Synthesis, characterization and application of new azo dyes derived from uracil for polyester fibre dyeing

Article abstract of DOI:10.1016/j.molstruc.2010.06.005

Some novel uracil derived azo compounds were synthesized by diazotization of substituted aromatic amines, amidine- and guanidine-like amines such as 2-aminopyridine and 2-aminopyrimidine, ortho-hydroxy aniline and ortho-hydroxy naphthyl amines and coupling reaction with 6-amino-1,3-dimethyluracil. Structures of the dyes were fully characterized by spectroscopic techniques (UV, ¹H NMR, ¹³C NMR, CHN and IR). The dyes were applied to polyester, affording orange-yellow shades and the wash fastness of the dyeings was excellent.

Full text of DOI:10.1016/j.molstruc.2010.06.005

Journal of Molecular Structure 977 (2010) 266–273
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization and application of new azo dyes derived from uracil
for polyester fibre dyeing
a
b
b
Mohamad-reza Yazdanbakhsh a, , Masoumeh Abbasnia , Mehdi Sheykhan , Leila Ma’mani
*
a Chemistry Department, Faculty of Science, Guilan University, Rasht, Iran
b Chemistry Department, Tarbiat Modares University, P.O. Box 14155-4838, Tehran, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Some novel uracil derived azo compounds were synthesized by diazotization of substituted aromatic
amines, amidine- and guanidine-like amines such as 2-aminopyridine and 2-aminopyrimidine, ortho-
hydroxy aniline and ortho-hydroxy naphthyl amines and coupling reaction with 6-amino-1,3-dimethyl-
uracil. Structures of the dyes were fully characterized by spectroscopic techniques (UV, 1H NMR, 13C NMR,
CHN and IR). The dyes were applied to polyester, affording orange-yellow shades and the wash fastness of
the dyeings was excellent.
Received 18 April 2010
Received in revised form 3 June 2010
Accepted 4 June 2010
Available online 9 June 2010
Keywords:
Azo dyes
Ó 2010 Elsevier B.V. All rights reserved.
Disperse dyes
Dyeing polyester
Spectroscopic characterization
Uracil
1. Introduction
pyrido [2,3-d] pyrimidine-2,4-diones are prepared by the conden-
sation of 6-amino-1,3-dimethyluracil with
bonyl compounds [15].
a,b-unsaturated car-
Synthetic organic pigments are carbon based molecules manu-
factured by petroleum compounds, acids and other chemicals. In
recent years, the fabrication of pyrimidine dyes has been inten-
sively investigated, due to their unique industrial applications in
hypnotic drugs [1], in living cells, in detecting cancer [2] and hav-
ing pharmacological and biological activities [3–6]. Particularly
uracil derivatives have aroused much interest owing to their po-
tential applications in medicine and photobiology [7,8]. These
compounds, typically pyrimidine-like structures, have an elegance
role in heterocyclic chemistry [9]. Some derivatives of pyrimidine
are prepared by use of 6-aminouracils as the starting material;
for example, the reaction of 6-amino-1,3-dimethyluracil with an
aldehyde and urea in the presence of an acid catalyst results in
the formation of pyrimidopyrimides [10] or treating 6-amino-
1,3-dialkyluracils with DMF–thionyl chloride in CHCl3 at reflux, af-
fords the 3-aminoisothiazolo [3,4-d] pyrimidine-4,6-diones that
are useful as sedative, inflammation [11] and adenosine 3,5-cyclo-
phosphate phosphodiesterase inhibitors [11,12]. As a third exam-
ple, the reaction of these compounds with DMAD in refluxing
methanol gives a pyrido [2,3-d] pyrimidine [13] of which, some
of the oxo derivatives like 4-oxo-(NSC 112518) and 2,4-dioxopyri-
do [2,3-d] pyrimidine (NSC 112519) have antitumor activity
against Walker muscular carcinosarcoma in rats [14]. Moreover,
Azo dyes are the most widely applicable in industry [16] with a
world market share about 60–70% [17–19]. Some azo dyes were used
in high technological systems, biological studies, plastics and
polymers [20–28]. It can be expected that they make up the vast
majority of the dyes discharged by textile-processing industries [29].
Among all, the long discussion on the structure of diazophenols
has now been concluded. They feature the mesomeric structure
(Scheme 1) and not a bezooxadiazole structure, but have structures
that also called quininediazides, diazooxides and diazoquinones.
These compounds have been widely studied in the literature
[30–32] including their interesting photochemical properties
[33–35]. Photolysis of diazotized o-aminonaphtholes has recently
become important so-called photo-resist process in the production
of semi-conductor elements. Furthermore, the diazotization of
o-aminophenols and naphthols is important in the context of
o,o0-dihydroxyazometal complex dyes [22].
Because of the mentioned importance of the uracil functional
group, this paper is concerned with the synthesis and studying
the structure of 6-amino-1,3-dimethyluracil azo component, the
novel monoazo dyes based on the aryl and hetaryl systems
(Scheme 2 and Table 1), as a possible replacement for methine
and anthraquinone commercial dyes having similar color shades.
In addition to synthesizing these new dyes, their unique applica-
tion in dyeing polyester fibres and their spectroscopic properties
were studied.
* Corresponding author. Tel.: +98 131 772 3677; fax: +98 131 772 0733.
E-mail address: sheykhan@modares.ac.ir (M.-r. Yazdanbakhsh).
0022-2860/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2010.06.005

M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
267
Table 1
O
O
OH
Properties of the synthetic dyes.
Dye
M.p. (°C)
C%
H%
N%
diazotization
-HCl
Found
Calc.
Found
Calc.
Found
Calc.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
270–273
316–318
234–236
262–263
324–326
284–286
303–305
259–261
257–260
234–236
262–263
324–326
284–286
303–305
54.47
47.42
55.38
57.04
47.56
55.65
50.22
48.98
50.84
55.38
57.04
47.56
55.65
50.22
54.93
47.37
55.44
57.13
47.71
55.81
50.00
49.07
50.77
55.44
57.13
47.71
55.81
50.00
4.12
3.79
5.51
5.44
3.59
4.89
4.53
4.17
4.73
5.51
5.44
3.59
4.89
4.53
4.25
3.98
5.65
5.53
3.70
5.02
4.48
4.12
4.65
5.65
5.53
3.70
5.02
4.48
29.37
27.47
22.93
25.57
21.46
23.17
23.36
23.79
32.23
22.93
25.57
21.46
23.17
23.36
29.56
27.62
23.09
25.63
21.40
23.24
23.32
23.84
32.29
23.09
25.63
21.40
23.24
23.32
N
N
NH2
N2
Scheme 1. Quinoid structure of para-hydroxyaryldiazonium salts.
2. Experimental
2.1. General remarks
All chemicals were purchased from Merck chemical company.
The products were carefully isolated, purified and characterized
by their spectroscopic data (UV, IR, 1H NMR, 13C NMR, CHN) and
m.p. All yields refer to isolated products. 1H NMR spectra of the
dyes were recorded on a Bruker 500 spectrometer in either CDCl3
or DMSO-d6 as the solvent and TMS the internal standard. IR spec-
tra were determined on a Perkin Elmer IR-1600. The electronic
spectra and the elemental analysis were determined on a Hitachi
U-2000 and a Vario-EL III CHN analyzer, respectively. TLC was car-
2.2. Synthesis of the dyes
2.2.1. Method A
To an aqueous solution of the aromatic amine (2 mmol) and
concentrated (12 M, 10 mmol) HCl placed in an ice bath (cooled
to 0 °C) a cooled solution of sodium nitrite (2 mmol, 1.4 mL) was
drop-wise added and the mixture vigorously stirred for 10 min.
ried out on plates coated with silica gel 60 F254
.
HCl, NaNO2
Ar-NH2
Ar-N2
Cl
0 oC
NH2
NH2
H3C
O
N
O
Ar
H3C
O
N
N
N
H2O
0 oC
Ar-N2
+
CN
1
Cl
N
N
O
CH3
CH3
COCH3
CH3
OCH2CH3
NO2
CF3
Ar =
3
5
2
6
4
Cl
CONHCH2CO2H
N
H2N
Ph
N
N
N
N
N
10
11
9
8
7
Cl
SO3H
CO2H
HO
HO
OH
12
13
14
Scheme 2. Some azo compounds synthesized from 6-amino-1,3-dimethyluracil.

268
M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
2.1 mmol of 6-amino-1,3-dimethyluracil which dissolved in an
aqueous NaOH (4 mmol, 1.6 mL) was added to this mixture and
stirred for 30 min. After the HCl neutralizing and filtration, the
product was crystallized from DMF.
(125 MHz, DMSO-d6): d 26.2 (CH3), 28.8 (CH3), 30.0 (CH3), 114.0
(C), 122.8 (CH), 129.1 (CH), 137.5 (C), 152.1 (C), 153.1 (C@O),
157.9 (C@O), 177.1 (C), 196.3 (C@O).
6-Amino-1,3-dimethyl-5-(4-carboxyglycinophenyl
diaze-
nyl)uracil, (7): Light yellow solid; 1H NMR (500 MHz, DMSO-d6):
d 11.86 (br, 1H), 8.80 (br, 1H), 8.13 (br, 1H), 7.92 (d, 2H,
J = 8.4 Hz), 7.69 (d, 2H, J = 8.4 Hz), 3.76 (s, 3H), 3.40 (s, 3H), 2.91
(s, 1H), 2.76 (s, 1H). 13C NMR (125 MHz, DMSO-d6): d 26.3 (CH3),
28.9 (CH3), 38.8 (CH2), 114.1 (C), 122.6 (C), 123.3 (CH), 128.2
(CH), 151.9 (C), 153.6 (C@O), 159.3 (C@O), 170.9 (C@O), 176.6
(C@O), 177.5 (C).
2.2.2. Method B
A mixture of sodium nitrite (2 mmol) and concentrated H2SO4
(2 mL) at 0 °C was heated to 60 °C and again cooled to 0 °C. To this
solution a (5:1 v/v) mixture of acetic and propanoic acids (3 mL)
and aromatic amine (2 mmol) dissolved in (5:1 v/v) mixture of ace-
tic and propanoic acids (2 mL) was added. After 2 h at 0 °C added
the coupling agent (2 mmol) and the solution stirred for 6 h. The
precipitated product was collected and purified by recrystallization
from DMF.
6-Amino-1,3-dimethyl-5-(4-chlorophenyldiazenyl)uracil, (8):
Orange solid; 1H NMR (500 MHz, CDCl3): d 12.24 (br, 1H), 9.43
(br, 1H), 7.58–8.34 (m, 4H, ArH), 3.66 (s, 3H), 3.50 (s, 3H). 13C
NMR (125 MHz, CDCl3): d 29.4 (CH3), 30.2 (CH3), 117.6 (C), 123.8
(CH), 127.6 (CH), 128.8 (C), 149.9 (C), 156.7 (C@O), 162.6 (C@O),
179.4 (C).
6-Amino-1,3-dimethyl-5-(2-pyridodiazenyl)uracil, (9): Red-
dish crystals; 1H NMR (500 MHz, DMSO-d6): d 12.92 (br, 1H),
9.02 (br, 1H), 8.59 (d, 1H, J = 5.4 Hz), 7.97 (d, 1H, J = 6.9 Hz), 7.10
(t, 1H, J = 6.9 Hz), 6.78 (t, 1H, J = 5.4 Hz), 3.23 (s, 3H), 3.21 (s, 3H).
13C NMR (125 MHz, DMSO-d6): d 28.2 (CH3), 29.2 (CH3), 117.5
(C), 119.5 (CH), 120.9 (CH), 136.1 (CH), 147.4 (CH), 153.5 (C@O),
158.4 (C@O), 171.6 (C), 177.8 (C).
2.2.3. Method C
NaNO2 (70 mg, 1 mmol) was added to concentrated H2SO4
(1.0 mL) with external cooling. The suspension was heated to
60 °C and again cooled to 0–5 °C. To this cooled solution 0.2 mL of
acetic acid was added and it was stirred for 10 min. The amidine-like
and guanidine-like amine (1 mmol) dispersed in acetic acid (0.1 mL)
was carefully added portion-wise and the mixture was stirred con-
tinuously for 2 h with external cooling (0 °C). To a cooled basic solu-
tion of 6-amino-1,3-dimethyluracil (1 mmol) in sodium hydroxide
solution (2 mmol, 0.8 mL) the prepared diazonium solution was
added drop-wise and the mixture was stirred for 20 min at reaction
pH 7 (neutralized with sodium acetate). The precipitated product
was filtered and purified by recrystallization from DMF.
6-Amino-1,3-dimethyl-5-(2-pyrimidodiazenyl)uracil,
(10):
Purple crystals; 1H NMR (500 MHz, DMSO-d6): d 12.93 (br, 1H),
9.02 (br, 1H), 8.34 (d, 2H, J = 5.2 Hz), 6.43 (t, 1H, J = 5.2 Hz), 3.23
(s, 3H), 3.21 (s, 3H). 13C NMR (125 MHz, DMSO-d6): d 28.2 (CH3),
29.2 (CH3), 121.0 (C), 121.3 (CH), 152.7 (C@O), 156.2 (CH), 157.9
(C@O), 177.4 (C), 180.1 (C).
Physical and spectroscopic data follow
6-Amino-1,3-dimethyl-5-(4-cyanophenyldiazenyl)uracil, (1):
Yellowish solid; 1H NMR (500 MHz, DMSO-d6): d 11.83 (br, 1H),
8.94 (br, 1H), 7.90 (d, 2H, J = 8.5 Hz), 7.80 (d, 2H, J = 8.5 Hz), 3.38
(s, 3H), 3.25 (s, 3H). 13C NMR (125 MHz, DMSO-d6): d 28.2 (CH3),
29.2 (CH3), 102.6 (C), 114.1 (C), 117.5 (CN), 122.2 (CH), 131.3
(CH), 151.2 (C), 157.4 (C@O), 161.7 (C@O), 178.2 (C).
6-Amino-1,3-dimethyl-5-(4-amino-6-phenyltriazinediaze-
nyl)uracil, (11): Violet crystals; 1H NMR (500 MHz, DMSO-d6): d
12.91 (br, 1H), 9.03 (br, 1H), 8.16 (d, 2H, J = 7.5 Hz), 7.55 (t, 1H,
J = 7.5 Hz), 7.48 (t, 1H, J = 7.5 Hz), 3.96 (br, 2H), 3.23 (s, 3H), 3.21
(s, 3H). 13C NMR (125 MHz, DMSO-d6): d 24.7 (CH3), 29.0 (CH3),
121.2 (C), 128.4 (CH), 132.5 (CH), 132.7 (CH), 132.8 (C), 153.3
(C@O), 158.3 (C@O), 168.4 (C), 172.1 (C), 178.5 (C), 192.7 (C).
6-Amino-1,3-dimethyl-5-(4-chloro-2-hydroxyphenyldiaze-
nyl)uracil, (12): Yellowish crystals; 1H NMR (500 MHz, DMSO-d6):
d 12.11 (br, 1H), 11.04 (br, 1H), 8.80 (br, 1H), 7.75 (d, 1H, J = 2.6 Hz),
7.13 (dd, 1H, J = 8.7, 2.6 Hz), 6.88 (d, 1H, J = 8.7 Hz), 3.34 (s, 3H),
3.21 (s, 3H). 13C NMR (125 MHz, DMSO-d6): d 25.2 (CH3), 28.8
(CH3), 115.4 (CH), 124.2 (CH), 126.7 (CH), 129.3 (C), 133.9 (C),
148.1 (C), 153.4 (C@O), 160.7 (C@O), 178.0 (C).
6-Amino-1,3-dimethyl-5-(4-carboxylic-2-hydroxyphenyldiaze-
nyl)uracil, (13): Yellowish crystals; 1H NMR (500 MHz, DMSO-d6):
d 1H NMR (500 MHz, DMSO): d 11.43 (br, 1H), 8.51 (br, 1H), 8.06 (d,
1H, J = 2.5 Hz), 7.91 (br, 1H), 7.83 (dd, 1H, J = 8.8, 2.5 Hz), 6.99 (d,
1H, J = 8.8 Hz), 3.33 (s, 3H), 3.20 (s, 3H). 13C NMR (125 MHz,
DMSO-d6): d 24.2 (CH3), 27.8 (CH3), 113.6 (C), 114.4 (CH), 124.3
(CH), 124.8 (CH), 128.7 (C), 136.6 (C), 147.9 (C), 153.6 (C@O),
159.9 (C@O), 170.7 (C@O, carboxyl), 177.5 (C).
6-Amino-1,3-dimethyl-5-(4-nitrophenyldiazenyl)uracil,
(2):
Orange solid; 1H NMR (500 MHz, DMSO-d6): d 14.59 (br, 1H),
11.34 (br, 1H), 8.37 (dd, 2H, J = 7.2, 1.9 Hz), 7.72 (dd, 2H, J = 7.2,
1.9 Hz), 3.49 (s, 3H), 3.45 (s, 3H). 13C NMR (125 MHz, DMSO-d6):
d 28.4 (CH3), 29.3 (CH3), 114.3 (C), 122.6 (CH), 127.5 (CH), 151.3
(C), 154.3 (C), 158.6 (C@O), 163.7 (C@O), 180.4 (C).
6-Amino-1,3-dimethyl-5-(4-ethoxyphenyldiazenyl)uracil, (3):
Brownish crystal; 1H NMR (500 MHz, DMSO-d6): d 11.58 (br, 1H),
8.48 (br, 1H), 7.62 (d, 2H, J = 8.9 Hz), 7.01 (d, 2H, J = 8.9 Hz), 4.07
(q, 2H, J = 6.9 Hz), 3.62 (s, 3H), 3.24 (s, 3H), 1.39 (t, 3H,
J = 6.9 Hz). 13C NMR (125 MHz, DMSO-d6): d 14.9 (CH3), 28.3
(CH3), 29.1 (CH3), 63.5 (CH2), 112.4 (CH), 127.9 (CH), 144.6 (C),
153.0 (C@O), 152.5 (C), 157.0 (C@O), 176.3 (C).
6-Amino-1,3-dimethyl-5-(4-methylphenyldiazenyl)uracil, (4):
Dark yellowish crystal; 1H NMR (500 MHz, CDCl3): d 14.22 (br,
1H), 9.00 (br, 1H), 7.51–8.13 (m, 4H, ArH), 3.62 (s, 3H), 3.42 (s,
3H), 2.66 (s, 3H). 13C NMR (125 MHz, CDCl3): d 20.7 (CH3), 28.4
(CH3), 29.2 (CH3), 113.6 (C), 122.7 (CH), 127.6 (CH), 138.5 (C),
147.9 (C), 154.5 (C@O), 160.1 (C@O), 178.2 (C).
6-Amino-1,3-dimethyl-5-(2-hydroxy-4-sulfonicnaphthyldiaze-
nyl)uracil, (14): Pink crystals; 1H NMR (500 MHz, DMSO-d6): d
12.33 (br, 1H), 8.67 (br, 1H), 8.13 (d, 1H, J = 2.6 Hz), 7.91 (br, 1H),
7.83 (dd, 1H, J = 8.5, 2.6 Hz), 7.07 (d, 1H, J = 8.5 Hz), 3.37 (s, 3H),
3.28 (s, 3H). 13C NMR (125 MHz, DMSO-d6): d 26.2 (CH3), 28.9
(CH3), 106.9 (CH), 114.2 (C), 119.3 (CH), 120.4 (CH), 129.8 (C),
130.7 (CH), 131.7 (C), 133.6 (C), 137.7 (C), 153.0 (C@O), 158.2
(C@O), 165.1 (C), 179.1 (C).
6-Amino-1,3-dimethyl-5-(3-trifluorophenyldiazenyl)uracil,
(5): Yellow crystals; 1H NMR (500 MHz, DMSO-d6): d 11.74 (br,
1H), 8.72 (br, 1H), 7.91 (s, 1H), 7.88 (d, 1H, J = 8.1 Hz), 7.58 (t,
1H, J = 8.1 Hz), 7.51 (d, 1H, J = 8.1 Hz), 3.42 (s, 3H), 3.29 (s, 3H).
13C NMR (125 MHz, DMSO-d6): d 29.3 (CH3), 31.2 (CH3), 115.0
2
(C), 124.8 (q, C, JCF = 11.0 Hz), 125.1 (CH), 126.0 (CH), 126.5
1
(CH), 127.8 (q, CF3, JCF = 281.0 Hz), 153.0 (C), 156.6 (C@O), 162.2
(C@O), 178.0 (C).
3. Results and discussion
6-Amino-1,3-dimethyl-5-(4-acetylphenyldiazenyl)uracil, (6):
Yellow crystals; 1H NMR (500 MHz, DMSO-d6): d 11,90 (br, 1H),
8.86 (br, 1H), 8.53 (dd, 2H, J = 6.9, 1.7 Hz), 7.76 (dd, 2H, J = 6.9,
1.7 Hz), 3.38 (s, 3H), 3.26 (s, 3H), 2.60 (s, 3H). 13C NMR
Occasionally, aromatic amines having hydroxyl groups in ortho
or para-position cannot be diazotized by straight forward nitrosa-
tion, due to an oxidation of the initial hydroxy amine. This occurs

M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
269
with nitrosating reagents, forming the corresponding quinoid com-
pounds. We suppressed the side reaction by performing the diazo-
tization in the presence of copper or zinc salts.
Previously, Towne et al. [36] reported a method for diazotization
of amino-nitropyrazole and Gupta et al. [37] similarly introduced a
method for diazotization of 5-amino-4-cyanopyrazoles by use of a
mixture of acetic and propanoic acid (5:1 v/v). When we used a sim-
ilar condition as ‘‘method B”, we observed that the rates and yields of
products 1–8 and 12–14 were decreased, and the dye 9 was obtained
in low yield after 6 h. The reason for this effect is not clear at this
time, however, it seems to conclude that the acid effect in this reac-
tion depends mainly on three factors, namely, acidity, the softness of
counter ion and the strongly nature of reagents.
To find the best condition in which all of yields raised and
which is proper for the synthesis of heteroaromatic and hydroxy-
aryl amine-related dyes, we tested many acidic media. After these
experiments we achieved a system, containing dilution of acidic
media by 20% (v/v) acetic acid that improved all of yields. Using
this procedure even in case of the amines with high-basic proper-
ties (entries 9–11), the diazonium ions were quantitatively pre-
pared, trapped with 6-amino-1,3-dimethyluracil and then the
prepared dyes were fully characterized by spectroscopic methods
(Scheme 3). Also we prepared the dyes of o-hydroxy amines by this
method and in the presence of 1 equivalent of zinc chloride in high
yields (entries 12–14).
Because of the strong basic properties, heteroaromatic amines
especially amidine-like and guanidine-like ones are acid sensitive
compounds and suppressed in acidic aqueous solutions before
occurrence of any other process such as diazotization. In the best
of our knowledge, there are a few reports about the convenient
method to obtain azo dyes based on uracil, via coupling of a 6-ami-
no-1,3-dialkyluracil with some diazonium salts. The use of a meth-
od containing a ‘‘naked nitrosonium ion” such as nitrosylsulfuric
acid opens up new avenues for design of novel and amazing dyes.
Based on previous studies we decided to prepare the new uracil
based dyes that have high efficiency in industrial dyeing.
Firstly we synthesized the dyes by diazotization of the aromatic
and heteroaromatic amines via the common method as ‘‘method
A”. The coupling reaction was performed in aqueous solution with
6-amino-1,3-dimethyluracil as the coupling component (Table 2).
In eight cases (entries 1–8), the dyes were synthesized in moderate
yields. The desired product obtained in low yield in the cases con-
taining an electron donating groups (entries 3 and 4) on the ring. In
the case of entry 1, IR spectra with distinctive signal at 2240 cmꢀ1
and absence of any new carbonyl signal confirm that no hydrolysis
to amide happened and cyano group remained intact. Especially,
regarding the heteroaromatic amines (entries 9–11) and hydroxy-
aryl amines (entries 12–14), no noticeable product was observed.
Rather, in these cases, fast suppressing of the amine occurred.
We tried to obtain these dyes by reducing the concentration of
acid, but when this effected, no diazotization was observed.
3.1. Dye uptake determination
3.1.1. Standardized curve
To measure the dyes uptake, we determined kmax values and
extinction coefficients of dyes 1–7 according to the Beer Lambert
law. For this reason dyes 1–7 (1.0 ꢁ 10ꢀ1 mmol) were dissolved
in DMF (25 mL). Absorption of this solution (0.5 mL) was diluted
to 10 mL with deionized water and allowed to stand overnight
and then the absorption spectra were recorded (Fig. 1).
Table 2
Synthesis of the new uracil azo dyes.
Dye
number
Time
(min)
Yielda
(%)
Dye
number
Time
(min)
Yielda
(%)
3.1.2. Uptake measurement
After the dissolution of the dyes (0.1 g) in water–DMF (19:1,
25 mL), the solution was sonicated. Dilution to 50 mL using deion-
ized water–DMF (19:1) occurred and a portion of these dye solu-
tions (0.1, 0.3, 0.5, 0.7, 0.9, 1.1, 1.3 mL) was placed in seven
25 mL volumetric flasks and the volume of each was adjusted to
25 mL using deionized water–DMF (19:1). Absorbance values were
determined for each solution at kmax as a function of dye concen-
tration and linear standard curve for each dye was obtained.
To solutions prepared above in 50-mL flask, deionized water
(10 mL) was added. A mechanical stirrer and a thermometer was
placed in flask. At 25 °C, polyester fabric (1 g) was added and the
time was recorded. Bath aliquots (1.0 mL) were removed and
1
2
3
4
5
6
7
15
15
25
25
20
15
30
96
99
93
95
93
96
92
8
9
10
20
20
15
25
20
20
20
97
95
98
96
96
93
94
11
12b
13b
14b
a
Based on method C: reaction conditions: sodium nitrite (1 mmol), concentrated
H2SO4 (1.5 mL) was heated to 60 °C and again cooled to 0 °C, acetic acid (0.2 mL),
aromatic amine (1 mmol) dissolved in acetic acid (0.1 mL), coupling agent (1 mmol)
in sodium hydroxide solution (0.8 mL, 10% wt.); quenched after mentioned time.
Performing the diazotization in the presence of zinc chloride (one equivalent for
one equivalent of amine).
b
N
N
H2SO4, NaNO2
acetic acid (0.2 mL)
0-5 oC, 10 min
N
NH2
N
N2
HSO4
NH2
NH2
N
H3C
H3C
O
N
O
N
N
N
N
N
water
+
N
N2
HSO4
0-5 oC
O
N
O
N
CH3
CH3
Scheme 3. Synthesis of the guanidine-like dye.

270
M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
Fig. 1. Visible absorption spectra for dyes 1–7.
diluted to 25 mL at the following times and temperatures: 5 min/
25 °C, 8 min/35 °C, 15 min/40 °C, 30 min/60 °C, 50 min/90 °C,
70 min/95 °C, 100 min/95 °C, 120 min/95 °C, and 150 min/95 °C.
After the addition of 1 mL of DMF, the absorbance value of each
solution was recorded at kmax and the corresponding dye concen-
tration was determined from the standard curve for the corre-
sponding dye. The fabric quantities sufficient for fastness studies
were obtained by repeating the dyeing process using 10 g of fabric
samples (Fig. 2).
After treatments, the dyed fabric samples were washed with
cold water and treated for 30 min at 50–60 °C with a solution con-
taining fixing agent Y (5% omf) and aq. Acetic acid (2 mL), at a 30:1
liquor ratio. The dyed fabrics were washed, air-dried and ironed.
of light was 1500 W. Light fastness values for dyes 1–7 were based
on shade depth differences between unexposed and irradiated fab-
rics. As the result of hue and fastness properties of the dyes, poly-
ester fabrics were dyed at 4% omf. The dyed fabrics were treated
with 5% (w/w) cationic fixing agent (fixing agent Y). It was found
that dyes 1–7 gave deep shades on polyester 4% omf (Table 3).
3.2.2. Wash fastness
For wash fastness assessment, dyed and after-treated fabric
samples (50 ꢁ 30 mm) were attached to the same size undyed
spun polyester fabric samples and immersed in a bath of 0.5%
detergent at 35 °C and at a liquor ratio of 50:1.
After 30 min, the samples were removed, washed twice with
deionized water, washed with tap water (four times), and air-dried
below 50 °C. Changes in shade and staining of adjacent fabrics were
evaluated with the aid of gray-scales for color change and transfer.
3.2. Fastness analysis
3.2.1. Light fastness
Light fastness assessment of dyed fabrics were done under irra-
diation in a commercial xenon arc weatherometer until the change
in shade of blue-standard fabrics reached the 4–5 levels using the
gray scale. The black panel temperature was 50 °C and the power
3.3. IR and NMR analysis of structures
Physical and spectral data of the dyes prepared are given in the
experimental section. The dyes may exist in two tautomeric forms,
Fig. 2. Uptake of the dyes 1–7 on polyester fibre at 4% (omf).

M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
271
3550 cmꢀ1, due to ANH2 band of the uracil ring [38,39]. The aro-
matic and aliphatic CAH stretching signals were recorded at
Table 3
Shades and fastness properties for dyes 1–7 on polyester.
3000–3110 cmꢀ1 and 2840–2980 cmꢀ1
,
respectively. Strong
Dyes
Color
Wash fastness
Light fastness
absorption bands appear at 1610 to 1700 cmꢀ1 in the carbonyl re-
gion (Table 4). It can be suggested that these dyes exist as the azo-
enamine form (I) in solid state.
Change in
shade
Staining on
polyester
1
2
3
4
5
6
Yellowish black
Orange
4
4
3
4–5
4
4–5
3–4
3
4–5
5
3–4
4
4–5
5
4–5
4
4
4
3
3–4
3–4
4
3–4
2–3
2–3
The 1H NMR spectra measured in DMSO-d6 and CDCl3 at room
temperature showed broad singlet peaks at 11.58–14.59 ppm for
one proton and at 8.48–11.34 ppm, that correspond to the tauto-
meric hydrazone NH and tautomeric imine NH respectively. It
was reported that the hydrazone NH proton resonance appears
approximately between 13.0 and 16.0 ppm, in ortho and para-
hydroxyazo dyes [40,41]. These results show that all the dyes
may exist predominantly as the hydrazone–imine form (II) in solu-
tion. Aromatic protons appeared at 6.88–8.59 ppm in doublet, trip-
let, doublet of doublet and multiplet forms owing to different HAH
couplings. Other well-resolved and notable signals were singlets at
3.20–3.50 and 3.23–3.76 ppm for two different NACH3 groups on
uracil section. For each compound the lower-field signal corre-
sponds to the methyl group which lies between two carbonyl
groups (3-position of the uracil) and the upper-field one corre-
sponds to the other methyl.
Dark yellow
Bright orange
Mustard yellow
Mustard yellow
Brick orange
Yellow
7
8a
9b
Yellow
3–4
4–5
a
C. I. disperse yellow 31.
C. I. disperse yellow 51.
b
NH2
NH
H3C
N
O
H3C
N
N
N
N
N
H
O
N
O
O
N
CH3
II
CH3
I
3.4. UV–Vis absorption spectra
Solvent effect study of the dyes (Table 5 and Fig. 3) indicated
that the increase in dipole moment of the solvent, increased kmax
of the dyes (bathochromic effect). Media of higher dipole moment
stabilize the excited state more than the ground state and reduce
the band gap between two levels. In the case of acetic acid, the pro-
Scheme 4. The tautomerism in the dyes.
as shown in Scheme 4. The infrared spectra of the dyes 1–14 in
KBr) showed two strong bands within the range 3250 to
Table 4
Characteristic IR absorption bands of uracil synthesized dyes.
Dye
m
NH2 (stretching) (cmꢀ1
)
m
C@O (stretching) (cmꢀ1
)
m
N@N (stretching) (cmꢀ1
)
Functional group (stretching) (cmꢀ1
)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
3400, 3500
3400, 3450
3265, 3275
3245, 3260
3285, 3290
3260, 3300
3300, 3550
3300, 3550
3350, 3400
3350, 3400
3050–3400 (br)
Under overlap
Under overlap
3350, 3400
1640, 1700
1635, 1680
1620, 1695
1610, 1700
1615, 1700
1625, 1650
1650, 1690
1650, 1690
1650, 1700
1650, 1700
1645, 1710
1650, 1690
1660, 1700
1665, 1710
1520
1510
1520
1520
1530
1520
1525
1525
1510
1515
1520
1510
1515
1510
CN, 2240
NO2, 1340, 1520
CAO, 1150
CAH, 1360, 1450
CAF, 1330
C@O, 1700
C@O, 1600
CACl, 1170
C@C, 1580, 1600
C@C, 1570, 1580
C@N, 1575, 1610
OAH, 3100–3500 (br)
OAH, 2400–3550 (br)
OAS@O, 1180, 1380
Table 5
UV–Vis absorption of dyes in various solvents, acidic and basic media.
Dye
kmax in
emax (L mol cmꢀ1
)
DMF (nm)
DMSO (nm)
Methanol (nm)
AcOH (nm)
MeOH/KOH (nm)
MeOH/HCl (nm)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
393
399
389
387
374
389
363
356
398
402
336
413
408
381
414
420
409
407
395
410
382
378
418
423
351
436
429
400
388
392
384
381
368
380
357
350
393
395
331
408
403
373
399
405
395
392
381
394
370
364
403
408
343
418
412
389
392
388
379
389
366
380
352
347
388
394
330
406
398
372
395
402
393
390
379
392
366
357
402
406
341
415
408
384
1.4 ꢁ 104
3.1 ꢁ 104
2.3 ꢁ 104
2.1 ꢁ 104
2.7 ꢁ 104
2.7 ꢁ 104
2.7 ꢁ 104
2.2 ꢁ 104
1.9 ꢁ 104
1.9 ꢁ 104
2.3 ꢁ 104
2.6 ꢁ 104
2.7 ꢁ 104
2.9 ꢁ 104

272
M.-r. Yazdanbakhsh et al. / Journal of Molecular Structure 977 (2010) 266–273
Fig. 3. Absorption spectra of dye 2 in various solvents.
tonation process caused the increase of the maximum absorption
wavelength. The four solvents used in this test were DMSO, DMF,
methanol and acetic acid with 46, 36, 32 and 6 Debye dipole mo-
ments, respectively.
Meanwhile, the effects of acidic and basic media on electronic
spectrum of the dye 2 were recorded. Examination indicated that
the acidic medium increases the mesomeric electron withdrawing
effect of the nitro group by relative stabilization of its anionic form,
and leads to increase of the kmax. Conversely, basic medium de-
creases the kmax value.
functionals. With regard to satisfactory wash fastness properties
obtained from the dyeings, it is expected that if these new uracil
dyes are less genotoxic than the corresponding commercial ones,
they would be potential substitutes for those azo dyes. Study on
genotoxicity of the new dyes is under way.
Appendix A. Supplementary material
Original 1H NMR characterization data of the dyes, dyes IR spec-
tra structural analysis, different schemes/figures in text and eyeful
dyes in panorama. Supplementary data associated with this article
can be found, in the online version, at doi:10.1016/j.molstruc.2010.
06.005.
The observed kmax is dependent on the nature of substituent.
Mesomeric electron withdrawing groups (e.g. nitro and cyano) re-
duced the band gap by destabilization of the ground state. In con-
trast, the absorption band acquired a blue shift in presence of
trifluoro as an inductive electron withdrawing group. This can be
mainly attributed to the fact that it stabilized
p
and pꢂ orbitals,
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