Synthesis and fungicidal activity of 2-benzoylaminobenzimidazole complex compounds with copper

Article abstract of DOI:10.1134/S107042721302262

Special features of the formation of 2-benzoylaminobenzimidazole complexes with copper(II) chloride, sulfate, and acetate were studied. Optimal conditions of obtaining the complexes were found, and chemical compositions, some physicochemical properties, a

Full text of DOI:10.1134/S107042721302262

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2013, Vol. 86, No. 2, pp. 285−288. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © G.E. Chikisheva, Yu.E. Sapozhnikov, R.Kh. Mudarisova, L.I. Buslaeva, Z.B. Galieva, D. Davletov, 2013, published in Zhurnal
Prikladnoi Khimii, 2013, Vol. 86, No. 2, pp. 306−309.
BRIEF
COMMUNICATIONS
Synthesis and Fungicidal Activity
of 2-Benzoylaminobenzimidazole Complex Compounds
with Copper
G. E. Chikisheva, Yu. E. Sapozhnikov, R. Kh. Mudarisova,
L. I. Buslaeva, Z. B. Galieva, and R. D. Davletov
Scientific and Engineering Institute of Herbicides and Plants Growth Regulators,
Academy of Sciences of Bashkortostan Republic, Ufa, Russia
Institute of Organic Chemistry, Ufa Scientific Center, Russian Academy of Sciences, Russia
e-mail: g.e.chik@yandex.ru
Received November 14, 2012
Abstract—Special features of the formation of 2-benzoylaminobenzimidazole complexes with copper(II) chloride,
sulfate, and acetate were studied. Optimal conditions of obtaining the complexes were found, and chemical com-
positions, some physicochemical properties, and fungicidal activity of the synthesized compounds were studied.
DOI: 10.1134/S107042721302262
Benzimidazoles belong to a manifold type of chemical
compounds with a biological activity, which is not limited
to antihelminthic activity, but also covers pathogenic
fungi, viruses, and bacteria [1–4]. The methyl ether of
2-benzimidazolylcarbamine acids (BMC) is most known
among 2-aminobenzimidazole derivatives. Earlier [5–7]
various benzoylaminobenzimidazoles were synthesized
and tested for biological activity. The simplest of them,
2-benzoylaminobenzimidazole (2-BABI), is highly com-
petitive with BMC for the fungicidal activity. Benzimid-
azoles readily form complexes with transition metals.
Biological activity and structure of various derivatives of
N-(benzimidazolyl-2)carbamine acid with transition metals
were described in detail in the literature [8–10], however
similar data on the complexes of substituted 2-aminoben-
zimidazoles are practically absent.
in acetone in the presence of triethylamine at 55°С.
Preparation of acyl derivatives of 2-aminobenzimidazole
and also the structure of these compounds studied by
the 13С NMR method were described earlier [5–7].
Chemically-pure grade copper chloride, sulfate, and
acetate were used without additional purification. The
IR spectra of powders in vaseline oil were recorded on
an IR Prestige-21 Fourier-transform infrared Shimadzu
spectrophotometer in the range of 700–3600 cm–1,
and the UV spectra of water-alcohol solutions in the
range of 190-400 nm were taken on a Hitachi M 340
spectrophotometer.
Complex of 2-BABI with copper chloride. 1.185 g
(0.005 mol) of 2-BABI was loaded in a capsule, filled in
with a solution of 0.4263 g (0.025 mol) of CuCl2·2H2O in
3 ml of H2O, and 1 ml of acetone was added. The result-
ing suspension was heated up with stirring at 55°С within
10 min and dried under an infrared lamp. The obtained
compound was washed free from unreacted copper chlo-
ride by water, then by acetone, and dried above CaCl2.
The yield of the resulting complex was 87.0% with the
copper content of 10.04 wt %.
In the present work the formation of 2-BABI com-
plexes with copper(II) chloride, sulfate, and acetate in
water-alcohol and water-acetone media was considered,
and their fungicidal activity was determined.
EXPERIMENTAL
In the experiments we used 2-BABI obtained by
acylating of 2-aminobenzimidazole with benzoyl chloride
Complex of 2-BABI with copper sulfate. 0.6 g
(0.00253 mol) of 2-BABI was dissolved in 50 ml of ac-
285

286
CHIKISHEVA et al.
Table 1. Elemental analysis of 2-BABI complexes with copper(II) salts
Cu, wt %
Anion, wt %
Complex
Color
Found
10.04
Calculated
10.44
Found
Calculated
11.65
[2-BABI]2·CuCl2
Green
''
11.60
14.84
–
[2-BABI]2·CuSO4
9.89
9.81
10.03
9.69
15.15
18.0
[2-BABI]2·Cu(CH3COO)2
Dark green
Table 2. Fungicidal activity of 2-BABI complexes with copper(II) salts
Suppression of growth of colonies of funguses, % of control diameter of colonies
2-BABI
content,
wt %
Helminto-
Compound
Fuzarium Fuzarium Fuzarium
graminiarum culmorum oxysporum
Alternaria Botrytis Penicillium
alternata sinerea chrizogenum
sporium
sativum
[2-BABI]2·CuSO4
[2-BABI]·Cu(CH3COO)2
[2-BABI]·CuCl2
2-BABI
74.81
72.30
77.90
100
80.0
89.4
95.2
95.8
83.5
95.9
96.8
97.2
40.6
59.4
50.2
71.0
41.0
38.8
32.2
40.1
24.5
29.8
37.2
42.2
19.0
25.1
40.6
44.5
89.0
92.5
93.5
86.1
etone with 3 ml of water added. 0.316 g (0.00126 mol) of
СuSO4·5H2O was dissolved in 7 ml of water and added
to the 2-BABI solution. The reaction mixture was heated
up to 50°С and stirred within 2 h. Then the solvent was
distilled off on a rotor evaporator. The resulting precipi-
tate was washed with water and acetone and dried above
CaCl2. The yield of the complex was 85.0% with the
copper content of 9.89 wt %.
weighted sample in a nitric acid solution with added ethyl
alcohol. The resulting solution was neutralized by an
alkali up to рН 3.5 and titrated by a mercury nitrate solu-
tion in the presence of diphenylcarbazone as an indicator.
A content sulfate ion was determined gravimetrically by
the procedure described in the handbook [13].
Tests of chemical compounds for fungicidal activity
were carried out by the method of cultivation of funguses
on a nutrient medium containing fungicides. All com-
pounds were tested in the concentration of 0.003% after
dissolution in dimethyl formamide (3 mg of a complex in
0.5 ml of the solvent). Potato-glucosic agar was used as
a substrate. A compound under testing was entered into
a nutrient medium up to its solidification at 45–50°С,
and then the medium was sloped to Petri dishes, 15 cm3
in each. Mycelia of a fungus were sowed into each Petri
dish simultaneously in three points. In a check sample
funguses were sowed on the same nutrient medium,
but without a fungicide. Sowings were incubated in a
thermostat within 72 h at 25–26°С, and then an average
diameter of colonies was determined.
Complex of 2-BABI with copper acetate. 1.2 g
(0.0051 mol) of 2-BABI was dissolved in 100 ml of ac-
etone with 6 ml of H2O added. 0.5054 g (0.0025 mol) of
Cu(C2H3O2)2·H2O was dissolved in 250 ml of acetone on
heating.Asolution of copper(II) acetate was added to the
resulting solution of 2-BABI with stirring. The reaction
mixture was stirred within 2 h at 50°С. After cooling the
precipitate formed was filtered, washed out on a filter by
acetone, and dried above CaCl2. The yield of the complex
was 48.2% with the copper content of 9.81 wt %.
Copper contents in the 2-BABI complexes with
copper(II) chloride and sulfate were determined by
complexometric titration with Trilon B after preliminary
decomposition of the complexes [11]; a copper content
in the 2-BABI complex with copper(II) acetate was de-
termined by the gravimetric method of burning in a fast
oxygen flow [12].Acontent of chloride ions in a complex
was determined by mercurimetry after dissolution of a
Structures of the obtained complexes of 2-BABI with
copper(II) salts were studied by the IR spectroscopy
method. The absorption band of carbonyl group stretch-
ing vibrations at 1662 cm–1, which is characteristic for
the spectrum of 2-BABI, disappears or becomes low-
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SYNTHESIS AND FUNGICIDAL ACTIVITY
287
intensive in the IR spectra of the complexes under study.
The absorption band of bending vibrations of the 2-BABI
carbonyl group at 1520 cm–1 changes similarly, it is absent
from the spectra of the complexes. These changes point to
the involvement of carbonyl oxygen in the coordination
with copper. Intensive absorption bands of benzimidazole
rings at 1632 and 1564 cm–1, characteristic for 2-BABI,
are displaced by 10–15 cm-1 into the low-frequency
region and save a high intensity in the spectra of its cop-
per complexes. New bands appear in the same region in
positions depending on a copper salt anion participating
in the complex formation: 1587 (with copper chloride),
1576 (with copper sulfate), and 1585 cm–1 (with copper
acetate).Absorption bands of stretching vibrations of the
2-BABI amino group at 3375, 3354, and 3313 cm–1 hold
constant their positions and relative intensities upon the
complex formation.
ylaminobenzimidazole forms with copper(II) a complex
containing two 2-BABI molecules.
Using the data of the molar ratios method, we have
calculated the instability constants of 2-BABI com-
plexes with copper(II) acetate, sulfate, and chloride in a
water-alcohol medium: 2.3 × 10–8, 1.1 × 10–9, and 5.9 ×
10–8 l mol–1, respectively. Low values of constants of in-
stability constants of 2-BABI complexes with copper(II)
salts point to a high stability of the obtained complexes
in water-alcohol solutions.
The synthesized complexes were analyzed for the
contents of copper and chloride and sulfate ions. The
elemental analysis data for these complexes are presented
in Table 1.
Thus, as a result of our study we have shown that in
the water-alcohol and water-acetone media 2-BABI forms
bidentate complexes, in which two 2-BABI molecules fit
to one copper atom, and anions of salts in use are also
included into the structure of the complexes.
Changes in the IR spectra of 2-BABI complexes
with copper in the region of vibrations of the benzimid-
azole ring and carbonyl group point to the attachment
of a 2-BABI molecule to a copper atom by means of
the imine nitrogen atom and the carbonyl oxygen atom.
The character of changes in the IR spectra compared to
the ligand spectrum points to the similarity of imidazole
ring structures in the coordinated and free states. The
participation of two heteroatoms of the 2-benzoylamino-
benzimidazole molecule, the nitrogen aromatic atom, and
the oxygen aliphatic atom in the formation of a coordina-
tion bond provides a high stability to 2-BABI complex
compounds with copper(II).
2-Benzoylaminobenzimidazole and its complexes in
the concentration of 0.003% were tested for fungicidal
activity on pure growths of phytopathogenic funguses:
representatives of Fuzarium, Alternaria, Helmintospo-
rium, Botryt, and Penicillium genera (Table 2). It is seen
from Table 2 that the fungicidal activity of the obtained
compounds depends on the nature of copper salt anions
participating in the complex formation, and thus the ac-
tivity of the 2-BABI complex with copper(II) chloride
is much higher than that of the other complexes. The
obtained complexes have exhibited the highest fungicidal
activity with respect to fusariose presented by Fusarium
culmorum, Fusarium graminearum, and also to Penicil-
lium chrizogenum, in other cases they have shown a weak
fungicidal activity.
The composition of 2-BABI complexes with
copper(II) acetate, sulfate, or chloride was determined
by spectrophotometry in water-alcohol solutions. The
complex formation was detected by variations of the
2-BABI UV spectrum in the presence of copper salts by
the method of molar ratios at a constant 2-BABI con-
centration (3.2 × 10–5 M) and increasing concentration
of copper(II) salts (from 0 up to 3.2 × 10–5 M). When
2-BABI solutions were mixed with copper(II) salts light
absorbance at the wave length of 298 nm (2-BABI absorp-
tion maximum) decreased and the absorption maximum
was slightly displaced in the long-wavelength region. On
the basis on the data obtained we constructed plots of opti-
cal density А298 of solutions vs. the ratio of a copper(II)
salt concentration to a 2-BABI concentration at a constant
2-BABI concentration [14]. The position of a breakpoint
in the plots gives the ratio of stoichiometric coefficients
in the 2-BABI–Cu(II) complex formation reaction equal
to 2 : 1. It follows from the results obtained that 2-benzo-
A correlation between the fungicidal activity (except
for Helmintosporium sativum) and instability constants
of the complexes is observed. The higher is the instabil-
ity constant of a complex, the greater is its fungicidal
activity. It is necessary to note that the complexes come
nearer to 2-BABI by fungicidal activity, in spite of the
fact that they contain approximately 25% of 2-BABI less
it their composition.
CONCLUSIONS
(1) Optimal conditions for the synthesis of 2-benzoyl-
aminobenzimidazole complexes with copper(II) chloride,
sulfate, and acetate were fitted. The 2-benzoylaminoben-
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288
CHIKISHEVA et al.
zimidazole : copper salt ratio of 2 : 1 was determined
by the IR and UV spectroscopy methods and also by
elemental analysis. Instability constants of the complexes
were calculated. It was shown that the high stability of the
complex compounds is caused by the participation of the
imine nitrogen atom and the aliphatic oxygen atom of the
2-benzoylaminobenzimidazole molecule in the formation
of a coordination bond with copper.
6. Pilyugin, V.S., Sapozhnikov, Yu.E., Davydov, A.M., et al.,
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