reported earlier [18], CAT dyes 4a-k can exist in three main
tautomeric forms, namely CAT azo-dioxothioxo tautomer I, CAT
hydrazo-dioxothioxo tautomer II and CAT azo-enol-oxothioxo tautomer
III as shown in Scheme 2. Tautomerism is not only important to chemists
but also to the dyestuff manufacturer. Tautomers not only have different
colors, but also have different properties, e.g. light fastness.
The FT-IR spectra of CAT dyes 4a-k showed two intense carbonyls
Obviously, in all cases the doublet for CHβ appeared around δ 8.02–7.60
ppm, which more deshielded than CHα refers to the effect of adjacent
phenyl ring that bonded to β-carbon atom. The doublet in the region δ
8.02–7.60 ppm with J coupling constant 14.6–15.6 Hz to H-β, indicates
that the ethylene moiety in the enone linkage is in the trans-conforma-
tion. The optimized 4a, geometry as well as 0◦ dihedral angle of H
α-
–
C
C-Hβ stated that Hα and Hβ are existing in the s-trans conformation as
–
ꢀ 1
(C O) peaks at 1666-1651 and 1712-1705 cm
(see experiment),
suggested from 1HNMR study [20].
–
–
while the hydroxyl group peak of the thiobarbituric moiety disappeared.
Therefore, IR results suggest that the CAT dyes 4a-k in the solid phase
are predominantly exist in either azo-dioxothioxo tautomer I or CAT
hydrazo-dioxothioxo II rather than CAT azo-enol-oxothioxo III tauto-
mers, Scheme 2. On the other hand, the absence of peaks attributable to
R. E. Stuckey reported that the thiobrbituric acid may be charac-
terized by equilibrium among thiobarbituric acid in monoenol-
oxothioxo, dienol-thioxo and thiodienol tautomers [21,22]. Actually,
the 1H NMR measurements indicate that the synthesized dyes exist in
thioldioxo IV, enolthioloxo V and dienolthiol tautomers VI are rejected,
Fig. 1, and CAT dyes 4a-4c and 4f-4j exist in the azo-enol-oxothioxo
tautomer III while dyes 4d-4e and 4k exist in hydrazo-dioxothioxo
tautomer II, Scheme 2.
imino group (C N) while the presence of weak peaks at ʋ cmꢀ 1 1519-
–
–
–
1496 for azo group (N N) [19] excluded the CAT
–
hydrazo-dioxothioxo tautomer II and suggests that the solid phase of
dyes 4a-k exist as CAT azo-dioxothioxo tautomer I. The FT-IR spectra
also showed peaks at ʋ cmꢀ 1 3471-3109, assigned to NH group,
3079-3000 cmꢀ 1 assigned to aromatic C–H, while aliphatic C–H peaks
appear at ʋ cmꢀ 1 2924–2862. The intense peaks at ʋ cmꢀ 1 1350–1334
2.2. Electronic Absorption Spectra and substituent effect
cmꢀ 1 correspond to thiocarbonyl (C S).
–
–
The computational results of absorptions and the observed colors of
mono azo disperse CAT dyes 4a-k are compared with the experimental
ones. The color strength values of dyeing process associated with some
molecular descriptors are examined.
Inspection of the 1H NMR spectra of CAT dyes 4a-4c and 4f-4j
showed the existence of two exchangeable broad singlet signals in the
downfield region; one resonates in the range δ 12.5–12.54 ppm is
attributed to two NH protons at the 1-position and 3-position of the
thiobarbituric acid moeity. While, the more deshielded proton in the
range δ 14.17–13.98 ppm, was attributed to one OH proton that forms
hydrogen bonding with the azo group. Also, the absence of a signal for
the methine proton (CH) suggests the existence of CAT dyes 4a-4c and
4f-4j in the azo-enol-oxothioxo tautomer III. While, 1H NMR spectra of
CAT dyes 4d-4e and 4k exhibit only one exchangeable broad singlet
signal in the range δ 12.88–12.80 ppm attributed to three NH protons,
indicating that these dyes exist in hydrazo-dioxothioxo tautomer II. The
low-field broad singlet peaks of NH protons for all synthesized dyes, 4a-
k is presumably due to intramolecular hydrogen bond between carbonyl
groups and NH of hydrazo-dioxothioxo tautomer II or between azo and
OH of azo-enol-oxothioxo tautomer III, Fig. 3.
The computed absorption values of compounds 4a-k using B3LYP/6-
311G are ranged in the region of (403–427 nm) which nearly lie in the
region of violet color absorption (400–435 nm), whereas, the observed
color was yellow and yellowish-orange, Table 1.
The data in Table 1 shows that CAT dyes 4b-k have slight shift in λ
max than the unsubstituted one 4a, Fig. 2. This indicates that the posi-
tions of absorption bands are slightly dependent of the nature and po-
sition of the substituent on the aryl group of the chalcone moiety. Also,
Table 1 showed that the computed absorption values of compounds 4a-k
(403–427 nm) are quit similar values compared with the experimental
ones.
Each of the CAT dyes 4a-k gave two absorption bands in the region λ
nm 274.65–342.88 and 430.96–439.65 nm. These absorption bands
The methyl groups of compounds 4f and 4j were displayed in 1H
NMR at δ 2.36 and 2.44 ppm, respectively, while their 13C APT NMR
exhibited signals at δ 20.93 and 19.37 respective to their methyl carbon
atoms. The methoxy and thiomethoxy groups in compounds 4g and 4h
were appeared more deshielded singlet signals at δ 3.82 and 2.52 ppm in
1H NMR spectra, while their 13C APT-NMR spectra signals appeared at δ
55.41 and 14.17 ppm. Dye 4k showed a triplet and two doublets signals
at δ 7.19 and 7.79 ppm corresponding to aromatic protons in the
mainly originate from the
π →π* electronic transition involving the
π
-electron system of the molecule and n →π* from ground to excited
state, respectively. Except, dye 4h and 4k have only one absorption
bands at λ 437.48 and 436.24 nm, respectively, mainly are due to n →π*
transition.
Examination of the results reported in Table 1, reveals that the
introduction of either electron-donating or electron-withdrawing of the
aryl ring containing chalcone moiety result in bathochromic shifts for
both absorption bands compared to the unsubstituted dye 4a (Ar =
Scheme 1. Synthetic pathway of CAT dyes 4a-k.
2

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Scheme 2. Possible tautomeric form of CAT dyes 4a-k.
slight hypsochromic shifts. This is because protonation of azo group
causes isolation the donor-acceptor interplay between chalcone and
thiobarbituric moiety, Scheme 3.
2.4. Fastness properties
Washing, perspiration, scorch and light fastness have been done by
using standard procedure [23,24], The physical data for the dyed
polyester fibers were collected in Table 2. Wash fastness property de-
pends mainly upon the solubility of dye in water and what type of
linkage present between the dye molecule and fabrics whereas light
fastness is the degree to which a dye resists fading due to light exposure.
Scorch fastness is the most significant requirement of the dyed polyester
fabrics, as the migration of the dye molecules of disperse dyes to poly-
ester fabrics are totally dependent on the heat treatment. All of
measured properties were assessed with gray scale from 1—poor to
6—excellent [25].
Fig. 1. Different tautumeric form of thiobarbituric acid moiety.
C6H5). The bathochromic shift can be attributed to more conjugation by
introducing a substituent with different nature and position, except, dye
4i (Ar = 2-ClC6H4) shows hypsochromic shifts for
π →π* band, dyes 4e
(Ar = 4-BrC6H4) and 4g (Ar = 4-CH3OC6H4) exhibit hypsochromic shift
for n →π* and whereas dye 4c (Ar = 3-NO2C6H4) shows hypsochromic
shifts for both bands, Fig. 2.
2.3. Acidochromic effects
The fastness ratings show that the disperse CAT dyes (4a-4c and 4e-
4k) displayed good to very good fastness levels to washing, this is
because of these dyes are hydrophobic, so high washing fastness ratings
are expected. CAT dyes (4a-4c and 4e-4k) exhibited moderate fastness
levels to perspiration and very good fastness levels to scorch and light
fastness.
The presence of basic nitrogen atom of azo group, and an acidic
tautomeric proton in the pyrimidine ring in the dyes 4a-k prompted us
to study the possibility of protonation and deprotonation of these CAT
dyes in DMF, by using 0.1 M hydrochloric acid and 0.1 M sodium hy-
droxide Figs. 3 and 4, respectively. The effects of the acid and base on
the absorption maxima of the dye solutions s are shown in Table 1. It
shows that the absorption of the dyes in DMF are quite sensitive to pH
change.
2.5. Dye exhaustion
The absorption maxima of the CAT azo dyes 4a-k in DMF showed
bathochromic shift due to deprotonation upon addition of NaOH s, that
leads to increase in donor-acceptor interplay between the enolate
functionality and the chalcone moiety (the anionic form for dye 4a-k).
While, addition of hydrochloric acid to dye solutions in λmax showed
The uptake of our disperse azo dyes by fiber polyester was measured
by sampling the dye bath before and after the dyeing [26]. The con-
centration (g/l) of the dye bath was measured on (pg instruments T80+)
UV/visible spectrophotometer at λ
of the corresponding dye. The
max
percentage of the individual dye exhaustion on PET (% E) was calculated
Table 1
Experimental and computed absorption maxima of CAT dye 4a-k in DMF, DMF/0.1 M NaOH and DMF/0.1 M HCl.
Dye no.
Ar
Observed color
DMF λ (nm)
λ (nm)
Experimental
Computational
DMF + NaOH
DMF + HCl
4a
4b
4c
4d
4e
4f
C6H5
yellow
orange
orange
orange
yellow
orange
yellow
yellow
orange
orange
yellow
308.76, 435.00
317.14, 430.96
274.65, 432.51
310.03, 439.65
315.59, 434.37
310.62, 437.43
342.88, 434.68
437.48
408.43
403.60
409.49
427.18
409.05
410.77
404.33
406.57
409.79
410.33
424.36
309.07, 464.77
318.07, 446.47
274.65, 447.09
310.62, 467.25
313.73, 465.70
312.49, 465.08
340.40, 462.60
360.56, 467.25
299.77, 476.56
314.04, 466.94
471.91
314.66, 424.76
319.62, 424.76
276.20, 423.52
318.07, 423.83
319.31, 425.07
315.59, 424.76
332.65, 427.55
337.61, 429.72
312.80, 425.07
318.38, 424.76
424.76
4-NO2 C6H4
3-NO2 C6H4
4-Cl C6H4
4-Br C6H4
3-CH3 C6H4
4-OCH3 C6H4
4-CH3S C6H4
2-Cl C6H4
2-CH3 C6H4
2-Theinyl
4g
4h
4i
303.80, 437.17
310.62, 435.93
436.24
4j
4k
3

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Fig. 2. Absorption Spectra of CAT dye 4a-k in DMF.
Fig. 3. Absorption Spectra of CAT dye 4a-k in DMF and 0.1 M HCl.
using Equation (1) [27]. The CAT dyes (4a-4c and 4e-4k) showed
relatively moderately to good exhaustion (%) compared onto PET, while
dye 4g displayed excellent exhaustion (%), Table 3.
correlation coefficient and positive slope of the plot indicating that
electron withdrawing increases while that with donating effect de-
creases dye exhaustion, Table 3. Also the magnitude of
effect on dye exhaustion of polyester fiber.
ρ* indicates poor
C1 ꢀ C
(%E =
2 100)
1
C1
2.6. Color strength
Attempts are made to apply Hammett equation for 3- and 4- sub-
stituents and Taft equation for 2-substituents to know the effect of these
substituents on dye exhaustion of dyes 4a-j on polyester fiber. Hammett
plot indicates poor dependence of dye exhaustion on the nature of
substituents, however, on removing 3-NO2 from the plot gives good
straight line with negative slope as appeared from their correlation co-
efficient. The negative slop indicates that electron withdrawing sub-
stituents decrease while electron donating substituents increase dye
exhaustion. On applying Taft equation for ortho substituents a good
Spectral reflectance measurements on the dyed fabrics, Fig. 5, were
carried out using a Jasco - UV/vis/NIR-spectrometer V-570 (1) over
190–2500 nm. The color strength of the dyed fabrics, Table 4, expressed
in terms of K/S values at λmax was determined using the Kubelka-Munk
[28] Equation (2):
/
/
K
S = (1 ꢀ R)2 2R
2
4

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Fig. 4. Absorption Spectra of CAT dye 4a-k in DMF and 0.1 M NaOH.
Scheme 3. Protonated and deprotonated structure of CAT dyes 4a-k in DMF.
Where R is the decimal fraction of the reflection of the dyed fabric; K the
absorption coefficient; and S the scattering coefficient.
dioxothioxo tautomer I is the more stable one and has a lower relative
energy (ΔE = 0.07 kcalmol-1) than CAT azo-enol-oxothioxo III tautomer
which it has a lower energy (ΔE = 0.716 kcalmol-1) than CAT hydrazo-
dioxothioxo II tautomer, Fig. 6.
Data in Table 4 reveals that the color strengths (K/S) of dyed fabrics
lie in the same range (0.702–1.769) indicating poor dependence on the
nature and position of substituents and this apparently noticed from the
hues of the fabrics treated with the CAT azo dyes which vary from yellow
to yellowish-orange. Dyed fabric with CAT dye 4i (X ¼ 2-Cl) showed the
high K/S value while CAT dye 4c (X ¼ 3-NO2) showed the lowest color
strength value.
2.7.1. Quantum chemical parameters
The DFT method were used to calculate the descriptor parameters
[29–32] of both tautomers II and III as well as to predict the mechanism
of dyeing process (see Table 6).
The molecular descriptors were calculated by using B3LYP/6-311G
level for investigation of dyeing efficiencies of 4a-k given in Scheme
1. The calculated molecular descriptors were given in Table 6 at gas
phase.
2.7. Theoretical study and the molecular descriptors
Theoretical analyses have been applied to calculate the tautomeri-
zation energy, Table 5, for the three tautomers of CAT dye 4a. In that
way, by using quantum mechanical modeling (DFT method), optimiza-
tion was performed on the tautomeric forms.
According the Koopman’s theorem, as can be seen from Equations
(3) and (4), ELUMO and EHOMO of any chemical species have been asso-
ciated with its ionization energy and electron affinity values [29–32],
Table 6.
The geometric optimization of dye 4a showed that the CAT azo-
5

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Table 2
Fastness properties of azo disperse CAT dyes (4a-4c and 4e-4k) on polyester fibers (PET).
Dyed polyester fibers
Dye no.
Wash fastness (1–6)
Perspiration fastness (1–6)
Scorch fastness (1–6)
Light fastness (1–6)
4–5
Alt.
5
SC
3
SP
acidic
alkaline
4a
4–5
3–4
3–4
4–5
4b
4c
5
5
3–4
4–5
4–5
3
3–4
3–4
4–5
4–5
4–5
4–5
3
3–4
4e
5
3
4–5
3–4
3–4
4–5
4–5
4f
5
5
3
3
4–5
4–5
3–4
3–4
3
4–5
4–5
4–5
4–5
4g
3–4
4h
5
3
4–5
3–4
3–4
4–5
4–5
4i
4j
5
5
3–4
4–5
4–5
3–4
3–4
3–4
3–4
4–5
4–5
4–5
4–5
3
4k
5
3
4–5
3–4
3–4
4–5
4–5
Alt. = alteration, SC = staining on cotton, SP = staining on polyester fiber, PET = polyethylene terephthalate.
μ
= ꢀ
χ
7
8
Table 3
Dye exhaustion of azo disperse CAT dyes (4a-4c and 4e-4k) on polyester fabrics
IP ꢀ EA
(PET).
Dye
no.
η
=
=
2
Dye
Application of
Hammett
σ
Application of
Taft Equation
(C1 ꢀ C2)X
σ *
Exhaustion
(%E =
C1 ꢀ C
1
η
Equation
σ
9
( C1 ꢀ C2)
(C1 ꢀ C2)
2 *100)
( C1 ꢀ C2)X
CH3
C1
H
Parr et al. have defined electrophilicity index as a measure of energy
4a
4b
4c
4e
4f
35.71%
31.21%
63.41%
61.21%
61.82%
80.15%
64.51%
49.57%
35.46%
33.23%
1.000
0.868
1.721
1.482
1.893
2.458
1.722
0.00
0.982
0.49
lowering due to maxima electro flow between donor and acceptor [35].
0.78
0.71
μ2
0.23
ω
=
10
2
η
ꢀ 0.07
ꢀ 0.27
0.00
4g
4h
4i
The molecular descriptors were calculated by using B3LYP/6-311G
level for investigation of dyeing efficiencies of 4a-k given in Scheme 1.
1.370
1.000
2.96
0.00
The calculated molecular descriptors were given in Table 6 at gas phase.
4j
4k
ρ
= ꢀ 0.274 (R2
=
ρ
* = 0.0503
E
HOMO is a parameter associated with the electron donating ability of
0.61) 6 points
(R2 = 0.97) 3
molecule [36,37]. If the EHOMO increases, electron transfer tendency will
increase to the LUMO of appropriate receptor molecules. The molecule
having the higher EHOMO indicates the higher dyeing strength. ELUMO is a
measure of electron accepting ability of chemical species. ELUMO de-
termines the polarizability of the compound i.e. the ability to be dis-
torted by an electric field, and hence LUMO level receives electrons.
Experimental and theoretical studies related to dyeing strength show
that increasing of ELUMO decreases the dyeing efficiency of molecules.
The separation energy, ΔE is an important parameter as a function of
dyeing strength of the molecule. The larger values of the HOMO-LUMO
energy gap and chemical hardness will provide low dyeing for fiber. The
dyeing efficiencies orders according to ΔE gap will be similar to each
other.
ꢀ 0.414 (R2
=
points
0.99) 5 points
(except 3-NO2)
IP = ꢀ EHOMO
EA = ꢀ ELUMO
3
4
Energy gap (ΔE) [33], absolute electronegativity (χ), chemical po-
tential (
μ
), absolute hardness (
η
) and absolute softness (
σ
) are given by
Equations (5-9) [34].
ΔE = EHLUMO ꢀ EHOMO
5
6
Chemical hardness is defined as resistance to electron transfer. The
larger values of the chemical hardness will provide low dyeing for fiber.
IP + EA
χ
=
2
6

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Fig. 5. Reflectance values of the dyed fabrics.
the molecule that known as electrophilicity index (
ω
). The electrophi-
Table 4
licity index is a descriptor that can represent the dye strength of the
chemical species. The global electrophilicity index of the molecule al-
lows quantitative classification of its reactivity [41–45]. The electro-
philicity index shows the ability of the electron-accepting ability [46].
Table 6 points out that each parameter exhibits poor effect on dye
exhaustion as indicated from its slope value and correlation coefficient.
Reflectance (%) and color strength (K/S) value of dyed fabrics at λmax
.
Dyed Fabric
Reflectance (%)
K/S
4a
4b
4c
4e
4f
24.059
26.643
32.786
26.684
26.204
32.149
30.292
18.750
21.328
27.224
1.198
1.009
0.702
1.007
1.039
0.716
0.802
1.769
1.443
0.972
However, parameters ΔE(e), IP, EA,
decrease dye exhaustion. While, (eV),
χ
and with negative slopes
ω
μ
η
, S and μ (D) parameters with
4g
4h
4i
positive slopes increase dye exhaustion. Therefore, multiparameters
correlation as well as local reactivity may give a concept of the dyeing
process.
4j
4k
2.8. Mechanism of dyeing process
Table 5
1H NMR shows that dyes CAT dye 4a-k in DMSO existing in the azo
enol-oxothioxo III or hydrazo dioxothioxo II tautomers suggesting the
formation of hydrogen bonds between the carbonyl group of polyester
fiber and the HN< of thiobarbituric moiety of dyes at low temperature
Fig. 7 [47].
Energy of tautomers I, II, III calculated by the density Functional Theory (DFT)
computational analysis [B3LYP/6-311G].
Tautomer
Energy kcal/mol
Azo-dioxothioxo tautomer
Hydrazo-dioxothioxo tautomer
Azo-enoloxothioxo tautomer
I
205.008
205.794
205.078
II
III
Transfer of dye onto fiber surface is occurred in slightly basic DMF
and slightly acidic medium through exhaustive process without any
additives at low-medium temperature with stirring few minutes clock-
wise followed by stirring anticlockwise. This environments promote
vibrational activity and accelerate the migration of the surface of the
fiber. Thus a layer is creating called ‘Barrier.’ If the dye molecules are to
reach the fiber surface then the barrier should be broken which is done
by agitation. The second step is assembly of dye molecules at the fiber
surface leading to adsorption if the dye which is to be distributed is
retained by a surface.
The dyeing efficiencies orders according to
η
will be similar to each
other. Softness is the inverse of chemical hardness and represents high
dyeing strength. Therefore, soft molecules exhibit high electron
donating tendency and high adsorption effect. Exchange of the calcu-
lated
σ values for these compounds is:
Absolute electronegativity is taken into account as a chemical
descriptor in comparison of dyeing strength of fibers. It should be noted
that strong colour strength should have low electronegativity values.
Because dyeing strength with low electronegativity are tended to give
the electron. For a reaction of two systems with different electronega-
tivity the electronic flow will occur from the molecule with the lower
electronegativity towards that of higher value until the chemical po-
tentials are equal [38,39]. Chemical potential is the inverse of the
electronegativity. Therefore, the dyeing strength increases with
increasing of chemical potential. Chemical hardness and softness,
chemical potential are known as global reactivity descriptors [35].
Recently, Parr et al. have defined a new descriptor [40]. This
parameter is a numeric expression of the global electrophilic power of
When the temperature exceeds the glass transition temperature, the
heat motion of the molecular chain turns from a frozen state into violent
motion [48]. The diffusion starts because the fiber expands, thus dilating
the fiber gap, and allowing the disperse dye molecule to enter the
compact fiber molecules, Fig. 8. The final step is reached when the
temperature decreases, the pores of material are restored, so that the dye
molecules are fixed in the fiber. The disperse dye dyeing is generally
based on polyester fiber.
7

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Fig. 6. Geometrical optimization for three tautomers of CAT dye 4a.
Table 6
Quantum chemical parameters with B3LYP/6-311G level in gas phase of inhibitors.
Cpd
EHOMO
ELUMO
ΔE(e)
IP
EA
χ
μ(eV)
η
S
ω
μ
(D)
%E
4a
4b
4c
ꢀ 0.24385
ꢀ 0.25085
ꢀ 0.24836
ꢀ 0.25341
ꢀ 0.25215
ꢀ 0.24362
ꢀ 0.23316
ꢀ 0.2296
ꢀ 0.11934
ꢀ 0.13644
ꢀ 0.12911
ꢀ 0.1342
0.1245
0.1144
0.1193
0.1192
0.1223
0.1249
0.1164
0.1111
0.1236
0.1246
0.1123
¡0.076
0.0044
0.2439
0.2509
0.2484
0.2534
0.2522
0.2436
0.2332
0.2296
0.2440
0.2441
0.2396
¡0.336
0.1505
0.1193
0.1364
0.1291
0.134
0.1816
0.1936
0.1887
0.1938
0.1910
0.1812
0.1750
0.1741
0.1822
0.1817
0.1834
¡0.405
0.1699
ꢀ 0.1816
ꢀ 0.1936
ꢀ 0.1887
ꢀ 0.1938
ꢀ 0.1910
ꢀ 0.1811
ꢀ 0.1749
ꢀ 0.1740
ꢀ 0.1821
ꢀ 0.1817
ꢀ 0.1834
+0.405
0.0622
0.0572
0.0596
0.0596
0.0611
0.0624
0.0581
0.0555
0.0618
0.0623
0.0561
+0.405
0.1696
16.062
17.480
16.771
16.777
16.355
16.016
17.189
18.003
16.178
16.050
17.806
+0.342
0.0033
0.2648
0.3277
0.2987
0.3150
0.2983
0.2628
0.2631
0.2727
0.2684
0.2650
0.2994
¡0.096
0.1189
7.121
2.719
5.137
1.849
2.360
7.581
8.636
7.547
7.5851
6.941
5.402
+0.026
0.1083
35.71%
31.21%
63.41%
–
61.21%
61.82%
80.15%
64.51%
49.57%
35.46%
33.23%
4d
4e
4f
ꢀ 0.12987
ꢀ 0.11875
ꢀ 0.11681
ꢀ 0.11851
ꢀ 0.12035
ꢀ 0.11944
ꢀ 0.12725
0.1298
0.1187
0.1168
0.1185
0.1203
0.1194
0.1272
¡0.350
0.1367
4g
4h
4i
ꢀ 0.24397
ꢀ 0.24405
ꢀ 0.23957
4j
4k
slope
R2
0.1696
Fig. 7. The bonding mechanisms of polymer and disperse dye.
3. Conclusion
region. The FT-IR spectra of CAT dyes 4a-k suggested that in the solid
phase are predominantly exist in either azo-dioxothioxo tautomer or
CAT hydrazo-dioxothioxo. The 1H NMR study suggested the existence of
CAT dyes 4a-4c and 4f-4j in the azo-enol-oxothioxo tautomer. While,
The computational calculation and experimental absorptions of
chalcone azo thiobarbituric acid dyes 4a-k are nearly lie in the same
8

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
Fig. 8. A schematic image that explain the mechanism of diffusion.
CAT dyes 4d-4e and 4k existed in hydrazo-dioxothioxo tautomer. The
effects of the acid and base on the dye solutions showed that the ab-
sorption of the dyes in DMF are quite sensitive to pH change. The fast-
ness ratings showed that the disperse CAT dyes (4a-4c and 4e-4k)
displayed good to very good fastness levels to washing. The percentage
of the individual dye exhaustion on PET (% E) of the CAT dyes (4a-4c
and 4e-4k) showed relatively moderately to good exhaustion (%)
compared onto PET, while dye 4g displayed excellent exhaustion (%).
The Hammett and Taft relationships indicated poor dependence of dye
exhaustion on the nature of substituents. The mechanism of dyeing
process was proceeded by three steps. The first step is the transfer of dye
onto fiber surface, the second step is assembly of dye molecules at the
fiber surface leading to adsorption and the third step was ended by
diffusion.
mg) and concentrated sulfuric acid (3.0 mL at 0–5 ◦C). The mixture was
stirred for an additional 3 h and the temperature was not exceeded
0–5 ◦C. The formed diazonium salt solution was added dropwise to
thiobarbituric acid (2.0 mmol) dissolved in water contained KOH (2.0
mmol). The resulting solution was vigorously stirred at 0–5 ◦C for 4 h,
while the pH of the reaction mixture was maintained at 7–8 by simul-
taneous addition of potassium carbonate solution (0.5 M). The progress
of the reaction was monitored by TLC and then crude dyes were filtered,
washed with hot water for several times.
4.3.1. 5-((4-(3-phenylacryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4a)
Yellow crystals, 0.291 g (77%) yield; m.p.319 ◦C. UV: גmax (DMF)
435 nm and Ɛmax 32580 molꢀ 1dm3cmꢀ 1. IR (KBr): 3448 (N–H), 3340
–
–
–
–
(N–H), 3255 (N–H), 1712 (C O), 1658 (C O), 1604 (C C), 1504
–
–
(N N) and 1342 (C S) cmꢀ 1. 1H NMR (DMSO‑d6, 500 MHz): δ 14.13
–
–
–
–
4. Experimental
(1H, s, OH), 12.50 (2H, s, 2NH), 8.27 (2H, d, J = 8.5 Hz, 2Ar–H), 7.98
(1H, d, J = 15.6 Hz, –CH = ), 7.90 (2H, d, J = 3.7 Hz, 2Ar–H), 7.76 (3H,
m, 3Ar–H) and 7.46 (3H, m, 3Ar–H) ppm. 13C NMR (APT) (DMSO‑d6,
125 MHz): δ 187.59, 177.69, 145.07, 143.91, 134.72, 134.60, 128.96,
121.88, 120.39 and 116.79 ppm. C19H14N4O3S requires: C, 60.31; H,
3.73; N, 14.81% found: C, 60.51; H, 3.27; N, 14.42%
4.1. Instruments and apparatus
Melting points were determined by MEL-TEMP II melting point
apparatus in open glass capillaries. The IR spectra were recorded as
potassium bromide (KBr) discs on a Perkin-Elemer FT-IR (Fourier-
Transform Infrared Spectroscopy), Faculty of Science, Alexandria Uni-
versity. The NMR spectra were carried out at ambient temperature
(~25 ◦C) on a (JEOL) 500 MHz spectrophotometer using tetrame-
thylsilane (TMS) as an internal standard, NMR Unit, Faculty of Science,
Mansoura University. Elemental analyses were analyzed at the Regional
Center for Mycology and Biotechnology, Al-Azhar University, Cairo,
Egypt. The dyeing process was carried out in Chemical Laboratory of
Misr Beida Dyers S.A.E., Alexandria, Egypt.
4.3.2. 5-((4-(3-(4-nitrophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4b)
Orange crystals, 0.338 g (80%) yield; m.p.294 ◦C. UV: גmax (DMF)
442.13 nm and Ɛmax 23460 molꢀ 1dm3cmꢀ 1. IR (KBr): 3471 (N–H), 3379
2
–
–
–
(N–H), 3240 (N–H), 3078 (=Sp -H), 1705 (C O), 1658 (C O), 1597
–
ꢀ 1
–
–
–
–
–
–
(C C), 1504 (N N) and 1334 (C S) cm
.
1H NMR (DMSO‑d6, 500
MHz): δ 13.93 (1H,s, OH), 12.56 (2H, s, 2NH), 8.25 (2H, d, J = 8.8 Hz,
2Ar–H), 8.11 (2H, d, J = 8.7 Hz, 2Ar–H), 8.06 (1H, d, J = 15.6 Hz, =CH-
), 7.94 (2H, d, J = 8.6 Hz, 2Ar–H), 7.82 (1H, d, J = 15.6 Hz, =CH-) and
7.77 (2H, d, J = 8.7 Hz, Ar–H) ppm. 13C NMR (APT) (DMSO‑d6, 125
MHz): δ 187.38, 177.69, 154.27, 148.07, 141.24, 140.97, 134.15,
130.76, 129.92, 126.67, 124.96, 123.92 and 120.50 ppm. C19H13N5O5S
requires: C, 53.90; H, 3.09; N, 16.54% found: C, 54.11; H, 3.28; N,
16.85%
4.2. General method for synthesis of chalcone 3a-k
4-aminoacetophenone 1 (0.01 mol) was added dropwise (15 min) to
a cold solution of sodium hydroxide (0.03 mol) in aqueous ethanol (75
mL, 60%), while stirring at 20 ◦C. The reaction mixture was stirred for
additional 20 min. The desired substituted benzaldehyde 2a-j and
thiophene-2-carbaldehyde 2k (0.01 mol) was added dropwise (15 min)
with stirring for 3–4 h and temperature kept below 20 ◦C and was left
overnight in refrigerator. The separated solid was filtered, washed with
cold water and dried, then recrystallized from ethanol to give the cor-
responding 1-(4-aminophenyl)-3-aryl-propen-1-one 3a-k [49].
4.3.3. 5-((4-(3-(3-nitrophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4c)
Orange crystals, 0.329 g (78%) yield; m.p.270 ◦C. UV: גmax (DMF)
432.51 nm and Ɛmax 35640 molꢀ 1dm3cmꢀ 1. IR (KBr): 3471 (N–H), 3340
2
–
–
–
(N–H), 3232 (N–H), 3078 (=Sp -H), 1705 (C O), 1643 (C O), 1604
–
ꢀ 1
–
–
–
–
–
–
(C C), 1519 (N N) and 1342 (C S) cm
.
1H NMR (DMSO‑d6, 500
4.3. General method for synthesis of 5-((4-(3-arylacryloyl)phenyl)
diazenyl)-2-thioxodihydro-pyrimidine-4,6(1H,5H)-dione 4a-k
MHz): δ 13.87 (1H, s, OH), 12.57 (2H, s, 2NH), 8.21 (2H, m, =CH- and
Ar–H), 7.97 (2H, d, J = 8.5 Hz, 2Ar–H), 7.86 (1H, d, J = 15.6 Hz, =CH-)
and 7.73 (5H, m, 5Ar–H) ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ
187.42, 177.79, 154.17, 141.29, 136.64, 134.83, 134.23, 131.43,
125.29, 125.03, 124.11, 122.63, 120.57 and 112.73 ppm. C19H13N5O5S
requires: C, 53.90; H, 3.09; N, 16.54% found: C, 54.12; H, 3.27; N,
A solution of aminochalcones 3a-k (2.0 mmol) in glacial acetic acid
and ethanol mixture (2:1, 6.0 mL) were quickly cooled in an ice-salt bath
at 0–5 ◦C. The mixture was added in portions to a cold solution of
nitrosyl sulfuric acid [prepared from sodium nitrite (2.2 mmol, 151.8
9

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
16.76%
2Ar–H), 7.93 (1H, d, J = 15.5 Hz, –CH = ), 7.83 (2H, d, J = 7.6 Hz,
2Ar–H), 7.75 (2H, d, J = 8.0 Hz, 2Ar–H), 7.71 (1H, d, J = 15.9 Hz, –CH
= ), 7.31 (2H, d, J = 7.6 Hz, 2Ar–H) and 2.52 (s, 3H, SCH 3) ppm. 13C
NMR (APT) (DMSO‑d6, 125 MHz): δ 187.47, 177.70, 145.03, 143.57,
142.19, 134.79, 131.20, 130.66, 129.47, 125.55, 120.68, 120.34,
116.82 and 14.17 ppm. C20H16N4O3S2 requires: C, 56.59; H, 3.80; N,
13.20% found: C, 56.84; H, 3.98; N, 13.49%
4.3.4. 5-((4-(3-(4-chlorophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4d)
Yellow crystals, 0.288 g (70%) yield; m.p.304 ◦C. UV: גmax (DMF)
439.65 nm and Ɛmax 17980 molꢀ 1dm3cmꢀ 1. IR (KBr): 3425 (N–H), 3255
–
–
–
–
(2 N–H), 3079 (=Sp2-H), 1712 (C O), 1658 (C C), 1604 (C C), 1504
–
–
(N N) and 1350 (C S) cmꢀ 1. 1H NMR (DMSO‑d6, 500 MHz): δ 12.80
–
–
–
–
(3H, s, 3NH), 8.26 (2H, d, J = 8.6 Hz, 2Ar–H), 8.01 (1H, d, J = 15.5 Hz,
–CH = ), 7.94 (2H, d, J = 8.4 Hz, 2Ar–H), 7.72 (3H, m, 2Ar–H and –CH
= ) and 7.53 (2H, d, J = 8.4 Hz, 2Ar–H) ppm. 13C NMR (APT) (DMSO‑d6,
125 MHz): δ 187.50, 154.25, 142.23, 135.05, 134.31, 133.76, 130.63,
130.45, 128.96, 122.69, 120.23, 117.37 and 112.71 ppm.
4.3.9. 5-((4-(3-(2-chlorophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4i)
Orange crystals, 0.33 g (80%) yield; m.p.290 ◦C. UV: גmax (DMF)
437.17 nm and Ɛmax 33740 molꢀ 1dm3cmꢀ 1. IR (KBr): 3425 (N–H), 3248
2
–
–
–
(N–H), 3093 (N–H), 3000 (=Sp -H), 1712 (C O), 1658 (C O), 1604
–
ꢀ 1
1H NMR (DMSO‑d6, 500
–
–
–
–
C
19H13ClN4O3S requires: C, 55.28; H, 3.17; N, 13.57% found: C, 55.49;
(C C), 1496 (N N) and 1350 (C S) cm .
– –
H, 3.42; N, 13.75%
MHz): δ 14.04 (1H, s, OH), 12.54 (2H, s, 2NH), 8.28 (2H, d, J = 8.2 Hz,
2Ar–H), 8.23 (1H, d, J = 6.4 Hz, Ar–H), 8.03 (2H, m, 2Ar–H), 7.77 (2H,
d, J = 8.2 Hz, 2Ar–H), 7.57 (1H, d, J = 6.9 Hz, Ar–H) and 7.48 (2H, m,
2Ar–H) ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ 187.50, 177.77,
145.38, 138.33, 134.40, 134.25, 132.30, 132.11, 130.70, 130.06,
128.64, 127.72, 124.62, 120.47 and 116.82 ppm. C19H13ClN4O3S re-
quires: C, 55.28; H, 3.17; N, 13.57% found: C, 55.49; H, 3.42; N, 13.34%
4.3.5. 5-((4-(3-(4-bromophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4e)
Yellow crystals, 0.356 g (78%) yield; m.p.320 ◦C. UV: גmax (DMF)
434.37 nm and Ɛmax 37060 molꢀ 1dm3cmꢀ 1. IR (KBr): 3456 (N–H), 3255
2
–
–
–
–
(N–H), 3109 (N–H), 3000 (=Sp -H), 1712 (C O), 1658 (C O), 1604
(C C), 1504 (N N) and 1350 (C S) cm
.
1H NMR (DMSO‑d6, 500
ꢀ 1
–
–
–
–
–
–
MHz): δ 12.88 (3H, s, 3NH), 8.27 (2H, d, J = 8.7 Hz, 2Ar–H), 8.02 (1H, d,
J = 15.5 Hz, –CH = ), 7.87 (2H, d, J = 8.4 Hz, 2Ar–H), 7.75 (2H, d, J =
8.7 Hz, 2Ar–H), 7.72 (1H, d, J = 15.7 Hz, –CH = ) and 7.66 (2H, d, J =
8.4 Hz, 2Ar–H) ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ 187.47,
177.72, 173.20, 142.43, 134.41, 134.05, 131.89, 130.85, 130.54,
123.99, 122.67, 120.34 and 116.99 ppm. C19H13BrN4O3S requires: C,
49.90; H, 2.87; N, 12.25% found: C, 50.15; H, 3.11; N, 12.49%
4.3.10. 5-((4-(3-(2-methylphenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4j)
Orange crystals, 0.313 g (80%) yield; m.p.282 ◦C. UV: גmax (DMF)
435.93 nm and Ɛmax 28880 molꢀ 1dm3cmꢀ 1. IR (KBr): 3448 (N–H), 3147
2
3
–
–
–
(2 N–H), 3055 (=Sp -H) 2916 (-Sp -H), 1659 (C O), 1651 (C O),
–
1589 (C C), 1504 (N N) and 1334 (C S) cmꢀ 1. 1H NMR (DMSO‑d6,
–
–
–
–
–
–
500 MHz): δ 14.17 (1H, s, OH), 12.54 (2H, s, 2NH), 8.26 (1H, d, J = 7.7
Hz, 2Ar–H), 7.99 (2H, d, J = 14.6 Hz, 2Ar–H), 7.85 (1H, d, J = 15.3 Hz,
–CH = ), 7.76 (2H, d, J = 7.7 Hz, 2Ar–H), 7.32 (3H, m, 2Ar–H and CH = )
and 2.44 (3H, s, CH3) ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ
187.63, 177.69, 140.89, 138.08, 134.60, 133.31, 130.83, 130.56,
130.44, 126.92, 126.40, 122.75, 120.37, 116.82 and 19.37 ppm.
4.3.6. 5-((4-(3-(3-methylphenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4f)
Yellow crystals, 0.297 g (76%) yield; m.p.296 ◦C. UV: גmax (DMF)
437.43 nm and Ɛmax 26600 molꢀ 1dm3cmꢀ 1. IR (KBr): 3390 (N–H), 3248
3
–
–
–
–
(N–H), 3109 (N–H), 2862 (-Sp -H), 1712 (C O), 1658 (C O), 1604
C20H16N4O3S requires: C, 61.21; H, 4.11; N, 14.28% found: C, 60.97; H,
(C C), 1504 (N N) and 1350 (C S) cm
.
1H NMR (DMSO‑d6, 500
4.34; N, 14.50%
ꢀ 1
–
–
–
–
–
–
MHz): δ 14.14 (1H, s, OH), 12.52 (2H, s, 2NH), 8.27 (2H, d, J = 8.0 Hz,
2Ar–H), 7.95 (1H, d, J = 15.5 Hz, –CH = ), 7.75 (5H, m, 4Ar–H and –CH
= ), 7.34 (1H, t, J = 7.2 Hz, Ar–H), 7.27 (1H, d, J = 6.8 Hz, Ar–H) and
2.36 (3H, s, CH3) ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ 187.58,
177.71, 145.05, 144.10, 138.23, 134.66, 131.44, 130.57, 129.21,
128.87, 126.46, 121.64, 120.39, 116.81 and 20.93 ppm. C20H16N4O3S
requires: C, 61.21; H, 4.11; N, 14.28% found: C, 61.46; H, 4.34; N,
14.07%
4.3.11. 5-((4-(3-(thiophen-2-yl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4k)
Yellow crystals, 0.307 g (80%) yield; m.p.275 ◦C. UV: גmax (DMF)
436.24 nm and Ɛ max 30640 molꢀ 1dm3cmꢀ 1. IR (KBr): 3417 (N–H), 3248
–
–
–
–
(N–H), 3101 (N–H), 1705 (C O), 1658 (C O), 1589 (C C), 1504
–
–
(N N) and 1346 (C S) cmꢀ 1. 1H NMR (DMSO‑d6, 500 MHz): δ 12.83
–
–
–
–
(3H, s, 3NH), 8.18 (2H, d, J = 8.6 Hz, 2Ar–H), 7.91 (1H, d, J = 15.3 Hz,
–CH = ), 7.79 (1H, d, J = 5.0 Hz, thienyl-H), 7.70 (3H, m, 2Ar–H and
thienyl-H), 7.60 (1H, d, J = 15.3 Hz, –CH = ) and 7.19 (1H, t, thienyl-H)
ppm. 13C NMR (APT) (DMSO‑d6, 125 MHz): δ 159.06, 156.52, 143.74,
135.47, 134.94, 132.65, 130.56, 130.44, 129.22, 129.07, 128.66,
128.61, 128.44, 128.41, 126.80, 122.36 and 115.18 ppm. C17H12N4O3S2
requires: C, 53.11; H, 3.15; N, 14.57% found: C, 53.28; H, 3.41; N,
14.39%
4.3.7. 5-((4-(3-(4-methoxyphenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4g)
Orange crystals, 0.302 g (74%) yield; m.p.319 ◦C. UV: גmax (DMF)
434.68 nm and Ɛmax 28680 molꢀ 1dm3cmꢀ 1. IR (KBr): 3441 (N–H), 3309
3
–
–
–
N–H), 3109 (N–H), 2924 (-Sp -H), 1712 (C O), 1658 (C O), 1597
–
(C C), 1504 (N N) and 1350 (C S) cm .1HNMR (DMSO‑d6, 500
ꢀ 1
–
–
–
–
–
–
MHz): δ 14.17 (1H, s, OH), 12.52 (2H, s, 2NH), 8.25 (2H, d, J = 8.4 Hz,
2Ar–H), 7.85 (3H, m, 2Ar–H and –CH = ), 7.74 (3H, m, 2Ar–H and –CH
4.4. Dyeing process
= ), 7.02 (2H, d, J = 8.4 Hz, 2Ar–H) and 3.82 (3H, s, OCH3) ppm. 13
C
NMR (APT) (DMSO‑d6, 125 MHz): δ 187.41, 177.68, 161.40, 134.91,
130.88, 130.40, 127.37, 120.28, 119.32, 116.78, 114.43 and 55.41
ppm. C20H16N4O4S requires: C, 58.81; H, 3.95; N, 13.72% found: C,
59.07; H, 4.18; N, 14.01%
Disperse Cat dyes 4a-4c and 4e-4k were applied to polyester fiber
(PET), using high temperature dyeing method (HT) at 130 ◦C with a
material to liquor ratio of 1:20. 2% Dye was used for dying (calculated
on weight of the fiber). The dye was dissolved in 20 mL DMF, while pH
of the dye bath was adjusted to 4.5 using aqueous acetic acid and the
polyester fibres were added. Dyeing was performed by raising the dye
bath temperature to 130 ◦C under pressure in a dyeing machine at a rate
of 3 ◦C/min, holding at this temperature for 60 min and cooling to 50 ◦C.
After dyeing, the fiber was thoroughly washed and subjected to surface
reduction clearing [(1 g NaOH + 1 g sodium hydrosulphite)/L. The
samples were heated in this solution for 10 min at 60 ◦C and then
thoroughly washed and air-dried.
4.3.8. 5-((4-(3-(4-methylthiophenyl)acryloyl)phenyl)diazenyl)-2-
thioxodihydropyrimidine-4,6(1H,5H)-dione (4h)
Orange crystals, 0.305 g (72%) yield; m.p.315 ◦C. UV: גmax (DMF)
437.48 nm and Ɛmax 23180 molꢀ 1dm3cmꢀ 1. IR (KBr): 3425 (N–H), 3278
3
–
–
–
(N–H), 3101 (N–H), 2916 (-Sp -H), 1705 (C O), 1666 (C O), 1597
–
ꢀ 1
–
–
–
–
–
–
(C C), 1496 (N N) and 1342 (C S) cm
.
1H NMR (DMSO‑d6, 500
MHz): δ 13.98 (1H, s, OH), 12.54 (2H, s, 2NH), 8.26 (2H, d, J = 7.9 Hz,
10

A.Z. Omar et al.
Dyes and Pigments 185 (2021) 108887
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Alaa Z. Omar: Designed the research; performed the experimental
work; analyzed the data; wrote the manuscript; revised the manuscript;
all the authors discussed, edited and approved the final revision. Mona
N. Mahmoud: performed the experimental work; analyzed the data;
wrote the manuscript; all the authors discussed, edited and approved the
final revision. Samir K. El-Sadany: Designed the research; wrote the
manuscript; revised the manuscript; all the authors discussed, edited and
approved the final revision. Ezzat A. Hamed: Designed the research;
wrote the manuscript; revised the manuscript; all the authors discussed,
edited and approved the final revision. Mohamed A. El-atawy:
Designed the research; performed the experimental work; analyzed the
data; wrote the manuscript; revised the manuscript; all the authors
discussed, edited and approved the final revision
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The authors declare that they have no known competing financial
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