Synthesis, solvatochromic properties and antimicrobial activities of some novel pyridone-based disperse disazo dyes

Article abstract of DOI:10.1016/j.molliq.2013.08.005

In this study, 5-amino-4-arylazo-3-methyl-1H-pyrazoles (2a-l) were diazotized and coupled with 3-cyano-6-hydroxy-4-methyl-2-pyridone to give pyridone-based disperse disazo dyes (3a-l). The newly synthesized twelve pyridone-based disperse disazo dyes were

Full text of DOI:10.1016/j.molliq.2013.08.005

MOLLIQ-03928; No of Pages 7
Journal of Molecular Liquids xxx (2013) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids
journal homepage: www.elsevier.com/locate/molliq
1
2
Synthesis, solvatochromic properties and antimicrobial activities of some
novel pyridone-based disperse disazo dyes
b
b
c
3Q1 Fati Karcı a, , Fikret Karcı , Aykut Demirçalı , Mustafa Yamaç
⁎
a
4
5
6
Department of Chemistry and Chemical Processing Technologies, Pamukkale University, Denizli, Turkey
Department of Chemistry, Faculty of Science-Arts, Pamukkale University, Denizli, Turkey
Department of Biology, Faculty of Science-Arts, Eskişehir Osmangazi University, Eskişehir, Turkey
b
c
7
OOF
a r t i c l e i n f o
a b s t r a c t
8
9
Article history:
In this study, 5-amino-4-arylazo-3-methyl-1H-pyrazoles (2a–l) were diazotized and coupled with 3-cyano-6- 22
hydroxy-4-methyl-2-pyridone to give pyridone-based disperse disazo dyes (3a–l). The newly synthesized 23
twelve pyridone-based disperse disazo dyes were characterized by elemental analysis and spectral methods. 24
The solvatochromic properties and antimicrobial activities of these disazo disperse dyes were also examined in 25
10
11
12
Received 6 May 2013
Accepted 12 August 2013
Available online xxxx
134
15
detail.
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21
Keywords:
Disazo dyes
Solvatochromism
Antimicrobial activity
Pyridone dyes
© 2013 Elsevier B.V. All rights reserved. 27
Tautomeric structure
31
30
289
32
1. Introduction
some novel pyridone-based disperse disazo dyes which were derived 54
from 5-amino-4-arylazo-3-methyl-1H-pyrazoles as heterocyclic diazo 55
components were reported. Moreover, solvatochromic properties and 56
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36
37
38
39
40
41
42
43
44
45
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51
52
53
It is well known that nitriles are widely used as intermediates for
many heterocyclic compounds. The aminopyrazole compounds have
been easily obtained by the reaction of nitrile derivatives with hy-
drazine hydrate [1–6]. Pyrazole and pyridone derivatives are impor-
tant intermediates that possess biological and pharmacological
activities [7–10]. Some azopyrazole derivatives also find application in
dyes and complexes [11–13]. The use of heterocyclic coupling com-
ponent and diazo components in the synthesis of azo disperse dyes is
well established, and the resultant dyes exhibit good tinctorial strength
and brighter shade properties than those derived from aniline-based
components. For instance, Hallas et al. [14,15] reported the synthesis
of azo dyes derived from 2-aminothiophene derivatives and various
heterocyclic coupling components, and their application on polyester
fibers which leads to excellent results. On the other hand, the use of
amino-substituted thiazole and benzothiazole, being very electronega-
tive diazo components, produce a pronounced bathochromic shift
when compared to the corresponding benzoid compounds [16–19].
Although, many patents and papers describe the synthesis, tau-
tomeric structures and dyeing properties of monoazo dyes [20–26],
very few comparable investigations have been made with disazo dyes
[27–31]. In this study, the synthesis and antimicrobial activities of
tautomeric forms of these dyes were also examined in detail.
57
2. Experimental
58
59
2.1. General
The chemicals which were used for the synthesis of the compounds 60
were obtained from Aldrich and Merck Chemical Company without fur- 61
ther purification. The solvents used were in spectroscopic grade. IR spec- 62
tra were determined using a Mattson 1000 Fourier Transform-infrared 63
(FT-IR) spectrophotometer on a KBr disc. Nuclear magnetic resonance 64
(1H NMR) spectra were recorded on a Bruker-Spectrospin Avance 65
DPX 400 Ultra-Shield in deuterated dimethylsulphoxide (DMSO-d6) 66
using tetramethylsilane (TMS) as the internal reference; chemical shifts 67
UNCORRECTED PR
were (δ) given in ppm. Ultraviolet–visible (UV–vis) absorption spectra 68
were recorded on a Shimadzu UV-1601 double beam spectrophotome- 6Q94
ter at the wavelength of maximum absorption (λmax) in a range of 70
solvents, i.e. DMSO, DMF, acetonitrile, methanol, acetic acid and chloro- 71
form at the various concentrations (1 × 10−6–10−8). Change of λmax 72
was also investigated when 0.1 ml base (potassium hydroxide, 0.1 M) 73
and 0.1 ml acid (hydrochloric acid, 0.1 M) were added to dye solutions 74
in methanol (1 ml). Melting points were determined on an Electrother- 75
mal 9100 melting point apparatus and they are uncorrected. Elemental 76
⁎
Corresponding author. Tel.: +90 258 2135681; fax: +90 258 2118065.
E-mail address: fati@pau.edu.tr (F. Karcı).
analyses were done on a Leco CHNS-932 analyzer.
77
0167-7322/$ – see front matter © 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molliq.2013.08.005
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

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F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
78
79
2.2. Synthesis of 2-arylhydrazono-3-ketiminobutyronitriles (1a–l) and
5-amino-4-arylazo-3-methyl-1H-pyrazoles (2a–l)
NH), 13.23 (br, 1H, pyrazole NH), 15.10 (br, 1H, OH or tautomeric 118
hydrazo NH); Anal. Calcd. for C18H16N8O3: C: 55.10, H: 4.11, N: 28.56. 119
Found: C: 55.23, H: 4.07, N: 28.84.
120
80
81
82
83
84
2-Arylhydrazone-3-ketiminobutyronitriles (1a–l) and 5-amino-4-
arylazo-3-methyl-1H-pyrazoles (2a–l) were prepared according to the
literature procedures [27]. The general route for the synthesis of 2-
arylhydrazono-3-ketiminobutyronitriles and 5-amino-4-arylazo-3-meth-
yl-1H-pyrazoles is outlined in Scheme 1.
2.3.3. 5-[3′-Methyl–4′-(p-chlorophenylazo)-1′H-pyrazole-5′-ylazo]-3-
cyano-6-hydroxy-4-methyl-2-pyridone (3c)
121
122
Red crystals; yield 79%; mp. 320–321 °C (DMF–H2O); IR (KBr): ν 123
(cm−1) = 3262–3188 (3 NH), 3058 (Ar-H), 2981 (Al-H), 2225 (CN), 124
1695, 1676 (2 C_O); 1H NMR (DMSO-d6): δ = 2.75 (s, 3H, 3-CH3 125
pyrazole), 2.92 (s, 3H, 4-CH3 pyridone), 7.54 (d, 2H, J = 8.4, ArH), 126
7.77 (d, 2H, J = 8.4, ArH), 12.15 (br, 1H, pyridone NH), 13.42 (br, 1H, 127
pyrazole NH), 15.13 (br, 1H, OH or tautomeric hydrazo NH); Anal. 128
Calcd. for C17H13ClN8O2: C: 51.46, H: 3.30, N: 28.24. Found: C: 51.26, 129
85
2.3. Synthesis of pyridone-based disperse disazo dyes (3a–l)
86
87
88
89
90
91
92
93
94
95
96
97
98
99
5-Amino-4-arylazo-3-methyl-1H-pyrazoles (0.01 mol) were dis-
solved in a mixture of glacial acetic acid and concentrated hydrochloric
acid (20 ml, ratio 1:1) and the solution was then cooled to 0–5 °C. Sodi-
um nitrite (0.69 g, 0.01 mol) in water (10 ml) was then added to this
solution dropwise with vigorous stirring, about 1 h, while cooling at
0–5 °C. Then the resulting diazonium solution was added in portions
over 30 min to a vigorously stirred solution of 3-cyano-6-hydroxy-4-
methyl-2-pyridone (1.50 g, 0.01 mol) in KOH (0.56 g, 0.01 mol) and
water (10 ml) between 0 and 5 °C, maintaining the pH at 7–8 by simul-
taneous addition of sodium acetate solutions. The mixture was then
stirred for 2 h between 0 and 5 °C. The precipitated product was sepa-
rated upon dilution with water (50 ml) and then filtered off, washed
with water several times, dried and crystallized from DMF–H2O, respec-
tively. The general route for the synthesis of disazo dyes 3a–l is outlined
H: 3.37, N: 28.39.
130
2.3.4. 5-[3′-Methyl–4′-(p-methlyphenylazo)-1′H-pyrazole-5′-ylazo]-3-
cyano-6-hydroxy-4-methyl-2-pyridone (3d)
131
132
Orange crystals; yield 63%; mp. 228–229 °C (DMF–H2O); IR (KBr): ν 133
(cm−1) = 3246–3121 (3 NH), 3063 (Ar-H), 2993 (Al-H), 2222 (CN), 134
1689, 1670 (2 C_O); 1H NMR (DMSO-d6): δ = 2.41 (s, 3H, p-CH3), 135
2.74 (s, 3H, 3-CH3 pyrazole), 2.89 (s, 3H, 4-CH3 pyridone), 7.39 (d, 2H, 136
J = 7.9, ArH), 7.77 (d, 2H, J = 8.0, ArH), 12.12 (br, 1H, pyridone NH), 137
13.43 (br, 1H, pyrazole NH), 15.12 (br, 1H, OH or tautomeric hydrazo 138
NH); Anal. Calcd. for C18H16N8O2: C: 57.44, H: 4.28, N: 29.77. Found: 139
C: 57.62, H: 4.35, N: 29.56.
140
100 in Scheme 1.
2.3.5. 5-[3′-Methyl–4′-(m-nitrophenylazo)-1′H-pyrazole-5′-ylazo]-3-
cyano-6-hydroxy-4-methyl-2-pyridone (3e)
141
142
101 2.3.1. 5-[3′-Methyl–4′-(p-nitrophenylazo)-1′H-pyrazole-5′-ylazo]-3-
102 cyano-6-hydroxy-4-methyl-2-pyridone (3a)
Orange crystals; yield 81%; mp. 324–325 °C (DMF–H2O); IR (KBr): ν 143
(cm−1) = 3226–3136 (3 NH), 3083 (Ar-H), 2954 (Al-H), 2227 (CN), 144
1677, 1660 (2 C_O); 1H NMR (DMSO-d6): δ = 2.74 (s, 3H, 3-CH3 145
pyrazole), 2.89 (s, 3H, 4-CH3 pyridone), 7.86–8.64 (m, 4H, ArH), 12.20 146
(br, 1H, pyridone NH), 13.55 (br, 1H, pyrazole NH), 15.18 (br, 1H, OH 147
or tautomeric hydrazo NH); Anal. Calcd. for C17H13N9O4: C: 50.13, 148
103
Orange crystals; yield 84%; mp. 333–334 °C (DMF–H2O); IR (KBr): ν
104 (cm−1) = 3234–3133 (3 NH), 3069 (Ar-H), 2998 (Al-H), 2225 (CN),
105 1681, 1668 (2 C_O); 1H NMR (DMSO-d6): δ = 2.74 (s, 3H, 3-CH3
106 pyrazole), 2.90 (s, 3H, 4-CH3 pyridone), 7.60 (d, 2H, J = 9.2, ArH),
107 8.13 (d, 2H, J = 9.3, ArH), 12.10 (br, 1H, pyridone NH), 13.25 (br, 1H,
108 pyrazole NH), 15.14 (br, 1H, OH or tautomeric hydrazo NH); Anal.
109 Calcd. for C17H13N9O4: C: 50.13, H: 3.22, N: 30.95. Found: C: 50.28,
110 H: 3.25, N: 30.74.
H: 3.22, N: 30.95. Found: C: 50.31, H: 3.28, N: 31.12.
149
2.3.6. 5-[3′-Methyl–4′-(m-methoxyphenylazo)-1′H-pyrazole-5′-ylazo]-3- 150
cyano-6-hydroxy-4-methyl-2-pyridone (3f) 151
111 2.3.2. 5-[3′-Methyl–4′-(p-methoxyphenylazo)-1′H-pyrazole-5′-ylazo]-3-
112 cyano-6-hydroxy-4-methyl-2-pyridone (3b)
Red crystals; yield 69%; mp. 307–308 °C (DMF–H2O); IR (KBr): ν 152
(cm−1) = 3225–3145 (3 NH), 3021 (Ar-H), 2961 (Al-H), 2231 (CN), 153
1677, 1661 (2 C_O); 1H NMR (DMSO-d6): δ = 2.74 (s, 3H, 3-CH3 154
pyrazole), 2.90 (s, 3H, 4-CH3 pyridone), 3.86 (s, 3H, m-OCH3), 7.00– 155
7.98 (m, 4H, ArH), 12.10 (br, 1H, pyridone NH), 13.34 (br, 1H, pyrazole 156
NH), 15.20 (br, 1H, OH or tautomeric hydrazo NH); Anal. Calcd. for 157
113
Brown crystals; yield 72%; mp. 274–275 °C (DMF–H2O); IR (KBr): ν
114 (cm−1) = 3238–3130 (3 NH), 3050 (Ar-H), 2997 (Al-H), 2223 (CN),
115 1680, 1666 (2 C_O); 1H NMR (DMSO-d6): δ = 2.74 (s, 3H, 3-CH3
116 pyrazole), 2.90 (s, 3H, 4-CH3 pyridone), 3.86 (s, 3H, p-OCH3), 7.12
117 (d, 2H, J = 8.5, ArH), 7.83 (d, 2H, J = 8.3, ArH), 12.05 (br, 1H, pyridone
Q2
Scheme 1.
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
3
158 C18H16N8O3: C: 55.10, H: 4.11, N: 28.56. Found: C: 55.19, H: 4.15, N:
159 28.77.
C18H16N8O3: C: 55.10, H: 4.11, N: 28.56. Found: C: 55.22, H: 4.07, 196
N: 28.80.
197
2.3.11. 5-[3′-Methyl–4′-(o-chlorophenylazo)-1′H-pyrazole-5′-ylazo]-
3-cyano-6-hydroxy-4-methyl-2-pyridone (3k)
198
199
160 2.3.7. 5-[3′-Methyl–4′-(m-chlorophenylazo)-1′H-pyrazole-5′-ylazo]-3-
161 cyano-6-hydroxy-4-methyl-2-pyridone (3g)
Dark red crystals; yield 68%; mp. 279–280 °C (DMF–H2O); IR (KBr): 200
ν (cm−1) = 3220–3118 (3 NH), 3038 (Ar-H), 2958 (Al-H), 2238 (CN), 201
1696, 1676 (2 C_O); 1H NMR (DMSO-d6): δ = 2.74 (s, 3H, 3-CH3 202
pyrazole), 2.90 (s, 3H, 4-CH3 pyridone), 7.27–7.96 (m, 4H, ArH), 12.05 203
(br, 1H, pyridone NH), 13.38 (br, 1H, pyrazole NH), 14.88 (br, 1H, OH 204
or tautomeric hydrazo NH); Anal. Calcd. for C17H13ClN8O2: C: 51.46, 205
162
Red crystals; yield 73%; mp. 326–327 °C (DMF–H2O); IR (KBr): ν
163 (cm−1) = 3241–3133 (3 NH), 3052 (Ar-H), 2983 (Al-H), 2227 (CN),
164 1675, 1663 (2 C_O); 1H NMR (DMSO-d6): δ = 2.73 (s, 3H, 3-CH3
165 pyrazole), 2.91 (s, 3H, 4-CH3 pyridone), 7.00–8.01 (m, 4H, ArH), 12.14
166 (br, 1H, pyridone NH), 13.45 (br, 1H, pyrazole NH), 15.18 (br, 1H, OH
167 or tautomeric hydrazo NH); Anal. Calcd. for C17H13ClN8O2: C: 51.46,
168 H: 3.30, N: 28.24. Found: C: 51.59, H: 3.27, N: 28.35.
H: 3.30, N: 28.24. Found: C: 51.64, H: 3.34, N: 28.37.
206
2.3.12. 5-[3′-Methyl–4′-(o-methylphenylazo)-1′H-pyrazole-5′-ylazo]-
3-cyano-6-hydroxy-4-methyl-2-pyridone (3l)
207
208
169 2.3.8. 5-[3′-Methyl–4′-(m-methylphenylazo)-1′H-pyrazole-5′-ylazo]-
170 3-cyano-6-hydroxy-4-methyl-2-pyridone (3h)
Red crystals; yield 59%; mp. 289–290 °C (DMF–H2O); IR (KBr): ν 209
(cm−1) = 3222–3117 (3 NH), 3037 (Ar-H), 2963 (Al-H), 2238 (CN), 210
1697, 1662 (2 C_O); 1H NMR (DMSO-d6): δ = 2.43 (s, 3H, o-CH3), 211
2.73 (s, 3H, 3-CH3 pyrazole), 2.89 (s, 3H, 4-CH3 pyridone), 7.26–7.97 212
(m, 4H, ArH), 12.00 (br, 1H, pyridone NH), 13.48 (br, 1H, pyrazole 213
171
Red crystals; yield 61%; mp. 314–315 °C (DMF–H2O); IR (KBr): ν
172 (cm−1) = 3224–3138 (3 NH), 3066 (Ar-H), 2946 (Al-H), 2229 (CN),
173 1670, 1668 (2 C_O); 1H NMR (DMSO-d6): δ = 2.42 (s, 3H, m-CH3),
174 2.74 (s, 3H, 3-CH3 pyrazole), 2.91 (s, 3H, 4-CH3 pyridone), 7.30–7.99
175 (m, 4H, ArH), 12.10 (br, 1H, pyridone NH), 13.38 (br, 1H, pyrazole
176 NH), 15.20 (br, 1H, OH or tautomeric hydrazo NH); Anal. Calcd. for
177 C18H16N8O2: C: 57.44, H: 4.28, N: 29.77. Found: C: 57.32, H: 4.37,
178 N: 29.63.
NH), 14.82 (br, 1H, OH or tautomeric hydrazo NH); Anal. Calcd. for 214
OOF
C18H16N8O2: C: 57.44, H: 4.28, N: 29.77. Found: C: 57.60, H: 4.30, 215
N: 29.91.
216
2.4. Antimicrobial activities of pyridone-based disperse disazo dyes (3a–l) 217
179 2.3.9. 5-[3′-Methyl–4′-(o-nitrophenylazo)-1′H-pyrazole-5′-ylazo]-3-
180 cyano-6-hydroxy-4-methyl-2-pyridone (3i)
In vitro antimicrobial activities of the newly synthesized disperse 218
disazo dyes compounds were tested using the microbroth dilution meth- 219
od [32] against a panel of pathogenic and non-pathogenic microorgan- 220
isms. The panel consisted of Escherichia coli ATTC 25922, Pseudomonas 221
aeruginosa ATCC 254992, Salmonella typhimurium NRRL B-4420, 222
Staphylococcus aureus NRRL B-767, Bacillus subtilis NRS-744, Streptococcus 223
faecalis NRRL B-14617, Saccharomyces cerevisiae NRRL Y-12632, and 224
Candida utilis NRRL Y-900. Stock solutions of synthesized compounds 225
were sterilized by filtration through 0.45 μm Millipore filters and dilut- 226
ed. A 100 μl from dilutions was transferred to wells of 96-well micro- 227
titer plates. Thus, dilution series were prepared ranging from 1 to 228
181
Red crystals; yield 78%; mp. 285–286 °C (DMF–H2O); IR (KBr): ν
182 (cm−1) = 3228–3127 (3 NH), 3047 (Ar-H), 2922 (Al-H), 2227 (CN),
183 1681, 1670 (2 C_O); 1H NMR (DMSO-d6): δ = 2.75 (s, 3H, 3-CH3
184 pyrazole), 2.92 (s, 3H, 4-CH3 pyridone), 7.65–8.07 (m, 4H, ArH), 12.05
185 (br, 1H, pyridone NH), 13.52 (br, 1H, pyrazole NH), 14.93 (br, 1H, OH
186 or tautomeric hydrazo NH); Anal. Calcd. for C17H13N9O4: C: 50.13,
187 H: 3.22, N: 30.95. Found: C: 50.29, H: 3.14, N: 30.81.
188 2.3.10. 5-[3′-Methyl–4′-(o-methoxyphenylazo)-1′H-pyrazole-5′-ylazo]-3-
189 cyano-6-hydroxy-4-methyl-2-pyridone (3j)
190
Brown crystals; yield 71%; mp. 301-302 °C (DMF–H2O); IR (KBr): ν
0.0009 mg/ml in microtiter plates.
229
191 (cm−1) = 3249–3139 (3 NH), 3017 (Ar-H), 2947 (Al-H), 2229 (CN),
192 1686, 1671 (2 C_O); 1H NMR (DMSO-d6): δ = 2.73 (s, 3H, 3-CH3
193 pyrazole), 2.89 (s, 3H, 4-CH3 pyridone), 3.94 (s, 3H, o-OCH3), 6.96–
194 7.52 (m, 4H, ArH), 11.94 (br, 1H, pyridone NH), 13.22 (br, 1H, pyrazole
195 NH), 14.75 (br, 1H, OH or tautomeric hydrazo NH); Anal. Calcd. for
Microorganism cultures prepared from overnight grown microbial 230
suspensions were used as inoculants. These suspensions were standard- 231
ized to 108 CFU/ml using McFarland No: 0.5 standard solutions. A 100 μl 232
from these microorganism suspensions was used as inoculants for each 233
well. The well containing media, sterile distilled water, and inoculum 234
UNCORRECTED PR
Q3
Scheme 2.
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

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F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
t1:1
t1:2
Table 1
Also, FT-IR spectra of dyes 3a–l did not show any broad band for hy- 255
Influence of solvent on λmax (nm) of dyes 3a–l.
droxyl group. These suggest that dyes 3a–l are predominantly in azo- 256
hydrazo-keto form (T2) or dishydrazo-keto form (T4) as opposed to 257
disazo-enol form (T1) and hydrazo-azo-enol form (T3), in the solid 258
state (Scheme 2). Numerous investigations were carried out to establish 259
the tautomeric structure of azo pyridone in the solid state using a vari- 260
ety of spectroscopic techniques. The spectral data generally lead to the 261
conclusion that the tautomeric equilibrium of the azo pyridone dyes is 262
in favor of the hydrazone form in the solid state [30,31,33]. The other 263
νmax values of 3083–3017 cm−1 (aromatic C\H), 2998–2922 cm−1 264
t1:3
Dye no DMSO DMF
Acetonitrile Methanol Acetic acid Chloroform
t1:4
3a
3b
3c
3d
3e
3f
3g
3h
3i
474
474
468
467
486
468
467
465
480
468
461
472
476
474
464
450
468
451
456
459
454
458
454
453
453
451
445
434
465
453
458
459
454
454
454
454
451
454
444
430
468
450
452
459
451
463
459
458
456
456
448
436
t1:5
t1:6
470, 524 s 454
467, 510 s 457
488, 514 s 450
469, 512 s 456
468, 520 s 454
466, 516 s 454
482, 530 s 451
470, 512 s 454
465, 508 s 444
473, 520 s 439
t1:7
t1:8
t1:9
t1:10
t1:11
t1:12
t1:13
t1:14
t1:15
(aliphatic C\H) and 2238–2222 cm−1 (C`N) were recorded.
265
1H NMR spectra of dyes 3a–l showed three broad peaks at 11.94– 266
12.20 ppm (br, 1H, pyridone NH), 13.22–13.55 ppm (br, 1H, pyrazole 267
NH or tautomeric hydrazo NH) and 14.75–15.20 ppm (br, 1H, OH 268
or tautomeric hydrazo NH). These results suggest that dyes 3a–l are 269
present in a single tautomeric form in DMSO. The other 1H NMR values 270
of 6.96–8.64 ppm (ArH), 2.89–2.92 ppm (3-CH3 pyrazole) and 2.73– 271
3j
3k
3l
t1:16 Abbreviation: s, shoulder.
235 served as a positive growth control. The well that does not contain any
236 microorganisms was also used as the control. After incubation at 37 °C
237 for 18–24 h, tetrazolium salts were applied to plates in order to examine
238 microbial growth. The minimal inhibitory concentration (MIC) values
239 were defined as the lowest compound concentration where the absence
240 of growth was recorded. To determine bactericidal or fungicidal activity,
241 a 10 μl aliquot from each well was transferred to the fresh solid media
242 that do not contain any synthesized compounds. Chloramphenicol and
243 ketoconazole were used as reference antibiotics for bacteria and yeasts,
244 respectively. All of the antimicrobial activity studies were performed in
245 triplicate.
2.75 ppm (4-CH3 pyridone) were recorded.
272
3.2. Solvent effects on UV–vis spectra
273
As the tautomeric equilibria strongly depend on the nature of the 274
media, the behavior of dyes in various solvents was studied. For this 275
purpose, the UV–vis absorption spectra of dyes 3a–l were recorded 276
over the range of λ between 350 and 700 nm, using a variety of solvents 277
in concentrations (10−6–10−8 M). Because of solubility problems, 278
these were run at different concentrations and these results are summa- 279
rized in Table 1. The visible absorption spectra of the dyes did not corre- 280
246 3. Results and discussion
late with the polarity of solvent.
281
247 3.1. Spectral characteristics and tautomerism
Dyes 3a and 3b gave a maximum absorption peak in all used sol- 282
vents. This result suggests that dyes 3a and 3b are present in a single 283
tautomeric form in all used solvents. Dyes 3c–l gave a maximum 284
absorption peak with a shoulder in DMF. In the other solvents (DMSO, 285
acetonitrile, methanol, acetic acid and chloroform), dyes 3c–l gave a 286
maximum absorption peak. These results suggest that dyes 3c–l are 287
present in the mixture of a tautomeric form and an anionic form in 288
DMF and are present in a single tautomeric form in the other solvents 289
248
Pyridone-based disperse disazo dyes 3a–l can exist in four possible
249 tautomeric forms, namely the disazo-enol form (T1), the azo-hydrazo-
250 keto form (T2), the hydrazo-azo-keto form (T3) and the dishydrazo-
251 keto form (T4) as shown in Scheme 2. The deprotonation of tautomeric
252 forms of 3a–l leads to a common anion A.
253 The FT-IR spectra of dyes 3a–l showed three imino bands (NH) at
254 3262–3117 cm−1 and two carbonyl (C_O) bands at 1697–1660 cm−1
.
(DMSO, acetonitrile, methanol, acetic acid and chloroform).
290
2.000
1.500
1.000
0.500
0.000
1: DMSO
2: DMF
3: Acetonitrile
4: Methanol
5: Acetic acid
6: Chloroform
3
4
2
6
5
1
350
400
450
500
550
600
650
700
Wavelength (nm)
Fig. 1. Absorption spectra of dye 3i in various solvents.
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
5
t2:1
t2:2
Table 2
Absorption maxima of dyes 3a–l in acidic and basic solutions.
t2:3
t2:4
Dye no.
λmax (nm)
Methanol
Methanol + KOH
Methanol + HCl
Chloroform
Chloroform + piperidine
Acetic acid
t2:5
3a
3b
3c
3d
3e
3f
3g
3h
3i
468
451
456
459
454
458
454
453
453
451
445
434
497
492
502
496
512
500
504
493
508
499
492
498
463
451
451
451
453
452
450
449
447
452
442
429
468
450
452
459
451
463
459
458
456
456
448
436
479
451
465
470
470
473
470
469
487, 525 s
470, 502 s
468, 502 s
470, 517 s
465
453
458
459
454
454
454
454
451
454
444
430
t2:6
t2:7
t2:8
t2:9
t2:10
t2:11
t2:12
t2:13
t2:14
t2:15
t2:16
3j
3k
3l
t2:17 Abbreviation: s, shoulder.
291
292 bathochromically with respect to the λmax in chloroform (e.g. for dye 3i
293
max is 456 nm in chloroform, 480 nm in DMSO, 482 nm and 530 nm
It was observed that the λmax of dyes 3a–l in DMSO and DMF shifted
of dyes 3a–l were assigned to a common anionic form (A) in strong basic 311
medium (Scheme 2). 312
λ
When hydrochloric acid (0.1 M) was added to dye solutions in 313
294 (shoulder) in DMF) (Fig. 1). On the other hand, λmax values of dyes
295 3a–l in acetonitrile, methanol and acetic acid did not change signifi-
296 cantly with respect to the λmax in chloroform. It was also observed
297 that absorption ability of these disazo dyes substituted with electron-
298 withdrawing and electron-donating groups at their o, m- and p-
299 position is similar except for dyes 3e and 3i. λmax values of m-nitro
300 and o-nitro derivatives (3e and 3i) shifted bathochromically with re-
301 spect to the λmax of the other substituents in DMSO and DMF.
methanol, λmax of dyes 3a–l did not change significantly with respect 314
to the λmax in methanol (e.g. for dye 3i λmax is 453 nm in methanol, 315
447 nm in methanol + HCl) (Fig. 2). This indicates that dyes 3a–l do 316
OOF
not exist in a dissociated state in methanol + HCl.
317
When piperidine was added to dye solutions in chloroform, λmax of 318
dyes 3a–h showed bathochromic shifts and absorption curves of the 319
dyes resembled those in DMSO. When piperidine was added to dye so- 320
lutions in chloroform, λmax of dyes 3i–l showed bathochromic shifts and 321
absorption curves of the dyes resembled those in DMF (e.g. for dye 3i 322
λmax is 456 nm in chloroform, 487 nm and 525 nm (shoulder) in 323
chloroform + piperidine) (Fig. 3). These results suggest that dyes 3a– 324
h are present in a single tautomeric form in chloroform + piperidine 325
and dyes 3i–l are present in the mixture of a tautomeric form and an an- 326
302 3.3. Acid and base effects on UV–vis spectra
303
The effects of acid and base on the absorption of dye solutions
304 were investigated and the results are shown in Table 2. The absorption
305 spectra of the dyes 3a–l in methanol was quite sensitive to the addition
306 of base (potassium hydroxide, 0.1 M), with λmax of dyes 3a–l showing
307 large bathochromic shifts and absorption curves of dyes 3c–l resembled
308 their shoulders in DMF (e.g. for dye 3i λmax is 453 nm in methanol,
309 508 nm in methanol + KOH) (Fig. 2). This indicates that dyes 3a–l
310 exist in a dissociated state in methanol + KOH. Therefore, the structures
ionic form in chloroform + piperidine.
327
3.4. Antimicrobial activities
328
Although, antimicrobial activities of monoazo dyes were reported by 329
several authors [34–39], research on disazo dyes can be accepted as 330
2.000
1.500
1: Methanol
2: Methanol + KOH
3: Methanol + HCl
1.000
1
UNCORRECTED PR
0.500
3
2
0.000
350
400
450
500
550
600
650
700
Wavelength (nm)
Fig. 2. Absorption spectra of dye 3i in acidic and basic solutions.
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

6
F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
2.000
1.500
1.000
0.500
0.000
1: Chloroform
2: Chloroform + piperidine
3: Acetic acid
1
3
2
350
400
450
500
550
600
650
700
Wavelength (nm)
Fig. 3. Absorption spectra of dye 3i in acidic and basic solutions.
331 relatively new [40,41]. In the present study, the synthesized disperse
332 disazo dyes 3a–l were in vitro tested against Gram-positive and nega-
333 tive bacteria and the yeast by using the twofold serial dilution tech-
334 nique. The data presented in Table 3 indicate that the dyes are able to
335 inhibit in vitro growth of the tested microorganisms showing MIC be-
336 tween 125 and 1000 μg/ml except 4k derivative, which was determined
337 active at a MIC 62.5 μg/ml against S. faecalis.
antimicrobial activities against P. aeruginosa, exhibiting one dilution 348
step lower potency than the compared control drug, chloramphenicol. 349
On the other hand, dyes 3j and 3k showed significant activities against 350
S. faecalis, 125 and 62.5 μg/ml MIC concentrations, respectively. There- 351
fore, these dyes may have a potential for nosocomial infections.
352
It appears that all of the synthesized dyes have static activities 353
against the used test microorganisms other than C. utilis. The com- 354
pounds 3a, 3c, 3e, 3f, 3j, and 3k showed fungicidal activity for C. utilis 355
at a MIC 125 μg/ml which is equal to the value of ketoconazole (Table 3). 356
338
It can be seen from Table 3 that most of the synthesized disperse
339 disazo dyes exhibited lower MIC values than the used positive control
340 drugs with the exception of dyes 3d and 3g. These dyes have presented
341 only weak antimicrobial activities generally. On the other hand, dye 3c
342 was the most active compound which exhibited lower MIC values
343 against 6 of the all test microorganisms. Because of the presence in nos-
344 ocomial infections and resistance to antibiotic therapy, P. aeruginosa and
345 S. faecalis can be accepted as significant pathogens. Therefore, inhibition
346 of these microorganisms is very important for treatment of secondary
347 infections. Dyes 3a, 3c, 3f, 3j, and 3k were presented significant
4. Conclusions
357
A series of twelve novel pyridone-based disperse disazo dyes was 358
synthesized by coupling diazonium salts of 5-amino-3-methyl-4- 359
arylazo-1H-pyrazoles with 3-cyano-6-hydroxy-4-methyl-2-pyridone. 360
These dyes were characterized by FT-IR, 1H NMR and elemental analy- 361
sis. Solvent and acid–base influences on the wavelength of maximum 362
t3:1
t3:2
t3:3
Table 3
Minimal inhibitory concentrations (MIC), minimum bactericidal concentration (MBC) and minimum fungicidal concentrations (MFC) of dyes 3a–l and reference antibiotics against test
microorganisms.
t3:4
t3:5
MIC (MBC or MFC) μg/ml
Dye no.
Aa
B
C
D
E
F
G
H
t3:6
3a
3b
3c
3d
3e
3f
3g
3h
250 (1000)
250 (1000)
500 (1000)
250 (1000)
500 (N1000)
250 (N1000)
250 (N1000)
1000 (N1000)
1000 (N1000)
1000 (1000)
1000 (N1000)
1000 (N1000)
1000 (1000)
1000 (1000)
1000 (1000)
1000 (N1000)
N1000 (N1000)
1000 (N1000)
1000 (N1000)
1000 (N1000)
250 (N1000)
125 (125)
t3:7
500 (1000)
250 (N1000)
1000 (1000)
500 (1000)
1000 (1000)
1000 (1000)
500 (1000)
500 (1000)
500 (1000)
250 (1000)
1000 (1000)
1000 (1000)
500 (1000)
250 (1000)
1000 (1000)
500 (1000)
250 (1000)
1000 (1000)
500 (1000)
500 (1000)
250 (1000)
250 (1000)
500 (1000)
500 (1000)
500 (1000)
250 (1000)
1000 (1000)
250 (N1000)
250 (1000)
1000 (1000)
500 (1000)
500 (1000)
500 (1000)
500 (1000)
500 (1000)
500 (1000)
250 (1000)
250 (1000)
1000 (N1000)
250 (1000)
500 (1000)
1000 (1000)
500 (1000)
250 (1000)
500 (1000)
250 (1000)
500 (1000)
1000 (1000)
250 (N1000)
250 (N1000)
1000 (N1000)
250 (N1000)
250 (N1000)
1000 (N1000)
250 (N1000)
250 (N1000)
250 (N1000)
125 (N1000)
500 (N1000)
1000 (N1000)
250 (250)
125 (125)
500 (500)
125 (125)
125 (125)
1000 (1000)
500 (500)
500 (500)
125 (125)
125 (125)
125 (250)
125 (125)
t3:8
t3:9
1000 (N1000)
500 (N1000)
500 (N1000)
1000 (N1000)
500 (N1000)
250 (N1000)
125 (N1000)
62.5 (N1000)
500 (N1000)
1000 (N1000)
t3:10
t3:11
t3:12
t3:13
t3:14
t3:15
t3:16
t3:17
t3:18
3i
3j
3k
3l
Referenceb
a
A: Escherichia coli ATCC 25922, B: Pseudomonas aeruginosa ATCC 254992, C: Salmonella typhimurium NRRL B-4420, D: Staphylococcus aureus NRRL B-767, F: Bacillus subtilis NRS-744,
t3:19 E: Streptococcus faecalis NRRL B-14617, G: Saccharomyces cerevisiae NRRL Y-12632, H: Candida utilis, NRRL Y-900.
b
t3:20
Reference for A–E: Chloramphenicol and for G, H: Ketoconazole.
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005

F. Karcı et al. / Journal of Molecular Liquids xxx (2013) xxx–xxx
7
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As a consequence for antimicrobial activity studies, we can argue that
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UNCORRECTED PR
Please cite this article as: F. Karcı, et al., J. Mol. Liq. (2013), http://dx.doi.org/10.1016/j.molliq.2013.08.005