Synthesis, structures, and antimicrobial studies of cobalt(III) complexes with tridentate schiff bases

Article abstract of DOI:10.1080/15533174.2011.609238

Two new cobalt(III) complexes, [Co₂(L¹) ₂(AEN)(N₃)] (1) and [Co(L²)(PEA)(N ₃)] (2) (L¹ = 2-[1-(2-hydroxyethylimino) ethyl]phenolate, L² = 2-[1-(2-phenylaminoethylimino

Full text of DOI:10.1080/15533174.2011.609238

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Synthesis, Structures, and Antimicrobial Studies of
Cobalt(III) Complexes with Tridentate Schiff Bases
a
a
a
a
a
Wen-Yan Fang , Mai Xu , Chuan-Gao Zhu , Yi-Jun Wei & Feng-Wu Wang
a
Department of Chemistry and Chemical Engineering , Huainan Normal University ,
Huainan , P. R. China
Published online: 31 Jan 2012.
To cite this article: Wen-Yan Fang , Mai Xu , Chuan-Gao Zhu , Yi-Jun Wei & Feng-Wu Wang (2012) Synthesis, Structures, and
Antimicrobial Studies of Cobalt(III) Complexes with Tridentate Schiff Bases, Synthesis and Reactivity in Inorganic, Metal-
Organic, and Nano-Metal Chemistry, 42:1, 109-114, DOI: 10.1080/15533174.2011.609238
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 42:109–114, 2012
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.609238
Synthesis, Structures, and Antimicrobial Studies
of Cobalt(III) Complexes with Tridentate Schiff Bases
Wen-Yan Fang, Mai Xu, Chuan-Gao Zhu, Yi-Jun Wei, and Feng-Wu Wang
Department of Chemistry and Chemical Engineering, Huainan Normal University, Huainan, P. R. China
1
2
(
2) (L = 2-[1-(2-hydroxyethylimino)ethyl]phenolate, L =
Two new cobalt(III) complexes, [Co
2
(L1)
)] (2) (L = 2-[1-(2-hydroxyethylimino)
2
(AEN)(N
3
)] (1) 2-[1-(2-phenylaminoethylimino)ethyl]phenolate, AEN = 2-
2
1
and [Co(L )(PEA)(N
3
aminoethanolate, PEA = N-phenylethane-1,2-diamine).
2
ethyl]phenolate,
L
=
2-[1-(2-phenylaminoethylimino)ethyl]
phenolate, AEN = 2-aminoethanolate, PEA = N-phenylethane-
1
,2-diamine), have been prepared and characterized by elemental
EXPERIMENTAL
analysis and infrared spectroscopy. The structures of the complexes
have been determined by X-ray crystallography. The coordination
geometry around cobalt atoms in both complexes is distorted octa-
hedral with one tridentate Schiff base ligand, one bidentate ligand,
and one monodentate azide ligand. The antimicrobial activity of
the complexes was studied.
Materials and Methods
All the starting materials and organic solvents for synthesis
were of analytical grade, purchased commercially, and purified
by standard methods prior to use. Infrared spectra were recorded
on a Nicolet 55XC Fourier transform spectrophotometer using
−1
Keywords antimicrobial, cobalt complex, crystal structure, Schiff KBr pellets (4000–400 cm ). Elemental analysis was carried
base, synthesis
out on a Perkin-Elmer model 240 analyzer.
Synthesis of H2L1
INTRODUCTION
A solution of 2-acetylphenol (0.136 g, 1.0 mmol) in MeOH
Schiff bases are a kind of versatile ligands, which are (20 mL) was added to a solution of 2-aminoethanol (0.061 g,
usually synthesized by the condensation of primary amines 1.0 mmol) in MeOH (10 mL) under stirring. The mixture was
[
1–4]
with carbonyl-containing compounds.
The compounds are stirred at room temperature for 30 min, and then the solvent was
very important in medicinal and pharmaceutical fields. Many evaporated by distillation. The gummy product was recrystal-
1
of them show antibacterial, antifungal, and antitumor activ- lized from ethanol to give yellow microcrystals of H2L . Yield:
ity.[
5–8]
−1
A number of studies indicated that the coordina- 73%. Characteristic IR (cm , KBr pellets): 3432 (m), 1623 (s).
tion of the Schiff bases to the metal atoms can increase Anal. Calcd. for C10H13NO2: C, 67.0; H, 7.3; N, 7.8. Found: C,
[
9, 10]
the biological properties.
Cobalt complexes derived from 67.2; H, 7.4; N, 7.7.
symmetrical and nonsymmetrical Schiff bases have received
considerable attention in the past few decades for their in-
Synthesis of HL2
[
11–13]
A solution of 2-acetylphenol (0.136 g, 1.0 mmol) in MeOH
teresting biological properties.
Study on the structures
(20 mL) was added to a solution of N-phenylethane-1,2-diamine
and antimicrobial activities of new cobalt complexes with
Schiff bases may help us to search for novel antimicro-
bial agents. We report in this article the synthesis, crystal
structures, and antimicrobial activity of two new cobalt(III)
(0.136 g, 1.0 mmol) in MeOH (10 mL) under stirring. The
mixture was stirred at room temperature for 30 min, and then
the solvent was evaporated by distillation. The gummy product
was recrystallized from ethanol to give yellow microcrystals of
1
2
complexes, [Co2(L )2(AEN)(N3)] (1) and [Co(L )(PEA)(N3)]
2
−1
HL . Yield: 81%. Characteristic IR (cm , KBr pellets): 3432
m), 1621 (s). Anal. Calcd. for C16H18N2O: C, 75.6; H, 7.1; N,
(
11.0. Found: C, 75.3; H, 7.2; N, 11.2.
Received 15 July 2011; accepted 27 July 2011.
This project was supported by the Natural Scientific Research Foun-
1
dation of the Higher Education Institutions of Anhui Province, China Synthesis of [Co2(L )2(AEN)(N3)] (1)
(
Grant No. KJ2009A008). The authors also thank the support from
Professor Yang-Zhong Liu (University of Science and Technology of
China).
Address correspondence to Wen-Yan Fang, Department of Chem-
istry and Chemical Engineering, Huainan Normal University, Huainan
32001, P. R. China. E-mail: wyfang6312@163.com
To a stirring solution of CoCl2·6H2O (23.8 mg, 0.1 mmol)
in MeOH (10 mL) was added an equimolar quantity of H2L1
(
17.9 mg, 0.1 mmol), 2-aminoethanol (6.1 mg, 0.1 mmol), and
sodium azide (6.5 mg, 0.1 mmol) in MeOH (10 mL), and a
few drops of triethylamine. The mixture was stirred at room
2
109

110
W.-Y. FANG ET AL.
temperature for 1 h to give a deep brown solution, which was
left undisturbed at room temperature to slow evaporation of
the solvent. Brown crystals of the complex suitable for X-ray
diffraction were obtained after a few days. The crystals were
isolated by filtration, and were washed with cold methanol and
TABLE 1
Crystal data for (1) and (2)
Compound
(1)
(2)
Chemical formula
Fw
T (K)
C22H28Co2N6O5
574.4
C24H29ClCoN7O
525.9
1
−1
dried under vacuum. Yield: 53% based on H2L . IR (cm , KBr
pellets): 3221 (sh, m), 2034 (vs), 1614 (s), 1596 (s), 1536 (m),
298(2)
298(2)
block/brown
1
1
5
4
438 (s), 1332 (s), 1229 (m), 1164 (w), 1136 (w), 1048 (m),
016 (w), 930 (w), 873 (w), 755 (m), 634 (m), 598 (w), 531 (w),
05 (w), 458 (w). Anal. Calcd. for C22H28Co2N6O5: C, 46.0; H,
.9; N, 14.6. Found: C, 45.7; H, 5.1; N, 14.4.
Crystal shape/color
block/brown
3
Crystal size (mm ) 0.18 × 0.17 × 0.17 0.27 × 0.26 × 0.26
Crystal system
Space group
a (Å)
Triclinic
P–1
Monoclinic
P21/n
2
8.284(2)
10.959(3)
14.083(3)
98.236(2)
101.229(2)
106.105(2)
1178.2(5)
2
9.845(1)
24.025(3)
10.457(2)
90
93.632(2)
90
2468.4(6)
4
1.415
Synthesis of [Co(L )(PEA)(N3)] (2)
b (Å)
To a stirring solution of CoCl2·6H2O (23.8 mg, 0.1 mmol)
2
c (Å)
in MeOH (10 mL) was added an equimolar quantity of HL
◦
α ( )
(
0
(
25.4 mg, 0.1 mmol), N-phenylethane-1,2-diamine (13.6 mg,
.1 mmol), and sodium azide (6.5 mg, 0.1 mmol) in MeOH
10 mL), and a few drops of triethylamine. The mixture was
◦
β ( )
◦
γ ( )
V (Å )
3
stirred at room temperature for 1 h to give a deep brown solu-
tion, which was left undisturbed at room temperature to slow
evaporation of the solvent. Brown crystals of the complex suit-
able for X-ray diffraction were obtained after a few days. The
crystals were isolated by filtration, and were washed with cold
Z
3
Dc (g/cm )
1.619
1.455
592
−1
µ (MoKα) (cm )
F(000)
0.835
1096
2.13/27.00
–12/12, –29/28,
–6/13
o
2
θ range ( )
2.22/27.00
–10/10, –13/13,
–14/17
methanol and dried under vacuum. Yield: 62% based on HL .
−1
Index ranges
IR (cm , KBr pellets): 3321 (sh, m), 3222 (sh, m), 2039 (vs),
592 (s), 1536 (m), 1491 (s), 1434 (s), 1335 (s), 1304 (w), 1233
(
h, k, l)
1
Independent
reflections
Observed
4873
5222
(m), 1200 (w), 1160 (w), 1142 (w), 1128 (w), 1083 (w), 1049
(w), 1028 (m), 861 (w), 804 (w), 757 (m), 727 (w), 705 (m), 605
(w), 534 (w), 505 (w), 477 (w), 447 (w), 423 (w). Anal. Calcd.
(Rint = 0.0551)
(Rint = 0.0234)
2847
4094
reflections
for C24H29ClCoN7O: C, 54.8; H, 5.6; N, 18.6. Found: C, 55.0;
H, 5.5; N, 18.7.
[
I ≥ 2σ(I)]
T(min)/T(max)
Data/restraints/
parameters
0.7797/0.7900
4873/0/318
0.8060/0.8122
5222/2/314
X-Ray Crystallography
X-ray diffraction data were collected on a Bruker SMART
Goodness of fit
0.970
1.024
1000 CCD area detector diffractometer, using graphite
2
on F
monochromatized Mo Kα radiation (λ = 0.71073 Å). The
R1, wR2
0.0674, 0.1536
0.0351, 0.0785
structures were solved by direct methods using the program
a
[
14]
[
I ≥ 2σ(I)]
SHELXS-97. Refinements were done by the full-matrix least-
a
2
[15]
R1, wR2 (all data)
0.1222, 0.1812
0.800 and –0.501
0.0515, 0.0857
0.341 and –0.259
squares on F using SHELXL-97. Non-hydrogen atoms were
refined with anisotropic displacement parameters. The H atoms
attached to the secondary amino groups in (2) were located from
a difference Fourier map and refined isotropically, with N–H dis-
tances restrained to 0.90(1) Å. All other hydrogen atoms were
placed in geometrically idealized positions and constrained to
ride on their parent atoms. The crystal data, data collection and
refinement parameters for the two compounds are presented in
Table 1. The coordinate bond lengths and angles are listed in
Table 2. Hydrogen bonding information is given in Table 3.
Large diff. peak
3
and hole (e/Å )
(
ꢀ/σ)max
0.000
0.000
ꢀ
ꢀ
ꢁꢀ ꢂ
ꢃ ꢀ ꢂ ꢃ ꢄ
aR
2
2
2
2 2
1/2.
1
=
||F
o
| – |F
c
||/ |F
o
|, wR
2
=
w F
o
– F
c
/
w F
o
complexes by the reaction of the Schiff base ligands, cobalt chlo-
ride, and sodium azide in MeOH; however, no single crystals can
be obtained. Occasionally, when additional 2-aminoethanol or
N-phenylethane-1,2-diamine is added to the reaction mixture, it
can obtain well-shaped single crystals during the crystallization.
RESULTS AND DISCUSSION
1
2
The tridentate Schiff base ligands (H2L and HL ) were syn- The cobalt complexes are soluble in common organic solvents
thesized by the condensation reaction of 2-acetylphenol with but insoluble in diethyl ether and water. The analytical data
2
-aminoethanol and N-phenylethane-1,2-diamine, respectively, for the compounds are in good agreement with the calculated
in 1:1 molar ratio in MeOH. We have tried to prepare the cobalt values.

SYNTHESIS, STRUCTURES, AND ANTIMICROBIAL STUDIES OF COBALT(III) COMPLEXES
111
TABLE 2
Selected bond lengths (Å) and angles ( ) for (1) and (2)
TABLE 3
◦
◦
Distances (Å) and angles ( ) involving hydrogen bonding of
(
1) and (2)
(
1)
Angle
d(H···A) d(D···A) d(D···A) (D–H···A)
Co1-O1
Co1-O4
Co1-N1
Co2-O2
Co2-O4
Co2-N2
1.848(4)
1.958(4)
1.879(5)
1.924(4)
1.908(4)
1.874(5)
95.3(2)
89.1(2)
91.0(2)
91.7(2)
91.9(2)
95.5(2)
79.7(2)
100.3(2)
173.9(2)
94.2(2)
80.8(2)
95.3(2)
81.9(2)
93.7(2)
88.2(2)
Co1-O2
Co1-O5
Co1-N4
Co2-O3
Co2-O5
Co2-N3
1.909(4)
1.939(4)
1.942(6) (1)
1.863(4) N3–H3B···N6
1.918(4) N3–H3A···N4
1.942(5)
174.4(2)
94.7(2)
81.7(2)
88.5(2)
173.6(2)
165.9(2)
79.0(2)
95.7(2)
89.3(2)
170.0(2)
95.5(2)
D–H···A
#
1
0.90
0.90
2.13
2.62
3.004(8)
3.435(9)
165
151
#
2
(
2)
O1-Co1-N1
N1-Co1-O2
N1-Co1-O5
O1-Co1-N4
O2-Co1-N4
O1-Co1-O4
O2-Co1-O4
N4-Co1-O4
O3-Co2-O4
O3-Co2-O5
O4-Co2-O5
N2-Co2-O2
O5-Co2-O2
N2-Co2-N3
O5-Co2-N3
O1-Co1-O2
O1-Co1-O5
O2-Co1-O5
N1-Co1-N4
O5-Co1-N4
N1-Co1-O4
O5-Co1-O4
O3-Co2-N2
N2-Co2-O4
N2-Co2-O5
O3-Co2-O2
O4-Co2-O2
O3-Co2-N3
O4-Co2-N3
O2-Co2-N3
#
3
N3–H3A···N7
0.90
2.27
3.071(3)
147
174(3)
175(3)
N4–H4A···Cl1
0.90(2) 2.28(2) 3.180(2)
0.89(2) 2.37(2) 3.256(2)
N2–H2···Cl1
Symmetry transformations used to generate the equivalent atoms:
1: –x, 2–y, 1–z; #2: 1+x, y, z; #3: –x, 2–y, –z.
#
−1
with those of the free Schiff bases, 1623 cm for (1) and 1621
−1
cm for (2). The weak bands indicative of the ν(Co–N) and
−1
ν(Co–O) appear in the range 520–410 cm .
80.6(2) Structure Description of (1)
90.1(2)
The molecular structure of (1) is shown in Figure 1. The
93.1(2) complex is a dinuclear cobalt(III) compound, with Co···Co dis-
168.9(2) tance of 2.561(1) Å. Each Co atom in the complex is hexa-
coordinated with a N2O4 donor set, forming an octahedral co-
(
2)
ordination. The Co1 atom is coordinated by the O1, N1, and
O2 atoms of one Schiff base ligand, and by the O4 atom of
another Schiff base ligand, at the equatorial plane, and by the
O5 atom of a Schiff base ligand and one azide N atom at the
axial positions. The Co2 atom is coordinated by the O3, N2,
and O4 atoms of one Schiff base ligand, and by the O5 atom of
-aminoethanolic ligand, at the equatorial plane, and by the N3
Co1-O1
Co1-N2
Co1-N4
1.865(1)
2.030(2)
2.064(2)
94.9(1)
90.5(1)
179.1(1)
177.5(1)
87.3(1)
88.0(1)
174.3(1)
93.7(1)
Co1-N1
Co1-N3
Co1-N5
O1-Co1-N5
O1-Co1-N3
N5-Co1-N3
N1-Co1-N2
N3-Co1-N2
N1-Co1-N4
N3-Co1-N4
1.911(2)
1.959(2)
1.939(2)
90.8(1)
86.0(1)
89.2(1)
86.8(1)
92.4(1)
95.1(1)
85.2(1)
O1-Co1-N1
N1-Co1-N5
N1-Co1-N3
O1-Co1-N2
N5-Co1-N2
O1-Co1-N4
N5-Co1-N4
N2-Co1-N4
2
atom of 2-aminoethanolic ligand, and the O2 atom of another
Schiff base ligand, at the axial positions. The coordination ge-
ometry is distorted in both cases, with the trans and cis angles
◦
lying in the ranges of 165.9(2)–174.4(2) and 79.0(2)–100.3(2) ,
respectively. The Co–O and Co–N bond distances in the com-
plex are comparable to those observed in similar cobalt(III)
complexes with Schiff bases.[
16–18]
The azide group is almost
Infrared Spectroscopy
In the infrared spectra of the free Schiff bases, there are broad
◦
linear [N4–N5–N6 174.3(5) ] and coordinates to the Co atom
◦
in a bent fashion [N5–N4–Co1 = 123.2(5) ]. It is very interest-
−1
bands centered at about 3432 cm , assigned to the vibration of
the hydroxyl groups, which are absent in the cobalt complexes.
ing that there forms three four-membered roof-shaped chelate
rings between the two Co atoms.
−
1
2
−1
The middle and sharp bands at 3337 cm for HL , 3321 cm
In the crystal structure of (1), the adjacent two molecules
are linked through intermolecular N–H···N hydrogen bonds,
forming a dimer, as shown in Figure 2.
−1
for (1), and 3321 and 3222 cm for (2) are assigned to the N–H
vibrations. The existence of two different peaks in (2) indicates
that there are two types of N–H groups (NH and NH2). The low
values of ν(N–H) are attributed to the fact that the NH groups Structure Description of (2)
are coordinated to the metal atoms. The intense bands appeared The molecular structure of (2) is shown in Figure 3. The
at 2034 cm for (1) and 2039 cm for (2) are attributed to the complex is a mononuclear cobalt(III) compound. The Co atom
−
1
−1
−1
azide ligands. The strong peaks at 1614 and 1596 cm for (1) in the complex is hexa-coordinated with a N5O donor set, form-
and 1592 cm for (2) are attributable to the azomethine groups, ing an octahedral coordination. The Co1 atom is coordinated
ν(C N), which are shifted toward lower frequencies compared by the O1, N1, and N2 atoms of the Schiff base ligand, and by
−
1

112
W.-Y. FANG ET AL.
FIG. 1. Molecular structure of (1) with 30% probability thermal ellipsoids.
◦
the N3 atom of the N-phenylethane-1,2-diamine ligand, at the lying in the ranges of 174.3(1)–179.1(1) and 85.2(1)–95.1(1) ,
equatorial plane, and by the N4 atom of the N-phenylethane-1,2- respectively. The Co–O and Co–N bond distances in the com-
diamine ligand and one azide N atom, at the axial positions. The plex are comparable to those observed in (1) and other similar
coordination geometry is distorted, with the trans and cis angles cobalt(III) complexes with Schiff bases.[
16–18]
The azide group
◦
is almost linear [N5–N6–N7
175.6(2) ] and coordinates to
◦
the Co atom in a bent fashion [N6–N5–Co1 = 118.8(1) ].
In the crystal structure of (2), the Cl anions are linked to the
cobalt complex cations through intermolecular N–H···Cl hydro-
gen bonds. The adjacent molecules are further linked through
intermolecular N–H···N hydrogen bonds, forming a dimer, as
shown in Figure 4.
Antimicrobial Test
Antimicrobial tests were measured according to the litera-
ture method.[ The compounds were tested for antimicrobial
activity against Bacillus subtilis, Staphylococcus aureus, Pseu-
domonas fluorescence, Escherichia coli, Pseudomonas aerugi-
nosa, and Bacillus cereus. A standard inoculum was introduced
onto the surface of sterile agar plates, and a sterile glass spreader
was used for even distribution of the inoculum. The discs mea-
suring 6.0 mm in diameter were sterilized by dry heat at 413 K
for 1 h. The sterile discs previously soaked in a known concentra-
tion of the test compounds were placed in nutrient agar medium.
Solvent and growth controls were maintained. The plates were
inverted and incubated for 24 h at 310 K. Penicillin was used as
a standard drug. The inhibition zones were measured and com-
pared with the control. The minimum inhibitory concentrations
of the compounds are given in Table 4. Minimum inhibitory con-
centration (MIC) was determined by broth dilution technique.
The nutrient broth, which contained logarithmic serially twofold
diluted amount of the two compounds and the control, was inoc-
19]
5
ulated with approximately 5 × 10 c.f.u. of actively dividing bac-
terial cells. The cultures were incubated for 24 h at 310 K and the
growth was monitored visually and spectrophotometrically.
The tests show that both complexes have effective activity
against the bacteria, and even stronger than the penicillin for
Pseudomonas fluorescence and Escherichia coli. For Bacillus
FIG. 2. Molecular packing of (1), viewed along the a-axis. Intermolecular
hydrogen bonds are drawn as dashed lines.

SYNTHESIS, STRUCTURES, AND ANTIMICROBIAL STUDIES OF COBALT(III) COMPLEXES
113
FIG. 3. Molecular structure of (2) with 30% probability thermal ellipsoids.
subtilis and Staphylococcus aureus, the complexes show rela-
tively weak activity than the penicillin.
CONCLUSIONS
Two new cobalt(III) complexes with Schiff bases have been
prepared, and their structures were characterized by X-ray crys-
tallography. The complexes show effective antimicrobial ac-
tivity against Bacillus subtilis, Staphylococcus aureus, Pseu-
domonas fluorescence, and Escherichia coli.
SUPPLEMENTARY MATERIALS
CCDC–833462 and 833463 contain the supplementary crys-
tallographic data for this article. These data can be obtained free
of charge at http://www.ccdc.cam.ac.uk/conts/retrieving.html or
from the Cambridge Crystallographic Data Center, 12 Union
Road, Cambridge CB2 1EZ, UK; Fax: +44–1223-336–033; E-
FIG. 4. Molecular packing of (2), viewed along the a-axis. Intermolecular mail: deposit@ccdc.cam.ac.uk.
hydrogen bonds are drawn as dashed lines.
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D.; Yusuff, K.K.M. Template synthesis and spectral characterization of
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and L-histidine. J. Coord. Chem. 2011, 64, 525.
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. Vyas, K.M.; Shah, V.K.; Jadeja, R.N. Synthesis and characterization of
Ni(II) complexes of O,N-donor Schiff bases derived from acyl pyrazolone
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TABLE 4
MIC values (µg/ml) of the antimicrobial activity of (1) and (2)
3
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