Synthesis, crystal structures, and antibacterial activity of copper(II) and cobalt(III) complexes derived from 2-{1-[2-(2-hydroxyethylamino)ethylimino] ethyl}phenol

Article abstract of DOI:10.1080/15533174.2010.538032

A new copper(II) complex [Cu(HEP)(N₃)] (1), and a new cobalt(III) complex [Co(HEP)(AE)]·Cl·H₂O (2), where HEP is 2-{1-[2-(2-hydroxyethylamino)ethylimino]ethyl}phenolate, AE is 2-(2-aminoethylamino)ethanol, were prepared and character

Full text of DOI:10.1080/15533174.2010.538032

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Synthesis, Crystal Structures, and Antibacterial
Activity of Copper(II) and Cobalt(III)
Complexes Derived from 2-{1-[2-(2-
Hydroxyethylamino)ethylimino]ethyl}phenol
Zhi-Xi Hang a , Bo Dong b & Xing-Wen Wang c
a College of Biological and Chemical Engineering, Anhui Polytechnic University, Wuhu, P.
R. China
b College of Chemical Engineering, Nanjing Forestry University, Nanjing, P. R. China
c Department of Biological and Enviromental Engineering, Hefei University, Hefei, P. R.
China
Published online: 19 Feb 2011.
To cite this article: Zhi-Xi Hang , Bo Dong & Xing-Wen Wang (2011) Synthesis, Crystal Structures, and Antibacterial
Activity of Copper(II) and Cobalt(III) Complexes Derived from 2-{1-[2-(2-Hydroxyethylamino)ethylimino]ethyl}phenol,
Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:2, 193-198
To link to this article: http://dx.doi.org/10.1080/15533174.2010.538032
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:193–198, 2011
Copyright © Taylor & Francis Group, LLC
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2010.538032
Synthesis, Crystal Structures, and Antibacterial Activity of
Copper(II) and Cobalt(III) Complexes Derived from
2-{1-[2-(2-Hydroxyethylamino)ethylimino]ethyl}phenol
Zhi-Xi Hang,1 Bo Dong,2 and Xing-Wen Wang3
1College of Biological and Chemical Engineering, Anhui Polytechnic University, Wuhu, P. R. China
2College of Chemical Engineering, Nanjing Forestry University, Nanjing, P. R. China
3Department of Biological and Enviromental Engineering, Hefei University, Hefei, P. R. China
tential antimicrobial activity.[8−9] In this paper, a new cop-
A new copper(II) complex [Cu(HEP)(N3)] (1), and a new
cobalt(III) complex [Co(HEP)(AE)]·Cl·H2O (2), where HEP is 2-
{1-[2-(2-hydroxyethylamino)ethylimino]ethyl}phenolate, AE is 2-
(2-aminoethylamino)ethanol, were prepared and characterized by
elemental analysis, IR spectra, and single crystal X-ray diffraction.
Complex (1) crystallizes in the monoclinic space group P21/c with
per(II) complex [Cu(HEP)(N3)] (1), and a new cobalt(III)
complex [Co(HEP)(AE)]·Cl·H2O (2), where HEP is 2-{1-
[2-(2-hydroxyethylamino)ethylimino]ethyl}phenolate (Scheme
1), AE is 2-(2-aminoethylamino)ethanol, were prepared and
characterized. The in vitro antibacterial activity of the ligands
and the complexes was evaluated. To our knowledge, only one
copper(II) complex derived from the Schiff base ligand has been
reported.[10]
˚
˚
unit cell dimensions a = 9.969(3) A, b = 19.218(3) A, c = 7.272(2)
◦
3
˚
˚
A, β = 108.788(3) , V = 1319.0(6) A , Z = 4, R1 = 0.0424 and
wR2 = 0.1116. Complex (2) crystallizes in the triclinic space group
˚
˚
P-1 with unit cell dimensions a = 7.205(2) A, b = 9.976(3) A, c =
◦
◦
◦
˚
16.737(5) A, α = 98.522(4) , β = 102.076(4) , β = 96.218(4) ,
2. EXPERIMENTAL
3
˚
V = 1151.4(6) A , Z = 2, R1 = 0.0614 and wR2 = 0.1308. The Cu
atom in (1) is four-coordinate in a square planar geometry. The Co
atom in (2) is six-coordinate in an octahedral geometry. The in vitro
antibacterial activity of the ligands and the complexes was tested
2.1. Materials and Measurements
All chemicals were available commercially as AR grade and
against the bacteria Staphylococcus aureus, Bacillus subtilis, Kleb- were used without further purification. C, H, and N elemental
siella pneumonia, Pseudomonas aeruginosa and Escherichia coli.
analyses were performed on a Vario-EL-III analyzer. The IR
spectra were recorded on a Perkin Elmer 2000 spectrophotome-
–1
Keywords antibacterial activity, cobalt, copper, crystal structure,
ter with KBr pellets in the region 4000–400 cm
.
Schiff base, synthesis
Caution: Sodium azide and copper(II) perchlorate are po-
tentially explosive, only a small quantity should be used and
handled with great care.
1. INTRODUCTION
Schiff bases derived from the condensation of aldehydes
with organic amines are a kind of versatile ligands in co-
ordination chemistry due to their easy synthesis and wide
applications.[1−4] Considerable attention has been focused on
the biological properties of Schiff bases and their metal
complexes.[5−7] Recent research indicates that in the pres-
ence of metal ions, the phenolic-containing compounds are be-
lieved to damage the cytoplasmic membrane, and show po-
2.2. Synthesis of the Schiff Base Ligand
1-(2-Hydroxyphenyl)ethanone (1.0 mmol, 136.2 mg) and 2-
(2-aminoethylamino)ethanol (1.0 mmol, 104.2 mg) were mixed
in 50 mL methanol and then stirred and refluxed for 30 min.
The solvent was removed by distillation to give yellow product.
Yield: 93%. Analysis calculated for C12H18N2O2: C, 64.8; H,
8.2; N, 12.6%; found: C, 64.6; H, 8.2; N, 12.7%.
2.3. Synthesis of [Cu(HEP)(N3)] (1)
A methanol solution (10 mL) of copper(II) perchlorate
(0.1 mmol, 37.0 mg) was added with stirring to a methanol
solution (10 mL) of the Schiff base (0.1 mmol, 22.2 mg), 2-
(2-aminoethylamino)ethanol (0.1 mmol, 10.4 mg), and sodium
azide (0.1 mmol, 6.5 mg). The mixture was stirred at ambi-
ent conditions for 30 min to give a blue solution, which was
Received 17 June 2010; accepted 15 July 2010.
The author acknowledges the Pivot Construction Subject of the Ap-
plied Chemistry and the Teaching Group of the Courses Construction
on Engineering Course Chemistry for financial support.
Address correspondence to Zhi-Xi Hang, College of Biological and
Chemical Engineering, Anhui Polytechnic University, Wuhu 241000,
P. R. China. E-mail: hangzhx@163.com
193

194
Z.-X. HANG ET AL.
TABLE 1
Crystal data and refinement parameters for the complexes
N
OH
N
Complex
(1)
(2)
OH
Formula
FW
C12H17CuN5O2
326.8
C17H31ClCoN5O4S
495.9
SCH. 1. The Schiff base ligand.
Crystal shape/color
Crystal size/mm3
Crystal system
Space group
Block/blue
block/brown
0.32 × 0.30 × 0.27 0.32 × 0.30 × 0.27
allowed to evaporate slowly in air for a week, yielding blue
single crystals, which were collected by filtration, washed with
methanol and dried in air. Yield: 63% (based on the Schiff base
ligand). Analysis calculated for C12H17CuN5O2: C, 44.1; H, 5.2;
N, 21.4%; found: C, 43.8; H, 5.4; N, 21.6%.
Monoclinic
P 21/c
Triclinic
P -1
˚
a/A
9.969(3)
19.218(3)
7.272(2)
7.205(2)
9.976(3)
16.737(5)
98.522(4)
102.076(4)
96.218(4)
1151.4(6)
2
0.71073
298(2)
0.984
0.7437
0.7771
˚
b/A
˚
c/A
α/◦
β/◦
γ /◦
2.4. Synthesis of [Co(HEP)(AE)]·Cl·H2O (2)
108.788(3)
A methanol solution (10 mL) of copper(II) chloride
(0.1 mmol, 17.0 mg) was added to a methanol solution
(10 mL) of the Schiff base (0.1 mmol, 22.2 mg), 2-(2-
aminoethylamino)ethanol (0.1 mmol, 10.4 mg), and ammonium
thiocyanate (0.1 mmol, 7.6 mg). The mixture was stirred at
ambient conditions for 30 min to give a deep brown solution,
which was allowed to evaporate slowly in air for 13 days, yield-
ing brown single crystals, which were collected by filtration,
washed with methanol, and dried in air. Yield: 32% (based on the
Schiff base ligand). Analysis calculated for C17H31ClCoN5O4S:
C, 41.2; H, 6.3; N, 14.1%; found: C, 41.5; H, 6.4; N, 13.8%.
3
˚
V /A
1319.0(6)
4
Z
˚
λ (MoKα)/A
T /K
0.71073
298(2)
1.665
0.6178
0.6620
10459
2866
µ (MoKα)/cm−1
Tmin
Tmax
Measured reflections
Unique reflections
Observed reflections
9350
4869
3121
2129
Parameters/restraints 186/1
279/7
1.017
2.5. Crystal Structure Determination
Goodness of fit on F2 1.061
R1, wR2 [I ≥ 2σ(I)]a 0.0424, 0.1116
0.0614, 0.1307
0.1076, 0.1522
ꢀ
The suitable single crystals of the complexes were mounted
on glass fibers for data collection performed on a Bruker
SMART 1000 CCD area diffractometer equipped with a
R1, wR2 (all data)a
0.0636, 0.1286
ꢀ
ꢀ
aR1
w(Fo2)2]1/2
=
||Fo| − |Fc||/ |Fo|, wR2
=
[
w(Fo2-Fc2)2/
˚
graphite-monochromatic Mo Kα radiation (λ = 0.71073 A)
ꢀ
at 298 K. The unit cell dimensions were obtained with the
least-squares refinements and the structures were solved by di-
rect methods using SHELXTL-97 program.[11] The final refine-
ment was performed by full-matrix least-squares methods with
anisotropic thermal parameters for the non-hydrogen atoms on
F2. The amino H atoms in both complexes, and hydroxyl H atom
of (2), were located from difference Fourier maps and refined
isotropically, with N−H, O−H, and H· · ·H distances restrained
this paper, the Schiff base ligand was readily synthesized by
condensation reaction of 1-(2-hydroxyphenyl)ethanone and 2-
(2-aminoethylamino)ethanol in methanol with a beaker, with a
very high yield.
The complexes were easily prepared by reaction of equimo-
lar quantities of the metal salts, Schiff base ligand, 2-(2-
aminoethylamino)ethanol, and sodium azide or ammonium
thiocyanate in methanol. We have intended to use 2-(2-
aminoethylamino)ethanol, sodium azide, and ammonium thio-
cyanate as bridging ligands when coordination, however,
they acted as terminal ligands in both complexes. The 2-(2-
aminoethylamino)ethanol ligand only coordinates to the Co
atom in a bidentate fashion. The terminal hydroxyl group of the
Schiff base ligand coordinates to two Cu atoms in the dinuclear
copper(II) complex reported by Cros and coworkers; however,
in this paper, the hydroxyl groups in both complexes are not par-
ticipate in coordination. This might be caused by the addition
of the deprotonating agent triethylamine in the synthesis of the
˚
to 0.90(1), 0.85(1), and 1.43(2) A, respectively. Other H atoms
were placed in calculated positions and constrained to ride on
their parent atoms. Multi-scan absorption correction was applied
by using the SADABS program.[12] The crystallographic data
and experimental details for structural analysis of the complexes
are summarized in Table 1. Selected bond lengths and angles
are given in Table 2. Hydrogen bonds are listed in Table 3. Crys-
tallographic data for the complex has been deposited with the
Cambridge Crystallographic Data Centre (CCDC 780758 (1)
and 780759 for (2)).
3. RESULTS AND DISCUSSION
The Schiff base ligand was first synthesized by Cros and dinuclear copper(II) complex, and no such agents were used in
coworkers using a Dean and Stark apparatus in benzene.[10] In the present work.

COPPER(II) AND COBALT(III) COMPLEXES
195
TABLE 2
TABLE 3◦
˚
Hydrogen-bond geometry (A, ) for the complexes
◦
˚
Selected bond lengths (A) and bond angles ( ) for the
complexes
D–H· · ·A
(1)
D–H
H· · ·A
D· · ·A D–H· · ·A
(1)
Cu1-O1
Cu1-N2
O1-Cu1-N1
N1-Cu1-N3
N1-Cu1-N2
1.857(2)
1.989(3)
Cu1-N1
Cu1-N3
1.965(3)
1.983(3)
89.96(12)
175.89(11)
92.99(12)
N2–H2A· · ·O1i 0.898(10) 2.32(3) 3.057(4) 139(4)
O2–H2· · ·N5i
(2)
0.82
2.09
2.905(4) 171
91.88(10)
167.51(15)
85.85(11)
O1-Cu1-N3
O1-Cu1-N2
N3-Cu1-N2
O3–H3A· · ·O4ii 0.845(10) 1.969(14) 2.811(7) 173(6)
N4–H4A· · ·O3iii 0.900(10) 2.36(4) 3.072(6) 136(4)
N4–H4B· · ·Cl1iv 0.900(10) 2.48(3) 3.279(4) 148(4)
(2)
N3–H3· · ·Cl1v 0.84(6)
N2–H2· · ·Cl1v 0.88(6)
O2–H2A· · ·Cl1v 0.82
2.72(6) 3.546(4) 166(5)
2.35(6) 3.205(4) 162(5)
2.35
Co1-O1
Co1-N2
Co1-N4
1.880(3)
1.996(4)
Co1-N1
Co1-N3
1.902(3)
2.014(4)
1.909(4)
91.69(15)
84.99(15)
92.73(16)
87.20(15)
93.97(16)
91.39(15)
85.44(16)
3.111(5) 155
1.960(4)
Co1-N5
Symmetry codes: (i) x, 1/2 − y, 1/2 + z; (ii) 1 + x, y, 1 +z; (iii)
O1-Co1-N1
N1-Co1-N5
N1-Co1-N4
O1-Co1-N2
N5-Co1-N2
O1-Co1-N3
N5-Co1-N3
N2-Co1-N3
93.83(13)
90.43(15)
176.65(17)
178.90(14)
88.71(16)
87.88(15)
178.15(15)
91.69(16)
O1-Co1-N5
O1-Co1-N4
N5-Co1-N4
N1-Co1-N2
N4-Co1-N2
N1-Co1-N3
N4-Co1-N3
–1 + x, y, z; (iv) x, 1 + y, z; (v) 1 + x, 1 + y, z.
to lower frequencies in the spectra of the complexes, 1626 cm−1
for (1) and 1627 cm−1 for (2). For (1), the strong absorption
band indicative of the azide group is at 2027 cm−1. For (2), the
strong absorption band indicative of the thiocyanate group is at
2093 cm−1. The spectra of the complexes also show some new
bands in the region 500–400 cm−1, which reflect the formation
of M–O and M–N bonds.[13−14]
3.1. IR Spectra
3.2. Structure Description of (1)
The Schiff base ligand and the two complexes show weak
and sharp absorption bands in the region 3200–3300 cm−1 cor-
The molecular structure of the complex (1) is shown in Fig-
responding to the ν(–NH) of the amino groups. The weak and ure 1. The Cu atom in the complex is four-coordinated by the
broad absorption bands in the region 3300–3600 cm−1 are as- phenolate O, imine N, and amine N atoms of the Schiff base
signed to the phenolic groups of the Schiff base ligands and ligand, and by one N atom of the azide ligand, forming a square
the water molecules. The strong and sharp band at 1643 for the planar geometry. All the bond lengths and angles are compara-
Schiff base ligand is assigned to the ν(C=N), which is shifted ble to those observed in other copper(II) complexes with square
FIG. 1. The molecule of (1), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

196
Z.-X. HANG ET AL.
TABLE 4
Mean diameter of zone of inhibition (mm) for the antimicrobial activity of the Schiff base and the complexes
Pseudomonas
aeruginosa
Staphylococcus
aureus
Bacillus
subtilis
Klebsiella
pneumonia
Escherichia
coli
Compound
The Schiff base ligand
(1)
(2)
8.3 0.6
11.0 0.8
13.3 0.6
12.1 0.8
12.5 0.8
14.5 0.8
21.7 1.0
25.0 1.0
7.0 0.5
10.3 0.5
16.3 0.8
23.3 1.0
-
5.4 0.5
13.1 0.8
23.2 1.0
17.2 1.0
4.2 0.5
8.3 0.8
15.5 1.0
Streptomycin
planar coordination.[15−17] The coordination around the Cu atom
displays somewhat distortion. The Cu atom deviates from the
least-squares plane defined by the four basal donor atoms by
one amine N atoms of the Schiff base ligand, and one pri-
mary amine N atom of 2-(2-aminoethylamino)ethanol defining
the equatorial plane, and with one secondary amine N atom of
2-(2-aminoethylamino)ethanol and one thiocyanate N atom oc-
cupying the two axial positions. All the bond lengths related
to the Co atom are comparable with those observed in other
similar cobalt(III) complexes with Schiff bases.[18−20] The oc-
tahedral coordination around the Co atom displays somewhat
distortion. The Co atom deviates from the least-squares plane
˚
0.080(2) A. The N1-Cu1-N2 bond angle is deviate from the
value for an ideal square planar geometry by 4.2(2)◦, which is
caused by the strain created by the five-membered chelate ring
Cu1-N1-C9-C10-N2.
In the crystal structure, molecules are linked through inter-
molecular N−H· · ·O and O−H· · ·N hydrogen bonds, to form
chains running along the c axis, as shown by Figure 2.
˚
defined by the four equatorial donor atoms by 0.030(2) A toward
N5. The N1-Co1-N2 and N3-Co1-N4 bond angles are deviate
from the values for an ideal octahedral geometry by 2.8(2) and
4.6(2)◦, respectively, which are caused by the strain created
by the five-membered chelate rings Co1-N1-C9-C10-N2 and
Co1-N3-C14-C13-N4.
In the crystal structure, molecules are linked through in-
termolecular O−H· · ·O, N−H· · ·O, N−H· · ·Cl and O−H· · ·Cl
3.3. Structure Description of (2)
The molecular structure of the complex (2) is shown in
Figure 3. The complex consists of a [Co(HEP)(AE)(NCS)]+
cation, a chloride anion, and a water molecule of crystalliza-
tion. The Co atom in the cation is six-coordinate in an oc-
tahedral geometry, with one phenolate O, one imine N and
FIG. 2. The molecular packing of (1). Intermolecular hydrogen bonds are shown as dashed lines.

COPPER(II) AND COBALT(III) COMPLEXES
197
3.4. Antibacterial Activities
Antibacterial activities of the complexes were tested by
the well diffusion method using Sabouraud dextrose agar and
Mu¨ller Hinton agar.[21] The zone of inhibition was recorded on
the completion of the incubation and the mean diameter for each
complex at 100 µg mL−1 was recorded. The zone of inhibition
was recorded in diameters. Stock solutions of tested compounds
were prepared in dimethyl sulfoxide. The diameters of the zone
of inhibition produced by the compounds were compared with
the standard antibiotics Streptomycin 10 µg per well. Each test
was carried out for three times to minimize the error.
The Schiff base and the two complexes were subjected to
antibacterial activity against Pseudomonas aeruginosa, Staphy-
lococcus aureus, Bacillus subtilis, Klebsiella pneumonia, and
Escherichia coli. The screening results are summarized in Table
4. It can be seen that both complexes have stronger activities than
those of the Schiff base ligand, and the cobalt(III) complex (2)
has stronger activities than those of the copper(II) complex (1).
Such an increased activity of the complexes can be explained
on the basis of Overtone’s concept[22] and Tweedy’s Chelation
theory[23] that the metal complexes have a better activity than the
free ligands. On chelating, the polarity of the metal ion will be
reduced to a greater extent due to the overlap of the ligand orbital
and partial sharing of positive charge of the metal ion with donor
groups. Further, it increases the delocalization of π-electrons
over the whole chelate ring and enhances the lipophilicity
of the complex. This increased lipophilicity enhances the
FIG. 3. The molecule of (2), showing the atom-numbering scheme. Displace-
ment ellipsoids are drawn at the 30% probability level.
hydrogen bonds, to form chains running along the a axis, as
shown by Figure 4.
FIG. 4. The molecular packing of (2), viewed along the b axis. Intermolecular hydrogen bonds are shown as dashed lines.

198
Z.-X. HANG ET AL.
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dicopper(II) complex, Cu2(L-H)(L-2H)ClO4 [L = 2-((2-((o-hydroxy-α-
methylbenzylidene)amino)ethyl)amino)ethanol], with quasi-orthogonal co-
ordination planes. Inorg. Chem. 1987, 26, 596–599.
the metal binding sites on enzymes of micro-organisms.
11. Sheldrick, G.M. SHELXTL-97, Program for X-ray Crystal Structure Solu-
tion; University of Go¨ttingen: Germany, 1997.
12. Sheldrick, G.M. SADABS, Siemens Area Detector Absorption (and Other)
Correction; University of Go¨ttingen: Germany, 1997.
13. Rajasekar, M.; Sreedaran, S.; Prabu, R.; Narayanan, V.; Jegadeesh, R.;
Raaman, N.; Rahiman, A.K. Synthesis, characterization, and antimicrobial
activities of nickel(II) and copper(II) Schiff-base complexes. J. Coord.
Chem. 2010, 63, 136–146.
4. CONCLUSIONS
In this article, two new copper(II) and cobalt(III) complexes
with Schiff base ligands were synthesized and characterized by
elemental analysis, IR spectra, and single crystal X-ray diffrac-
tion. The in vitro antimicrobial test shows that both complexes
have stronger activities than those of the Schiff bases.
14. EI-Metwally, N.M.; Gabr, I.M.; Shallaby, A.M.; EI-Asmy, A.A. Synthesis
and spectroscopic characterization of new mono- and binuclear complexes
of some NH(1) thiosemicarbazides. J. Coord. Chem. 2005, 58, 1145–1159.
15. Adhikary, C.; Mal, D.; Okamoto, K.-I.; Chaudhuri, S.; Koner, S. Synthesis,
characterization, X-ray structure and magnetic study of the azido adducts
of tridentate (NNO) Schiff base copper (II) complexes. Polyhedron 2006,
25, 2191–2197.
16. Zhu, Q.-Y.; Wei, Y.-J.; Wang, F.-W. Azido{1-[2-(dimethylamino)ethylimi-
nomethyl]naphthalenolato}copper(II). Acta Crystallogr. 2006, E62, m983–
m985.
17. Zbiri, M.; Saha, S.; Adhikary, C.,;Chaudhuri, S.; Daul, C.; Koner, S. Asym-
metric µ2-1,1-azido bridged copper(II) complex: Synthesis, X-ray struc-
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18. Zhang, C.-X.; Cui, C.; Lu, M.; Yu, L.; Zhan, Y.-X. In situ synthesis, charac-
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