Fluorescent azo disperse dyes from 3-(1,3-benzothiazol-2-yl)naphthalen-2-ol and comparison with 2-naphthol analogs

Article abstract of DOI:10.1016/j.dyepig.2012.07.019

Five novel fluorescent azo disperse dyes were synthesized using different diazotized aromatic amines followed by coupling with 3-(1,3-benzothiazol-2-yl) naphthalen-2-ol. These dyes were characterized by FT-IR, ¹H NMR and mass spectroscopy. These azo disperse dyes were applied on polyester and their fastness properties were evaluated. A parallel series of dyes using 2-naphthol in place of benzothiazolyl were made to investigate the effect of benzothiazolyl moiety on the fastness properties. This investigation showed that the dyes containing benzothiazolyl residue have better fastness properties than that of the azo disperse dyes based on 2-naphthol. Effect of pH on photo physical properties was also studied.

Full text of DOI:10.1016/j.dyepig.2012.07.019

Dyes and Pigments 96 (2013) 92e103
Contents lists available at SciVerse ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Fluorescent azo disperse dyes from 3-(1,3-benzothiazol-2-yl)naphthalen-2-ol
and comparison with 2-naphthol analogs
,
Manjaree A. Satam a, Rajesh K. Raut b, N. Sekar a
*
a Tinctorial Chemistry Group, Department of Dyestuff Technology, Institute of Chemical Technology, Matunga, Mumbai 400 019, India
b Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW 2109, Australia
a r t i c l e i n f o
a b s t r a c t
Article history:
Five novel fluorescent azo disperse dyes were synthesized using different diazotized aromatic amines
followed by coupling with 3-(1,3-benzothiazol-2-yl)naphthalen-2-ol. These dyes were characterized by
FT-IR, 1H NMR and mass spectroscopy. These azo disperse dyes were applied on polyester and their
fastness properties were evaluated. A parallel series of dyes using 2-naphthol in place of benzothiazolyl
were made to investigate the effect of benzothiazolyl moiety on the fastness properties. This investi-
gation showed that the dyes containing benzothiazolyl residue have better fastness properties than that
of the azo disperse dyes based on 2-naphthol. Effect of pH on photo physical properties was also studied.
Ó 2012 Elsevier Ltd. All rights reserved.
Received 27 May 2012
Received in revised form
21 July 2012
Accepted 26 July 2012
Available online 3 August 2012
Keywords:
Benzothiazole
Fluorescent azo disperse dye
Photo physical property
pH study
Enhanced light fastness
2-Naphthol analog
1. Introduction
Among them thiazolyl and benzothiazolyl azo compounds are the
most popular ones in the production of red azo dyes having better
Azo dyes represent the single largest chemical class of industrial
colorants. They are the most versatile and robust group of synthetic
dyes, which cover the full range of shades of colors. The ease of
preparation of azo dyes by diazotization and azo coupling reactions
and economy of the reaction have led to the synthesis of many dyes
in the past. Replacement of anthraquinone dyes with equivalent
azo dyes has great importance [1,2]. Azo disperse dyes containing
aromatic heterocyclic moiety have been investigated due to their
superior properties in general, and the use of heterocyclic diazo or
coupling components in particular has made possible the produc-
tion of colorants with brilliant color and chromophoric strength,
high level-dying property and excellent fastness properties [3e7].
Azo dyes based on heterocyclic compounds have been reviewed
comprehensively [4,8e10]. Heterocyclic azo disperse dyes are used
to dye hydrophobic fibers especially polyester and polyamide
fabrics due to their excellent properties; they have also been
utilized in non-textile applications such as lasers and non-linear
optical systems [11], photodynamic therapy, reprography [12],
dye sensitized solar cells [13], and metallochromic indicators [14].
fastness properties [15e18]. Benzothiazolyl azo disperse dyes are
used for dyeing polyester fabrics due to their better fastness and
high level-dyeing properties [19e24]. Azo disperse dyes containing
thiazole unit have been investigated due to their excellent prop-
erties [25].
The photo stability and hence light fastness of mono azo
disperse dyes can be enhanced by the presence of hydroxyl, amino,
or acetamido groups at ortho position relative to the azo bridge [26]
which is attributed to the hydrogen bonding between hydroxyl and
azo groups. However mono azo disperse dyes derived from 2-
naphthol as coupling component are reported to have poor light
fastness [27]. Many a times UV absorber-finish is given to prevent
photo degradation of dyed fabrics, or UV absorbing unit is delib-
erately introduced into the dye molecule [28e32]. The commonly
used UV absorbers or substituted benzophenones, benzotriazole
and their exceptional photo stability are attributed to the presence
of hydrogen bonding [32].
In this paper we have reported azo disperse dyes using 3-(1,3-
benzothiazol-2-yl) naphthalen-2-ol as a coupler. The benzothia-
zolyl group present adjacent to the hydroxyl group is known to
enter into an excited state intramolecular proton transfer (ESIPT) as
shown in Fig. 1 [33] conferring extra photo stability. It was
* Corresponding author. Tel.: þ91 22 3361 2707; fax: þ91 22 3361 1020.
E-mail addresses: n.sekar@ictmumbai.edu.in, nethi.sekar@gmail.com (N. Sekar).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.dyepig.2012.07.019

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
93
temperature. The dyed fabrics were rinsed and then reduction
cleared in an aqueous solution of 1 g Lꢁ1 sodium hydroxide and
1 g Lꢁ1 sodium hydrosulfite using 50:1 liquor to goods ratio at
80 ꢀC for 10 min. The treated fabrics were then rinsed under cold
water and allowed to dry in the open air.
H
H
O
O
N
N
ESIPT
S
S
K*
E*
2.2.2. Fastness to washing
A specimen of dyed polyester fabric was stitched between two
pieces, one of undyed polyester and other of cotton fabric having
equal length. This fabric was washed in solution (3 g Lꢁ1 Na2CO3,
1 g Lꢁ1 NaOH) with 1:50 fabric to solution ratio at 60 ꢀC for 30 min.
The staining on the undyed adjacent fabric or change in tone was
assessed according to the following international geometric gray
scale (1 for poor and 5 for excellent).
H
O
H
O
N
N
S
2.2.3. Fastness to light
S
Light fastness was evaluated by exposing a dyed fabric to high-
energy radiation (Q-SUN Xenon Test Chamber, Q-LAB, USA) in
a fade-o-meter for 24 h and compared with unexposed fabric.
AATCC Test method was used for evaluation (scale: 1 for poor and 8
for outstanding).
K
E
E = enol form in ground state; K = keto form in ground state;
E* = enol form in excited state; K* = keto form in excited state.
Fig. 1. Mechanism of ESIPT.
2.2.4. Fastness to sublimation
Sublimation fastness was measured with a sublimation fastness
tester (R. B. Electronics and Engineering Pvt. Ltd.). The sample was
prepared by stitching a piece of dyed polyester fabric between two
pieces, one of undyed polyester and other of cotton fabric having
equal length and then treated at 180 ꢀC for 30 s. Any staining on the
undyed adjacent fabric or change in tone was assessed according to
the following international geometric gray scale (1 for poor and 5
for excellent).
envisaged that presence of such an ESIPT in mono azo dyes will lead
to dyes with superior light fastness properties. It is also known that
azo disperse dyes having an inbuilt ESIPT unit fluoresce in highly
polar solvents [34], although the fluorescence intensity is sup-
pressed due to presence of azo bridge [35e38]. It is also to be noted
that 3-(1,3-benzothiazol-2-yl) naphthalen-2-ol has been used in
the preparation of mono azo pigments [39,40] and bisazo dyes
[41,42].
2.2.5. Color assessment
The color coordinates of azo disperse dyes were determined on
CE-7000A Gretag-Macbeth computer color matching system. The
color values were expressed by using CIE 1976 Color Space method.
The coordinates used to determine color values are “L*” for light-
ness, “a*” for redness (positive value) and greenness (negative
value), “b*” for yellowness (positive value) and blueness (negative
value), “c*” for chroma and “ho” for hue angle in the range of
0ꢀe360ꢀ. “K/S” value is directly associated with the dye
concentration on polyester fabrics.
2. Materials and methods
2.1. Materials
Aniline,
2-aminothiophenol,
3-hydroxynaphthalene-2-
carboxylic acid, 4-chloroaniline, 4-nitroaniline, 4-methoxyaniline,
4-nitroaminophenol, sodium carbonate, sodium hydroxide, meta-
mol (dispersing agent) and conc. HCl were purchased from S.D. fine
chemicals Ltd, Mumbai, India. Solid reagents were characterized by
melting point and used without purification. Liquid reagents
distilled at their boiling points and used thereafter. Solvents were
used after necessary purification and drying according to standard
processes.
2.2.6. Spectrophotometer measurements
UVevisible spectral studies were carried on Spectrophotometer
(Modele8500, TECHCOMP, Hong Kong) with 1 cm quartz cells. The
concentration used was 100 ppm.
2.2.7. Fluorescence emission measurements
2.2. Methods
Fluorescence emission measurements were performed on
JASCO-FP 1520 with Borwin software.
2.2.1. General procedure of dyeing [43,44]
Disperse dyeing of polyester fabric was carried out using high
temperature high pressure method in Rossari Labtech Flexi Dyer
dyeing machine at a material to liquor ratio of 1:20. Fabric was
dyed using 2% dye (calculated on weight of the fabric). All
synthesized azo disperse dyes are having poor solubility in water.
Initially dye was dissolved in 5 mL N,N-dimethylformamide and
diluted with 15 mL buffered solution of pH 5 made by using
sodium acetate and acetic acid in water. Solution was ultra-
sonicated for 15 min to obtain fine dispersion. Metamol was used
as a dispersant. Polyester fabric was dyed using above solution.
Dyeing was commenced at room temperatꢁu1re. The dye bath
temperature was raised at a rate of 3 ꢀC min to 130 ꢀC, main-
tained at this temperature for 60 min, and rapidly cooled to room
2.3. Experimental
All reactions were monitored on precoated silica gel aluminum
based plates kisel gel 60 F254 Merck, India. Purification of all
compounds was achieved by recrystallization. Purity of compounds
was ascertained by thin layer chromatography. Melting points were
recorded by using open capillary on instrument from Sunder
Industrial Product and are uncorrected. Infrared analysis was
carried on an FTIR-8400S spectrophotometer, SHIMADZU. 1H NMR
spectra were recorded on 400 MHz on Varian mercury plus spec-
trometer. Chemical shifts are expressed in
internal standard and CDCl3 as a solvent.
d ppm using TMS as an

94
M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
2.4. Synthesis
(eC]N), 1557 (eN]N), 1504 (aromatic ring), 748 (eCeS). Mass: m/
z: 427 (M þ 1).
2.4.1. General procedure for preparation of 3-(1,3-benzothiazol-2-
yl)naphthalen-2-ol
2.4.3.4. 3-(1,3-Benzothiazol-2-yl)-1-[(E)-(4-methoxyphenyl)dia-
Phosphorus trichloride (2.6 mL, 4.13 g, d ¼ 1.57 g mLꢁ1, 0.03 mol)
was added drop wise to a mixture of the 3-hydroxynaphthalene-2-
carboxylic acid (6.2 g 0.033 mol) and 2-aminothiophenol (3.85 mL,
4.5 g, d ¼ 1.17 g mLꢁ1, 0.036 mol) in toluene (50 mL). Slight exo-
therm was observed. The temperature was maintained below
45e50 ꢀC during the addition of phosphorus trichloride. The
mixture was refluxed vigorously for 4 h and then cooled solution
was made alkaline using 20% sodium carbonate solution. Solid was
filtered. Crude solid was slurred in methanol and filtered to remove
methanol-soluble impurities followed by washing with (25 mL)
80% aqueous acetone. Homogenous spot was obtained on TLC. This
was used as a coupler. Yield: 65%; m.p.: 182 ꢀC (literature
183 ꢀC) [45].
zenyl]naphthalen-2-ol 6d. Color: red. Yield: 91%; m.p.: 204e206 ꢀC.
1H NMR (CDCl3,
d ppm): 17.25 (s, 1H, Hydrogen bonding), 9.05 (s,
1H, AreH), 8.45 (d, 1H, AreH, J ¼ 8.2 Hz), 8.09 (d, 1H, AreH,
J ¼ 8.3 Hz), 7.98 (d, 1H, AreH, J ¼ 7.9 Hz), 7.8 (d, 2H, AreH,
J ¼ 7.9 Hz), 7.69 (d, 2H, AreH, J ¼ 8.9 Hz), 7.56 (m, 2H, AreH),
7.39 (t, 1H, AreH, J ¼ 7.7 Hz), 7.01 (d, 2H, AreH, J ¼ 8.9 Hz), 3.93
(s, 3H, eOCH3), 1.6 (s, 1H, eOH). FT-IR (KBr, cmꢁ1): 3463 (eOH),
1604 (eC]N), 1552 (eN]N), 1508 (aromatic ring), 1258
(eCeOeAr), 757 (eCeS). Mass: m/z: 412 (M þ 1).
2.4.3.5. 3-(1,3-Benzothiazol-2-yl)-1-[(E)-(2-hydroxy-5-nitrophenyl)
diazenyl]naphthalen-2-ol 6e. Color: blackish red. Yield: 78%; m.p.:
312e314 ꢀC. 1H NMR (CDCl3,
d ppm): 16.23 (s, 1H, Hydrogen
bonding), 9.11 (s, 1H, AreH), 8.42 (s, 1H, AreH), 8.28 (d, 1H, AreH,
J ¼ 8.0 Hz), 8.24 (d, 1H, AreH, J ¼ 9.0 Hz), 8.11 (d, 1H, AreH,
J ¼ 3.0 Hz), 8.00 (d, 1H, AreH, J ¼ 8.0 Hz), 7.8 (d, 1H, AreH,
J ¼ 8.3 Hz), 7.65 (t, 1H, AreH, J ¼ 7.1 Hz), 7.54 (m, 2H, AreH), 7.43
(t, 1H, AreH, J ¼ 7.0 Hz), 7.32 (t, 1H, AreH, J ¼ 8.3 Hz), 3.49 (s, 1H,
OH), 1.25 (s, 1H, OH). FT-IR (KBr, cmꢁ1): 3593, 3462 (eOH), 1586
(eC]N),1553 (eN]N),1498 (aromatic ring), 758 (eCeS). Mass: m/
z: 443 (M þ 1).
2.4.2. General method of diazotization
One of the substituted aromatic amines 4aee (0.015 mol) was
taken in water. Conc. HCl (0.045 mol, 1.64 g, d ¼ 1.1 g mLꢁ1, 4.98 mL
of 30% HCl) was added to dissolve completely. Then reaction
mixture was cooled to 0e5 ꢀC by using iceesalt mixture. Cold 20%
solution of NaNO2 (0.015 mol, 1.03 g) was added drop wise over the
period of 10 min. Reaction mixture was stirred for 30 min.
Completion of diazotization was checked using starch iodide paper.
0.01 g of urea was added to consume excess of nitrous acid [46].
3. Results and discussions
2.4.3. General method of coupling
The synthesis of target fluorescent azo disperse dyes 6aee were
3-(1,3-Benzothiazol-2-yl)naphthalen-2-ol (0.01 mol, 2.77 g) was
dissolved in (50 mL) 80% of methanol in water having 0.4 g NaOH
(0.01 mol). Clear yellow solution was obtained. Reaction mixture was
then cooled to 5 ꢀC. Above diazotized amine was added slowly with
constant stirring and maintaining temperature at 5 ꢀC and pH between
9 and 10. Dyes 6aee were collected and purified by using methanol.
accomplished by condensation of 3-hydroxynaphthalene-2-
carboxylic acid
1 with 2-aminothiophinol 2 to give 3-(1,3-
benzothiazol-2-yl)naphthalen-2-ol 3 as a coupler, followed by
coupling with diazotized aromatic amines 4aee (Fig. 2).
Synthesized azo disperse dyes 6aee are having red color with
high color strength. All these azo disperse dyes showed weak
fluorescence in polar as well as in non-polar solvents. This may be
due to the presence of azo group, which is known to quench the
fluorescence [35e38]. Absorption and emission spectra of disperse
dyes 6aee in DMF is summarized in Figs. 3 and 4 respectively.
2.4.3.1. 3-(1,3-Benzothiazol-2-yl)-1-[(E)-(4-chlorophenyl)diazenyl]
naphthalen-2-ol 6a. Color: red. Yield: 88%; m.p.: 248e250 ꢀC. 1H
NMR (CDCl3,
d ppm): 16.72 (s, 1H, Hydrogen bonding), 9.03 (s, 1H,
AreH), 8.36 (d, 1H, AreH, J ¼ 8 Hz), 8.10 (d, 1H, AreH, J ¼ 8 Hz), 7.95
(d 1H, AreH, J ¼ 8 Hz), 7.72 (d,1H, AreH, J ¼ 8 Hz), 7.58 (t, 2H, AreH,
J ¼ 3 Hz), 7.52 (t, 2H, AreH, J ¼ 9 Hz), 7.37 (d, 4H, AreH, J ¼ 8 Hz),
1.60 (s, 1H, OH). FT-IR (KBr, cmꢁ1): 3442 (eOH), 1607 (eC]N), 1555
(eN]N), 1498 (aromatic ring), 821 (eCeCl), 755 (eCeS). Mass: m/
z: 416.5 (M þ 1).
3.1. Effect of solvent polarity on photo physical properties of azo
disperse dyes 6aee
A parallel series of azo disperse dyes 60aee were made using 2-
naphthol in place of 3. To evaluate the effect of solvent polarities on
photo physical properties of azo disperse dyes, dyes 6aee synthe-
sized from 3 as well as disperse dyes 60aee synthesized from 2-
naphthol were analyzed in seven different solvents of differing
polarity, dielectric constant, refractive indices. Effects of solvent
polarity on absorption and emission of these dyes are summarized
in Tables 1e5 (Figs. 5e9). It was observed that change in solvent
polarity does not have significant influence on absorption maxima
as well as emission maxima (Figs. 5e8) except for the dye 6e, which
contains a nitro group on the acceptor side of the azo dye. The dye
6e absorbed at 506 nm in almost all solvents except in highly polar
aprotic solvent, DMSO in which it showed red shift of 144 nm
(Fig. 9).
2.4.3.2. 3-(1,3-Benzothiazol-2-yl)-1-[(E)-phenyldiazenyl]naph-
thalen-2-ol 6b. Color: red. Yield: 92%; m.p.: 272e274 ꢀC. 1H NMR
(CDCl3, d ppm): 16.88 (s, 1H, Hydrogen bonding), 9.11 (s, 1H, AreH),
8.85 (d, 1H, AreH, J ¼ 8 Hz), 8.14 (d, 1H, AreH, J ¼ 8 Hz), 8.02 (d, 1H,
AreH, J ¼ 8 Hz), 7.82 (d, 1H, AreH, J ¼ 7 Hz), 7.78 (d, 1H, AreH,
J ¼ 7 Hz), 7.62 (t, 1H, AreH, J ¼ 7.9 Hz), 7.53 (t, 3H, AreH,
J ¼ 7 Hz), 7.44 (d, 2H, AreH, J ¼ 7 Hz), 7.31 (d, 1H, AreH,
J ¼ 8 Hz), 1.25 (s, 1H, OH). FT-IR (KBr, cmꢁ1): 3439 (eOH), 1604
(eC]N),1557 (eN]N),1499 (aromatic ring), 758 (eCeS). Mass: m/
z: 382 (M þ 1).
2.4.3.3. 3-(1,3-Benzothiazol-2-yl)-1-[(E)-(4-nitrophenyl)diazenyl]
Fluorescence emission of azo disperse dyes 6aee were also
insensitive to solvent polarity (Tables 1e5). The variation in emis-
sion intensity does not have any specific relation to the solvent
polarity. Dyes 6a, 6c and 6d showed highest emission intensity in
non-polar solvent like chloroform (Figs. 5, 7 and 8), while
compound 6b showed high emission intensity in highly polar
aprotic solvent, DMSO (Fig. 6). Dye 6e showed least emission
intensity in DMSO (Fig. 9). Intensities of fluorescence of all azo
naphthalen-2-ol 6c. Color: brownish red. Yield: 83%; m.p.:
290e292 ꢀC. 1H NMR (CDCl3,
d ppm): 16.31 (s, 1H, Hydrogen
bonding), 9.08 (s, 1H, AreH), 8.42 (d, 1H, AreH, J ¼ 8 Hz), 8.36 (d,
2H, AreH, J ¼ 7.3 Hz), 8.12 (d, 1H, AreH, J ¼ 8.0 Hz), 8.00 (d, 1H,
AreH, J ¼ 8.0 Hz), 7.84 (t, 2H, AreH, J ¼ 8.0 Hz), 7.76 (d, 1H, AreH,
J ¼ 7.0 Hz), 7.64 (t, 1H, AreH, J ¼ 8.2 Hz), 7.54 (m, 2H, AreH), 7.42
(m, 1H, AreH), 1.57 (s, 1H, OH). FT-IR (KBr, cmꢁ1): 3621 (eOH), 1599

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
95
Step 1:
OH
S
OH
OH
H2N
Toluene, PCl3
Reflux
+
N
O
HS
[ 2 ]
[ 3 ]
[ 1 ]
Step 2:
Cl- N+
N
NH2
Diazotization, NaNO2/HCl
0-5 oC
a: R = 4-Cl
b: R = H
R
R
c: R = 4-NO
2
[ 4 (a-e) ]
d: R = 4-OCH
[ 5 (a-e) ]
3
e: R = 2-OH, 5-NO
2
Step 3:
R
Cl- N+
N
OH
Coupling, pH 8 - 9
0-5 oC
N
+
N
N
S
R
[ 5 (a-e) ]
OH
S
[ 3 ]
N
[ 6 (a-e) ]
Fig. 2. Experimental scheme for azo disperse dyes.
disperse dyes 6aee were very low which may be ascribed to the
presence of azo group [35e38]. Similar trend was observed in dyes
(60aee) based on 2-naphthol except for the fact that they do not
have any emission.
compare to dyes 60aee Figs. 5e10 (Tables 1e5) except for the dye 6e
and 60e; the dye 60e showed two absorptions.
3.2. Effect of pH on photo physical properties of azo disperse dyes
A comparison of dyes containing benzothiazolyl group (6aee)
with the parallel series of dyes (60aee) devoid of benzothiazolyl
dyes revealed the following. The dyes 6aee were red shifted
6aee
pH sensitive dyes have applications as indicators and visible
ratiometric sensors [47]. In order to understand the behavior of
Wavelength (nm)
Fig. 3. UV visible absorption spectra of synthesized azo disperse dyes 6aee in DMF.
Fig. 4. Fluorescence emission spectra of synthesized azo disperse dyes 6aee in DMF.

96
M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
Table 1
Effect of solvents on photo physical properties of dyes 6a and 60a.
Solvents
6a
60a
lmax (nm)
Ɛ Molar absorptivity
lemi (nm)
Emission
intensity
Dl (nm)
lmax (nm)
Ɛ Molar
lemi (nm)
Emission
intensity
(dm3 molꢁ1 cmꢁ1
)
absorptivity
(dm3 molꢁ1 cmꢁ1
)
CHCl3 (a)
EtOAc (b)
1,4-Dioxane (c)
Ethanol (d)
ACN (e)
513
506
509
509
509
512
515
22,187
21,481
23,351
23,683
21,979
22,686
21,107
589
589
589
589
589
581
587
2.344
1.333
1.544
1.676
0.946
1.744
1.239
76
83
80
80
80
69
72
482
470
474
473
474
476
476
13,654
11,053
12,467
11,392
12,834
12,099
12,947
e
e
e
e
e
e
e
e
e
e
e
e
e
e
DMF (f)
DMSO (g)
Table 2
Effect of solvents on photo physical properties of dyes 6b and 60b.
Solvents
6b
60b
lmax (nm)
Ɛ Molar absorptivity
lemi (nm)
Emission
intensity
Dl (nm)
lmax (nm)
Ɛ Molar absorptivity
lemi (nm)
Emission
intensity
(dm3 molꢁ1 cmꢁ1
)
(dm3 molꢁ1 cmꢁ1
)
CHCl3 (a)
EtOAc (b)
1,4-Dioxane (c)
Ethanol (d)
ACN (e)
510
506
506
506
506
509
512
14,897
12,877
17,449
11,277
11,391
14,020
12,115
571
586
585
585
585
589
567
3.213
0.913
1.306
1.010
0.614
0.959
3.738
61
80
79
79
79
80
55
482
473
474
477
474
474
480
2579
2232
2058
2356
2802
2430
2331
e
e
e
e
e
e
e
e
e
e
e
e
e
e
DMF (f)
DMSO (g)
dyes 6aee which carries an ESIPT unit, absorption and emission
studies as a function of pH were undertaken in the pH range 2e12.
Aqueous solutions containing DMF were prepared and pH
(2,4,6,8,10,12) values were adjusted using 5% hydrochloric acid
and 5% sodium hydroxide solutions.
Colorsof dyes 6a, 6b and 6din all pH solutions remained same, but
dyes 6c and 6e showed visible color change from acidic media to
highly alkaline media. Dye 6c showed orange color from pH 2 to pH 8
and turn into wine red beyond pH 10. Similarly, color of dye 6e was
orange in color and turned into dark reddish brown color in highly
alkaline media. The absorptionvalues are summarized inTable 6. Also
dyes 6c and 6e showed dual absorption maxima at highlyalkaline pH.
Longer absorption band was observed at around 635 nm.
Emission maxima of all the dyes 6aee remained same at all pH.
However the emission intensity changed with the change in pH,
although not uniformly. The dye 6c however showed a gradual
increase in the emission intensity with decrease in pH. Dyes 6c and
6e with a nitro group on the acceptor side of the azo dye showed
less emission intensities in highly alkaline media. The results are
summarized in Table 6, Figs. 11e15.
rather than from solution to avoid loss of dye [21]. Synthesized azo
disperse dyes were insoluble in water and were prepared for
application on polyester fiber by dispersing in water. These readily
dispersible dyes 6aee were dyed hydrophobic fibers (polyester
fabrics) at 2% shade by using high temperature pressure technique.
These dyes generally give red shade on polyester fabrics with
excellent uniformity. Dyed fabrics were evaluated in terms of their
fastness properties. Various fastness properties such as light, wash
and sublimation of the dyed polyester fabrics were studied and the
values are given in Table 7.
3.3.1. Fastness to washing
Wash fastness property depends upon the solubility of dye in
water, type of linkage present in dye molecule and fiber, size of dye
molecules and charge present on the dye. All synthesized azo
disperse dyes 6aee show excellent wash fastness properties
according to the international geometric gray scale. This result is
attributed may be due to the less solubility of the dyes in water.
Staining against polyester and cotton gives excellent ratings, as
both fabrics remain undyed.
3.3.2. Fastness to sublimation
3.3. Dyeing and fastness properties of the dyes 6aee on polyester fabric
Fastness to sublimation is the most important requirement of
dyed polyester fabrics, as migration of dye molecules and wet
fastness of azo disperse dyes on polyester fabrics are totally
Most of the azo disperse dyes are insoluble in water. These dyes
are used to apply on polyester fabric from aqueous dispersion
Table 3
Effect of solvents on photo physical properties of dyes 6c and 60c.
Solvents
6c
60c
lmax (nm)
Ɛ Molar absorptivity
lemi (nm)
Emission
intensity
Dl (nm)
lmax (nm)
Ɛ Molar
lemi (nm)
Emission
intensity
(dm3 molꢁ1 cmꢁ1
)
absorptivity
(dm3 molꢁ1 cmꢁ1
)
CHCl3 (a)
EtOAc (b)
1,4-Dioxane (c)
Ethanol (d)
ACN (e)
507
504
506
506
503
509
516
20,788
26,113
19,084
17,892
22,109
16,443
17,295
600
596
600
598
592
586
592
3.437
1.55
93
92
94
92
89
77
76
492
482
486
483
483
489
498, 612
17,638
14,943
15,001
13,800
15,792
15,060
13,390, 4863
e
e
e
e
e
e
e
e
e
e
e
e
e
e
1.757
1.426
0.972
1.065
1.032
DMF (f)
DMSO (g)

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
97
Table 4
Effect of solvents on photo physical properties of dyes 6d and 60d.
Solvents
6d
60d
lmax (nm)
Ɛ Molar absorptivity
lemi (nm)
Emission
intensity
Dl (nm)
lmax (nm)
Ɛ Molar
lemi (nm)
Emission
intensity
(dm3 molꢁ1 cmꢁ1
)
absorptivity
(dm3 molꢁ1 cmꢁ1
)
CHCl3 (a)
EtOAc (b)
1,4-Dioxane (c)
Ethanol (d)
ACN (e)
507
504
504
507
504
510
513
13,645
12,330
9864
12,288
12,535
12,576
12,165
601
603
601
605
607
611
617
5.961
2.069
1.757
2.887
1.547
2.135
2.010
94
99
97
419
416
417
417
417
420
420
8479
10,147
9618
8868
9368
e
e
e
e
e
e
e
e
e
e
e
e
e
e
98
103
101
104
DMF (f)
DMSO (g)
9785
9424
Table 5
Effect of solvents on photo physical properties of dyes 6e and 60e.
Solvents
6e
60e
lmax (nm)
Ɛ Molar
lemi (nm)
Emission
intensity
Dl (nm)
lmax (nm)
Ɛ Molar
lemi (nm)
Emission
intensity
absorptivity
absorptivity
(dm3 molꢁ1 cmꢁ1
)
(dm3 molꢁ1 cmꢁ1
)
CHCl3 (a)
EtOAc (b)
1,4-Dioxane (c)
Ethanol (d)
ACN (e)
495
494
500
524
503
506
644
24,089
8840
24,707
3005
3580
16,000
8132
594
572
588
598
562
590
709
3.618
3.302
3.876
5.127
4.347
3.862
0.174
99
78
88
74
59
84
65
506
488
9053
11,772
e
e
e
e
e
e
e
e
e
e
e
e
e
e
399, 612
402, 546
429, 573
438, 582
438, 582
7817, 9609
6705, 11,031
8219, 13,039
9331, 15,511
9331, 15,511
DMF (f)
DMSO (g)
6a
6a
Wavelength (nm)
Wavelength (nm)
Where, a= chloroform, b= ethyl acetate, c= 1,4-dioxane, d= ethanol, e= acetonitrile,
f= N,N-dimethylformamide, g= dimethylsulfoxide.
Fig. 5. Effect of solvent polarity on photo physical properties of azo disperse dyes 6a.
Fig. 6. Effect of solvent polarity on photo physical properties of azo disperse dyes 6b.

98
M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
Fig. 7. Effect of solvent polarity on photo physical properties of azo disperse dyes 6c.
6d
6d
Wavelength (nm)
Wavelength (nm)
Where, a= chloroform, b= ethyl acetate, c= 1,4-dioxane, d= ethanol, e= acetonitrile,
f= N,N-dimethylformamide, g= dimethylsulfoxide.
Fig. 8. Effect of solvent polarity on photo physical properties of azo disperse dyes 6d.
6e
6e
Wavelength (nm)
Wavelength (nm)
Where, a= chloroform, b= ethyl acetate, c= 1,4-dioxane, d= ethanol, e= acetonitrile,
f= N,N-dimethylformamide, g= dimethylsulfoxide.
Fig. 9. Effect of solvent polarity on photo physical properties of azo disperse dyes 6e.

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
99
6'a
6'b
Wavelength (nm)
6'c
Wavelength (nm)
6'd
Wavelength (nm)
Wavelength (nm)
6'e
Wavelength (nm)
Where, a= chloroform,b= ethyl acetate, c= 1,4-dioxane, d= ethanol, e= acetonitrile,
f= N,N-dimethylformamide, g= dimethylsulfoxide.
Fig. 10. Effect of solvent polarity on UVevisible absorption spectra of dyes 60aee.
Table 6
UVeVis absorption and fluorescence maxima of dyes 6aee at pH 2 to 12.
pH 6a
labs
6b
6c
6d
6e
lemi
Dl labs
lemi
Dl labs
lemi
Dl labs
lemi
Dl labs
lemi
Dl
(intensity)
(intensity)
(intensity) (intensity)
(intensity)
(intensity)
(intensity)
(intensity)
(intensity)
(intensity)
2
4
6
8
495 (2.383) 592 (0.076) 97 490 (2.400) 602 (0.89) 112 495 (2.393) 596 (0.156) 101 500 (2.384), 614 (0.114) 114 495 (2.353) 586 (0.370) 91
575 (2.619)
495 (2.395) 602 (0.027) 107 495 (2.391) 598 (0.054) 103 495 (2.394) 596 (0.098) 101 505 (2.342), 612 (0.168) 107 495 (2.364) 580 (0.372) 85
575 (2.524)
505 (2.314) 590 (0.16)
85 495 (2.395) 590 (0.181) 95 495 (2.411) 594 (0.098) 99 495 (2.407), 612 (0.112) 117 495 (2.344) 570 (0.798) 75
575 (2.647)
495 (2.397) 590 (0.120) 95 495 (2.388) 588 (0.368) 93 495 (2.415) 594 (0.076) 99 500 (2.367), 612 (0.161) 112 495 (2.169) 578 (0.670) 83
575 (2.554)
10 495 (2.368), 592 (0.107) 97 495 (2.381) 588 (0.178) 93 490 (2.459), 588 (0.021) 98 505 (2.317), 610 (0.168) 105 495 (2.458), 578 (0.017) 83
635 (1.261) 575 (2.457) 645 (2.437)
12 495 (2.346) 592 (0.128) 97 495 (2.365) 588 (0.217) 93 490 (2.454), 592 (0.016) 102 505 (2.31), 610 (0.186) 105 495 (2.488), 580 (0.012) 85
635 (1.171) 575 (2.429) 645 (2.377)

100
M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
Fig. 11. UV visible absorption and emission spectra of dye 6a at various pH.
6b
pH 02
pH 04
pH 06
pH 08
pH 10
pH 12
6b
Wavelength (nm)
Wavelength (nm)
Fig. 12. UV visible absorption and emission spectra of dye 6b at various pH.
Fig. 13. UV visible absorption and emission spectra of dye 6c at various pH.
Fig 14. UV visible absorption and emission spectra of dye 6d at various pH.

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
101
Fig. 15. UV visible absorption and emission spectra of dye 6e at various pH.
Table 7
3.3.3. Fastness to light
Fastness properties of azo disperse dyes 6aee.
Light fastness is the degree to which a dye resists fading due to
light exposure. All dyes have some susceptibility to light damage
which fully depends on molecular structure. Dye 6c shows good to
very good light fastness and others show good light fastness
according to the AATCC Test method.
Dye no. Light
Wash
Staining on fabric Sublimation Staining on fabric
fastness fastness after washing
(1e8)
fastness
after sublimation
(1e5)
(1e5)
(1e5)
(1e5)
Polyester Cotton
Polyester Cotton
6a
6b
6c
6d
6e
5
4
6
4
4
4
4e5
4e5
5
4e5
5
5
5
4
4
4
4e5
4
5
4
4
3e4
4
4e5
3
4
4
5
4
4
4e5
4e5
5
3.4. Color assessment
5
5
The colorimetric parameters of dyed polyester fabrics using
synthesized azo disperse dyes 6aee were recorded on a reflectance
spectrophotometer CE-7000A Gretag-Macbeth. The color values of
synthesized azo disperse dyes 6aee on polyester fabrics were
determined by using CIE 1976 Color Space method in terms of
L*, a* and b* and tabulated in Table 8. All dyes have good affinity
toward the polyester fabrics at high temperature and gave red
shades on polyester fabrics. The values of color coordinates
suggested that the color hue of all dyes shifted toward the redder
direction on the redegreen axis as well as toward the yellowish
direction on yelloweblue axis as positive values of a* and
b* respectively. Dye 6a is redder as well as yellower than other azo
disperse dyes (a*, b*values from Table 8). Color strength of all dyes
applied on polyester fabrics are expressed as K/S values which
dependent on type of substituent present on aromatic ring. The K/S
values are in the range of 0.81e1.47.
Table 8
Color values of azo disperse dyes 6aee.
Dye No.
L*
a*
b*
c*
ho
K/S
6a
6b
6c
6d
6e
49.29
50.42
51.66
33.40
56.52
54.25
51.51
50.88
41.92
29.13
30.99
25.56
26.88
15.10
8.50
62.48
57.50
57.55
44.56
30.34
29.74
26.39
27.85
19.81
16.27
1.335
1.218
1.248
1.469
0.812
depended on heat treatment. Sublimation properties of azo
disperse dyes 6aee also show good ratings according to the inter-
national geometric gray scale. The dyes 6a and 6d showed good to
very good rating for sublimation fastness and staining on the
undyed polyester as well as cotton fabrics.
Table 9
Comparison between fastness properties of 2-naphthol azo disperse dyes and 2-naphthol benzothiazolyl azo disperse dyes.
2-Naphthol azo disperse dyes
Structure
2-Naphthol benzothiazolyl azo disperse dyes
Color
Light fastness Wash fastness
Structure
Color
Light fastness Wash fastness
Cl
Cl
N
N
Orange
1e2
4
Red
5
4
N
N
OH
S
OH
N
[6a]
[6'a]
(continued on next page)

102
M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
Table 9 (continued)
N
N
N
N
Orange
2e3
4
Red
4
4e5
OH
OH
N
[6b]
S
[6'b]
NO2
NO2
N
N
Orange
3
4
Brownish red
6
4e5
N
N
OH
S
OH
N
[6c]
[6'c]
OCH3
OCH3
N
N
Reddish orange
2
4e5
Red
4
5
N
N
OH
OH
N
[6d]
S
[6'd]
O2N
O2N
OH
N
OH
N
N
N
Brown
3e4
4
Blackish red
4
5
N
OH
S
OH
[6e]
[6'e]
3.5. Comparison study
dyes 6aee from 3 were synthesized and compared with the dyes
60aee obtained from 2-naphthol in place of 3.
Azo disperse dyes derived from the coupler 2-naphthol are
known to have deficiency in their light fastness properties [27]. To
overcome this deficiency we introduced heterocyclic benzothia-
zolyl ring ortho to hydroxyl group present on naphthalene moiety.
This may enhance the fastness properties. Therefore dispersed azo
A comparative account of fastness rating data is compiled in
Table 9. It is observed that the dyes from 3 have uniformly higher light
fastness properties on polyester as compare to the dyes from 2-
naphthol. The presence of benzothiazolyl ring adjacent to hydroxyl
group has decisive role in enhancing the photo stability of these dye

M.A. Satam et al. / Dyes and Pigments 96 (2013) 92e103
103
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6aee. The occurrence of ESIPT as shown in Fig. 1 may be held
responsible for the enhanced photo stability and hence light fastness.
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4. Conclusion
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[25] Elgmeie GH, Helal MH, Ahmed KA. Synthesis and dyeing properties of new
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We have successfully synthesized azo disperse dyes using 3-
(1,3-benzothiazol-2-yl)naphthalen-2-ol as a coupler. All these
disperse dyes give red shades on polyester fabric. Comparison study
proves that inclusion of heterocyclic benzothiazolyl ring enhance
the fastness properties. Synthesized azo disperse dyes 6aee show
fluorescence with lower intensity in various pH solutions and in
different organic solvents.
Acknowledgment
[26] Zollinger H. Color chemistry synthesis, properties and applications of organic
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Theauthorsare greatlythankfultoSAIF, I.I.T. Mumbaiforrecording
the 1H-NMR andMassspectra.Oneof theauthors(ManjareeSatam) is
grateful to UGC-CAS for providing fellowship under SAP.
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