Synthesis, characterization of a ternary Cu(II) Schiff base complex with degradation activity of organophosphorus pesticides

Article abstract of DOI:10.1016/j.ica.2017.11.024

Organophosphorus pesticides are a class of the most important groups of insecticides and are widely applied to pest and plant diseases control in agriculture. The extensive application of organophosphorus pesticides can subsequently release organophosphorus pesticides into environment which may pose a seriously adverse impact to non-target organisms and humans. However, we could not ban organophosphorus pesticides at present as they are very efficient. Therefore, the new technique of degradation of organophosphorus pesticides must be studied. In this paper, a ternary copper Schiff base complex 2Cu(C₁₄H₈NO₃Cl)(C₁₂H₈N₂)·3CH₃OH was synthesized and characterised by physico-chemical and spectroscopic methods. The degraded effects of 4 pesticides by the complex were investigated. The results showed that the degraded rates of every organophosphorus pesticide were increased. However, the effects of degradation were varied because of the different molecule structures of organophosphorus pesticides. Gas chromatography-mass spectrometry (GC–MS) and ion chromatography were used to analyze the degradation products by the complex, and then the catalytic mechanism of degradation was proposed. The study results suggest that the Schiff base copper complex, as a potent catalyzer, may find its applications in catalytic degradation area.

Full text of DOI:10.1016/j.ica.2017.11.024

Accepted Manuscript
Research paper
Synthesis, Characterization of a Ternary Cu(II) Schiff Base Complex with Deg-
radation Activity of Organophosphorus Pesticides
Xin Li, Dandan Zhang, Zihui Liu, Ying Xu, Dongfeng Wang
PII:
S0020-1693(17)31387-7
https://doi.org/10.1016/j.ica.2017.11.024
ICA 17994
DOI:
Reference:
Inorganica Chimica Acta
To appear in:
Received Date:
Revised Date:
Accepted Date:
4 September 2017
26 October 2017
13 November 2017
Please cite this article as: X. Li, D. Zhang, Z. Liu, Y. Xu, D. Wang, Synthesis, Characterization of a Ternary Cu(II)
Schiff Base Complex with Degradation Activity of Organophosphorus Pesticides, Inorganica Chimica Acta (2017),
doi: https://doi.org/10.1016/j.ica.2017.11.024
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Synthesis, Characterization of a Ternary Cu(ІІ) Schiff Base Complex
with Degradation Activity of Organophosphorus Pesticides
Xin Li, Dandan Zhang, Zihui Liu, Ying Xu, Dongfeng Wang*
College of Food Science and Engineering, Ocean University of China,
Qingdao, Shandong 266003, P.R. China
Abstract Organophosphorus pesticides are a class of the most important groups of insecticides
and are widely applied to pest and plant diseases control in agriculture. The extensive application
of organophosphorus pesticides can subsequently release organophosphorus pesticides into
environment which may pose a seriously adverse impact to non-target organisms and humans.
However, we could not ban organophosphorus pesticides at present as they are very efficient.
Therefore, the new technique of degradation of organophosphorus pesticides must be studied. In
this paper, a ternary copper Schiff base complex 2Cu(C14H8NO3Cl)(C12H8N2)·3CH3OH was
synthesized and characterised by physico-chemical and spectroscopic methods. The degraded
effects of 4 pesticides by the complex were investigated. The results showed that the degraded
rates of every organophosphorus pesticide were increased. However, the effects of degradation
were varied because of the different molecule structures of organophosphorus pesticides. Gas
chromatography-mass spectrometry (GC-MS) and ion chromatography were used to analyze the
degradation products by the complex, and then the catalytic mechanism of degradation was
proposed. The study results suggest that the Schiff base copper complex, as a potent catalyzer,
may find its applications in catalytic degradation area.
Keywords: Schiff base; complex; degradation activity; molecular docking; mechanism
*Corresponding author:
E-mail address: wangdf105@126.com
Telephone/fax: +86 532 82031575
1

1. Introduction
Organophosphorus pesticides are a class of the most widely used insecticides in the world
and they play a very important role in prevention of pests and plant diseases. However, the
improper use of organophosphorus pesticides makes pesticide residues almost ubiquitously found
in the environment and agricultural products [1]. Organophosphorus pesticides can enter the
human body through the digestive tract, respiratory tract and skin. They inhibit the activity of
cholinesterase in vivo, cause the accumulation of acetylcholine in the nervous system, and
eventually cause the dysfunction of central nervous system. At present, the relatively effective
degradation method is microbial degradation. However, the use of microorganism will affect the
microflora of the environment. Therefore, the safe and rapid degradation of organophosphorus
pesticides is an important research topic to improve the environment and food safety.
Schiff bases are a class of organic compounds that contain carbon and nitrogen double bond
(-C=N-), such as the imine and azomethine group. Due to their efficient catalytic activity, Schiff
bases have attracted wide attention [2-5]. In recent years, the catalytic degradation of metal
complexes is gaining even more popularity in the research community [6]. The metal ions, as the
catalytic center, play a very important role in the process of electron transfer. They are easy to lose
electrons and form empty electronic orbits, which are typical “Lewis Acid”. The metal ions have a
good directive effect on the movement of the various groups in the catalytic process, thus the
activation energy of the catalytic reaction is reduced. Because of the potential catalytic activity,
metal complexes have great research value in the field of pesticides degradation [7].
In this paper, a ternary copper Schiff base complex was synthesized and characterized [8].
The degradation activity of 4 organophosphorus pesticides with different structures of the complex
was investigated and the studies indicated that the complex was capable of degrading
organophosphorus pesticides. Gas chromatography-mass spectrometry (GC-MS) and ion
chromatography were used to analyze the degradation products and the AutoDock software
predicted the binding ability between the complex and pesticides [9]. Finally, the catalytic
mechanism of degradation was proposed. Experiment results demonstrated that the synthetic
complex was of remarkable catalytic capability for pesticides degradation. This novel artificial
catalyzer may find its applications in catalytic degradation area.
2. Experimental
2

2.1 Measurement and reagents
Elemental analyses (C, H, and N) were performed on a model 2400 Perkin Elmer analyzer.
Infrared spectra were recorded as KBr pellets on a Nicolet 170SX spectrometer in the 4000-400
1
cm–1 region. H NMR spectra were recorded on an AVANCE III (600 MHz) spectrometer. The
X-ray diffraction data were collected on an Enraf-Nonius CAD-4 X-ray single-crystal
diffractometer. The degree of degradation was recorded by HP6890 gas chromatograph and
HP5975 mass spectrometer detector. 4-chloroanthranilic acid, salicylaldehyde, copper acetate and
other chemicals were all purchased from Aladdin. 4 typical organophosphorus pesticides were
selected for this study. All of the chemicals were produced by the Sinopharm Chemical Reagent
Limited Company (China).
2.2 Synthesis of the ligand
4-chloroanthranilic acid (0.171 g, 1.0 mmol) was dissolved in 40 mL of methanol, and then
salicylaldehyde (0.122 g, 1.0 mmol) was added dropwise to the solution. The reaction mixture was
heated to 50°C with stirring for 6 h to give a yellow solution. The solution was evaporated to 4 mL
and the yellow powder was precipitated. Elemental Anal Calc (%) for the ligand: C 61.0, H 3.7, N
5.1. Found (%): C 60.9, H 3.7, N 5.1. IR (KBr, cm-1): 1,617 (s), 1,565 (s), 1,466 (m), 1,364 (s),
1,245 (s), 1,117 (m), 1,035 (m), 921 (m), 843 (w), 753 (m), 547 (m), 469 (m). 1H NMR (DMSO,
600 MHz) δ(ppm): 5.02 (s, 1H, -OH); 6.76 (d, 1H, J = 7.8 Hz), 6.84-6.86 (m, 1H), 7.12-7.16 (m,
1H), 7.45 (d, 1H, J = 7.2 Hz), (salicylaldehyde); 7.53 (d, 1H, J = 8.4 Hz), 7.56 (s, 1H), 8.13 (d, 1H,
3

J = 7.2 Hz), (4-chloroanthranilic acid); 8.38 (s, 1H, -CH=N-); 11.11 (s, 1H, -COOH). 13C NMR
(DMSO) δ(ppm): 169.44 (-COOH); 114.52, 122.51, 127.37, 133.04, 140.83, and 155.53
(4-chloroanthranilic acid); 160.13 (-CH=N-); 116.07, 118.51, 121.56, 130.64, 132.53, and 161.17
(salicylaldehyde).
2.3 Synthesis of the complex
The ligand (0.275 g, 1.0 mmol) was dissolved in 20 mL of methanol. The solution of
Cu(OAc)2•H2O (0.199 g, 1.0 mmol) in methanol (30 mL) was added dropwise to the above
solution with stirring for 6 h to give a green precipitate. And then the solution of
1,10-phenathroline (0.198g, 1.0 mmol) in methanol (15 mL) was added dropwise to the above
system and stirred for 6 h at 50°C. The resulting solution was cooled to room temperature and then
filtered. The filtrate was left for slow evaporation at room temperature and then the green crystal
was formed slowly. The synthesis reactions of the ligand and the complex are shown in Scheme 1.
Elemental Anal Calc (%) for the complex: C 58.4, H 3.9, N 7.4. Found (%): C 58.4, H 3.9, N 7.5.
IR (KBr, cm-1): 1,621 (s), 1,589 (s), 1,440 (w), 1,382 (m), 1,347 (m), 1,092 (m), 983 (m), 903 (w),
846 (w), 764 (m), 737 (s), 583 (m), 472 (m). 1H NMR (DMSO, 600 MHz) δ(ppm): 6.85 (d, 1H, J
= 7.2 Hz), 6.92-6.96 (m, 1H), 7.18-7.20 (m, 1H), 7.48 (d, 1H, J = 7.2 Hz); 7.55 (d, 1H, J = 8.4 Hz),
7.58 (s, 1H), 8.17 (d, 1H, J = 8.4 Hz); 8.41 (s, 1H); 7.31-7.33 (m, 2H), 7.63 (s, 2H), 7.99 (d, 2H, J
= 7.2 Hz), 8.79 (d, 2H, J = 7.8 Hz). 13C NMR (DMSO) δ(ppm): 172.01 (-COO); 115.15, 123.86,
128.03, 133.49, 141.18, and 156.25 (4-chloroanthranilic acid); 163.72 (-CH=N-); 115.97, 118.73,
122.05, 130.96, 131.44, and 157.87 (salicylaldehyde); 121.51, 127.62, 129.14, 136.43, 139.02, and
150.03 (1,10-phenathroline).
Scheme 1
2.4 X-ray structure determination
The single crystal with dimensions of 0.45×0.37×0.22 mm was mounted on an Enraf-Nonius
CAD-4 X-ray single-crystal diffractometer. All data were collected at 298(2) K with a
graphite-monochromatized MoKα radiation (λ = 0.71073 Å) by using a ω-2θ scan mode. 2969
reflections intensities with I > 2σ(I) was considered to be observed and used in the subsequent
refinements. The structure was solved by direct methods using SHELXS-97 [10, 11]. The
non-hydrogen atoms were defined by the Fourier synthesis method. Positional and thermal
parameters were refined by the full matrix least-squares method (on F2) to convergence.
4

2.5 The degradation experiments of organophosphorus pesticides
The complex with different mass was added to 0.5 mL organophosphorus pesticides solution
(100 mg/L), and then fixed by buffer solution to 25 mL, respectively. The solution was stirred
evenly and reacted at room temperature (20°C). At periodic intervals, taking 1 mL solution for
testing and analysis.
2.6 The condition of gas chromatography-mass spectrometry
HP6890 gas chromatograph, FPD detector, HP6890 chemical workstation, cyanopropyl
phenyl methyl capillary, carrier gas: high purity nitrogen gas, programmed temperature:
ion source: EI (70 eV), ion source temperature: 230°C.
2.7 The condition of ion chromatography
Dionex AS18 anion separation column column, mobile phase: 50 mmol/L NaOH, flow rate:
0.25 mL/min, injection volume: 10 µL, temperature of chromatographic column: 35°C.
2.8 Molecular docking calculation
The software AutoDock 4.2 was employed to set up and perform blind docking calculations
of the complex binding to organophosphorus pesticides [12]. In order to establish the docking
mode, the structures of the complex and organophosphorus pesticides were optimized by Gaussian
03 software. In the docking analysis, the binding site was assigned to include the entire pesticide
molecule. For each of the docking cases, the lowest energy docked conformation, according to the
AutoDock scoring function, was selected as the binding mode. Visualization of the docked pose
has been done by using the PyMOL molecular graphics program.
3. Results and discussion
3.1 Molecule structure of the complex
The IR spectrum of the Cu(II) complex displays a strong absorption at 1,621 cm–1, which is
assigned to the -CH=N- stretching mode of the Schiff base. Absorpting at 1,589 and 1,382 cm–1
1
are assigned to νas(COO-) and νs(COO-) respectively [13]. On comparing the H NMR spectra of
the Cu(II) complex and the free Schiff base, the signals from hydrogen atoms of -COOH (11.11
ppm) and -OH (5.02 ppm) were absent from the spectrum of the complex, indicating
deprotonation of this group. The crystallographic structural analysis reveals that the Cu(II)
5

complex crystallizes in triclinic crystal system, space group Pī. The crystallographic data and
structure refinement of the complex are given in Table 1. The copper atom is five-coordinate,
being coordinated by the imine nitrogen (-CH=N-), two nitrogen atoms from 1,10-phenanthroline,
the hydroxyl oxygen and the carboxylate oxygen atom. There are four complex molecules and six
free methanol molecules (solvent) in the unit cell. The crystal structure of the complex and the
diagram of the unit cell are shown in Fig. 1 [14, 15].
Table 1.
Fig. 1.
3.2 Degradation rates of organophosphorus pesticides under different conditions
In order to preliminary investigation of the degradation rates with the complex, 4
organophosphorus pesticides were treated with the different conditions. As shown in Fig. 2a,
organophosphorus pesticides were degraded by the complex under different pH. The degradation
rates of all pesticides at pH=1 and 7 were higher than those of pH=3 and 5, and the degradation
rates were the highest at pH=9 and 11. These show that the organophosphorus pesticides are
relatively stable in the weak acid solution, and they are easy to degrade under the condition of
strong acid and alkali. The alkaline condition is more favorable for organophosphorus pesticides
degradation.
As shown in Fig. 2b, with the increase of the reaction time, the degradation rates of all
organophosphorus pesticides gradually increased. When the reactions were 24 hours later, the
degradation rates still increased, however the growth trend became very slow. In Fig. 2c, the
addition of complex also had an effect on the degradation rates of organophosphorus pesticides.
With the addition of the complex, the degradation rates of all organophosphorus pesticides were
greatly improved. However, the degradation rates of 10 mg were not as good as those of 5 mg.
This was because when the addition of the complex was 10 mg, the solution became viscous
obviously, thus inhibiting the normal degradation, resulting in the degradation rates degradation.
The influence of reaction temperature is shown in Fig. 2d, with the increase of the reaction
temperature, the degradation rates of all organophosphorus pesticides gradually increased. This
shows that the degradation rates of organophosphorus pesticides are positively correlated with the
reaction temperature.
In order to test for convenient and efficient in the following experiments, organophosphorus
6

pesticides were treated with 5 mg of the complex at pH 7.0 and room temperature (20°C). To
compare the degradation activity of the ligand and the complex, 4 organophosphorus pesticides
were treated with the ligand. The results showed that the complex had more significant
degradation activity compared with the ligand (Fig. 2e).
Fig. 2.
3.3 Gas chromatogram of organophosphorus pesticides
The standard organophosphorus pesticides were measured by gas chromatography (Fig. 3a
and Table 2). After treatment with the complex for 24 hours, the gas chromatogram was also tested
(Fig. 3b). In contrast to the two gas chromatograms, we found that the peak area of omethoate
decreased most (90±2.5%) and the peak area of chlorpyrifos decreased least (23±1.0%). The
reduction of dichlorvos and dimethoate were 73±1.5% and 69±2.0%, respectively.
Table 2.
Fig. 3.
3.4 Molecular docking of the complex with organophosphorus pesticides
To deepen the understanding of the binding nature of the complex to organophosphorus
pesticides, molecular docking was used to validate the results obtained from the above studies.
The 4 different pesticide molecules were used to establish the binding mode and the
energy-minimized docked pose were illustrated intuitively in Fig. 4. The best docking results are
presented as the binding free energy, listed in Table 3. It is universally accepted that the lower the
relative binding free energy, and the more potent the binding affinity is between the complex and
target molecules [16]. The resulting binding free energy values are negative, suggesting that the
binding events of the complex are spontaneous [17]. The Cu2+ ion can function as “Lewis acid”, it
attacks the oxygen or sulfur atom with negative charges in the phosphate group, causing the
degradation reaction, which leads to the breakage of the pesticide molecule [18]. The binding free
energy of omethoate is the highest, it proves omethoate has the strongest binding ability with the
complex. The results are consistent with the degradation rates obtained from the above
experiments.
Table 3.
Fig. 4.
3.5 Study on degradation of dichlorvos
7

In order to study the degradation mechanism of dichlorvos, GC-MS and ion chromatography
were used to detect the degradation products. Compared to the total ion chromatogram of 0 hour,
after 24 hours of degradation, the peak of dichlorvos (peak 1) decreased significantly and a new
peak (peak 2) was detected (Fig. 5a and 5b). By analyzing the mass spectrum of peak 2, we
determined that the degradation product was dichloro vinyl alcohol (Fig. 5c). At the end of the
chemical reaction, the Cl- and PO34- ions were detected by ion chromatography (Fig. 5d).
On the basis of the experimental detection and the molecular docking, a tentative mechanism
was proposed for the degradation of dichlorvos in the presence of the complex is shown in Fig. 6.
As the center of catalysis, the metal ion plays an important role in the process of electron transfer.
It is easy to lose electrons and form empty orbits, which is typical of “Lewis acid”. The Cu2+ ion
shows a strong activity of Lewis acid, which has more affinity to the rich electronic phosphorus
ester bond. Through the positive charges, the Cu2+ ion neutralizes the electron cloud of the oxygen
atom of P=O bond in the phosphoric acid group. Thus, the electronic distribution of the dichlorvos
molecule is changed, because the electrons move towards the direction of the oxygen atom in P=O
bond. Similarly, chlorine atoms also attract the electrons. These make the P-O bond weak in the
ortho-position, and then leading to water molecules attack the P-O bond in the ortho-position. This
breaks the stable distribution of the charges of the P-O bond, so that the P-O bond is broken [19,
20]. Finally, inorganic small molecules and ions were detected in the reaction solution. In addition
to the complex, there may be other factors that affect the degradation or oxidation of pesticides in
the solution. The generation of these final products requires further studies.
Fig. 5.
Fig. 6.
3.6 Study on degradation of omethoate and dimethoate
Similar to the study of dichlorvos, GC-MS and ion chromatography were also used to detect
the degradation products of omethoate. After 24 hours of degradation, the peak of omethoate (peak
1) decreased significantly and a new peak (peak 2) was detected (Fig. 7a and 7b). By analyzing
the mass spectrum of peak 2, we also determined one of the degradation product of omethoate
-
(Fig. 7c). At the end of the chemical reaction, the NO3 , PO34- and SO42- ions were detected by ion
chromatography (Fig. 7d).
For the degradation of dimethoate, we detected the same degradation product and inorganic
8

ions as omethoate. So we believe that the two pesticides have the same degradation mechanism.
As shown in Fig. 8, the Cu2+ ion still plays the role of “Lewis acid”, it neutralizes the electron
cloud of the oxygen or sulfur atom of P=O or P=S bond in the phosphoric acid group. Thus, the
stable distribution of charges of the pesticide molecule is broken. Because the bonding energy of
P-S bond is less than that of P-O bond, water molecules are easier to attack the P-S bond, resulting
the break of the P-S bond. Finally, inorganic small molecules and ions were detected in both of the
two pesticides solution.
Fig. 7.
Fig. 8.
3.7 Study on degradation of chlorpyrifos
As can be seen from the above experiments, the degradation rate of chlorpyrifos was much
lower than that of other three pesticides. After 24 hours of degradation, there was no obvious
change in the gas chromatogram of chlorpyrifos. At the end of the chemical reaction, only a small
amount of PO34- and SO42- ions were detected by ion chromatography (Fig. 9). This indicated that
the heterocyclic ring of chlorpyrifos was not destroyed. On the basis of molecular docking, the
binding free energy of chlorpyrifos was also the lowest. It was consistent with the degradation
experiments of chlorpyrifos.
Fig. 9.
3.8 The influence of different molecular structures on degradation rates
Most of organophosphorus pesticides are phosphorus esters, so their biochemical properties
depend greatly on the characteristics of esters. Organophosphorus pesticides contain P=O or P=S
bonds, in which the phosphorus atom has positive charge and strong electrical affinity, it is easy to
react with nucleophilic reagents. Because the electronegativity of oxygen atom is greater than that
of sulfur atom, the P=O bond is more easily bound to the complex than the P=S bond. The
bonding energy of P-S bond is less than that of P-O bond, so the P-S bond is more likely to break.
For chlorpyrifos, the presence of the heterocyclic ring greatly increases the steric hindrance of the
degradation reaction. In summary, for these 4 organophosphorus pesticides, omethoate has the
highest degradation rate and chlorpyrifos has the lowest degradation rate in the presence of the
complex.
4. Conclusions
9

In this work, a copper complex with Schiff base derived from 4-chloroanthranilic acid and
salicylaldehyde was synthesized and characterized. The degradation activity of organophosphorus
pesticides in the presence of complex was investigated both theoretically and experimentally. The
results showed that the complex can effectively degrade organophosphorus pesticides with the
specific structure. Finally, we proposed the possible degradation mechanism of organophosphorus
pesticides. The study reinforces the idea that the complex, as a potent artificial catalyzer, has great
potential to be developed into the novel pesticide degradation material.
Acknowledgments
The work was supported by National Natural Science Foundation of China (Grant No.
31371731); the Independent Innovation Major Project of Huangdao District Qingdao City (Grant
No. 2014-3-11); and the Marine Economy Innovation Development Regional Demonstration
Project of Fujian Province (Grant No. 2014FJ10).
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11

Research Highlights:
1. A copper Schiff base complex was synthesized and characterized.
2. Molecular docking was used to study the pesticides degradation.
3. The catalytic mechanism of pesticides degradation was supposed.
12

13

Scheme 1 The synthesis of the Schiff base ligand and the complex.
14

Fig. 1. Molecule structure of the complex and the diagram of the unit cell.
15

Fig. 2. Degradation of 4 pesticides by the complex under different conditions. (a) Degradation of 4
pesticides under different pH (the complex 5 mg, 18 hours and 20°C). (b) Degradation of 4
pesticides for different time (the complex 5 mg, pH 7.0 and 20°C). (c) Degradation of 4 pesticides
by the different amounts of complex (24 hours, pH 7.0 and 20°C). (d) Degradation of 4 pesticides
under different temperature (the complex 5 mg, 24 hours and pH 7.0). (e) Comparison of
degradation activity of the ligand and the complex (5 mg, 24 hours, pH 7.0 and 20°C).
16

Fig. 3. (a) Gas chromatogram of standard organophosphorus pesticides, dichlorvos: 5.552,
omethoate: 9.049, dimethoate: 10.574 and chlorpyrifos: 11.711. (b) Gas chromatogram of
organophosphorus pesticides after treatment with the complex, dichlorvos: 5.550, omethoate:
9.026, dimethoate: 10.565 and chlorpyrifos: 11.701.
17

Fig. 4. Molecular docking of the complex with the organophosphorus pesticides. The interaction
of Cu2+ and P=O or P=S bond is shown as a dashed line. (a) dichlorvos, (b) omethoate, (c)
dimethoate and (d) chlorpyrifos.
18

Fig. 5. (a) Gas chromatography-mass spectrometry of dichlorvos degradation for 0 hour. (b) Gas
chromatography-mass spectrometry of dichlorvos degradation for 24 hours. (c) Mass spectrum of
the degraded product. (d) Ion chromatography of reaction solution for 2 days.
Fig. 6. The possible degradation mechanism of dichlorvos.
19

Fig. 7. (a) Gas chromatography-mass spectrometry of omethoate degradation for 0 hour. (b) Gas
chromatography-mass spectrometry of omethoate degradation for 24 hours. (c) Mass spectrum of
the degraded product. (d) Ion chromatography of reaction solution for 2 days.
Fig. 8. The possible degradation mechanism of omethoate (or dimethoate).
20

Fig. 9. Ion chromatography of chlorpyrifos solution after 2 days reaction.
21

Table 1. Crystallographic data and structure refinement of the complex
Empirical formula
C55H44Cl2Cu2N6O9
Temperature (K)
298(2)
Wavelength (Å)
0.71073
Crystal system and Space group
a (Å), b (Å), c (Å)
α (˚), β (˚), γ (˚)
Triclinic and Pī
8.1253(5), 11.5385(11), 27.964(3)
79.2250(10), 86.591(2), 88.422(2)
Volume (Å3)
2570.6(4)
2
Z
Calculated density (g/cm3)
Absorption coefficient (mm-1)
F(000)
1.461
0.995
1160
Crystal size (mm)
θ range for data collection (˚)
Limiting indices
0.45 × 0.37 × 0.22
2.85 to 25.02
-9 ≤ h ≤ 9
-13 ≤ k ≤ 12
-30 ≤ l ≤ 33
12384 / 8734 [Rint = 0.0453]
96.2
Reflections collected / unique
Completeness to θ = 25.02 (%)
Max. and min. transmission
Data / restraints / parameters
Goodness of fit on F2
0.8108 and 0.6631
8734 / 0 / 670
1.082
A
R1 , wR2B [I > 2σ(I)]
R1 = 0.0909, wR2 = 0.2407
R1 = 0.1600, wR2 = 0.2757
A
R1 , wR2B (all data)
Largest diff. peak and hole (e. Å-3)
0.575 and -1.058
2
2
w = 1 / [σ2 (Fo ) + (0.0975P)2 + 5.1937P ], with P = ( Fo + 2 Fc2 ) / 3.
22

Table 2. Retention time, linear regression equation, correlation coefficient and detection limit of
4 organophosphorus pesticides
Retention time
(min)
Correlation Detection limit
Pesticides
Linear regression equation
coefficient
(µg/L)
Dichlorvos
Omethoate
Dimethoate
Chlorpyrifos
5.552
9.049
y = 1792.6 x - 55.584
y = 299.79 x + 211.86
y = 2685.7 x - 43.782
y = 1948.5 x + 32.478
0.9995
0.011
0.9947
0.9946
0.9955
0.015
0.018
0.014
10.574
11.711
Table 3. The docking results of the complex with organophosphorus pesticides (Kcal/mol)
Dichlorvos
-1.95
Omethoate
-1.78
Dimethoate
-1.58
Chlorpyrifos
-1.24
Vdw_hb_desolv energy
(∆GvdW + hb + desolv
Electrostatic energy
(∆Gelec
Total internal energy
(∆Gtotal
)
-7.69
0.36
0.21
0.36
-9.43
-9.73
0.35
-7.17
0.32
0.19
0.32
-8.56
-3.77
0.29
0.22
0.29
-4.79
)
)
Torsional free energy
(∆Gtor)
0.24
Unbound system's energy
0.35
(∆Gunb
Complex Binding free
energy (∆Gbinding
)
-11.27
)
∆Gbinding = ∆GvdW + hb + desolv + ∆Gelec + ∆Gtotal + ∆Gtor - ∆Gunb
.
23