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Photostable coumarin containing azo dyes with multifunctional property
Dyes and Pigments 163 (2019) 692–699
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Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Photostable coumarin containing azo dyes with multifunctional property Nitesh N. Ayare, Supriya H. Ramugade, Nagaiyan Sekar
T
∗
Dyestuff Technology Department, Institute of Chemical Technology, N. P. Marg, Matunga, Mumbai, 400019, Maharashtra, India
ARTICLE INFO
ABSTRACT
Keywords: Coumarin-azo dyes Fastness property UPF Antimicrobial activity HOMO-LUMO gap Global reactivity descriptors
A series five coumarin azo disperse dyes with thiophene bridge are synthesized using diazotized aniline derivatives which are confirmed by FT-IR, 1H NMR, 13C NMR, and CHN analysis. The dyes are applied on polyester and nylon material. The multifunctional properties (lightfastness, washing fastness, sublimation fastness, K/S, UPF, and antimicrobial activity) of the dyed fabric are determined. The dye 3a (-NO2) show red shifted absorption (649 nm) and blocking 95.5–97.4% of UV radiations with 96% antimicrobial property. The geometries of all the azo dyes are optimized using Density Functional Theory (DFT). The Global Reactivity Descriptors (GRD) are evaluated at the same method of theory. The GRD obtained shows a linear relation with lightfastness and UPF ratings. The antimicrobial activity of all synthesized dyes are determined by AATCC 100 test method and it is correlated with the HOMO-LUMO energy band gap.
1. Introduction The fundamental function of textile fabric is to cover and protect the human body from harmful ultraviolet (UV) rays, microbes, and bacteria [1,2]. It is reported that a fabric made from yarn fulfil the basic function of protecting the human skin through the multifunctional properties [2]. The multifunctional properties include antimicrobial, UV protective, moisture control, and other comfort properties [2]. The natural dyes extracted from neem, turmeric, marigold, onion, annatto plant, Eclipta show antimicrobial and ultraviolet protective properties [3,4]. But natural dyes exhibit inherent drawbacks like poor tinctorial strength, inferior light fastness properties, and use of metallic mordants generates serious problems affecting the environment [5,6]. Therefore, the natural dyes are preferred over synthetic dyes in niche areas. Majority of natural dyes contain chromones, flavonoids, and coumarin core which exhibit the antimicrobial and ultraviolet protective property [4,7,8]. Numerous natural products contain coumarins and heterocyclic moieties which possess medicinal properties [9,10]. Dyes containing heterocyclic units are commonly used as an additive in foods, cosmetics, pharmaceuticals and in optical brighteners [10]. Thiophene is an important heterocyclic system in dyes as it leads to better dyeability and intrinsic conjugation of electrons which causes charge tranfer (CT) [11]. It also enhances the antimicrobial activity, sublimation fastness property, and tinctorial strength [12]. Incorporation of the electron withdrawing group (EWG) brings photostability which intensifies light fastness property [13]. Therefore, the overall significance of synthetic
∗
azo dyes is excellent tinctorial strength, with brighter dyeing and fastness property [6,14]. The above benefits motivated us to synthesize coumarin azo dyes with thiophene bridge, and the structure of the dyes synthesized are given in Fig. 2. The disperse dyes are applied on nylon and polyester and materials. The fastness property, K/S values, Ultraviolet protection factor (UPF) and the antimicrobial activity are evaluated using different test methods. The experimental findings are correlated with the computational method by using Density functional theory (DFT). 2. Experimental 2.1. Materials 2.1.1. Chemicals p-Toluidine, p-cynoaniline, p-chloroaniline, p-nitroaniline, p-methoxyaniline and, sodium carbonate, sodium nitrate (NaNO2), HCl (33%), acetic acid, N,N-diethyl meta amino phenol (DEMAP) aldehyde, malononitrile, sulphur (S8) were bought from Spectrochem chemicals Ltd, Mumbai, India. Solid chemicals used are confirmed by melting point. Liquid chemicals are purified by distillation, confirmed by taking their boiling points and then used. Required solvents are purified according to standard protocol. 2.1.2. Substrate and measurement Nylon and 100% polyester fabrics were purchased from the local manufacturer (Piyush Syndicate yarn merchant and commission agent).
Corresponding author. E-mail addresses: [email protected], [email protected] (N. Sekar).
https://doi.org/10.1016/j.dyepig.2018.12.050 Received 2 October 2018; Received in revised form 21 December 2018; Accepted 21 December 2018 Available online 29 December 2018 0143-7208/ © 2018 Elsevier Ltd. All rights reserved.
Dyes and Pigments 163 (2019) 692–699
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Perkin Elmer spectrophotometer with 1 cm quartz cells is used to record UV visible spectra of the titled dyes. The dyes of 10 μM are taken for UV visible study. The progress of reactions are examined by Thin layer chromatography (TLC) technique (60 F254) Merck, India. Purification of all compounds is attained by recrystallization. The coupler, 2-amino-4-(7-diethylamino)-2-oxo-2H-chromen-3-yl) thiophene-3-carbonitrile 3 is synthesized as described earlier [15]. “Melting points are noted on the instrument, Sunder Industrial Product, India. Jasco 4100”. The IR bands of the synthesized dyes are recorded on Fourier Transform IR (FT-IR) instrument. Agilent 400 MHz, 500 MHz and 800 MHz Bruker NMR instrument with tetramethylsilane (TMS) as the internal standard was used to record 1H NMR and 13C NMR spectra. CDCl3 and DMSO-d6 solvents used for sample preparation. Shimadzu Labsolution instrument with averaged ESI positive+ was used to analyse the mass of titled dyes.
were subjected on sublimation plate's fastness analyzer at different temperatures (150 °C, 180 °C, 210 °C) for 30 s. Further, the staining on the undyed fabric was checked and compared with standard Greyscale [16]. 2.2.3. Ultraviolet protection factor (UPF) Protection of skin from harmful UV radiation is done by textile fabric because the textile fabric can absorb, reflect and scatter UV radiation. The applied five dyed fabric need to have appreciable quantities of these protective agents to fulfill UV protection [5,17]. The table mentioned below is a sorting scheme for UPF ratings published in 1996, it is a standard for classification and determination of sun protective clothing (AS/NZ 4399) sourced by Australian and New Zealand which considered as a standard by industries as well [5,17] (see Table 1). 2.2.4. Antimicrobial activity With a view to protecting human skin from microbes, the textile fabric is imparted with the synthesized dyes, the antimicrobial activity was deduced using agar well diffusion method and quantitively effective antimicrobial activity are assessed using standard AATCC 100 test method [18].
2.1.3. Application of coumarin azo disperse dye The disperse azo dyes are applied on 100% polyester and nylon fabric through an aqueous medium. For dyeing of polyester, 2% shade and material to liquor ratio were kept at 1:30 with dyeing machine temperature at 130 °C for 45 min. The pH of dye bath was maintained between 4 and 5 using glacial acetic acid. Levelling agent, dispersing agent used were Supergen KDF and Saracen SO respectively, later the dyed fabric was introduced to reduction clearing treatment in 2 g/l solution of sodium hydrosulfite and NaOH at 70 °C for 20 min”. The dyed fabrics are finally rinsed, washed with cold water and dried [5,27]. “The nylon material is dyed using rota dyer machine at 100 °C for 60 min keeping the % shade, MLR ratio and pH similar to that of polyester dyeing”. The dyed nylon material obtained is washed followed by soaping and dried [5].
2.3. Computational fine points All the quantum chemical computations are preformed on Gaussian 09 program [19], while outcomes are visualized with Gauss View 5.0. All the dyes structure are optimized at ground state (S0) in the gas phase using Density Functional Theory (DFT). The hybrid function B3LYP used which is a combination of Becke's three parameter exchange functional (B3) [20] with the nonlocal correlation functional by Lee, Yang, and Parr (LYP) [21]. The energy band gap i.e. (HOMO – LUMO) and the global reactivity descriptors of the azo dyes are evaluated using the hybrid functional B3LYP and triple zeta basis set with both the diffuse function, 6–311++g(d,p) [22].
2.2. Methods 2.2.1. Assessment of colour The assessment of dyed fabric was done by using Spectrascan 5100 + instrument. The assessment was done on the basis of color space values (L*, a* and b*) and tinctorial strength in terms of K/S. L* represent brightness, a* represents red – green coordinate, b* represents yellow – blue coordinate. By assembling the above three, we conclude the tonal change of applied dye on fabric. The Rayscan Spectrascan 5100 + equipped with reflectance accessories is used to determine the absorbance of dyed fabric. The K/S values is evaluated using equation (1);
(1 R)2 K = S 2R
3. Synthesis 3.1. The general protocol of diazotization One of the substituted aromatic amines 1a -1e (0.1 g, 0.007 mol) is taken in water and acetic acid mixture. Conc. HCl (0.14 mol, 2.19 g, d = 1.1 gmL−1, 5.6 mL of 30% HCl) added to get either a clear solution or dispersion depending upon the amine used. Then the reaction mixture is cooled to 0-5 °C. 0.065 g, (0.0009mol) NaNO2 was dissolved in water (3 ml), and the resulting solution was added to the mixture slowly within 15 min. The reaction mixture is stirred for an hour at 0-5 °C. Completion of diazotization is checked using starch-iodide paper. The excess of nitrous acid present is quenched by adding 0.01 g of urea [23].
(1)
where R = Reflectance at complete opacity.S = Scattering coefficient.K = Absorption coefficient.
3.2. Coupling procedure
2.2.2. Fastness property 2.2.2.1. Lightfastness. Dyed fabric was kept in light fastness chamber in such a manner that half dyed fabric is exposed to Xenon arc lamp for 18 h. The samples later equated with standard Blue Wool Scale [16].
2-Amino-4-(7-diethylamino)-2-oxo-2H-chromen-3-yl) thiophene-3carbonitrile 3 (0.004 mol) is dissolved in 10 mL of methanol and a drops of conc. HCl is added to it. The clear Red solution is obtained. The reaction mass is cooled to 0–5 °C, the diazotized amine is added dropwise with continuous stirring and maintaining the temperature of 0–5 °C and at acidic pH. The pH was maintained at 3–4 using sodium
2.2.2.2. Washing fastness. The dyed fabric (2 × 5 cm) taken and out of which (2 × 2.5 cm) dyed fabric is stitched around edges between two fragments of cotton and polyester fabric and rest of the 2*2.5 cm dyed fabric is kept unstitched. The dyed samples are washed in lauder-ometer at 60 °C containing 5gpl soap solution and 2gpl soda ash for 30 min. After completion of 30 min the washed samples are unstitched, dried and the colour change is analyzed along with staining on the undyed cotton and wool fabric using a grey scale [16] (see Table 3).
Table 1 Arrangement scheme for UPF rating.
2.2.2.3. Sublimation fastness. The dyed fabric to be tested were sandwiched between the undyed fabric of polyester and nylon and 693
UPF rating
% UVR Transmitted
Protection Category
15–24 25–39 40-50+
6.7–4.2 4.1–2.6 < 2.5
GOOD VERY GOOD EXCELLENT
Dyes and Pigments 163 (2019) 692–699
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acetate or sodium carbonate solution [24]. The dyes 3a-3e are isolated by filtration and purified by recrystallization. Synthetic scheme of coumarin disperse azo dye.
δ (Z) 8.45 (s, 2H), (F) 8.10 (s, 1H), (D) 7.54 (d, J = 8.9 Hz, 1H), (A) 7.44 (d, J = 8.3 Hz), (B) 7.22 (d, J = 8.3 Hz, 2H), (C) 6.76 (dd, J = 8.9, 2.3 Hz, 1H), (E) 6.60 (d, J = 2.3 Hz, 1H), (Y) 3.46 (q, J = 7.0 Hz, 4H), (M) 2.30 (s, 3H), (Z) 1.14 (t, J = 7.0 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 166.9 (s), 159.4 (s), 156.8 (s), 151.7 (s), 150.4 (s), 146.8 (s), 141.0 (s), 139.8 (s), 138.58(s), 130.2 (s), 125.9 (s), 122.0 (s), 111.4 (s), 109.9 (s), 108.0 (s), 96.7 (s), 87.8 (s), 62.9 (s), 44.6 (s), 21.3 (s), 12.7 (s). MS (m/z): calculated 457.16, [M+H]+ for C25H23N5O2S found 458.25, [M+H]+, CHN data “Anal. Calculated for C25H23N5O2S C, 65.63, H, 5.07, N, 15.32. Found: C, 65.65, H, 5.07, N, 15.32.”
4. Compounds characterization 4.1. 2-Amino-4-(7-(diethylamino)-2-oxo-2H-chrome-3-yl)-5-((4nitrophenyl)diazenyl)thiophene-3-carbonitrile (3a) 3a was purified by recrystallization with ethanol (hot filter). Yield 80% mp (at pressure mmHg) 218–220 °C.IR (v cm−1): 3407 (NH2 str.), 2210 (CN), 1780 (-O-C=O), 1595 (-N=N-), 1305 (N-O str.), 827 (C-S). 1 H NMR (500 MHz, DMSO) δ (Z) 9.01 (s, 2H), (A) 8.25 (d, J = 9.1 Hz, 2H), (F) 8.20 (s, 1H), (B) 7.67 (d, J = 9.1 Hz, 2H), (D) 7.58 (d, J = 9.0 Hz, 1H), (C) 6.79 (dd, J = 9.0, 2.3 Hz, 1H), (E) 6.62 (d, J = 2.3 Hz, 1H), (Y) 3.49 (q, J = 7.0 Hz, 4H), (X)1.15 (t, J = 7.0 Hz, 6H). 13 C NMR (201 MHz, DMSO) δ 169.2 (s), 159.1 (s), 157.1 (s), 156.6 (s), 152.1 (s), 147.7 (s), 146.5 (s), 138.5 (s), 131.1 (s), 125.5 (s), 122.4 (s), 114.6 (s), 110.7 (s), 110.1 (s), 108 (s), 96.7 (s), 90.4 (s), 65.3 (s), 44.7 (s), 12.8 (s). MS (m/z): calculated 488.13, [M+H]+ for C24H20N6O4S found 489.20, [M+H]+, CHN data “Anal. Calculated for C24H20N6O4S C, 59.01, H, 4.13, N, 17.20. Found: C, 59.04, H, 4.14, N, 17.21.”
4.5. 2-Amino-4-(7-(diethylamino)-2-oxo-2H-chrome-3-yl)-5-((4methoxyphenyl)diazenyl)thiophene-3-carbonitrile (3e). 3e was purified by recrystallization with ethyl acetate (hot filter). Yield 86% mp (at pressure mmHg) 227–228 °C. IR (v cm−1): 3382 (NH2 str.), 2218 (CN), 1697 (-O-C=O), 1595 (-N=N-), 1251(C-O str.) 819 (C-S). 1H NMR (500 MHz, DMSO) δ (Z) 8.38 (s, 2H), (F) 8.11 (s, 1H, =CH), (D) 7.56 (d, J = 9.0 Hz, 1H), (A) 7.52 (d, J = 9.1 Hz, 2H), (B) 6.99 (d, J = 9.1 Hz 2H), (C) 6.77 (dd, J = 9.0, 2.3 Hz 1H), (E) 6.61 (d, J = 2.3 Hz, 1H), (N) 3.78 (s, 3H), (Y) 3.47 (q, J = 7.0 Hz, 4H), (X) 1.15 (d, J = 7.0 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 166.5 (s), 160.9 (s), 159.4 (s), 156.8 (s), 151.6 (s), 146.7 (s), 146.4 (s), 139.7 (s), 138.7 (s), 130.7 (s), 123.8 (s), 115.33 (s), 115.06 (s), 111.5 (s), 109.9 (s), 108.44–108.14 (m), 96.7 (s), 87.4 (s), 55.94 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 473.15, [M+H]+ for C25H23N5O3S found 474.25, [M+H]+, CHN data “Anal. Calculated for C25H23N5O3S C, 63.41, H, 4.90, N, 14.79. Found: C, 63.44, H, 4.90, N, 14.78.” Note: The 1H signals numerated as A,B,C,D,E,F,X,Y,Z,M,N are shown and specified in SI. Figs. S2, S3, S4, S5 and S6.
4.2. (E)-2-Amino-5-((4-cyanophenyl)diazenyl)-4-(7-(diethylamino)-2oxo-2H-chromen-3yl)thiophene-3-carbonitrile (3b). Yield 86% mp (at pressure mmHg) 235–237 °C IR (v cm−1): 3319 (NH2 str.), 2217 (CN), 1710 (-O-C=O), 1587 (-N=N-), 821 (C-S). 1 H NMR (400 MHz, DMSO) δ (Z) 8.91 (s, 2H), (F) 8.16 (s, 1H), (A) 7.83 (d, J = 8.0 Hz, 2H), (B) 7.60 (d, J = 8.0 Hz, 2H), (D) 7.55 (d, J = 8.6 Hz, 1H), (C) 6.76 (d, J = 8.6, 2.3 Hz, 1H), (E) 6.59 (s, J = 2.3 Hz, 1H), (Y) 3.46 (q, 4H the q merged with the moisture of DMSO), (X) 1.12 (t, J = 6.8 Hz, 6H, J = 6.8 Hz). 13C NMR (201 MHz, DMSO) δ 168.8 (s), 159.1 (s), 157 (s), 154.9 (s), 152 (s), 147.4 (s), 145.6 (s), 138.2 (s), 134 (s), 131 (s), 122.4 (s), 119.3 (s), 114.7 (s), 110.9 (s), 110.4 (s), 110.1 (s), 108 (s), 96.8 (s), 89.9 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 468.13, [M+H]+ for C25H20N6O2S found 469.25, [M+H]+, CHN data “Anal. Calculated for C25H20N6O2S C, 64.09, H, 4.30, N, 17.94. Found: C, 64.10, H, 4.30, N, 17.95.”
5. Results and discussion The intermediate 3 was synthesized by Gewald reaction [15]. Substituted anilines are used as diazonium salt (see Fig. 1) and coupled with 3 to get five novel coumarin thiophene bridge disperse azo dyes. The azo dyes are characterized by FT-IR, 1H NMR, 13C NMR spectroscopic analyses. All the dyes obtained are brown to red solid with good yields. In FT-IR spectra, the stretching frequency 3350-3625 cm−1 corresponds to the primary amines in the skeleton. The occurrence of the azo group is shown by the 1488-1595 cm−1 bands. The bands at 2200-2220 cm−1 represent the presence of the CN group. All the other bands in the spectra represent other functionalities of the synthesized azo dyes. The 1H NMR spectra are noted in DMSO-d6 at 25–27 °C using TMS as an internal standard. The NMR data of all compounds show the aromatic protons (doublets) in the range of 6.38 and 7.69 ppm. The presence of the characteristic triplet between 1.0 and 1.10 ppm and quartet at around 3.45–3.48 ppm represents the ethyl group attached to N, N diethyl coumarin. The singlet protons obtained at 2.30 ppm and 3.78 ppm assigned for methyl and methoxy group attached to aromatic ring of (3d) and (3e) respectively. The other 1H signals are in agreement with assigned structures. The UPF and antimicrobial activity all five azo dyes were carried out as mentioned in the method. Theoretically, the global reactivity descriptors are determined using DFT computation.
4.3. 2-Amino-5-((4-chlorophenyl)diazenyl)-4-(7-(diethylamino)-2-oxo2H-chrome-3-yl)thiophene-3-carbonitrile (3c). 3c was purified recrystallization in chloroform (hot filter). Yield 76% mp (at pressure mmHg) 228–230 °C. IR (v cm−1): 3357 (NH2 str.), 2208 (CN), 1716 (-O-C=O), 1515 (-N=N-), 827 (C-S). 1 H NMR (500 MHz, DMSO) δ (Z) 8.61 (s, 2H), (F) 8.13 (s, 1H), (A) 7.55 (d, J = 9.0 Hz, 2H), (D) 7.52 (d, J = 8.1 Hz, 1H), (B) 7.47 (d, J = 9.0 Hz, 2H), (C) 6.76 (d, J = 8.1, 2.3 Hz, 1H), (E) 6.60 (s, J = 2.3 Hz. 1H), (Y) 3.47 (q, J = 6.5 Hz, 4H), (X) 1.14 (t, J = 6.5 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 167.6 (s), 159.2 (s), 156.9 (s), 151.8 (s), 151 (s), 147 (s), 142.8 (s), 138.2 (s), 133.7 (s), 130.8 (s), 129.8 (s), 123.5 (s), 115 (s), 111.2 (s), 110 (s), 108 (s), 96.7 (s), 88.5 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 477.1, [M+H]+ for C24H20ClN5O2S found 478.1, [M+H]+, CHN data “Anal. Calculated for C24H20ClN5O2S C, 60.31, H, 4.22, N, 14.65. Found: C, 60.34, H, 4.23, N, 14.66.” 4.4. 2-Amino-4-(diethylamino)-2-oxo-2H-chromen-3yl)-5-(ptolyldiazenyl)thiophene-3-carbonitrile (3d). 3d was purified by column chromatography in 25% ethyl acetate in pet ether. Yield 62% mp (at pressure mmHg) 238–240 °C. IR (v cm−1): 3641 (NH2 str.), 3186 (Ar-H), 2937 (CH3), 2206 (CN), 1699 (-O-C=O), 1591 (-N=N-), 819 (C-S). 1H NMR (500 MHz, DMSO)
Fig. 1. Substituted Anilines for diazotization. 694
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Fig. 2. Synthetic scheme.
5.1. Spectral characteristic of azo dyes Table 2 Absorption data of all five dyes in DMF.
The absorption spectra of all the dyes (10 μM solutions) were recorded in DMF. All the dyes display a dual peak, the shorter wavelength band in the range of 405 nm–410 nm is mainly due to π-π∗ transition of the aromatic system and the other longer wavelength broad hump in the range of 465 nm-495 nm is due to n-π∗ (charge transfer) respectively [25]. The dye 3a shows red-shifted absorption (see Table 2, Fig. 3.), as compared to the other four dyes. As − NO2 is a strong electron withdrawing group (EWG) it shows a bathochromic shift [26].
Solvent
DMF DMF DMF DMF DMF
5.2. Assessment of colour
a b
The colour assessment showed that synthesized dyes have excellent dyeability for both nylon as well as polyester fabric. But the K/S and percent (%) exhaustion values for nylon are expected to be higher than polyester, as nylon has the compact and an open structure being knitted fabric as compared to polyester making it an easy medium for dyeing, also nylon has higher gsm (gram per square meter) ratio as compared to polyester [5,28]. Therefore, the % exhaustion of the only polyester was evaluated. The % exhaustion results were found to be appreciable. It was concluded that 3a has the lowest exhaustion percent, on the contrary 3b has the most percent exhaustion (see Table 3). If we consider the series from electron accepting group to electron donating group (NO2 > CN > Cl > Me > OMe), the shades of disperse azo dye changes from dark brown > orange > light orange. The dye 3a contain -NO2 group which is strong acceptor, -NO2 is the strongest chromophore causing strong resonance, hence it shows darker shade as compared to the rest of the other azo dyes [29].
c
Dye
3a 3b 3c 3d 3e
Absorptiona
ε Maxb
FWHMc
(nm)
va(cm−1)
(mol−1 cm−1)
nm
(cm−1)
649 474 479 480 495
15408.32 21097.0 20876.83 20833.3 20202.02
61400.7 99722 88644 49988.6 43317.9
295 174 144 130 129
11268.1 5685.7 7467.3 7127.2 6921.6
Absorption maxima in (nm). Molar extinction co-efficient (mol−1 cm−1). Full width half maxima (nm).
5.3. Fastness properties Fig. 3. Absorption spectra of all 5 dyes in DMF.
We observed that all the five dyes show (6–5 rating) which indicates very good to better light fastness property in the case of polyester while 695
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Table 3 Colour quantity values in terms of K/S and CIELAB values for dyeing of polyester 2% dyed fabrics. (Std. -OMe). DYE
L*
a*
b*
K/S
% Exhaustion
3a 3b 3c 3d 3e
44.003 47.033 60.954 62.476 60.954
15.957 15.639 17.577 9.016 12.024
22.94 19.285 22.032 7.182 10.953
4.189 5.238 5.876 5.424 3.762
63.23 88.23 81.03 77.08 75.60
Table 6 Results (UPF rating) of all five disperse dyes.
Light Fastness Rating (1–8)
Polyester 3a 6–5 3b 6–5 3c 5 3d 5 3e 5
Wash Fastness Rating (1–5)
Dye Nylon 3a 3b 3c 3d 3e
4–3 4–3 5–4 5–4 5
UPF Ratings Polyester
3a 3b 3c 3d 3e
29.75 29.62 25.96 25.84 25.35
UPF rating: 15–24 40–50 + Excellent.
Table 4 Rating of Light and Wash Fastness for all five dyed polyester fabric. Dye
Dye
Light Fastness Rating (1–8)
Wash Fastness Rating (1–5)
4 5–4 4 5 5
4–3 4–3 5–4 5–4 5
Good,
25–39
Very
Good,
Rating* (Light fastness: 1-poor, 2-fair, 3-moderate, 4-good, 5-better, 6-very good, 7-best and 8-Excellent) (Wash Fastness: 1-poor, 2-fair, 3-good, 4-very good and 5-Excellent). Fig. 4. Comparison of synthesized dyes UPF range with standard range.
in case of nylon the ratings are in the range of (5–4) which is better to good [16]. The washing fastness results showed that all the five dyes have excellent to good washing fastness property for polyester. It was observed that (see Table 4), 3a has strong EWG group (-NO2) which show high lightfastness (i.e. high photostability) whereas 3e has a strong donor group (-OMe) which shows low lightfastness (i.e. low photostability). The trend of photostability i.e. the highest light fastness to the lowest light fastness is as follows, (3a > 3b > 3c > 3d > 3e). Sublimation Fastness. Sublimation fastness ratings for all five polyester and nylon fabric [16] (see Table 5). In sublimation fastness, there was no staining detected on the undyed fabric of polyester and nylon at 150 °C and 180 °C, but at 210 °C the nylon fabric itself gets degraded along with undyed fabric, so it becomes very hard to visualize staining, therefore we concluded that all 5 disperse dye have excellent sublimation fastness property.
5.5. Antimicrobial activity Generally, antimicrobial active compounds diffuse into the agar gel and inhibit the growth of microorganisms, therefore the antimicrobial activity is examined by measuring the diameter of the zone of inhibition [18,31]. The five newly synthesized azo dyes were screened for antimicrobial activity by dissolving in N, N -dimethylformamide (DMF) against S. aureus (AATCC 6538) (gram + ve bacteria) and K. pneumoniae (AATCC 4352) (gram –ve bacteria) by using the agar well diffusion method. According to Activity Index, the well diffusion results reveal that all the five azo dyes show excellent to intermediate antimicrobial activity towards the tested microbes which was confirmed by a zone of inhibition [18,30](see Table 7, Fig. 5). Images of determination of antimicrobial activity by well diffusion method: Further, to evaluate the minimum inhibitory concentration (MIC) of the dyed fabric, a test named AATCC 100 was executed. It is the minimum concentration of the dye active towards bacteria. It is calculated using equation (2)
5.4. Ultraviolet protecting factor (UPF) The UPF result disclosed clear evidence that, the darker shade, better is the UPF value [17]. In our case, the maximum UPF value was given by 3a which is expected as it possesses dark shade, and as the shade decreases the UPF value also decreases linearly [17] (see Table 6 Fig. 4.). Therefore we conclude that all the disperse dyes applied on fabric show very good UPF rating between 25 and 39, suggesting transmittance of 4.1–2.6% (i.e. blocking 95.5–97.4%) of the UV radiation which acting as a very good UV rays protector for textile materials [27].
R=
3a 3b 3c 3d 3e
Polyester 180 °C
210 °C
150 °C
180 °C
210 °C
5 5 5 5 5
5 5 5 5 5
5–4 5–4 5–4 5–4 5–4
5 5 5 5 5
4–3 4–3 4 4 4
3–2 3–2 3–2 3–2 3–2
(2)
Table 7 Well Diffusion test results with Gram-positive (S. aureus) and Gram-negative (K. pneuminiae). Sample Name
Nylon
150 °C
A)
where R is the percent (%) reduction, A is the number of bacteria colonies recovered after 18 h, B is the number of bacteria colonies present at 0 h [18]. The result of AATCC 100 concludes that the fabric dyed
Table 5 (Sublimation Fastness: 1-poor, 2-fair, 3-good, 4-very good and 5-Excellent). DYE
100(B B
3a 3b 3c 3d 3e
Note: Diameter of the well: 1 cm. 696
Zone of Inhibition (cm) S. aureus
K. pneumoniae
2.1 1.8 1.8 2.1 1.9
2.1 1.8 1.8 2.0 1.8
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Fig. 5. Specimen X is CH3 (3d) substituted azo dye and Specimen Y is NO2 (3a) substituted azo dye.
Fig. 7. Correlation of light fastness and Electrophilicity index (ω).
Table 8 Organism Used: 1. Staphylococcus aureus Strain No. AATCC 6538 (GramPositive Bacteria). 2. Klebsiella pneumoniae Strain No. AATCC 4352 (Gram Negative Bacteria). Sample Identification
Test Culture
No. of colonies recovered at 0 h [B]
No. of colonies recovered at 18 h [A]
% Reduction [R]
1. 3a
S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae
164 192 176 188 188 196 168 168 178 192
5 7 16 18 6 6 9 9 9 9
96.95 96.35 96.73 95.31 96.80 95.91 94.64 94.64 90.90 90.42
2. 3b 3. 3c 4. 3d 5. 3e
Fig. 8. Linear Trend of Electrophilicity Index and UPF ratings.
concludes that 3a has maximum inhibitory activity towards microbes. AATCC 100 test result:
Images of MIC study by AATCC 100 test method.
6. Computational study 6.1. Global reactivity descriptors (GRD) To correlate the experimentally investigated photostability and light fastness property, it was necessary to evaluate the photostability of the dyes theoretically, using global reactivity descriptor (GRD). This descriptor is used to develop the quantitative structure-activity relation (QSAR) and structure-property (QSPR) [32]. Electrophilicity index (ω) is one of the global descriptor which relates QSAR and QSPR. The large electron flow from the donor i.e. highest occupied molecular orbitals (HOMO) to the acceptor i.e. lowest occupied molecular orbitals (LUMO) causes lowering of energy whiich gives electrophilicity index (ω) [33]. It is defined as follows:
=
µ2 2
(3)
where, μ = chemical potential.η = chemical hardness. The conceptual density functional theory (CDFT) consisting of descriptors like, electrophilicity index(ω), chemical hardness (η) and chemical softness (S) which are used to predict the biological properties and photostability [33,34]. One of the important CDFT descriptors applied to study photostability and light fastness is the electrophilicity index (ω) [35]. The electrophilicity index (ω) is concerned with energy stabilization phenomena, which takes place when electron transfer takes place from environment to the molecular system, and the system is stabilized more and the value of (ω) rises, therefore such molecules show high photostability. Theoretically, 3a has the highest ω value i.e. high photostability as compared to the other dyes (see S10). A similar observation was visualized in experimental lightfastness values (see S10). Therefore, we
Fig. 6. Specimen X is (3d) CH3 substituted and specimen Y is (3a) NO2 substituted azo dye respectively.
with 3e has the lowest % reduction value towards both AATCC 6538 (gram + ve bacteria) and AATCC 4352 (gram –ve bacteria), whereas the fabric dyed with 3a has maximum % reduction towards AATCC 6538 (gram + ve bacteria) and AATCC 4352 (gram –ve bacteria) revealing the highest antimicrobial activity (see Table 8, Fig. 6.). It 697
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Fig. 9. HOMO-LUMO energy band gap at B3LYP-6-311++G(d,p). Similar experimental results are attained by AATCC 100 test. From the data (S12. Fig. 10), we have interrelated antimicrobial activity with HOMO-LUMO energy gap. As the HOMO-LUMO gap decreases antimicrobial activity (inhibition activity) increases.
calculated HOMO-LUMO energy gap and global reactivity descriptors (GRD). The electrophilicity index (ω) obtained was successfully correlated with the experimental light fastness property and UPF ratings. Dye 3a has less HOMO-LUMO energy band gap compared to other dyes and therefore it exhibits excellent “antimicrobial activity (Inhibition activity) which was confirmed by the AATCC 100 test method.” Acknowledgment Authors are thankful to the UGC-CAS for the financial grant and Textile Department (ICT, Mumbai) for allowing to use the facilities for application studies on textiles. Appendix A. Supplementary data
Fig. 10. Correlation of HOMO-LUMO energy band gap with Antimicrobial Activity.
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.dyepig.2018.12.050.
concluded that, the electrophilicity index (ω) and light fastness property are linearly related to each other (see Fig. 7) [36]. Also, we studied the correlation between the experimental UPF ratings of all five azo dyes with electrophilicity index (ω). 3a show maximum UPF and electrophilicity index (ω) whereas, 3e show minimum UPF ratings and electrophilicity index (ω) value (see S11. Fig. 8). So we settled that there is a direct relation among UPF and electrophilicity index (ω). Further, it is reported that the HOMO-LUMO energy gap of a molecule is related to inhibition activity [37]. As seen in (S12. Fig. 9) 3a have the lowest HOMO-LUMO energy gap as compared to the rest of the dyes. Low HOMO-LUMO gap suggests low stability which implies high reactivity towards the microbes [37].
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7. Conclusion We have successfully synthesized and characterized five courmarin azo thiophene bridge. Nylon and polyester coloured with the five novel disperse dyes reported in this paper exhibit multi-functional properties. All the dyes show very good UPF values and excellent antimicrobial activity. 3a is the most active dye which shows UPF and antimicrobial activity. Additionally, using theoretical DFT computations, we have 698
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Photostable coumarin containing azo dyes with multifunctional property Nitesh N. Ayare, Supriya H. Ramugade, Nagaiyan Sekar
T
∗
Dyestuff Technology Department, Institute of Chemical Technology, N. P. Marg, Matunga, Mumbai, 400019, Maharashtra, India
ARTICLE INFO
ABSTRACT
Keywords: Coumarin-azo dyes Fastness property UPF Antimicrobial activity HOMO-LUMO gap Global reactivity descriptors
A series five coumarin azo disperse dyes with thiophene bridge are synthesized using diazotized aniline derivatives which are confirmed by FT-IR, 1H NMR, 13C NMR, and CHN analysis. The dyes are applied on polyester and nylon material. The multifunctional properties (lightfastness, washing fastness, sublimation fastness, K/S, UPF, and antimicrobial activity) of the dyed fabric are determined. The dye 3a (-NO2) show red shifted absorption (649 nm) and blocking 95.5–97.4% of UV radiations with 96% antimicrobial property. The geometries of all the azo dyes are optimized using Density Functional Theory (DFT). The Global Reactivity Descriptors (GRD) are evaluated at the same method of theory. The GRD obtained shows a linear relation with lightfastness and UPF ratings. The antimicrobial activity of all synthesized dyes are determined by AATCC 100 test method and it is correlated with the HOMO-LUMO energy band gap.
1. Introduction The fundamental function of textile fabric is to cover and protect the human body from harmful ultraviolet (UV) rays, microbes, and bacteria [1,2]. It is reported that a fabric made from yarn fulfil the basic function of protecting the human skin through the multifunctional properties [2]. The multifunctional properties include antimicrobial, UV protective, moisture control, and other comfort properties [2]. The natural dyes extracted from neem, turmeric, marigold, onion, annatto plant, Eclipta show antimicrobial and ultraviolet protective properties [3,4]. But natural dyes exhibit inherent drawbacks like poor tinctorial strength, inferior light fastness properties, and use of metallic mordants generates serious problems affecting the environment [5,6]. Therefore, the natural dyes are preferred over synthetic dyes in niche areas. Majority of natural dyes contain chromones, flavonoids, and coumarin core which exhibit the antimicrobial and ultraviolet protective property [4,7,8]. Numerous natural products contain coumarins and heterocyclic moieties which possess medicinal properties [9,10]. Dyes containing heterocyclic units are commonly used as an additive in foods, cosmetics, pharmaceuticals and in optical brighteners [10]. Thiophene is an important heterocyclic system in dyes as it leads to better dyeability and intrinsic conjugation of electrons which causes charge tranfer (CT) [11]. It also enhances the antimicrobial activity, sublimation fastness property, and tinctorial strength [12]. Incorporation of the electron withdrawing group (EWG) brings photostability which intensifies light fastness property [13]. Therefore, the overall significance of synthetic
∗
azo dyes is excellent tinctorial strength, with brighter dyeing and fastness property [6,14]. The above benefits motivated us to synthesize coumarin azo dyes with thiophene bridge, and the structure of the dyes synthesized are given in Fig. 2. The disperse dyes are applied on nylon and polyester and materials. The fastness property, K/S values, Ultraviolet protection factor (UPF) and the antimicrobial activity are evaluated using different test methods. The experimental findings are correlated with the computational method by using Density functional theory (DFT). 2. Experimental 2.1. Materials 2.1.1. Chemicals p-Toluidine, p-cynoaniline, p-chloroaniline, p-nitroaniline, p-methoxyaniline and, sodium carbonate, sodium nitrate (NaNO2), HCl (33%), acetic acid, N,N-diethyl meta amino phenol (DEMAP) aldehyde, malononitrile, sulphur (S8) were bought from Spectrochem chemicals Ltd, Mumbai, India. Solid chemicals used are confirmed by melting point. Liquid chemicals are purified by distillation, confirmed by taking their boiling points and then used. Required solvents are purified according to standard protocol. 2.1.2. Substrate and measurement Nylon and 100% polyester fabrics were purchased from the local manufacturer (Piyush Syndicate yarn merchant and commission agent).
Corresponding author. E-mail addresses: [email protected], [email protected] (N. Sekar).
https://doi.org/10.1016/j.dyepig.2018.12.050 Received 2 October 2018; Received in revised form 21 December 2018; Accepted 21 December 2018 Available online 29 December 2018 0143-7208/ © 2018 Elsevier Ltd. All rights reserved.
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Perkin Elmer spectrophotometer with 1 cm quartz cells is used to record UV visible spectra of the titled dyes. The dyes of 10 μM are taken for UV visible study. The progress of reactions are examined by Thin layer chromatography (TLC) technique (60 F254) Merck, India. Purification of all compounds is attained by recrystallization. The coupler, 2-amino-4-(7-diethylamino)-2-oxo-2H-chromen-3-yl) thiophene-3-carbonitrile 3 is synthesized as described earlier [15]. “Melting points are noted on the instrument, Sunder Industrial Product, India. Jasco 4100”. The IR bands of the synthesized dyes are recorded on Fourier Transform IR (FT-IR) instrument. Agilent 400 MHz, 500 MHz and 800 MHz Bruker NMR instrument with tetramethylsilane (TMS) as the internal standard was used to record 1H NMR and 13C NMR spectra. CDCl3 and DMSO-d6 solvents used for sample preparation. Shimadzu Labsolution instrument with averaged ESI positive+ was used to analyse the mass of titled dyes.
were subjected on sublimation plate's fastness analyzer at different temperatures (150 °C, 180 °C, 210 °C) for 30 s. Further, the staining on the undyed fabric was checked and compared with standard Greyscale [16]. 2.2.3. Ultraviolet protection factor (UPF) Protection of skin from harmful UV radiation is done by textile fabric because the textile fabric can absorb, reflect and scatter UV radiation. The applied five dyed fabric need to have appreciable quantities of these protective agents to fulfill UV protection [5,17]. The table mentioned below is a sorting scheme for UPF ratings published in 1996, it is a standard for classification and determination of sun protective clothing (AS/NZ 4399) sourced by Australian and New Zealand which considered as a standard by industries as well [5,17] (see Table 1). 2.2.4. Antimicrobial activity With a view to protecting human skin from microbes, the textile fabric is imparted with the synthesized dyes, the antimicrobial activity was deduced using agar well diffusion method and quantitively effective antimicrobial activity are assessed using standard AATCC 100 test method [18].
2.1.3. Application of coumarin azo disperse dye The disperse azo dyes are applied on 100% polyester and nylon fabric through an aqueous medium. For dyeing of polyester, 2% shade and material to liquor ratio were kept at 1:30 with dyeing machine temperature at 130 °C for 45 min. The pH of dye bath was maintained between 4 and 5 using glacial acetic acid. Levelling agent, dispersing agent used were Supergen KDF and Saracen SO respectively, later the dyed fabric was introduced to reduction clearing treatment in 2 g/l solution of sodium hydrosulfite and NaOH at 70 °C for 20 min”. The dyed fabrics are finally rinsed, washed with cold water and dried [5,27]. “The nylon material is dyed using rota dyer machine at 100 °C for 60 min keeping the % shade, MLR ratio and pH similar to that of polyester dyeing”. The dyed nylon material obtained is washed followed by soaping and dried [5].
2.3. Computational fine points All the quantum chemical computations are preformed on Gaussian 09 program [19], while outcomes are visualized with Gauss View 5.0. All the dyes structure are optimized at ground state (S0) in the gas phase using Density Functional Theory (DFT). The hybrid function B3LYP used which is a combination of Becke's three parameter exchange functional (B3) [20] with the nonlocal correlation functional by Lee, Yang, and Parr (LYP) [21]. The energy band gap i.e. (HOMO – LUMO) and the global reactivity descriptors of the azo dyes are evaluated using the hybrid functional B3LYP and triple zeta basis set with both the diffuse function, 6–311++g(d,p) [22].
2.2. Methods 2.2.1. Assessment of colour The assessment of dyed fabric was done by using Spectrascan 5100 + instrument. The assessment was done on the basis of color space values (L*, a* and b*) and tinctorial strength in terms of K/S. L* represent brightness, a* represents red – green coordinate, b* represents yellow – blue coordinate. By assembling the above three, we conclude the tonal change of applied dye on fabric. The Rayscan Spectrascan 5100 + equipped with reflectance accessories is used to determine the absorbance of dyed fabric. The K/S values is evaluated using equation (1);
(1 R)2 K = S 2R
3. Synthesis 3.1. The general protocol of diazotization One of the substituted aromatic amines 1a -1e (0.1 g, 0.007 mol) is taken in water and acetic acid mixture. Conc. HCl (0.14 mol, 2.19 g, d = 1.1 gmL−1, 5.6 mL of 30% HCl) added to get either a clear solution or dispersion depending upon the amine used. Then the reaction mixture is cooled to 0-5 °C. 0.065 g, (0.0009mol) NaNO2 was dissolved in water (3 ml), and the resulting solution was added to the mixture slowly within 15 min. The reaction mixture is stirred for an hour at 0-5 °C. Completion of diazotization is checked using starch-iodide paper. The excess of nitrous acid present is quenched by adding 0.01 g of urea [23].
(1)
where R = Reflectance at complete opacity.S = Scattering coefficient.K = Absorption coefficient.
3.2. Coupling procedure
2.2.2. Fastness property 2.2.2.1. Lightfastness. Dyed fabric was kept in light fastness chamber in such a manner that half dyed fabric is exposed to Xenon arc lamp for 18 h. The samples later equated with standard Blue Wool Scale [16].
2-Amino-4-(7-diethylamino)-2-oxo-2H-chromen-3-yl) thiophene-3carbonitrile 3 (0.004 mol) is dissolved in 10 mL of methanol and a drops of conc. HCl is added to it. The clear Red solution is obtained. The reaction mass is cooled to 0–5 °C, the diazotized amine is added dropwise with continuous stirring and maintaining the temperature of 0–5 °C and at acidic pH. The pH was maintained at 3–4 using sodium
2.2.2.2. Washing fastness. The dyed fabric (2 × 5 cm) taken and out of which (2 × 2.5 cm) dyed fabric is stitched around edges between two fragments of cotton and polyester fabric and rest of the 2*2.5 cm dyed fabric is kept unstitched. The dyed samples are washed in lauder-ometer at 60 °C containing 5gpl soap solution and 2gpl soda ash for 30 min. After completion of 30 min the washed samples are unstitched, dried and the colour change is analyzed along with staining on the undyed cotton and wool fabric using a grey scale [16] (see Table 3).
Table 1 Arrangement scheme for UPF rating.
2.2.2.3. Sublimation fastness. The dyed fabric to be tested were sandwiched between the undyed fabric of polyester and nylon and 693
UPF rating
% UVR Transmitted
Protection Category
15–24 25–39 40-50+
6.7–4.2 4.1–2.6 < 2.5
GOOD VERY GOOD EXCELLENT
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acetate or sodium carbonate solution [24]. The dyes 3a-3e are isolated by filtration and purified by recrystallization. Synthetic scheme of coumarin disperse azo dye.
δ (Z) 8.45 (s, 2H), (F) 8.10 (s, 1H), (D) 7.54 (d, J = 8.9 Hz, 1H), (A) 7.44 (d, J = 8.3 Hz), (B) 7.22 (d, J = 8.3 Hz, 2H), (C) 6.76 (dd, J = 8.9, 2.3 Hz, 1H), (E) 6.60 (d, J = 2.3 Hz, 1H), (Y) 3.46 (q, J = 7.0 Hz, 4H), (M) 2.30 (s, 3H), (Z) 1.14 (t, J = 7.0 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 166.9 (s), 159.4 (s), 156.8 (s), 151.7 (s), 150.4 (s), 146.8 (s), 141.0 (s), 139.8 (s), 138.58(s), 130.2 (s), 125.9 (s), 122.0 (s), 111.4 (s), 109.9 (s), 108.0 (s), 96.7 (s), 87.8 (s), 62.9 (s), 44.6 (s), 21.3 (s), 12.7 (s). MS (m/z): calculated 457.16, [M+H]+ for C25H23N5O2S found 458.25, [M+H]+, CHN data “Anal. Calculated for C25H23N5O2S C, 65.63, H, 5.07, N, 15.32. Found: C, 65.65, H, 5.07, N, 15.32.”
4. Compounds characterization 4.1. 2-Amino-4-(7-(diethylamino)-2-oxo-2H-chrome-3-yl)-5-((4nitrophenyl)diazenyl)thiophene-3-carbonitrile (3a) 3a was purified by recrystallization with ethanol (hot filter). Yield 80% mp (at pressure mmHg) 218–220 °C.IR (v cm−1): 3407 (NH2 str.), 2210 (CN), 1780 (-O-C=O), 1595 (-N=N-), 1305 (N-O str.), 827 (C-S). 1 H NMR (500 MHz, DMSO) δ (Z) 9.01 (s, 2H), (A) 8.25 (d, J = 9.1 Hz, 2H), (F) 8.20 (s, 1H), (B) 7.67 (d, J = 9.1 Hz, 2H), (D) 7.58 (d, J = 9.0 Hz, 1H), (C) 6.79 (dd, J = 9.0, 2.3 Hz, 1H), (E) 6.62 (d, J = 2.3 Hz, 1H), (Y) 3.49 (q, J = 7.0 Hz, 4H), (X)1.15 (t, J = 7.0 Hz, 6H). 13 C NMR (201 MHz, DMSO) δ 169.2 (s), 159.1 (s), 157.1 (s), 156.6 (s), 152.1 (s), 147.7 (s), 146.5 (s), 138.5 (s), 131.1 (s), 125.5 (s), 122.4 (s), 114.6 (s), 110.7 (s), 110.1 (s), 108 (s), 96.7 (s), 90.4 (s), 65.3 (s), 44.7 (s), 12.8 (s). MS (m/z): calculated 488.13, [M+H]+ for C24H20N6O4S found 489.20, [M+H]+, CHN data “Anal. Calculated for C24H20N6O4S C, 59.01, H, 4.13, N, 17.20. Found: C, 59.04, H, 4.14, N, 17.21.”
4.5. 2-Amino-4-(7-(diethylamino)-2-oxo-2H-chrome-3-yl)-5-((4methoxyphenyl)diazenyl)thiophene-3-carbonitrile (3e). 3e was purified by recrystallization with ethyl acetate (hot filter). Yield 86% mp (at pressure mmHg) 227–228 °C. IR (v cm−1): 3382 (NH2 str.), 2218 (CN), 1697 (-O-C=O), 1595 (-N=N-), 1251(C-O str.) 819 (C-S). 1H NMR (500 MHz, DMSO) δ (Z) 8.38 (s, 2H), (F) 8.11 (s, 1H, =CH), (D) 7.56 (d, J = 9.0 Hz, 1H), (A) 7.52 (d, J = 9.1 Hz, 2H), (B) 6.99 (d, J = 9.1 Hz 2H), (C) 6.77 (dd, J = 9.0, 2.3 Hz 1H), (E) 6.61 (d, J = 2.3 Hz, 1H), (N) 3.78 (s, 3H), (Y) 3.47 (q, J = 7.0 Hz, 4H), (X) 1.15 (d, J = 7.0 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 166.5 (s), 160.9 (s), 159.4 (s), 156.8 (s), 151.6 (s), 146.7 (s), 146.4 (s), 139.7 (s), 138.7 (s), 130.7 (s), 123.8 (s), 115.33 (s), 115.06 (s), 111.5 (s), 109.9 (s), 108.44–108.14 (m), 96.7 (s), 87.4 (s), 55.94 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 473.15, [M+H]+ for C25H23N5O3S found 474.25, [M+H]+, CHN data “Anal. Calculated for C25H23N5O3S C, 63.41, H, 4.90, N, 14.79. Found: C, 63.44, H, 4.90, N, 14.78.” Note: The 1H signals numerated as A,B,C,D,E,F,X,Y,Z,M,N are shown and specified in SI. Figs. S2, S3, S4, S5 and S6.
4.2. (E)-2-Amino-5-((4-cyanophenyl)diazenyl)-4-(7-(diethylamino)-2oxo-2H-chromen-3yl)thiophene-3-carbonitrile (3b). Yield 86% mp (at pressure mmHg) 235–237 °C IR (v cm−1): 3319 (NH2 str.), 2217 (CN), 1710 (-O-C=O), 1587 (-N=N-), 821 (C-S). 1 H NMR (400 MHz, DMSO) δ (Z) 8.91 (s, 2H), (F) 8.16 (s, 1H), (A) 7.83 (d, J = 8.0 Hz, 2H), (B) 7.60 (d, J = 8.0 Hz, 2H), (D) 7.55 (d, J = 8.6 Hz, 1H), (C) 6.76 (d, J = 8.6, 2.3 Hz, 1H), (E) 6.59 (s, J = 2.3 Hz, 1H), (Y) 3.46 (q, 4H the q merged with the moisture of DMSO), (X) 1.12 (t, J = 6.8 Hz, 6H, J = 6.8 Hz). 13C NMR (201 MHz, DMSO) δ 168.8 (s), 159.1 (s), 157 (s), 154.9 (s), 152 (s), 147.4 (s), 145.6 (s), 138.2 (s), 134 (s), 131 (s), 122.4 (s), 119.3 (s), 114.7 (s), 110.9 (s), 110.4 (s), 110.1 (s), 108 (s), 96.8 (s), 89.9 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 468.13, [M+H]+ for C25H20N6O2S found 469.25, [M+H]+, CHN data “Anal. Calculated for C25H20N6O2S C, 64.09, H, 4.30, N, 17.94. Found: C, 64.10, H, 4.30, N, 17.95.”
5. Results and discussion The intermediate 3 was synthesized by Gewald reaction [15]. Substituted anilines are used as diazonium salt (see Fig. 1) and coupled with 3 to get five novel coumarin thiophene bridge disperse azo dyes. The azo dyes are characterized by FT-IR, 1H NMR, 13C NMR spectroscopic analyses. All the dyes obtained are brown to red solid with good yields. In FT-IR spectra, the stretching frequency 3350-3625 cm−1 corresponds to the primary amines in the skeleton. The occurrence of the azo group is shown by the 1488-1595 cm−1 bands. The bands at 2200-2220 cm−1 represent the presence of the CN group. All the other bands in the spectra represent other functionalities of the synthesized azo dyes. The 1H NMR spectra are noted in DMSO-d6 at 25–27 °C using TMS as an internal standard. The NMR data of all compounds show the aromatic protons (doublets) in the range of 6.38 and 7.69 ppm. The presence of the characteristic triplet between 1.0 and 1.10 ppm and quartet at around 3.45–3.48 ppm represents the ethyl group attached to N, N diethyl coumarin. The singlet protons obtained at 2.30 ppm and 3.78 ppm assigned for methyl and methoxy group attached to aromatic ring of (3d) and (3e) respectively. The other 1H signals are in agreement with assigned structures. The UPF and antimicrobial activity all five azo dyes were carried out as mentioned in the method. Theoretically, the global reactivity descriptors are determined using DFT computation.
4.3. 2-Amino-5-((4-chlorophenyl)diazenyl)-4-(7-(diethylamino)-2-oxo2H-chrome-3-yl)thiophene-3-carbonitrile (3c). 3c was purified recrystallization in chloroform (hot filter). Yield 76% mp (at pressure mmHg) 228–230 °C. IR (v cm−1): 3357 (NH2 str.), 2208 (CN), 1716 (-O-C=O), 1515 (-N=N-), 827 (C-S). 1 H NMR (500 MHz, DMSO) δ (Z) 8.61 (s, 2H), (F) 8.13 (s, 1H), (A) 7.55 (d, J = 9.0 Hz, 2H), (D) 7.52 (d, J = 8.1 Hz, 1H), (B) 7.47 (d, J = 9.0 Hz, 2H), (C) 6.76 (d, J = 8.1, 2.3 Hz, 1H), (E) 6.60 (s, J = 2.3 Hz. 1H), (Y) 3.47 (q, J = 6.5 Hz, 4H), (X) 1.14 (t, J = 6.5 Hz, 6H). 13C NMR (126 MHz, DMSO) δ 167.6 (s), 159.2 (s), 156.9 (s), 151.8 (s), 151 (s), 147 (s), 142.8 (s), 138.2 (s), 133.7 (s), 130.8 (s), 129.8 (s), 123.5 (s), 115 (s), 111.2 (s), 110 (s), 108 (s), 96.7 (s), 88.5 (s), 44.7 (s), 12.7 (s). MS (m/z): calculated 477.1, [M+H]+ for C24H20ClN5O2S found 478.1, [M+H]+, CHN data “Anal. Calculated for C24H20ClN5O2S C, 60.31, H, 4.22, N, 14.65. Found: C, 60.34, H, 4.23, N, 14.66.” 4.4. 2-Amino-4-(diethylamino)-2-oxo-2H-chromen-3yl)-5-(ptolyldiazenyl)thiophene-3-carbonitrile (3d). 3d was purified by column chromatography in 25% ethyl acetate in pet ether. Yield 62% mp (at pressure mmHg) 238–240 °C. IR (v cm−1): 3641 (NH2 str.), 3186 (Ar-H), 2937 (CH3), 2206 (CN), 1699 (-O-C=O), 1591 (-N=N-), 819 (C-S). 1H NMR (500 MHz, DMSO)
Fig. 1. Substituted Anilines for diazotization. 694
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Fig. 2. Synthetic scheme.
5.1. Spectral characteristic of azo dyes Table 2 Absorption data of all five dyes in DMF.
The absorption spectra of all the dyes (10 μM solutions) were recorded in DMF. All the dyes display a dual peak, the shorter wavelength band in the range of 405 nm–410 nm is mainly due to π-π∗ transition of the aromatic system and the other longer wavelength broad hump in the range of 465 nm-495 nm is due to n-π∗ (charge transfer) respectively [25]. The dye 3a shows red-shifted absorption (see Table 2, Fig. 3.), as compared to the other four dyes. As − NO2 is a strong electron withdrawing group (EWG) it shows a bathochromic shift [26].
Solvent
DMF DMF DMF DMF DMF
5.2. Assessment of colour
a b
The colour assessment showed that synthesized dyes have excellent dyeability for both nylon as well as polyester fabric. But the K/S and percent (%) exhaustion values for nylon are expected to be higher than polyester, as nylon has the compact and an open structure being knitted fabric as compared to polyester making it an easy medium for dyeing, also nylon has higher gsm (gram per square meter) ratio as compared to polyester [5,28]. Therefore, the % exhaustion of the only polyester was evaluated. The % exhaustion results were found to be appreciable. It was concluded that 3a has the lowest exhaustion percent, on the contrary 3b has the most percent exhaustion (see Table 3). If we consider the series from electron accepting group to electron donating group (NO2 > CN > Cl > Me > OMe), the shades of disperse azo dye changes from dark brown > orange > light orange. The dye 3a contain -NO2 group which is strong acceptor, -NO2 is the strongest chromophore causing strong resonance, hence it shows darker shade as compared to the rest of the other azo dyes [29].
c
Dye
3a 3b 3c 3d 3e
Absorptiona
ε Maxb
FWHMc
(nm)
va(cm−1)
(mol−1 cm−1)
nm
(cm−1)
649 474 479 480 495
15408.32 21097.0 20876.83 20833.3 20202.02
61400.7 99722 88644 49988.6 43317.9
295 174 144 130 129
11268.1 5685.7 7467.3 7127.2 6921.6
Absorption maxima in (nm). Molar extinction co-efficient (mol−1 cm−1). Full width half maxima (nm).
5.3. Fastness properties Fig. 3. Absorption spectra of all 5 dyes in DMF.
We observed that all the five dyes show (6–5 rating) which indicates very good to better light fastness property in the case of polyester while 695
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Table 3 Colour quantity values in terms of K/S and CIELAB values for dyeing of polyester 2% dyed fabrics. (Std. -OMe). DYE
L*
a*
b*
K/S
% Exhaustion
3a 3b 3c 3d 3e
44.003 47.033 60.954 62.476 60.954
15.957 15.639 17.577 9.016 12.024
22.94 19.285 22.032 7.182 10.953
4.189 5.238 5.876 5.424 3.762
63.23 88.23 81.03 77.08 75.60
Table 6 Results (UPF rating) of all five disperse dyes.
Light Fastness Rating (1–8)
Polyester 3a 6–5 3b 6–5 3c 5 3d 5 3e 5
Wash Fastness Rating (1–5)
Dye Nylon 3a 3b 3c 3d 3e
4–3 4–3 5–4 5–4 5
UPF Ratings Polyester
3a 3b 3c 3d 3e
29.75 29.62 25.96 25.84 25.35
UPF rating: 15–24 40–50 + Excellent.
Table 4 Rating of Light and Wash Fastness for all five dyed polyester fabric. Dye
Dye
Light Fastness Rating (1–8)
Wash Fastness Rating (1–5)
4 5–4 4 5 5
4–3 4–3 5–4 5–4 5
Good,
25–39
Very
Good,
Rating* (Light fastness: 1-poor, 2-fair, 3-moderate, 4-good, 5-better, 6-very good, 7-best and 8-Excellent) (Wash Fastness: 1-poor, 2-fair, 3-good, 4-very good and 5-Excellent). Fig. 4. Comparison of synthesized dyes UPF range with standard range.
in case of nylon the ratings are in the range of (5–4) which is better to good [16]. The washing fastness results showed that all the five dyes have excellent to good washing fastness property for polyester. It was observed that (see Table 4), 3a has strong EWG group (-NO2) which show high lightfastness (i.e. high photostability) whereas 3e has a strong donor group (-OMe) which shows low lightfastness (i.e. low photostability). The trend of photostability i.e. the highest light fastness to the lowest light fastness is as follows, (3a > 3b > 3c > 3d > 3e). Sublimation Fastness. Sublimation fastness ratings for all five polyester and nylon fabric [16] (see Table 5). In sublimation fastness, there was no staining detected on the undyed fabric of polyester and nylon at 150 °C and 180 °C, but at 210 °C the nylon fabric itself gets degraded along with undyed fabric, so it becomes very hard to visualize staining, therefore we concluded that all 5 disperse dye have excellent sublimation fastness property.
5.5. Antimicrobial activity Generally, antimicrobial active compounds diffuse into the agar gel and inhibit the growth of microorganisms, therefore the antimicrobial activity is examined by measuring the diameter of the zone of inhibition [18,31]. The five newly synthesized azo dyes were screened for antimicrobial activity by dissolving in N, N -dimethylformamide (DMF) against S. aureus (AATCC 6538) (gram + ve bacteria) and K. pneumoniae (AATCC 4352) (gram –ve bacteria) by using the agar well diffusion method. According to Activity Index, the well diffusion results reveal that all the five azo dyes show excellent to intermediate antimicrobial activity towards the tested microbes which was confirmed by a zone of inhibition [18,30](see Table 7, Fig. 5). Images of determination of antimicrobial activity by well diffusion method: Further, to evaluate the minimum inhibitory concentration (MIC) of the dyed fabric, a test named AATCC 100 was executed. It is the minimum concentration of the dye active towards bacteria. It is calculated using equation (2)
5.4. Ultraviolet protecting factor (UPF) The UPF result disclosed clear evidence that, the darker shade, better is the UPF value [17]. In our case, the maximum UPF value was given by 3a which is expected as it possesses dark shade, and as the shade decreases the UPF value also decreases linearly [17] (see Table 6 Fig. 4.). Therefore we conclude that all the disperse dyes applied on fabric show very good UPF rating between 25 and 39, suggesting transmittance of 4.1–2.6% (i.e. blocking 95.5–97.4%) of the UV radiation which acting as a very good UV rays protector for textile materials [27].
R=
3a 3b 3c 3d 3e
Polyester 180 °C
210 °C
150 °C
180 °C
210 °C
5 5 5 5 5
5 5 5 5 5
5–4 5–4 5–4 5–4 5–4
5 5 5 5 5
4–3 4–3 4 4 4
3–2 3–2 3–2 3–2 3–2
(2)
Table 7 Well Diffusion test results with Gram-positive (S. aureus) and Gram-negative (K. pneuminiae). Sample Name
Nylon
150 °C
A)
where R is the percent (%) reduction, A is the number of bacteria colonies recovered after 18 h, B is the number of bacteria colonies present at 0 h [18]. The result of AATCC 100 concludes that the fabric dyed
Table 5 (Sublimation Fastness: 1-poor, 2-fair, 3-good, 4-very good and 5-Excellent). DYE
100(B B
3a 3b 3c 3d 3e
Note: Diameter of the well: 1 cm. 696
Zone of Inhibition (cm) S. aureus
K. pneumoniae
2.1 1.8 1.8 2.1 1.9
2.1 1.8 1.8 2.0 1.8
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Fig. 5. Specimen X is CH3 (3d) substituted azo dye and Specimen Y is NO2 (3a) substituted azo dye.
Fig. 7. Correlation of light fastness and Electrophilicity index (ω).
Table 8 Organism Used: 1. Staphylococcus aureus Strain No. AATCC 6538 (GramPositive Bacteria). 2. Klebsiella pneumoniae Strain No. AATCC 4352 (Gram Negative Bacteria). Sample Identification
Test Culture
No. of colonies recovered at 0 h [B]
No. of colonies recovered at 18 h [A]
% Reduction [R]
1. 3a
S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae S. aureus K. pneumoniae
164 192 176 188 188 196 168 168 178 192
5 7 16 18 6 6 9 9 9 9
96.95 96.35 96.73 95.31 96.80 95.91 94.64 94.64 90.90 90.42
2. 3b 3. 3c 4. 3d 5. 3e
Fig. 8. Linear Trend of Electrophilicity Index and UPF ratings.
concludes that 3a has maximum inhibitory activity towards microbes. AATCC 100 test result:
Images of MIC study by AATCC 100 test method.
6. Computational study 6.1. Global reactivity descriptors (GRD) To correlate the experimentally investigated photostability and light fastness property, it was necessary to evaluate the photostability of the dyes theoretically, using global reactivity descriptor (GRD). This descriptor is used to develop the quantitative structure-activity relation (QSAR) and structure-property (QSPR) [32]. Electrophilicity index (ω) is one of the global descriptor which relates QSAR and QSPR. The large electron flow from the donor i.e. highest occupied molecular orbitals (HOMO) to the acceptor i.e. lowest occupied molecular orbitals (LUMO) causes lowering of energy whiich gives electrophilicity index (ω) [33]. It is defined as follows:
=
µ2 2
(3)
where, μ = chemical potential.η = chemical hardness. The conceptual density functional theory (CDFT) consisting of descriptors like, electrophilicity index(ω), chemical hardness (η) and chemical softness (S) which are used to predict the biological properties and photostability [33,34]. One of the important CDFT descriptors applied to study photostability and light fastness is the electrophilicity index (ω) [35]. The electrophilicity index (ω) is concerned with energy stabilization phenomena, which takes place when electron transfer takes place from environment to the molecular system, and the system is stabilized more and the value of (ω) rises, therefore such molecules show high photostability. Theoretically, 3a has the highest ω value i.e. high photostability as compared to the other dyes (see S10). A similar observation was visualized in experimental lightfastness values (see S10). Therefore, we
Fig. 6. Specimen X is (3d) CH3 substituted and specimen Y is (3a) NO2 substituted azo dye respectively.
with 3e has the lowest % reduction value towards both AATCC 6538 (gram + ve bacteria) and AATCC 4352 (gram –ve bacteria), whereas the fabric dyed with 3a has maximum % reduction towards AATCC 6538 (gram + ve bacteria) and AATCC 4352 (gram –ve bacteria) revealing the highest antimicrobial activity (see Table 8, Fig. 6.). It 697
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Fig. 9. HOMO-LUMO energy band gap at B3LYP-6-311++G(d,p). Similar experimental results are attained by AATCC 100 test. From the data (S12. Fig. 10), we have interrelated antimicrobial activity with HOMO-LUMO energy gap. As the HOMO-LUMO gap decreases antimicrobial activity (inhibition activity) increases.
calculated HOMO-LUMO energy gap and global reactivity descriptors (GRD). The electrophilicity index (ω) obtained was successfully correlated with the experimental light fastness property and UPF ratings. Dye 3a has less HOMO-LUMO energy band gap compared to other dyes and therefore it exhibits excellent “antimicrobial activity (Inhibition activity) which was confirmed by the AATCC 100 test method.” Acknowledgment Authors are thankful to the UGC-CAS for the financial grant and Textile Department (ICT, Mumbai) for allowing to use the facilities for application studies on textiles. Appendix A. Supplementary data
Fig. 10. Correlation of HOMO-LUMO energy band gap with Antimicrobial Activity.
Supplementary data to this article can be found online at https:// doi.org/10.1016/j.dyepig.2018.12.050.
concluded that, the electrophilicity index (ω) and light fastness property are linearly related to each other (see Fig. 7) [36]. Also, we studied the correlation between the experimental UPF ratings of all five azo dyes with electrophilicity index (ω). 3a show maximum UPF and electrophilicity index (ω) whereas, 3e show minimum UPF ratings and electrophilicity index (ω) value (see S11. Fig. 8). So we settled that there is a direct relation among UPF and electrophilicity index (ω). Further, it is reported that the HOMO-LUMO energy gap of a molecule is related to inhibition activity [37]. As seen in (S12. Fig. 9) 3a have the lowest HOMO-LUMO energy gap as compared to the rest of the dyes. Low HOMO-LUMO gap suggests low stability which implies high reactivity towards the microbes [37].
References [1] Ibrahim NA, Gouda M, Husseiny Sh M, El-Gamal AR, Mahrous F. UV-protecting and antibacterial finishing of cotton knits. J Appl Polym Sci 2009;112:3589–96. https:// doi.org/10.1002/app.29669. [2] Upasani PS, Sreekumar TV, Jain AK. Polyester fabric with inherent antibacterial, hydrophilic and UV protection properties. J Text Inst 2016;107:1135–43. https:// doi.org/10.1080/00405000.2015.1097082. [3] Murugesh Babu K, Ravindra KB. Bioactive antimicrobial agents for finishing of textiles for health care products. J Text Inst 2015;106:706–17. https://doi.org/10. 1080/00405000.2014.936670. [4] Rekha MS, Bhanu V. Effect of knitted bamboo structures dyed with natural colorants on ultraviolet radiation protection effect of knitted bamboo structures dyed with natural colorants on ultraviolet radiation protection effect of knitted bamboo structures. Dyed With Natural C 2015:1–2. https://doi.org/10.4172/2165-8064. 1000115. [5] Pawar AB, More SP, Adivarekar RV. Dyeing of polyester and nylon with semi-synthetic azo dye by chemical modification of natural source areca nut. Nat Products Bioprospect 2017;8:23–9. https://doi.org/10.1007/s13659-017-0144-8. [6] Wan Ahmad WY, Mohd Nor MA, Saim N, Ab Kadir MI, Ahmad MR. Nano natural dyes from Melastoma malabathricum L. Adv Mater Res 2012;545:59–63www. scientific.net/AMR.545.59. [7] Sarwar M, Ali S, Hussain MT, Atif M, Majeed MI. Cotton fabric dyeability assessment of floral extracts obtained from binary mixtures of Callistemon citrinus and Tagetes erecta L. 2018. p. 0478. https://doi.org/10.1080/15440478.2018. 1426077.
7. Conclusion We have successfully synthesized and characterized five courmarin azo thiophene bridge. Nylon and polyester coloured with the five novel disperse dyes reported in this paper exhibit multi-functional properties. All the dyes show very good UPF values and excellent antimicrobial activity. 3a is the most active dye which shows UPF and antimicrobial activity. Additionally, using theoretical DFT computations, we have 698
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