Azo-8-hydroxyquinoline dyes: The synthesis, characterizations and determination of tautomeric properties of some new phenyl- and heteroarylazo-8-hydroxyquinolines

Article abstract of DOI:10.1016/j.molliq.2014.02.027

Two series of new heterocyclic and carbocyclic disperse azo dyes based on 8-hydroxyquinoline were prepared and characterized by FT-IR, ¹H NMR, mass spectroscopic techniques and elemental analysis. Their solvatochromic properties in different solvents were investigated and their absorption spectra were strongly solvent dependent. The acid and base effects on this equilibrium were also examined. In addition, the colors of dyes were discussed with respect to the nature of the carbocyclic and heterocyclic rings and substituent therein. To determine the tautomeric forms of the prepared dyes in solid state, X-ray data for 5-(5-methylthiazol-2-yldiazenyl)-8-hydroxyquinoline were recorded. The X-ray results showed that the dye exists as an azo tautomer in the solid state.

Full text of DOI:10.1016/j.molliq.2014.02.027

MOLLIQ-04160; No of Pages 10
Journal of Molecular Liquids xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
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Azo-8-hydroxyquinoline dyes: The synthesis, characterizations and
determination of tautomeric properties of some new
phenyl- and heteroarylazo-8-hydroxyquinolines
⁎
4Q1 Aytül Saylam, Zeynel Seferoğlu, Nermin Ertan
5
Gazi University, Faculty of Science-Art, Department of Chemistry, 06500 Teknikokullar, Ankara, Turkey
OOF
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a r t i c l e i n f o
a b s t r a c t
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Article history:
Two series of new heterocyclic and carbocyclic disperse azo dyes based on 8-hydroxyquinoline were prepared 19
and characterized by FT-IR, 1H NMR, mass spectroscopic techniques and elemental analysis. Their solvatochromic 20
properties in different solvents were investigated and their absorption spectra were strongly solvent dependent. 21
The acid and base effects on this equilibrium were also examined. In addition, the colors of dyes were discussed 22
with respect to the nature of the carbocyclic and heterocyclic rings and substituent therein. To determine the tau- 23
tomeric forms of the prepared dyes in solid state, X-ray data for 5-(5-methylthiazol-2-yldiazenyl)-8- 24
hydroxyquinoline were recorded. The X-ray results showed that the dye exists as an azo tautomer in the solid 25
Received 25 November 2013
Received in revised form 6 February 2014
Accepted 25 February 2014
Available online xxxx
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Keywords:
Phenylazo
state.
26
Heteroarylazo
8-Hydroxyquinoline
Azo-hydrazone
Absorption spectra
Solvent effect
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© 2014 Elsevier B.V. All rights reserved.
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1. Introduction
The chemical properties of quinoline and its derivatives have been 54
widely discussed because of their biological relevance, coordination ca- 55
pacity and their use as metal extracting agent [23]. They have attracted 56
special interest due to their therapeutic properties. On the other hand, 57
quinoline sulfonamides have been used in the treatment of cancer, 58
tuberculosis and malaria [24]. Several quinoline derivatives possess che- 59
motherapeutic activity and act as antimalaria and antiallergic agents 60
[25]. They show broad-spectrum efficiency against multiple herpes 61
viruses and they have a potential role for the treatment of a variety of 62
infections [26]. 8-Hydroxyquinoline is one of the most important 63
derivatives of quinoline because of its chelator properties for important 64
metal ions [27]. 8-Hydroxyquinoline and its derivatives have high anti- 65
bacterial activities [28,29]. Some of the 8-hydroxyquinoline derivatives 66
and their complexes with transition metals were reported to be active 67
against some bacteria and DNA [30,31]. In addition, azo compounds 68
based on 8-hydroxyquinoline derivatives play a central role as chelating 69
agents for a large number of metal ions [1,2,5,30–42]. Although 8- 70
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36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
It is well known that, because of their versatile application in various
fields such as the dyeing of textile fibers, the coloring of different
materials and biological–medicinal studies, the azo compounds are
the most widely used class of dyes. They are also used in the fields of
non-linear optics (NLO), optical data storage, advanced applications in
organic synthesis and analytical chemistry as acid–base, redox and
metallochromic indicator [1–5].
In recently, monoazo dyes have became the most important type of
azo dyes. The monoazo dyes based on heterocyclic amines have been
developed and the resultant dyes have higher tinctorial strength and
give brighter than those derived from aniline-based diazo components.
For instance, amino-substituted thiazole, benzothiazole, isothiazole,
thiadiazole, and thiophene compounds afford very electronegative diazo
components and consequently, provide a pronounced bathochromic
effect compared to the benzenoid compounds [6–12]. In addition, hetero-
cyclic coupling compoUnent sNuch asCpyridOone, pRyrazoloRne, pEyrimidCine, TED PR
hydroxyquinoline azo dyes have bacteriostatic action, they have not 71
thiophene, quinoline, and indole derivatives is also very important for in-
dustrial and other advanced applications [1]. Therefore, the synthesis and
investigation of spectroscopic properties of many monoazo dyes contain-
ing one or two heterocyclic rings in molecule have been studied in the
past decades [7–22].
been an indication of commercial value as textile dyes [43]. On the 72
other hand, 8-hydroxyquinoline azo dyes derived from the sulfonamide 73
derivatives were employed on textiles. Mordant dyeing with these acid 74
azo dyes showed very good fastness properties on wool and nylon fi- 75
bers [44]. In addition, some 8-hydroxyquinoline and azo derivatives 76
found numerous applications in analytical chemistry as chromophoric 77
and metallochromic indicators [45]. Although many papers were 78
described in the synthesis and some properties of phenylazo-8- 79
⁎
Corresponding author. Tel.: +90 312 2021105; fax: +90 312 2122279.
E-mail address: nertan@gazi.edu.tr (N. Ertan).
http://dx.doi.org/10.1016/j.molliq.2014.02.027
0167-7322/© 2014 Elsevier B.V. All rights reserved.
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A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
Fig. 1. Synthetic pathway and structure of phenylazo-8-hydroxyquinolines (I 1–10).
80
hydroxyquinolines [37,39,40,43,45], only few heteroarylazo-8-
8Q1 2 hydroxyquinolines were synthesized [38,46–49]. However, the
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
solvatochromic properties of these dyes were not investigated in detail.
In our previous paper, we synthesized some new heteroarylazo 8-
hydroxyquinoline dyes and evaluated their tautomeric equilibria in
solution. In continuation of our work, we aimed to find new data for
supporting tautomeric equilibria of these dyes. For this purpose, some
novel various substituted heteroarylazo-8-hydroxyquinoline dyes
were synthesized and their absorption spectra were compared with
the absorption spectra of substituted phenylazo-8-hydroxyquinolines
in various solvents. The color of the dyes was discussed in relation to
the nature of the carbocyclic and heterocyclic rings and the substituents
therein. Acid–base effects on the absorption spectra of the dyes were
also studied in detail. The molecular structures of 5-(5-methylthiazol-
2-yldiazenyl)-8-hydroxyquinoline obtained by X-ray diffraction
analysis were also evaluated. 5-(2-carboxyphenyldiazenyl)-8-
hydroxyquinoline was also used as a model compound for the
determination of tautomeric equilibria of phenylazoquinoline dyes.
Fig. 3. Azo-hydrazone tautomeric and anionic form of phenyl- and heteroarylazo-8-
hydroxyquinolines.
dyes may exist in two possible tautomeric forms, namely azo form 107
A and hydrazone B as depicted in Fig. 3. The deprotonation of two 108
tautomers leads to common anion C (Fig. 3).
109
The infrared spectra of the prepared dyes (I 1–10 and II 1–12) (in KBr) 110
showed strong and broad band within the range 3448–3147 cm−1 corre- 111
sponding to quinoline νO\H. The broad value reveals that the \OH group 112
was involved in intra- and intermolecular H-bonding. Some researcher 113
suggested that 8-hydroxyquinolines and their phenylazo derivatives con- 114
tain intramolecular H-bond in solid state [50,51]. The other study showed 115
that they were stable in azo form because of intermolecular H-bond in 116
solid state [37,52,53]. On the other hand, Basu Baul and co-workers sug- 117
gested that phenylazo-8-hydroxyquinoline dyes were in azo form and 118
may contain intra- and intermolecular H-bond in solid state [40].
119
In this work, to determine the tautomeric forms of the dyes in solid 120
state, X-ray data for 5-(5-methyl-2-thiazolylazo)-8-hydroxyquinoline 121
(II-2) (Figs. 4 and 5) were recorded. Suitable single crystals were obtain- 122
ed by slow evaporation from ethanol/H2O in one week. The crystal struc- 123
ture of this dye showed only strong intramolecular H-bond between the 124
hydroxy H and the quinoline N atoms (O\H\N = 2.212 Å). This result 1Q235
suggests that the synthesized dyes can be stable as azo in solid state. The 126
other νmax values at 3077–3040 (aromatic CH), at 2986–2851 (aliphatic 127
98
99
2. Results and discussion
The phenylazoquinoline dyes (I 1–10) were prepared by cou-
100 pling 8-hydroxyquinoline with diazotized aniline derivatives with
101 NaNO2 in HCl/H2O mixture (Fig. 1). The heteroarylazoquinoline
102 dyes (II 1–12) were prepared by coupling 8-hydroxyquinoline
103 with diazotized 2-aminothiazole, 2-aminobenzothiazole derivatives
104 and 2-aminobenzimidazole in nitrosyl sulfuric acid (Fig. 2). The
105 structures of prepared dyes have been confirmed by FT-IR, 1H
106 NMR, mass spectral data and elemental analysis. The all prepared
CH) were recorded.
128
Fig. 2. Structure of heteroarylazo-8-hydroxyquinolines (II 1–12).
Fig. 4. Structure of a molecule of dye II-2 in the crystal.
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A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
3
Fig. 6. Azo-hydrazone tautomeric equilibrium of 5-(2-carboxyphenyldiazenyl)-8-
hydroxyquinoline (I-7-o).
disperse azo dyes and compared absorption maxima of the dyes in 147
different solutions.
148
8-Hydroxyquinoline based azo dyes theoretically may be involved in 149
azo-hydrazone tautomerism (Fig. 3). The visible absorption spectra of 150
the phenylazo-8-hydroxyquinoline dyes I 1–9 showed one absorption 151
maximum in chloroform with the exception of the dye I-10. These re- 152
sults showed that the dyes were in favor of the predominantly single 153
OOF
tautomeric form in chloroform. The absorption spectra of dye I-10 ex- 154
hibit one absorption maximum at 478 in methanol, at 445 in DMSO 155
and one absorption maximum with shoulder in chloroform, acetic acid 156
and acetonitrile and two absorption maxima in DMF (Table 1). The ap- 157
pearance of two absorption maxima in some solvents attributed two 158
forms of the dyes in these solvents. In DMF, the phenylazo-8- 159
hydroxyquinolines dyes exhibit two absorption maxima or one absorp- 160
tion maximum with a shoulder. Similar results were also observed in 161
DMSO. These results suggest that dyes prepared exist as mixture of 162
two tautomeric forms in DMSO and DMF. The determination of the 163
most stable tautomeric form for 8-hydroxyquinoline type azo dyes is 164
quite important for potential using field such as textile industry, optical 165
data storage, molecular probe etc. In our study, in order to determine 166
the most stable tautomeric form of the phenylazo-8-hydroxyquinoline 167
dyes in solution, 5-(2-carboxyphenyldiazenyl)-8-hydroxyquinoline 168
(I-7-o) has been used as model compound for dye I-7. This model 169
compound was synthesized by the reaction of 2-aminobenzoic acid 170
with 8-hydroxyquinoline. The dye I-7-o may contain intramolecular 171
H-bond between COOH with hydrazone NH (Fig. 6) or COOH with 172
azo group. The absorption spectra of dye I-7-o and dye I-7 were com- 173
pared to decide the most stable tautomeric form of dyes. The absorp- 174
tion spectra of dye I-7-o exhibit one absorption maximum at 521 nm 175
in DMF (Fig. 7a), at 490 nm in methanol (Fig. 7b). On the other hand, 176
the dye I-7 exhibit two absorption maxima at 408 and 523 nm in 177
DMF. Dye I-7-o exhibited significantly larger bathochromic shifts 178
compared to dye I-7 in DMF and methanol. For instance, Δλmax 179
value of I-7-o is 90 nm in methanol relative to I-7 in the same solvent 180
(Fig. 7a and b). These large bathochromic shifts are attributed to azo- 181
Fig. 5. A partial packing diagram of dye II-2.
129
The 1H NMR spectra of aromatic protons of dyes in the 8-
130 hydroxyquinoline ring appeared at δ 9.40–9.20 doublet, δ 9.00–8.90
131 doublet, δ 8.30–7.90 doublet, δ 7.80–7.60 multiplet and δ 7.30–7.10
132 doublet. The \OH protons of 8-hydroxyquinoline ring were not ob-
133 served in DMSO-d6 or DMSO-d6 and CDCl3 mixtures at 25 °C except of
134 dyes I-2, I-6, II-5, and II-10 [37]. These dyes showed a broad peak at δ
135 10.80, 10.80, 9.40, and 8.00 for quinoline \OH respectively. Dye I-4
136 showed a broad peak at δ 9.70 for \NHCOCH3. Dye I-7 showed a
137 broad peak at δ 12.50 for \COOH. Dye II-12 showed a broad peak at δ
138 12.32 for benzimidazole \NH. The other 1H NMR, IR and mass data of
139 the dyes prepared are shown in the Experimental section.
140 2.1. Solvent effect on absorption spectra of compounds in various solvents
141
142
143
144
145
146
Although many papers on azo-hydrazone tautomerism of
hydroxyazo dyes have been published, the determination of the tauto-
meric structure is important because the tautomeric equilibrium strong-
ly depends on the nature of the corresponding medium [54–58]. In order
to investigate the tautomeric equilibria of phenylazo- and heteroarylazo-
8-hydroxyquinoline dyes (I 1–10 and II 1–12) in detail, we prepared
t1:1
t1:2
Table 1
Influence of solvent on λmax (nm) of phenylazoquinoline dye I (1–10).
t1:3
t1:4
λ max (nm)
UNCORRECTED PR
Dye no.
Q
Chloroform
Acetic acid
Methanol
Acetonitrile
DMF
DMSO
t1:5
I-1
I-2
I-3
I-4
I-5
I-6
I-7
I-7o
I-8
I-9
I-10
Phenyl
p-CH3
p-OPh
p-NHCOCH3
p-OC2H5
p-Cl
p-COOH
o-COOH
p-COCH3
p-CN
384
386
391
394
394
390
397
426, 453, 542s
402
383
384
376
395
375, 427s
390
401, 481s
469
399, 494
400, 482
417, 469s
385, 465s
388, 468s
390
403, 475s
390
394, 474s
400
490
382
384
390, 493s
395
390
388, 492s
395
503
398
401
392, 499
398, 501
401, 512s
416, 518
403, 496s
403, 524
408, 523
521
396
397
407, 508
417, 517s
410, 508s
406
t1:6
t1:7
t1:8
t1:9
t1:10
t1:11
t1:12
t1:13
t1:14
t1:15
413
397, 510
417, 560
425, 570
445
405
410
478
413, 569
416, 562
433, 633
405
414, 515s
p-NO2
413, 495s
t1:16 s: shoulder.
Please cite this article as: A. Saylam, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.02.027

4
A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
Fig. 8. Absorption spectra of dye II-7 in various solvents.
band may be assigned to the hydrazone form for the phenylazo-8- 190
hydroxyquinolines. These observations are in agreement with previ- 191
ous works [6,13,54–56].
192
Mono- or bis heteroarylazo disperse dyes tend to show larger 193
solvatochromic and bathochromic effects than phenylazodyes because 194
of the increased polarity of the dye system, especially in the excited 195
state. Thus, they are preferred more than phenylazo analogs especially 196
in industrial applications [1]. The absorption spectra of heteroarylazo- 197
8-hydroxyquinoline dyes prepared (except of dye II-3) showed one ab- 198
sorption maximum in chloroform whereas they showed two absorption 199
maxima or one absorption maximum with a shoulder in other solvents 200
used (Table 2). In addition, dyes II-5 and II-6 have a broad band at long 201
wavelength with low intensity in acetonitrile, DMSO and DMF. This 202
broad band attributed the CT bands (charge-transfer). Dye II-7 has 2Q043
also CT band at long wavelength in methanol, acetonitrile, DMSO and 204
DMF (Fig. 8). Although the dyes II-3, II-11 and II-12 exhibit two absorp- 205
tion maxima in acetic acid, other dyes exhibit one absorption maximum 206
in this solvent. These results suggest that these dyes (II-3, II-11 and II- 207
12) may exist as a mixture of two tautomeric forms in acetic acid 208
(azo-hydrazone). The spectra of dye II-4 in chloroform and acetic acid 209
show one maximum at 438 nm and 441 nm respectively, whereas in 210
DMSO and DMF the intensity of this band is decreased and a new 211
more intensive band is appeared at the 565 and 562 nm and also two 212
absorption bands are observed at 432 and 554 nm and at 444 and 213
544 nm in acetonitrile and methanol. Thus, the absorption curves al- 214
most pass through an isosbestic point approximately 505 nm character- 215
istic of equilibria (Fig. 9). Similar results were observed for dye II-10 216
(Fig. 10). This equilibrium may exist between the tautomeric forms 217
Fig. 7. Absorption spectra of dye I-7 and I-7-o a) in DMF, b) in methanol.
182 hydrazone tautomerism. Thus it can be explained that I-7-o is stable
183 as hydrazone form in DMF and methanol due to intramolecular H-
184 bond between COOH with hydrazone NH. Similar results were also
185 observed by Sawicki in 5-(2-methoxycarbonylphenyldiazenyl)-8-
186 hydroxyquinoline [59]. On the other hand, it is known that the
187 hydrazone form generally absorbs at a longer wavelength than azo
188 form for these type compounds. Therefore, at the shorter wavelength
189 band may be assigned to the azo form and at the longer wavelength
t2:1
t2:2
Table 2
Influence of solvent on λmax (nm) of heteroarylazoquinoline dye II (1–12).
t2:3
t2:4
λ max (nm)
Dye no.
Q
Chloroform
Acetic acid
Methanol
Acetonitrile
DMF
DMSO
t2:5
II-1
II-2
II-3
II-4
II-5
II-6
II-7
II-8
II-9
II-10
II-11
II-12
Thiazole
5-Methylthiazole
428
436
491, 589s
438
516
456
462
442
450
435
440
457, 542
441
501
457
455
444
452
434, 517s
439
581
444, 544
539
550
552, 741
444s, 552
464, 568s
518
492
430s, 526
425, 548
434, 551
582
445s, 556
444, 557
591
434s, 562
565, 721
566, 731
567, 740
562
564
570
569
427s, 555
443
448, 563
593
432s, 565
570, 732
569, 737
570, 739
489, 572s
461s, 564
506
t2:6
t2:7
5-(4-Nitrophenyl sulfonyl)thiazole
4-Ethylthiazolacetate
4-Phenylthiazole
4-(4-Chlorophenyl)thiazole
4-(4-Bromophenyl)thiazole
Benzothiazole
6-Chlorobenzothiazole
6-Methoxybenzothiazole
5,6-Dimethylbenzothiazole
Benzimidazole
t2:8
432, 554
546, 716
449, 548, 730
560, 733
428s, 560
447, 559
457, 561
449, 573s
431, 547
t2:9
t2:10
t2:11
t2:12
t2:13
t2:14
t2:15
t2:16
461
456
437
469
457, 562
441, 554
570
430s, 558
t2:17 s: shoulder.
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A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
5
Fig. 11. Absorption spectra of dye I-3 in acidic and basic solvents.
Fig. 9. Absorption spectra of dye II-4 in various solvents.
OOF
common anion form, or the other tautomer. In the other solvents, the 224
dyes exhibit equilibria (azo-hydrazone or azo-anion). 225
To determine the observed equilibrium, we examined the absorp- 226
tion spectra of the dyes prepared in acidic and basic media. The dyes 227
prepared from carbocyclic amines (I 1–10) exhibit significant change 228
at the absorption maxima, when a small amount of piperidine was 229
added to the solutions in DMF, DMSO and chloroform (Table 3). In the 230
case of dyes I 3–5, I–8 and I–9, the addition of piperidine to their dye so- 231
lutions in DMSO, maxima at the shorter wavelength disappeared and 232
λmax values at longer wavelength did not significantly change or shift 233
to bathochromic region (Fig. 11). Similar effects were observed in the 234
addition of piperidine in DMF solution of all phenylazo-8- 235
hydroxyquinolines. These results indicate that the phenylazo-8- 236
hydroxyquinoline dyes (I 1–10) in DMF and the dyes I 3–5, I-8 and I-9 237
in DMSO exist in a partly dissociated state. Therefore, the absorption 238
maxima of these dyes in basic solutions are assigned to common 239
anion form. The absorption maxima of prepared phenylazo-8- 240
hydroxyquinoline dyes in chloroform are also sensitive to the addition 241
of piperidine and λmax of the dyes shifts to bathochromic and two ab- 242
sorption maxima appeared with the addition of piperidine in chloro- 243
form solution except for dye I-10. This equilibrium may exist between 2Q464
azo and common anion forms. The dye I-10 exhibits one absorption 245
maximum at short wavelength (414 nm) and shoulder at long wave- 246
length (515 nm) in chloroform. The shoulder has very low intensity. 247
When 0.2 mL piperidine was gradually added to the dye solution in 248
chloroform, firstly the intensity of shoulder increased and turned to a 249
maximum, the intensity of absorption band at short wavelength de- 250
creased at the same time. And then, the absorption maximum at short 251
Fig. 10. Absorption spectra of dye II-10 in various solvents.
218 (azo and hydrazone) or between one tautomeric form and anionic form
2Q195 because the equilibrium depends on the solvents used. In proton donat-
220 ing solvents such as acetic acid and chloroform, the dye give a
221 hypsochromic shift of λmax and are basically in the neutral form (azo
222 or hydrazone). In proton-accepting solvents, such as DMSO and DMF,
223 the dye gives a bathochromic shift of λmax and may exist mainly in the
t3:1
t3:2
Table 3
Absorption maxima of phenylazoquinoline dyes I (1–10) in acidic and basic solution.
t3:3
t3:4
λ max (nm)
UNCORRECTED PR
Dye no.
Q
DMSO
DMSO +
piperidine
DMF
DMF +
piperidine
Methanol
Methanol +
KOH
Methanol +
HCl
Chloroform
Chloroform +
piperidine
t3:5
I-1
I-2
I-3
I-4
I-5
I-6
I-7
I-8
I-9
I-10
Phenyl
p-CH3
p-OPh
p-NHCOCH3
p-OC2H5
p-Cl
p-COOH
p-COCH3
p-CN
396
397
407, 508
417, 517s
410, 508s
406
526
522
528
531
523
534
531
573
571
636
392, 499
398, 501
401, 512s
416, 518
403, 496s
403, 524
408, 523
413, 569
416, 562
433, 633
515
516
520
522
513
530
525
572
568
634
385, 465s
388, 468s
390
403, 475s
390
394, 474s
400
405
480
478
484
486
482
490
493
525
521
550
366
368
374
381
377
375
389
394
384
386
391
394
394
390
397
402
387, 473s
390, 478s
401, 479s
405, 481
402, 468s
395, 484s
391, 491s
421, 516
432s, 520
541
t3:6
t3:7
t3:8
t3:9
t3:10
t3:11
t3:12
t3:13
t3:14
413
417, 560
425, 570
445
410
478
396
396, 546
405
414, 515s
p-NO2
t3:15 s: shoulder.
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A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
Fig. 12. Absorption spectra of dye I-10 in chloroform and in addition of piperidine
(0.05–0.2 mL).
Fig. 13. Absorption spectra of dye II-3 in DMF and in addition of acetic acid solvents
(0.5–2.5 mL).
252 wavelength converts to shoulder. Finally, this shoulder disappeared and
253 the absorption maximum at long wavelength appeared at 541 nm
254 (Fig. 12). This result showed that the dye I-10 exists predominantly
255 one tautomeric form (azo or hydrazone) in chloroform and common
256 anion form in basic chloroform solution.
DMSO and DMF and therefore it assigned to anionic form in DMSO 278
and DMF. In addition, the absorption band of this dye shifted 279
hypsochromically and two absorption bands appeared with the 280
addition of acetic acid to its DMF solution. When 2.5 mL acetic acid 281
was gradually added to the dye solution in DMF, two absorption 282
maxima were observed (Fig. 13). This absorption curve is similar to 283
the ones in acetic acid. These results show that the dye II-3 exists 2Q874
in anionic form in DMF (λmax = 591 nm) and in both tautomeric 285
257
Similarly, when 0.1 mL KOH was added to methanolic solutions of
258 the phenylazo-8-hydroxyquinoline dyes, the absorption maxima of
259 the dyes shifts bathochromically (for dye I-1 Δλmax = 95 nm, for dye
260 I-8 Δλmax = 120 nm relative to their methanolic solution). These
261 bands are assigned to anionic form. On the other hand, λmax values of
262 the dyes in methanol showed small hypsochromic shifts when 0.1 M
263 HCl was added (for dyes I-1 and I-6 Δλmax = 19 nm, for dye I-2
264 Δλmax = 20 nm and for dye I-4 Δλmax = 22 nm). These data indicate
265 that the phenylazo-8-hydroxyquinolines may be converted into a
266 cationic form or the other tautomeric forms in acidic medium.
forms in acetic acid (λmax = 457, 542 nm).
286
The absorption bands of heteroarylazo dyes prepared in chloroform 287
are sensitive to the addition of piperidine and the absorption maxima of 288
the dyes shift to bathochromic. Two absorption maxima (for dye II-5), 289
one absorption maximum with a shoulder (for dye II-2) or one absorp- 290
tion maximum (for dyes II-1, II-3, 4 and II 6–12) appeared with the ad- 291
dition of piperidine in chloroform solution. The longest wavelength 292
absorption maximum is attributed to the anionic form. Similar effects 293
were observed when a small amount of 0.1 M KOH was added to 294
methanolic solutions of the dyes. In the case of dyes II-1 and II-4, the ad- 295
dition of 0.1 M KOH to their methanolic solution, maximum (dyes II-1 296
and II-4) at the shorter wavelength disappeared. λmax value at the lon- 297
gest wavelength did not significantly change for dye II-4. But the ab- 298
sorption maximum of dye II-1 at longer wavelength shifts to 299
bathochromic. The other dyes showed one absorption maximum at 300
long wavelength in basic methanolic solution. When 0.1 M HCl was 301
added to methanolic solutions of the dyes, λmax values of the dyes 302
showed hypsochromic shifts except of II 1, 2, II-9, II-11 and II-12. The 303
267
The effects of the acid and base on the absorption maxima of the
268 heteroarylazo-8-hydroxyquinolines were also investigated and the re-
269 sults are shown in Table 4. There was a significant change in the spectra
270 of the dyes II-1, II-2, II-4, II 8–10 and II-12 when a small amount of pi-
271 peridine was added to their solutions in DMSO. The absorption spectra
272 of the other dyes didn't exhibit significant change. Similar effects were
273 observed when the addition of piperidine to their solutions in DMF ex-
274 cept of dyes II-1, II-2, II-4 and II-12. This indicates that some
275 heteroarylazo-8-hydroxyquinolines exist in partial or full dissociated
276 state in DMSO and DMF. For example, the absorption spectra of dye
277 II-3 didn't change with the addition of piperidine to its solutions in
t4:1
t4:2
Table 4
Absorption maxima of heteroarylazoquinoline dyes II (1–12) in acidic and basic solution.
t4:3
λ max (nm)
Dye no.
Q
DMSO
DMSO +
piperidine
DMF
DMF +
piperidine
Methanol
Methanol +
KOH
Methanol +
HCl
Chloroform
Chloroform +
piperidine
t4:4
t4:5
II-1
II-2
II-3
II-4
II-5
II-6
II-7
II-8
II-9
II-10
II-11
II-12
Thiazole
5-Methylthiazole
443
448, 563
593
432s, 565
570, 732
569, 737
570, 739
489, 572s
461s, 564
506
562
564
592
565
574, 722
571
572
566
566
445s, 556
444, 557
591
434s, 562
565, 721
566, 731
567, 740
562
564
570
569
427s, 555
556
560
589
562
570, 727
567, 735
567, 736
561
563
569
434, 517s
439
581
444, 544
539
550
552, 741
444s, 552
464, 568s
518
492
430s, 526
542
544
581
547
547
553
553
561
564
563
563
532
423, 548
434, 564s
430
431, 557s
431, 540s
469
458
538
444, 525
472
455, 551
462, 552
428
436
491,589 s
438
516
456
462
442
450
535
446s, 535
594
540
534, 695
540
547
552
563
557
t4:6
t4:7
5-(4-Nitrophenyl sulfonyl)thiazole
4-Ethylthiazolacetate
4-Phenylthiazole
4-(4-chlorophenyl)thiazole
4-(4-Bromophenyl)thiazole
Benzothiazole
6-Chlorobenzothiazole
6-Methoxybenzothiazole
5,6-Dimethylbenzothiazole
Benzimidazole
t4:8
t4:9
t4:10
t4:11
t4:12
t4:13
t4:14
t4:15
t4:16
573
572
559
461
456
437
570
430s, 558
568
556
557
528
t4:17 s: shoulder.
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A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
7
304 dyes II-9, II-11 and II-12 have two absorption maxima with the addition
3. Experimental
367
368
305 of HCl to methanolic solution. It can be suggested that these dyes exist in
306 the mixture of azo and hydrazone forms in acidic methanolic solution.
307 On the other hand, the charged transfer band of dye II-7 disappeared
308 with the addition of HCl to methanolic solution of the dye. At the
309 same time the absorption maximum of this dye at 552 nm shifts to
310 458 nm. The absorption spectra of II-7 in methanolic HCl solution,
311 being nearly the same as those observed in acetic acid and chloroform.
312 The results indicate that heteroarylazo-8-hydroxyquinoline dyes may
313 exist as one tautomeric form or mixture of two tautomeric forms in
314 acidic methanolic solution.
3.1. General
The chemicals used in the synthesis of all compounds were pur- 369
chased from Sigma-Aldrich Chemical Company and used without fur- 370
ther purification. The solvents used were of spectroscopic grade. IR 3Q791
spectra were recorded on a Mattson 1000 FT-IR spectrophotometer in 372
KBr (ν are in cm−1). 1H NMR spectra were recorded on a Bruker- 373
Spectrospin Avance DPX 400 Ultra-Shield in DMSO-d6. Chemical shifts 374
are expressed in δ units (ppm). Ultraviolet–visible (UV–vis) absorption 375
spectra were recorded on a Analytik Jena Specord 200 spectrophotom- 376
eter at the wavelength of maximum absorption (λmax, in nm) in the sol- 377
vents specified. λmax values of the dyes were investigated when 0.1 mL 378
piperidine was added to 1 mL of dye solutions in DMSO and DMF. The 379
methanolic solutions of the dyes were examined, when 0.1 mL KOH 380
(0.1 M) or 0.1 mL HCl to 1 mL of the dye solutions was added. In addi- 381
tion, λmax was investigated when the solution of dyes in DMSO and 382
DMF was examined over the temperature range 25–70 °C.
Elemental analyses were recorded on LECO CHNS 932 by Turkish Re- 384
search Council Laboratories (Center of Science and Technology Research 385
of Turkey). Mass spectra were recorded on an Agilent 5973 Network 386
Mass Selective Detector, SIS (Direct Insertion Probe) and AGILENT 387
1100 MSD (electron impact 70 and 100 eV).
315 2.2. Substituent effect on absorption spectra of dyes in various solvents
316
It is well known that λmax values of dyes tend to be related to the
317 electronic effects in chromophoric system. The bathochromic shifts
318 can be obtained by enhancing the electron acceptor properties of the
319 diazo component. In our obtained results, this bathochromic shifts
320 was seen by enhancing the electron acceptor properties of substituents
321 (Table 1). In the carbocyclic series, the introduction of electron-
322 accepting substituents, such as NO2, CN, COCH3 and COOH in the para
323 position of the phenyl ring results in a significant bathochromic shifts
324 according to unsubstituted analog (for dye I-7 Δλmax = 15 nm, for
325 dye I-8 Δλmax = 20 nm, for dye I-9 Δλmax = 25 nm and for dye I-10
326 Δλmax = 93 nm in methanol relative to dye I-1). Similarly, with the
327 introduction of electron-donating substituents such as CH3, OC2H5
328 at the para position into phenyl ring, absorption maxima shift
329 bathochromically according to unsubstituted analogs (for dye I-5
383
OOF
388
3.2. Crystallography
389
The X-ray diffraction data collection was performed on a Bruker-AXS 390
SMART CCD Detector diffractometer equipped with MoK\a (λ = 391
0.71073 Å) radiation using w-scans. The intensity data were corrected 392
for Lorentz polarization [60] and absorption [61] effects. The structure 393
was analyzed by Crystal Maker 3D data visualization program. Crystal- 394
lographic data are obtained from the Cambridge Crystallographic Data 395
330 Δλmax = 14 nm in DMSO, Δλmax = 10 nm in chloroform, Δλmax
=
331 8 nm in acetonitrile relative to dye I-1; for dye I-2 Δλmax = 1 nm in
332 DMSO, Δλmax = 3 nm in methanol, Δλmax = 2 nm in chloroform, rela-
333 tive to dye I-1). On the other hand, the introduction of electron-
334 donating or electron-accepting substituents at the para position into
335 phenyl ring, one absorption maximum was observed in chloroform ex-
336 cept p-NO2 derivative. This shows that, these dyes exist predominantly
337 in one tautomeric form (azo) in chloroform. These results are in
338 agreement with those obtained for 4-phenylazo-1-naphthol and 5-
339 phenylazo-8-hydroxyquinolines [6,55,57,58]. In addition, the introduc-
340 tion of electron-accepting substituents into phenyl ring caused the ab-
341 sorption maxima of the dyes to shift more bathochromically than
3Q428 electron-donating substituted dyes.
Centre with CCDC 725346.
396
3.3. Preparation of phenylazo-8-hydroxyquinoline dyes (I 1–9)
397
2 mmol carbocyclic amine was dissolved in HCl (1.5 mL) and water 398
(4 mL). The solution was cooled in an ice-salt bath and a cold solution of 399
NaNO2 (0.15 g, 2 mmol) in water (3.0 mL) was added dropwise with 400
stirring. The resulting diazonium salt was also cooled in an ice-salt 401
bath. Excess nitrous acid was destroyed by the addition of urea. And 402
then added dropwise with stirring to 8-hydroxyquinoline (0.29 g, 403
2 mmol) in KOH, cooled in an ice-salt bath. The solution was stirred at 404
0–5 °C for 1 h and the pH of the reaction mixture was maintained at 405
4–6 by the simultaneous addition of saturated sodium acetate solution 406
(15–20 mL). The mixtures were stirred for further 1 h. The resulting 407
solid was filtered off, washed with cold water and dried. The obtained 408
compounds were purified by crystallization using ethanol and then an- 409
alyzed. The yields of the dyes are in the range of 75–85%. Characteriza- 410
343
In the heterocyclic series, the introduction of 4-nitrophenylsulfonyl
344 group into the thiazole ring at the 5-position gives the largest
345 bathochromic shift compared with the other heteroarylazo-8-
346 hydroxyquinoline dyes in all solvents used (for dye II-3 Δλmax
=
347 150 nm in DMSO, Δλmax = 63 nm in chloroform, Δλmax = 34 nm in ace-
348 tonitrile relative to dye II-1; Δλmax = 23 nm in DMSO, Δλmax = 26 nm
349 in DMF, Δλmax = 42 nm in methanol, relative to dye II-5). On the other
350 hand, the presence of a phenyl substituent in the 4-position of the thia-
351 zole ring gives rise to a bathochromic shift relative to thiazole (II-1) and
tion data are below.
411
352 4-ethylthiazolacetate (II-4) in all solvents used (for dye II-5 Δλmax
353 127 nm in DMSO, Δλmax = 88 nm in chloroform, Δλmax = 66 nm in
354 acetic acid relative to dye II-1; Δλmax = 5 nm in DMSO, Δλmax
=
3.3.1. Preparation of 5-(phenyldiazenyl)-8-hydroxyquinoline (I-1)
412
=
This dye was obtained from aniline and 8-hydroxyquinoline as yel- 413
UNCORRECTED PR
355 60 nm in acetic acid, Δλmax = 78 nm in chloroform, relative to dye
low crystalline (yield: 0.39 g, 78%; m.p. 186–187 °C, lit: 182–183 °C 414
[40]; 185–185.5 °C [50]). IR(KBr): νmax: 3409–3147 (quinoline OH), 415
356 II-4). In addition, the dyes II 5–7 showed intramolecular CT band at
357 the NIR (for dye II-7 λmax = 741 nm in methanol, 733 nm in acetoni-
358 trile, 740 nm in DMF and 739 in DMSO) in methanol, acetonitrile,
359 DMSO and DMF due to π-donating properties of phenyl substituent.
360 The introduction of electron-donating and accepting substituents
361 into benzothiazole ring, absorption maxima shift to bathochromic
362 in chloroform and acetic acid but in the other solvents did not signif-
363 icantly change (for dye II-9 Δλmax = 2 nm in DMF, Δλmax = 8 nm in
364 chloroform, Δλmax = 8 nm in acetic acid relative to dye II-8, for dye
3063 (aromatic CH), 1580, 1510 (C_C), 1240 (C\O) cm−1 1H NMR 416
;
(DMSO-d6/CDCl3): δ 9.40 (d,1H), 8.95 (d,1H), 8.10 (d,1H), 7.95 (d,2H), 417
7.70 (m,1H), 7.55 (m,2H), 7.50 (m,1H), 7.30 (d,1H). Anal. calcd. for 418
C15H11N3O (249.27): C, 72.28; H, 4.45; N, 16.86. Found C, 71.97; H, 419
4.59; N, 16.76.
420
MS: (m/z, 100 eV): 250 (M + 1)+, 172, 144.
421
3.3.2. Preparation of 5-(4-methylphenyldiazenyl)-8-hydroxyquinoline (I-2) 422
This dye was obtained from 4-aminotoluidine and 8- 423
hydroxyquinoline as yellow crystals (yield: 0.39 g, 75%; m.p: 188– 424
365 II-10 Δλmax = 8 nm in DMF, Δλmax = 19 nm in chloroform, Δλmax
366 25 nm in acetic acid relative to dye II-8).
=
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8
A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
425 189 °C, lit: 188–189 °C [40]). IR (KBr): νmax: 3435–3242 (quinoline OH),
426 3063 (aromatic CH), 2960 (aliphatic CH), 1573, 1510 (C_C), 1227
427 (C\O) cm−1; 1H NMR (DMSO-d6): δ 10.80 (br, OH), 9.30 (d,1H), 9.00
428 (d,1H), 8.00 (d,1H), 7.90 (d,2H), 7.80 (m,1H), 7.40 (d,2H), 7.20 (d,1H),
429 2.40 (s,3H)). Anal. calcd. for C16H13N3O (263.29): C, 72.99; H, 4.98; N,
430 15.96. Found C, 72.97; H, 4.84; N, 16.05.
229 °C). IR (KBr): νmax: 3281 (quinoline OH), 3050 (aromatic CH), 485
2979, 2928 (aliphatic CH), 1676 (C_O), 1573, 1510 (C_C), 1227 486
(C\O) cm−1 1H NMR (DMSO-d6): δ 9.20 (d,1H), 8.90 (d,1H), 8.07 487
;
(d,2H), 7.90–8.00 (m,3H), 7.70 (m,1H), 7.10 (d,1H), 2.57 (s,3H). Anal. 488
calcd. for C17H13N3O2 (291.3): C, 70.09; H, 4.50; N, 14.42. Found C, 489
69.98; H, 4.52; N, 14.35.
490
431
MS: (m/z, 70 eV): 264 (M + 1)+, 263 (M+), 179, 146.
MS: (m/z, 70 eV): 291 (M+), 292 (M + 1)+, 146.
491
432 3.3.3. Preparation of 5-(4-phenoxyphenyldiazenyl)-8-hydroxyquinoline
433 (I-3)
3.3.9. Preparation of 5-(4-cyanophenyldiazenyl)-8-hydroxyquinoline (I-9) 492
This dye was obtained from 4-cyanoaniline and 8-hydroxyquinoline 493
as orange powder (yield: 0.44 g, 80%; m.p: 261–262 °C). IR (KBr): νmax: 494
3256 (quinoline OH), 3063 (aromatic CH), 2222 (C ≡ N), 1573, 1510 495
434
This dye was obtained from 4-phenoxyaniline and 8-
435 hydroxyquinoline as orange powder (yield: 0.58 g, 85%; m.p: 156–
436 157 °C). IR (KBr): νmax: 3268 (quinoline OH), 3056 (aromatic CH),
(C_C), 1234 (C\O) cm−1 1H NMR (DMSO-d6): δ 9.20 (d,1H), 8.90 496
;
437 1573, 1510 (C_C), 1240 (C\O) cm−1
;
1H NMR (DMSO-d6): δ 9.20
(d,1H), 7.90–8.05 (m,5H), 7.70 (m,1H), 7.10 (d,1H). Anal. calcd. for 497
C16H10N4O (274.28): C, 70.06; H, 3.67; N, 20.43. Found C, 69.94; H, 498
438 (d,1H), 8.90 (d,1H), 8.00 (d,2H), 7.90 (d,1H), 7.70 (m,1H), 7.40
439 (m,2H), 7.20–7.00 (m,6H)). Anal. calcd. for C21H15N3O2 (341.36): C,
440 73.89; H, 4.43; N, 12.31. Found C, 74.04; H, 4.40; N, 12.41.
3.60; N, 20.36.
499
MS: (m/z, 100 eV): 275 (M + 1)+, 145.
500
441
MS: (m/z, 100 eV): 342 (M + 1)+, 172, 144.
3.3.10. Preparation of 5-(4-nitrophenyldiazenyl)-8-hydroxyquinoline (I-10) 501
This dye was obtained from 4-nitroaniline and 8-hydroxyquinoline 502
as violet powder (yield: 0.49 g, 83%; m.p: 274–275 °C). IR (KBr): νmax: 503
3433 (quinoline OH), 3077 (aromatic CH), 1560, 1539 (C_C), 1217 504
442 3.3.4. Preparation of 5-(4-acetamidophenyldiazenyl)-8-hydroxyquinoline
443 (I-4)
444
This dye was obtained from 4-acetamidoaniline and 8-
445 hydroxyquinoline as orange powder (yield: 0.48 g, 78%; m.p: 265–
(C\O) cm−1 1H NMR (DMSO-d6/CDCl3): δ 9.30 (d,1H), 8.95 (d,1H), 505
;
446
447
448
266 °C). IR (KBr): νmax: 3275 (acetamido NH), 3070 (aromatic CH),
8.45 (d,2H), 8.20 (d,1H), 8.10 (d,2H), 7.80 (m,1H), 7.15 (d,1H). Anal. 506
calcd. for C15H10N4O3 (294.26): C, 61.22; H, 3.43; N, 19.04. Found C, 507
2960 (aliphatic CH), 1696, 1670, 1592, 1510 (C_C), 1240 (C\O) cm−1
;
1H NMR (DMSO-d6/CDCl3): δ 9.70 (b, NH-COCH3), 9.30 (d,1H), 8.90
(d,1H), 8.00 (d,1H), 7.90 (d,2H), 7.80 (d,2H), 7.60 (m,1H), 7.20 (d,1H),
2.20 (s,3H). Anal. calcd. for C17H14N4O2 (306.32): C, 66.66; H, 4.61; N,
18.29. Found C, 66.70; H, 4.58; N, 18.47.
61.18; H, 3.35; N, 18.97.
508
449
450
451
452
MS: (m/z, 100 eV): 294 (M)+, 145.
509
3.4. Preparation of heteroarylazo-8-hydroxyquinoline dyes (II 1–12)
510
MS: (m/z, 100 eV): 307 (M + 1)+, 263, 146.
2 mmol heterocyclic amines were dissolved in hot glacial acetic 511
acid–propionic acid mixture (2:1, 6.0 mL) and was rapidly cooled in 512
an ice-salt bath to −5 °C. The liquor was then added in portions during 513
30 min to a cold solution of nitrosyl sulfuric acid (prepared from sodium 514
nitrite (0.15 g) and concentrated sulfuric acid, 98% (3 mL at 50 °C)). The 515
mixture was stirred for an additional 2 h at 0 °C. Excess nitrous acid was 516
destroyed by the addition of urea. The resulting diazonium salt was 517
cooled in ice–salt bath. After diazotization was complete the azo liquor 518
was slowly added to vigorously stirred solution of 8-hydroxyquinoline 519
(2 mmol, 0.29 g) in potassium hydroxide (2.0 × 10−3 mol, 0.112 g) 520
and water (2 mL). The solution was stirred at 0–5 °C for 2 h. After that 521
the pH of the reaction mixture was maintained at 4–6 by the simulta- 522
neous addition of saturated sodium carbonate solution. The mixture 523
was stirred for 1 day at room temperature. The resulting solid was fil- 524
tered, washed with cold water and dried. The obtained compounds 525
were purified by crystallization using ethanol and then analyzed. The 526
yields of the dyes are in range of 54–78%. Characterization data are 527
453 3.3.5. Preparation of 5-(4-ethoxyphenyldiazenyl)-8-hydroxyquinoline (I-5)
454
This dye was obtained from 4-ethoxyaniline and 8-
455 hydroxyquinoline as red powder (yield: 0.45 g, 85%; m.p: 182–183 °C,
456 lit: 180–181 °C [40]). IR (KBr): νmax: 3275 (quinoline OH), 3075 (aro-
457 matic CH), 2979, 2928 (aliphatic CH), 1606, 1573, 1510 (C_C), 1246
458 (C\O) cm−1 1H NMR (DMSO-d6): δ 9.30 (d,1H), 9.00 (d,1H), 8.00
;
459 (d,2H), 7.90 (d,1H), 7.70 (m,1H), 7.20 (d,1H), 7.10 (d,2H), 4.20 (q,2H),
460 1.40 (t,3H). Anal. calcd. for C17H15N3O2 (293.32): C, 69.61; H, 5.15; N,
461 14.33. Found C, 69.66; H, 5.28; N, 14.53.
462
MS: (m/z, 100 eV): 294 (M + 1)+, 279, 145.
463 3.3.6. Preparation of 5-(4-chlorophenyldiazenyl)-8-hydroxyquinoline (I-6)
464
This dye was obtained from 4-chloroaniline and 8-hydroxyquinoline
465 as yellow powder (yield: 0.46 g, 81%; m.p: 229–230 °C, lit: 220–221 °C
466 [39]). IR (KBr): νmax: 3268 (quinoline OH), 3056 (aromatic CH), 1573,
467 1510 (C_C), 1234 (C\O) cm−1; 1H NMR (DMSO-d6): δ 10.80 (br, quin-
468 oline OH), 9.30 (d,1H), 9.00 (d,1H), 8.10 (dd,3H), 7.80 (m,1H), 7.60
469 (d,2H), 7.25 (d,1H). Anal. calcd. for C15H10ClN3O (283.71): C, 63.50; H,
470 3.55; N, 14.81. Found C, 63.27; H, 3.46; N, 14.77.
shown below.
528
3.4.1. Preparation of 5-(thiazol-2-yldiazenyl)-8-hydroxyquinoline (II-1) 529
This dye was obtained from 2-aminothiazole and 8-hydroxyquinoline 530
as dark violet claret brown powder (yield: 0.29 g, 56%; m.p: 155–156 °C). 531
IR(KBr): νmax: 3448 (quinoline OH), 3070 (aromatic CH), 1573, 1510 532
471
MS: (m/z, 70 eV): 283 (M+), 172, 144.
472 3.3.7. Preparation of 5-(4-carboxyphenyldiazenyl)-8-hydroxyquinoline (I-7)
473
This dye was obtained from 4-aminobenzoic acid and 8-
(C_C), 1214 (C\O) cm−1 1H NMR (DMSO-d6/CDCl3): δ 9.28 (d,1H), 533
;
474 hydroxyquinoline as red powder (yield: 0.47 g, 80%; m.p: 281–
475 282 °C). IR (KBr): νmax: 3210–2530 (COOH, OH), 3056 (aromatic CH),
8.94 (dd,1H), 8.28 (d,1H), 8.00 (d,1H), 7.70 (m,1H), 7.45 (d,1H), 7.35 534
(d,1H). Anal. calcd. for C12H8N4OS (256.28): C, 56.24; H, 3.15; N, 21.86; 535
476 1689 (C_O), 1573, 1606, 1510 (C_C), 1246 (C\O) cm−1
;
1H NMR
S, 12.51. Found C, 56.27; H, 3.28; N, 21.87; S, 12.80.
536
477 (DMSO-d6/CDCl3): δ 12.50 (br, COOH), 9.30 (d,1H), 8.90 (d,1H), 8.20
478 (d,2H), 8.10 (d,1H), 8.00 (d,2H), 7.70 (m,1H), 7.30 (d,1H). Anal. calcd.
479 for C16H11N3O3 (293.28): C, 65.53; H, 3.73; N, 14.33. Found C, 65.46;
480 H, 3.70; N, 14.26.
MS: (m/z, 70 eV): 256 (M+), 144.
537
3.4.2. Preparation of 5-(5-methylthiazol-2-yldiazenyl)-8-hydroxyquinoline 538
(II-2) 539
481
MS: (m/z, 70 eV): 293 (M+), 172, 144.
This dye was obtained from 2-amino-5-methylthiazole and 8- 540
hydroxyquinoline as dark violet crystals (yield: 0.32 g, 60%; m.p: 541
232–233 °C). IR (KBr): νmax: 3416–3268 (quinoline OH), 3070 (ar- 542
omatic CH), 2928, 2870 (aliphatic CH), 1573, 1510 (C_C), 1208 543
482 3.3.8. Preparation of 5-(4-acetylphenyldiazenyl)-8-hydroxyquinoline (I-8)
483
This dye was obtained from 4-aminoacetophenone and 8-
484 hydroxyquinoline as orange powder (yield: 0.49 g, 85%; m.p: 228–
(C\O) cm−1 1H NMR (DMSO-d6): δ 9.10 (d,1H), 9.00 (d,1H), 544
;
Please cite this article as: A. Saylam, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.02.027

A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
9
545 8.10 (d,1H), 7.80 (m,2H), 7.30 (d,1H), 2,55 (s,3H). Anal. calcd. for
546 C13H10N4OS (270.31): C, 57.76; H, 3.73; N, 20.73; S, 11.86. Found
547 C, 57.68; H, 3.68; N, 20.71; S, 11.48.
3.4.8. Preparation of 5-(benzothiazol-2-yldiazenyl)-8-hydroxyquinoline 603
(II-8) 604
This dye was obtained from 2-aminobenzothiazole and 8- 605
hydroxyquinoline as claret red powder (yield: 0.35 g, 57%; m.p: 191– 606
192 °C, lit: 238–240 °C [49]). IR (KBr): νmax: 3288–3089 (quinoline 607
548
MS: (m/z, 70 eV): 270 (M+), 144.
OH), 3050 (aromatic CH), 1567, 1510 (C_C), 1227 (C\O) cm−1 1H 608
;
549 3.4.3. Preparation of 5-[5-(4-nitrophenylsulfonyl)thiazol-2-yldiazenyl]-8-
550 hydroxyquinoline (II-3)
NMR (DMSO-d6): δ 8.74 (dd,1H), 8.14 (dd,1H), 8.10 (d,1H), 7.40 609
(m,3H), 7.28 (d,2H), 7.10 (d,1H). Anal. calcd. for C16H10N4OS (306.34): 610
C, 62.73; H, 3.29; N, 18.29; S, 10.47. Found C, 62.65; H, 3.31; N, 18.18; 611
551
This dye was obtained from 2-amino-5-(4-nitrophenylsulfonyl)
552 thiazole and 8-hydroxyquinoline as dark brown powder (yield:
553 0.64 g, 72%; m.p: 246–247 °C). IR (KBr): νmax: 3416 (quinoline
S, 10.34.
612
MS: (m/z, 70 eV): 306 (M)+, 144.
613
554 OH), 3070 (aromatic CH), 1535, 1490 (C_C), 1252 (C\O) cm−1
555
;
1H NMR (DMSO-d6/CDCl3): δ 9.20 (d,1H), 8.90 (d,1H), 8.50 (s,1H),
3.4.9.
Preparation
of
5-(6-chlorobenzothiazol-2-yldiazenyl)-8- 614
615
556 8.40 (d,2H), 8.30 (d,2H), 8.10 (d,1H), 7.90 (m, 1H), 7.00 (d,1H).).
557 Anal. calcd. for C18H11N5O5S2 (441.44): C, 48.97; H, 2.51; N, 15.86;
558 S, 14.53. Found C, 48.65; H, 2.42; N, 15.57; S, 14.35.
hydroxyquinoline (II-9)
This dye was obtained from 2-amino-6-chlorobenzothiazole and 8- 616
hydroxyquinoline as brown powder (yield: 0.37 g, 54%; m.p: 267– 617
268 °C). IR (KBr): νmax: 3428–3191 (quinoline OH), 3063 (aromatic 618
559
MS: (m/z, 70 eV): 442 (M + 1)+, 146.
CH), 1567, 1510 (C_C), 1246 (C\O) cm−1 1H NMR (DMSO-d6/ 619
;
CDCl3): δ 9.20 (d,1H), 8.90 (d,1H), 8.25 (d,1H), 7.90–7.80 (m,3H), 7.65 620
(m,1H), 7.15 (d,1H). Anal. calcd. for C16H9ClN4OS (340.79): C, 56.39; 621
560 3.4.4. Preparation of ethyl[2-(8-hydroxyquinoline-5-yldiazenyl)-1,3-
561 thiazol-4-yl]acetate (II-4)
H, 2.66; N, 16.44; S, 9.41. Found C, 56.25; H, 2.71; N, 16.42; S, 9.26.
OOF
622
562
This dye was obtained from 2-amino-4-ethylthiazoleacetate and 8-
MS: (m/z, 100 eV): 341 (M + 1)+, 172, 144.
623
563 hydroxyquinoline as dark brown powder (yield: 0.54 g, 64%; m.p:
564 145–146 °C). IR (KBr): νmax: 3377–3133 (quinoline OH), 3050 (aromat-
565 ic CH), 2986, 2877 (aliphatic CH), 1740 (C_O), 1573, 1510 (C_C), 1227
3.4.10. Preparation of 5-(6-methoxybenzothiazol-2-yldiazenyl)-8- 624
hydroxyquinoline (II-10) 625
566 (C\O) cm−1 1H NMR (DMSO-d6): δ 9.20 (d,1H), 9.05 (d,1H), 8.20
;
This dye was obtained from 2-amino-6-methoxybenzothiazole and 626
8-hydroxyquinoline as greenish yellow powder (yield: 0.42 g 63%; 627
m.p: 250–251 °C). IR (KBr): νmax: 3050 (aromatic CH), 2940 (aliphatic 628
567 (d,1H), 7.70 (m,1H), 7.60 (s,1H), 7.20 (d,1H), 4.20 (q,2H), 3.90 (s, 2H),
568 1.80 (t, 3H).). Anal. calcd. for C16H14N4O3S (328.35): C, 56.13; H, 4.12;
569 N, 16.36; S, 9.37. Found C, 55.99; H, 4.08; N, 16.38; S, 9.49.
CH), 1567, 1510 (C_C), 1227 (C\O) cm−1 1H NMR (DMSO-d6/ 629
;
570
MS: (m/z, 100 eV): 343 (M + 1)+, 342 (M)+, 172, 144.
CDCl3): δ 9.25 (d,1H), 8.75 (d,1H), 8.30 (dd,1H), 8.00 (br, quinoline 630
OH), 7.70 (m,1H), 7.44 (s,1H), 7.40 (d,1H), 7.30 (d,1H), 7.10 (d,1H), 631
3.90 (s,3H). Anal. calcd. for C17H12N4O2S (336.37): C, 60.70; H, 3.60; N, 632
571 3.4.5. Preparation of 5-(4-phenylthiazol-2-yldiazenyl)-8-hydroxyquinoline
572 (II-5)
16.66; S, 9.53. Found C, 60.55; H, 3.61; N, 16.35; S, 9.38.
633
MS: (m/z, 100 eV): 337 (M + 1)+, 144.
634
573
This dye was obtained from 2-amino-4-phenylthiazole and 8-
574 hydroxyquinoline as dark brown powder (yield: 0.45 g, 68%; m.p:
575 218–219 °C). IR (KBr): νmax: 3486–3056 (quinoline OH), 3040 (aromat-
3.4.11. Preparation of 5-(5,6-dimethylbenzothiazol-2-yldiazenyl)-8- 635
hydroxyquinoline (II-11) 636
576 ic CH), 1650, 1522 (C_C), 1271 (C\O) cm−1 1H NMR (DMSO-d6): δ
;
577 9.37 (br, quinoline OH), 9.18 (d,1H), 9.04 (d,1H), 8.25 (d,1H), 7.98
578 (d,1H), 7.85 (m,1H), 7.63–7.45 (m,6H), 7.30 (d,1H).). Anal. calcd. for
579 C18H12N4OS (332.38): C, 65.04; H, 3.64; N, 16.86; S, 9.65. Found C,
580 64.97; H, 3.56; N, 16.88; S, 9.66.
This dye was obtained from 2-amino-5,6-dimethylbenzothiazole 637
and 8-hydroxyquinoline as claret red powder (yield: 0.36 g, 54%; m.p: 638
264–265 °C). IR (KBr): νmax: 3288 (quinoline OH), 3050 (aromatic CH), 639
2921, 2851 (aliphatic CH), 1573, 1510 (C_C), 1234 (C\O) cm−1 1H 640
;
581
MS: (m/z, 100 eV): 333 (M + 1)+, 172, 144.
NMR (CDCl3): δ 9.25 (d,1H), 8.85 (d,1H), 8.28 (d,1H), 7.85 (s,1H), 7.62 641
(m,1H), 7.57 (s,1H), 7.24 (d,1H), 2.33 (s,6H). Anal. calcd. for C18H14N4OS 642
(334.39): C, 64.65; H, 4.22; N, 16.75; S, 9.59. Found C, 64.37; H, 4.18; N, 643
582 3.4.6. Preparation of 5-[4-(4-chlorophenyl)thiazol-2-yldiazenyl]-8-
583 hydroxyquinoline (II-6)
16.70; S, 9.46.
644
MS: (m/z, 70 eV): 335 (M + 1)+.
645
584
585
586
587
588
589
590
591
592
This dye was obtained from 2-amino-4-(4-chlorophenyl)thiazole
and 8-hydroxyquinoline as dark brown powder (yield: 0.55 g, 75%;
m.p: 203–205 °C). IR (KBr): νmax: 3428–3075 (quinoline OH), 3045 (ar-
omatic CH), 1592, 1510 (C_C), 1240 (C\O) cm−1; 1H NMR (DMSO-d6):
δ 9.20 (d,1H), 9.03 (d,1H), 8.35 (d,1H), 8.08 (s,1H), 7.86 (m,1H), 7.64
(d,2H), 7.53 (d,2H), 7.30 (d,1H).). Anal. calcd. for C18H11ClN4OS
(366.82): C, 58.94; H, 3.02; N, 15.27; S, 8.74. Found C, 58.65; H, 2.96; N,
3.4.12. Preparation of 5-(benzimidazol-2-yldiazenyl)-8-hydroxyquinoline 646
(II-12) 647
This dye was obtained from 2-aminobenzimidazole and 8- 648
hydroxyquinoline as dark brown powder (yield: 0.32 g, 56%; m.p: 649
214–215 °C). IR (KBr): νmax: 3409–3070 (quinoline OH, benzimidazole 650
NH), 3055 (aromatic CH), 1567, 1458 (C_C), 1246 (C\O) cm−1 1H 651
;
15.15; S, 8.57.
MS: (m/z, 100 eV):U367 (MN+ 1C) , 17O2, 144.RRECTED PR
NMR (DMSO-d6): δ 12.32 (br, NH), 8.60 (d,1H), 8.40 (d,1H), 7.74–7.51 652
(m,4H), 7.30–7.10 (m,3H), 6.80 (s,1H). Anal. calcd. for C16H11N5O 653
+
(289.29): C, 66.43; H, 3.83; N, 24.21. Found C, 66.52; H, 3.74; N, 24.18. 654
655
593 3.4.7. Preparation of 5-[4-(4-bromophenyl)thiazol-2-yldiazenyl]-8-
594 hydroxyquinoline (II-7)
MS: (m/z, 100 eV): 290 (M + 1)+, 172, 144.
595
596
597
598
599
600
601
602
This dye was obtained from 2-amino-4-(4-bromophenyl)thiazole and
8-hydroxyquinoline as dark brown powder (yield: 0.64 g, 78%; m.p: 227–
228 °C). IR (KBr): νmax: 3448–3095 (quinoline OH), 3056 (aromatic CH),
1592, 1510 (C_C), 1240 (C\O) cm−1; 1H NMR(DMSO-d6/CDCl3): δ 9.20
(m,1H), 9.04 (d,1H), 8.15 (d,1H), 8.08 (s,1H), 7.95 (d,2H), 7.65 (d,2H),
7.85 (m,1H), 7.30 (d,1H).). Anal. calcd. for C18H11BrN4OS (411.28): C,
52.57; H, 2.70; N, 13.62; S, 7.80. Found C, 52.45; H, 2.65; N, 13.46; S, 7.76.
MS: (m/z, 100 eV): 410 (M-1)+, 172, 144.
4. Conclusions
656
In this study, some new heterocyclic and carbocyclic disperse azo 657
dyes based on 8-hydroxyquinoline have been prepared. The absorption 658
maxima of heteroarylazo-8-hydroxyquinolines shifted more to 659
bathochromic than phenylazo-8-hydroxyquinolines in all solvents 660
used except of dye I-10. Heterocyclic based azo disperse dyes showed 6Q6110
larger solvatochromic effects than azo-benzene based dyes. The solvent 662
Please cite this article as: A. Saylam, et al., J. Mol. Liq. (2014), http://dx.doi.org/10.1016/j.molliq.2014.02.027

10
A. Saylam et al. / Journal of Molecular Liquids xxx (2014) xxx–xxx
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710
663 effects on the absorption spectra of the dyes indicated that the different
664 tautomeric structures were exhibited. On the other hand, all dyes were
665 of pure anionic form or exhibited azo-common anion equilibrium in
666 DMF. It was also observed that the absorption curves of the dyes were
667 very sensitive to acids and bases. The bathochromic shifts were obtain-
668 ed by enhancing the electron acceptor properties of the carbocyclic and
669 heterocyclic diazo components. In addition, the crystal structure of the
670 dye (II-2) showed that the dye exists azo structure in solid state due
671 to strong intramolecular H-bond.
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679 Appendix A. Supplementary material
680
Crystallographic data (excluding structure factors) have been
681 deposited with the Cambridge Crystallographic Data Centre as the sup-
682 plementary publication no. CCDC 725346. These data can be obtained
683 free of charge from the Cambridge Crystallographic Data Centre via
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