Synthesis and potency study of some Dibutyltin(IV) dinitrobenzoate compounds as corrosion inhibitor for mild steel HRP in DMSO-HC1 solution

Article abstract of DOI:10.14233/ajchem.2015.18590

Following our succes in the synthesis of some derivatives of organotin(lV) carboxylates, in this work we reported the corrosion inhibitor study of three dibutyltin(IV) compounds using ligands of 2-, 3- And 4-nitrobenzoic acid. All the three synthesized compounds were characterized by spectroscopy techniques and also based on the microanalytical and physical data. The corrosion inhibition was evaluated with potentiodynamic polarization technique using ER644 Integrated Potentiostat eDAQ type on mild steel hot rolled plate (HRP) in DiMSO-HCl solution. The results indicated that the these compounds showed interesting inhibition activity with percentage of inhibition efficiency (% IE) of 59.3, 60.5 and 61.2 % for dibutyltin(IV) 2-nitrobenzoate, 3-nitrobenzoate and 4-nitrobenzoate, respectively. These three dibutyltin(IV) compounds have been shown promising to be potentially used as anticorrosion inhibitors.

Full text of DOI:10.14233/ajchem.2015.18590

Asian Journal of Chemistry; Vol. 27, No. 4 (2015), 1509-1512
A
SIAN
J
OURNAL OF HEMISTRY
C
http://dx.doi.org/10.14233/ajchem.2015.18590
Synthesis and Potency Study of Some Dibutyltin(IV) Dinitrobenzoate
Compounds as Corrosion Inhibitor for Mild Steel HRP in DMSO-HCl Solution
*
SUTOPO HADI , HAPIN AFRIYANI, WYNDA D. ANGGRAINI, HARDOKO I. QUDUS and TATI SUHARTATI
Department of Chemistry, University of Lampung, Bandar Lampung 35145, Indonesia
*Corresponding author: Fax: +62 721 704625; Tel: +62 721 701609, Ext 967; E-mail: sutopo.hadi@fmipa.unila.ac.id
Received: 13 August 2014;
Accepted: 12 September 2014;
Published online: 4 February 2015;
AJC-16825
Following our succes in the synthesis of some derivatives of organotin(IV) carboxylates, in this work we reported the corrosion inhibitor
study of three dibutyltin(IV) compounds using ligands of 2-, 3- and 4-nitrobenzoic acid. All the three synthesized compounds were
characterized by spectroscopy techniques and also based on the microanalytical and physical data. The corrosion inhibition was evaluated
with potentiodynamic polarization technique using ER644 Integrated Potentiostat eDAQ type on mild steel hot rolled plate (HRP) in
DMSO-HCl solution. The results indicated that the these compounds showed interesting inhibition activity with percentage of inhibition
efficiency (% IE) of 59.3, 60.5 and 61.2 % for dibutyltin(IV) 2-nitrobenzoate, 3-nitrobenzoate and 4-nitrobenzoate, respectively. These
three dibutyltin(IV) compounds have been shown promising to be potentially used as anticorrosion inhibitors.
Keywords: Inhibitor, Corrosion, Dibutyltin(IV) dinitrobenzoate, Hot rolled plate mild steel.
HPLC grade, petroleum ether, acetone and methanol were JT
Baker products and all of them were used without further
purification.
INTRODUCTION
The interest in the chemistry of organotin compound
continues to grow and are mostly due to their significant effects
on their biological activity1,2. Their biological activities are
fundamentally determined by the number and the nature of
organic groups bound to the central Sn atom3. The nature of
the anionic groups seems acting only as a secondary factor3,4.
The latest researches on the complexation of carboxylate acid
derivatives with some organotin(IV) compounds have pro-
duced some new organotin(IV) carboxylate derivatives, where
in most cases have shown some interesting biological activities
such as antimicrobial5-8, antitumor and anticancer3,7-11, anti-
fungal activity4,6,12,13, antiplasmodial14 and the latest develop-
ment of these compounds has led to the new finding as
anticorrosion inhibitor15-17, therefore the investigation of
organotin(IV) as a prospective anticorrosion is very challen-
ging, has been and will still be attracting more attention.
In the present work, we reported the application and anti-
corrosion inhibition study of some dibutyltin(IV) dinitrobenzoates
toward hot rolled plate mild steel in DMSO-HCl solution.
Elemental analyses (CHNS) were performed on Fision
EA 1108 series elemental analyser. IR spectra in the range of
4000-300 cm-1 were recorded on a Bruker VERTEX 70 FT-IR
spectrophotometer with KBr discs. The UV spectra were recorded
in the UV region and were measured using a UV- Shimadzu
UV-245 Spectrophotometer. Measurements were performed
in 1 mL quartz-cells. Solutions were prepared using methanol
as the solvent with concentration of 1 × 10-4 M. 1H and 13C NMR
spectra were recorded on a Bruker AV 600 MHz NMR (600
MHz for 1H and 150 MHz for 13C). All experiments were run
in DMSO-D6 at 298 K. The number of runs used for 1H experi-
ments were 32 with reference at DMSO signal at 2.5 ppm,
while the 13C were 1000-4000 scans with the reference DMSO
signal at 39.5 ppm.
Synthesis of dibutyltin(IV) dinitrobenzoates: The
dibutyltin(IV) dinitrobenzoates used in this work were pre-
pared based on the refinement procedures which have been
succesfully used and has been reported previously10-12. The
following procedure was used in the preparation of dibutyl-
tin(IV) dinitrobenzoate:
EXPERIMENTAL
All reagents used were of AR grade. Dibutyltin(IV)
dichlorides ([(n-C4H9)2SnCl2]), HCl, dimethyl sulfoxie, sodium
hydroxide, 2-nitrobenzoic acid, 3-nitrobenzoic acid and 4-
nitrobenzoic acid were obtained from Sigma Aldrich, water
To 3.04 g (0.01 mol) [(n-C4H9)2SnCl2] (1) in 50 mL methanol
was added 0.8 g (0.02 mol) NaOH. The reaction mixtures were
stirred for about 45 min. Compound [(n-C4H9)2SnO] (2)
was precipitated out as a white solid, filtered off, washed

1510 Hadi et al.
Asian J. Chem.
succesivelly with double distilled water then with acetone and
dried in vacuo until it is ready for analysis and further reaction.
The average yield was 2.35 g ( 95 %).
The qualitative analysis of the steel surface was performed
by immersing the steel with and without dibutyltin(IV) dinitro-
benzoate inhibitor in the corrosive medium and followed by
taking the image of the steel surface using microscope after
the immersion process.
To 0.374 g (1.5 mmol) compound 2 in 50 mL of methanol
was added with 2 mole equivalents of nitrobenzoic acid (0.25
g) and was refluxed for 4 h at 60-70 °C. After removal of the
solvent by rotary evaporator, the solid was washed with petro-
leum ether (60-80 °C), on cooling a white solid of the product
compounds of [(n-C4H9)2Sn(OOCC6H4NO2)2] was obtained
and dried in vacuo until they are ready for analysis and further
use for anticorrosion inhibition test.
Corrosion inhibitor measurement: Mild steel hot rolled
plate types were cut in 2 × 1 cm2 and were successively polished
with abrasive paper starting from grid 240, 400, 600 and 800.
After the surface of the mild steel were homogenous, the
surface were thoroughly washed with distilled water (aquadest),
dilute HCl and finally with acetone. The surface area of each
mild steel was then measured, weight out and stored in a vacuum
desiccator until they were used.
The potentiostat used was ER644 Integrated Potentiostat
eDAQ type. It has three electrode cells which is assembly
consisted of a working electrode of mild steel (2 cm2 exposed
are), a saturated AgCl as a reference electrode and a platinum
counter electrode.After being assembled, they were immersed
in corrosive medium as the electrolyte and connected to poten-
tiostat. The first step was the measurement of rate inhibition
without inhibitor, all three electrodes were immersed for 10
min in the electrolyte. The potential was set up with scanning
rate of 0.5 mV/s. The current change occurred were measured
and recorded, the data obtained were then processes to
deterimine the potentiodynamic graph (η against ln |j|) in which
the current corrosion density (Icorr0) and corrosion potential
(Icorri) were obtained using Tafel extrapolation method18. The
similar way was used in the masurement of inhibition rate
with inhibitor of dibutyltin(IV) nitrobenzoates. The concen-
tration of inhibitor used were 0, 10, 20, 40, 60, 80 and 100
mg/L. The data in each measurement were recorded and then
the percentage of inhibition efficienty (the corrosion rate) were
calculated based on eqn. 1.
RESULTS AND DISCUSSION
Synthesis of dibutyltin(IV) dinitrobenzoates: The com-
pounds of dibutyltin(IV) dinitrobenzoate, [(n-C4H9)2Sn(OO-
CC6H4NO2)2] (3, 4, 5), were successfully performed from their
chlorides [(n-C4H9)2SnCl2] (1), where all of the reactions in
all cases were done via [(n-C4H9)2SnO] (2) similar to those
previously reported10-12. Scheme-I showed the reaction step
that occurred in the synthesis of dibutyltin(IV) dinitro-benzate
(Fig. 1). Table-1 summarizes the result of microanalytical data
of all compounds synthesized and in general the data obtained
are good and all values obtained are in aggreement to those of
calculated values. The λmax obtained from the UV-visible spectro-
scopy analyses of all compounds synthesized is summarized
in Table-2. It is clear that there was a shifting change in the λmax
for each compound in any steps of the reaction and the data
agreed to those reported in the literatature10-12,20,21
.
TABLE-2
λ
max OF THE UV-VISIBLE SPECTRA OF
THE DIBUTYLTIN(IV) COMPOUNDS
Compound
[(n-C4H9)2SnCl] (1)
λ
max (nm) n-π
210.7
202.9
[(n-C4H9)2SnO] (2)
303.2
307.3
301.2
[(n-C4H9)2Sn(o-C6H4(NO2)COO)2] (3)
[(n-C4H9)2Sn(m-C6H4(NO2)COO)2] (4)
[(n-C4H9)2Sn(p-C6H4(NO2)COO)2] (5)
The 1H and 13C chemical shifts of the compounds prepared
are shown Table-3.A number of signals in the spectra recorded
have been characterized carefully. The chemical shift (δ) of
butyl protons attached to the tin metal appeared in the range
of 0.92 ppm for Hδ up to 1.37-1.62 ppm for Hα and Hβ and
the carbons of butyl ligands are observed at position compa-
Icorr − ICorr
rable with other similar compounds reported previously11,19
.
0
i
× 100 %
% Protection (% IE) =
(1)
The chemical shift of the carbon from carboxyl group of all
compounds as expected appeared in the region of 176-175 ppm
I
corr0
where % IE: the percentage of inhibition efficiency; Icorr
:
0
and similar to those reported previously and also by other11,19
.
current before the addition of inhibitor; Icorr : current after the
i
The carbon atoms in the nitrobenzoate ligands appeared in δ
addition of inhibitor.
Nitrobenzoic
acid
2
NaOH in MeOH
stirred 60 min
[(
n
C4H9)2SnCl2]
[(
n
C4H9)2SnO]
[(
n
C4H9)2Sn[OOCC6H4(NO2)]2]
stirred in MeOH
for 4 h
1
2
3, 4, 5
Scheme-I: Scheme of preparative route of the dibutyltin(IV) dinitrobenzoate
TABLE-1
MICROANALYTICAL DATA OF THE DIBUTYLTIN(IV) COMPOUNDS SYNTHESIZED
Elemental analysis found (calculated)
Compound
C
H
N
46.30 (46.73)
46.23 (46.73)
46.41 (46.73)
4.52 (4.60)
4.62 (4.60)
4.57 (4.60)
4.91 (4.96)
4.98 (4.96)
4.93 (4.96)
[(n-C4H9)2Sn(o-C6H4(NO2)COO)2] (3)
[(n-C4H9)2Sn(m-C6H4(NO2)COO)2] (4)
[(n-C4H9)2Sn(p-C6H4(NO2)COO)2] (5)

Vol. 27, No. 4 (2015)
Synthesis and Potency Study of Some Dibutyltin(IV) Dinitrobenzoate Compounds as Corrosion Inhibitor 1511
TABLE-3
1H AND 13C CHEMICAL SHIFTS OF THE ORGANOTIN(IV) COMPOUNDS SYNTHESIZED
Compounds
H in butyl (ppm)
H in benzoate (ppm)
C in butyl and benzoate (ppm)
Cα: 21.3; Cβ: 26.6; Cγ: 25.9; Cδ: 14.2;
C1: 139.3; C2: 163.3; C3: 130.1; C4:
128.6; C5: 127.1; C6: 129.7; C7: 175.0
Cα: 21.3; Cβ: 26.7; Cγ: 25.9; Cδ: 14.3;
C1: 139.3; C2: 131.2; C3: 164.2; C4:
131.2; C5: 129.5; C6: 129.9 C7: 175.2
Hα & Hβ:1.39-1.61 (m);
Hγ: 1.29 (m); Hδ: 0.92 (t)
[(n-C4H9)2Sn(o-C6H4(NO2)COO)2] (3)
[(n-C4H9)2Sn(m-C6H4(NO2)COO)2] (4)
[(n-C4H9)2Sn(p-C6H4(NO2)COO)2] (5)
7.34-7.86 (m)
Hα & Hβ:1.4-1.6 (m);
Hγ: 1.29 (m); Hδ: 0.93 (t)
7.35-7.89 (m)
7.36-7.87 (m)
80
Cα: 21.3; Cβ: 26.7; Cγ: 25.9; Cδ: 14.2;
C1: 139.5; C2: 130.3; C3: 129.1; C4:
164.6; C5: 130.2; C6: 129.9; C7: 175.1
Hα & Hβ:1.41-1.6 (m);
Hγ: 1.29 (m); Hδ: 0.93 (t)
range of 140-130 ppm, thus very close to the reported values
for our previous compounds11.
3-Nitrobenzoic acid
Compound 1
Compound 2
Compound 3
60
40
Table-4 listed the key FT-IR data and the assignments of
all functional groups surround tin in every compound were
very similar to our previous works10-12. The most important
characteristic band of the starting material, the compound 1,
is the presence of strong stretching band from Sn-Cl bond
which appeared at wave number between 390-310 cm-1. In
the compound 1, the Sn-Cl bond appeared at frequency of
334.2 cm-1. The other characteristic bands of this compound
appear as stretching band from butyl ligands at 1069 cm-1 and
bending vibration of C-H aliphatic stretch of the butyl at
frequency of 2956-2865 cm-1. When compound 1 is converted
to compound 2, the main stretching band of Sn-Cl disappeared
and a new strong band at frequency of 417.4 cm-1 appeared as
one of the main stretching band. This band is characteristic
for Sn-O bond in compound [(n-C4H9)2SnO] (2). The stretching
band due to the butyls and their bending vibrations are still
appearing as expected although the frequencies have little bit
shifted. The formation of dibutyltin(IV) dinitrobenzoate com-
pounds, [(n-C4H9)2Sn(OOCC6H4NO2)2], (3, 4, 5) is confirmed
by the strong asymmetric stretching bands of the carboxylates
which occurred at ca. 1400 cm-1 and the symmetric stretch at
about 1600 cm-1 as well as the present of Sn-O stretching of
the acid at 435 cm-1 and the appearance of these bands is
20
0
0
20
40
60
80
100 120
-20
-40
-60
Inhibitor concentration (mg/L)
Fig. 1. Comparison curves of %IE vs inhibitor concentration
occured to them, as a result all ligands increased the corrosion
activity to the mild steel.
All dibutyltin(IV) dinitrobenzoate compounds synthesized
exhibited much higher corrosion inhibition activity compared
to those of the starting material and intermediate product, as
shown in Table-5. In this respect, our results are consistent
with a well-known fact that many biologically active com-
pounds become more active upon complexation than in their
uncomplexed forms22.
confirming the success of the substitution reaction10-12
.
TABLE-5
Anticorrosion inhibition activity test: The increase of
inhibition efficiency with increase in inhibitor concentration
was observed for all inhibitors (as an example is given in
m-nitrobenzoic acid series as shown in Fig. 1), a similar
observation was also observed by Rastogi et al.15,17. Based on
Fig. 1, it was also noted that the ligands used indeed increased
the corrosion activity as shown by their % IE values in which
all the ligands used in this work gave negative values. This
can be understood that the hydrogen ion of the acid in medium
used increasing the number of hygrogen ion due to ionization
PERCENTAGE INHIBITION EFFICIENTY (% IE)
Compounds
% IE
-41.9
-43.1
-42.2
21.9
22.3
59.3
60.5
61.2
2-Nitrobenzoic acid
3-Nitrobenzoic acid
4-Nitrobenzoic acid
[(n-C4H9)2SnCl2] (1)
[(n-C4H9)2SnO] (2)
[(n-C4H9)2Sn(o-C6H4(NO2)COO)2] (3)
[(n-C4H9)2Sn(m-C6H4(NO2)COO)2] (4)
[(n-C4H9)2Sn(m-C6H4(NO2)COO)2] (5)
TABLE-4
KEY IR BANDS (cm–1) OF THE DIBUTYLTIN(IV) COMPOUNDS
Compound
Bands
1
2
-
3
-
4
-
5
-
Sn-Cl
Sn-O
334.2
-
390-310
800-400
417.4
434.6
435.4
435.4
Sn-Bu
673.4
674.5
675.9
677.1
677.8
740-660
Sn-O-C
butyl
CO2 asym
CO2 sym
C-H aliphatic
-
-
1029.2
1073.3
1419.2
1558.2
2953-2860
1028.8
1074.9
1418.4
1560.1
2954-2863
1028.8
1074.1
1418.3
1559.6
2954-2861
1050-900
1100-1060
1600-1400
1700-1550
2960-2850
1069.2
1070.9
-
-
-
-
2953-2858
2953-2859

1512 Hadi et al.
Asian J. Chem.
According to Crowe23 the actual biological activity of
ACKNOWLEDGEMENTS
diorganotin compounds of the type RR'SnXY (R and R' = alkyl
or aryl; X andY = anions) is determined solely by the RR'Sn2+
moiety, however the presence of carboxylate or other anions
attached to tin metal was proven to be very important in the
increased activity of the organotin compounds as it has been
observed by many researchers4-15,17. Futhermore, it is believed
that the organotin(IV) corrosion inhibitors offer an excellent
method of protecting various material objects against the
aggressive effects of hostile environment, without limitations
in regard to shape or size of the object to be protected16. It has
been shown by qualitative analysis by immersing the mild steel
into the solution containing inhibitor dibutyltin(IV) compared
to immersing the mild steel into corrosive medium withoug
inhibitor (Fig. 2). The careful observation of the steel surface
with microscope was clearly indicated that the corrosion in
the surface of the mild steel which was immersed with corrosive
medium without inhibitor did occur as shown by the formation
of holes on the surface which is known as wells corrosion24
(Fig. 2a). The addition of dibutyltin(IV) dinitrobenzoate into
the corrosive medium used significantly inhibit the corrosion
process as shown by the less formation of wells corrosion (Fig.
2b). Therefore, corrosion protection is offered by partial or
complete inhibition of the electrochemical reactions16.
The authors are grateful to Directorate of Research and
Community Services, Directorate General of Higher Education,
The Ministry of Education and Cultural of Republic of
Indonesia that provide fund for this project to be undertaken
through Hibah Kompetensi (Competency Research Grant)
Scheme 2014 with contract number of 301/UN26/8/PL/2014.
Thanks also go to Prof. Bohari M. Yamin, Universiti Keban-
gsaan Malaysia for helping in doing microanalysis and Dr. Huy
Hoang of Institute of Molecular Biosciences (IMB) University
of Queensland, Brisbane, Australia for NMR experimentation.
REFERENCES
1. E.R.T. Tiekink, Appl. Organomet. Chem., 5, 1 (1991).
2. K. Shahid, S. Ali, S. Shahzadi and Z. Akhtar, Turk. J. Chem., 27, 209
(2003).
3. L. Pellerito and L. Nagy, Coord. Chem. Rev., 224, 111 (2002).
4. J.J. Bonire, G.A. Ayoko, P.F. Olurinola, J.O. Ehinmidu, N.S.N. Jalil
and A.A. Omachi, Met. Based Drugs, 5, 233 (1998).
5. M. Gielen, J. Braz. Chem. Soc., 14, 870 (2003).
6. A. Szorcsik, 1, L. Nagy, K. Gajda-Schrantz, L. Pellerito, E. Nagy and
F.T. Edelmann, J. Radioanal. Nucl. Chem., 252, 523 (2002).
7. B. Gleeson, J. Claffey, D. Ertler, M. Hogan, H. Müller-Bunz, F. Paradisi,
D. Wallis and M. Tacke, Polyhedron, 27, 3619 (2008).
8. W. Rehman,A. Badshah, S. Khan and L.T.A. Tuyet, Eur. J. Med. Chem.,
44, 3981 (2009).
9. Y. Li,Y. Li,Y. Niu, L. Jie, X. Shang, J. Guo and Q. Li, J. Inorg. Biochem.,
102, 1731 (2008).
10. S. Hadi and M. Rilyanti, Orient. J. Chem., 26, 775 (2010).
11. S. Hadi, M. Rilyanti and Suharso, Indo. J. Chem., 12, 172 (2012).
12. S. Hadi, B. Irawan and J. Efri, Appl. Sci. Res., 4, 1521 (2008).
13. S. Hadi, M. Rilyanti and Nurhasanah, Modern Appl. Sci., 3, 12 (2009).
14. C. Hansch and R.P. Verma, Eur. J. Med. Chem., 44, 260 (2009).
15. R.B. Rastogi, M.M. Singh, K. Singh and M. Yadav, Port. Electrochim.
Acta., 23, 315 (2005).
16. R. Singh, P. Chaudhary and N.K. Kaushik, Rev. Inorg. Chem., 30, 275
(2010).
17. R.B. Rastogi, M.M. Singh, K. Singh and M. Yadav, Afr. J. Pure Appl.
Chem., 5, 19 (2011).
18. U.R. Evans, Oxidation and Corrosion of Metals, Arnold, London, edn. 3
(1968).
a
b
Fig. 2. Surface of mild steel (a) corrosive medium without inhibitor and
(b) corrosive medium with the addition of dibutyltin(IV) di-3-
nitrobenzoate
19. M. Nath, R. Yadav, M. Gielen, H. Dalil, D. de Vos and G. Eng, Appl.
Organomet. Chem., 11, 727 (1997).
20. Sudjadi, The Structure Determination of Organic Compounds, Ghalia
Publishers (1985) (In Indonesian).
Conclusion
The dibutyltin(IV) dinitrobenzoate were continued to be
successfully prepared and it was quite clear that they have
shown some promising results to be used as anticorrosion
inhibitor. Although they are not as strong as other related
derivatives of organotin(IV). However, they are still good to
be used as anticorrosion inhibitors. Further studies are being
carried out to find the best inhibitor and the better way to apply
these compounds and other derivatives for the new generation
of anticorrosion which will be useful for many industries.
21. Z.H. Chohan and A. Rauf, Synth. React. Inorg. Met.-Org. Chem., 26,
591 (1996).
22. H. Gershon, J. Med. Chem., 17, 824 (1974).
23. A.J. Crowe, in ed.: M. Gielne, TheAntitumourActivity of Tin Compounds,
Metal-Based Drugs, Freund Publishing House, vol. 1, p. 103 (1989).
24. M.G. Fontana, Corrosion Engineering, McGraw Hill Book Company,
Singapore, edn. 3 (1986).