Synthesis, spectral properties, biological activity and application of new 4-(benzyloxy)phenol derived azo dyes for polyester fiber dyeing

Article abstract of DOI:10.1016/j.molliq.2012.12.030

A series of hetaryl-azophenol dyes were prepared by coupling 4-benzyloxyphenol with eight heterocyclic amines in nitrosyl sulphuric acid. The structure of the prepared azo dyes was characterized by UV-Vis, FT-IR and ¹H-NMR spectroscopic techniques, as well as elemental analysis (CHN). The solvatochromism of dyes was evaluated with respect to the wavelength of maximum absorption (λ_max) in various solvents. The effects of temperature, concentration as well as acid and base on the visible absorption maxima are also reported. The newly synthesized dyes were screened for their potential antibacterial activities against four bacterial species and the results revealed significant activity against the test microorganisms in vitro. In addition, the dyes were applied to polyesters and afforded red-orange shades with excellent wash fastness properties.

Full text of DOI:10.1016/j.molliq.2012.12.030

MOLLIQ-03741; No of Pages 8
Journal of Molecular Liquids xxx (2013) xxx–xxx
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
1
2
Synthesis, spectral properties, biological activity and application of new
4-(benzyloxy)phenol derived azo dyes for polyester fiber dyeing
b
c
⁎
Q13
H. Yousefi a, A. Yahyazadeh a, , E.O. Moradi Rufchahi , M. Rassa
a
4
5
6
Department of Chemistry, Faculty of Sciences University of Guilan, Rasht, Iran
b
Department of Chemistry, Faculty of Sciences, Lahijan Branch, Islamic Azad University, Lahijan, Iran
c
Department of Biology, Faculty of Sciences University of Guilan, Rasht, Iran
7
OOF
a r t i c l e i n f o
a b s t r a c t
8
9
10
11
12
13
Article history:
A series of hetaryl-azophenol dyes were prepared by coupling 4-benzyloxyphenol with eight heterocyclic 24
amines in nitrosyl sulphuric acid. The structure of the prepared azo dyes was characterized by UV-Vis, 25
FT-IR and 1H-NMR spectroscopic techniques, as well as elemental analysis (CHN). The solvatochromism 26
of dyes was evaluated with respect to the wavelength of maximum absorption (λmax) in various solvents. 27
The effects of temperature, concentration as well as acid and base on the visible absorption maxima are 28
also reported. The newly synthesized dyes were screened for their potential antibacterial activities against 29
four bacterial species and the results revealed significant activity against the test microorganisms in vitro. 30
In addition, the dyes were applied to polyesters and afforded red-orange shades with excellent wash fastness 31
Received 24 September 2012
Received in revised form 19 December 2012
Accepted 20 December 2012
Available online xxxx
145
16
17
18
19
20
21
22
23
Keywords:
Azo dye
Benzyloxyphenol
Antibacterial activity
Dyeing
properties.
32
© 2012 Published by Elsevier B.V. 33
Fastness
Spectral properties
37
36
345
38
1. Introduction
respect to the influence of solvent. The effects of acid and base on 61
the visible absorption maxima of the dyes are reported. In addition, 62
their unique application in polyester fiber dyeing was investigated. 63
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Azo dyes (–N N–) are an important class of organic colorants used
in many practical applications [1–4]. They are successfully employed
as LCD color filters [5], chromophoric substrates for redox enzymes
[6], optical switches [7,8] chemical sensors [9,10], textile dyes [11–14],
lasers [15], optical data storage [16], non-linear optics [17–21]; and
also they have advanced applications in organic synthesis [22]. Azo
dyes containing sulfur and/or nitrogen atoms have been the subject of
many studies recently. These dyes provide bright and strong shades
that range from red to green and blue [23–26]. In addition, azothiazole
and azobenzothiazole dyes have been attracted great attention for their
spectral and eco-friendly features. They illustrate bathochromic shift as
compared to corresponding azobenzene dyes [27–29]. In this regard,
a number of studies have been devoted to the characterization, purifica-
tion and application of azo dyes as antibacterial agents [30–36]. Thus,
the aim of the present work was to prepare some new dyestuffs
containing heterocyclic moieties having acceptable antibacterial activi-
ties and fastness properties. The latter was a requirement as the dyes
would be used to dye polyester, wool nylon and garments which
would be in direct contact with human skin.
Accordingly, in this paper, we report the synthesis of some hetaryl
azophenol compounds (1–8) using 4-benzyloxyphenol as coupling
component and evaluation of their visible absorption spectra with
The compounds structures are shown in Scheme 1.
64
65
66
2. Results and discussion
2.1. Synthesis and characterization
Following the general procedure for preparation of azo dyes, diazo- 67
tization was performed by treatment of heterocyclic amines with 68
nitrosyl sulfuric acid, then the resulting diazonium salts were reacted 69
with alkaline solution of 4-benzyloxyphenol to afford azo dyes 1–8 in 70
high yields (Scheme 1). The structure of the synthesized dyes was 71
confirmed by FT-IR, 1H-NMR and elemental analyses. The prepared 72
dyes may exist in two tautomeric forms, azo form (A) and hydrazone 73
(B), as depicted in Scheme 2. Deprotonation of two tautomers leads to 74
UNCORRECTED PR
common anions (A1 and B1).
75
The IR spectra of all synthesized dyes showed the O–H stretching at 76
3350–3450 cm−1. In addition, absorption bands at 3021–3100 cm−1 77
and 2872–2970 cm−1 were attributed to the aromatic and aliphatic 78
C–H stretching vibrations, respectively. The 1H-NMR spectra were 79
recorded in CDCl3 at room temperature and showed singlets at 80
2.45 ppm (–CH3, 3), 3.90 ppm (–OCH3, 4), 5.10 to 5.16 ppm for benzylic 81
protons (–CH2Ar), a multiplet from 7.00 to 8.70 ppm for aromatic pro- 82
tons (Ar–H) and a broad peak from 11.23 to 12.45 ppm for hydroxylic 83
proton (–OH). The 1H-NMR of dyes 6 and 7 exhibit one broad peak, 84
⁎
Corresponding author. Tel./fax: +98 1313233262.
E-mail address: ayahyazadeh53@yahoo.com (A. Yahyazadeh).
0167-7322/$ – see front matter © 2012 Published by Elsevier B.V.
http://dx.doi.org/10.1016/j.molliq.2012.12.030
Please cite this article as: H. Yousefi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2012.12.030

2
H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
OH
OH
N
1) pH = 8-9
O
2) H+
O
N
Het
+
N N
Het
N
N
N
(7) Het:
(8) Het:
(4) Het:
(1) Het:
(2) Het:
N H
N
S
S
OCH3
NO2
N
N
(5) Het:
(6) Het:
S
N
S
N
S
N
(3) Het:
N
H
CH3
Scheme 1. Synthesis of azo dyes 1–8.
85
86
87
related to –NH protons, at 14.70 and 15.20 ppm, respectively. Spectro-
scopic results suggest that the synthesized dyes are predominantly in
azo form (A), both in solid state and in chloroform.
forms (A1 and B1) in DMSO and DMF, while they are predominantly 104
in the single tautomeric form in other solvents. As it can be seen in 105
Fig. 1, the absorption curves of dye 1 almost pass through an isobestic 106
point, approximately at 536 nm, which is characteristic of equilibrium. 107
This equilibrium may exist between the azo tautomeric form and the 108
88
2.2. Solvent effect on UV-Vis spectra
anionic forms A1 and B1.
109
Dye 6 showed two absorption maxima in all used solvents, indic- 110
ative of two tautomeric forms existing simultaneously in solution. In 111
contrast, dye 8 indicated just one absorption maximum, confirming 112
the fact that the azoic form dominated. Interestingly, dye 7 in DMSO 113
and acetic acid exhibited one λmax. However, the maximum in 114
DMSO was related to the anionic form whereas in acetic acid it was 115
related to the azoic form. In other solvents, it showed two absorption 116
maxima, emphasizing that both forms are present simultaneously in 117
89
90
91
92
93
94
95
96
97
98
99
Since the tautomeric equilibriums strongly depend on the nature
of the media, the behaviors of dyes in various solvents were studied.
For this purpose, the UV-Vis absorption spectra of dyes 1–8 were
measured in various solvents at 10−6 to 10−8 mol L−1. The results
are summarized in Table 1. Visible absorption spectra of the dyes
exhibited a strong solvent dependence; however, no regular variation
with the solvent polarity was observed.
The benzothiazole azo dyes 1–5 showed three absorbances in DMSO
and DMF and single absorbance in methanol, chloroform, acetonitrile
and acetic acid. It was observed that the λmax values of dyes 1–5 showed
bathochromic shifts in high polar basic solvents, e.g. DMSO and DMF,
solution (Fig. 2).
118
It was also observed that the absorption curves of the synthesized 119
dyes are not significantly sensitive to acid, whilst they are sensitive 120
to base. Absorption spectra of the dyes in methanol did not change 121
significantly by addition of 0.1 M HCl and the absorption curves are 122
similar to those in acetic acid. However, the λmax of dyes 1–8 showed 123
large bathochromic shifts when a small amount of 0.1 M KOH solution 124
100 as shown in Table 1. A typical example is shown in Fig. 1. The large
101 bathochromic shifts in basic solvents are due to deprotonation of the
102 dyes, which leads to anionic forms, A1 and B1. It can be suggested that
103 these dyes may be a mixture of tautomeric form (A) and anionic
O
H
OH
N
N
O
N
Het
O
N
Het
azo (A)
hydrazon (B)
O
O
N
O
N
Het
N
O
N
Het
A1
B1
Scheme 2. The tautomerism and anionic form of hetraylazo 4-benzyloxyphenoles.
Please cite this article as: H. Yousefi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2012.12.030

H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
3
t1:1
t1:2
Table 1
Influence of solvents on the λmax of dyes 1–8.
t1:3
Dye DMSO
DMF
Acetonitrile Methanol Acetic
Chloroform
acid
t1:4
t1:5
t1:6
t1:7
t1:8
1
2
3
4
5
474, 591 s, 483, 585,
624 s 621 s
488, 588 s, 490, 584 s, 486
623 s 619 s
495, 596 s, 497, 594 s, 481
471
470
492
492
483
506
470
480
496
490
492
520
498
493
498
532
636 s
626 s
502, 597,
639 s
499, 595 s, 492
637 s
517, 588 s, 514, 586 s, 507
642 s 638 s
443 s, 478 440 s, 474 430, 464 s
t1:9
6
7
8
434, 454 s 428, 554 s 481, 617 s
441, 548 s 444
427 430
t1:10
t1:11
550
440
452 s, 540 468, 550 s
437 429
454, 632 s
431
t1:12 s=shoulder.
Fig. 2. Absorption spectra of dye 7 in various solvents.
125 was added to each dye solution in methanol. A typical example is
126 shown in Fig. 3. These results indicate that the dyes may exist in a
127 dissociated (anionic) tautomeric form in strongly basic solutions.
Buffer standard solutions with pH 1.33, 2.01, 4.37, 6.71, 7.02, 8.27, 153
8.57, 8.87, 9.20, 10.12, 12.39O, and 13O.47 weFre prepared with traditional 154
128
The absorption spectra of dyes 1 to 8 were determined in aqueous
procedure from distilled deionized water and ethanol with HCl, NaOH, 155
H3PO4, KHC8H4O4, KH2PO4, H2B4O7, NaHCO3, KCl, and Na2CO3. In most 156
cases, the pH needed to be adjusted using a pH meter and the drop 157
wise addition of either 1 M HCl or 1 M NaOH to 1 L of solution. The 158
accurate pH for each buffer solution was measured with a Jenway 159
model 3505 digital pH meter. Typical absorbance–pH curve is showed 160
129 solution in different pH values at room temperature and are given
130 in Table 2. Each compound exhibits two bands in the region of 479–
131 588 nm and 421–528 nm for anionic and the molecular species,
132 respectively. As the pH value of the solution increases, the height of
133 the former band increases and simultaneously that of the latter
134 band decreases. From the optical spectra, in each case, the isobestic
135 points indicate that two species are in equilibrium (Fig. 4).
in Fig. 5.
161
As an example, Fig. 6 shows the photograph of the 2-thiazolylazo- 162
4-benzyloxy phenol (dye 1) solutions at different pHs obtained from 163
buffer solutions. It is possible to appreciate the pH-dependence of the 164
136
For all of these dyes, the changes of color were extremely sharp
137 and clear in the pH range 7.02–9.20 (Table 2). Sensitive acid–base re-
138 action property of the compounds can be explained by the formation
139 of a π system within the whole dye structures. From the UV-Vis ab-
140 sorption spectra based on the varying basicity, a pH-dependent
141 equilibrium between molecular species (HIn) (acidic medium) and
142 its deprotonated form (In−) (basic medium) was established in a
143 mixture of sodium hydroxide and EtOH/H2O system. The dyes were
144 yellow or red in acidic medium (0.1 mol L−1 HCl). While, as the pH
145 values were increased, the color of the medium changed dramatically
146 to blue-violet in the pH range 7.02–9.20. As a result of the reaction be-
147 tween acid and base forms, a considerable increase in the absorption
148 intensity was observed in this pH range, exhibiting the color transi-
149 tion property necessary for pH indicators. Also color changes were
150 reversible and the dyes were stable in acidic and alkali conditions.
151 Consequently, these compounds could potentially be used as pH
152 indicators.
color variation in solution.
165
To further our study, we evaluated the effects of substituent and 166
extension of resonance system on absorption maximum of the syn- 167
thesized heterocyclic dyes (Table 1). Evaluations show that thiazolyl 168
derivatives have a higher maximum wavelength relative to dyes 169
containing isoxazole, triazole and pyridine. This bathocromic shift in 170
absorption maximum of thiazolyl dyes has been attributed to the ex- 171
istence of sulfur, either alone or in combination with nitrogen atoms 172
in the chemical structures of such dyes. As it is apparent in Table 1, 173
the introduction of an electron-accepting nitro group into position 6 174
on benzothiazole ring results in a hypsochromic shift in all solvents 175
as compared to electron-donating, methyl and methoxy groups 176
(for dye 3 Δλ=30 nm and for dye 4 Δλ=28 nm, relative to dye 5 177
for spectra in chloroform). Also dye 2, including benzothiazole ring, 178
UNCORRECTED PR
Fig. 1. Absorption spectra of dye 1 in various solvents.
Fig. 3. Absorption spectra of dye 3 in acidic and basic solutions.
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4
H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
t2:1
t2:2
Table 2
Influence of pH on λmax of dyes 1–8.
t2:3
Dye pH 1.33 pH 2.01 pH 4.37
pH 6.71 pH 7.02 pH 8.27
pH 8.57
pH 8.87
pH 9.20
pH 10.12 pH 12.39 pH 13.47
t2:4
t2:5
t2:6
t2:7
t2:8
t2:9
t2:10
t2:11
1
2
3
4
5
6
7
8
471
493
488
492
520
421
431
431
469
492
488
492
521
422
432
432
471
491
490
492
521
469
491
490
492
528
469
491
491
492
528
429
435
437
472, 561 s
492, 610 s
491, 618 s
473, 563 s
473, 565 s
561, 472 s
563
588
586
584
563
585
588
586
587
481
542
514
565
588
588
587
587
481
543
514
493, 584 s, 617 s 493, 584 s, 617 s 614, 584, 492 s
492, 584 s, 618 s 492, 584 s, 618 s 618, 584, 493 s
500, 582 s, 620 s 502, 582 s, 620 s 502, 582 s, 620 s 620, 583, 502 s
518, 585 s, 634 s 518, 585 s, 635 s 518, 585 s, 635 s 635, 585 s, 518 s 586
442, 479 s
441, 547 s
437
428, 538 s 428
432
432
442, 479 s
441, 548 s
439
442, 479 s
442, 549 s
439
442, 479 s
442, 542 s
439, 510 s
479
542
510
435
432
t2:12 s=shoulder.
179 shows bathochromic shifts due to the extended resonance system in
180 comparison with dye 1.
3. Experimental
208
209
181
The effects of concentration and temperature on the absorption
3.1. Materials and methods
182 maxima of dyes were also examined and the results are listed in
183 Table 3. The λmax values of synthesized dyes did not change signifi-
184 cantly by altering the dye concentration in chloroform, acetonitrile,
185 methanol, DMSO and DMF, except for dye 4 and dye 8 in acetonitrile,
186 in which a red shift appeared as the concentration increased. Con-
187 sidering the influence of temperature, a solution of each dye in
188 chloroform, acetonitrile, methanol, DMSO and DMF were prepared
189 and examined in a temperature range of 25–70 °C. The results show
190 few changes in λmax values of the dyes 1–8 as the temperature was
191 increased.
All reagents were purchased from Merck and Aldrich Chemical 210
Companies and used without further purification. IR spectra were 211
recorded on a shimadzu 8400 FT-IR spectrophotometer. 1H-NMR 212
spectra of the dyes were recorded on a Bruker 400 spectrometer in 213
CDCl3 as solvent and TMS as the internal standard. Microanalytical 214
data for CHN were performed on a Perkin-Elmer 2400 (II) elemental 215
analyzer. The absorption spectra of the compounds were scanned 216
on a Cary UV-Vis double-beam spectrophotometer (Model 100). 217
Melting points were recorded with an Electro-thermal apparatus.
218
3.2. The general procedure for the synthesis and purification of disperse 219
azo dyes 220
192 2.3. Antibacterial activity
193
The antibacterial activity of the dyes at various concentrations
For the preparation of dyes 1–8, the diazonium coupling reaction 221
was employed. The procedure is presented in Scheme 1. Nitrosyl 222
sulfuric acid solution was prepared from concentrated sulfuric acid 223
(1.5 mL) and sodium nitrite (0.14 g, 2 mmol) at 70 °C and then 224
cooled to 5 °C. This solution was added dropwise, with stirring, to a 225
mixture of 3 mL of acetic acid and propionic acid (5:1 v/v) containing 226
2 mmol of heterocyclic amines in an ice bath. The mixture was then 227
stirred for 1.5 h at 0–5 °C. After completion of the diazotization 228
procedure, the diazonium salt solution was added dropwise to 229
the solution of coupling compound (2 mmol) in sodium hydroxide 230
(2 mmol) and water (3 mL). The resulting solution was vigorously 231
stirred at 0–5 °C for 1.5 h, while the pH of the reaction mixture was 232
maintained close to 8–9 by adding 2.5 % sodium hydroxide solution. 233
The progress of the reaction was followed by TLC using an ethyl 234
acetate-petroleum ether mixture (4:1). After completion of the reac- 235
tion, the pH of the reaction mixture was regulated at 5–6 by means 236
194 is shown in Tables 4 to 7. The comparative effect of all the dyes on
195 Pseudomonas aeruginosa is shown in Fig. 7, as an example. In general,
196 dye 5 showed the most potent effect, being comparable to tetracycline
197 and penicillin (Fig. 8). Dye 7 showed the second highest activity
198 against the bacteria. It may be speculated that these two dyes were
199 more active due to the presence of more polar groups or formation
200 of hydrogen bonds with groups on bacterial surfaces. Escherichia coli
201 and Micrococcus luteus strains were more sensitive to the dyes than
202 the Bacillus subtilis or Pseudomonas aeruginosa strains. This is not sur-
203 prising as the two latter species are some of the most resistant envi-
204 ronmental bacteria. It can also be observed that antibacterial effect
205 of the dyes is not Gram-specific, as Escherichia coli and Pseudomonas
206 aeruginosa are Gram negative, whilst Bacillus subtilis and Micrococcus
207 luteus are Gram positive.
Fig. 5. Effect of pH on the maximum absorption intensity of 2-thiazolylazo-4-benzyloxy
phenol (dye 1, 0.1%, w/v in 80% ethanol).
Fig. 4. Absorption spectra of dye 1 at different pH values.
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H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
5
OOF
Fig. 6. Color observed for dye 1 solution at different pH values.
t3:1
t3:2
Table 3
Influence of temperature and sample concentration on absorption maxima of dyes 1–8.
t3:3
Dye DMSO conc. DMSO dil.
DMSO
(70 °C)
DMF conc. DMF dil.
λmax (nm)
DMF (70 °C) (25 °C)
A. nitrile conc. A. nitrile dil. Meth. conc. Meth. dil.
Chl. conc.
(25 °C)
Chl. dil.
(25 °C)
(25 °C)
(25 °C)
(25 °C)
(25 °C)
(25 °C)
(25 °C)
(25 °C)
t3:4
t3:5
t3:6
t3:7
t3:8
1
2
3
4
5
472, 591 s,
624 s
485, 591 s,
623 s
495, 596 s,
636 s
499, 597,
639 s
472, 591 s, 474, 590 s, 483, 582,
620 s 621 s 624 s
486, 588 s, 488, 586 s, 492, 580 s, 491, 582 s, 490, 584 s,
623 s 623 s 620 s 622 s 619 s
495, 596 s, 495, 635 s 495, 596 s, 497, 594 s, 497, 592 s,
485, 588,
622 s
483, 584,
621 s
471
484
480
504
505
471
472
470
480
492
491
494
521
480
496
491
495
520
482
484
492
506
494
488
482
503
492
489
485
502
636 s
628 s
626 s
626 s
502, 597,
639 s
500, 597,
640 s
499, 598 s, 501, 595 s, 500, 595 s,
637 s
638 s
512, 581,
640 s
637 s
515, 587,
641 s
517, 588,
640 s
515, 583,
641 s
517, 584,
642 s
512, 582,
639 s
t3:9
6
7
8
443 s, 478
554
440
440 s, 477 443 s, 478 442 s, 472 442 s, 474 440 s, 474
432, 464 s
470, 552 s
442
430, 464 s
466, 552 s
429
436, 452 s
441, 548 s
429
434, 454 s 481, 617 s 481, 617 s
441, 548 s 454, 632 s 454, 632 s
t3:10
t3:11
550
440
551
442
455 s, 540 452 s, 540 452 s, 540
438 438 437
430
432
431
t3:12 Chl.: chloroform, Meth.: methanol, A. nitrile: acetonitrile, conc.: concentrated, dil.: diluted.
237 of a 10 % hydrochloric acid solution. The resulting solid was filtered,
238 washed thoroughly with cold water and dried. Recrystallization
239 from DMF-EtOH afforded pure crystals of the dyes.
3.3. Determination of antimicrobial activity
242
The antibacterial activities of the dyes were determined against 243
Escherichia coli, Pseudomonas aeruginosa, Micrococcus luteus and 244
Bacillus subtilis, using the well diffusion method. Each bacterium 245
240
Supplementary data are also available for the products showed in
241 Scheme 1.
t4:1
t4:2
t4:3
Table 4
Table 5
t5:1
Antibacterial activity of test compounds against Escherichia coli (diameter of inhibition
zone (mm)).
Antibacterial activity of test compounds against Pseudomonas aeruginosa (diameter of t5:2
inhibition zone (mm)).
t5:3
t4:4
t4:5
Test
compound
Concentration
Test
compound
Concentration
t5:4
t5:5
UNCORRECTED PR
50 μg/mL
100 μg/mL
150 μg/mL
200 μg/mL
50 μg/mL
100 μg/mL
150 μg/mL
200 μg/mL
t4:6
1
2
3
4
5
6
7
8
12
–
15
9
17
13
22
16
24
16
16
12
27
23
20
15
24
19
28
20
19
14
33
26
1
2
3
4
5
6
7
8
–
9
12
18
15
16
17
12
17
14
21
24
13
20
19
18
22
16
19
16
24
29
t5:6
t4:7
11
10
10
11
8
15
12
12
13
10
12
9
t5:7
t4:8
14
8
16
10
9
18
13
19
12
13
9
t5:8
t4:9
t5:9
t4:10
t4:11
t4:12
t4:13
t4:14
t4:15
t5:10
t5:11
t5:12
t5:13
t5:14
t5:15
10
–
–
Stda
Stdb
19
16
22
18
Stda
Stdb
18
17
19
21
t4:16 –: Resistant.
–: Resistant.
t5:16
t5:17
t5:18
a
a
t4:17
Tetracycline is used as standard.
Penicillin is used as standard.
Tetracycline is used as standard.
Penicillin is used as standard.
b
b
t4:18
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H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
t6:1
t6:2
t6:3
Table 6
concentrations (50, 100, 150 and 200 μg/mL) in DMSO and 50 μL was 251
added to the wells. After overnight growth at 37 °C, the diameters of 252
zones of growth inhibition were measured. Tetracycline and penicillin 253
Antibacterial activity of test compounds against Micrococcus luteus (diameter of inhibi-
tion zone (mm)).
t6:4
t6:5
Test
compound
Concentration
were used as positive control.
3.4. Dye uptake determination
3.4.1. Spectrophotometric analyses
In order to measure the dyes uptake, for the synthesized dyes 257
50 mg of the dyes (1–5 and 7) were dissolved in 10 mL of water-DMF 258
(25:1 v/v) solutions and sonicated for 10 minutes. The prepared solu- 259
tions were then diluted to 50 mL and absorption spectra of the obtained 260
solutions were recorded and used for characterization of the peak posi- 261
tion, λmax, and the molar absorptivity, ε, according to Beer–Lambert 262
law. Different portions (0.1, 0.2, 0.4, 0.6, 0.8 and 1 mL) of each solution 263
were subsequently diluted to 10 mL deionized water-DMF (25:1, v/v) 264
for making proper series of the standard samples. Absorptions of 265
these standard samples were recorded and the obtained data were 266
254
255
256
50 μg/mL
100 μg/mL
150 μg/mL
200 μg/mL
t6:6
1
2
3
4
5
6
7
8
17
–
21
–
24
11
22
23
25
21
12
11
27
12
28
13
26
25
29
24
15
12
30
14
t6:7
t6:8
14
14
18
11
8
18
18
21
14
9
9
23
10
t6:9
t6:10
t6:11
t6:12
t6:13
t6:14
t6:15
–
Stda
Stdb
18
9
t6:16 –: Resistant.
t6:17
a
Tetracycline is used as standard.
Penicillin is used as standard.
b
t6:18
used for development of standard curves.
267
t7:1
t7:2
t7:3
Table 7
Antibacterial activity of test compounds against Bacillus subtilis (diameter of inhibition
zone (mm)).
3.4.2. Uptake measurements
268
The prepared standard solution were diluted to 50% of their initial 269
concentrations and set as first concentrations, C0 for each dye. The 270
polyester fibers (100 mg) were then immersed and stirred according 271
to the following profile: 5 min/25 °C, 10 min/35 °C, 15 min/50 °C, 272
25 min/60 °C, 50 min/90 °C, 85 min/95 °C, 100 min/95 °C and 273
120 min/95 °C. At the end of the each period, 1 mL of the bath solu- 274
tion was removed and diluted to 10 mL with deionized water-DMF 275
(25:1 v/v) and the absorption was recorded at λmax. According to 276
the dye standard curve, the concentration of the dye in the bath solu- 277
tion was evaluated (Ci). Subsequently, the uptake percentage was 278
t7:4
t7:5
Test
compound
Concentration
50 μg/mL
100 μg/mL
150 μg/mL
200 μg/mL
t7:6
1
2
3
4
5
6
7
8
8
–
10
–
12
9
9
10
15
9
22
12
19
12
13
10
10
13
18
12
25
15
21
16
t7:7
t7:8
–
–
t7:9
–
–
t7:10
t7:11
t7:12
t7:13
t7:14
t7:15
9
–
11
–
12
–
18
8
16
10
Stda
Stdb
14
8
calculated according to the following equation:
279
t7:16 –: Resistant.
a
C0−Ci
C0
t7:17
Tetracycline is used as standard.
Penicillin is used as standard.
Uptake % ¼
ꢀ 100%
b
t7:18
2801
Fig. 9 and Table 8 show the uptake of dyes 1–5 and 7. The dye up- 282
take percentage increased as the temperature increased. It suggested 283
that the dye molecules interact more effectively with the fiber func- 284
tional groups and penetrate into the fiber structure more easily, as 285
the temperature is raised. This means that the dyestuff dyes the 286
246 was inoculated into 3 mL of nutrient broth (Merck) and after overnight
247 growth at 37 °C, 50 μL was transferred onto nutrient agar (Merck)
248 plates. The inoculum was spread using a sterile glass spreader. Wells
249 were formed in the nutrient agar by removing the agar gel using a
250 sterile Pasteur pipette end. The dyes were prepared at 4 different
fiber more easily at higher temperatures.
287
Fig. 7. Statistical representation for biological activity of dyes 1–8 against Pseudomonas aeruginosa.
Please cite this article as: H. Yousefi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2012.12.030

H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
7
OOF
Fig. 8. Statistical representation for biological activity of dye 5.
dyes. It was also observed that the absorption curves of the dyes 307
changed slightly with acid, but significantly with base. 308
288 3.4.3. Colorfastness assessment
289
The wash fastness of dyed fabrics was evaluated using AATCC test
In acidic aqueous medium, the dyes were intense yellow or red. 309
As the pH value of the solution increased, they showed a gradual 310
bathochromic shift with sharp, clear and reversible color changes in 311
the pH range 7.02–9.20. A few drops of the dye in 50 mL of solution 312
will turn the solution from yellow or red to a strong blue-violet color 313
in the mentioned pH range. As a result, the possible use of these azo 314
290 method 61-1996 No. 2A and the resultant fabrics were evaluated for
291 color change and staining [37]. The dyed fabric was rinsed with
292 water, dried at room temperature and ironed. The dyes (1–5 and 7)
293 gave a narrow range of color, varying from orange to red, with excel-
294 lent brightness, depth on fabric and deeper shade with high tinctorial
295 and excellent levelness. The washing fastness properties of the dyed
296 polyesters were evaluated and are shown in Table 9. For the assess-
297 ments, a rating scale of 1 to 5 was used. Where 1=poor, 2=fair, 3=
298 moderate, 4=good, and 5=excellent. All of the used dyes showed
299 moderate (3–4) to fairly good (4–5) fastness to wash on fabric.
dyes as an acid–base endpoint indicator should be considered.
315
All the dyes exhibited antibacterial activity. The most active, was 316
dye 5, followed by dye 7. Presence of more polar groups in these 317
dyes is likely to increase their antibacterial activities. Antibacterial 318
activity exhibited was not Gram-specific and therefore, the activity is 319
probably related to bacterial cytoplasmic membrane or to interference 320
300 4. Conclusions
301
In this study, we have synthesized some hetaryl-azo dyes by
302 linking various heterocyclic amines with 4-benzyloxyphenol as the
303 coupling component. The solvatochromic behaviors of these dyes
304 in various solvents were evaluated. The study of substituent effects
305 showed that the withdrawing group on the diazo moiety has signifi-
306 cant influence (red shift) on the electron absorption spectra of these
Table 8
t8:1
t8:2
Effect of dyeing time and temperature on the dye uptake percentage.
Dyeing
profile
Dye uptake (%)
t8:3
t8:4
Dye 1
Dye 2
Dye 3
Dye 4
Dye 5
Dye 7
5 min/25 °C
5
9
8
8
10
16
26
39
63
75
81
82
7
t8:5
10 min/35 °C
15 min/50 °C
25 min/60 °C
50 min/90 °C
75 min/95 °C
100 min/95 °C
120 min/95 °C
12
22
36
53
63
70
72
16
24
38
60
71
79
80
12
22
36
58
69
75
76
11
22
35
57
66
73
73
11
24
35
56
66
72
74
t8:6
t8:7
t8:8
t8:9
t8:10
t8:11
t8:12
UNCORRECTED PR
Table 9
Wash fastness properties for dyes 1–5 and 7 on polyester.
t9:1
t9:2
Dye
Wash fastness
color
t9:3
t9:4
Change in Shade
Staining on polyester
1
2
3
4
5
7
Red
Red
Dark red
Dark red
Reddish black
Brick orange
3–4
4–5
4
4
4–5
3
4
t9:5
t9:6
t9:7
t9:8
t9:9
t9:10
3–4
4–5
4–5
4
4
Q2
Fig. 9. Uptake of the dyes 1–5 and 7 on polyester fiber at 1 % (omf).
Please cite this article as: H. Yousefi, et al., Journal of Molecular Liquids (2013), http://dx.doi.org/10.1016/j.molliq.2012.12.030

8
H. Yousefi et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
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322 necessary to determine the mechanism of activity.
323
The dyeing of polyester fiber was also studied. Wash fastness
324 results of the new azo dyes are excellent, both in change in shade
325 and color staining.
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326 Acknowledgements
327
The authors would like to thank Dr. Mehdi Sheykhan for all
328 supports.
329 Appendix A. Supplementary data
330
Supplementary data to this article can be found online at http://
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