KOOPMHH^HOHHÄS XHMH3, 2014, moM 40, № 2, c. 118-122
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SYNTHESIS, STRUCTURES, AND ANTIBACTERIAL ACTIVITY OF SCHIFF-BASE COBALT(III) COMPLEXES
© 2014 C. H. Dai and F. L. Mao*
Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection, Department of Chemistry, Yancheng Normal College, Yancheng, 224002 P.R. China *E-mail: xpzhougroup@163.com Received January 4, 2013
Two new Schiff-base cobalt(III) complexes, [CoL1(En)N3]Cl (I) and [CoL2N3(OH2)] (II), where L1, L2, and En are 2-[1-(2-aminoethylimino)ethyl]phenolate, bis(5-chlorosalicylidene)ethane-1,2-diamine, and 1,2-ethylenediamine, respectively, have been prepared and characterized by physicochemical methods and single crystal X-ray determination. Complex I crystallizes in monoclinic system space group P2j/n with a =
= 7.113(1), b = 21.385(1), c = 10.599(1) Â, P = 106.067(2)°, V = 1549.2(3) Â3, Z = 4, R1 = 0.0322, and wR2 = = 0.0800. Complex II crystallizes in monoclinic system space group P2j/c with a = 1.679(1), b = 11.145(1), c = 12.493(1) Â, P = 110.553(2)°, V = 1783.5(2) Â3, Z = 4, R1 = 0.0360, and wR2 = 0.0838. Single crystal X-ray diffraction analysis reveals that the Co atoms in the complexes are six-coordinated in octahedral geometry. The complexes were screened in vitro for their antibacterial activity against Bacillus subtillis, Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruguinosa.
DOI: 10.7868/S0132344X14020029
INTRODUCTION
In recent years, considerable attention has been focused on Schiff bases and their complexes in the fields of coordination chemistry and biological chemistry [1—3]. A number of Schiff bases were reported to possess antibacterial, antifungal and antitumor activities [4—6]. Cobalt complexes have been proved to participate in various biological processes [7—10]. Recently, we have reported some Schiff base complexes [11]. As a further study of such complexes, this work deals with the synthesis and antibacterial activity of two new cobalt(III) complexes, [CoL1(En)N3]Cl (I) and [CoL2N3(OH2)] (II), where L1, L2, and En are 2-[1-(2-aminoethylimi-no)ethyl]phenolate, ¿¿s,(5-chlorosalicylidene)ethane-1,2-diamine, and 1,2-ethylenediamine, respectively. The coordination behavior of the ligands toward cobalt ion was investigated via the single crystal X-ray determination.
were determined by complexometric titration with EDTA. IR spectra (4000-400 cm-1), as KBr pellets, were recorded on a Nicolet FT-IR 170X spectropho-tometer.
Synthesis of I. 2-Acetylphenol (0.136 g, 1 mmol), 1,2-ethylenediamine (0.122 g, 2 mmol), sodium azide (0.065 g, 1 mmol), and cobalt chloride (0.238 g, 1 mmol) were mixed in methanol (20 mL). The mixture was stirred at room temperature for 2 h. The insoluble impurities were removed by filtration. Block and brown crystals, suitable for single crystal X-ray diffraction, were formed by slow evaporation of the filtrate in air for a few days. The yield was 51%.
For C12H21ClN7OCo
anal. calcd., %: C, 38.57; H, 5.66; N, 26.23; Co, 15.77. Found, %: C, 38.43; H, 5.59; N, 26.32; Co, 15.95.
EXPERIMENTAL
Materials and methods. 2-Acetylphenol, 5-chloro-salicylaldehyde, and 1,2-ethylenediamine with AR grade were available from Alfa Aesar Company. Sodium azide, cobalt salts and other chemicals with AR grade were purchased from Beijing Chemical Reagent Company and used without further purification. Carbon, hydrogen, and nitrogen were determined on a PerkinElmer 240C microanalyser. The metal contents
IR data (v, cm-1): 3189 (N-H), 2021 (N3), 1595 (CH=N).
Synthesis of II. 5-Chlorosalicylaldehyde (0.313 g, 2 mmol), 1,2-ethylenediamine (0.061 g, 1 mmol), sodium azide (0.065 g, 1 mmol), and cobalt nitrate (0.291 g, 1 mmol) were mixed in methanol (20 mL). The mixture was stirred at room temperature for 2 h. The insoluble impurities were removed by filtration. Block and brown crystals, suitable for single crystal
Table 1. Crystallographic data and refinement parameters for complexes I and II
Table 2. Selected bond lengths (A) and bond angles (deg) for the complexes
Parameter Value
I II
Fw 373.7 454.2
T, K 298(2) 298(2)
Crystal shape/color Block/brown Block/brown
Crystal size, mm 0.27 x 0.23 x 0.23 0.30 x 0.27 x 0.23
Crystal system Monoclinic Monoclinic
Space group P21/n P21/c
a, A 7.113(1) 13.679(1)
b, A 21.385(1) 11.145(1)
c, A 10.599(1) 12.493(1)
P, deg 106.067(2) 110.553(2)
V, A3 1549.2(3) 1783.5(2)
Z 4 4
Pc, g/cm3 1.602 1.691
^(MoJa), cm-1 1.293 1.291
F(000) 776 920
Index ranges (h, k, l) -8/8 -16/16
-26/26 -13/13
-11/12 -15/15
Measured reflections 13792 15424
Independent reflections 2956 3382
Observed reflections 2647 2811
(I > 2CT(T))
Parameters 200 252
Restraints 0 3
T ■ /T * min/ J max 0.7215/0.7552 0.6981/0.7556
Goodness of fit on F 2 1.109 1.041
Rh wR2 (I> 2ct(I))* 0.0322, 0.0800 0.0360, 0.0838
R1, wR2 (all data)* 0.0369, 0.0822 0.0483, 0.0907
APmax/APmin, ^ A-3 0.508, -0.241 0.354, -0.320
Bond d, A Bond d, A
Co(1)-O(1) Co(1)-N(2) Co(1)-N(4) Co(1)-N(1) Co(1)-O(1) Co(1)-N(3) 1.8795(16) 1.9445(18) 1.9703(19) I 1.890(2) 1.9055(18) 1.920(2) Co(1)-N(1) Co(1)-N(3) Co(1)-N(5) I Co(1)-N(2) Co(1)-O(2) Co(1)-O(3) 1.9120(18) 1.9742(19) 1.960(2) 1.887(2) 1.9038(17) 1.9922(18)
Angle ro, deg Angle ro, deg
O(1)Co(1)N(1) 95.59(7) O(1)Co(1)N(2) 178.04(8)
N(1)Co(1)N(2) 85.36(8) O(1)Co(1)N(5) 90.77(9)
N(1)Co(1)N(5) 91.89(9) N(2)Co(1)N(5) 87.49(9)
O(1)Co(1)N(4) 87.91(8) N(1)Co(1)N(4) 93.21(8)
N(2)Co(1)N(4) 93.74(8) N(5)Co(1)N(4) 174.83(8)
O(1)Co(1)N(3) 87.06(7) N(1)Co(1)N(3) 176.57(8)
N(2)Co(1)N(3) 92.05(8) N(5)Co(1)N(3) 90.25(9)
N(4)Co(1)N(3) 84.69(8)
II
N(2)Co(1)N(1) 85.72(10) N(2)Co(1)O(2) 94.50(9)
N(1)Co(1)O(2) 179.11(9) N(2)Co(1)O(1) 177.40(9)
N(1)Co(1)O(1) 92.59(9) O(2)Co(1)O(1) 87.15(7)
N(2)Co(1)N(3) 91.66(10) N(1)Co(1)N(3) 88.47(10)
O(2)Co(1)N(3) 92.39(9) O(1)Co(1)N(3) 90.27(9)
N(2)Co(1)O(3) 89.36(9) N(1)Co(1)O(3) 89.23(8)
O(2)Co(1)O(3) 89.91(8) O(1)Co(1)O(3) 88.64(8)
N(3)Co(1)O(3) 177.41(10)
* R1 = Eii^oi - i^cii/Si^oi, wR2 = Ew(F2 - Fc2)2/Zw( F02)2]1/2.
X-ray diffraction, were formed by slow evaporation of the filtrate in air for a few days. The yield was 45%.
For C16H14Cl2N5O3Co
anal. calcd., %: C, 42.31; H, 3.11; N, 15.42; Co, 12.98. Found, %: C, 42.22; H, 3.07; N, 15.56; Co, 13.17.
IR data (v, cm-1): 3410 (N-H), 2017 (N3), 1606 (CH=N).
X-ray crystallography. Single crystals of complexes I and II suitable for X-ray diffraction were mounted on thin-walled glass fibers and aligned on the Bruker SMART 1000 CCD area diffractometer,
equippted with graphite-monochromated Mo^a radiation (X = 0.71073 A). The 9 ranges for data collection are 1.90°—5.75° for I and 2.42°-25.69° for II. All data were corrected for Lorentz and polarization effects and for the effects of absorption. The structures were solved by the direct method and refined by least-square cycles. The non-hydrogen atoms were refined anisotropically. The hydrogen atoms of the water ligand in II were located from a difference Fourier map and refined isotropically, with O—H and H—H distances restrained to 0.85 and 1.37 A, respectively. The remaining hydrogen were located as riding atoms and not refined. All calculations were performed using SHELXTL-97 [12]. The data collection and refinement parameters are summarized in Table 1. Selected bond lengths and angles are given in Table 2. Crystal-lographic data for the complexes have been deposited with the Cambridge Crystallographic Data Centre
I
120 DAI, MAO
Table 3. Geometric parameters of hydrogen bonds for complexes I and II*
D H-A Distance, Á Angle D—H—A, deg
D—H H-A D—A
N(2)—H(2^)-Cl(1)a 0.90 I 2.59 3.373(2) 146
N(2)—H(2B) ••• Cl(1)b 0.90 2.38 3.173(2) 147
N(3)—H(3^)-Cl(1)b 0.90 2.52 3.367(2) 158
N(3)—H(3B)---O(1)b 0.90 2.29 3.118(2) 153
N(4)—H(4^)-N(6)c 0.90 2.62 3.412(3) 147
N(4)—H(4B)---Cl(1)d 0.90 2.49 II 2.12(2) 3.283(2) 147
O(3)—H(3^)—O(2)e 0.85(1) 2.778(3) 135(3)
O(3)-H(3B)-O(1)e 0.85(1) 1.88(2) 2.658(2) 152(3)
* Symmetry codes: a x, y, - 1 + z; b 1 — x, — y, 1 — z; c —1 + x, y, z; d —1 + x, y, — 1 + z; e — x, 1 — y, — z.
(nos. 931207 (I) and 931208 (II); deposit@ccdc. cam.ac.uk; http://www.ccdc.cam.ac.uk).
Microbiological test. For the microbiological test the filter paper disc method was applied according to the method reported by Gupta and co-workers [13]. The investigated isolates of bacteria were seeded in tubes with nutrient broth. The seeded nutrient broth (1 cm3) was homogenized in the tubes with 9 cm3 of melted (45°C) nutrient agar. The homogeneous suspensions were poured into Petri dishes. The discs of filter paper (diameter 4 mm) were ranged on the cool medium. After cooling on the formed solid medium, 2 x 10-5 dm3 of the investigated compounds were applied using a micropipette. After incubation for 24 h in a thermostat at 25—27°C, the inhibition (sterile) zone diameters were measured and expressed in mm. An inhibition zone diameter over 7 mm indicates that the tested compound is active against the bacteria under investigation. The antibacterial activities of the compounds were tested against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus, respectively. The concentration of each solution was 1.0 x 10-3 mol/L.
RESULTS AND DISCUSSION
ORTEP plots with atom numbering schemes for the complexes I and II are shown in Fig. 1. Complex I contains a mononuclear [CoL1(En)N3] cation and a chloride anion. Complex II is a neutral mononuclear complex. The coordination around the Co atoms in the complexes are best described as distorted octahe-dra. The equatorial plane of the Co coordination of I is defined by O(1), N(1), and N(2) atoms of L1 and N(3) atom of En. The two axial positions are occupied by N(4) atom of En and N(5) atom of the azide ligand. The equatorial plane of the Co coordination of II is defined by O(1), O(2), N(1), and N(2) atoms of L2.
The two axial positions are occupied by O(3) atom of the water ligand and N(3
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