UV protective heterocyclic disperse azo dyes: Spectral properties, dyeing, potent antibacterial activity on dyed fabric and comparative computational study

Article abstract of DOI:10.1016/j.saa.2019.117353

Disperse azo dyes are synthesized and characterized by ¹H NMR, ¹³C NMR, LC-MS, Elemental analysis, UV–visible, and fluorescence spectroscopy methods. The azo dyes show absorption maxima in the range of 460–493 nm. Dye with benzothiaz

Full text of DOI:10.1016/j.saa.2019.117353

Accepted Manuscript
UV protective heterocyclic disperse azo dyes: Spectral properties,
dyeing, potent antibacterial activity on dyed fabric and
comparative computational study
Virendra R. Mishra, Chaitannya W. Ghanavatkar, Nagaiyan Sekar
PII:
S1386-1425(19)30743-7
DOI:
https://doi.org/10.1016/j.saa.2019.117353
Article
Number:
Reference:
117353
SAA 117353
Spectrochimica Acta Part A: Molecular and Biomolecular
Spectroscopy
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Received date:
Revised date:
Accepted date:
12 April 2019
28 June 2019
7 July 2019
Please cite this article as: V.R. Mishra, C.W. Ghanavatkar and N. Sekar, UV protective
heterocyclic disperse azo dyes: Spectral properties, dyeing, potent antibacterial activity on
dyed fabric and comparative computational study, Spectrochimica Acta Part A: Molecular
and Biomolecular Spectroscopy, https://doi.org/10.1016/j.saa.2019.117353
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ACCEPTED MANUSCRIPT
UV Protective Heterocyclic Disperse Azo Dyes: Spectral properties, Dyeing, Potent
Antibacterial activity on dyed fabric and Comparative Computational study
Virendra R. Mishraa, Chaitannya W. Ghanavatkara, Nagaiyan Sekara,*
aVirendra R. Mishra -ORCID ID- https://orcid.org/0000-0003-0070-4705
aChaitannya W. Ghanavatkar -ORCID ID- https://orcid.org/0000-0003-0821-1083
a,*Department of Dyestuff Technology, Institute of Chemical Technology, Matunga (E),
Mumbai, Maharashtra, India, PIN: 400 019.
E-mail: nethi.sekar@gmail.com; n.sekar@ictmumbai.edu.in
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Abstract
Disperse azo dyes are synthesized and characterized by 1H NMR, 13C NMR, LC-MS, Elemental
analysis, UV-visible, and fluorescence spectroscopy methods. The azo dyes show absorption
maxima in the range of 460-493 nm. Dye with benzothiazole moiety i.e. VM7a and VM8a show
a bathochromic shift in absorption maxima of 90 and 26 nm respectively in a polar aprotic
solvent (i.e. DMF, DMSO). The dyes show deep red emission in a polar aprotic solvent (i.e.
DMF, DMSO) with a Stokes shift of 62 to 180 nm. The dyes are applied on polyester fabric and
the dyed fabric exhibit excellent to a good wash and sublimation fastness property. They show a
very good UPF rating and almost blocking 95 to 98 % of harmful UV radiation. Antibacterial
activity of dyed polyester fabric is assessed qualitatively and quantitatively by using AATCC
147 and 100 test method respectively. The dyed fabrics exhibit excellent antibacterial activities
against S.aureus (Gram-positive) and K. pneumoniae (Gram-negative). DFT method was used to
identify the stable conformer. HOMO-LUMO gap and global reactivity descriptors were
calculated using DFT method and correlated with antibacterial activities and light fastness
properties respectively.
Keywords: Heterocyclic disperse dyes, UPF, Antibacterial activity, HOMO-LUMO gap, and
Electrophilicity Index.
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1. Introduction
Azo dyes (-N=N-) are widely used as colorants [1] and they contribute almost 50% of
synthetic colorants [2,3]. Moreover as textile colorants [4,5], they have many applications like in
ink-jet printing [6,7], photography [8], color additives [9], biomedical diagnostics [10],
molecular recognition [11], and liquid crystal industry [12–14]. Azo dyes containing hetero
atoms like sulfur and nitrogen occupy a niche position in recent years because of their good
performance in optical data storage [15], dye-sensitized solar cells [16–18], non-linear optics
[19–21], and the also provide bright and strong shades that range from red to green and blue
[22,23].
Heterocyclic azo dyes are as disperse azo dyes which exhibit good tinctorial strength,
large molar extinction, and brighter dyeing than those obtained from aniline based intermediates
[1,23–25]. Also, heterocyclic azo dyes exhibit biological activities based on their specific
structure [26–35] M. A. El-Borai etal [36] shown that azo dyes containing thiazole moiety
exhibit fair to moderate light fastness property. However, only some molecules show excellent
antimicrobial activities against gram-positive and gram-negative bacteria. A. Yahyazadeh etal
[31] reported that azo dyes with thiazole, benzothiazole, benzimidazole, and pyridine moiety
exhibit excellent wash fastness and significant antibacterial activity. Tahir Tilki etal [37] showed
that disazo dyes incorporate with imidazole and pyrazole moiety exhibit antimicrobial activity.
Thus, the scope of current work is to prepare heterocyclic disperse azo dyes containing a
group imparting antibacterial activity. In this paper, we have selected our previously reported
[26] six heterocyclic azo disperse dyes containing benzimidazole, benzoxazole and
benzothiazole moiety and evaluated their visible absorption and emission spectra in solvents of
different polarities. Furthermore, to dyed these disperse dyes on polyester fabric and evaluate
their fastness property, ultraviolet protection factor (UPF), K/S values, and the antibacterial
activities. Finally, Density Functional Theory method used to correlate the experimental finding.
2. Experimental Section
2.1 Materials and Equipment
Polyester fabrics were procured from the local manufacturer. All the necessary chemicals were
acquired from commercial sources and used as received. Solvents and chemicals were obtained
from the commercial source (Spectrochem and SD Fine Chemicals Ltd.) and then used for the
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experiments with no further purification. Thin layered chromatography plates (TLC) (0.25mm E-
Merck silica gel 60-F254, pre-coated) were used for monitoring the reactions. Visualization of
TLC plates were done under UV light. Melting points were recorded using standard melting
1
13
point apparatus. H NMR spectra were recorded on a 500 MHz and 400 MHz CNMR spectra
were recorded on the 126 MHz instrument of Agilent Technology. The absorption spectra were
recorded on a Perkin Elmer Lambda-25 spectrophotometer at room temperature. Fluorescence
spectra were performed with a Varian Cary Eclipse fluorescence spectrophotometer at room
temperature.
2.2 Methods
2.2.1 General procedure for dyeing
Dyeing of polyester fabric with the heterocyclic azo disperse dyes was done using standard
prodecure and detail procedure are given in supplementary information.
2.2.2 Fastness property
Fastness properties i.e. light fastness, washing and sublimation fastness of dyed fabric were
evaluated using standard procedure and detail procedure are given in supplementary information.
2.2.3 Color Measurements
Rayscan-Spectrascan 5100+ instrument were used to evaluate the color coordinates of dyed
fabric. CIELAB color space values (L*, a* and b*) and tinctorial strength i.e. K/S were used for
assessment of color values. L* represents brightness (100 for white, 0 for black), a* represents
red-green coordinate (+ ve for red, -ve for green), b* represents yellow-blue coordinate (+ve for
yellow, -ve for blue). K/S value is directly associated with the Dye concentration on polyester
fabrics.
The K/S values were determined using the equation:
where, R = reflectance at complete opacity; K = Absorption coefficient; S = Scattering
coefficient
2.2.4 Ultraviolet protection factor (UPF)
Ultraviolet Protection Factor (UPF) were used to measure the efficiency of fabric towards
harmful UV radiation. Higher the value of UPF implies that fabric will have greater protection
efficiency towards harmful UV radiation. AS/NZ 4339 is a standard method and mostly adopted
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among the existing methods to determined and classify the Sun Protective Clothing [38,39] (see
Table 1).
Table 1: UPF rating
UPF rating
% UVR transmitted
Protection efficiency
15-24
25-39
6.7–4.2
4.1–2.6
Good
Very Good
40-50+
≤2.5
Excellent
2.2.5 Antibacterial Activities
Agar-Well Diffusion method was used for screening of antibacterial activity of synthesized azo
disperse dyes. A pure culture of Staphylococcus aureus (Gram-positive) and Klebsiella
pneumoniae (Gram-negative) was employed in the test. The antibacterial activity of polyester
dyed fabrics were evaluated qualitatively and quantitatively by using AATCC 147 and AATCC
100 respectively.
2.2.6 Computational Method - Density Functional Theory (DFT)
The ground state geometry of all the possible tautomers of the dyes were optimize using the
hybrid functional, B3LYP with double zeta basis set 6-31G(d) as implemented in Gaussian 09
package [40]. The stable tautomer was further optimized by using a triple-zeta basis set with both
diffuse and polarization functions 6-311+G(d,p). Self-Consistent Reaction Field (SCRF) under
the Polarizable Continuum Model (PCM) was used for computations in various solvent media.
2.2.7 Synthesis and Characterization
The disperse dyes were synthesized as reported literature [26]. The general procedure for
diazotization and coupling reaction along with characterization are given in supplementary
information.
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Figure 1: Synthesized Azo dyes.
3. Result and Discussion
3.1 Photophysical study of azo dyes
UV-visible spectra of VM7(a-c) and VM8(a-c) are recorded in various organic solvents of
o
different polarity at 27 C. The absorption and emission data and their related properties are
outlined in Table 2. The absorption maxima (λmax.) for VM7(a-c) and VM8(a-c) were in the
range of 480-493 nm and 460-475 nm respectively in almost all the solvents. Whereas,
absorption maxima of VM7a and VM8a display a broad peak with a bathochromic shift of 90
and 26 nm respectively in polar aprotic solvents i.e. DMF and DMSO (Figure 2), which may be
due to existence of tautomeric equilibrium [41]. Furthermore, Dyes VM7(a-c) and VM8(a-c)
display emission in polar aprotic solvents in the range of 567 to 640 nm and 535 to 668 nm
respectively (Figure 3). Dyes VM7(a-c) and VM8(a-c) show a Stokes shift of 62-121 nm and
67-180 nm respectively.
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Figure 2: Absorption spectra of VM7(a-c) and VM8(a-c) in different solvents at 27 oC.
Figure 3: Emission spectra of VM7(a-c) and VM8(a-c) in different solvents at 27 oC.
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Table 2: Experimental electronic absorption and emission data of VM7(a-c) and VM8(a-c) in
different solvents at 27 oC.
Dyes
Solvents
Absorption
Molar Absorptivity (ε)
Emission
Stoke shift
λabs
λemi
(nm)
486
486
484
488
482
521
572
570
480
483
480
486
480
491
493
488
485
483
487
482
491
493
464
464
462
466
465
491
488
464
464
461
465
464
469
473
460
463
459
466
464
468
468
(cm)-1
20576
20576
20661
20492
20747
19194
17483
17544
20833
20703
20833
20576
20833
20367
20284
20492
20619
20704
20534
20747
20367
20284
21552
21552
21645
21459
21505
20367
20492
21552
21552
21692
21505
21552
21322
21142
21739
21598
21786
21459
21552
21367
21368
L mol-1 cm-1
34551
38023
37013
40012
35017
27726
28351
36177
20885
14795
15633
14567
12816
13562
16995
48756
53307
51001
54147
48009
47237
51544
17469
17155
17251
17141
14968
13248
18391
56915
65622
58217
66467
55579
59526
56744
17439
18911
17590
19206
15290
15766
15766
(nm)
(cm)-1
(nm) (cm)-1
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
Toluene
Acetonitrile
EtOAc
DCM
MeOH
VM7a
-
-
-
-
634
634
636
-
-
-
-
-
567
573
-
-
-
-
-
612
610
-
-
-
-
-
663
668
-
-
-
-
15773
15773
15723
113
62
66
-
-
-
-
-
76
80
-
-
-
-
-
121
117
-
-
-
-
-
172
180
-
-
-
-
-
73
76
-
3421
1710
1821
-
-
-
-
-
2729
2832
-
-
-
-
-
DMF
DMSO
Toluene
Acetonitrile
EtOAc
DCM
-
-
-
-
VM7b
-
MeOH
DMF
17637
17452
DMSO
Toluene
Acetonitrile
EtOAc
DCM
-
-
-
-
VM7c
VM8a
-
MeOH
DMF
16339
16393
4027
3890
DMSO
Toluene
Acetonitrile
EtOAc
DCM
-
-
-
-
-
-
-
-
-
MeOH
DMF
15083
14970
5284
5522
-
-
-
-
-
2872
2927
-
-
-
-
-
DMSO
Toluene
Acetonitrile
EtOAc
DCM
-
-
-
-
VM8b
-
542
549
-
-
-
-
MeOH
DMF
18450
18215
-
-
-
-
DMSO
Toluene
Acetonitrile
EtOAc
DCM
-
-
-
-
-
-
-
MeOH
535
618
18691
16181
67
150
2676
5186
VM8c
DMF
473
473
21142
21141
18100
18100
542
631
18450
15848
69
2691
5294
158
DMSO
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3.2 Assessment of dye uptake on polyester fabrics
The color values of disperse dyes VM7(a-c) and VM8(a-c) on polyester fabric were determined
by using CIELAB coordinates. The CIELAB coordinates L*, a*, b* and K/S for dyes were
measured and tabulated in Table 3. From Table 3, it was observed that all dyes have a good
affinity toward polyester fabric at high temperature and gave Orange to yellowish color shade.
The values of a* and b* coordinate proposes that the color hues of all dyes shifted towards the
redder and yellowish direction respectively. The “K/S” values of all dyes are in the range of 6.99
to 16.16.
Table 3: Color values of VM7(a-c) and VM8(a-c) dyes on polyester fabric.
Dyes
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
L*
a*
b*
K/S
9.46
7.13
6.99
16.16
16.07
9.43
53.444
60.091
57.64
52.39
61.17
63.996
43.372
42.26
40.84
23.025
25.461
22.455
39.412
42.669
40.646
53.434
69.603
58.901
3.3 Fastness properties
From Table 4, it was observed that dye VM7(a-c) and VM8(a-c) display fair to moderate light
fastness on polyester fabric. Furthermore, it exhibits excellent to good wash fastness property on
polyester fabric it may be due to less solubility of dyes in water. Staining on polyester and cotton
fabrics gave an excellent result, as both fabrics remain undyed.
The migration of dye molecules on polyester fabric is totally depended on heat treatment, hence
Sublimation fastness is the most essential property of dyed polyester fabric. From Table 5, it was
o
observed that all dyes exhibit excellent sublimation fastness at 150 C and excellent to good
sublimation fastness at 180 and 210 oC.
Table 4: Light Fastness and Wash fastness property of VM7(a-c) and VM8(a-c) dyes on
polyester fabric.
Dyes
Lightfastness
Wash fastness
Change in color Staining on fabric
VM7a
VM7b
VM7c
VM8a
3
3
1‒2
3
4
4
4‒5
4‒5
4
4
4
4‒5
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VM8b
VM8c
3
1‒2
3‒4
4‒5
3‒4
4
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).
Table 5: Sublimation fastness property of VM7(a-c) and VM8(a-c) dyes on polyester fabric.
Sublimation fastness
150oC
180oC
210oC
Dyes
Staining on fabric
Staining on fabric
Staining on fabric
Cotton
Polyester
Cotton
Polyester
Cotton
Polyester
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
5
5
4‒5
5
5
4‒5
4
5
4‒5
5
5
4‒5
3‒4
5
4
4
4‒5
4
3‒4
4‒5
4
4
4‒5
3‒4
3
5
5
5
5
5
5
5
5
5
5
4‒5
Rating*(1-poor, 2-fair, 3-good, 4-very good, and 5-Excellent).
3.4 Ultraviolet Protecting Factor (UPF)
Textile fabric can reflect, absorb and scatter the harmful UV radiations and it is measured in
terms of UPF [42]. UPF of a fabric is a quantitative measurement of the efficiency of the fabric
to protect the human skin against harmful solar radiation. From, Table 6 it is noticed that all
dyes show a very good UPF rating in a range of 27 to 37 which indicates the transmittance of
4.1-2.6% (i.e. blocking 95.9-97.4%) of the UV radiation. Therefore all dyes act as a very good
UV rays protector for textile material compared to earlier reported dyes [27].
Table 6: Ultraviolet Protecting Factor (UPF) of all dyes.
Dyes
UPF rating
Undyed fabric
VM7a
14.63
31.62
29.76
35.46
27.37
37.14
35.52
25-39
<40
VM7b
VM7c
VM8a
VM8b
VM8c
Very good
Excellent
3.5 Antibacterial Activity
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The disperse azo dyes VM7(a-c) and VM8(a-c) were screened for antibacterial activity against
S.aureus and K. pneumoniae bacterial strains. The activities of dyes were evaluated using agar
well diffusion method and reported in terms of the diameter of the zone of inhibition (cm). The
well diffusion results reveal that all the dyes exhibit excellent to moderate antibacterial activity
towards the tested microbes (see Table 7 and Figure 4).
Table 7: Zone of inhibition (cm) for VM7(a-c) and VM8(a-c) by well diffusion method.
Dyes
Zone of inhibition (cm)
S.aureus K. pneumoniae
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
1.9
1.8
1.7
2.2
2.1
2.2
1.8
1.8
1.5
1.9
1.9
2.0
Note: Diameter of the well is 1cm.
Figure 4: Zone of inhibition for VM7a and VM8a by well diffusion method.
The dyed fabric was screened against S.aureus (AATCC 6538) and K.pneumoniae (AATCC
4352) by both qualitatively and quantitatively using AATCC 147 and AATCC 100 respectively.
From, qualitatively analysis i.e. AATCC 147 it is observed that all dyes show no zone of
inhibition but also there is no bacterial growth below the fabric hence the exhibit antibacterial
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activity (Figure 5). Furthermore, to assess quantitatively the minimum inhibitory concentration
(MIC) was calculated using the AATCC 100 method. It is calculated using equation (2)
(2)
where R is percentage reduction of microorganisms, A is the number of bacteria colonies
recovered after 24 h, and B is the number of bacteria colonies present at 0 h.
From, Table 8 it is observed that all dyed fabric exhibit more than 94% of reduction values
towards both S.aureus (AATCC 6538) and K.pneumoniae (AATCC 4352) (see Figure 6). Dyed
fabric for VM7a and VM8a exhibit maximum inhibitory activity towards microbes.
Figure 5: Antibacterial test for VM7a and VM8a by AATCC 147 against S.aureus Strain no.
AATCC 6538 and K. pneumoniae Strain no. AATCC 4352.
Table 8: Antibacterial Test for VM 7(a-c) and VM 8(a-c) by AATCC 100 against S.aureus
Strain no. AATCC 6538 and K. pneumoniae Strain no. AATCC 4352.
Dyes
Test Culture
No. of colonies No. of colonies
Reduction of
recovered at ‘0’
hr [B]
recovered at
‘24’ hrs [A]
5 X 10^3
8 X 10^3
7 X 10^3
1.1 X 10^4
7 X 10^3
1.1 X 10^4
3 X 10^3
9 X 10^3
4 X 10^3
4 X 10^3
8 X 10^3
1.5 X 10^4
Microorganisms [R]
(%)
S.aureus
K. pneumoniae
S.aureus
K. pneumoniae
S.aureus
K. pneumoniae
S.aureus
K. pneumoniae
S.aureus
1.49 X 10^5
1.67 X 10^5
1.83 X 10^5
1.95 X 10^5
1.96 X 10^5
1.95 X 10^5
1.76 X 10^5
1.87 X 10^5
1.18 X 10^5
1.32 X 10^5
1.92 X 10^5
2.12 X 10^5
96.64
95.20
96.17
94.35
96.42
94.35
98.29
95.18
96.61
96.96
95.83
92.92
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
K. pneumoniae
S.aureus
K. pneumoniae
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Figure 6: Antibacterial test for VM7a and VM8a by AATCC 100 against S.aureus Strain no.
AATCC 6538 and K. pneumoniae Strain no. AATCC 4352.
3.6 Computational Study
3.6.1 Optimized geometry at ground state
Dyes VM7(a-c) and VM8(a-c) can exist in various tautomeric forms as seen in Figure 7, so all
possible forms were optimized at B3LYP/6-31G(d) in the gas phase and seven different solvent
phase to determine the stable conformers. The relative ground state energies of stable tautomeric
forms are listed in supplementary Table (SI Table 1) and it is observed that for dyes VM7(a-c)
azo-enol form are more stable in gas and solvent phase. In the case of dyes VM8(a-c), VM8a
and VM8b exist in azo-enol form, however, VM8c exist in the hydrazone-enol form in polar
solvents whereas in gas phase and remaining solvents azo-enol form predominant. The stable
tautomeric form is further optimized at B3LYP 6-311+G(d,p) for further calculation.
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Figure 7: Possible tautomer for dye VM7(a-c) and VM8(a-c).
3.6.2 Frontier Molecular Orbital
Highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO)
are the most vital orbitals in a molecule. HOMO energy is directly related to ionization potential.
So, molecule easily loses an electron when they are energized. In the case of LUMO, it is
directly accomplice with electron affinity because it accepts an electron. The small energy gap
between frontier orbital of molecules indicates that it is chemically more active and has low
kinetic stability [27,43–45]. From, Table 9 it is witnessed that VM7(a-c) shows almost the same
HOMO-LUMO energy gap. However, for VM8(a-c), VM8a exhibit the lowest HOMO-LUMO
energy gap compared to VM8b and VM8c (see Figure 8). Therefore, VM8a exhibit excellent
antibacterial activity compared to other dyes which are confirmed by the AATCC 100 test
method (see Figure 9).
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Table 9: HOMO-LUMO energy gap of VM7(a-c) and VM8(a-c) in MeOH solvent at B3LYP/6-
311+G(d, p)
Dyes
HOMO Energy LUMO Energy ELUMO-EHOMO
eV
eV
eV
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
-5.49
-5.48
-5.47
-5.48
-5.50
-5.46
-2.67
-2.66
-2.65
-2.48
-2.48
-2.45
2.82
2.82
2.82
3.00
3.02
3.01
Figure 8: HOMO-LUMO energy gap of VM7(a-c) and VM8(a-c) in MeOH solvent at
B3LYP/6-311+G(d, p).
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HOMO-LUMO gap vs Antibacterial
activity
3.02
3.01
3
99
98
97
96
95
2.82
2.82
2.82
3
2.5
2
1.5
1
0.5
0
VM7a
VM7b
VM7c
VM8a VM8b
VM8c
HOMO-LUMO gap
Antibacterial Activity
Figure 9: Correlation of HOMO-LUMO band gap with antibacterial activity (AATCC 100)
3.6.3 Global Reactivity Descriptors
The stable tautomer is optimized at B3LYP/6-311+G(d, p) in gas and solvent phase, the frontier
molecular orbitals EHOMO and ELUMO are used to calculate the Global reactivity descriptor –
chemical potential (μ), chemical hardness (η), global softness (S), electrophilicity index (ω)
given by equations (1-4) [46,47].
μ = -½ (EHOMO+ ELUMO
)
(1)
(2)
(3)
(4)
η = ½ (ELUMO - EHOMO
)
S = 1/ 2η
ω = μ 2/2η
The molecule is stabilized more if the value of ω is more, and hence such molecules exhibit
higher light fastness and better photostability [27,48–50]. From Table 10 it is observed that
value ω for VM7a is more compared to VM7(b-c), a similar observation was visualized in
experimental lightfastness values, the comparable observation was observed for VM8(a-b) also.
Hence VM7a and VM8a exhibit higher lightfastness value and more photostability than other
dyes (see Figure 10).
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Table 10: HOMO and LUMO energies (eV), chemical potential (μ, eV), chemical hardness (η,
eV), electrophilicity index (ω, eV), global softness (S, 1/eV) of all the dyes in MeOH solvent
phase at B3LYP/6-311+G(d, p).
HOMO Energy LUMO Energy
μ
η
ω
Dyes
Light
fastness
3
eV
eV
eV
eV
eV
VM7a
VM7b
VM7c
VM8a
VM8b
VM8c
-5.4956
-5.4758
-5.4670
-5.4809
-5.4959
-5.4551
-2.6732
-2.6629
-2.6531
-2.4806
-2.4749
-2.4482
4.0844
4.0693
4.0601
3.9808
3.9854
3.9516
1.4112
1.4064
1.407
1.5002
1.5105
1.5034
5.9108
5.8871
5.8581
5.2816
5.2576
5.1978
3
1-2
3
3
1-2
Lightfastness vs Electrophilicity index
6
4
2
0
VM7a VM7b VM7c VM8a VM8b VM8c
Light fastness
ω
Figure 10: Comparison of Lightfastness and Electrophilicity index (ω) (in MeOH solvent) for all
the dyes.
4. Conclusion
In this paper, six heterocyclics disperse azo dyes were prepared through the diazo-coupling
reaction. The structures of the dyes prepared were confirmed by FTIR, 1H NMR, 13C NMR, LC-
MS, elemental analysis, UV-visible and fluorescence spectroscopy. The azo dyes showed
absorption maxima in the range of 460-493 nm, whereas dye VM7a and VM8a showed a
bathochromic shift of 90 and 26 nm respectively in a polar aprotic solvent. All dyes are emissive
in a polar aprotic solvent having a Stokes shift of 62 to 180 nm. The disperse dyes were
investigated for their dyeing characteristics on polyester fibers and exhibited moderate light
fastness, excellent to a good wash and sublimation fastness. All the dyes are very good UV ray
17

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protectors for polyester fiber and almost blocking 95 to 98 % of harmful rays. The synthesized
dyes exhibit excellent antibacterial activities. Furthermore, dyed polyester fabric was examined
for antibacterial study by using AATCC 100 and 147 test method. The results indicated that
these dyes exhibit excellent antibacterial activities for polyester fabric. HOMO-LUMO gap and
global reactivity descriptors were calculated from frontier molecular orbitals and correlated it
with antibacterial activity and light fastness property respectively.
Acknowledgment
Authors (VRM and CWG) acknowledge the office of the Principal Scientific Adviser to
Government of India for financial support by way of Junior Research Fellowship and the
Department of Textiles, ICT, Mumbai for allowing to use the facilities for dyeing experiments.
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Graphical abstract
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Highlights
UV Protective Heterocyclic Disperse Azo Dyes: Spectral properties, Dyeing, Potent
Antibacterial activity on dyed fabric and Comparative Computational study
Virendra R. Mishraa, Chaitannya W. Ghanavatkara, Nagaiyan Sekara,*
aVirendra R. Mishra -ORCID ID- https://orcid.org/0000-0003-0070-4705
aChaitannya W. Ghanavatkar -ORCID ID- https://orcid.org/0000-0003-0821-1083
a,*Department of Dyestuff Technology, Institute of Chemical Technology, Matunga (E),
Mumbai, Maharashtra, India, PIN: 400 019.
E-mail: nethi.sekar@gmail.com; n.sekar@ictmumbai.edu.in
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Highlights
 Heterocyclic Disperse Azo dyes were applied on polyester fabric and evaluated it fastness
properties.
 Dyed fabric exhibit excellent to a good wash and sublimation fastness property.
 Dyed fabric showed very good UPF rating and almost blocking 95 to 98 % of harmful
UV radiation.
 Antibacterial studies of dyed fabric were carried by using AATCC 147 and 100 test
method and it exhibit excellent antibacterial activities against “S.aureus” (Gram +ve) and
“K. pneumoniae” (Gram –ve).
 DFT method was used to correlate the experimental findings.
25