Synthesis, crystal structure, and antibacterial evaluation of a copper(II) compound derived from 1,2-diaminobenzene- N,N′-bis(3- methoxysalicylideneimine)

Article abstract of DOI:10.1080/15533174.2012.762379

A copper(II) compound, [CuL][CuL(OH₂)]·ClO ₄·0.5CH₃OH, where L = 1,2-diaminobenzene-N, N′-bis(3-methoxysalicylidenei mine), has been synthesized and characterized by means of spectroscopic methods and single-crystal X-ray

Full text of DOI:10.1080/15533174.2012.762379

Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:1385–1389, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.762379
Synthesis, Crystal Structure, and Antibacterial
Evaluation of a Copper(II) Compound Derived From
1,2-Diaminobenzene-N,Nꢀ-bis(3-methoxysalicylideneimine)
Zhen Zhang
School of Chemistry and Chemical Engineering & Experimental Center, Linyi University,
Linyi Shandong, P. R. China
biological activities of Schiff base complexes, in the present arti-
cle, I report a new Schiff base copper compound with the ligand
A copper(II) compound, [CuL][CuL(OH2)]·ClO4·0.5CH3OH,
where L = 1,2-diaminobenzene-N,Nꢀ-bis(3-methoxysalicylidenei
mine), has been synthesized and characterized by means of spec-
troscopic methods and single-crystal X-ray structure determina-
tion. The compound crystallizes in the orthorhombic space group
Cmc21 with unit cell dimensions a = 17.981(3) Å, b = 17.776(3) Å,
c = 14.047(3) Å, V = 4489.8(14) Å3, Z = 4, R1 = 0.0511, and
wR2 = 0.1267. The asymmetric unit of the compound contains one
mononuclear [CuL] unit, in which the Cu atom adopts a square-
planar geometry, one mononuclear [CuL(OH2)] unit, in which the
Cu atom adopts a square-pyramidal geometry, one perchlorate an-
ion, and one half methanol solvate. The compound was tested for
its antibacterial activities to assess its inhibiting potential.
1,2-diaminobenzene-N,Nꢁ-bis(3-methoxysalicylideneimine).
EXPERIMENTAL
General Considerations
All materials were obtained from commercial sources and
used as received. Copper perchlorate was prepared by the
reaction of basic cupric carbonate with perchloric acid in
distilled water. The Schiff base ligand was prepared according
to the literature procedure.[12] Infrared spectra were collected
on a Nicolet 5SXC FT-IR spectrometer (Linyi University,
China) as KBr pellets. Electronic absorption (UV-Vis) spectra
were collected on a Cary 500 UV-Vis-NIR spectrophotometer
(Linyi University, China). Microanalyses for C, H, and N
were performed on a Perkin-Elmer 2400 CHNS/O elemental
analyzer (Linyi University, China).
Keywords antibacterial activity, copper compound, crystal structure,
Schiff base, X-ray diffraction
INTRODUCTION
Schiff bases have often been used as versatile chelating lig-
ands in coordination chemistry. Schiff bases with donors such
as O, N, and S have structure similarities with neutral biolog-
ical systems and due to presence of imine groups are utilized
in elucidating the mechanism of transformation of rasemina-
tion reaction in biological system.[1–3] The Schiff bases pre-
pared from salicylaldehyde and its derivatives are interesting and
have received considerable attention not only for their applica-
tion in coordination chemistry[4–6] but also for their importance
in medicinal and pharmaceutical fields. Most Schiff bases and
their complexes show biological activities including antibacte-
rial,[7–9] antifungal,[9,10] antitumor,[11] anticancer,[10] anticorro-
sion, and anti-inflammatory activities. As a continuation of the
Preparation of the Copper Compound
To a methanolic solution (20 mL) of the Schiff base ligand
(0.38 g, 1 mmol) was added a methanolic solution (10 mL)
of copper perchlorate (0.37 g, 1 mmol). The reaction mixture
was gently heated at 50◦C for 30 min while stirring and the
complex precipitated was recrystallized from methanol, yield-
ing well-shaped single crystals suitable for X-ray diffraction.
Yield: 45%. Elemental Anal. Calcd. for C46H44ClCu2N4O14: C,
53.15; H, 4.27; N, 5.39. Found: C, 52.93; H, 4.40; N, 5.51%.
IR (KBr, cm−1): 1605 (C N). UV-Vis (toluene, λ, nm, (ε, M−1
cm−1)): 325 (21200), 339 (17900), 357 (14500), 403 (11300),
458 (14500), 693 (2730).
Crystal Structure Determination and Refinement
Received 10 February 2012; accepted 20 December 2012.
The author thanks Dr. Zhujun Zhou of Lanzhou University for
collection of X-ray intensity data and Linyi University for supports of
the work.
Address correspondence to Zhen Zhang, School of Chemistry and
Chemical Engineering & Experimental Center, Linyi University, Linyi
Shandong 276005, P. R. China. E-mail: zhangzhen lynu@126.com.
Crystal data, data collection and refinement parameters for
the compound are listed in Table 1. Data were obtained on a
Bruker Apex II diffractometer (Shandong University, China)
equipped with graphite monochromated Mo Kα (λ = 0.71073
Å) radiation. The structure of the compound was solved by di-
rect methods and refined on F2 by full-matrix least-squares using
1385

1386
Z. ZHANG
TABLE 1
Crystal data and structure refinement for the compound
TABLE 2
Selected bond lengths (Å) and angles (◦) for the compound
Empirical formula
M/g mol−1
Crystal size/mm
2θ range/deg
Completeness to 2θ (%)
h; k; l range
Temperature/K
Crystal system
Space group
a/Å
b/Å
c/Å
V/Å3
C46H44ClCu2N4O14
1039.4
0.30 × 0.27 × 0.27
1.61–27.00
100
–22, 22; –14, 22; –17, 17
298(2)
Orthorhombic
Cmc21
17.981(3)
17.776(3)
14.047(3)
4489.8(14)
4
1.538
2140
1.080
0.759/0.738
12853 (0.0438)
4776
3718
320
Bond lengths
Cu1-O3
Cu2-O1
Cu2-O9
Bond angles
O3-Cu1-O3A
O3-Cu1-N2
O1-Cu2-O1A
O1-Cu2-N1
O1-Cu2-O9
1.896(4)
1.905(3)
2.431(6)
Cu1-N2
Cu2-N1
1.926(4)
1.930(4)
89.2(2)
93.6(2)
87.8(2)
93.6(2)
96.2(2)
O3-Cu1-N2A
N2-Cu1-N2A
O1-Cu2-N1A
N1-Cu2-N1A
N1-Cu2-O9
177.2(2)
83.7(3)
172.7(2)
84.2(3)
90.8(2)
Symmetry operation for A: 1 – x, y, z.
SHELX-97.[13] All non-hydrogen atoms were refined anisotrop-
ically. All hydrogen atoms were placed in calculated positions,
assigned fixed isotropic thermal parameters at 1.2 or 1.5 times
the equivalent isotropic U of the atoms to which they are at-
tached and allowed to ride on their respective parent atoms.
The contributions of these hydrogen atoms were included in the
structure factor calculations. Selected bond lengths and angles
are listed in Table 2.
Z
Dcalc/g cm−3
F(000)
μ/mm−1
Max/min transmission
Reflections collected (Rint)
Independent reflections
Observed reflections
Parameters refined
Restraints
Max/min ꢀρ/e Å−3
R1, wR2 [I > 2σ(I)]
R1, wR2 (all data)
Goodness-of-fit on F2
Antibacterial Activities
43
Antibacterial activities of the compound were investigated
using agar well diffusion method.[14] The activities of the
free Schiff base ligand and standard drug imipenem were
studied against the Staphylococcus aureus and Bacillus sub-
tilis (as gram-positive bacteria) and Pseudomonas aerugi-
nosa, Escherichia coli, and Salmonella typhi (as gram-negative
0.813/–0.384
0.0511, 0.1267
0.0703, 0.1382
1.018
FIG. 1. Molecular structure of the complex. Hydrogen atoms have been omitted for clarity. Symmetry operation for A: 1 – x, y, z.

SYNTHESIS OF A COPPER(II) COMPOUND
1387
bacteria). Strains were obtained from Dalian Medical Univer-
sity. The solution of 2 μg/mL of each compound (free Schiff
base ligand and Imipenem) in DMSO was prepared for testing
against bacteria. Centrifuged pellets of bacteria from a 24 h old
culture containing approximately 104–106 CFU (colony forming
unit) per milliliter were spread on the surface of Muller Hinton
Agar plates. Wells were created in medium with the help of
a sterile metallic bores and nutrients agar media (agar 20 g +
beef extract 3 g + peptones 5 g) in 1000 mL of distilled water
(pH 7.0), autoclaved and cooled down to 45◦C. Then it was
seeded with 10 mL of prepared inocula to have 106 CFU/mL.
Petri plates were prepared by pouring 75 mL of seeded nutrient
agar. The activities were determined by measuring the diame-
ters of the inhibition zones (in mm). The growth inhibition was
calculated according to Rahman et al.[14]
RESULTS AND DISCUSSION
The Schiff base ligand was prepared by a 1:2 condensa-
tion of benzene-1,2-diamine with 3-methoxysalicylaldehyde in
methanol. Reaction of the ligand with copper perchlorate in
methanol gave the copper compound.
Structure Description of the Compound
The crystal structure analysis of the compound reveals that it
contains a [CuL] unit, a [CuL(OH2)] unit, a perchlorate anion,
and one half methanol solvate in the asymmetric unit (Figure 1).
In [CuL], the Cu atom is in a square-planar geometry, coordi-
nated by two imine N and two phenolate O atoms of L. In
[CuL(OH2)], the Cu atom is in a square-pyramidal geometry,
coordinated by two imine N and two phenolate O atoms of
L in the basal plane, and weakly coordinated by one water O
atom at the apical position. In [CuL(OH2)], the C8-C9-C10-
C10A-C9A-C8A (symmetry code for A: 1 – x, y, z) benzene
ring forms a dihedral angle of 1.5(3)◦ with the C1-C6 benzene
ring. In [CuL], the C19-C20-C21-C21A-C20A-C19A benzene
ring forms a dihedral angle of 7.7(3)◦ with the C12-C17 ben-
zene ring. The Cu-O and Cu-N bonds in the basal plane of
[CuL(OH2)] are slightly longer than those in [CuL], and all of
them are in the range of similar Schiff base copper(II) complexes
with square-planar and square-pyramidal geometries.[15–18] In
the three-dimensional crystal structure of the compound, the
[CuL] and [CuL(OH2)] molecules are linked together by four
intermolecular O−H···O hydrogen bonds (Table 3, Figure 2).
FIG. 2. The molecular packing structure of the complex, viewed along the y
axis. Hydrogen bonds are drawn as dashed lines.
Antibacterial Activity
The copper compound, the free Schiff base ligand, and the
standard drug imipenem were screened separately for their an-
tibacterial activities against the bacteria Staphylococcus aureus,
Bacillus subtilis, Pseudomonas aeruginosa, Escherichia coli,
and Salmonella typhi. The diffusion agar technique was used
to evaluate the antibacterial activities of the compounds.[19] The
results are summarized in Table 4. From the results, it is obvious
that the copper compound is more active toward gram-positive
TABLE 3
Hydrogen-bond geometry for the compound (Å, ◦)
D−H···A
D−H
H···A
D···A
D−H···A
O9−H9W···O3
0.94(1)
0.94(1)
2.30(2)
2.02(2)
3.01(3)
2.86(3)
132(3)
147(3)
O9−H9W···O4

1388
Z. ZHANG
TABLE 4
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A copper(II) compound with the Schiff base ligand 1,2-
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