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Structure, anticorrosion and antibacterial evaluation of
(E)-3-(N-oxide-methylimino)indolin-2-one
Hua-rui Hao1 , Cheng-hu Xue1 , Zhi- fang Zhang1 , Gang Chen2 *
1
School of Chemistry and Chemical Engineering, Yulin University, Yulin 719000, People’s
Republic of China
2
College of Chemistry and Chemical Engineering, Xi’an Shiyou University, Xi’an 710065,
China
*Corresponding author: [email protected]
Abstract: A nitrone, 3-(4-hydroxyphenylimino)indolin-2-one, was synthesized and analyzed
by X-ray single crystal analysis. The inhibition and the mechanism of the title compound on
the corrosion of high protective Q235A steel in HCl solution were screened and discussed by
weight loss and electrochemical measurements. The results indicated that it can inhibit the
corrosion with moderate inhibition efficiency in different conditions, and the inhibition
mechanism of the corrosion inhibiting may be mainly contributed to the adsorption. It was
screened for antibacterial activity against oilfield water-borne bacteria, and it showed good to
moderate activity against sulfate reducing bacteria.
Keywords: isatin; nitrone; corrosion inhibition; adsorption; microbiologically influenced
corrosion
Introduction
Nitrone have been largely employed in organic chemistry. The importance of the nitrone
functionality has been revealed by the growing number of scientific papers which appeared in
the literature over the last years concerning nitrones and related compounds. Nitrones are
easily prepared by several methods well-documented in the primary literature. The most used
includes condensation reactions between carbonyl compounds and oxidation of amines,
imines or hydroxylamines.
Isatin is a compound found in Strobilanthes cusia (Nees) Kuntze and many other plants
such as genus Isatis, Calanthe discolor LINDL, Couroupita guianensis Aubl. and in
mammalian tissue[1]. It has versatile bioactivity and it is used to synthesize a large variety of
heterocyclic compounds in preparing drugs[3,4]. Isatin Schiff bases are reported to have
antibacterial activity against Bacillus subtilis], Gram(+) and Gram(−) bacterial strains and
Magnaporthe grisea[5,6] among others. The compound has been produced industrially and
can thus be used for large-scale applications such as treating oilfield water before re- injection.
Compounds, containing functional electronegative groups and p and/or π-electron in
triple or conjugated double bonds, are found to be efficient as inhibitors against metal
corrosion [7,8]. It has been commonly recognized that an organic inhibitor usually promotes
formation of a chelate on a metal surface, by transferring p and/or π-electrons from the
organic compounds to the metal and forming a coordinate covalent bond during the chemical
adsorption[9-11]. Organic compounds, containing heteroatoms, such as sulfur, phosphorus,
nitrogen and oxygen, together with aromatic rings in their structure are the major adsorption
centers, and the Schiff bases, a condensation product of an amine and a ketone/aldehyde, are
such typical molecules [12-14]. Some polydentate Schiff base compounds (PSCs) have been
reported as effective corrosion inhibitors for various metals in acid media [13,15-17]. Several
isatin derivatives have been reported as inhibitors in HCl solution[18-20], the aim of this
work is to screen the inhibition of a nitrone, (E)-3-(N-oxide- methylimino)indolin-2-one, for
the corrosion of mild steel both in high concentrated HCl solution and microbiologically
influenced corrosion.
Experime ntal
Synthesis of (E)-3-(N-oxide- methylimino)indolin-2-one
(E)-3-(N-oxide- methylimino)indolin-2-one was synthesized according to published methods
(as shown in Scheme 1) [21,22]. Isatin (1 mmol) was dissolved in methanol (20 ml), 10 ml
methanol solution of 1.2 mmol N- methyl- hydroxylamine was added dropwise. The mixture
was refluxed for 1 h, until the disappearance of isatin, as evidenced by thin- layer
chromatography. The solvent was removed in vacuo and the residue was separated by column
chromatography (silica gel, petroleum ether/ethyl acetate = 1:1 v/v), to give the title
compound. Natural evaporation gave yellow single crystals of the title compound suitable for
X-ray analysis over a period of 4 d.
X-ray Data Collection and Structure Refinement
Intensity data for colorless crystals of compound 4 was collected at 150 K on a Bruker
SMART 1000 CCD fitted with Mo Ka radiation. The data sets were corrected for absorption
based on multiple scans and reduced using standard methods. The structures was solved by
direct- methods[13] and refined by a full- matrix leastsquares procedure on F2 with anisotropic
displacement parameters for non-hydrogen atoms, carbon-and nitrogen bound hydrogen
atoms in their calculated positions and a weighting scheme of the form w = 1/[σ2 (Fo 2 ) + (αP)2
+ bP] where P = (Fo 2 + 2Fc2 )/3). All hydrogen atoms were positioned geometrically and
allowed to ride on their parent atoms, with d(N—H)=0.86 Å and Uiso(H)=1.2 Ueq(N),
d(C—H)=0.93 or 0.96 (CH3) Å and Uiso(H)=1.2 Ueq(C) or 1.5 Ueq(C). Crystal data and
refinement details were given in Table 1.
Gravimetric measurements
The corrosion tests were performed on Q235A with a composition (in wt.%) C: 0.22, P: 0.045,
Si: 0.35, S: 0.05, Mn: 1.40, and Fe balance. The electrolyte solution was 2M HCl, prepared
from analytical grade 38% HCl and distilled water. The concentration range of
3-(4-hydroxyphenylimino)indolin-2-one was employed as 100 mg/L and 1000 mg/L. All tests
have been performed in deaerated solutions and at 60 ± 0.5℃. The gravimetric tests were
carried out according to the People's Republic of China Standard of Petroleum and Natural
Gas Industry (Evaluation method for behavior of corrosion inhibitor for produced water of
oilfield, SY/T5273-2000) with a few modifications. Each test was done with three specimens
at the same time to give reproducible results.
Electrochemical measurements
The electrodes were mechanically abraded with a series of emery papers (800 and 1,200
grades), then rinsed in acetone and double-distilled water before their immersion in the
experimental solution. Electrochemical measurements were conducted in a conventional
three-electrode thermostated cell. The electrode was inserted into a Teflon tube and isolated
with polyester so that only its section (0.5 cm2 ) was allowed to contact the aggressive
solutions. A platinum disk as counter electrode and standard calomel electrode (SCE) as the
reference electrode have been used in the electrochemical studies.
The potentiodynamic curves were recorded using a CS350 system connected to a personal
computer. The working electrode was first immersed in the test solution for 60 min to
establish a steady state open circuit potential. After measuring the open circuit, potential
dynamic polarization curves were obtained with a scan rate of 0.5 mV/s. Corrosion rates
(corrosion current densities) were obtained from the polarization curves by linear
extrapolation of the anodic and cathodic branches of the Tafel plots at points 100 mV more
positive and more negative than the Ecorr.
Scanning electron microscopy (SEM)
The surface morphology of the sample under study in the absence and presence of inhibitors
was investigating using a Digital Microscope Imaging scanning electron microscope (model
SU6600, serial no. HI-2102-0003) at accelerating voltage of 20.0 kV. Sampleswere attached
on the top of an aluminum stopper by means of carbon conductive adhesive tape. All
micrographs of the specimen were taken at 5009 magnification.
Microbiological monitoring
Viable counts of SRB, TGB and FB were determined with the ―most probable number‖
method, People’s Republic of China Standard of Petroleum and Natural Gas Industry, the
national method of the bactericidal agent’s performance, SY/T 5890-1993). The produced
water containing the three kinds of bacteria was gathered from Zichang Oilfield Factory,
Yanchang Oilfield.
Results and discussion
Structure
The X-ray structural analysis confirmed the assignment of its structure from spectroscopic
data. Geometric parameters of (E)-3-(N-oxide- methylimino)indolin- 2-one are in the usual
ranges. The atomic coordinates are displayed in Table 2, and the molecular structure is
depicted in Fig. 1. The space-group is P-1(2) with a triclinic crystal system. The indol-2-one
ring system is substantially planar, the angle of C2–N2–O2 is 121.359(279)°, and the angle of
C2–N2–C9 is 123.272(262)°. In the crystal structure, typical intermolecular N—H…O
hydrogen bonds are responsible for the formation of dimmers as shown in Fig. 2, and the
hydrogen bonds parameters are included in Table 3. The π-π stacking between the planar
moities is responsible for the formation of a one-dimensional network, and a packing diagram
of (E)-3-(N-oxide- methylimino)indolin-2-one is depicted in Fig. 3.
Inhibitor properties and mechanism
Corrosion can be defined as the degradation of a material due to a reaction with its
environment. Degradation implies deterioration of physical properties of the material. This
can be a weakening of the material due to a loss of cross-sectional area, it can be the
shattering of a metal due to hydrogen embrittlement, or it can be the cracking of a polymer
due to sunlight exposure. The use of corrosion inhibitors has been considered as the most
effective method for the protection against such acid attack. Some inhibitors, such as
imidazoline, Mannich base, Schiff base and some other heterocyclic compounds, have been
employed in this process, but the concentration or the price is too high to be acceptable.
In the following work, the performance of the title compound as an inhibitor with the
concentration from 100 to 1000 mg/L in 1M and 2M HCl under the temperature from 30 ℃
to 65 ℃, and the results were summarized in Table 4. From the table, it was found that
almost all the IE increases along with the concentration of inhibitor, but there is difference in
the two concentrations and different temperatures, and it reaches to 83.2% with the
concentration of 1000 mg/L in 1M HCl solution, further increase of the inhibitor does not
increase the IE.
The inhibition mechanism of the corrosion inhibiting may be mainly contributed to the
adsorption. The process of adsorption is governed by the chemical structure of these inhibitors.
The presence of N, O, S atoms and conjugated bonds in the structures makes the formation of
p–d bonds resulting form the overlap of p electrons to the 3d vacant orbital of Fe atoms,
which conforms the adsorption of the compounds on the metal surface [23]. The inhibitive
performance of (E)-3-(N-oxide- methylimino)indolin-2-one can be explained on the presence
of polydentate nitrone and indolin which rises the possibility of transferring the unshared
electron of this molecule to iron [24]. The molecules may absorb on the ion surface by the
coordinate covalent bonds with the 3d vacant orbital of Fe atoms in the manner described in
Figure 1 to form the protective film.
The possible reaction centers are unshared electron pair
of heteroatoms and/or p-electrons of aromatic ring. The schematic illustration of different
modes of adsorption on metal is shown in Fig. 4.
Tafel polarisation measurements
The anodic and cathodic polarization results were shown in Fig. 5. Table 5 shows the
electrochemical corrosion kinetic parameters. As it was expected both anodic and cathodic
reactions of mild steel electrode corrosion were inhibited by the increase of the title
compound. It means that the addition of the (E)-3-(N-oxide- methylimino)indolin-2-one can
reduce anodic dissolution and also retards the hydrogen evolution reaction. With a
concentration of 1,000 mg/L, the additive exhibits maximum IE of 80.1%. The extract causes
changes in the anodic, cathodic Tafel slopes and the Ecorr values in the presence of different
concentrations. Ecorr, βa and βc values do not change appreciably with the addition of the
inhibitor, which indicates that the inhibitor is not only interfering with the anodic dissolution
or cathodic hydrogen evolution reactions independently but also acts as a mixed-type
(anodic/cathodic) of inhibitor. Increasing IE with increasing concentration of the AE shows
that the inhibition actions are due to its adsorption on the steel surface [24]. The IEs gotten
from potentiodynamic polarization were quite different from that from weight-loss
measurements, which is due to the fact that the weight- loss method gives average corrosion
rate, whereas electrochemical method gives instantaneous corrosion rates.
Scanning electron microscopy
To evaluate the conditions of the steel in contact with 2M HCl acid solutions, SEM
investigation was carried out as shown in Fig 7. In this figure, a shows the SEM image of the
polished steel sample, b shows SEM images of the surface of the steel specimens after
immersion in 2M HCl solution without inhibitor for 4 h, which shows the result of cracks
caused by acidic corrosion attack. The status in c shows the surface of the steel specimens
immersed for 4 h in 2M HCl solutions containing 1000 mg/L inhibitor, and the surface
appears smooth, which is much less damaged than that without any inhibitors. This was due to
adsorption of (E)-3-(N-oxide- methylimino)indolin-2-one on the steel surface, which accords
with the mechanism analysis above.
Bioactivity
Corrosion is an electrochemical process leading to the deterioration of materials that can be
caused or accelerated by microbiological activity, so called Microbiologically Influenced
Corrosion (MIC). It is estimated that 30-50% of the corrosion cases are a result of microbial
activity. MIC caused by growth of sulfate reducing bacteria (SRB), iron bacteria (IB) and
total general bacteria (TGB) in oil pipelines, is considered a major problem for water
treatment in the oil industry. MIC can result in different types of attack: pitting, crevices,
dealloying and erosion in pipelines [21]. Corrosion products produced by microorganisms are
production of hydrogen sulfide, molecular hydrogen, hydrogen ions and destabilization of
metal oxide films. In addition, microbial degradation of crude oil can lead to increased acidity
in the oil phase, and oil containing acids is a problem concerning corrosion of pipelines. The
reported results showed that the interaction of IB, SRB and TGB accelerated the corrosion
rate, and the corrosion in the mixture of IB, SRB and TGB was more serious than in a single
microbial system. If this is the case, different treatment system to inhibit corrosion should be
considered, among which bactericide agent has received the greatest acceptance. Currently,
oxidizer, aldehyde, quatemary ammonium salt and heterocycle compounds has been used as
bactericide agents, and Cl2 , ClO 2 , formaldehyde, pentane-1,5-dial, trichloroisocyanuric acid
(TCCA) [25], but the toxicity tests have been conducted on a limited selection. The antifungal
activity of (E)-3-(N-oxide- methylimino)indolin-2-one against oilfield microorganism was
tested under the concentration of 0.20g/L and 0.02g/L, and the results were summarized in
Table 6. From the table, it can be found that (E)-3-(N-oxide- methylimino)indolin-2-one is
antifungal active against SRB and IB, but inactive against TGB under both concentrations.
Conclusions
(E)-3-(N-oxide- methylimino)indolin-2-one was synthesized and the its inhibition and the
mechanism on the corrosion of high protective Q235A steel in HCl solution were investigated
by multi- method. It can inhibit the corrosion with moderate inhibition efficiency in different
conditions and the highest reaches to 83.2% with the concentration of 1000 mg/L in 1M HCl
solution. Besides, it displays potent activity against the oilfield water-borne bacteria,
especially for SRB and IB.
Acknowledgme nts
This work was financially supported by the grants from National Science Foundation of
China (21376189), Scientific and Technological Plan Projects of Shaanxi Province
(2014TG-09) and Scientific Research Program Funded by Shaanxi Provincial Education
Department (2013JK0647).
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-
O
N+
O
+
N
H
O
CH3NHOH
N
H
Scheme 1 Synthesis of (E)-3-(N-oxide-methylimino)indolin-2-one
O
Fig. 1 Molecular structure of (E)-3-(N-oxide-methylimino)indolin-2-one
Fig. 2 The inte rmolecular hydrogen bonds of (E)-3-(N-oxide-methylimino)indolin-2-one
Fig. 3 The packing diagram of (E)-3-(N-oxide-methylimino)indolin-2-one
Fig. 4 Absorption of (E)-3-(N-oxide-methylimino)indolin-2-one molecules on the ion
surface
Fig. 5 Typical polarization curves for corrosion of the steel in 2M HCl in the absence and
presence of different concentrations of (E)-3-(N-oxide-methylimino)indolin-2-one
（a）
（b）
（c）
Fig. 6. SEM micrographs of steel samples after 4 h immersion
(a) Blank; (b) Immersion in 2M HCl, (c) Immersion in 2M HCl + 1000 mg/L title compound
Table 1 Experimental Data of (E)-3-(N-oxide-methylimino)indolin-2-one
Crystal parameter
data
Crystal parameter
data
a (Ǻ)
6.951(6)
Index ranges
-4 ≤ h ≤ 5;
-13 ≤ k ≤ 12;
-11 ≤ l ≤ 12
b (Ǻ)
8.029(7)
Reflections collected
3112
c (Ǻ)
8.658(6)
Independent reflections
2190
α (º)
103.00(2)
Reflections theta (°)
2.26 to 28.27
β (º)
98.46(2)
Absorption correction
transmission
0.9440 to 0.9861
γ (º)
115.40(1)
Reflections with I≥2σ(I)
1427
Volume
408.67(514)
Number of parameters
109
Z
2
Goodness-of-fit on F2
1.006
Density (mg/m3 )
1.510
Final R indices [I﹥2s(I)]
R1 = 0.1884;
wR2 = 0.1323
0.112
R indices (all data)
R1 = 0.0674;
wR2 = 0.1027
F (000)
168
Refine different density
-0.224 to 0.176
Crystal size (mm3 )
0.20×0.22×0.30
Theta range for data
collection (°)
1.9 to 27.3
Absorption
coefficient
Table 2 The atomic coordinates (in Å2 ) of (E)-3-(N-oxide-methylimino)indolin-2-one
Atom
x/a
y/b
z/c
Atom
y/b
z/c
O1
0.5293(4) 0.9571(3) 0.7060(3)
O2
0.2534(4) 0.4094(3) 0.8098(3) H7A
0.46280
0.69720
1.03920
N1
0.3609(4) 0.7373(4) 0.4414(3) H7B
0.41060
0.83160
0.95380
0.62480
0.81270
0.94740
H1A
0.39390
0.81930
0.38800
C9
x/a
H7C
N2
0.3469(4) 0.5782(4) 0.7916(3)
C2
0.3293(5) 0.5984(4) 0.6444(4) H5A
C8
0.2151(5) 0.4427(4) 0.4873(4)
C7
0.2381(5) 0.5349(4) 0.3659(4) H3A
-0.06740
C1
0.4224(5) 0.7894(4) 0.6097(4)
0.0352(6) 0.2258(5) 0.1566(4)
C3
0.0995(5) 0.2409(5) 0.4423(4) H4A
H2A
0.08210
0.17900
0.52200
C6
0.4723(6) 0.7446(5) 0.9466(4)
C4
C5
0.1483(5) 0.4288(5) 0.1986(4)
0.16280
0.49000
0.11850
0.0100(6) 0.1333(5) 0.2747(5)
-0.02480
-0.00200
0.15070
0.24220
0.04570
Table 3 The intermolecular hydrogen bonds parameters of
(E)-3-(N-oxide-methylimino)indolin-2-one
D—H···A
D—H
H···A
D···A
D—H···A
N1(i)—H1A(i)···O1(ii) 0.8593(32) 2.033(3)
2.8845 (46)
170.748(212)
N1(ii)—H1A(ii)···O1(i) 0.8593(32) 2.033(3)
2.8845 (46)
170.748(212)
*Symmetry codes: (i) −x+1, y+1/2, −z+2; (ii) −x+1, y−1/2, −z+2.
Table 4 The corrosion inhibition efficiency of (E)-3-(N-oxide-methylimino)indolin-2-one
Concentration
HCl Concentration
Temperature
Inhibition Efficiency
(mg/L)
(M)
(℃)
(%)
100
1
30
16.4
100
1
45
25.5
100
1
60
18.9
100
2
30
12.0
100
2
45
13.8
100
2
60
15.6
200
1
30
32.2
200
1
45
20.8
200
1
60
22.1
200
2
30
16.51
200
2
45
17.9
200
2
60
18.9
500
1
30
15.3
500
1
45
79.3
500
1
60
65.9
500
2
30
48.1
500
2
45
35.7
500
2
60
57.8
1000
1
30
83.2
1000
1
45
67.9
1000
1
60
48.6
1000
2
30
68.8
1000
2
45
63.5
1000
2
60
33.3
Table 5 Potentiodynamic polarization parameters for the corrosion of the steel in the 2M
HCl solution containing (E)-3-(N-oxide-methylimino)indolin-2-one
Concentration
(mg/L)
−Ecorr
(mV)
Icorr
βa
βc
2
(μA/cm ) (mV/dec) (mV/dec)
--
0.4607
151.445
90.435
50
0.4647
141.906
100
0.4552
200
Corrosion rate
(mm/a)
IE
(%)
155.21
1.8022
--
107.112
166.59
1.3221
26.6
90.512
77.033
146.33
1.0519
41.6
0.4553
31.432
63.162
119.67
0.7986
55.7
500
0.4609
51.930
62.719
81.25
0.5574
69.1
1,000
0.4526
30.781
58.288
135.31
0.35880
80.1
Table 6 The antifungal activity of (E)-3-(N-oxide-methylimino)indolin-2-one against
oilfield wate r-borne bacte ria
Microbiotic Concentration /mL
Concentration
SIB
IB
TGB
—
110.0
110.0
110.0
0.20 g/L
0.0
0.0
70.0
0.02 g/L
0.0
1.3
110.0