Synthesis of bis-azobenzene derivatives with reactive bromohexyl unit and carboxylic acid group based on Disperse Yellow 7 European Journal of Chemistry 11 (4) (2020) 298-303 European Journal of Chemistry ISSN 2153-2249 (Print) / ISSN 2153-2257 (Online) – Copyright © 2020 The Authors – Atlanta Publishing House LLC – Printed in the USA. This work is published and licensed by Atlanta Publishing House LLC – CC BY NC – Some Rights Reserved. http://dx.doi.org/10.5155/eurjchem.11.4.298-303.2032 European Journal of Chemistry View Journal Online View Article Online Synthesis of bis-azobenzene derivatives with reactive bromohexyl unit and carboxylic acid group based on Disperse Yellow 7 Alina Madalina Darabut 1, Olha Hennadiivna Purikova 2 and Yevheniia Volodymyrivna Lobko 1,* 1 Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague, 18000, Czech Republic alinadarabut@gmail.com (A.M.D.), lobkoeugenia@gmail.com (Y.V.L.) 2 Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, Kharkivske shosse 48, Kyiv, 02160, Ukraine olhapurikova@gmail.com (O.H.P.) * Corresponding author at: Department of Surface and Plasma Science, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, Prague, 18000, Czech Republic. e-mail: yevheniia.lobko@mff.cuni.cz (Y.V. Lobko). 10.5155/eurjchem.11.4.298-303.2032 Received: 21 August 2020 Received in revised form: 02 October 2020 Accepted: 03 October 2020 Published online: 31 December 2020 Printed: 31 December 2020 In this work, two types of azobenzene derivatives based on Disperse Yellow 7 (DY7, 4-[4- (phenylazo)phenylazo]-o-cresol) were synthesized, which are bis-azobenzenes bearing flexible functional 6-bromohexyl chain or carboxylic acid moiety. The first one was synthesized by alkylation of DY7 with an excess of 1,6-dibromohexane in the presence of a mild base (K2CO3). The second one (azo dye with carboxylic acid functionality) was obtained by the alkaline hydrolysis of the ester bond of the newly obtained DY7 derivative with the ethoxycarbonyl group. The synthesized compounds were characterized by different spectral analytical techniques such as 1H NMR, 13C NMR, FT-IR, and UV-Vis. They can be employed for the synthesis of a wide variety of azo-based materials, which may be suitable for photochromic systems and molecular electronics applications. Dyes Alkylations Azobenzene Bromohexyl unit Carboxylic acids Photo-regulation Cite this: Eur. J. Chem. 2020, 11(4), 298-303 Journal website: www.eurjchem.com 1. Introduction Azobenzene-based compounds have been targeted as crucial building blocks of numerous functional smart materials such as photoresponsive molecular switches, molecular shut- les, data storage devices, sensors, nonlinear optical systems, and liquid crystals [1-5]. Azobenzenes (AB) are switchable compounds that exhibit reversible E-Z (trans-cis) photoisome- rization. Photoisomerization from a cis- (Z-form) to a trans- (E- form) conformation is reversible by photochemical and thermal pathways [6,7]. It is essential that the isomerization of azobenzene units proceeds with a large structural change that affects the dipole moment and geometry (Figure 1a). Thus, azobenzene derivatives can exhibit a photomechanical effect in bulk materials [8-11]. Note that most of the reported azobenzene-containing compounds have only non-conjugated AB units (mono-AB). The different AB derivatives can exist in Z-state for many hours in the dark [6,12]. At the same time, irradiation of photochromic components containing two (or more) AB units leads to a mixture of three isomers E/E, E/Z, and Z/Z at the photostationary state (Figure 1b) [13,14]. Next, systems with multi-AB groups back-isomerize instantaneously [15]. Typically, the organic azo-based chromophores have been incorporated into a polymer backbone (via both covalent and noncovalent binding), the polyhedral oligomeric silsesquioxane core, and others silica-based particles that have better process- ability and optical properties (i.e. reduced chromophore aggregation) than small molecules [3,12,16-18]. Importantly, that besides photoisomerization, the formation of surface relief gratings in the films, photoinduced orientation, photoactuation are also possible in AB-functionalized polymers [12]. By increasing the number of photochromic groups in bis-AB, such as Disperse Yellow 7 (DY7, 4-[4-(phenylazo)phenylazo]-o- cresol), it is possible to achieve higher and more stable photo- induced birefringence than the corresponding mono-azo- functionalized systems [15,19,20]. Thus, bis-AB-based mate- rials are preferable for photoorientation. Moreover, a high degree of conjugation in para-substituted bis-AB allows conduc- tance, which can be precisely regulated by fast and reversible ABSTRACT RESEARCH ARTICLE KEYWORDS http://dx.doi.org/10.5155/eurjchem.11.4.298-303.2032 http://www.eurjchem.com/ http://dx.doi.org/10.5155/eurjchem.11.4.298-303.2032 mailto:alinadarabut@gmail.com mailto:lobkoeugenia@gmail.com mailto:olhapurikova@gmail.com mailto:yevheniia.lobko@mff.cuni.cz http://www.eurjchem.com/ https://crossmark.crossref.org/dialog/?doi=10.5155/eurjchem.11.4.298-303.2032&domain=pdf&date_stamp=2020-12-31 Darabut et al. / European Journal of Chemistry 11 (4) (2020) 298-303 299 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.298-303.2032 N N 9Å N N 5.5Å UV Vis / Thermal E Z D=0 D=3.5 (a) N N NN N N NN N N NN E E E Z Z Z UV UV (b) Figure 1. Photochemical isomerization of mono-azobenzene (a) and bis-azobenzene (b) with conjugated AB units derivatives. The trans (E)- and cis (Z)-forms are very different in shape, size, and polarity (D - Dipole moment). light-induced switching [21]. Next, liquid crystal molecules were prepared based on bis-AB having alkyl moieties [22] as well as, for example, bis-AB dyes were applied as cross-linkers for photocontrol of peptide structure [23]. Thus, the synthesis of new chromophores containing π-conjugated para-azo- benzene units and an appropriate functional group for further synthetic manipulation (attachment/functionalization) is crucial for the development of new azo-based structures with extensive and versatile applications. In this context, flexible bromohexyl unit and highly polar carboxylic acid group are promising functional moieties. Since bromoalkylated azo dyes, these compounds are widely used for directly incorporating azo chromophore groups into the side chains of polymers [24] or as substrates for subsequent organic transformation [25]. The carboxylic functions are the principal groups employed in organic building blocks [26]. The presence of COOH groups not only allows further conjugation of the corresponding dyes with different scaffolds, but they, thanks to their strong and highly directional H-bonding, are extremely important in the supra- molecular chemistry [27]. The supramolecular strategy may simplify the route for the preparation of azo materials since such materials can be prepared by non-covalently introducing AB groups into the medium [12]. Therefore, the development of synthetic routes for the preparation of new reactive bis-AB chromophores is significant importance. To the best of our knowledge, the bis-azobenzene derivatives based on DY7, containing a flexible functional 6- bromohexyl chain or aliphatic carboxylic acid moiety have not been reported yet. Hence, the current work represents an approach to the design of a reactive bis-azobenzene dye possessing a flexible alkyl chain with reactive bromine as well as bis-azobenzene containing a functional acetic acid fragment. 2. Experimental 2.1. Materials and measurements Disperse Yellow 7 (95%), 1,6-dibromohexane (96%), ethyl chloroacetate (99%) were purchased from Sigma-Aldrich and used as received. The other reagents and solvents were purified by well-established techniques. NMR spectra were recorded on a Bruker Avance DRX 500 MHz spectrometer at room temperature in deuterated solvents CDCl3 or DMSO-d6. Chemical shifts are reported relative to chloroform (δ = 7.25 ppm for 1Н NMR and δ = 77.00 ppm for 13С NMR) or DMSO-d6 (δ = 2.50 ppm for 1Н NMR). Fourier transform infrared (FT-IR) spectra (4000-400 сm-1) of synthesized compounds were recorded on a TENSOR 37 spectrometer using KBr pellets. The UV/Vis spectra were recorded on Shimadzu UV-2450 spectrophotometer. 2.2. Azo dyes synthesis 2.2.1. Synthesis of 1-(4-((6-bromohexyl)oxy)-3-methyl phenyl)-2-(4-(phenyldiazenyl)phenyl)diazene (2) A 50 cm3 three-necked flask equipped with an oil bath, a mechanical stirrer, a cold-water condenser, an argon inlet/outlet, and a thermometer was charged with compound DY7 (Dye 1, 4-[4-(phenylazo)phenylazo]-o-cresol) (1.00 g, 3.16 mmol), 6-dibromohexane (3.85 g, 15.8 mmol), potassium carbonate (0.66 g, 4.74 mmol) and acetone (15 cm3). The mixture was stirred and heated under reflux for 24 h. Then, the mixture was cooled to room temperature and the inorganic salt was removed via filtration. The filtrate poured dropwise into ice water to precipitate the product. The resulting orange solid was purified by precipitation from chloroform solution into hexane (Scheme 1). Yield: 75%. M.p.: 89-92 °C. 1H NMR (CDCl3, 500 MHz, δ, ppm): 1.55 (s, 4H, -СН2-), 1.87-1.93 (m, 4H, -СН2-), 2.31 (s, 3H, -CH3), 3.43 (t, 2H, J1 = 6.7, J2 = 7.1 Hz, -CH2-), 4.07 (t, 2H, J1 = 5.8, J2 = 6.2 Hz, -CH2-), 6.93 (d, 1Н, J = 8.3 Hz, Ph), 7.48- 7.55 (m, 3Н, Ph), 7.81-7.84 (m, 2Н, Ph), 7.95 (d, 2Н, J = 8.3 Hz, Ph), 8.00-8.06 (m, 4Н, Ph). 13С NMR (CDCl3, 125 MHz, δ, ppm): 16.41 (-CH3), 25.76, 28.17, 29.09 (-CH2-), 38.93 (-CH2Br), 68.06 (-OCH2-), 110.46, 122.98, 123.32, 123.73, 123.80, 124.57 (Ar- C),127.63 (C-CH3), 129.09, 131.21 (Ar-C), 146.50, 152.70, 153.13, 153.98 (Ar-C-N), 160.26 (Ar-C-O). 300 Darabut et al. / European Journal of Chemistry 11 (4) (2020) 298-303 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.298-303.2032 Scheme 1 FT-IR (KBr, ν, cm-1): 2850-3050 (CH), 1601, 1499 (C=Carom), 1250 (C-O-C), 1144 (C-O), 648 (C-Br). UV/vis (CHCl3, λmax, nm): 385. 2.2.2. Synthesis of ethyl 2-(2-methyl-4-((4-(phenyldiazenyl) phenyl)diazenyl)phenoxy)acetate (3) A 50 cm3 three-necked flask equipped with an oil bath, a mechanical stirrer, a cold-water condenser, an argon inlet/outlet, and a thermometer was charged with dye 1 (1.00 g, 3.16 mmol), ethyl chloroacetate (0.58 g, 4.74 mmol), potassium carbonate (0.66 g, 4.74 mmol) and acetone (12 cm3). The mixture was stirred and heated under reflux for 24 h and filtered. The filtrate was poured into ice-cold water. The separated ester was extracted with ether and dried over anhydrous magnesium sulfate. Excess ether was removed by distillation, and the remaining crude ester was used to prepare the corresponding carboxylic acid 4 (Scheme 1). Yield: 80%. M.p.: 139-142 °C. 1H NMR (CDCl3, 500 MHz, δ, ppm): 1.31 (t, 3H, -CH3), 2.39 (s, 3H, Ar-CH3), 4.29 (q, 2H, J= 7.1 Hz, -COOCH2-), 4.73 (s, 2H, -OCH2CO-), 6.82 (d, 1Н, J = 7.9 Hz, Ar-H), 7.49-7.55 (m, 3Н, Ar-H), 7.79-7.82 (m, 2Н, Ar-H), 7.95 (d, 2Н, J = 7.5 Hz, Ar-H), 8.00-8.06 (m, 4Н, Ph). FT-IR (KBr, ν, cm-1): 2850-3060 (CH), 1728 (C=O), 1597, 1491 (C=Carom), 1248 (C-O-C), 1109 (C- O), 1032 (O-C-C). UV/vis (CHCl3, λmax, nm): 387. 2.2.3. Synthesis of 2-(2-methyl-4-((4-(phenyldiazenyl) phenyl)diazenyl)phenoxy)acetic acid (4) A mixture of dye 3 (1.00 g, 2.48 mmol), 20 wt% KOH aqueous solution (15 cm3) and ethanol (20 cm3) was reflux for 2 h. The mixture was then poured into HCl (1 N, 50 cm3) with stirring. The product was filtered, then washed with water and purified by boiling out with ethanol (Scheme 1). Yield: 90%. M.p.: ˃200 °C. 1H NMR (DMSO-d6, 500 MHz, δ, ppm): 2.30 (s, 3H, Ar-CH3), 4.85 (s, 2H, -CH2-), 7.06 (d, 1Н, J = 7.8 Hz, Ar-H), 7.59- 7.62 (m, 3Н, Ar-H), 7.80-7.82 (m, 2Н, Ar-H), 7.93 (d, 2Н, J = 6.2 Hz, Ar-H), 8.02-8.08 (m, 4Н, Ar-H). FT-IR (KBr, ν, cm-1): 2500- 3300 (OH), 2850-3060 (CH), 1745 (C=O), 1597, 1489 (C=Carom), 1248 (C-O-C), 1113 (C-O). UV/vis (CHCl3, λmax, nm): 387. 3. Results and discussion A broader application of bis-AB-functionalized materials depends on the successful synthesis of new bis-AB-based chromophores with highly reactive groups. For the synthesis of bis-azo-containing dyes with reactive bromohexyl unit and carboxylic acid group, commercially available DY7 (dye 1) was chosen as the initial precursor (Scheme 1). The attachment of the bromohexyl substituent into the structure of DY7 was achieved by the reaction of a 5-fold excess of 1,6-dibromohexane with dye 1 in the presence of K2CO3 in acetone. The excess of the 1,6-dibromohexane was used to ensure the formation of the mono-substitution product 2 [28]. The developed method of synthesis of dye 4 containing the carboxylic group is based on etherification of compound 1 with ethyl chloroacetate followed by the alkaline hydrolysis of the ester group of the newly obtained scaffold 3. The hydrolysis was performed in ethyl alcohol-water solvent. Importantly, that compounds with aliphatic carboxylic acid-based units are more reactive than compounds with aromatic carboxylic acid-based units [29]. This might facilitate the later conjugation of the obtained dye 4 with polymers or other scaffolds in subsequent applications. The yield of products was 75-90%. The bis-AB dyes 2, 3 and 4 are orange or brown in color. The dyes 2 and 3 are readily soluble in common organic solvents such as CHCl3, tetra- hydrofuran, dimethylformamide (DMF), dimethylacetamide (DMAc) and dimethyl sulfoxide (DMSO). The azo dye 4, due to the presence in its structure of the highly polar carboxylic acid group, is soluble only in polar aprotic solvents such as DMF, DMAc and DMSO. The 1H NМR spectra of the synthesized dyes 2, 3, and 4 correspond to the proposed structures (Figures 2- 4). The conjugation of bromohexyl substituent to DY7 was confirmed by the presence of both sets of signals from the corresponding AB fragment (the resonance peaks from aromatic protons in the range δ 6.9-8.0 ppm as well as a singlet at δ 2.31 ppm for the methyl group) and alkyl unit (four methylene proton signals in the range of δ 1.5 to 4.1 ppm) (Figure 2). Note that the signal from central -CH2- (protons a in Figure 2) at δ ~1.55 ppm of the alkyl group overlaps with the signal given by the trace water in deuterated chloroform. Next, the ethyl proton signals at δ 1.31 and 4.28 ppm (Figure 3), originating from the ethoxycarbonyl group of dye 3, fully disappeared after alkaline hydrolysis of the ester bond in the 1H NMR spectrum of carboxylic acid derivative 4, as shown in Figure 4. The COOH signal of dye 4 is not seen because of the exchange of the OH protons with at least protons of the residual water in DMSO-d6 solution. Similar to the 1H NMR spectrum of dye 2, peaks due to the AB fragment of DY7 were also observed in the 1H NMR spectra of dyes 3 and 4. Overall, the chemical shifts and peak integrations of all the protons in the azo chromophores are in excellent agreement with their expected structures. The excellent solubility in the organic solvents of azo dye 2 with alkyl chain and reactive bromine makes it possible additionally to investigate the structure of the dye by 13C NMR spectroscopy (Figure 5). The corresponding 13C NMR spectrum of bis-AB 2 indicated that the hydrogen atom from the hydroxyl group of the initial dye 1 was substituted by the alkyl chain such as the 6-bromhexyl unit. The structures of the prepared bis-AB dyes were further confirmed by FT-IR spectroscopy (Figure 6). Darabut et al. / European Journal of Chemistry 11 (4) (2020) 298-303 301 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.298-303.2032 N N N N O Br CH3 8 7 6 5 4 3 2 Chemical Shift (ppm) 6.39 4.883.953.30 2.862.002.001.00 Chloroform-d 1. 55 1. 87 1. 93 2. 31 3. 43 4. 07 6. 94 7. 48 7. 55 7. 817. 94 8. 02 8. 04 b d e fg hi j a+H2O c a ab b c d e f g g h h g j j i i 2.16 Figure 2. 1H NMR spectrum of azo dye 2. N N N N O O O CH3 CH3 8 7 6 5 4 3 2 1 Chemical Shift (ppm) 6.35 3.32 3.00 2.942.061.991.00 Chloroform-d 1. 31 2. 39 4. 28 4. 73 6. 83 7. 51 7. 80 7. 82 7. 94 8. 02 a b c d e a b c d e f g h i f f f g gh h i i H2O 2.10 Figure 3. 1H NMR spectrum of azo dye 3. 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 Chemical Shift (ppm) 4.00 3.34 3.001.95 1.890.96 DMSO-d6 8. 06 8. 04 7. 93 7. 80 7. 62 7. 59 7. 06 4. 85 2. 30 a b c d H2O ef g f N N N N O OH OCH3 a bc d d d e ef g g Figure 4. 1H NMR spectrum of azo dye 4. The FT-IR spectra of all dyes show the characteristic absorptions in the regions 1248-1250, 1489-1601 (at least two bands in each spectrum in this region) and 2800-3100 cm-1, which correspond to C-O-C, С=Сarom and CH groups [30,31]. The absence of intense bands of ethyl groups connected with oxygen (-O-C-C) of the ester intermediate 3 in the FT-IR spectrum of the obtained dye 4 at the 1032 cm–1 indicates that these groups have been removed during the hydrolysis reaction. According to Figure 6, the comparison between the two spectra of dye 3 and dye 4 shows a chemical shift at a wavelength of 1728 cm-1, which refers to C=O group in ester-based dye 3 to a wavelength of 1745 cm-1 of C=O group in acid-based dye 4. The FT-IR spectrum of dye 4 also has a very broadband with a developed structure (due to the overlap with CH absorption bands) in the region 3300-2500 cm-1. This band is associated with OH stretching vibrations of COOH group. 302 Darabut et al. / European Journal of Chemistry 11 (4) (2020) 298-303 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.298-303.2032 140 120 100 80 60 40 20 Chemical Shift (ppm) Chloroform-d 16 .4 125 .7 6 28 .1 7 29 .0 9 38 .9 3 68 .0 6 11 0. 46 12 2. 98 12 3. 32 12 3. 73 12 7. 63 12 9. 09 13 1. 21 14 6. 50 15 2. 70 15 3. 13 15 3. 98 16 0. 26 N N N N O CH3 Br 124.5 124.0 123.5 123.0 Chemical Shift (ppm) 12 2. 9812 3. 32 12 3. 73 12 3. 80 12 4. 57 1 2 8 7 9 4 3 56 10 1112 13 14 1516 17 18 19 20 1 2 34 4 5 6 7 8 9 10 11 12 13 14 15 16 17 1918 20 Figure 5. 13C NMR spectrum of azo dye 2. Figure 6. FT-IR spectra of azo dyes 2, 3 and 4. Figure 7. UV/Vis absorbance spectra of azo dyes 2, 3 and 4 in CHCl3. The great breadth of this band resulting from the intramolecular and intermolecular hydrogen bond interactions of dye 4 with carboxylic acid functionality [32]. Figure 7 presents the UV-visible spectra of dyes 2, 3, and 4 in CHCl3. The spectra of these bis-AB chromophores show absorption maxima, corresponding to the π-π* transition, at about 387 nm, being red-shifted ∼40 nm as compared to the Darabut et al. / European Journal of Chemistry 11 (4) (2020) 298-303 303 2020 – European Journal of Chemistry – CC BY NC – DOI: 10.5155/eurjchem.11.4.298-303.2032 absorption maximum of mono-azobenzene dyes with similar structures. Thus, mainly, mono-azobenzene dyes have a typical azobenzene absorbance with a strong π-π* band at 348 nm and a weaker n-π* transition at around 430 nm [25,33]. The n-π* transition for azo dyes 2, 3, and 4 appears as a shoulder of a main peak at around 470 nm (Figure 7). Overall, the structural design of the bis-azobenzenes 3 and 4 extends the possibility of using such compounds to build up functional azobenzene-based polymer systems. The detailed synthesis and properties of different azo-containing systems based on the obtained bis-AB chromophores will be reported in due course. 4. Conclusion In summary, the Br-terminated bis-azobenzene dyes comp- rising flexible hexenyloxy fragments as well as bis-azobenzene with COOH functionality were synthesized. For the synthesis of dye with the carboxylic acid group, bis-azobenzene interme- diate with the ethoxycarbonyl moieties was firstly obtained. All dyes were synthesized from commercially available Disperse Yellow 7 possessing the π-conjugation between the two AB units. The structures of the synthesized compounds were indicated by FT-IR, 1H and 13C NMR, and UV/vis spectrometry techniques. The presence of functional groups and bis-AB functionality in such chromophores opens the possibility of their further chemical modification and their use in macro- molecular and supramolecular chemistry for the synthesis of a wide range of new photochromic materials with targeted optical properties. Disclosure statement Conflict of interests: The authors declare that they have no conflict of interest. Author contributions: All authors contributed equally to this work. Ethical approval: All ethical guidelines have been adhered. Sample availability: Samples of the compounds are available from the author. ORCID Alina Madalina Darabut http://orcid.org/0000-0002-1595-6094 Olha Hennadiivna Purikova http://orcid.org/0000-0002-4606-8815 Yevheniia Volodymyrivna Lobko http://orcid.org/0000-0003-1796-7691 References [1]. Merino, E. Chem. Soc. Rev. 2011, 40, 3835-3853. [2]. Beharry, A. A.; Woolley, G. A. Chem. Soc. Rev. 2011, 40, 4422-4437. [3]. Fihey, A.; Perrier, A.; Browne, W. 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Dyes Pigments 2016, 132, 7-19. [30]. Tkachenko, I. M.; Belov, N. A.; Kobzar, Ya. L.; Dorokhin, A. V.; Shekera, O. V.; Shantarovich, V. P.; Bekeshev V. G.; Shevchenko, V. V. J. Fluorine Chem. 2017, 195, 1-12. [31]. Yazici, A.; Dalbul, N.; Salih, B. J. Chem. Soc. Pakistan 2014, 36, 707-711. [32]. Abdulla, H. A.; Minor, E. C.; Dias, R. F.; Hatcher, P. G. Geochim. Cosmochim. Acta 2010, 74, 3815-3838. [33]. Ledin, P. A.; Tkachenko, I. M.; Xu, W.; Choi, I.; Shevchenko, V. V.; Tsukruk, V. V. Langmuir 2014, 30, 8856-8865. Copyright © 2020 by Authors. This work is published and licensed by Atlanta Publishing House LLC, Atlanta, GA, USA. The full terms of this license are available at http://www.eurjchem.com/index.php/eurjchem/pages/view/terms and incorporate the Creative Commons Attribution-Non Commercial (CC BY NC) (International, v4.0) License (http://creativecommons.org/licenses/by-nc/4.0). By accessing the work, you hereby accept the Terms. This is an open access article distributed under the terms and conditions of the CC BY NC License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited without any further permission from Atlanta Publishing House LLC (European Journal of Chemistry). No use, distribution or reproduction is permitted which does not comply with these terms. Permissions for commercial use of this work beyond the scope of the License (http://www.eurjchem.com/index.php/eurjchem/pages/view/terms) are administered by Atlanta Publishing House LLC (European Journal of Chemistry). http://orcid.org/0000-0002-1595-6094 http://orcid.org/0000-0002-4606-8815 http://orcid.org/0000-0003-1796-7691 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms http://creativecommons.org/licenses/by-nc/4.0 http://www.eurjchem.com/index.php/eurjchem/pages/view/terms 1. Introduction 2.1. Materials and measurements 2.2. Azo dyes synthesis 2.2.1. Synthesis of 1-(4-((6-bromohexyl)oxy)-3-methyl phenyl)-2-(4-(phenyldiazenyl)phenyl)diazene (2) 2.2.2. Synthesis of ethyl 2-(2-methyl-4-((4-(phenyldiazenyl) phenyl)diazenyl)phenoxy)acetate (3) 2.2.3. Synthesis of 2-(2-methyl-4-((4-(phenyldiazenyl) phenyl)diazenyl)phenoxy)acetic acid (4) 3. Results and discussion 4. Conclusion Disclosure statement ORCID References PrintField10: PrintField11: PrintField12: PrintField13: PrintField14: PrintField15: PrintField20: PrintField21: PrintField22: PrintField23: PrintField24: PrintField25: