Design and development of 1,3,4-thiadiazole based potent new nano-fungicides

Article abstract of DOI:10.1016/j.molstruc.2020.128507

Being the important organic reaction intermediates and biological scaffolds, a series of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-amino/methyl-1,3,4-thiadiazoles have been synthesized by suitable synthetic route and characterized by analytical and spectral data. The evaluation of these compounds for their bioefficacy against two phyto-pathogenic fungi revealed their fungicidal potency against Rhizoctonia bataticola (ED₅₀ values, 3.9–300.4 μg/mL) and Rhizoctonia solani (ED₅₀ values, 4.2–228.5 μg/mL). To further augment their fungicidal efficacy, the potent five fungicidal compounds were nano-sized. The protocol for preparing 1,3,4-thiadiazole based nano-fungicide employing polyethylene glycol was developed and standardized. Characterization of nano-forms of 1,3,4-thiadiazole derivatives by particle size analyzer and electron microscopy (TEM) techniques confirmed the <100 nm average particle sizes of all nano-fungicides. The 2–4 times higher fungicidal activity was observed with nano-forms than the corresponding conventional sized 1,3,4-thiadiazole derivatives against phytopathogenic fungi, namely, Rhizoctonia solani and R. bataticola.

Full text of DOI:10.1016/j.molstruc.2020.128507

Journal of Molecular Structure 1219 (2020) 128507
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Design and development of 1,3,4-thiadiazole based potent new nano-
fungicides
,
Suprabhat Pal a, Vikrant Singh a, Rajesh Kumar a *, Robin Gogoi b
a Division of Agricultural Chemicals, ICAR-Indian Agricultural Research Institute, New Delhi, 110 012, India
b Division of Plant Pathology, ICAR-Indian Agricultural Research Institute, New Delhi, 110 012, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Being the important organic reaction intermediates and biological scaffolds, a series of 2-alkyl/aralkyl/
heterocyclyl sulfanyl-5-amino/methyl-1,3,4-thiadiazoles have been synthesized by suitable synthetic
route and characterized by analytical and spectral data. The evaluation of these compounds for their
bioefficacy against two phyto-pathogenic fungi revealed their fungicidal potency against Rhizoctonia
Received 14 October 2019
Received in revised form
3 April 2020
Accepted 21 May 2020
Available online 6 June 2020
bataticola (ED50 values, 3.9e300.4
mg/mL) and Rhizoctonia solani (ED50 values, 4.2e228.5 mg/mL). To
further augment their fungicidal efficacy, the potent five fungicidal compounds were nano-sized. The
protocol for preparing 1,3,4-thiadiazole based nano-fungicide employing polyethylene glycol was
developed and standardized. Characterization of nano-forms of 1,3,4-thiadiazole derivatives by particle
size analyzer and electron microscopy (TEM) techniques confirmed the <100 nm average particle sizes of
all nano-fungicides. The 2e4 times higher fungicidal activity was observed with nano-forms than the
corresponding conventional sized 1,3,4-thiadiazole derivatives against phytopathogenic fungi, namely,
Rhizoctonia solani and R. bataticola.
Keywords:
Disease
Heterocycles
Nanotechnology
Rhizoctonia bataticola
R. solani
© 2020 Published by Elsevier B.V.
1. Introduction
yield losses are due to phyto-pathogenic fungi in different crops.
These phyto-pathogenic fungi are responsible for infecting crops at
The biologically active heterocyclic core,1,3,4-thiadiazole and its
derivatives have been utilized for pharmaceutical, medical and crop
protection applications. 1,3,4-Thiadiazole derivatives are well-
known for their interesting biological properties [1e6] including
antibacterial, antifungal, antitubercular, antiviral, antidiabetic,
anticancer, molluscicidal, antioxidant, antihypertensive and pesti-
cidal activity [7,8].
One of the starting material, 5-methyl-1,3,4-thiadiazole-2-thiol
is a part of well known antibiotic, Cefazolin Sodium. Such a diverse
range of biological properties possessed by 1,3,4-thidiazoles and
their derivatives makes them an ideal candidate to be explored for
their possible use for crop protection. Theoretical assessment [9] of
5-methyl/amino-1,3,4-thiadiazole-2-thiols for fungicide likedness
following the Hao’s rule (Table 1) further affirmed this point.
Globally, infestations of crops by various pests have always been
one of the major concerns in agriculture. Up to fifty per cent of
overall crop yields are lost due to various pests in spite of using
modern crop protection measures [10] and up to twenty per cent
different plant growth stages in the field and cause various plant
diseases, for example, damping off, collar rot, root rot [11]. Among
these, Rhizoctonia solani and R. bataticola are one of the most
devastating soil borne fungi and causes numbers of plant diseases.
In order to exploit the fungicidal potential of thiadiazole group
and to discover new potent fungicidal molecules, synthesis of a
series of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-amino/methyl-
1,3,4-thiadiazoles was taken up followed by their characterization
and fungicidal activity evaluation.
Nano-technological tools [12e22] have been utilized for devel-
oping a number of nano-products [23e40] for diverse applications
in agriculture. Therefore, nano-sizing of potent fungicidal thiadia-
zole derivatives was also carried out followed by their analysis for
particle size and comparative in vitro bioactivity against Rhizoctonia
solani and R. bataticola.
2. Experimental
2.1. Synthesis of 5-methyl/amino-1,3,4-thiadiazole-2-thiol
5-Methyl-1,3,4-thiadiazole-2-thiol was synthesized starting
* Corresponding author.
E-mail address: rajesh_agchem@iari.res.in (R. Kumar).
https://doi.org/10.1016/j.molstruc.2020.128507
0022-2860/© 2020 Published by Elsevier B.V.

2
S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
Table 1
thiol (5 mmol) was added in small lots. The reaction mixture was
stirred and cooled to 10 ꢀC followed by the addition of a solution of
alkyl iodide/bromide or allyl bromide/benzyl chloride (5.5 mmol)
or dibromopropane (2.5 mmol) in ethyl alcohol (20 mL). The re-
action mixture was stirred at ambient temperature for 7e8 h and
thin layer chromatography was used to monitor the progress of
reaction by using the solvent system of 1:1 mixture of hexane and
ethyl acetate. The solid product was obtained which was filtered
followed by washing with water and recrystallization from ethanol/
water.
Theoretical assessment of 5-amino/methyl-1,3,4-thiadiazole-2-thiols for fungicide
likedness.
S. No.
Rule class
Hao rule
1,3,4- Thiadiazoles
1.
2.
3.
4.
5.
6.
MW (mol. wt.)
ꢁ435
ꢁ6
132.21e133.2
0.623e0.975
0e1
2e3
0
CLogP (Hydrophobicity)
HBD (H bond donor)
HBA (H bond acceptor)
RB (Rotating bonds)
Aromatic bonds
ꢁ2
ꢁ6
ꢁ9
ꢁ17
5
2.3. Characterization of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-
substituted-1,3,4-thiadiazoles (1-22)
from ethyl actetate in a multistep synthesis [6]. 5-Amino-1,3,4-
thiadiazole-2-thiol was prepared by using the reported method [8].
The analytical and spectral data were recorded for all the syn-
thesized compounds and utilized for the characterization of the
products.
2.2. Preparation of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-amino/
methyl-1,3,4-thiadiazoles (1-22)
Determination of melting points of synthesized chemicals was
completed using electro thermal melting point apparatus and re-
ported in degrees Celsius without any correction. Thin layer chro-
The title compounds were prepared by following the Scheme 1
To a cold solution (10 ꢀC) of potassium hydroxide (10 mmol) in
absolute ethyl alcohol (50 mL), 5-methyl/amino-1,3,4-thidiazole-2-
matography was accomplished on 200 mm thick aluminium sheets
Scheme 1. Synthesis of thiadiazole derivatives.

S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
3
Table 2
having silica gel 60 F 254 as adsorbent. Different solvent systems
Solvent and polymer used for nano-sizing of thiadiazole derivatives.
were used for developing the TLC plates. Visualization of spots was
carried out under UV-light using the ultra-violet light cabinet.
A Bruker Fourier Transform Infrared Spectrophotometer, Model
alpha was employed and the spectra were recorded in automatic
mode. Nuclear magnetic resonance (NMR) spectra were recorded
on a Bruker Avance II, 400 MHz instrument after dissolving the
samples in deuterated solvents like CCl4/CDCl3/DMSO(d6). Tetra-
Compound No.
Solvents in which active ingredients were soluble
15
16
17
21
9
Dichloromethane
Acetone
Dicholromethane
Dicholromethane
Dicholromethane
methylsilane (TMS) was used as an internal standard (
d0.0).
Chemical shifts were reported in values relative to TMS and the
notations used are (s) singlet, (d) doublet, (t) triplet, (m) multiplet
and (brs) broad singlet.
d
Solution B: A mixture of polyethylene glycol (PEG-400) of mo-
lecular weight 400 (100 mL) and distilled water (20 mL) was pre-
pared in a 1000 mL glass beaker and kept on a magnetic stirrer with
a magnet on it for stirring.
Then the solution A was added dropwise to solution B with
stirring. After complete addition, mixture was stirred again for
30 min or more and kept for evaporation of total amount of solvent
at warm conditions.
2.4. Antifungal activity
The poisoned food technique was followed for antifungal
bioassay of synthesized compounds and reference fungicide hex-
aconazole against soil borne phytopathogenic fungi at different
concentrations. The readymade Potato dextrose agar medium
(39 g) was dissolved in hot distilled water (1000 mL) and auto-
claved alongwith Petri dishes at 120 ꢀC for 30 min. The solutions of
synthesized compounds in Dimethyl sulfoxide (DMSO) were tested
alongwith DMSO (1 mL) as a control. These solutions were added to
the media (65 mL, temperature 40 ꢀC) to get the required con-
2.6. Characterization of nano-sized thiadiazole derivatives
The size of the prepared nano-thiadiazole derivatives was
determined by particle size analysis and transmission electron
microscopy.
Particle size of the prepared nano-sized thiadiazole derivatives
was determined by Zetatrac Microtrac particle size analyser. Nano-
sized chemicals were diluted in various suitable concentrations in
distilled water and micelle size of the aqueous sample was analysed
in the zeta sizer. Background of the instrument was kept zero by
placing distilled water in sample plate before loading of each
sample. Washing of the sample plate was carried out before load
and run of each sample.
centrations of 250,125, 62.5 and 31.25 mg/mL of the test compounds
in the media. The medium was transferred into Petri dishes (9 cm in
diameter) under aseptic conditions in a laminar flow chamber.
After solidification of the media, a 5 mm (diameter) mycelia plug
taken from the actively growing front of the desired pathogenic
fungal strain was then placed in the centre of each treatment plate,
aseptically. Incubation of treated Petri dishes was done at 28 ꢀC
until the completion of fungal growth in the control plates. All
experiments were in quadruplicate for each treatment.
The actual size and internal structure of nano-thiadiazole de-
rivatives was further confirmed by Transmission Electron Micro-
scopy using TEM-JEOLX1011. The PEGylated nano-thiadiazole
2.4.1. Recording of observations
derivatives (5e10 mL) were dropped on a carbon-coated copper grid
The mycelial growths of fungi (cm) in both control (C) and
treated (T) Petri dishes were measured diametrically. The following
formula was used for calculating percentage inhibition of growth
(I):
having mesh size 200e400. After complete drying, the samples
were stained with 2% (w/v) phosphotungstic acid. Digital Micro-
graph and Soft Imaging Viewer software were used to perform the
image capture and analysis, including particle sizing.
Inhibition % ¼ (C - T)/C ꢂ 100.
Abbott’s formula was used for converting the percent inhibition
to corrected percent inhibition for calculation of ED50 values
(effective dose required for 50% inhibition of growth):
corrected inhibition ¼ (I - CF) ꢂ 100/100 - CF.where CF is the
correction factor obtained by the equation.
2.7. Bioefficacy evaluation of nano 1,3,4-thiadiazole derivatives
The synthesized nano thiadiazole derivatives were screened for
their in vitro antifungal potential against Rhizoctonia bataticola and
R. solani.
correction factor (CF) ¼ (D-C) ꢂ 100/C.where D is the diameter
of the Petri dish in cm and C is the diameter of growth of the fungus
in control plates. Statistical Package for Social Sciences (SPSS
version 10.0) software was used to carry out Probit analysis for
3. Results and discussion
Synthesis of title compounds was carried out by following the
Scheme 1 by reacting 5-methyl/amino-1,3,4-thiadiazole-2-thiol
and different alkyl/aralkyl/heterocyclyl halides. The reactions
were completed in 7e8 h. The yield of the compounds ranged from
22.5 to 60.3% and Rf values were in the range of 0.21e0.70 (Table 3).
Characterization of all the synthesized thiadiazole derivatives were
done on the basis of spectral and analytical data (Tables 3e5).
The IR, 1H NMR and 13C NMR spectral data were used to
establish the structures of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-
substituted-1,3,4-thiadiazoles (1-22) (Tables 4 and 5) and to
confirm their formation. As a representative example, IR spectra of
5-methyl-2-methyl sulfanyl-1,3,4-thiadiazole (1) showed CeH
stretching at 2999, 2927, 2849 cmꢃ1 while peaks at 1484 cmꢃ1
was assigned to C]N of thiadiazole ring. In its 1H NMR spectrum,
two signals were observed. The protons of two methyl groups
calculating the ED50 (mg/mL) value from the concentration (mg/mL)
and corresponding corrected percentage inhibition data of each
compound.
2.5. Nano-sizing of synthesized 2-alkyl/aralkyl/heterocyclyl
sulfanyl-5-substituted-1,3,4-thiadiazoles
Various parameters namely, type and amount of solvent and
polymer; concentration of active compound were optimized to
develop the protocol for nano-sizing of potent thiadiazole de-
rivatives and following procedure was finally taken up for prepar-
ing nano-sized thiadiazole derivatives.
Solution A: The 0.5% solution of 1,3,4-thiadiazole derivatives
was made by dissolving them (500 mg) in 100 mL of an suitable
organic solvent (Table 2).
appeared singlet at
d 2.49 (5-methyl group) and 3.33 (S-methyl

4
S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
Table 3
provided in Table 6.
Physico-chemical data of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-substituted-1,3,4-
thiadiazoles (1-22).
3.2. Antifungal activity against Rhizoctonia bataticola
S. No.
Melting point (ꢀC)
*Rf
% Yield
1.
2.
3.
4.
5.
6.
7.
8.
120
129
124
137
129
138
152
159
132
173
170
178e179
136
145
130
140
147
0.36
0.48
0.58
0.33
0.52
0.57
0.52
0.44
0.21
0.26
0.47
0.57
0.53
0.58
0.61
0.63
0.60
0.70
0.61
0.53
0.67
0.59
60.3
47.5
47.1
25.5
44.6
36.1
40.0
33.6
43.7
51.7
30.4
49.3
52.5
50.6
50.0
35.6
47.2
34.4
36.4
49.4
48.8
22.5
The most of test compounds were highly effective against
R. bataticola. The ED50 values of the test compounds ranged from
3.9 to 300.4
ED50 values of seven compounds were below 25
pounds showed ED50 values from 26.2 to 46.9
remaining compounds, ED50 values ranging 66.9e101.7
observed for nine compounds and 300.4 g/mL for the least active
compound. The standard fungicide hexaconzole showed ED50 value
of 4.4 g/mL.
The most active compound against R. bataticola was 2-hexyl
sulfanyl-5-amino-1,3,4-thiadiazole (17), with ED50 value 3.9 g/
mL followed by 2-benzyl sulfanyl-5-methyl-1,3,4-thiadiazoles (10),
with ED50 value, 8.9 g/mL. The other active thiadiazoles were
compounds 21 (ED50 ¼ 10.7 g/mL), 9 (ED50 ¼ 12.6 g/mL), 15
(ED50 ¼ 14.5 g/mL and 16 (ED50 ¼ 18.4 g/mL).
mg/mL with an average of 60.0
m
g/mL (Table 6). The
g/mL. Six com-
g/mL. Out of the
g/mL were
m
m
m
m
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
m
m
m
m
m
157
156
135
159e160
173
m
m
3.3. Structural activity relationship (SAR) studies
Compounds containing 5-amino group on the thiadiazole ring
exhibited
3.9e300.4
a
wide range of antifungal performance (ED50
group). In the 13C NMR spectrum of the same compound four sig-
nals were viewed. Aliphatic carbons of methyl were observed at
mg/mL; Mean ED50 63.0 g/mL) including the both best
m
and worst performer, but out of first six most active compounds
(ED50 3.9e18.6 g/mL), four compounds (17, 21, 15, 16) were from
d
15.64 and 16.74 whle thiadiazolyl carbons appeared at d 165.22
m
and 166.86. The spectral data of the compounds 12, 14 and 21 were
in agreement with the data reported in the literature [41,42].
this group. Compounds containing 5-methyl group on the thia-
diazole ring displayed a narrower range of antifungal activity (ED50
8.9e93.9
mg/mL; Mean ED50 56.9 mg/mL) and lower mean ED50
3.1. Antifungal bioassay
values as compared to 5-amino substituted thiadiazole derivatives.
Among the aliphatic groups attached to the 2-sulfanyl group on
thiadiazole ring, compounds with carbon chain of six carbon atoms
Antifungal evaluation of all the thiadiazole derivatives (1-22)
following the poisoned food technique was carried out against
Rhizoctonia bataticola and R. solani and their ED50 values are
were emerged as best performer (6, ED50 40.3
3.9 g/mL) within this group of compounds.
mg/mL; 17, ED50
m
Table 4
IR and 1H NMR data of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-substituted-1,3,4-thiadiazoles (1-22).
S.
No. N]
IR (cmꢃ1) [C] 1H NMR (DMSO‑d6 d, ppm)
1.
2.
3.
4.
5.
6.
7.
8.
9.
1484
2.49 (s, 3H, 5-CH3), 3.33 (s, 3H, SCH3)
1510
1505
1521
1515
1525
1528
1530
1534
1.32e1.36 (t, 3H, SCH2CH3), 2.46 (s, 3H, 5-CH3), 3.21e3.27 (q, 2H, SCH2CH3)
1.03 (t, 3H, SCH2CH2CH3), 1.75 (m, 2H, SCH2CH2CH3), 2.58 (s, 3H, 5-CH3), 3.25 (t, 2H, SCH2C2H5)
0.94 (t, 3H, S(CH2)3CH3), 1.46 (m, 2H, S(CH2)2CH2CH3), 1.74 (m, 2H, SCH2CH2C2H5), 2.40 (s, 3H, 5-CH3), 3.27 (t, 2H, SCH2C3H7)
0.87 (s, 3H, S(CH2)4CH3), 1.3e1.4 (m, 4H, S(CH2)2CH2CH2CH3), 1.65 (t, 2H, SCH2CH2C3H7), 2.5 (s, 3H, 5-CH3), 3.25 (t, 2H, SCH2eC4H9)
0.96 (t, 3H, S(CH2)5CH3), 1.29e1.31 (m, 6H, S(CH2)2(CH2)3CH3), 1.69 (m, 2H, SCH2CH2C4H9), 2.35 (s, 3H, 5-CH3), 3.19 (t, 2H, SCH2C5H11
)
0.86 (t, 3H, S(CH2)6CH3), 1.25 (m, 8H, S(CH2)2C4H8CH3), 1.69 (m, 2H, SCH2CH2C5H11), 2.48 (s, 3H, 5-CH3), 3.24 (t, 2H, SCH2C6H13
)
0.88 (t, 3H, S(CH2)7CH3), 1.26e1.27 (m, 10H, S(CH2)2C5H10CH3), 1.73 (m, 2H, SCH2CH2C6H13), 2.45 (s, 3H, 5-CH3), 3.25 (t, 2H, SCH2C7H15
2.48 (s, 3H, 5-CH3), 3.76 (d, 2H, SCH2 CH]CH2), 4.5 (d, 2H, S CH2CH]CH2), 7.23 (m, 1H, SCH2CH]CH2)
2.45 (s, 3H, 5-CH3), 4.51 (s, 2H, SCH2C6H5), 7.1e7.2 (m, 5H, SCH2C6H5)
)
10. 1544
11. 1529
12. 1552
13. 1557
14. 1550
15. 1534
16. 1512
17. 1505
18. 1521
2.36 (s, 6H, 5 and 50-CH3), 2.14 (m, 2H, SCH2CH2CH2S), 3.4 (t, 4H, SCH2CH2CH2S)
2.58 (s, 3H, SCH3), 7.09 (s, 2H, 5-NH2)
1.22 (t, 3H, SCH2CH3), 2.97 (m, 2H, SCH2CH3), 7.12 (s, 2H, 5-NH2)
0.96 (t, 3H, S(CH2)2CH3), 1.65 (m, 2H, SCH2CH2CH3), 3.02 (t, 2H, SCH2C2H5), 7.27 (s, 2H, 5-NH2)
1.04 (t, 3H, S(CH2)3CH3), 1.56e1.59 (m, 2H, S(CH2)2CH2CH3), 1.79e1.81 (m, 2H, SCH2CH2C2H5), 3.37 (t, 2H, SCH2C3H7), 7.21 (s, 2H, 5-NH2)
0.97 (s, 3H, S(CH2)4CH3), 1.41e1.49 (m, 4H, S(CH2)2CH2CH2CH3), 1.74 (t, 2H, SCH2CH2C3H7), 3.32 (t, 2H, SCH2eC4H9), 7.17 (s, 2H, 5-NH2)
0.99 (t, 3H, S(CH2)5CH3), 1.32e1.39 (m, 6H, S(CH2)2(CH2)3CH3), 1.76 (m, 2H, SCH2CH2C4H9), 3.29 (t, 2H, SCH2C5H11), 7.21 (s, 2H, 5-NH2)
0.96 (t, 3H, S(CH2)6CH3), 1.42 (m, 2H, S(CH2)5CH2CH3), 1.29 (m, 6H, S(CH2)2(CH2)3C2H5), 1.68 (m, 2H, SCH2CH2C5H11), 3.11 (t, 2H, SCH2C6H13), 7.17 (s,
2H, 5-NH2)
19. 1520
20. 1534
21. 1563
22. 1555
0.94 (t, 3H, S(CH2)7CH3), 1.28e1.38 (m, 10H, S(CH2)2(CH2)5CH3), 1.64 (m, 2H, SCH2CH2C6H13), 3.02 (t, 2H, SCH2C7H15), 7.20 (s, 2H, 5-NH2)
3.8 (d, 2H, SCH2C2H3), 5.15 (d, 2H, SCH2CHCH2), 5.8 (m, 1H, SCH2CHCH2), 7.2 (s, 2H, 5-NH2)
4.07 (s, 2H, SCH2C6H5), 7.23 (s, 2H, 5-NH2), 7.10e7.18 (m, 5H, SCH2C6H5)
2.14 (m, 2H, SCH2CH2CH2S), 3.4 (t, 4H, SCH2CH2CH2S), 7.2 (s, 4H, 5 and 50-NH2)

S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
5
Table 5
13C NMR data of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-substituted-1,3,4-thiadiazoles (1-22).
Compd.
No.
13C NMR (DMSO‑d6 d, ppm)
1.
2.
3.
4.
5.
6.
15.64 (5-CH3), 16.74 (SeCH3), 165.22 (CC]N), 166.86 (SC]N)
14.98 (SeCH2eCH3), 15.64 (5-CH3), 28.63 (SeCH2eCH3), 165.40 (CC]N), 166.67 (SC]N)
13.01 (S-(CH2)2CH3), 15.77 (5-CH3), 22.70 (SeCH2eCH2eCH3), 36.03 (SeCH2eC2H5), 164.77 (CC]N), 166.5 (SC]N)
13.3 (S(CH2)3CH3), 15.3 (5-CH3), 22.8 (SC2H4eCH2eCH3), 30.84 (SeCH2eCH2eC2H5), 33.54 (SeCH2C3H7), 165.35 (CC]N), 165.6 (SC]N)
14.27 (SC4H8CH3), 15.66 (5-CH3), 22.04 (SC3H6CH2CH3), 28.90 (SCH2CH2C3H7), 30.59 (SCH2CH2CH2C2H5), 34.09 (SCH2C4H9), 165.67 (CC]N, SC]N)
14.0 (SC5H10CH3), 15.3 (5-CH3), 23.1 (SC4H8CH2CH3), 28.9 (SC3H6CH2C2H5), 31.8 (SeCH2CH2C4H9), 31.9 (SC2H4CH2C3H7), 34.9 (SCH2C5H11), 165.35 (CC]N),
165.67 (SC]N)
7.
8.
13.23 (SC6H12CH3), 15.62 (5-CH3), 22.44 (SC5H10CH2CH3), 28.55 (SC2H4(CH2)2C3H7), 31.5 (SCH2CH2C5H11), 32.5 (SC4H8CH2C2H5), 34.19 (SeCH2C6H13), 165.57
(SC]N), 165.48 (CC]N)
13.83 (SC7H14CH3), 15.87 (5-CH3), 22.45 (SC6H12CH2CH3), 28.81 (SC2H4CH2CH2C4H9), 29.78 (SC4H8CH2CH2C2H5), 31.43 (SCH2CH2C6H13), 33.9 (SCH2C7H15),
165.66 (SC]N), 164.38 (CC]N)
9.
13.3 (5-CH3), 38.93 (SeCH2eC2H3), 127.83 (SeCH2eCH]CH2), 137.48 (SeCH2eCH]CH2), 169.85 (CC]N), 170.29 (SC]N)
15.61 (5-CH3), 38.23 (SCH2C6H5), 126.3 (4C-phenyl), 127.3 (2 and 6 C-phenyl), 128.5 (3 and 5 C-phenyl), 141.0 (1C-phenyl), 164.96 (CC]N), 165.24 (SC]N)
16.11 (5 and 50-CH3), 29.04 (SCH2CH2CH2S), 32.7 (SCH2CH2CH2S), 165.77 (CC]N), 172.42 (SC]N)
21.49 (SCH3), 165.22 (NC]N), 166.86 (SC]N)
10.
11.
12.
13.
14.
15.
16.
17.
15.6 (SCH2CH3), 27.7 (SCH2CH3), 165.22 (NC]N), 166.86 (SC]N)
13.33 (SC2H4CH3), 22.92 (SCH2CH2CH3), 36.7 (SCH2C2H5), 166.66 (NC]N), 169.9 (SC]N)
13.86 (SC3H6CH3), 21.49 (SC2H4CH2CH3), 31.6 (SCH2CH2C2H5), 34.49 (SCH2C3H7), 167.76 (NC]N), 169.8 (SC]N)
13.69 (SC4H8CH3), 21.58 (SC3H6CH2CH3), 28.70 (SCH2CH2CH2C2H5), 30.05 (CH2CH2C3H7), 34.37 (SCH2C4H9), 165.34 (NC]N), 166.25 (SC]N)
13.98 (SC5H10 CH3), 22.48 (SC4H8CH2CH3), 28.79 (SC3H6CH2C2H5), 29.31 (SC2H4CH2C3H7), 31.23 (SCH2CH2C4H9), 35.21 (SCH2C5H11), 164.93 (NC]N), 168.7
(SC]N)
18.
19.
13.7 (SC6H12CH3), 22.29 (SC5H10CH2CH3), 28.24 (SC4H8CH2C2H5), 29.03 (SC2H4CH2CH2C3H7), 31.25 (SCH2CH2C5H11), 34.668 (SCH2C6H13), 165.55 (NC]N),
168.33 (SC]N)
13.71 (SC7H14CH3), 22.51 (SC6H12CH2CH3), 28.88 (SC5H10CH2C2H5), 29.50 (SC4H8CH2CH2C2H5), 29.02 (SC2H4CH2CH2C4H9), 31.64 (SCH2CH2C6H13), 34.83
(SCH2C7H15), 150.74 (NC]N), 169.88 (SC]N)
20.
21.
22.
39.30 (SeCH2eC2H3), 130.09 (SeCH2eCH]CH2), 134.58 (SeCH2eCH]CH2), 167.43 (CC]N), 170.29 (SC]N)
38.33 (SeCH2eC6H5), 127.77 (4C-phenyl), 128.80 (3 and 5 C-phenyl), 129.31 (2 and 6 C-phenyl), 137.38 (1C-phenyl), 170.23 (CC]N), 170.29 (SC]N)
18.11 (5 and 50-CH3), 31.04 (SCH2CH2CH2S), 38.7 (SCH2CH2CH2S), 169.22 (CC]N), 171.31 (SC]N)
3.4. Antifungal activity against R. solani
amino-1,3,4-thiadiazole ring revealed that compound with car-
bon chain of six carbon atoms was the best performer (17, ED50
All the synthesized thiadiazole derivatives (1-22) were also
4.2 mg/mL). In case of 5-methyl-1,3,4-thiadiazole, 2-sulfanyl butyl
effective against R. solani with ED50 values of 4.2e228.5
the test compounds and mean ED50 of 52.9 g/mL. ED50 value of
18.3 g/mL was observed with the standard fungicide, hexaconzole.
m
g/mL for
groups substitution resulted in highest activity (4, ED50 10.6 mg/
mL).
m
m
The ED50 values of seven compounds were below 25
Nine compounds showed ED50 in the range of 25.6e43.5
m
m
g/mL.
g/mL.
3.6. Docking studies
Out of the remaining compounds, ED50 values ranging
77.3e86.8 g/mL were observed for three compounds and
151.4e228.5 g/mL for another three compounds.
The lowest ED50 of 4.2 g/mL was obtained for compound, 2-
hexyl sulfanyl-5-amino-1,3,4-thiadiazoles (17), due to its highest
antifungal bioactivity with against R. solani. The other good anti-
fungal agents from the series against R. solani were compounds 10
Docking studies of compound 17 was carried out taking Lano-
sterol 14-alpha-demethylase as target enzyme (https://mcule.com/
apps/1-click-docking/). The docking score for the compound 17
was ꢃ5.2 as compared to that of ꢃ6.3 for standard fungicide,
hexaconazole which suggested the possible inhibitory interaction
of thiadiazole derivatives with Lanosterol 14-alpha- demethylase.
m
m
m
(ED50 ¼ 6.2
m
g/mL), 9 (ED50 ¼ 9.3
mg/mL), 4 (ED50 ¼ 10.6
mg/mL) and
16 (ED50 ¼ 14.6
m
g/mL).
3.5. Structure activity relationship studies
.
5-Methyl substituted thiadiazole derivatives (1-11) displayed a
narrower range of antifungal activity (ED50 6.2e151.6 g/mL; Mean
ED50 45.8 g/mL) and lower mean ED50 values as compared to that
of 5-amino substituted thiadiazole derivatives (11e22, ED50
4.2e228.5 g/mL; Mean ED50 60.0 g/mL). Though the best
m
m
m
m
performer belongs to the compounds containing 5-amino group on
the thiadiazole ring, but the first six most active compounds (ED50
3.7. Nano-sizing
3.9e18.6 mg/mL) included four compounds (10, 9, 4, 11) from the 5-
methyl substituted thiadiazole derivatives. Analysis of number of
carbon atoms in the chain attached to the 2-sulfanyl alkyl on 5-
Different parameters namely amount of the active fungicidal
compound, type of polymer, amount of the polymer and solvent

6
S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
Table 6
In vitro antifungal activity of 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-substituted-1,3,4-thiadiazoles (1-22) against Rhizoctonia bataticola and Rhizoctonia solani.
S. No.
R1
R2
Antifungal activity
Rhizoctonia bataticola
Rhizoctonia solani
a
A
B
b
1.
2.
3.
4.
5.
6.
7.
8.
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
CH3
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
n-C7H15
n-C8H17
89.0
66.8
77.3
93.9
86.3
40.3
46.9
77.4
12.6
8.9
0.24
0.19
2.95
3.80
2.90
0.26
1.30
0.97
0.01
0.32
0.87
151.6
77.3
25.6
10.6
36.1
39.4
43.5
84.0
9.3
0.59
0.37
1.27
3.38
3.33
4.40
0.60
0.08
0.24
0.26
0.56
9.
10.
11.
CH2¼CHCH2
C6H5CH2
6.2
19.7
45.8
5-methyl-1,3,4-thiadiazol-2-sulfanyl propyl
26.2
56.9
Mean (1-11)
e
e
12.
13.
14.
15.
16.
17.
18.
19.
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
NH2
CH3
C2H5
n-C3H7
n-C4H9
n-C5H11
n-C6H13
n-C7H15
n-C8H17
300.4
88.4
101.7
14.5
18.4
3.9
21.1
69.85
28.5
10.7
36.0
63.0
1.90
0.66
6.02
0.55
2.00
0.78
0.65
0.51
0.39
0.10
0.39
228.5
151.4
86.8
29.4
14.6
4.2
32.0
27.3
21.8
27.1
36.4
60.0
1.22
2.66
6.91
0.48
0.54
0.34
0.33
0.13
0.68
0.54
0.04
20.
21.
22.
CH2¼CHCH2
C6H5CH2
5-amino-1,3,4-thiadiazol-2-sulfanyl propyl
Mean (12e22)
e
e
Overall Mean (1-22)
60.0
4.4
52.9
18.3
e
e
Hexaconazole
1.20
2.10
e
e
a, ED50 value (mg/mL), calculated from mean percentage inhibition, which is an average of four replicates and its standard deviation ( ) ranged from 0.3 to 4.3; b, chi square
for heterogeneity (tabular value at 0.05 level) ¼ 5.99 (degrees of freedom ¼ 3).
were standardized to optimize the protocol for preparing the nano-
sized thiadiazole derivatives. Polyethylene glycols of different
molecular weight were employed for synthesis of nano-size
chemicals namely, PEG-200, PEG-300, PEG-400, PEG-600 and
PEG-800. Optimum size of chemicals within nano-range was ob-
tained from PEG-400 for all the compounds except compound 6 (2-
octyl sulfanyl-5-amino-1,3,4-thiadiazole) for which PEG-600 was
the most suitable for nano-sizing. Ratio of 5:1 for PEG and water
was optimal for preparing nano-sized thiadiazole derivatives for
0.5% concentration of compounds.
3.9. In-vitro antifungal bioassay against Rhizoctonia bataticola
All the chemicals exhibited good antifungal activity against this
fungus with ED50 of 2.27e18.4
reference fungicide, hexaconazole, showed the ED50 value of 4.4
mL. ED50 values of nano-chemicals ranged from 2.27 to 16.83 g/ml
as compared to their conventional counterparts whose ED50 values
ranged in between 3.9 and 18.4 g/mL. Higher (1.1e4.5 times)
m
g/ml as given in Table 7. The
mg/
m
m
fungicidal activity was observed with nano-chemicals in compari-
son to their conventional 1,3,4-thiadiazoles.
The 2-alkyl/aralkyl/heterocyclyl sulfanyl-5-substituted-1,3,4-
thiadiazoles were nanosized by encapsulating with poly ethylene
glycol-400 or 600. Particle size analysis by zetasizer and Trans-
mission electron microscopy (TEM) studies revealed that average
particle size of nano-thiadiazole derivatives was about 100 nm. No
change in the chemical structure of thiadiazole derivatives was
evident from the presence of peaks due to same functional groups
in the FTIR spectra.
Particle size analysis (Fig. 1) revealed the micelle size in the
range of 76.1e256.3 nm for nano-thiadiazole derivatives. Trans-
mission electron microscopy studies (Fig. 2) confirmed that average
particle size of nano-thiadiazole derivatives was about 100 nm. The
FTIR studies confirmed the presence of thiadiazole derivatives after
their nano-sizing using poly ethylene glycol.
Highest fungicidal activity was demonstrated by 2-(hexyl sul-
fanyl)-5-amino-1,3,4-thiadiazole (17) among the conventional
sized 1,3,4-thiadiazoles. This compound also topped the list with
ED50 of 2.27
mg/mL among the nano-sized 1,3,4-thiadiazole de-
rivatives. Nano-sizing of this chemical resulted in the 1.7 times
enhancement in the antifungal activity of this compound. The next
in performance were 2-(benzyl sulfanyl)-5-amino-1,3,4-thiadiazole
(21), with ED50 value 2.39
thiadiazole (9), with ED50 value 4.79
amino-1,3,4-thiadiazole (15), with ED50 value 10.82
pentyl sulfanyl-5-amino-1,3,4-thiadiazole (16) with ED50 value
16.83 g/mL.
m
g/mL, 2-allyl sulfanyl-5-methyl-1,3,4-
g/mL, 2-butyl sulfanyl-5-
g/mL and 2-
m
m
m
Highest improvement, 4.5 times, in the antifungal activity
against R. bataticola was observed with 2-benzyl sulfanyl-5-amino-
1,3,4-thiadiazole (21) with reduction in ED50 value from 10.7 to
2.39 mg/mL which surpasses the best performer in the conventional
1,3,4-thiadiazole derivatives. In case of nano-sized 2-allyl sulfanyl-
5-methyl-1,3,4-thiadiazoles (9) the increase in the activity was 2.6
folds whereas for the rest of the chemicals it was 1.7 folds or less.
3.8. Comparative antifungal bioassay
1,3,4-Thiadiazole derivatives and corresponding nano-sized
1,3,4-thiadiazole derivatives were tested for in vitro antifungal ac-
tivity against Rhizoctonia bataticola and Rhizoctonia solani. The
bioassay data are depicted in Tables 7 and 8.
3.10. In-vitro antifungal bioassay against Rhizoctonia solani
Bioassay data (Table 8) of all the compounds revealed their ED50

S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
7
Fig. 1. Particle size distribution of nano-form of compound 17.
2-Hexyl sulfanyl-5-amino-1,3,4-thiadiazole (17) also displayed
highest antifungal activity against Rhizoctonia solani as evident
from ED50 value of 4.2
mg/mL. Its nano-sized product showed
slightly higher antifungal activity with ED50 value of 3.83
m
g/mL
demonstrating the marginal improvement in the bioactivity.
Highest reduction, 1.9 times, in the ED50 was observed in case of 2-
allyl sulfanyl-5-methyl-1,3,4-thiadiazole from 9.3 to 4.95
The next in performance was nano 2-pentyl sulfanyl-5-amino-
1,3,4-thiadiazole (16) with ED50 value 11.87 g/mL, followed by
nano 2-benzyl sulfanyl-5-amino-1,3,4-thiadiazoles (21), with ED50
value 17.8 g/mL and nano 2-butyl sulfanyl-5-amino-1,3,4-
thiadiazole (15) with ED50 value 26.6 g/mL.
mg/mL.
m
m
m
Improvement in antifungal activity after nano-sizing against
R. bataticola (1.1e4.5 times) was more as compared to the same
against R. solani (1.1e1.9 times). Improvement in various bio-
activities by nano-sizing [19,23e34] has been exhibited by various
nano-chemicals and nanoencapsulated pesticide formulation
resulting in the lowering of application rate of pesticides and
subsequently posing fewer hazards to environment and human
[35e40]. Choudhury et al. [28] and Gogoi et al. [29] reported nano-
sulphur with an improved fungicidal efficacy against food path-
ogen, Aspergillus niger and Erysiphe cichoracearum causing powdery
mildew of okra (Abelmoschus esculentus Moench). Nanosizing of
hexaconazole [30,31] using polymer encapsulation augmented its
fungicidal potential two times as compared to conventional sized
commercial hexaconazole and also resulted in better biosafety.
Pyridalyl nanocapsule suspension [32e34] has been found effective
for the control of tomato fruit and shoot borer (Helicoverpa
armigera).
Fig. 2. TEM image for nano-form of compound 17.
values in the range of 3.83e29.4
m
g/mL against Rhizoctonia solani.
The reference fungicide, hexaconazole, showed the ED50 value of
18.3
ED50 values of nano-sized chemicals were 3.83e26.4
compared to ED50 values of 4.2e29.4 g/mL for conventional
mg/mL.
mg/ml as
m
thiadiazole derivatives. The performance of nano-chemicals was
better than conventional 1,3,4-thiadiazole derivatives. Antifungal
activity was improved by 1.1e1.9 times by nano-sizing of 1,3,4-
thiadiazole derivatives.
Table 7
Antifungal activity against Rhizoctonia bataticola.
Compound No.
ED50
(m
g/ml)
Increase in activity by nano-sizing (times)
R1
R2
Conventional
Nano-sized
15
16
17
21
NH2
NH2
NH2
NH2
CH3
n-C4H9
n-C5H11
n-C6H13
C6H5CH2
CH2¼CHCH2
14.5
18.4
3.9
10.7
12.6
4.4
10.82
16.83
2.27
2.39
4.79
1.3
1.1
1.7
4.5
2.6
9
Hexaconazole

8
S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
Table 8
Antifungal activity against Rhizoctonia solani.
Compound No.
ED50
(m
g/ml)
Increase in activity by nano-sizing (times)
R1
R2
Conventional
Nano-sized
15
16
17
21
NH2
NH2
NH2
NH2
CH3
n-C4H9
n-C5H11
n-C6H13
C6H5CH2
CH2¼CHCH2
29.4
14.6
4.2
27.1
9.3
26.6
11.87
3.83
17.8
4.95
1.1
1.2
1.1
1.5
1.9
9
Hexaconazole
18.3
4. Conclusion
Contribution No. 1193 from Division of Agricultural Chemicals, ICAR
- Indian Agricultural Research Institute, New Delhi, India.
Twenty
two,
2-alkyl/aralkyl/heterocyclyl
sulfanyl-5-
substituted-1,3,4-thiadiazoles (1-22) were synthesized in moder-
ate yields. All the synthesized thiadiazole derivatives were char-
acterized by IR and NMR spectra and taken up for bioassay studies.
Methyl substitution at 5-position in the thiadiazole ring (1-11)
References
[1] M. Kidwai, R. Kumar, Microwave-assisted synthesis of 1, 3, 4-thiadiazolyl-
substituted 1, 2, 4, 5-tetrazines, pyridazinones, 1, 2, 4-triazoles, 4-
thiazolidinones, oxazoles and thiazoles, Gazz. Chim. Ital. 127 (1997) 263e267.
[2] M. Kidwai, R. Kumar, Y. Goel, Microwave-assisted synthesis of novel biologi-
cally active organomercurials, Main Gr, Met. Chem. 20 (1997) 367e372,
https://doi.org/10.1515/MGMC.1997.20.6.367.
[3] M. Kidwai, K.R. Bhushan, P. Kumar, R. Kumar, Synthesis of novel fungicidal
organomercurials using microwaves, Monatsh. Chem. 128 (1997) 1291e1295,
https://doi.org/10.1007/BF00807262.
resulted in the better antifungal activity (ED50 6.2e151.6
Mean ED50 45.8 g/mL) as compared to the antifungal performance
of amino substitution at 5-postion in thiadiazole ring (11e22, ED50
4.2e228.5 g/mL; Mean ED50 60.0 g/mL). Among the first six most
active compounds (ED50 3.9e18.6 g/mL), four compounds (10, 9, 4,
mg/mL;
m
m
m
m
11) are 5-methyl substituted thiadiazole derivatives. Among the 2-
sulfanyl alkyl groups in the 5-amino-1,3,4-thiadiazole ring, 2-
sulfanyl hexyl group substitution resulted in the highest anti-
[4] M. Kidwai, R. Kumar, A. Srivastava, H.P. Gupta, Microwave-assisted synthesis
of novel 1,3,4-thiadiazolyl-substituted-1,2,4-triazines as potential antituber-
cular agents, Bioorg. Chem. 26 (1998) 289e294, https://doi.org/10.1006/
bioo.1998.1108.
[5] R. Kumar, B.S. Parmar S. Walia, S. Saha, Nitrification inhibitors: classes and its
use in nitrification management, in: A. Rakshit, H.B. Singh, A. Sen (Eds.),
Nutrient Use Efficiency: from Basics to Advances, 2015, pp. 103e122, https://
doi.org/10.1007/978-81-322-2169-2_8. Springer India.
[6] A. Saha, R. Kumar, C. Devakumar, Green synthesis of 5-substituted-1,3,4-
thiadiazole-2-thiols as new potent nitrification inhibitors, J. Heterocycl.
Chem. 47 (2010) 838e845, https://doi.org/10.1002/jhet.345.
[7] N. Aggarwal, R. Kumar, P. Dureja, J.M. Khurana, Synthesis of novel nalidixic
acid-based 1,3,4-thiadiazole and 1,3,4-oxadiazole derivatives as potent anti-
bacterial agents, Chem. Biol. Drug Des. 79 (2012) 384e397, https://doi.org/
10.1111/j.1747-0285.2011.01316.x.
[8] Y. Hu, C.Y. Li, X.M. Wang, Y.H. Yang, H.L. Zhu, 1,3,4-Thiadiazole: synthesis,
reactions, and applications in medicinal, agricultural, and materials chemistry,
Chem. Rev. 114 (10) (2014) 5572e5610, https://doi.org/10.1021/cr400131u.
[9] S. Avram, S. Funar-Timofei, A. Borota, S.R. Chennamaneni, A.K. Manchala,
S. Muresan, Quantitative estimation of pesticide-likeness for agrochemical
discovery, J. Cheminf. 6 (2014), https://doi.org/10.1186/s13321-014-0042-6,
42.
[10] C. Devakumar, R. Kumar, Agro-biochemicals in agriculture, in: S. Ayyappan,
P. Chandra, S.K. Tandon (Eds.), ICAR-Industry Meet e Agricultural Trans-
formation through Public-Private Partnership: an Interface. Directorate of
Information and Publication of Agriculture, Indian Council of Agricultural
Research, 2007, pp. 55e62. New Delhi, India.
fungal activity (17, ED50 4.2
thiadiazoles, 2-sulfanyl butyl groups substitution resulted in
highest activity (4, ED50 10.6 g/mL).
mg/mL). In case of 5-methyl-1,3,4-
m
All the nano-sized compounds performed better than their
conventional (9, 15, 16, 17, 21) thiadiazole derivatives. ED50 values
of nano-chemicals were in the range of 2.27e16.83
compared to conventional chemicals with ED50 values in the range
of 3.9e18.4 g/mL against Rhizoctonia bataticola. ED50 values
against R solani for conventional and nano-range chemicals were
4.2e29.4 g/mL and 3.83e26.6 g/mL respectively. Nano-sized 2-
mg/ml as
m
m
m
hexyl sulfanyl-5-amino-1,3,4-thiadiazole (17) showed highest ac-
tivity against both the fungi (ED50 against Rhizoctonia bataticola
was 2.27 mg/mL and against Rhizoctonia solani was 3.9 mg/mL) than
conventional compounds as well as commercial hexaconazole. The
study revealed the nano-thiadiazole derivatives with improved
antifungal bioactivity to be taken up as suitable antifungal
compounds.
[11] N. Aggarwal, R. Kumar, P. Dureja, D.S. Rawat, Schiff bases as potential fungi-
cides and nitrification inhibitors, J. Agric. Food Chem. 57 (2009) 8520e8525,
https://doi.org/10.1021/jf902035w.
Declaration of competing interest
[12] R. Bheemaraya, R. Gogoi, R. Aggarwal, S.N. Kumar, F. Rai, I.S. Hossain, Bisht,
Effect of Nano-hexaconazole on the Phenotype and Pathogenicity of Rhizoc-
tonia solani f. sp. sasakii causing banded leaf and sheath blight in maize, J. Pure
Appl. Microbiol. 8 (2014) 4579e4592.
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
[13] M. Gopal, R. Gogoi, C. Srivastava, R. Kumar, P.K. Singh, K.K. Nair, S. Yadav,
A. Goswami, Nanotechnology and its Application in Plant Protection, in Plant
Pathology in India: Vision 2030, Indian Phytopathological Society, Division of
Plant Pathology, IARI, New Delhi, 2011, pp. 224e232.
CRediT authorship contribution statement
[14] M. Gopal, R. Kumar, A. Goswami, Nano-pesticides-A recent approach for pest
control, J. Plant Prot. Sci. 4 (2012) 1e7.
[15] M. Gopal, C. Srivastava, R. Gogoi, R. Kumar, A. Goswami, Addressing envi-
ronmental concern with nano pesticides for sustainable agriculture, Int. J.
Suprabhat Pal: Investigation, Writing - original draft. Vikrant
Singh: Investigation. Rajesh Kumar: Conceptualization, Method-
ology, Supervision, Writing - review & editing. Robin Gogoi:
Supervision.
Environ. Sustain.
8 (2012) 115e130, https://doi.org/10.18848/2325-1077/
CGP/v08i01/55039.
[16] J. Hayles, L. Johnson, C. Worthley, D. Losic, Nanopesticides: A review of current
research and perspectives, New Pesticides and Soil Sensors, 193e225. https://
doi.org/10.1016/B978-0-12-804299-1.00006-0...
Acknowledgements
[17] D.Y. Kim, A. Kadam, S. Shinde, R.G. Saratale, J. Patra, G. Ghodake, Recent de-
velopments in nanotechnology transforming the agricultural sector: a tran-
sition replete with opportunities,, J. Sci. Food Agric. 98 (2018) 849e864,
https://doi.org/10.1002/jsfa.8749.
The authors thank the Director and Dean, ICAR - Indian Agri-
cultural Research Institute, New Delhi, India for financial assistance
and providing necessary facilities to carry out the research work.
[18] R. Kumar, K.K. Nair, M.I. Alam, R. Gogoi, P.K. Singh, C. Srivastava, M. Gopal,

S. Pal et al. / Journal of Molecular Structure 1219 (2020) 128507
9
A. Goswami, Development and quality control of nanohexaconazole as an
effective fungicide and its biosafety studies on soil nitifiers, J. Nanosci.
Nanotechnol. 15 (2015) 1350e1356, https://doi.org/10.1166/jnn.2015.9088.
[19] N. Kumar, R. Kumar, N.A. Shakil, T.K. Das, Nanoformulations of Pretilachlor
herbicide: preparation, characterization and activity, J. Sci. Ind. Res. 75 (2016)
676e680.
171e175, https://doi.org/10.4172/2157-7471.1000171.
[30] R. Kumar, M. Gopal, S. Verma, K.K. Nair, R. Gogoi, S. Kulanthaivel, P.K. Singh,
C. Srivastava, A. Goswami, Influence of nanohexaconazole on ergosterol
biosynthesis in Rhizoctonia solani kuhn and molecular characterization of
sclerotial fungi, Adv. Sci. Eng. Med.
10.1166/asem.2017.1970.
9 (2017) 122e129, https://doi.org/
[20] K.K. Nair, W.A. Siddiqi, R. Kumar, R. Niwas, R. Gogoi, C. Srivastava, M. Gopal,
Sensitive and rapid determination of elemental nanosulfur/sulfur by liquid
chromatography, J. Separ. Sci. 37 (9e10) (2014) 1126e1133, https://doi.org/
10.1002/jssc.201300927.
[31] R. Kumar, M. Gopal, S. Pabbi, S. Paul, M.I. Alam, S. Yadav, K.K. Nair, N. Chauhan,
C. Srivastava, R. Gogoi, P.K. Singh, A. Goswami, Effect of nanohexaconazole on
nitrogen fixing blue green algae and bacteria, J. Nanosci. Nanotechnol. 16
(2016) 643e647, https://doi.org/10.1166/jnn.2016.10901.
[21] P. Patra, S.R. Choudhury, S. Mandal, A. Basu, A. Goswami, R. Gogoi,
C. Srivastava, R. Kumar, M. Gopal, Effect Sulfur and ZnO Nanoparticles on
Stress Physiology and Plant (Vigna Radiata) Nutrition, in: P.K. Giri,
D.K. Goswami, A. Perumal (Eds.), Advanced Nanomaterials and Nanotech-
nology, Springer, 2013, pp. 301e309, https://doi.org/10.1007/978-3-642-
34216-5_31.
[22] P. Patra, I. Roy, R. Kumar, M. Gopal, C. Devakumar, R. Gogoi, C. Srivastava,
B.S. Subramanium, A. Goswami, Characterization of nanocomposites in flyash
for possible pesticide application, AIP Conf. Proc. 1276 (2010) 144e147,
https://doi.org/10.1063/1.3504279.
[32] P. Saini, M. Gopal, R. Kumar, C. Srivastava, R. Gogoi, Comparative insecticidal
activity of a commercial and a nanoformulation of pyridalyl against bollworm,
Helicoverpa armigera (Hubner), Pestic. Res. J. 25 (2013) 191e194.
[33] P. Saini, M. Gopal, R. Kumar, R. Gogoi, C. Srivastava, Bioefficacy evaluation and
dissipation pattern of nanoformulation versus commercial formulation of
pyridalyl in tomato (Solanum lycopersicum), Environ. Monit. Assess, 187 541
(2015), https://doi.org/10.1007/s10661-015-4767-0.
[34] P. Saini, M. Gopal, R. Kumar, C. Srivastava, Development of pyridalyl nano-
capsule suspension for efficient management of tomato fruit and shoot borer
(Helicoverpa armigera), J. Environ. Sci. Heal. Part B 49, 2014, pp. 344e351.
https://doi.org/10.1080/03601234.2014.882168.
[23] M. Ali, K.K. Nair, R. Kumar, M. Gopal, C. Srivastava, W.A. Siddiqi, Development
and evaluation of chitosan-sodium alginate based etofenprox as nano-
pesticide, Adv. Sci. Eng. Med. 9 (2017) 137e143, https://doi.org/10.1166/
asem.2017.1974.
[35] X. Zhao, H. Cui, Y. Wang, C. Sun, B. Cui, Z. Zeng, Development strategies and
prospects of nano-based smart pesticide formulation, J. Agric. Food Chem. 66
(2018) 6504e6512, https://doi.org/10.1021/acs.jafc.7b02004.
[24] N. Chauhan, N. Dilbaghi, M. Gopal, R. Kumar, K.H. Kim, S. Kumar, Development
of chitosan nanocapsules for the controlled release of hexaconazole, Int. J. Biol.
[36] F. Liu, L.X. Wen, Z.Z. Li, W. Yu, H.Y. Sun, J.F. Chen, Porous hollow silica
nanoparticles as controlled delivery system for water-soluble pesticide,
Mater. Res. Bull. 41 (2006) 2268e2275, https://doi.org/10.1016/
j.materresbull.2006.04.014.
Macromol.
97
(2017)
616e624,
https://doi.org/10.1016/
j.ijbiomac.2016.12.059.
[25] R. Kumar, K.K. Nair, S. Verma, R. Gogoi, P.K. Singh, C. Srivastava, Alpana, M.
Gopal, S.R. Choudhary, A. Goswami, Developing nanosulphur for mitigation of
agricultural pests and better crop health, Int. J. Appl. Agric. Res. 7 (2012)
87e90.
[26] S. Kumar, N. Chauhan, M. Gopal, R. Kumar, N. Dilbaghi, Development and
evaluation of alginate-chitosan nanocapsules for controlled release of acet-
amiprid, Int. J. Biol. Macromol. 81 (2015) 631e637, https://doi.org/10.1016/
j.ijbiomac.2015.08.062.
[37] A. Gogos, K. Knauer, T.D. Bucheli, Nanomaterials in plant protection and
fertilization: current state, foreseen applications, and research priorities,
J. Agric. Food Chem. 60 (2012) 9781e9792, https://doi.org/10.1021/jf302154y.
[38] M. Kah, T. Hofmann, Nanopesticide research: current trends and future pri-
orities, Environ. Int. 63 (2014) 224e235, https://doi.org/10.1016/
j.envint.2013.11.015.
[39] M. Nuruzzaman, M.M. Rahman, Y. Liu, R. Naidu, Nanoencapsulation, nano-
guard for pesticides:
a new window for safe application,, J. Agric. Food
[27] P. Mondal, R. Kumar, R. Gogoi, Azomethine based nano-chemicals: develop-
ment, in vitro and in vivo fungicidal evaluation against Sclerotium rolfsii,
Rhizoctonia bataticola and Rhizoctonia solani, Bioorg. Chem. 70 (2017)
153e162, https://doi.org/10.1016/j.bioorg.2016.12.006.
[28] S.R. Choudhury, K.K. Nair, R. Kumar, R. Gogoi, C. Srivastava, M. Gopal, Sub-
hramanyam BS, goswami A, nanosulfur: potent fungicide against food path-
ogen, Aspergillus niger, AIP Conf. Proc. 1276 (2010) 154e157, https://doi.org/
10.1063/1.3504287.
[29] R. Gogoi, P.K. Singh, R. Kumar, K.K. Nair, M.I. Alam, C. Srivastava, S. Yadav,
M. Gopal, S.R. Choudhury, A. Goswami, Suitability of nano-sulphur for bio-
rational management of powdery mildew of okra (Abelmoschus esculentus
Moench) caused by Erysiphe cichoracearum, J. Plant Pathol. Microbiol. 4 (2013)
Chem. 64 (2016) 1447e1483, https://doi.org/10.1021/acs.jafc.5b05214.
[40] M. Kah, R.S. Kookana, A. Gogos, T.D. Bucheli, A critical evaluation of nano-
pesticides and nanofertilizers against their conventional analogues, Nat.
Nanotechnol. 13 (2018) 677e684, https://doi.org/10.1038/s41565-018-0131-
1.
[41] Y. Hu, C.Y. Li, X.M. Wang, Y.H. Yang, H.L. Zhu, 1,3,4-Thiadiazole: synthesis,
reactions, and applications in medicinal, agricultural, and materials chemistry,
Chem. Rev. 114 (2014) 5572e5610, https://doi.org/10.1021/cr400131u.
[42] F. Clerici, D. Pocar, M. Guido, A. Loche, V. Perlini, M. Brufani, Synthesis of 2-
amino-5-sulfanyl-1,3,4-thiadiazole derivatives and evaluation of their anti-
depressant and anxiolytic activity, J. Med. Chem. 44 (2001) 931e936, https://
doi.org/10.1021/jm001027w.