The synthesis, characterization and investigation of absorption properties of disperse disazo dyes containing pyrazole and isoxazole

Accepted Manuscript The Synthesis, Characterization and Investigation of Absorption Properties of Disperse Disazo Dyes Containing Pyrazole and Isoxazole

Aykut Demirçalı, Fikret Karcı, Ozan Avinc, Aylin Uğur Kahrıman, Görkem Gedik, Emine Bakan PII:

S0022-2860(18)31454-6

DOI:

10.1016/j.molstruc.2018.12.033

Reference:

MOLSTR 25970

To appear in:

Journal of Molecular Structure

Received Date:

23 August 2018

Accepted Date:

08 December 2018

Please cite this article as: Aykut Demirçalı, Fikret Karcı, Ozan Avinc, Aylin Uğur Kahrıman, Görkem Gedik, Emine Bakan, The Synthesis, Characterization and Investigation of Absorption Properties of Disperse Disazo Dyes Containing Pyrazole and Isoxazole, Journal of Molecular Structure (2018), doi: 10.1016/j.molstruc.2018.12.033

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ACCEPTED MANUSCRIPT The Synthesis, Characterization and Investigation of Absorption Properties of Disperse Disazo Dyes Containing Pyrazole and Isoxazole Aykut Demirçalı1, Fikret Karcı1, Ozan Avinc2, Aylin Uğur Kahrıman1, Görkem Gedik2, Emine Bakan3* Pamukkale University, Faculty of Science-Arts, Department of Chemistry, Denizli, Turkey University, Faculty of Engineering, Department of Textile Engineering, Denizli, Turkey 3 Uşak University, Higher Vocational School of Ulubey, Fashion Design Programme, Ulubey, Uşak, Turkey 1

2Pamukkale

*Corresponding Author: [email protected]

Abstract In this study, new heterocyclic disazo disperse dyes, substituted with methyl, nitro and chloro groups at their o-, m-, p- positions were synthesized (4a-4j). These newly synthesized ten disazo disperse dyes were characterized by elemental analysis and spectral techniques. Spectroscopic data for novel synthesized dyes, dissolved in six solvents, were procured. The influences of six different acidic and alkaline solutions were also reported. In addition, the absorption capability of these ten-novel heterocyclic disazo disperse dyes at their o-, m- and p- positions were explored in detail. Keywords: Disperse dye synthesis, Heterocyclic disazo disperse dye, Spectroscopic properties.

*Corresponding author. Phone: +90 276 7162739 Fax: +90 276 7162817 *E-mail address: [email protected]

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ACCEPTED MANUSCRIPT 1. Introduction According to the chemical compound classification, most widely used and preferred textile dyes are azo dyes due to their dyeing power, easy production of its cheap basic materials, their wide color range and good fastness properties [1-10]. Main disadvantage of azo dyes is to give dull shades on blue-violet color range [11-14]. However, this disadvantage was being overcome with the use of heterocyclic compounds in this color range leading to brighter colors [15-19]. Therefore, in the recent years, the usage of aromatic heterocyclic compound as a disazo or coupling component has gained importance [20-26]. Pyrazoles are one of the important class of heterocyles according to their wide using areas [27- 29]. On the other hand, pyrazole dyestuffs color and fastness properties on synthetic fibers give good results. Since commercial disperse dyes generally dye synthetic fibers, it is very important to produce new disperse dyes which dye synthetics with high color yields along with good fastness properties [13]. In this study, heterocyclic disazo disperse dyes substituted with methyl (-CH3), nitro (-NO2) and chloro (-Cl) groups at their o-, m-, p-positions, for the first time in the literature, were synthesized. The absorption capability of these synthesized dyes according to their electron withdrawing and electron donating groups with o-, m- and p-positions was investigated too.

2. Experimental 2.1. Materials and Methods The chemicals utilized in the synthesis were supplied from Aldrich and Merck Chemical Company without any purification. The spectroscopic grade of the used solvents was appropriate. Elemental analysis was implemented using a Costech ECS 4010 analyzer. UV-visible spectrums were procured via a PG T80+ high performance double beam spectrophotometer in

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ACCEPTED MANUSCRIPT the range of varied solvents, i.e. acetonitrile, methanol, DMSO, DMF, acetic acid and chloroform at different concentrations (1x10-6 - 10-8 M). IR spectra were measured via PerkinElmer Spectrum Two (FT-IR) Spectrophotometer. Nuclear magnetic resonance (1H-NMR) spectra were obtained on a Bruker-Spectrospin Avance DPX 400 Ultra-Shield in deuterated dimethylsulphoxide (DMSO-d6) utilizing tetramethylsilane (TMS) as the internal reference and chemical shifts () were reported in ppm. Molecular volume of ten synthesized disperse dyes were calculated utilizing ACD / Chemsketch 12 software programme. 2.2.

Synthesis of the novel heterocyclic disazo disperse dyes Ten different heterocyclic disazo disperse dyes, one without auxochrome group and nine

with –NO2, –Cl, –CH3 auxochrome on para, meta and ortho positions, were synthesized. Dye synthesis is explained in detail in the below section.

Insert Scheme 1 here

Aniline, o-, m-, p-nitroanilines, o-, m-, p-chloroanilines and o-, m-, p-methylanilines were diazotized with 3-aminocrotononitrile and coupled to result in the corresponding 2arylhydrazono-3-ketiminobutyronitriles (1a-1j). After cyclization process of 2-arylhydrazono3-ketiminobutyronitriles (1a-1j) with hydrazine monohydrate, 5-amino-4-arylazo-3-methyl1H-pyrazoles (2a-2j) which were diazotised and coupled with ethyl acetoacetate afforded and a series of ethyl pyrazolylhydrazonoacetoacetates (3a-3j) yielded. Cyclization of these ethyl pyrazolylhydrazonoacetoacetates derivatives (3a-3j) with hydroxylamine afforded disazo dyes 4a-4j (Scheme 1). The precipitated dye was separated by dilution with water, was filtered off and washed in water many times. Subsequently, the product is dried and crystallized from DMF–H2O [30]. 2.2.1. 4-(4'-phenylazo-3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-methylisoxazole (4a):

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ACCEPTED MANUSCRIPT Dark brown crystals; yield 80 %; mp. 265-266 oC (DMF-H2O); IR (KBr):  (cm-1) = 3141 (NH), 3076 (Ar-H), 2923 (Al-H), 3430 (-OH); 1H-NMR (DMSO-d6): δ = 2.61 (3H, pyrazoleCH3), 2.89 (3H, isoxazole-CH3), 7.36-8.01 (5H, Ar-H), 11.85 (-OH), 13.64 (-NH); Anal. Calcd. for C14H13N7O2: C: 54.02, H: 4.21, N: 31.50. Found: C: 54.24, H: 4.13, N: 31.39. Molecular weight: 311 g/mol. 2.2.2. 4-[4'-(p-nitrophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4b): Claret red crystals; yield 70 %; mp. 228-229 oC (DMF-H2O); IR (KBr):  (cm-1) = 3151 (-NH), 3061 (Ar-H), 2925 (Al-H), 3428 (-OH) ; 1H-NMR (DMSO-d6): δ = 2.73 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.47-9.26 (4H, ArH), 12.37 (-OH), 13.23 (NH); Anal. Calcd. for C14H12N8O4: C: 47.19, H: 3.39, N: 31.45. Found: C: 47.33, H: 3.42, N: 31.28. Molecular weight: 356 g/mol. 2.2.3. 4-[4'-(p-chlorophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4c) : Claret red crystals; yield 83 %; mp. 239-240 oC (DMF-H2O); IR (KBr):  (cm-1) = 3168 (-NH), 3074 (Ar-H), 2925 (Al-H), 3414 (-OH); 1H-NMR (DMSO-d6): δ = 2.57 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.38-8.37 (4H, ArH), 11.86 (-OH), 13.56 (NH); Anal. Calcd. for C14H12N7O2Cl: C: 48.63, H: 3.50, N: 28.36. Found: C: 48.56, H: 3.57, N: 28.47. Molecular weight: 345.5 g/mol. 2.2.4. 4-[4'-(p-methylphenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4d) : Red crystals; yield 74 %; mp. 258-259 oC (DMF-H2O); IR (KBr):  (cm-1) = 3133 (-NH), 3064 (Ar-H), 2924 (Al-H), 3451 (-OH); 1H-NMR (DMSO-d6): δ = 2.25 (3H, phenyl-CH3), 2.60 (3H, pyrazole-CH3), 2.90 (3H, isoxazole-CH3), 7.31-7.96 (4H, ArH), 11.95 (-OH), 13.64 (-NH); Anal. Calcd. for C15H15N7O2: C: 55.38, H: 4.65, N: 30.14. Found: C: 55.51, H: 4.70, N: 30.05. Molecular weight: 325 g/mol. 2.2.5. 4-[4'-(m-nitrophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4e) : Claret red crystals; yield 86 %; mp. 260-261 oC (DMF-H2O); IR (KBr):

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ACCEPTED MANUSCRIPT  (cm-1) = 3133 (-NH), 3067 (Ar-H), 2926 (Al-H), 3405 (-OH); 1H-NMR (DMSO-d6): δ = 2.57 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.40-8.11 (4H, ArH), 11.89 (-OH), 13.55 (NH); Anal. Calcd. for C14H12N8O4: C: 47.19, H: 3.39, N: 31.45. Found: C: 47.11, H: 3.42, N: 31.38. Molecular weight: 356 g/mol. 2.2.6. 4-[4'-(m-chlorophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4f) : Claret red crystals; yield 80 %; mp. 263-264 oC (DMF-H2O); IR (KBr):  (cm-1) = 3142 (-NH), 3067 (Ar-H), 2926 (Al-H), 3360 (-OH); 1H-NMR (DMSO-d6): δ = 2.58 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.45-8.94 (4H, ArH), 11.90 (-OH), 13.49 (NH); Anal. Calcd. for C14H12N7O2Cl: C: 48.63, H: 3.50, N: 28.36. Found: C: 48.45, H: 3.41, N: 28.26. Molecular weight: 345.5 g/mol. 2.2.7. 4-[4'-(m-methylphenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4g) : Orange crystals; yield 90 %; mp. 175-176 oC (DMF-H2O); IR (KBr):  (cm-1) = 3186 (-NH), 3073 (Ar-H), 2923 (Al-H), 3408 (-OH); 1H-NMR (DMSO-d6): δ = 2.18 (3H, phenyl-CH3), 2.58 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.01-7.60 (4H, ArH), 11.57 (-OH), 13.30 (-NH); Anal. Calcd. for C15H15N7O2: C: 55.38, H: 4.65, N: 30.14. Found: C: 55.43, H: 4.72, N: 29.98. Molecular weight: 325 g/mol. 2.2.8. 4-[4'-(o-nitrophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4h) : Brown crystals; yield 60 %; mp. 233-234 oC (DMF-H2O); IR (KBr):  (cm-1) = 3181 (-NH), 3091 (Ar-H), 2925 (Al-H), 3424 (-OH) ; 1H-NMR (DMSO-d6): δ = 2.56 (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.44-8.05 (4H, ArH), 11.89 (-OH), 13.51 (NH); Anal. Calcd. for C14H12N8O4: C: 47.19, H: 3.39, N: 31.45. Found: C: 47.07, H: 3.44, N: 31.52. Molecular weight: 356 g/mol. 2.2.9. 4-[4'-(o-chlorophenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4i) : Orange crystals; yield 76 %; mp. 254-255 oC (DMF-H2O); IR (KBr):  (cm-1) = 3192 (-NH), 3059 (Ar-H), 2924 (Al-H), 3435 (-OH) ; 1H-NMR (DMSO-d6): δ = 2.61

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ACCEPTED MANUSCRIPT (3H, pyrazole-CH3), 2.89 (3H, isoxazole-CH3), 7.35-7.96 (4H, ArH), 11.40 (-OH), 13.40 (NH); Anal. Calcd. for C14H12N7O2Cl: C: 48.63, H: 3.50, N: 28.36. Found: C: 48.79, H: 3.54, N: 28.17. Molecular weight: 345.5 g/mol. 2.2.10. 4-[4'-(o-methylphenylazo)-

3'-methyl-1'H-pyrazol-5'-ylazo)-5-hydroxy-3-

methylisoxazole (4j) : Red crystals; yield 84 %; mp. 223-224 oC (DMF-H2O); IR (KBr):  (cm1)

= 3181 (-NH), 3055 (Ar-H), 2924 (Al-H), 3399 (-OH); ; 1H-NMR (DMSO-d6): δ = 2.10 (3H,

phenyl-CH3), 2.59 (3H, pyrazole-CH3), 2.94 (3H, isoxazole-CH3), 7.19-8.24 (4H, ArH), 11.81 (OH), 13.33 (NH); Anal. Calcd. for C15H15N7O2: C: 55.38, H: 4.65, N: 30.14. Found: C: 55.29, H: 4.60, N: 30.26. Molecular weight: 325 g/mol.

3. Results and Discussion 3.1.

Spectral characteristics and tautomerism Synthesized pyrazole and isoxazole disperse dyes 4a-4j could exist in four possible

tautomeric forms, named as disazo-enol form T1, azo-hydrazo-keto form T2, hydrazo-azo-enol form T3 and dishydrazo-keto form T4, displayed in Scheme 2. The FT-IR spectra of 4a-4j dyes exhibited imino (NH) bands at 3133-3186 cm-1 and hydroxyl (O-H) bands at 3360-3451 cm-1. The bands show that these compounds are overwhelmingly in the solid form as one of the disazo-enol (T1) or hydrazo-azo-enol (T3) tautomeric forms. The FT-IR spectra of all dyes prove that the compounds are generally in the enol form in solid state. 1H-NMR

spectra of novel synthesized dyes 4a-4j exhibited one broad peak at 13.23-

13.64 ppm (NH) and one broad peak at 11.40-12.37 ppm (OH). Those outcomes advise that all dyes (4a-4j) are in only one tautomeric form and these tautomeric forms might be disazo-enol (T1) or hydrazo-azo-enol (T3) tautomeric forms in DMSO as shown in Scheme 2. Insert Scheme 2 here Insert Table 1 here

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ACCEPTED MANUSCRIPT 3.2.

Solvent effects on UV-vis. Spectra UV-vis absorption spectra of dyes 4a-4j were obtained in the range of  between 300-

700 nm and summed up in Table 1. The visible absorption spectra of novel synthesized dyes do not correlate with the solvent polarity. Synthesized dyes 4a-4j exhibited one maximum absorption peaks in all utilized solvents, except for 4b and 4e. This means that all dyes except 4b and 4e are present in a single-tautomeric form in all utilized solvents. Dye 4b is present in the mixture of tautomeric forms in solvents DMSO and DMF (Figure 1). Dye 4e is present in the mixture of tautomeric forms in solvent DMF (Figure 2). Insert Figure 1 here Insert Figure 2 here

3.3.

Acid and base influences on UV-visible spectra Acid and base influences on the absorption of synthesized dye solutions were examined

and the outcomes were displayed in Table 2. Insert Table 2 here The absorption spectra of all dyes except 4g (m-CH3) in methanol and chloroform was sensitive to alkali addition (KOH, piperidine, 0.1 M), with max of dyes 4a, 4b, 4c, 4d, 4e, 4f, 4h, 4i and 4j showing bathochromic shifts. These outcomes suggest that dyes 4a, 4b, 4c, 4d, 4e, 4f, 4h, 4i and 4j are present in the transition between tautomeric forms or can be explained by equilibrium. The absorption spectra of dye 4g in alkali methanol and alkali chloroform showed hypochromic shifts. This hypochromic shift can be explained that 4g compounds undergoes tautomeric change in the alkaline medium by comparison in methanol and chloroform solutions and in tautomeric structures given in Scheme 2, it shows that it transforms

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ACCEPTED MANUSCRIPT from one structure to another. The absorption spectra of dye 4b in methanol changed significantly with alkali addition (KOH, 0.1 M) (Figure 3). This result can be explained by the tautomeric structures turned into anionic form with the addition of potassium hydroxide, 0.1 M. The absorption spectra of all dyes except 4g and 4h in methanol were sensitive to acid addition (HCl, 0.1 M), with max of all dyes displaying hypochromic shifts (Table 2). An example of this result is given in Figure 4. These results can be explained by the transition between short and long wavelength tautomeric forms. Insert Figure 3 here Insert Figure 3 here 3.4.

Substituent effects on UV-vis. spectra Compared to other dyes, as it is visible in Table 1, the compound 4b to which the p-NO2

group is substituted, that withdraws electron strongly from the ring, showed bathochromic shift in DMSO and DMF in comparison with chloroform. The compound 4d, substituted with p-CH3 group, provides electron to the ring, showed also bathochromic shift in DMSO and DMF as compound 4b. The 4e and 4h compounds to which electron-providing m-NO2 and o-NO2 groups substituted to the ring, showed bathochromic shift in DMSO and DMF, while there is no clear change in the max of the 4g and 4j compounds to which electron-providing m-CH3 and o-CH3 groups substituted to the ring. This indicates that there is no direct contribution to the substituent effect when the substituents are dependent on the para position, but in particular, as the electron-donating

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ACCEPTED MANUSCRIPT groups approach to the phenyl substituted azo group showed that the compounds contribute to tautomer exchange.

4. Conclusions New heterocyclic disperse disazo dyes containing pyrazole and isoxazole groups were synthesized by a series of synthesis processes. Acid-base, substituent and solvent influence have been studied on the wavelength of maximum absorption. In this research, novel synthesized some disperse disazo pyrazole and isoxazole dyes exhibited solvatochromic effects. While all dyes are one of the single tautomeric forms shown in Scheme 2, 4b in DMSO and DMF, 4e in DMF are thought to be in the form of a mixture of two tautomeric forms. The absorption spectra of all synthesized dyes except 4g (m-CH3) in methanol and chloroform was sensitive to alkali addition (KOH, piperidine, 0.1 M) and showed bathochromic shifts. The absorption spectra of all dyes in acidic methanol (HCl, 0.1 M) showed hypochromic shifts except 4g and 4h. As it is specified in part 3.4, there isn’t any substitution effect seen when the substituents are dependent on the para position when based on the meta and ortho group, it is thought that the components change the structure.

Acknowledgements This study is sponsored and supported by The Scientific and Technological Research Council of Turkey (TUBITAK) with the TUBITAK project number of 109M578.

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polyester fiber, Dye. Pigment. 95.1 (2012) 142-148. https://doi.org/10.1016/j.dyepig.2012.03.014 H. F. Rizk, S. A. İbrahim, M. A. El-Borani, Synthesis, fastness properties, color assessment and antimicrobial activity of some azo reactive dyes having pyrazole moiety, Dye. Pigment. 112 (2015) 86-92. https://doi.org/10.1016/j.dyepig.2014.06.026 S. Y. Alqaradawi, Novel cycloalkane ring-fused arylazopyrazolo [1, 5-a]-pyrimidine derivatives: synthesis, properties and dyeing characteristics, Pigm. Resin. Technol. 32/4 (2003) 248-258. https://doi.org/10.1108/036994203104815 M. H. Helal, Synthesis and characterisation of a new series of pyridinone azo dyes for dyeing of synthetic fibers, Pigm. Resin. Technol. 33/3 (2004) 165-171. https://doi.org/10.1108/036994204105372 A. Deeb, F. Yassine, N. Aouf, W. Shehta, Pyridazine and its related compounds: Part 26.[Synthesis and Application of some Monoazo disperse dyes derived from 3hydrazinopyridazine, Int. J. ChemTech Res. 6(1) (2014) 719-729. http://www.sphinxsai.com/framesphinxsaichemtech.htm G. Hussain, M. Ather, M. U. A. Khan, A. Saeed, R. Saleem, G. Shabir, P. A. Channar, Synthesis and characterization of chromium (III), iron (II), copper (II) complexes of 4amino-1-(p-sulphophenyl)-3-methyl-5-pyrazolone based acid dyes and their applications on leather, Dye. Pigment. 130 (2016) 90-98. https://doi.org/10.1016/j.dyepig.2016.02.014 Y. A. Youssef, M. M. Kamel, M. S. Taher, N. F. Ali, S. A. Abd El Megiede, Synthesis and application of disazo reactive dyes derived from sulfatoethylsulfone pyrazolo [1, 5a] pyrimidine derivatives, J. Saudi Chem. Soc. 18.3 (2014) 220-226. https://doi.org/10.1016/j.jscs.2011.06.015 T. B. Shah, R. S. Shiny, R. B. Dixit, B.C. Dixit, Synthesis and dyeing properties of new disazo disperse dyes for polyester and nylon fabrics, J. Saudi Chem. Soc. 18.6 (2014) 985-992. https://doi.org/10.1016/j.jscs.2011.11.022 Ç. Karabacak, T. Tilki, B. Ö. Tuncer, M. Cengiz, Antimicrobial pyrazole dyes: synthesis, characterization, and absorption characteristics, Res. Chem. Intermed, 41.4 (2015) 19851999. https://doi.org/10.1007/s11164-013-1326-6 E.Aktan, T. Uyar, Hetarylazopyrazolone Dyes Based on Benzothiazole and Benzimidazole Ring Systems: Synthesis, Spectroscopic Investigation and Computational Study, J. Chem. (2017). http://doi.org/10.1155/2017/8659346 M. A. I. Salem, M. I. Marzouk, H. M. Mashaly, Synthesis of pharmacological dyes and their application on synthetic fabrics, Color. Technol. 131.4 (2015) 288-297. https://doi.org/10.1111/cote.12155 S. Malladi, A. M. Isloor, S. Isloor, D. S. Akhila, H. K. Fun, Synthesis, characterization and antibacterial activity of some new pyrazole based Schiff bases, Arab. J. Chem. 6.3 (2013) 335-340. https://doi.org/10.1016/j.arabjc.2011.10.009 A. Çetin, Pirazol türevlerinin sentez metotları, Muş Alparslan Unv. J. Sci. 3(1) (2015) 303-321. S. F. Thakor, D. M. Patel, M. P. Patel, R. G. Patel, Synthesis and antibacterial activity of novel pyrazolo [3, 4-b] quinoline based heterocyclic azo compounds and their dyeing performance, Saudi Pharm. J. 15.1 (2007) 48-54. Y.W. Ho, Synthesis of some new azo pyrazolo[1,5-a] pyrimidine-thieno[2,3-b] pyridine derivatives and their application as disperse dyes, Dyes and Pigments, 64(3) (2005) 223230. https://doi.org/10.1016/j.dyepig.2004.06.007

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ACCEPTED MANUSCRIPT FIGURE LIST

Figure 1. Absorption spectra of synthesized dye 4b in varied solvents

ACCEPTED MANUSCRIPT

Figure 2. Absorption spectra of synthesized dye 4e in varied solvents

ACCEPTED MANUSCRIPT

Figure 3. Dye 4b’s absorption spectra in acidic and basic solvents

ACCEPTED MANUSCRIPT

Figure 4. Dye 4d’s absorption spectra in acidic and basic solvents

ACCEPTED MANUSCRIPT

SCHEME LIST

NC + _ C N2 Cl + H

X

CN

NH2 C CH3

N N H

X

NH

C

N N CH3

(1a-1j)

NH2

X H3C

e, X : m-NO2 f, X : m-Cl g, X : m-CH3

a, X : H b, X : p-NO2 c, X: p-Cl d, X : p-CH3

H2NNH2H2O

C

N

(2a-2j)

h, X : o-NO2 i, X : o-Cl j, X : o-CH3

HO H N

N

X H3C

N

NH2 N

NH

(2a-2j)

1) HCl/AcOH, NaNO2 2) CH3COCH2COOC2H5

N

N N

X H3C

N

NH

COCH3 C

COOC2H5 H NOH 2

NH

N

N

N N

X H3C

N

NH

(4a-4j)

(3a-3j)

Scheme 1. Synthesis of heterocyclic disazo disperse dyestuffs

O

N CH3

ACCEPTED MANUSCRIPT

HO N N

O

N N H3C

NH

N

_

O

(T2)

(T1)

-

KT

HO

H N N

N N

X N

CH3

N N

azo-hydrazo-keto

disazo-enol

H3C

N

X KT

NH

N

O

H CH3

N N

X H3C

O

N

N

hydrazo-azo-enol (T3)

O

KT N CH3

O

H

H

N N

N N

X KT

H3C

N

O

H+

+ H+ N

N N

N N

X H3C

CH3

N

NH

anionic form (A)

N

dishydrazo-keto (T4)

Scheme 2. Tautomeric equilibrium of pyrazole and isoxazole dyes 4a-4j

O

N CH3

ACCEPTED MANUSCRIPT Highlights - A series of novel pyrazole and isoxazole moieties disazo dyes were synthesized. - The solvatochromic properties of these dyes in various solvents were evaluated. - Acid and base effects on λmax of the dyes were also examined in detail.

ACCEPTED MANUSCRIPT

TABLE LIST Table 1. Solvent effect on max (nm) of synthesized dyes 4a-4j Dye No. 4a

DMSO

DMF

Acetonitrile

Methanol

Acetic acid

Chloroform

454

459

416

416

413

431

4b

474, 574 (s)

471, 573 (s)

458

457

454

461

4c

450

460

422

428

416

436

4d

454

454

427

441

425

436

4e

448

466, 481 (s)

416

438

416

435

4f

442

458

429

449

426

441

4g

422

420

406

408

407

411

4h

444

496

430

344

424

431

4i

459

460

434

446

432

446

4j

435

437

404

412

405

436

s: shoulder

ACCEPTED MANUSCRIPT

Table 2. Absorption maximum values of synthesized dyes 4a-4j in acidic and basic solvents max(nm)

Dye No. Methanol

Methanol + KOH

Methanol + HCl

Chloroform

Chloroform + Piperidine

Acetic Acid

4a

416

456

385

431

470

413

4b

457

536

454

461

536

454

4c

428

461

406

436

448

416

4d

441

460

410

436

466

425

4e

438

457

398

435

478

416

4f

449

448

398

441

486

426

4g

408

387

416

411

344

407

4h

344

482

426

461

489

424

4i

446

468

399

446

487

432

4j

412

458

398

436

469

405