- Email: [email protected]
New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures
MOLLIQ-04684; No of Pages 7 Journal of Molecular Liquids xxx (2015) xxx–xxx
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
3Q2
Fikret Karcı a,⁎, Emine Bakan b a
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a r t i c l e
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Article history: Received 28 January 2015 Received in revised form 23 February 2015 Accepted 24 February 2015 Available online xxxx
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Keywords: Disperse dyes Disazo dyes Pyrazole dyes Absorption ability Solvatochromism Tautomeric structure
i n f o
R O
Pamukkale University, Faculty of Science–Arts, Department of Chemistry, Denizli, Turkey Uşak University, Higher Vocational School of Ulubey, Fashion Design Programme, Ulubey, Uşak, Turkey
a b s t r a c t
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1. Introduction
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Simple nitrogen-containing heterocycles receive significant attention in the literature due to their exciting biological properties as well as their historical important role as pharmacophores. The synthesis, reactions and biological activities of pyrazole containing molecules, of these heterocycles, lead to an ever-expanding research area in heterocyclic chemistry and moreover; these structures appear in a large number of pharmaceutical agents and natural products. Fused pyrazoles with many different derivatives may exhibit a wide range of interesting properties such as antihyperglycemic, analgestic, anti-inflammatory, antipyretic, anti-bacterial, hypoglycaemic and sedative-hypnotic activities. Recently, some pyrazoles were reported to display nonnucleoside HIV1 reverse transcriptase inhibitory activity [1–6]. Some azopyrazole derivatives also find applications in dyes, biological and pharmacological studies and complexes [7–12]. The condensation of β-enaminonitriles and β-ketoesters with hydrazines continues to be the most widely used method for aminopyrazole and pyrazolone formation, respectively [13–16]. The amino derivatives of pyrazoles belong to important compounds used for the preparation of other functional derivatives mainly for the synthesis of condensed heterocyclic systems [17–19]. The use of heterocyclic intermediates in the synthesis of azo disperse dyes is well established and the resultant dyes exhibit good tinctorial strength and brighter appearance than those derived from aniline-
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
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5-amino-4-arylazo-3-methyl-1-phenylpyrazoles (2a–k) were diazotised and coupled with 5-hydroxy-3-methyl1H-pyrazole and 5-hydroxy-3-methyl-1-phenylpyrazole to generate two series disazo pyrazole disperse dyes (3a–k and 4a–k). These novel synthesized disazo pyrazole disperse dyes were characterized by elemental analysis and spectral methods. Absorption ability and tautomeric structure of synthesized disazo pyrazole disperse dyes substituted with electron-withdrawing and electron-donating groups at their o, m- and p-positions were also examined in detail. © 2015 Published by Elsevier B.V.
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New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures
1Q1
⁎ Corresponding author. E-mail address: [email protected] (F. Karcı).
based diazo components. For instance, amino-substituted thiazole, benzothiazole [20–23] and benzoisothiazole [24] compounds afford highly electronegative diazo components and consequently, provide a pronounced bathochromic effect compared to the corresponding benzoid compounds. Moreover, azo disperse dyes containing 5hydroxy-3-methyl-1H-pyrazole as coupling component were reported to be in red–violet colours in the literature [25,26]. We have previously reported the synthesis of some disazo disperse dyes [27–32]. In this study, we report the synthesis of two different series of new disazo disperse dyes based on two pyrazole rings in one dye structure. The absorption ability of these dyes substituted with electron-withdrawing and electron-donating groups at their o, m- and p-positions was also examined in detail.
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2. Experimental
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2.1. General
67
The chemicals, used for the synthesis of the compounds, were obtained from Aldrich and Merck without further purification. The solvents used were of spectroscopic grade. IR spectra were determined via Mattson 1000 Fourier Transforminfrared (FT-IR) spectrophotometer using a KBr disc. Nuclear magnetic resonance (1H NMR) spectra were recorded on a Bruker-Spectrospin Avance DPX 400 Ultra-Shield in deuterated dimethylsulphoxide (DMSO-d6) using tetramethylsilane (TMS) as the internal reference and chemical shifts (δ) were given in ppm. Ultraviolet–visible (UV–
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http://dx.doi.org/10.1016/j.molliq.2015.02.032 0167-7322/© 2015 Published by Elsevier B.V.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
54 55 56 57 58 59 60 61 62 63 64 65
69 70 71 72 73 74 75 76
2
86 87
2.2. Synthesis of 2-arylhydrazono-3-ketiminobutyronitriles (1a–k) and 5amino-4-arylazo-3-methyl-1-phenylpyrazoles (2a–k)
91
2.3. Synthesis of disperse disazo pyrazole dyes (3a–k and 4a–k)
92
5-Amino-4-arylazo-3-methyl-1-phenylpyrazoles (0.01 mol) were dissolved 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. Sodium nitrite (0.69 g, 0.01 mol) in water (10 ml) was then added to this solution dropwise with vigorous stirring, for 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 5-hydroxy-3-methyl1H-pyrazole or 5-hydroxy-3-methyl-1-phenylpyrazole (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 simultaneous sodium acetate solution addition. The mixture was then stirred for 2 h at 0–5 °C. The precipitated product separated upon dilution with water (50 ml) was filtered off, washed with water several times, dried and crystallized from DMF–H2O.
105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
C
104
2.3.1. 4-(4′-(p-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)-5hydroxy-3-methyl-1H-pyrazole (3a) Red crystals; yield 74%; mp. 210–211 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3244 (NH), 3057 (Ar–H), 2923 (Al–H), 1663 (C_O), 1493 (N_N); 1H-NMR (DMSO-d6): δ = 2.23 (s, 3H, CH3), 2.72 (s, 3H, CH3), 6.84–8.42 (m, 9H, ArH), 9.97 (br, 1H, OH), 11.55 (br, 1H, NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.12, H: 3.85, N: 29.30.
E
102 103
R
100 101
R
98 99
O
96 97
2.3.2. 4-(4′-(p-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3b) Yellow crystals; yield 48 %; mp. dec. N 96 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3195 (NH), 3071 (Ar–H), 2923 (Al–H), 1649 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.76 (s, 3H, CH3), 3.84 (s, 3H, p-OCH3), 7.09–8.01 (m, 9H, ArH), 11.70 (br, OH), 13.37 (br, NH), 13.91 (br, hydrazo NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C21H20N8O2: C: 60.57, H: 4.84, N: 26.91. Found: C: 60.35, H: 4.89, N: 26.80.
C
94 95
N
93
U
88
130 131
2.3.5. 4-(4′-(m-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3e) Brown crystals; yield 68 %; mp. 131–132 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3107 (NH), 3036 (Ar–H), 2870 (Al–H), 1666 (C_O), 1525 (N_N); 1H-NMR (DMSO-d6): δ = 2.21 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.21–8.79 (m, 9H, ArH), 9.86 (br, OH), 11.32 (br, NH), 11.81 (br, hydrazo NH), 14.13 (br, hydrazo NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.79, H: 3.99, N: 29.33.
138
+
N2 Cl X
_
NC C
+ H
C CH3
N N H
128 129
132 133 134 135 136 137
139 140 141 142 143 144 145
2.3.7. 4-(4′-(m-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3g) Greenish black crystals; yield 35 %; mp. 104–105 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3170 (NH), 3064 (Ar–H), 2919 (Al–H), 1659 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.29 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.41 (s, 3H, m-CH3), 7.04–7.95 (m, 9H, ArH), 11.74 (br, OH), 13.26 (br, NH), 14.15 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 63.15, H: 5.12, N: 28.21.
154 155
2.3.8. 4-(4′-(o-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)-5hydroxy-3-methyl-1H-pyrazole (3h) Red crystals; yield 55 %; mp. 200–201 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3262 (NH), 3054 (Ar–H), 2926 (Al–H), 1670 (C_O), 1486 (N_N); 1H-NMR (DMSO-d6): δ = 2.25 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.29–8.22 (m, 9H, ArH), 10.12 (br, OH), 11.57 (br, NH), 13.98 (br, hydrazo NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.56, H: 4.03, N: 29.45.
162 163
C
X
NH
PhNHNH2 N
C CH3
(1a-k)
a, X : p-NO2 b, X : p-OCH3 c, X : p-Cl d, X : p-CH3
126 127
146
CN
NH2
124 125
2.3.6. 4-(4′-(m-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3f) Orange crystals; yield 70 %; mp. 114–115 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3061 (Ar–H), 2926 (Al–H), 1670 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.71 (s, 3H, CH3), 7.22–8.13 (m, 9H, ArH), 11.79 (br, NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 57.14, H: 3.89, N: 26.69.
T
89 90
2-Arylhydrazone-3-ketiminobutyronitriles (1a–k) and 5-amino-4arylazo-3-methyl-1-phenylpyrazoles (2a–k) were prepared according to the literature procedures [16,33,34]. The general route for the synthesis of 2-arylhydrazono-3-ketiminobutyronitriles and 5-amino-4arylazo-3-methyl-1-phenylpyrazoles is outlined in Scheme 1.
2.3.4. 4-(4′-(p-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3d) Orange crystals; yield 58 %; mp. 90–91 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3047 (Ar–H), 2916 (Al–H), 1666 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.28 (s, 3H, CH3), 2.67 (s, 3H, CH3), 2.38 (s, 3H, p-CH3), 7.16–8.03 (m, 9H, ArH), 11.71 (br, OH), 13.30 (br, NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 62.90, H: 4.90, N: 27.91.
F
85
O
84
R O
83
122 123
P
81 82
2.3.3. 4-(4′-(p-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3c) Yellow crystals; yield 65 %; mp. 120–121 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3064 (Ar–H), 2926 (Al–H), 1666 (C_O), 1529 (N_N); 1H-NMR (DMSO-d6): δ = 2.29 (s, 3H, CH3), 2.69 (s, 3H, CH3), 7.47–8.13 (m, 9H, ArH), 11.74 (br, NH), 14.18 (br, hydrazo NH); Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 56.95, H: 4.23, N: 26.55.
D
79 80
vis) absorption spectra were recorded via a Schimadzu UV-1601 double beam spectrophotometer at the wavelength of maximum absorption (λmax) in a range of different solvents, i.e. DMSO, DMF, acetonitrile, methanol, acetic acid and chloroform at various concentrations (1 × 10−6–10−8). Melting points were determined on an Electrothermal 9100 melting point apparatus and are uncorrected. Elemental analysis was carried out using a Leco CHNS-932 analyzer.
E
77 78
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
e, X : m-NO2 f, X : m-Cl g, X : m-CH3
N
X H3C
h, X : o-NO2 i, X : o-OCH3 j, X : o-Cl k, X : o-CH3
NH2 N N (2a-k)
Scheme 1. Synthesis of aminoarylazopyrazoles (2a–k).
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
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189 190 191 192 193
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2.3.18. 4-(4′-(m-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4g) Orange crystals; yield 35 %; mp. 230–231 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3131 (NH), 3054 (Ar–H), 2916 (Al–H), 1666 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.74 (s, 3H, CH3), 2.37 (s, 3H, m-CH3), 7.06–8.46 (m, 14H, ArH), 13.29 (br, NH), 14.34 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 68.11, H: 5.22, N: 23.70.
242
2.3.12. 4-(4′-(p-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1-phenylpyrazole (4a) Red crystals; yield 67 %; mp. 332–333 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3128 (NH), 3064 (Ar–H), 2926 (Al–H), 1666 (C_O), 1507 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.76 (s, 3H, CH3), 7.41–8.52 (m, 14H, ArH), 13.37 (br, NH), 14.30 (br, hydrazo NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.42, H: 4.02, N: 24.71.
2.3.19. 4-(4′-(o-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1-phenylpyrazole (4h) Red crystals; yield 78 %; mp. 150–151 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3262 (NH), 3057 (Ar–H), 2923 (Al–H), 1666 (C_O), 1486 (N_N); 1H-NMR (DMSO-d6): δ = 2.26 (s, 3H, CH3), 2.73 (s, 3H, CH3), 7.28–8.20 (m, 14H, ArH), 10.12 (br, OH), 11.57 (br, NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.65, H: 4.29, N: 24.97.
250
2.3.13. 4-(4′-(p-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4b) Brown crystals; yield 33 %; mp. dec. N 104 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3212 (NH), 3064 (Ar–H), 2965 (Al–H), 1666 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.28 (s, 3H, CH3), 2.73 (s, 3H, CH3), 3.78 (s, 3H, p-OCH3), 7.02–8.14 (m, 14H, ArH), 13.38 (br, NH), 14.20 (br, hydrazo NH);Anal. Calcd. for C27H24N8O2: C: 65.84, H: 4.91, N: 22.75. Found: C: 65.71, H: 4.98, N: 22.94.
2.3.20. 4-(4′-(o-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phneylpyrazole (4i) Brown crystals; yield 44 %; mp. dec. N 105 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3276 (NH), 3064 (Ar–H), 2934 (Al–H), 1670 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.32 (s, 3H, CH3), 2.73 (s, 3H, CH3), 3.97 (s, 3H, o-OCH3), 7.02–7.95 (m, 14H, ArH), 10.59 (br, OH), 13.73 (br, NH), 14.64 (br, hydrazo NH); Anal. Calcd. for C27H24N8O2: C: 65.84, H: 4.91, N: 22.75. Found: C: 65.91, H: 5.01, N: 22.63.
258 259
2.3.14. 4-(4′-(p-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4c) Orange crystals; yield 62 %; mp. 300–301 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3191 (NH), 3064 (Ar–H), 2926 (Al–H), 1659 (C_O), 1500 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.74 (s, 3H, CH3), 7.20–8.19 (m, 14H, ArH), 14.30 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.90, H: 4.33, N: 22.59.
2.3.21. 4-(4′-(o-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4j) Orange crystals; yield 90 %; mp. 175–176 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3142 (NH), 3061 (Ar–H), 2923 (Al–H), 1659 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.70 (s, 3H, CH3), 7.23–7.88 (m, 14H, ArH), 13.77 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.75, H: 4.30, N: 22.24.
266 267
2.3.15. 4-(4′-(p-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4d) Orange crystals; yield 60 %; mp. 259–260 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3191 (NH), 3025 (Ar–H), 2919 (Al–H), 1659 (C_O), 1504 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.39 (s, 3H, p-CH3), 7.20–8.09 (m, 14H, ArH), 12.20 (br, OH), 13.30 (br, NH), 14.21 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 68.14, H: 5.32, N: 23.65.
2.3.22. 4-(4′-(o-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4k) Orange crystals; yield 92 %; mp. 241–242 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3195 (NH), 3061 (Ar–H), 2923 (Al–H), 1666 (C_O), 1539 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.73 (s, 3H, CH3), 2.36 (s, 3H, o-CH3), 7.23–7.87 (m, 14H, ArH), 13.85 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 67.92, H: 4.87, N: 23.45.
274
O
F
2.3.11. 4-(4′-(o-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3k) Brown crystals; yield 32 %; mp. 180–181 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3149 (NH), 3064 (Ar–H), 2979 (Al–H), 1663 (C_O), 1500 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.36 (s, 3H, o-CH3), 7.30–7.93 (m, 9H, ArH), 11.65 (br, NH), 13.78 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 63.23, H: 4.95, N: 28.05.
R O
187 188
P
186
D
184 185
234 235
E
182 183
2.3.17. 4-(4′-(m-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4f) Orange crystals; yield 63 %; mp. 125–126 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3134 (NH), 3061 (Ar–H), 2926 (Al–H), 1670 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.31 (s, 3H, CH3), 2.73 (s, 3H, CH3), 7.51–7.81 (m, 14H, ArH), 14.34 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.88, H: 4.34, N: 22.63.
T
180 181
2.3.10. 4-(4′-(o-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3j) Brown crystals; yield 45 %; mp. 196–197 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3230 (NH), 3064 (Ar–H), 2923 (Al–H), 1677 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.31 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.41–7.70 (m, 9H, ArH), 11.61 (br, NH), 13.74 (br, hydrazo NH);Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 57.33, H: 4.19, N: 26.86.
C
178 179
E
177
R
176
226 227
R
174 175
2.3.16. 4-(4′-(m-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (4e) Brick red crystals; yield 58 %; mp. 134–135 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3248 (NH), 3075 (Ar–H), 2919 (Al–H), 1652 (C_O), 1522 (N_N); 1H-NMR (DMSO-d6): δ = 2.33 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.69–8.70 (m, 14H, ArH), 9.86 (br, OH), 11.34 (br, NH), 13.28 (br, hydrazo NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.20, H: 4.05, N: 25.03.
N C O
172 173
2.3.9. 4-(4′-(o-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3i) Brown crystals; yield 36 %; mp. 117–118 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3276 (NH), 3071 (Ar–H), 2941 (Al–H), 1663 (C_O), 1529 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 3.92 (s, 3H, o-OCH3), 7.04–7.92 (m, 9H, ArH), 10.59 (br, OH), 11.59 (br, NH), 14.64 (br, hydrazo NH); Anal. Calcd. for C21H20N8O2: C: 60.57, H: 4.84, N: 26.91. Found: C: 60.28, H: 4.87, N: 26.74.
U
170 171
3
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
228 229 230 231 232 233
236 237 238 239 240 241
243 244 245 246 247 248 249
251 252 253 254 255 256 257
260 261 262 263 264 265
268 269 270 271 272 273
275 276 277 278 279 280 281
4
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
HO
H N N
H N
HO
N
CH3 N
N
CH3
N N
X N
H3C N
N
N
NH2 N
H3C
N
(3a-k)
X
NaNO2/HCl
X
+ N2 Cl
N
N
_
N
H3C
CH3COOH
N
(2a-k) N
F
HO
N
N
O
X
H3C
N N
CH3
N N N
N (4a-k)
R O
HO
N
CH3
N
N
H N
O
N N X
N
E N
HO
N
N
N
N N
N
O
H
CH3
N N
disazo-enol
(T3)
N
- H+ +
H3C
azo-hydrazo-enol
U
N
N
X
C
N N
_
CH3
N N
X H3C
KT
HO
O
H N
(T2)
R
KT
N
N
azo-hydrazo-keto
R
(T1)
CH3
N N
H3C
N
disazo-enol
N
N
C
X H3C
N
H
KT
CH3
N N
H N
T
HO
E
D
P
Scheme 2. Synthesis of disperse disazo pyrazole dyes 3a–k and 4a–k.
H+
N
N N
H N N CH3
X H3C
N N
anionic form (A1)
(T4) KT
KT
O
N
N
N N
H N NH CH3
X H3C
N N
disazo-keto (T5)
Scheme 3. Tautomeric equilibriums of dyes 3a–k.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
HO
N
N
O
N
N N
N
N N
H
KT
CH3
5
N
N
N N
CH3
X
X N
H3C
N
H3C
N
N _ O
disazo-enol
azo-hydrazo-keto
(T6)
KT
(T7)
KT
N
- H+ +
N
N N
N N CH3
X
H+
N N
N
N
N
N N
H
CH3
X N
H3C
anionic form (A2)
R O
N
O
O
F
H3C
N
disazo-keto
P
(T8)
D
Scheme 4. Tautomeric equilibriums of dyes 4a–k.
3. Results and discussion
283
3.1. Spectral characteristics and tautomerism
284
300 301
Disazo pyrazole disperse dyes 3a–k can exist in five possible tautomeric forms, namely the disazo-enol forms T1 and T4, the azohydrazo-keto form T2, the azo-hydrazo-enol form T3 and the disazoketo form T5 as shown in Scheme 3. The FT-IR spectra of 3a–k dyes displayed imino (NH) bands at 3107–3276 cm− 1, carbonyl (C_O) bands at 1649–1677 cm−1 and diazo (N_N) bands at 1486– 1536 cm−1. The other νmax values of 3036–3071 cm−1 (aromatic C– H) and 2870–2979 cm−1 (aliphatic C–H) were also recorded. On the other hand, disazo disperse dyes 4a–k can exist in three possible tautomeric forms, namely the disazo-enol form T6, the azo-hydrazo-keto form T7 and the disazo-keto form T8 as shown in Scheme 4. The FT-IR spectra of 4a–k dyes exhibited imino (NH) bands at 3128–3276 cm−1, carbonyl (C_O) bands at 1652–1670 cm−1 and diazo (N_N) bands at 1486–1539 cm−1. The other νmax values of 3025–3075 cm−1 (aromatic C–H) and 2916–2965 cm−1 (aliphatic C–H) were also recorded. Also, FT-IR spectra of disazo pyrazole disperse dyes (3a–k and 4a–k) did not exhibit any broad bands for hydroxyl group. These suggest that disazo pyrazole disperse dyes 3a–k are predominantly in azo-
t1:1 t1:2
Table 1 Influence of solvent on λmax (nm) of dyes 3a–k.
292 293 294 295 296 297 298 299
T
C
E
R
291
R
289 290
N C O
287 288
U
285 286
hydrazo-keto form T2 or disazo-keto form T5 and 4a–k are predominantly in azo-hydrazo-keto form T7 or disazo-keto form T8 as opposed to the other tautomeric forms in the solid state (Schemes 3 and 4). (See Scheme 2.) 1 H NMR spectra of dyes 3a displayed one broad peak at 9.97 ppm (OH) and one broad peak at 11.55 ppm (NH). This result suggests that dye 3a is present as one of T1, T3 and T4 as opposed to the other tautomeric forms in DMSO-d6. 1H NMR spectra of 3b, 3d, 3e, 3g, 3h, 3i dyes exhibited one hydroxyl (OH) peak, one imino (NH) peak and hydrazo NH peaks. These results suggest that 3b, 3d, 3e, 3g, 3h, 3i dyes are in the mixture of tautomeric forms in DMSO-d6. 1H NMR spectra of 3c, 3f, 3j and 3k dyes showed one imino (NH) peak and hydrazo NH peaks. These results suggest that 3c, 3f, 3j and 3k dyes are present as one or mixture of T2 and T5 as opposed to the other tautomeric forms in DMSO-d6. 1 H NMR spectra of 4a–c, 4f, 4g, 4j and 4k dyes displayed only NH peaks and did not exhibit any broad peaks for hydroxyl (OH) groups. These results suggest that 4a–c, 4f, 4g, 4j and 4k dyes are present as one or mixture of T7 and T8 as opposed to the other tautomeric form T6 in DMSO-d6. On the other hand, 1H NMR spectra of 4d, 4e, 4h and 4i dyes both showed NH peaks and OH peaks. These results suggest that 4d, 4e, 4h and 4i dyes are in the mixture of tautomeric forms in DMSO-d6.
E
282
t1:3
Dye no.
DMSO
DMF
Acetonitrile
Methanol
Acetic acid
Chloroform
t1:4 t1:5 t1:6 t1:7 t1:8 t1:9 t1:10 t1:11 t1:12 t1:13 t1:14
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
452, 350 418, 304 420, 345 397, 346 386, 343 438, 343 391, 347 443, 387 386 422, 343 395, 340
444, 342, 586 416, 364 420, 343 402, 345 390, 340 424, 340 394, 345 443, 385 385 421, 342 406, 340
429, 336 411, 364 420, 341 394, 342 381, 340 438, 338 387, 341 434, 373 381 417, 341 399, 338
435, 340 413, 350 421, 339 398, 339 379, 340 413, 336 394, 337 385, 348 385 410, 341 392, 337
428, 334 415, 362 423, 339 401, 340 378, 337 400, 335 394, 339 409, 344 380 413, 337 406, 333
432, 341 416, 364 415, 343 402, 344 385, 341 399, 340 397, 345 440, 378 395 412, 341 409, 340
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
302 303 304 305 Q3 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
6
4a
t2:6 t2:7 t2:8 t2:9 t2:10 t2:11 t2:12 t2:13 t2:14 t2:15
4b 4c 4d 4e 4f 4g 4h 4i 4j 4k
451, 357, 590 420, 364 420, 345 422, 345 395, 340 420, 340 418, 343 431, 348 405, 363 409, 341 410, 338
Acetonitrile
440, 356, 584 418, 357 424, 344 423, 344 401, 340 425, 340 420, 341 426, 349 406, 361 411, 339 413, 337
Methanol
Acetic acid
Chloroform
428, 351
433, 353
427, 346
429, 354
411, 358 420, 341 411, 341 394, 338 414, 338 411, 339 421, 347 398, 359 403, 335 405, 334
414, 361 419, 337 398, 340 389, 337 412, 337 401, 337 410, 348 396, 361 421, 340 409, 333
416, 352 419, 339 409, 341 396, 335 411, 336 415, 336 412, 341 405, 358 408, 332 408, 332
419, 358 421, 343 416, 344 399, 339 415, 340 415, 341 425, 349 406, 361 401, 339 408, 338
3.2. Solvent effects on UV–vis spectra
325
340
The UV–vis absorption spectra of 3a–k and 4a–k dyes were recorded over the range of λ between 300 and 700 nm, using a variety of solvents in concentrations (10−6–10−8 M) and the results are summarised in Tables 1 and 2. The visible absorption spectra of the dyes did not correlate with the polarity of solvents. 3a–k and 4a–k dyes resulted in two maximum absorption peaks in all used solvents, except for 3i. These results suggest that 3a–k and 4a–k dyes are present in the mixture of tautomeric forms in all used solvents, except for 3i. Dye 3i is present in a single tautomeric form in all used solvents. It was observed that λmax of 3a–k and 4a–k dyes did not change significantly in all used solvents, except for 3a and 4a. It was also observed that new peaks at long wavelength besides other peaks in absorption spectra of 3a and 4a dyes in DMF and DMSO. These results suggest that 3a and 4a dyes are present in the mixture of tautomeric forms and an anionic form in DMF and DMSO.
341
3.3. Acid and base effects on UV–vis spectra
342 343
349 350
The effects of acid and base on the absorption of dye solutions were investigated and the results are shown in Tables 3 and 4. The absorption spectra of the 3a and 4a dyes in methanol was quite sensitive to alkali addition (potassium hydroxide, 0.1 M), with λmax of 3a and 4a dyes showing bathochromic shifts. Absorption curves of the dye 3a resembled those of DMF (Fig. 3) while absorption curves of the dye 4a were similar to those of DMF and DMSO (Fig. 4). The absorption spectra of the other dyes in methanol were not sensitive to alkali addition (potassium hydroxide, 0.1 M). These results suggest that 3a and 4a dyes are
t3:1 t3:2
Table 3 Absorption maxima of dyes 3a–k in acidic and basic solutions.
344 345 346
Chloroform Chloroform + piperidine
Acetic acid
4a
433, 353
430, 365
429, 354
421, 352
427, 346
t4:6
4b 4c 4d 4e 4f 4g 4h 4i 4j 4k
414, 361 419, 337 398, 340 389, 337 412, 337 401, 337 410, 348 396, 361 421, 340 409, 333
413, 360 416, 337 405, 340 389, 340 414, 337 401, 337 411, 342 400, 362 413, 333 408, 332
419, 358 421, 343 416, 344 399, 339 415, 340 415, 341 425, 349 406, 361 401, 339 408, 338
413, 351 421, 340 412, 331 399, 311 415, 302 412, 340 427, 340 407, 360 403, 340 414, 305
416, 352 419, 339 409, 341 396, 335 411, 336 415, 336 412, 341 405, 358 408, 332 408, 332
t4:7 t4:8 t4:9 t4:10 t4:11 t4:12 t4:13 t4:14 t4:15 t4:16
440, 369, 553 408, 363 418, 339 402, 339 423, 329 419, 336 403, 335 413, 345 401,360 433, 342 434, 336
present in the mixture of tautomeric forms and an anionic form in strong basic solutions. (See Figs. 1 and 2.) When hydrochloric acid (0.1 M) was added to dye solutions in methanol, λmax of 3a–k and 4a–k dyes did not change significantly and the absorption spectra of dyes were similar to those in acetic acid (Figs. 3 and 4). When piperidine was added to dye 3a solutions in chloroform, λmax of dye 3a exhibited bathochromic shift. This result suggests that dye 3a is present in the mixture of tautomeric forms and an anionic form in weak basic solutions. λmax of 3b–k and 4a–k dyes did not change significantly when a small amount of piperidine was added to 3b–k and 4a–k dyes solution in chloroform.
Dye no.
t3:4 t3:5 t3:6 t3:7 t3:8 t3:9 t3:10 t3:11 t3:12 t3:13 t3:14 t3:15
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
351 352 Q5 353 354 355 356 357 358 359 360 361 362 363
As seen in Tables 1 and 2, generally, electron-accepting nitro groups in p- and o-positions for dyes caused bathochromical shifts in all used solvents when compared with the other dyes. Electron-donating methyl groups in all position for dyes 3a–k cause hypsochromical shifts in all used solvents when compared with the other dyes. Also electronaccepting nitro groups in m-positions (3e and 4e) resulted in hypsochromical shifts in all used solvents when compared the other dyes.
364
4. Conclusions
372
365 366 367 368 369 370 371
Two series disazo pyrazole disperse dyes were synthesized by some 373 diazotizing and coupling reactions. Solvent, substituent and acid–base 374 influences on the wavelength of maximum absorption have been 375
U
t3:3
t4:3 t4:4 t4:5
3.4. Substituent effects on UV–vis spectra
N
347 348
C
338 339
E
336 Q4 337
R
334 335
R
332 333
O
330 331
C
328 329
Methanol + HCl
T
324
326 327
Dye λmax (nm) no. Methanol Methanol + KOH
O
t2:5
DMF
R O
DMSO
P
Dye no.
D
t2:3 t2:4
t4:1 t4:2
Table 4 Absorption maxima of dyes 4a–k in acidic and basic solutions.
F
Table 2 Influence of solvent on λmax (nm) of dyes 4a–k.
E
t2:1 t2:2
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
λmax (nm) Methanol
Methanol + KOH
Methanol + HCl
Chloroform
Chloroform + piperidine
Acetic acid
435, 340 413, 350 421, 339 398, 339 379, 340 413, 336 394, 337 385, 348 385 410, 341 392, 337
555, 371 415, 361 405, 339 408, 339 410, 326 428, 336 415, 335 413, 344 384 409, 342 400, 340
435, 341 414, 351 423, 339 401, 339 382, 344 410, 335 385, 338 418, 358 380 414, 339 403, 333
432, 341 416, 364 415, 343 402, 344 385, 341 399, 340 397, 345 440, 378 395 412, 341 409, 340
550, 433 410, 348 394, 344 389, 339 421, 380 405, 339 389, 340 444, 342 371 421, 330 405, 337
428, 334 415, 362 423, 339 401, 340 378, 337 400, 335 394, 339 409, 344 380 413, 337 406, 333
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
7
O
F
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
Fig. 4. Absorption spectra of dye 4a in acidic and basic solutions.
Acknowledgements
P
384
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385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428
D
References
E Fig. 2. Absorption spectra of dye 4a in various solvents.
381
The authors are grateful to PAUBAP for financial support with the 382 project number of 2012FBE035. 383
T C E R R
379 380
studied. Newly synthesized some disazo pyrazole disperse dyes showed solvatochromic effects. New peaks at long wavelength were observed besides the other peaks in the absorption spectra of 3a and 4a dyes in DMF and DMSO. It was also observed that the absorption spectra of 3a and 4a dyes in methanol were quite sensitive to the alkali addition.
N C O
377 378
U
376
R O
Fig. 1. Absorption spectra of dye 3a in various solvents.
429
Fig. 3. Absorption spectra of dye 3a in acidic and basic solutions.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
Contents lists available at ScienceDirect
Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq
3Q2
Fikret Karcı a,⁎, Emine Bakan b a
6
a r t i c l e
7 8 9 10 11
Article history: Received 28 January 2015 Received in revised form 23 February 2015 Accepted 24 February 2015 Available online xxxx
12 25 13 14 15 16 17 18
Keywords: Disperse dyes Disazo dyes Pyrazole dyes Absorption ability Solvatochromism Tautomeric structure
i n f o
R O
Pamukkale University, Faculty of Science–Arts, Department of Chemistry, Denizli, Turkey Uşak University, Higher Vocational School of Ulubey, Fashion Design Programme, Ulubey, Uşak, Turkey
a b s t r a c t
C
29 27 26 28
1. Introduction
31
Simple nitrogen-containing heterocycles receive significant attention in the literature due to their exciting biological properties as well as their historical important role as pharmacophores. The synthesis, reactions and biological activities of pyrazole containing molecules, of these heterocycles, lead to an ever-expanding research area in heterocyclic chemistry and moreover; these structures appear in a large number of pharmaceutical agents and natural products. Fused pyrazoles with many different derivatives may exhibit a wide range of interesting properties such as antihyperglycemic, analgestic, anti-inflammatory, antipyretic, anti-bacterial, hypoglycaemic and sedative-hypnotic activities. Recently, some pyrazoles were reported to display nonnucleoside HIV1 reverse transcriptase inhibitory activity [1–6]. Some azopyrazole derivatives also find applications in dyes, biological and pharmacological studies and complexes [7–12]. The condensation of β-enaminonitriles and β-ketoesters with hydrazines continues to be the most widely used method for aminopyrazole and pyrazolone formation, respectively [13–16]. The amino derivatives of pyrazoles belong to important compounds used for the preparation of other functional derivatives mainly for the synthesis of condensed heterocyclic systems [17–19]. The use of heterocyclic intermediates in the synthesis of azo disperse dyes is well established and the resultant dyes exhibit good tinctorial strength and brighter appearance than those derived from aniline-
38 39 40 41 42 43 44 45 46 47 48 49 50 51 52
R
R
N C O
36 37
U
34 35
E
30
32 33
19 20 21 22 23 24
E
D
P
5-amino-4-arylazo-3-methyl-1-phenylpyrazoles (2a–k) were diazotised and coupled with 5-hydroxy-3-methyl1H-pyrazole and 5-hydroxy-3-methyl-1-phenylpyrazole to generate two series disazo pyrazole disperse dyes (3a–k and 4a–k). These novel synthesized disazo pyrazole disperse dyes were characterized by elemental analysis and spectral methods. Absorption ability and tautomeric structure of synthesized disazo pyrazole disperse dyes substituted with electron-withdrawing and electron-donating groups at their o, m- and p-positions were also examined in detail. © 2015 Published by Elsevier B.V.
T
b
O
4 5
F
2
New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures
1Q1
⁎ Corresponding author. E-mail address: [email protected] (F. Karcı).
based diazo components. For instance, amino-substituted thiazole, benzothiazole [20–23] and benzoisothiazole [24] compounds afford highly electronegative diazo components and consequently, provide a pronounced bathochromic effect compared to the corresponding benzoid compounds. Moreover, azo disperse dyes containing 5hydroxy-3-methyl-1H-pyrazole as coupling component were reported to be in red–violet colours in the literature [25,26]. We have previously reported the synthesis of some disazo disperse dyes [27–32]. In this study, we report the synthesis of two different series of new disazo disperse dyes based on two pyrazole rings in one dye structure. The absorption ability of these dyes substituted with electron-withdrawing and electron-donating groups at their o, m- and p-positions was also examined in detail.
53
2. Experimental
66
2.1. General
67
The chemicals, used for the synthesis of the compounds, were obtained from Aldrich and Merck without further purification. The solvents used were of spectroscopic grade. IR spectra were determined via Mattson 1000 Fourier Transforminfrared (FT-IR) spectrophotometer using a KBr disc. Nuclear magnetic resonance (1H NMR) spectra were recorded on a Bruker-Spectrospin Avance DPX 400 Ultra-Shield in deuterated dimethylsulphoxide (DMSO-d6) using tetramethylsilane (TMS) as the internal reference and chemical shifts (δ) were given in ppm. Ultraviolet–visible (UV–
68
http://dx.doi.org/10.1016/j.molliq.2015.02.032 0167-7322/© 2015 Published by Elsevier B.V.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
54 55 56 57 58 59 60 61 62 63 64 65
69 70 71 72 73 74 75 76
2
86 87
2.2. Synthesis of 2-arylhydrazono-3-ketiminobutyronitriles (1a–k) and 5amino-4-arylazo-3-methyl-1-phenylpyrazoles (2a–k)
91
2.3. Synthesis of disperse disazo pyrazole dyes (3a–k and 4a–k)
92
5-Amino-4-arylazo-3-methyl-1-phenylpyrazoles (0.01 mol) were dissolved 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. Sodium nitrite (0.69 g, 0.01 mol) in water (10 ml) was then added to this solution dropwise with vigorous stirring, for 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 5-hydroxy-3-methyl1H-pyrazole or 5-hydroxy-3-methyl-1-phenylpyrazole (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 simultaneous sodium acetate solution addition. The mixture was then stirred for 2 h at 0–5 °C. The precipitated product separated upon dilution with water (50 ml) was filtered off, washed with water several times, dried and crystallized from DMF–H2O.
105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121
C
104
2.3.1. 4-(4′-(p-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)-5hydroxy-3-methyl-1H-pyrazole (3a) Red crystals; yield 74%; mp. 210–211 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3244 (NH), 3057 (Ar–H), 2923 (Al–H), 1663 (C_O), 1493 (N_N); 1H-NMR (DMSO-d6): δ = 2.23 (s, 3H, CH3), 2.72 (s, 3H, CH3), 6.84–8.42 (m, 9H, ArH), 9.97 (br, 1H, OH), 11.55 (br, 1H, NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.12, H: 3.85, N: 29.30.
E
102 103
R
100 101
R
98 99
O
96 97
2.3.2. 4-(4′-(p-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3b) Yellow crystals; yield 48 %; mp. dec. N 96 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3195 (NH), 3071 (Ar–H), 2923 (Al–H), 1649 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.76 (s, 3H, CH3), 3.84 (s, 3H, p-OCH3), 7.09–8.01 (m, 9H, ArH), 11.70 (br, OH), 13.37 (br, NH), 13.91 (br, hydrazo NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C21H20N8O2: C: 60.57, H: 4.84, N: 26.91. Found: C: 60.35, H: 4.89, N: 26.80.
C
94 95
N
93
U
88
130 131
2.3.5. 4-(4′-(m-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3e) Brown crystals; yield 68 %; mp. 131–132 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3107 (NH), 3036 (Ar–H), 2870 (Al–H), 1666 (C_O), 1525 (N_N); 1H-NMR (DMSO-d6): δ = 2.21 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.21–8.79 (m, 9H, ArH), 9.86 (br, OH), 11.32 (br, NH), 11.81 (br, hydrazo NH), 14.13 (br, hydrazo NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.79, H: 3.99, N: 29.33.
138
+
N2 Cl X
_
NC C
+ H
C CH3
N N H
128 129
132 133 134 135 136 137
139 140 141 142 143 144 145
2.3.7. 4-(4′-(m-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3g) Greenish black crystals; yield 35 %; mp. 104–105 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3170 (NH), 3064 (Ar–H), 2919 (Al–H), 1659 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.29 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.41 (s, 3H, m-CH3), 7.04–7.95 (m, 9H, ArH), 11.74 (br, OH), 13.26 (br, NH), 14.15 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 63.15, H: 5.12, N: 28.21.
154 155
2.3.8. 4-(4′-(o-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)-5hydroxy-3-methyl-1H-pyrazole (3h) Red crystals; yield 55 %; mp. 200–201 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3262 (NH), 3054 (Ar–H), 2926 (Al–H), 1670 (C_O), 1486 (N_N); 1H-NMR (DMSO-d6): δ = 2.25 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.29–8.22 (m, 9H, ArH), 10.12 (br, OH), 11.57 (br, NH), 13.98 (br, hydrazo NH); Anal. Calcd. for C20H17N9O3: C: 55.68, H: 3.97, N: 29.22. Found: C: 55.56, H: 4.03, N: 29.45.
162 163
C
X
NH
PhNHNH2 N
C CH3
(1a-k)
a, X : p-NO2 b, X : p-OCH3 c, X : p-Cl d, X : p-CH3
126 127
146
CN
NH2
124 125
2.3.6. 4-(4′-(m-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3f) Orange crystals; yield 70 %; mp. 114–115 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3061 (Ar–H), 2926 (Al–H), 1670 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.71 (s, 3H, CH3), 7.22–8.13 (m, 9H, ArH), 11.79 (br, NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 57.14, H: 3.89, N: 26.69.
T
89 90
2-Arylhydrazone-3-ketiminobutyronitriles (1a–k) and 5-amino-4arylazo-3-methyl-1-phenylpyrazoles (2a–k) were prepared according to the literature procedures [16,33,34]. The general route for the synthesis of 2-arylhydrazono-3-ketiminobutyronitriles and 5-amino-4arylazo-3-methyl-1-phenylpyrazoles is outlined in Scheme 1.
2.3.4. 4-(4′-(p-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3d) Orange crystals; yield 58 %; mp. 90–91 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3047 (Ar–H), 2916 (Al–H), 1666 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.28 (s, 3H, CH3), 2.67 (s, 3H, CH3), 2.38 (s, 3H, p-CH3), 7.16–8.03 (m, 9H, ArH), 11.71 (br, OH), 13.30 (br, NH), 14.17 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 62.90, H: 4.90, N: 27.91.
F
85
O
84
R O
83
122 123
P
81 82
2.3.3. 4-(4′-(p-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (3c) Yellow crystals; yield 65 %; mp. 120–121 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3188 (NH), 3064 (Ar–H), 2926 (Al–H), 1666 (C_O), 1529 (N_N); 1H-NMR (DMSO-d6): δ = 2.29 (s, 3H, CH3), 2.69 (s, 3H, CH3), 7.47–8.13 (m, 9H, ArH), 11.74 (br, NH), 14.18 (br, hydrazo NH); Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 56.95, H: 4.23, N: 26.55.
D
79 80
vis) absorption spectra were recorded via a Schimadzu UV-1601 double beam spectrophotometer at the wavelength of maximum absorption (λmax) in a range of different solvents, i.e. DMSO, DMF, acetonitrile, methanol, acetic acid and chloroform at various concentrations (1 × 10−6–10−8). Melting points were determined on an Electrothermal 9100 melting point apparatus and are uncorrected. Elemental analysis was carried out using a Leco CHNS-932 analyzer.
E
77 78
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
e, X : m-NO2 f, X : m-Cl g, X : m-CH3
N
X H3C
h, X : o-NO2 i, X : o-OCH3 j, X : o-Cl k, X : o-CH3
NH2 N N (2a-k)
Scheme 1. Synthesis of aminoarylazopyrazoles (2a–k).
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
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189 190 191 192 193
194 195 196 197 198 199 200 201
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218 219 220 221 222 223 224 225
2.3.18. 4-(4′-(m-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4g) Orange crystals; yield 35 %; mp. 230–231 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3131 (NH), 3054 (Ar–H), 2916 (Al–H), 1666 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.74 (s, 3H, CH3), 2.37 (s, 3H, m-CH3), 7.06–8.46 (m, 14H, ArH), 13.29 (br, NH), 14.34 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 68.11, H: 5.22, N: 23.70.
242
2.3.12. 4-(4′-(p-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1-phenylpyrazole (4a) Red crystals; yield 67 %; mp. 332–333 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3128 (NH), 3064 (Ar–H), 2926 (Al–H), 1666 (C_O), 1507 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.76 (s, 3H, CH3), 7.41–8.52 (m, 14H, ArH), 13.37 (br, NH), 14.30 (br, hydrazo NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.42, H: 4.02, N: 24.71.
2.3.19. 4-(4′-(o-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1-phenylpyrazole (4h) Red crystals; yield 78 %; mp. 150–151 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3262 (NH), 3057 (Ar–H), 2923 (Al–H), 1666 (C_O), 1486 (N_N); 1H-NMR (DMSO-d6): δ = 2.26 (s, 3H, CH3), 2.73 (s, 3H, CH3), 7.28–8.20 (m, 14H, ArH), 10.12 (br, OH), 11.57 (br, NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.65, H: 4.29, N: 24.97.
250
2.3.13. 4-(4′-(p-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4b) Brown crystals; yield 33 %; mp. dec. N 104 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3212 (NH), 3064 (Ar–H), 2965 (Al–H), 1666 (C_O), 1497 (N_N); 1H-NMR (DMSO-d6): δ = 2.28 (s, 3H, CH3), 2.73 (s, 3H, CH3), 3.78 (s, 3H, p-OCH3), 7.02–8.14 (m, 14H, ArH), 13.38 (br, NH), 14.20 (br, hydrazo NH);Anal. Calcd. for C27H24N8O2: C: 65.84, H: 4.91, N: 22.75. Found: C: 65.71, H: 4.98, N: 22.94.
2.3.20. 4-(4′-(o-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phneylpyrazole (4i) Brown crystals; yield 44 %; mp. dec. N 105 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3276 (NH), 3064 (Ar–H), 2934 (Al–H), 1670 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.32 (s, 3H, CH3), 2.73 (s, 3H, CH3), 3.97 (s, 3H, o-OCH3), 7.02–7.95 (m, 14H, ArH), 10.59 (br, OH), 13.73 (br, NH), 14.64 (br, hydrazo NH); Anal. Calcd. for C27H24N8O2: C: 65.84, H: 4.91, N: 22.75. Found: C: 65.91, H: 5.01, N: 22.63.
258 259
2.3.14. 4-(4′-(p-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4c) Orange crystals; yield 62 %; mp. 300–301 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3191 (NH), 3064 (Ar–H), 2926 (Al–H), 1659 (C_O), 1500 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.74 (s, 3H, CH3), 7.20–8.19 (m, 14H, ArH), 14.30 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.90, H: 4.33, N: 22.59.
2.3.21. 4-(4′-(o-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4j) Orange crystals; yield 90 %; mp. 175–176 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3142 (NH), 3061 (Ar–H), 2923 (Al–H), 1659 (C_O), 1536 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.70 (s, 3H, CH3), 7.23–7.88 (m, 14H, ArH), 13.77 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.75, H: 4.30, N: 22.24.
266 267
2.3.15. 4-(4′-(p-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4d) Orange crystals; yield 60 %; mp. 259–260 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3191 (NH), 3025 (Ar–H), 2919 (Al–H), 1659 (C_O), 1504 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.39 (s, 3H, p-CH3), 7.20–8.09 (m, 14H, ArH), 12.20 (br, OH), 13.30 (br, NH), 14.21 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 68.14, H: 5.32, N: 23.65.
2.3.22. 4-(4′-(o-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4k) Orange crystals; yield 92 %; mp. 241–242 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3195 (NH), 3061 (Ar–H), 2923 (Al–H), 1666 (C_O), 1539 (N_N); 1H-NMR (DMSO-d6): δ = 2.27 (s, 3H, CH3), 2.73 (s, 3H, CH3), 2.36 (s, 3H, o-CH3), 7.23–7.87 (m, 14H, ArH), 13.85 (br, hydrazo NH); Anal. Calcd. for C27H24N8O: C: 68.05, H: 5.08, N: 23.51. Found: C: 67.92, H: 4.87, N: 23.45.
274
O
F
2.3.11. 4-(4′-(o-methylphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3k) Brown crystals; yield 32 %; mp. 180–181 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3149 (NH), 3064 (Ar–H), 2979 (Al–H), 1663 (C_O), 1500 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 2.36 (s, 3H, o-CH3), 7.30–7.93 (m, 9H, ArH), 11.65 (br, NH), 13.78 (br, hydrazo NH); Anal. Calcd. for C21H20N8O: C: 62.99, H: 5.03, N: 27.98. Found: C: 63.23, H: 4.95, N: 28.05.
R O
187 188
P
186
D
184 185
234 235
E
182 183
2.3.17. 4-(4′-(m-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1-phenylpyrazole (4f) Orange crystals; yield 63 %; mp. 125–126 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3134 (NH), 3061 (Ar–H), 2926 (Al–H), 1670 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.31 (s, 3H, CH3), 2.73 (s, 3H, CH3), 7.51–7.81 (m, 14H, ArH), 14.34 (br, hydrazo NH); Anal. Calcd. for C26H21ClN8O: C: 62.84, H: 4.26, N: 22.55. Found: C: 62.88, H: 4.34, N: 22.63.
T
180 181
2.3.10. 4-(4′-(o-chlorophenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3j) Brown crystals; yield 45 %; mp. 196–197 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3230 (NH), 3064 (Ar–H), 2923 (Al–H), 1677 (C_O), 1532 (N_N); 1H-NMR (DMSO-d6): δ = 2.31 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.41–7.70 (m, 9H, ArH), 11.61 (br, NH), 13.74 (br, hydrazo NH);Anal. Calcd. for C20H17ClN8O: C: 57.08, H: 4.07, N: 26.63. Found: C: 57.33, H: 4.19, N: 26.86.
C
178 179
E
177
R
176
226 227
R
174 175
2.3.16. 4-(4′-(m-nitrophenylazo)-3′-methyl-1′-phenylpyrazole-5′-ylazo)5-hydroxy-3-methyl-1H-pyrazole (4e) Brick red crystals; yield 58 %; mp. 134–135 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3248 (NH), 3075 (Ar–H), 2919 (Al–H), 1652 (C_O), 1522 (N_N); 1H-NMR (DMSO-d6): δ = 2.33 (s, 3H, CH3), 2.72 (s, 3H, CH3), 7.69–8.70 (m, 14H, ArH), 9.86 (br, OH), 11.34 (br, NH), 13.28 (br, hydrazo NH); Anal. Calcd. for C26H21N9O3: C: 61.53, H: 4.17, N: 24.84. Found: C: 61.20, H: 4.05, N: 25.03.
N C O
172 173
2.3.9. 4-(4′-(o-methoxyphenylazo)-3′-methyl-1′-phenylpyrazole-5′ylazo)-5-hydroxy-3-methyl-1H-pyrazole (3i) Brown crystals; yield 36 %; mp. 117–118 °C (DMF–H2O); IR (KBr): ν (cm−1) = 3276 (NH), 3071 (Ar–H), 2941 (Al–H), 1663 (C_O), 1529 (N_N); 1H-NMR (DMSO-d6): δ = 2.30 (s, 3H, CH3), 2.72 (s, 3H, CH3), 3.92 (s, 3H, o-OCH3), 7.04–7.92 (m, 9H, ArH), 10.59 (br, OH), 11.59 (br, NH), 14.64 (br, hydrazo NH); Anal. Calcd. for C21H20N8O2: C: 60.57, H: 4.84, N: 26.91. Found: C: 60.28, H: 4.87, N: 26.74.
U
170 171
3
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
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236 237 238 239 240 241
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251 252 253 254 255 256 257
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268 269 270 271 272 273
275 276 277 278 279 280 281
4
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
HO
H N N
H N
HO
N
CH3 N
N
CH3
N N
X N
H3C N
N
N
NH2 N
H3C
N
(3a-k)
X
NaNO2/HCl
X
+ N2 Cl
N
N
_
N
H3C
CH3COOH
N
(2a-k) N
F
HO
N
N
O
X
H3C
N N
CH3
N N N
N (4a-k)
R O
HO
N
CH3
N
N
H N
O
N N X
N
E N
HO
N
N
N
N N
N
O
H
CH3
N N
disazo-enol
(T3)
N
- H+ +
H3C
azo-hydrazo-enol
U
N
N
X
C
N N
_
CH3
N N
X H3C
KT
HO
O
H N
(T2)
R
KT
N
N
azo-hydrazo-keto
R
(T1)
CH3
N N
H3C
N
disazo-enol
N
N
C
X H3C
N
H
KT
CH3
N N
H N
T
HO
E
D
P
Scheme 2. Synthesis of disperse disazo pyrazole dyes 3a–k and 4a–k.
H+
N
N N
H N N CH3
X H3C
N N
anionic form (A1)
(T4) KT
KT
O
N
N
N N
H N NH CH3
X H3C
N N
disazo-keto (T5)
Scheme 3. Tautomeric equilibriums of dyes 3a–k.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
HO
N
N
O
N
N N
N
N N
H
KT
CH3
5
N
N
N N
CH3
X
X N
H3C
N
H3C
N
N _ O
disazo-enol
azo-hydrazo-keto
(T6)
KT
(T7)
KT
N
- H+ +
N
N N
N N CH3
X
H+
N N
N
N
N
N N
H
CH3
X N
H3C
anionic form (A2)
R O
N
O
O
F
H3C
N
disazo-keto
P
(T8)
D
Scheme 4. Tautomeric equilibriums of dyes 4a–k.
3. Results and discussion
283
3.1. Spectral characteristics and tautomerism
284
300 301
Disazo pyrazole disperse dyes 3a–k can exist in five possible tautomeric forms, namely the disazo-enol forms T1 and T4, the azohydrazo-keto form T2, the azo-hydrazo-enol form T3 and the disazoketo form T5 as shown in Scheme 3. The FT-IR spectra of 3a–k dyes displayed imino (NH) bands at 3107–3276 cm− 1, carbonyl (C_O) bands at 1649–1677 cm−1 and diazo (N_N) bands at 1486– 1536 cm−1. The other νmax values of 3036–3071 cm−1 (aromatic C– H) and 2870–2979 cm−1 (aliphatic C–H) were also recorded. On the other hand, disazo disperse dyes 4a–k can exist in three possible tautomeric forms, namely the disazo-enol form T6, the azo-hydrazo-keto form T7 and the disazo-keto form T8 as shown in Scheme 4. The FT-IR spectra of 4a–k dyes exhibited imino (NH) bands at 3128–3276 cm−1, carbonyl (C_O) bands at 1652–1670 cm−1 and diazo (N_N) bands at 1486–1539 cm−1. The other νmax values of 3025–3075 cm−1 (aromatic C–H) and 2916–2965 cm−1 (aliphatic C–H) were also recorded. Also, FT-IR spectra of disazo pyrazole disperse dyes (3a–k and 4a–k) did not exhibit any broad bands for hydroxyl group. These suggest that disazo pyrazole disperse dyes 3a–k are predominantly in azo-
t1:1 t1:2
Table 1 Influence of solvent on λmax (nm) of dyes 3a–k.
292 293 294 295 296 297 298 299
T
C
E
R
291
R
289 290
N C O
287 288
U
285 286
hydrazo-keto form T2 or disazo-keto form T5 and 4a–k are predominantly in azo-hydrazo-keto form T7 or disazo-keto form T8 as opposed to the other tautomeric forms in the solid state (Schemes 3 and 4). (See Scheme 2.) 1 H NMR spectra of dyes 3a displayed one broad peak at 9.97 ppm (OH) and one broad peak at 11.55 ppm (NH). This result suggests that dye 3a is present as one of T1, T3 and T4 as opposed to the other tautomeric forms in DMSO-d6. 1H NMR spectra of 3b, 3d, 3e, 3g, 3h, 3i dyes exhibited one hydroxyl (OH) peak, one imino (NH) peak and hydrazo NH peaks. These results suggest that 3b, 3d, 3e, 3g, 3h, 3i dyes are in the mixture of tautomeric forms in DMSO-d6. 1H NMR spectra of 3c, 3f, 3j and 3k dyes showed one imino (NH) peak and hydrazo NH peaks. These results suggest that 3c, 3f, 3j and 3k dyes are present as one or mixture of T2 and T5 as opposed to the other tautomeric forms in DMSO-d6. 1 H NMR spectra of 4a–c, 4f, 4g, 4j and 4k dyes displayed only NH peaks and did not exhibit any broad peaks for hydroxyl (OH) groups. These results suggest that 4a–c, 4f, 4g, 4j and 4k dyes are present as one or mixture of T7 and T8 as opposed to the other tautomeric form T6 in DMSO-d6. On the other hand, 1H NMR spectra of 4d, 4e, 4h and 4i dyes both showed NH peaks and OH peaks. These results suggest that 4d, 4e, 4h and 4i dyes are in the mixture of tautomeric forms in DMSO-d6.
E
282
t1:3
Dye no.
DMSO
DMF
Acetonitrile
Methanol
Acetic acid
Chloroform
t1:4 t1:5 t1:6 t1:7 t1:8 t1:9 t1:10 t1:11 t1:12 t1:13 t1:14
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
452, 350 418, 304 420, 345 397, 346 386, 343 438, 343 391, 347 443, 387 386 422, 343 395, 340
444, 342, 586 416, 364 420, 343 402, 345 390, 340 424, 340 394, 345 443, 385 385 421, 342 406, 340
429, 336 411, 364 420, 341 394, 342 381, 340 438, 338 387, 341 434, 373 381 417, 341 399, 338
435, 340 413, 350 421, 339 398, 339 379, 340 413, 336 394, 337 385, 348 385 410, 341 392, 337
428, 334 415, 362 423, 339 401, 340 378, 337 400, 335 394, 339 409, 344 380 413, 337 406, 333
432, 341 416, 364 415, 343 402, 344 385, 341 399, 340 397, 345 440, 378 395 412, 341 409, 340
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
302 303 304 305 Q3 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323
6
4a
t2:6 t2:7 t2:8 t2:9 t2:10 t2:11 t2:12 t2:13 t2:14 t2:15
4b 4c 4d 4e 4f 4g 4h 4i 4j 4k
451, 357, 590 420, 364 420, 345 422, 345 395, 340 420, 340 418, 343 431, 348 405, 363 409, 341 410, 338
Acetonitrile
440, 356, 584 418, 357 424, 344 423, 344 401, 340 425, 340 420, 341 426, 349 406, 361 411, 339 413, 337
Methanol
Acetic acid
Chloroform
428, 351
433, 353
427, 346
429, 354
411, 358 420, 341 411, 341 394, 338 414, 338 411, 339 421, 347 398, 359 403, 335 405, 334
414, 361 419, 337 398, 340 389, 337 412, 337 401, 337 410, 348 396, 361 421, 340 409, 333
416, 352 419, 339 409, 341 396, 335 411, 336 415, 336 412, 341 405, 358 408, 332 408, 332
419, 358 421, 343 416, 344 399, 339 415, 340 415, 341 425, 349 406, 361 401, 339 408, 338
3.2. Solvent effects on UV–vis spectra
325
340
The UV–vis absorption spectra of 3a–k and 4a–k dyes were recorded over the range of λ between 300 and 700 nm, using a variety of solvents in concentrations (10−6–10−8 M) and the results are summarised in Tables 1 and 2. The visible absorption spectra of the dyes did not correlate with the polarity of solvents. 3a–k and 4a–k dyes resulted in two maximum absorption peaks in all used solvents, except for 3i. These results suggest that 3a–k and 4a–k dyes are present in the mixture of tautomeric forms in all used solvents, except for 3i. Dye 3i is present in a single tautomeric form in all used solvents. It was observed that λmax of 3a–k and 4a–k dyes did not change significantly in all used solvents, except for 3a and 4a. It was also observed that new peaks at long wavelength besides other peaks in absorption spectra of 3a and 4a dyes in DMF and DMSO. These results suggest that 3a and 4a dyes are present in the mixture of tautomeric forms and an anionic form in DMF and DMSO.
341
3.3. Acid and base effects on UV–vis spectra
342 343
349 350
The effects of acid and base on the absorption of dye solutions were investigated and the results are shown in Tables 3 and 4. The absorption spectra of the 3a and 4a dyes in methanol was quite sensitive to alkali addition (potassium hydroxide, 0.1 M), with λmax of 3a and 4a dyes showing bathochromic shifts. Absorption curves of the dye 3a resembled those of DMF (Fig. 3) while absorption curves of the dye 4a were similar to those of DMF and DMSO (Fig. 4). The absorption spectra of the other dyes in methanol were not sensitive to alkali addition (potassium hydroxide, 0.1 M). These results suggest that 3a and 4a dyes are
t3:1 t3:2
Table 3 Absorption maxima of dyes 3a–k in acidic and basic solutions.
344 345 346
Chloroform Chloroform + piperidine
Acetic acid
4a
433, 353
430, 365
429, 354
421, 352
427, 346
t4:6
4b 4c 4d 4e 4f 4g 4h 4i 4j 4k
414, 361 419, 337 398, 340 389, 337 412, 337 401, 337 410, 348 396, 361 421, 340 409, 333
413, 360 416, 337 405, 340 389, 340 414, 337 401, 337 411, 342 400, 362 413, 333 408, 332
419, 358 421, 343 416, 344 399, 339 415, 340 415, 341 425, 349 406, 361 401, 339 408, 338
413, 351 421, 340 412, 331 399, 311 415, 302 412, 340 427, 340 407, 360 403, 340 414, 305
416, 352 419, 339 409, 341 396, 335 411, 336 415, 336 412, 341 405, 358 408, 332 408, 332
t4:7 t4:8 t4:9 t4:10 t4:11 t4:12 t4:13 t4:14 t4:15 t4:16
440, 369, 553 408, 363 418, 339 402, 339 423, 329 419, 336 403, 335 413, 345 401,360 433, 342 434, 336
present in the mixture of tautomeric forms and an anionic form in strong basic solutions. (See Figs. 1 and 2.) When hydrochloric acid (0.1 M) was added to dye solutions in methanol, λmax of 3a–k and 4a–k dyes did not change significantly and the absorption spectra of dyes were similar to those in acetic acid (Figs. 3 and 4). When piperidine was added to dye 3a solutions in chloroform, λmax of dye 3a exhibited bathochromic shift. This result suggests that dye 3a is present in the mixture of tautomeric forms and an anionic form in weak basic solutions. λmax of 3b–k and 4a–k dyes did not change significantly when a small amount of piperidine was added to 3b–k and 4a–k dyes solution in chloroform.
Dye no.
t3:4 t3:5 t3:6 t3:7 t3:8 t3:9 t3:10 t3:11 t3:12 t3:13 t3:14 t3:15
3a 3b 3c 3d 3e 3f 3g 3h 3i 3j 3k
351 352 Q5 353 354 355 356 357 358 359 360 361 362 363
As seen in Tables 1 and 2, generally, electron-accepting nitro groups in p- and o-positions for dyes caused bathochromical shifts in all used solvents when compared with the other dyes. Electron-donating methyl groups in all position for dyes 3a–k cause hypsochromical shifts in all used solvents when compared with the other dyes. Also electronaccepting nitro groups in m-positions (3e and 4e) resulted in hypsochromical shifts in all used solvents when compared the other dyes.
364
4. Conclusions
372
365 366 367 368 369 370 371
Two series disazo pyrazole disperse dyes were synthesized by some 373 diazotizing and coupling reactions. Solvent, substituent and acid–base 374 influences on the wavelength of maximum absorption have been 375
U
t3:3
t4:3 t4:4 t4:5
3.4. Substituent effects on UV–vis spectra
N
347 348
C
338 339
E
336 Q4 337
R
334 335
R
332 333
O
330 331
C
328 329
Methanol + HCl
T
324
326 327
Dye λmax (nm) no. Methanol Methanol + KOH
O
t2:5
DMF
R O
DMSO
P
Dye no.
D
t2:3 t2:4
t4:1 t4:2
Table 4 Absorption maxima of dyes 4a–k in acidic and basic solutions.
F
Table 2 Influence of solvent on λmax (nm) of dyes 4a–k.
E
t2:1 t2:2
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
λmax (nm) Methanol
Methanol + KOH
Methanol + HCl
Chloroform
Chloroform + piperidine
Acetic acid
435, 340 413, 350 421, 339 398, 339 379, 340 413, 336 394, 337 385, 348 385 410, 341 392, 337
555, 371 415, 361 405, 339 408, 339 410, 326 428, 336 415, 335 413, 344 384 409, 342 400, 340
435, 341 414, 351 423, 339 401, 339 382, 344 410, 335 385, 338 418, 358 380 414, 339 403, 333
432, 341 416, 364 415, 343 402, 344 385, 341 399, 340 397, 345 440, 378 395 412, 341 409, 340
550, 433 410, 348 394, 344 389, 339 421, 380 405, 339 389, 340 444, 342 371 421, 330 405, 337
428, 334 415, 362 423, 339 401, 340 378, 337 400, 335 394, 339 409, 344 380 413, 337 406, 333
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032
7
O
F
F. Karcı, E. Bakan / Journal of Molecular Liquids xxx (2015) xxx–xxx
Fig. 4. Absorption spectra of dye 4a in acidic and basic solutions.
Acknowledgements
P
384
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385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428
D
References
E Fig. 2. Absorption spectra of dye 4a in various solvents.
381
The authors are grateful to PAUBAP for financial support with the 382 project number of 2012FBE035. 383
T C E R R
379 380
studied. Newly synthesized some disazo pyrazole disperse dyes showed solvatochromic effects. New peaks at long wavelength were observed besides the other peaks in the absorption spectra of 3a and 4a dyes in DMF and DMSO. It was also observed that the absorption spectra of 3a and 4a dyes in methanol were quite sensitive to the alkali addition.
N C O
377 378
U
376
R O
Fig. 1. Absorption spectra of dye 3a in various solvents.
429
Fig. 3. Absorption spectra of dye 3a in acidic and basic solutions.
Please cite this article as: F. Karcı, E. Bakan, New disazo pyrazole disperse dyes: Synthesis, spectroscopic studies and tautomeric structures, J. Mol. Liq. (2015), http://dx.doi.org/10.1016/j.molliq.2015.02.032