Synthesis, structure, and antimicrobial activity of copper(II) chelates containing imidazole and condensation products of α-amino acids with salicylaldehyde and its derivatives

Article abstract of DOI:10.1134/S1070363213030201

Salicylaldehyde, 5-bromo- and 5-nitrosalicylaldehydes, 2- hydroxynaphthalene-1-carbaldehyde, and 2,3-, 2,4-, and 2,5- dihydroxybenzaldehydes reacted with glycine, alanine, and phenylalanine in ethanol in the presence of imidazole (Im) and copper(II) acetate hydrate to give copper(II) chelates with the composition Cu(Im)(L) · nH₂O (H₂L is the condensation product of the above aldehydes with α-amino acids; n = 0-2). The structure of the complex Cu(Im)(L ¹) [H₂L¹ = 2-(2-hydroxybenzylideneamino)acetic acid] was determined by X-ray analysis. The crystalline structure of [2-(2-hydroxybenzylideneamino)acetato](imidazole)copper is formed by polymeric chains of the Cu(Im)(L¹) molecules linked through bridging oxygen atoms in the carboxy groups of the Schiff base ligand. The coordination unit has a distorted tetragonal pyramid configuration, where the pyramid base is composed of the phenol and carboxy oxygen atoms, CH=N nitrogen atom in the ligand H₂L¹ and imidazole nitrogen atom. The oxygen atom in the carboxy group in the neighboring molecule occupies the apical position of the coordination pyramid. The other coordination compounds also have polynuclear structure with the Schiff base H₂L acting as doubly deprotonated tridentate O,N,O-ligand and bridging carboxy groups. Thermal decomposition of the complexes includes their dehydration (70-95 C), while complete thermal decomposition occurs at 360-530 C. The synthesized complexes showed selective antimicrobial activity in the concentration range from 75 to 300 μg/ml against a number of standard strains of Staphylococcus aureus and Escherichia coli.

Full text of DOI:10.1134/S1070363213030201

ISSN 1070-3632, Russian Journal of General Chemistry, 2013, Vol. 83, No. 3, pp. 530–537. © Pleiades Publishing, Ltd., 2013.
Original Russian Text © A.P. Gulya, K.S. Lozan-Tyrshu, V.I. Tsapkov, Yu.M. Chumakov, E. Zhanno, V.F. Rudik, 2013, published in Zhurnal Obshchei Khimii,
2013, Vol. 83, No. 3, pp. 477–484.
Synthesis, Structure, and Antimicrobial Activity of Copper(II)
Chelates Containing Imidazole and Condensation Products
of α-Amino Acids with Salicylaldehyde and Its Derivatives
A. P. Gulyaa, K. S. Lozan-Tyrshub, V. I. Tsapkova, Yu. M. Chumakovc,
E. Zhannod, and V. F. Rudikb
a Moldova State University, ul. Mateevicha 60, Chisinau, 2009 Moldova
e-mail: dociu1946@yahoo.com
b State University of Medicine and Pharmacy “Nicolae Testemitanu” of the Republic of Moldova, Chisinau, Moldova
c Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Kishinev
d University Claude Bernard Lyon 1, France
Received July 7, 2011
Abstract—Salicylaldehyde, 5-bromo- and 5-nitrosalicylaldehydes, 2-hydroxynaphthalene-1-carbaldehyde, and
2,3-, 2,4-, and 2,5-dihydroxybenzaldehydes reacted with glycine, alanine, and phenylalanine in ethanol in the
presence of imidazole (Im) and copper(II) acetate hydrate to give copper(II) chelates with the composition
Cu(Im)(L)·nH2O (H2L is the condensation product of the above aldehydes with α-amino acids; n = 0–2). The
structure of the complex Cu(Im)(L1) [H2L1 = 2-(2-hydroxybenzylideneamino)acetic acid] was determined by
X-ray analysis. The crystalline structure of [2-(2-hydroxybenzylideneamino)acetato](imidazole)copper is
formed by polymeric chains of the Cu(Im)(L1) molecules linked through bridging oxygen atoms in the carboxy
groups of the Schiff base ligand. The coordination unit has a distorted tetragonal pyramid configuration, where
the pyramid base is composed of the phenol and carboxy oxygen atoms, CH=N nitrogen atom in the ligand
H2L1 and imidazole nitrogen atom. The oxygen atom in the carboxy group in the neighboring molecule
occupies the apical position of the coordination pyramid. The other coordination compounds also have
polynuclear structure with the Schiff base H2L acting as doubly deprotonated tridentate O,N,O-ligand and
bridging carboxy groups. Thermal decomposition of the complexes includes their dehydration (70–95°C),
while complete thermal decomposition occurs at 360–530°C. The synthesized complexes showed selective
antimicrobial activity in the concentration range from 75 to 300 μg/ml against a number of standard strains of
Staphylococcus aureus and Escherichia coli.
DOI: 10.1134/S1070363213030201
Amino acid derivatives possess a number of donor
atoms and are therefore capable of forming various
coordination compounds with metal ions [1–5]. The
structure and physicochemical properties of these
compounds are determined by the nature of the central
atom and its inner-sphere environment. Taking into
account that salicylaldehyde and glycine were often
used as starting compounds, it was interesting to
elucidate how introduction of different substituents
into their molecules may affect the composition,
structure, and properties of the resulting complexes.
properties of copper(II) chelates with imidazole (Im)
and Schiff bases H2L1–9 derived from glycine, alanine,
and phenylalanine, on the one hand, and salicylal-
dehyde (H2L1, H2L7, H2L8), 5-bromo- (H2L2) and 5-
nitrosalicylaldehydes (H2L3), 2-hydroxynaphthalene-1-
carbaldehyde (HL9), and 2,5- (HL4), 2,4- (HL5), and
2,3-dihydroxybenzaldehydes (HL6).
We have found that glycine, alanine, and
phenylalanine in hot (50–55°C) ethanolic solution
reacted with equimolar amounts of salicylaldehyde or
its derivatives, imidazole, and copper(II) acetate
hydrate to produce finely crystalline compounds I–IX.
On the basis of the elemental analysis data (Table 1),
The goal of the present work was to find conditions
of synthesis, determined the structure, and examine the
530

SYNTHESIS, STRUCTURE, AND ANTIMICROBIAL ACTIVITY OF COPPER(II) CHELATES
531
R3
OH
R2
R1
OH
OH
OH
N
N
O
R4
H2L1_8
HL9
H2L1: R1 = R2 = R3 = R4 = H; H2L2: R1 = Br, R2 = R3 = R4 = H; H2L3: R1 = NO2, R2 = R3 = R4 = H; H2L4: R1 = OH, R2 = R3
= R4 = H; H2L5: R1 = R3 = R4 = H; R2 = OH; H2L6: R1 = R2 = R4 = H, R3 = OH; H2L7: R1 = R2 = R3 = H, R4 = CH3; H2L8:
R1 = R2 = R3 = H, R4 = CH2C6H5.
the products were assigned the composition
Cu(Im)(L1–9)·nH2O (I, VI, n = 0; II, III, V, VIII, n =
1; IV, VII, IX, n = 2). Coordination compounds I–IX
are insoluble in diethyl ether, poorly soluble in water
and alcohols, and readily soluble in dimethyl-
formamide (DMF), dimethyl sulfoxide, and aceto-
nitrile. Their yields, elemental analyses, and physical
properties are given in Table 1.
chains are linked to each other by the hydrogen bonds
N3–H···O3 (–x, –y, 1 – z) with the following param-
eters: H···A 1.90, D···A 2.757 Å, ÐDHA 176° (Fig. 2).
The copper coordination polyhedron in complex I is a
distorted tetragonal pyramid; this is confirmed by the
calculation of the trigonality index τ proposed in [6]:
τ = (β – α)/60, where α and β are the largest bond
angles formed by the central atom. If τ = 0, the
coordination entity is an ideal tetragonal pyramid, and
τ = 1 corresponds to an ideal trigonal bipyramid. The τ
value for compounds I is equal to 0.02. The tetragonal
pyramid base is formed by the phenol and carboxy
oxygen atoms O1 and O2, azomethine nitrogen atom N1
and imidazole nitrogen atom N2. These atoms deviate
by –0.013, –0.014, 0.014, and 0.013 Å, respectively,
from the mean-square plane defined by them, and the
copper atom deviates from that plane by 0.120 Å
toward O3a in the neighboring molecule. This O3a atom
occupies the apical position in the Cu1 coordination
pyramid, the Cu1···O3a distance being 2.571(2) Å. The
By analogy with the data of [1, 2], we presumed
that copper template condensation of α-amino acids
with salicylaldehyde and its derivatives gives Schiff
bases H2L1–9 which react with copper acetate in the
presence of imidazole to afford copper chelates I–IX.
By recrystallization from ethanol we succeeded in
isolating single crystals of complex I, and its structure
was determined by X-ray analysis. Compound I
crystallizes in monoclinic crystal system (Tables 2, 3).
Molecules I in crystal form polymeric chains along the
[001] axis through the c glide plane (Fig. 1). These
Table 1. Yields, effective magnetic moments, electrical conductivities, elemental analyses, and complete decomposition
temperatures of copper(II) chelates I–IX
æ,a
Complete decomposition
temperature, °C
Found, %
Calculated, %
Comp. Yield,
μef,a B.M.
Formula
no.
%
Ω–1 cm2 mol–1
Cu
N
Cu
N
65
1.72
3
20.62
13.38
C12H11CuN3O3
20.58
13.61
350
I
66
75
65
68
63
65
75
60
1.73
1.77
1.71
1.75
1.74
1.71
1.74
1.72
3
2
4
3
3
3
2
4
15.43
16.84
17.44
18.27
19.38
17.47
14.97
15.85
10.18
14.90
11.52
12.01
12.74
11.43
9.90
C12H12BrCuN3O4
C12H12CuN4O6
C12H15CuN3O6
C12H13CuN3O5
C12H11CuN3O4
C13H17CuN3O5
C19H19CuN3O4
C16H17CuN3O5
15.66
17.09
17.61
18.54
19.57
17.71
15.24
16.09
10.36
15.07
11.65
12.26
12.94
11.71
10.08
10.64
330
300
340
340
330
360
330
340
II
III
IV
V
VI
VII
VIII
10.37
IX
a
At 294 K.
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532
GULYA et al.
dihedral angle between the CulO1N1 and O1C1C2C3N1
planes is 4.7°. It should be noted that the
corresponding dihedral angle in structurally related
complexes, di(μ-Ophenoxy)-bis{nitrato-2-[2-(hydroxyethyl-
imino)methyl]phenolato(imidazole)copper(II)} [7],
nitrato-2-[2-(hydroxyethylimino)methyl]phenolato(3-
methylpyridine)copper(II) [8], and (3-hydroxypropyl-
salicylaldiminato)copper [9], is 20.6°, 14.9°, and 22.7°,
respectively and that no such folding was observed in
the crystalline structures of nitrato{2-[2-(hydroxy-
ethylimino)methyl]phenolato}copper [10], nitrato-2-
[2-(hydroxyethylimino)methyl]phenolato(4-methyl-
pyridine)copper [11], and {2-[2-(hydroxyethylimino)-
methyl]phenolato}copper [12]. The five-membered
metallacycle Cg2(Cu1O2N1C8C9) in complex I has a
skewed conformation; the N1, C8, and C9 atoms deviate
from the mean-square plane by –0.022, 0.028, and
–0.020 Å, respectively, and the Cu1 and O2 atoms, by
0.009 and 0.006 Å, respectively. The imidazole ring
Cg3(N2N3C10C11C12) is turned through a dihedral angle
of 31.7° with respect to the base of the coordination
polyhedron.
Table 2. Crystallographic data for complex I and parameters
of X-ray diffraction experiment
Parameter
Value
C12H11CuN3O3
308.78
Formula
M
Crystal system
Space group
Z
Monoclinic
Р21/с
4
a, Å
11.058(5)
11.580(5)
9.677(5)
102.76(1)
1208(1)
1.697
b, Å
c, Å
β, deg
V, Å3
d
calc, g/cm3
Irradiation, λ, Å
μ, cm–1
MoKα; 0.7107
1.814
Temperature, K
Crystal habit, mm
Scan mode
293(2)
0.10×0.30×0.35
θ/2θ
θ
max, deg
29.62
According to [13] (CgI···CgJ < 6.0 Å, β < 60.0°,
where β is the angle formed by the CgI···CgJ vector
and normal to the CgI aromatic ring), π–π stacking
exists between the Cg1 and Cg1 rings (1 – x, –y, 1 – z),
as well as between Cg2 and Cg4(C2C3C4C5C6C7) (1 – x,
–y, 1 – z). The distances between the centroids of the
above fragments are 3.373 and 3.486 Å, and the angles
β are 2.5 and 7.5°, respectively. Apart from the π–π
stacking, the interactions metal···Cg and X–H···Cg
(π-ring) are also observed (the distance metal···Cg is
shorter than 4.0 Å, the distance H···Cg is shorter than
3.0 Å, and the angle γ between the H···Cg vector and
the normal to the aromatic ring is less than 30.0° [13]).
Thus, the distance Cg4···Cu1 (1 – x, –y, 1 – z) is 3.779 Å,
the distance between the hydrogen atom and metalla-
cycle centroid C8–H···Cg1 (x, 1/2 – y, 1/2 + z) is 2.660 Å,
and γ = 8.5°.
Ranges of h, k, l
–13 ≤ h ≤ 13
–15 ≤ k ≤ 14
–13 ≤ l ≤ 13
Number of reflections:
total/independent (N1),
Rint/I > 2σ(I), (N2)
10287/3011, 0.0374/2469
Refinement method
Weight schemea
Number of variables
R1/wR2 (N1)
Least squares
K1 0.055, K2 0.42
172
0.0356/0.0992
0.0443/0.1032
R1/wR2 (N2)
Goodness of fit S
Δρ(max), Δρ(min), e/A3
1.143
0.405, –0.466
w = 1/[Σ2(F02) + (K1P)2 + K2P], where P = [max (F02, 0 ) +
2F2c]/3.
a
Visual microscopic analysis of the other coordina-
tion compounds (II–IX) showed phase homogeneity of
their powders which consisted of crystallites with
various shapes. Insofar as we failed to obtain single
crystals of these compounds, their structure was
studied by elemental and thermal gravimetric analysis,
magnetochemistry, and IR spectroscopy.
lengths of the other bonds formed by the copper atom
with those in the pyramid base are Cu1–O1 1.922(1),
Cu1–O2 1.989(2), Cu1–N1 1.942(2), and Cu1–N2
1.970(2) Å (Table 3). The angles formed by the apical
Cu1–O3a bond with the other bonds at the copper atom
range from 90.0 to 98.1°. The volume of the Cu1
coordination pyramid is 6.831 Å3.
Judging by the electrical conductivities (æ) of
compounds I–IX in DMF (Table 1), all these are
nonelectrolytes (æ = 2–4 Ω–1 cm2 mol–1). The effective
The six-membered chelate ring Cg1(CulO1N1C1C2C3)
is slightly folded along the O1···N1 line so that the
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SYNTHESIS, STRUCTURE, AND ANTIMICROBIAL ACTIVITY OF COPPER(II) CHELATES
533
Table 3. Selected bond lengths d and bond angles ω in molecule I
Bond
d, Å
Angle
ω, deg
92.9(1)
90.4(1)
83.2(1)
92.6(1)
172.7(1)
171.4(1)
98.08
Angle
N2Cu1O3а
N1Cu1O2
N2Cu1O2
Cu1O1C3
O1C3C2
C3C2C1
ω, deg
90.15
Cu1–O1
Cu1–O2
Cu1–N1
Cu1–N2
Cu1–O3а
O1–C3
O3–C9
C3–C2
C2–C1
C1–N1
N1–C8
C8–C9
C9–O2
1.922(1)
1.989(2)
1.942(2)
1.970(2)
2.571(2)
1.305(3)
1.242(3)
1.430(3)
1.432(3)
1.285(3)
1.454(3)
1.507(3)
1.273(3)
O1Cu1N1
O1Cu1N2
O2Cu1N1
O2Cu1N2
N1Cu1N2
O1Cu1O2
O1Cu1O3а
O2Cu1O3а
N1Cu1N2
O1Cu1O2
O1Cu1O3а
O2Cu1O3а
N1Cu1O3а
83.2(1)
92.6(1)
127(1)
125.0(2)
122.9(2)
124.6(2)
127.3(2)
113.7(1)
110.1(2
117.7(2)
116(1)
C2C1N1
89.96
C1N1Cu1
Cu1N1C8
N1C8C9
C8C9O2
172.7(1)
171.4(1)
98.08
89.96
C9O2Cu1
95.82
magnetic moments of I–IX at room temperature (294 K,
Table 1) were 1.71–1.77 B.M.; i.e., they are close to
the spin values typical of one unpaired electron.
that Schiff bases H2L1–9 in complexes I–IX behave as
doubly deprotonated tridentate O,N,O-ligands which
are coordinated to the metal ion through the phenol
and carboxy oxygen atoms and azomethine nitrogen
atom to form six- and five-membered chelate rings.
This follows from the low-frequency shift of the
ν(C=N) and ν(COO–) bands by 25–10 cm–1 relative to
the corresponding bands of analogous Schiff bases [2,
3]. The IR spectra of all complexes I–IX contained a
number of new absorption bands in the region 530–
In order to determine the mode of coordination of
ligands H2L1–9 to the central ion we compared the IR
spectra of complexes I–IX with those of the initial α-
amino acids and aldehydes, as well as of previously
described coordination compounds [1–5] of transition
metals with analogous Schiff bases. We found (Table 4)
Fig. 1. Polymeric chains in the crystalline structure of compound I.
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 3 2013

534
GULYA et al.
400 cm–1 due to ν(Cu–N) (530–510 and 430–405 cm–1)
and ν(Cu–O) vibrations (490–450 cm–1). Participation
of the other functional groups in Schiff bases H2L1-9 in
the coordination can be ruled out, for the position of
their characteristic absorption bands was the same as in
the spectrum of I. According to the IR data, the carboxy
group in I–IX is a bridging fragment; this is confirmed
by the presence of νas(COO–) and νs(COO–) absorption
bands at 1609–1605 and 1336–1311 cm–1, respectively.
The difference Δ = νas(COO–) – νs(COO–) is 104–142
cm–1; in keeping with [14], this difference indicates
bridging mode of coordination of the carboxy group.
Thermal gravimetric analysis of complexes I–IX
(Table 1) showed that their thermal decomposition
includes dehydration step (70–95°C). Their complete
decomposition temperatures (330–530°C) depended on
the nature of substituent in the salicylidene fragment of
the Schiff base ligand and decreased in the series H >
Br > OH > NO2 for complexes with similar
compositions.
On the basis of the obtained data we presumed the
following structure of linear chains of complexes I–IX
in crystal.
R1
R2
R3
R1
R2
R3
R1
O
N
N
R4
Cu
O
R2
R3
O
N
N
HN
O
R4
nH2O
Cu
O
O
N
N
HN
O
R4
nH2O
Cu
O
x
HN
O
nH2O
I_VIII
R1 = H, Br, NO2, OH; R2 = H, OH; R3 = H, OH; R4 = H, CH3, CH2C6H5; n = 0–2.
As shown in [1, 2, 5] many complexes of biometals
EXPERIMENTAL
with Schiff bases derived from amino acids selectively
inhibit the growth and replication of various
microorganisms. Coordination compounds I–IX were
tested for antimicrobial activity in vitro (Table 5). The
results showed that complexes I–IX exhibit both
bacteriostatic and bactericidal effects against Gram-
positive (Staphylococcus aureus ATCC 25923,
Bacillus cereus GISK 8035) and Gram-negative test
cultures (Escherichia coli ATCC 25922, Shigela
sonnei, Salmonella abony GISK 03/03) in the
concentration range from 75 to 300 μg/ml. The
minimum inhibitory (MIC) and minimum bactericidal
concentrations (MBC) of complexes I–IX are
determined mainly by the nature of the R substituent in
Schiff base HL1–9, and the antibacterial activity of the
complexes with similar compositions changes in the
series NO2 > H ≥ Br > OH; 3-OH > 4-OH > 5-OH;
C6H5CH2 > Me ≈ H. Furthermore, replacement of the
benzene ring in the Schiff base by naphthalene reduces
the antibacterial activity of the complexes.
The X-ray diffraction data for compound I were
obtained on
a
Gemini diffractometer (Oxford
Diffraction) [15]. The structure was solved by the
direct method and was refined by the least-squares
procedure in anisotropic approximation for non-
hydrogen atoms using SHELX-97 software [16]. The
positions of hydrogen atoms were calculated
geometrically and were included in the refinement
with temperature factors UH exceeding those of the
corresponding carbon and oxygen atoms by a factor of
1.2. The principal crystallographic data for compound
I and refinement parameters are given in Table 2, and
selected bond lengths and bond angles are given in
Table 3. The coordinates of atoms were deposited to
the Cambridge Crystallographic Data Centre (entry no.
CCDC 806259). PLATON program [13] was used to
calculate the geometric parameters and plot the
structures; only hydrogen atoms involved in hydrogen
bonds are shown in the crystal packing of I (Fig. 2).
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SYNTHESIS, STRUCTURE, AND ANTIMICROBIAL ACTIVITY OF COPPER(II) CHELATES
535
Table 4. IR spectra (ν, cm–1) of copper(II) chelates I–IXa
Comp. no.
ν(NH)
ν(C=N)
νas(COO–)
νs(COO–)
Δb
ν(Cu–N), ν(Cu–O)
3298, 3253, 3137, 3022, 2960,
2925, 2843, 2794,2694, 2634
3332, 3136, 3020, 2931, 2768,
2682, 2637, 2600, 2500, 2420
3143, 3111, 3033, 2930, 2847,
2798, 2702, 2644, 2612, 2512
3135, 3035, 2953, 2852, 2850,
2846, 2795, 2707, 2651, 2510
3320, 3147, 3030, 2951, 2844,
2765, 2700, 2612, 2507, 2430
3325, 3142, 3026, 2941, 2837,
2760, 2710, 2605, 2515, 2435
3153, 3106, 3028, 2914, 2853,
2796, 2637, 2610, 2507, 2425
3293, 3226, 3125, 3030, 2923,
2848, 2797, 2701, 2636, 2510
3339, 3257, 3209, 3131, 2939,
2840, 2785, 2707, 2625, 2508
1635,
1599
1633,
1603
1631,
1598
1637,
1595
1634,
1600
1631,
1604
1633,
1605
1624,
1607
1626,
1594
1572
1451
121
535, 468,
458, 413
538, 478,
467, 431
501, 468,
455, 414
528, 470,
449, 414
535, 480,
459, 435
525, 484,
452, 422
533, 478,
458, 414
516, 477,
459, 418
525, 470,
460, 410
I
1570
1571
1586
1575
1580
1574
1583
1575
1452
1467
1447
1440
1438
1443
1449
1454
116
104
139
135
142
131
134
121
II
III
IV
V
VI
VII
VIII
IX
a
The complexes were preliminarily dried in a drying box at 105°C until constant weight. b Δ = νa(COO–) – νs(COO–).
The electrical resistivities of solutions of I–IX in
DMF (20°C, c = 0.001 M) were measured with the aid
of an R-38 slide-wire bridge. The IR spectra of I–IX
(preliminarily dried in a drying box at 105°C until
constant weight) dispersed in mineral oil were
recorded on a Specord M-80 spectrometer. The effective
magnetic moments were determined by the Gouy
method. The molar magnetic susceptibilities were
calculated with a correction made for diamag-netism
from the theoretical magnetic susceptibilities of organic
compounds. The thermal stability of complexes I–IX
was studied on a Paulik–Paulik–Erdey derivatograph
in the temperature range from 20 to 1000°C on ex-
posure to air using Al2O3 as reference (corundum crucible).
The antimicrobial activity of complexes I–IX was
studied in vitro by the twofold serial dilution method
[17] using a liquid nutrition medium (meat infusion
broth, pH 7.0).
[2-(2-Hydroxybenzylideneamino)acetato](imida-
zole)copper(II) (I). A solution of 10 mmol of salicyl-
aldehyde, 10 mmol of aminoacetic acid (glycine), and
10 mmol of imidazole in 30 ml of ethanol was heated
to 50–55°C, 20 ml of a suspension of 10 mmol of
Fig. 2. A fragment of crystal packing of compound I.
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536
GULYA et al.
Table 5. Minimum inhibitory (MIC) and minimum bactericidal (MBC) concentrations (μg/ml) of copper(II) chelates I–IX
against some test bacterial culturesa
Gram-positive
Gram-negative
Comp. Staphylococcus aureus,
no.
ATCC 25923
Bacillus cereus
GISK 8035
Escherichia coli,
ATCC 25922
Salmonella abony
Shigela sonnei
GISK 03/03
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
MIC
MBC
300
>300
150
>300
300
150
300
75
300
>300
300
150
150
300
300
150
>300
300
300
>300
300
300
>300
150
300
>300
300
300
>300
150
>300
300
75
300
>300
300
I
II
150
300
III
IV
V
>300
>300
>300
>300
>300
>300
>300
300
>300
>300
>300
>300
>300
>300
>300
150
>300
>300
>300
>300
>300
>300
>300
>300
300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
>300
300
75
VI
VII
VIII
IX
>300
300
>300
150
>300
>300
>300
300
300
300
300
300
300
a
The MIC and MBC values for all initial compounds (imidazole, α-amino acids, and hydroxy aldehydes) exceeded 300 μg/ml.
copper(II) acetate hydrate in alcohol was added, and
the mixture was heated for 30–40 min under
continuous stirring on a magnetic stirrer. After cooling
to room temperature, slow evaporation of the mixture
was accompanied by separation of a green solid which
was filtered through a glass filter, washed with small
amounts of alcohol and diethyl ether, and dried in air
until constant weight.
Complexes II–IX were synthesized in a similar
way using as starting compounds glycine, α-alanine, or
α-phenylalanine, 5-bromo- or 5-nitrosalicylaldehyde,
2-hydroxynaphthalene-1-carbaldehyde, or 2,3-, 2,4-,
2,5-dihydroxybenzaldehyde, imidazole, and copper(II)
acetate hydrate at a molar ratio of 1:1:1:1. The yields
of I–IX and their elemental analyses and some
physicochemical characteristics are given in Table 1.
O
N
N
Cu
O
O
N
N
HN
O
nH2O
Cu
O
O
N
N
HN
O
nH2O
Cu
O
x
HN
O
nH2O
IХ
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 83 No. 3 2013

SYNTHESIS, STRUCTURE, AND ANTIMICROBIAL ACTIVITY OF COPPER(II) CHELATES
537
1998, vol. 46, no. 5, p. 859.
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