Synthesis and structural and biochemical activity studies of dioxime ligand and its mononuclear Cu(II), Ni(II), and Co(II) complexes

Article abstract of DOI:10.1080/15533174.2011.591878

A new tetradentate ligand incorporating dioxime moities has been synthesized. Its copper(II), nickel(II), and cobalt(II) complexes have been prepared and characterized by spectral methods. Elemental analyses and spectroscopic data of the metal complexes a

Full text of DOI:10.1080/15533174.2011.591878

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Synthesis and Structural and Biochemical Activity
Studies of Dioxime Ligand and its Mononuclear Cu(II),
Ni(II), and Co(II) Complexes
Nevin Karabocek a , Mine Armutcu a , Serdar Karabocek a , Hasan Tanak b , Samil Isik c &
Oya Baskan a
a Department of Chemistry , Karadeniz Technical University , Trabzon, Turkey
b Department of Physics, Faculty of Arts and Sciences , Amasya University , Amasya,
Turkey
c Department of Physics, Faculty of Arts and Sciences , Ondokuz Mayıs University ,
Kurupelit, Samsun, Turkey
Published online: 02 Dec 2011.
To cite this article: Nevin Karabocek , Mine Armutcu , Serdar Karabocek , Hasan Tanak , Samil Isik & Oya Baskan (2011)
Synthesis and Structural and Biochemical Activity Studies of Dioxime Ligand and its Mononuclear Cu(II), Ni(II), and Co(II)
Complexes, Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:10, 1249-1256, DOI:
10.1080/15533174.2011.591878
To link to this article: http://dx.doi.org/10.1080/15533174.2011.591878
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 41:1249–1256, 2011
Copyright ꢀ Taylor & Francis Group, LLC
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ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2011.591878
Synthesis and Structural and Biochemical Activity Studies
of Dioxime Ligand and its Mononuclear Cu(II), Ni(II),
and Co(II) Complexes
Nevin Karabocek,1 Mine Armutcu,1 Serdar Karabocek,1 Hasan Tanak,2
Samil Isik,3 and Oya Baskan1
1Department of Chemistry, Karadeniz Technical University, Trabzon, Turkey
2Department of Physics, Faculty of Arts and Sciences, Amasya University, Amasya, Turkey
3Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit,
Samsun, Turkey
discovered by using oximes in transition metal-catalyzed al-
lylic substitution[12,13] and Michael addition,[14] as well as Cu-
A new tetradentate ligand incorporating dioxime moities has
been synthesized. Its copper(II), nickel(II), and cobalt(II) com-
plexes have been prepared and characterized by spectral meth-
ods. Elemental analyses and spectroscopic data of the metal
complexes are consistent with the formation of the mononu-
clear copper(II), nickel(II) and cobalt(II) complexes. The crys-
tal structure of the (2E, 2ꢀE)-butane-2,3-dione 2,2ꢀ-{O2,O2ꢀ-[1,2-
phenylenebis(methylene)]oxime compound (3) was determined by
single-crystal x-ray diffraction technique. The free ligand and
copper(II), nickel(II), and cobalt(II) complexes (5–7) were tested
against the morphology of series bacteria. The Cu(II), Ni(II), and
Co(II) complexes exhibit higher activity than dioxime ligand under
identical experimental conditions.
catalyzed cross-coupling reaction.[15]
This article describes the syntheses and characterization
of the new ligand (2E, 3E, 2ꢁE, 3ꢁE)-butane-2,3-dione 2,2ꢁ,
3,3ꢁ-{O2, O2ꢁ-[1,2-phenylenebis(methylene)]oxime}, (H2L),
and its new complexes with Cu(II), Ni(II), and Co(II). The
properties of the complexes were investigated by magnetic,
physical, and spectral methods. Furthermore, the crystal
structure of the (2E, 2ꢁE)-butane-2,3-dione 2,2ꢁ-{O2,O2ꢁ-
[1,2-phenylenebis(methylene)]oxime, (3) was determined
by single-crystal x-ray diffraction technique. The dioxime
ligand (H2L) and its Cu(II), Ni(II), and Co(II) complexes were
evaluated for antimicrobial activity against one gram-positive
bacterium (Staphylococcus aureus), a gram-negative bacterium
(Escherichia coli), and the fungi Aspergillus niger and Tricho-
derma. The antimicrobial activities are presented in Table 1,
showing that the dioxime ligand and Cu(II), Ni(II), and Co(II)
complexes exhibit antibacterial activity against both strains.
Keywords antimicrobial activity, dione dioxime, metal complexes
Over the years, oximes have been widely used as very ef-
ficient complexing agents in analytical chemistry for isolation,
separation, and extraction of different metal ions.[1–4] The in-
corporation of oxime functions in multidonor ligands may give
rise to strong chelating agents.[2–4] Oximes and oxime ethers
are important building blocks in organic synthesis. The addition
of organometallic or radical species to oxime ethers is a syn-
thetically valuable protocol for the construction of C–C bonds,
and various useful reactions are built through this methodol-
ogy.[5–8] Generally, oxime ethers were prepared from O-alkyl
hydroxylamines and the corresponding aldehydes.[9] The direct
preparation of oxime ethers from oximes has been commonly
limited to the reaction of oximes with alkyl halides under ba-
sic conditions.[10,11] Recently, several new methods have been
EXPERIMENTAL
1H-Nuclear magnetic resonance (NMR) and 13C-NMR spec-
tra were recorded on a Varian Gemini 200 spectrometer. CDCl3
and dimethyl sulfoxide (DMSO)-d6 were used as solvent. Chem-
ical shifts (δ) were reported in parts per million (ppm) relative to
tetramethylsilane, using the solvent signal as the internal refer-
ence. Elemental analyses (C, H, and N contents) were performed
on a Costech 4010 CHNS elemental analyzer, and metal contents
were estimated spectrophotometrically. Infrared (IR) spectra
were recorded on an ATI Unicam Matson 1000 model Fourier-
transform IR (FTIR) spectrophotometer and ultraviolet–visible
(UV-Vis) spectra on an ATI Unicam UV2 model UV/Vis
spectrophotometer. Mass spectra (electrospray ionization,
ESI) were recorded on a Micromass Quanto LC-MS/MS
spectrophotometer. Room-temperature magnetic susceptibility
Received 11 February 2011; accepted 28 February 2011.
This work was supported by Karadeniz Technical University
Research Fund, and its project code is 2005.111.02.2.
Address correspondence to Serdar Karabocek Department of
Chemistry, Karadeniz Technical University 61080, Trabzon, Turkey.
E-mail: serdar@ktu.edu.tr
1249

1250
N. KARABOCEK ET AL.
TABLE 1
Antibacterial activity of compounds (diameter of inhibition zone in mm) and antifungal activity weight (mg) (% inhibition) of
the ligand and complexes
Antibacterial activity (mg mL−1
E. coli S. aureus
0.5
)
Antifungal activity (mg mL−1
A. niger Trichoderma
0.5
)
Compound
0.5
1
1
0.5
1
1
Ciprofloxin/control
H2L
5
6
7
40
10
25
12
22
45
12
35
14
20
42
10
20
13
15
44
12
27
17
19
74
72
66
62
65 (12)
45 (44)
47 (40)
50 (29)
60 (15)
12 (85)
15 (80)
20 (75)
40 (30)
30 (60)
30 (50)
35 (55)
25 (60)
20 (65)
25 (60)
24 (61)
measurements were done on a PAR model 155 vibrating sample
For [Cu(HL)(H2O)]ClO4, (5), elemental analysis (%): calcu-
magnetometer. All chemicals were of the highest quality lated: C, 37.36; H, 4.50; N, 10.89; Cu, 12.35; found: C, 37.50;
available, obtained from local suppliers, and used as received.
H, 4.45; N, 10.90; Cu, 12.20. Yield: 0.75 g (73%). MS (ESI):
m/z = 415.8 [Cu(HL)(H2O)+1]+. Yield, a green-brown solid:
0.670 g (65%). For [Ni(HL)(H2O)2]ClO4 (6), elemental analysis
(%): calculated: C, 36.36; H, 4.73; N, 10.60; Ni, 11.17; found:
C, 36.30; H, 4.65; N, 10.67; Ni, 11.05. Yield, a pale-red solid:
0.60 g (57%). MS (ESI): m/z = 429.5 [Ni(HL)(H2O)2+1]+. For
[Co(HL(H2O)2]ClO4 (7), elemental analysis (%): calculated: C,
36.35; H, 4.72; N, 10.60; Co, 11.18; found: C, 36.30; H, 4.65;
N, 10.65; Co, 11.15. Yield, a deep-brown solid: 0.70 g (67%).
MS (ESI): m/z = 430.49 [Co(HL(H2O)2 +1]+.
(2E,2ꢀE)-Butane-2,3-dione 2,2ꢀ-{O2,O2ꢀ-[1,2-Phenylenebis
(methylene)]oxime} (3)
To a vigorously stirred solution of 2,3-butanedione
monoxime (2.1 g, 20 mmol) and 1,2-bis(brommethyl)benzen
(2.5 g, 10 mmol) in 1:1 MeOH/H2O (25 mL) was added a solu-
tion of KOH (1.12 g, 20 mmol) in MeOH (10 mL) at 0◦C over
∼30 min. After stirring for 24 h at room temperature, the reac-
tion mixture was filltered and washed with MeOH. The crude
product was recrystallized from EtOH as a white microcrys-
talline solid, melting point (m.p.) 60◦C. Yield: 3.0 g (96%). MS
(ESI): m/z = 327 [M+Na]+. Elemental analysis (%): calculated:
C, 63.14; H, 6.62; N, 9.20; found: C, 63.10; H, 6.50; N, 9.30.
General Procedure for Single-Crystal X-Ray Structure
Determination
The molecular data were collected on a STOE IPDS II (16)
MoK
(2E,3E,2ꢀE,3ꢀE)-Butane-2,3-dione 2,2ꢀ,3,3ꢀ-{O2,O2ꢀ-[1,2-
Phenylenebis(methylene)]-oxime}, (H2L)
diffractometer using the
radiation at room temperature.
α
For the title compound, data collection: X-AREA; cell refine-
ment: X-AREA; data reduction: X-RED32[16]; program used to
solve structure: SHELXS9717; program used to refine structure:
SHELXL97[18]; molecular figures: ORTEP III[18]; publication
software: WinGX[19] and PARST.[20] The structure was solved
by direct methods with SHELXS-97 and refined by full-matrix
least-squares procedures on F2, using the program SHELXL-
97 computer program belonging to the WinGX software pack-
age. The refinement was carried out by full-matrix-least squares
method on the positional and anisotropic temperature param-
eters of non-hydrogen atoms corresponding to 215 crystallo-
graphic parameters. Atoms H7A, H7B, H12A, and H12B were
located in a difference Fourier map and refined isotropically, and
the other H atoms were positioned geometrically and treated us-
ing a riding model, fixing the bond lengths at 0.93 and 0.96 Å
for CH and CH3, respectively. The displacement parameters of
the H atoms were fixed at Uiso(H) = 1.2Ueq (1.5Ueq for methyl)
of their parent atoms. The structure was refined to Rint = 0.039
with 2359 observed reflections by the condition of I > 2σ(I)
threshold. Details of the data collection conditions and the pa-
rameters of refinement process are given in Table 2.
A solution of (2E,2ꢁE)-butane-2,3-dione 2,2ꢁ-{O2,O2ꢁ-
[1,2-phenylenebis(methylene)]oxime} (3.0 g, 10 mmol) and
HONH2.HCl (9.87 g, 142 mmol) in pyridine (50 mL) was
stirred at room temperature for 24 h and the mixture was
then poured into ice-cold H2O (200 mL). The resulting pre-
cipitate was collected, washed successively with ice-cold H2O
and Et2O, and dried in vacuo over P2O5. Recrystallization from
1:1 EtOH/DMSO (30 mL) gave (H2L) as a colorless microcrys-
talline solid, m.p. 180–181◦C. Yield: 3.1 g (92%). MS (ESI):
m/z = 357 [M+Na]+. Elemental analysis (%): calculated: C,
57.47; H, 6.63; N, 16.76; found: C, 57.40; H, 6.70; N, 16.65.
Preparation of Metal Complexes
The [Cu(HL)(H2O)]ClO4 (5), [Ni(HL)(H2O)2]ClO4 (6) and
[Co(HL)(H2O)2]ClO4 (7) complexes have been synthesized by
the same method. A solution of M(ClO4)2·6H2O (2 mmol) in
Me2CO (25 mL) was added to the ligand (0.670 g, 2 mmol)
solution in Me2CO (25 mL), and the mixture was boiled under
reflux with stirring for 10 h. The products were filtered off,
washed with H2O, MeOH, and Et2O, and dried over P2O5.

MONONUCLEAR Cu(II), Ni(II), AND Co(II) COMPLEXES
1251
TABLE 2
Crystallographic data for compound (3)
disc was measured. The results obtained were compared with
those of ciprofloxin. Three replicates were taken and the average
value is given in Table 1. The free ligand, its Cu(II), Ni(II), and
Co(II) complexes, metal salts, and the control (DMSO) were
screened for antifungal activity against the fungi Aspergillus
niger and Trichoderma at 0.5 and 1 mg L−1 by the mycelial dry
weight (MDW) method.[22] The cultures of fungi were purified
by single-spore isolation technique. The glucose nitrate (GN)
medium was used for growth of fungi. The mycelial biomass
was then dried along with filter paper in an oven at 65 5◦C
to constant weight, cooled, and finally weighed. The MDW was
obtained by subtracting the weight of mycelium-free filter pa-
per from final dry weight.[23] Three replicates of each treatment
were repeated in all experiments. The MDW was corrected each
time by subtracting the dry weight obtained from the incubated
flask under similar experimental conditions. The yields of MDW
(mg) are presented in Table 1. The percentage error was found to
be 0.01. The percent decrease in MDW to the test compound
in each case was calculated and tabulated in terms of average
percentage inhibition. The results indicate that the ligand and
its metal complexes arrested the growth of fungi.
CCDC deposition no.
Color/shape
771226
Colorless/prismatic plate
C16H20N2O4
304.34
Chemical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
Unit cell parameters
a, b, c (Å)
α, β, γ (a˚)
Volume (Å3)
296
0.71073 Mo Ka
Triclinic
¯
P1
8.589(7), 10.015(6), 10.939(6)
106.77(4), 96.68(5), 109.74(5)
823.9(9)
Z
2
Calculated density (mg/m3)
1.227
µ (mm−1
)
0.09
Absorption correction
Tmin, Tmax
F(000)
Integration (X-RED32)
0.946, 0.975
324
Crystal size (mm)
0.73 × 0.57 × 0.37
Diffractometer/measurement STOE IPDS II/rotation (ω
RESULTS AND DISCUSSION
method
Index ranges
scan)
(2E,3E,2ꢁE,3ꢁE)-Butane-2,3-dione 2,2ꢁ,3,3ꢁ-{O2,O2ꢁ-[1,2-
phenylenebis(methylene)]-oxime} (H2L) was synthesized in
EtOH by reacting (2E,2ꢁE)-butane-2,3-dione 2,2ꢁ-{O2,O2ꢁ-[1,2-
phenylene bis-(methylene)]oxime} (3) with hydroxylamine hy-
drochloride (Scheme 1). The dioxime (H2L) and dione (3) were
−10 ≤ h ≤ 10, −12 ≤ k ≤ 12,
−13 ≤l≤ 13
Range for data collection (a˚) 2.0 ≤ θ ≤ 26.0
Measured reflections
Independent/observed
reflections
9093
3242/2359
1
characterized by elemental analysis, H-NMR, 13C-NMR, IR,
and mass spectral data. In addition, copper(II), nickel(II), and
cobalt(II) complexes of dioxime have been prepared and char-
acterized by elemental analyses and magnetic moment, UV-Vis,
IR, and mass spectral data. In the proposed structure of (H2L),
N4 units are available for the complexation of metal ions.
Rint
0.039
Refinement method
Full-matrix least-squares on
F2
Data/restraints/parameters
Goodness-of-fit on F2
R indices [I > 2σ (I)]
R indices (all data)
3242/0/215
1.07
R1 = 0.049, wR2 = 0.1337
NMR Spectra
R1 = 0.07, wR2 = 0.144
1
The H-NMR spectra of dione (3) (in CDCl3) and dioxime
w = 1/[σ2(Fo ) + (0.0806P)2
2
Weighting scheme
ligand (H2L) (in DMSO-d6) showed well-resolved signals as
expected (Table 3). The proton NMR spectrum of compound
3 showed the following signals: C6H4 as multiplet at δ =
7.20–7.60, = C-CH3 singlet at δ = 1.95 and 2.40, O-CH2-
singlet at δ = 5.40. The proton NMR spectrum dioxime lig-
and showed the following signals: C6H4 as multiplet at δ =
7.15–7.55, = C-CH3 singlet at δ = 1.90 and 1.98, O-CH2- sin-
glet at δ = 5.25, = N-OH singlet at δ = 11.60. In the 1H-NMR
spectra, integrated data are consistent with the formula. Eight
resonance signals were observed in the 13C-NMR spectra of
dione (3) and dioxime ligand (H2L), which was also consistent
with the formula for H2L.
2
+ 0.0448P] P = (Fo
+
2
2Fc )/3
ꢀρmax, ꢀρmin (e Å−3
)
0.18, –0.23
Antimicrobial Activity
The antibacterial activity of dioxime ligand, its Cu(II), Ni(II),
and Co(II) complexes, the metal salts, and the control (DMSO)
was tested in vitro against gram-positive bacteria (Staphylococ-
cus aureus) and gram-negative bacteria (Escherichia coli) by
a paper disc method.[21] Sterile (10-mm diameter) Whatman
number 42 paper discs were soaked in different concentrations
of ligand/complexes (0.5 and 1 mg L−1) in DMSO, dried, and
then placed on nutrient agar plates. The plates were then in-
Crystal Data for (2E,2ꢀE)-Butane-2,3-dione 2,2ꢀ-{O2,O2ꢀ-
[1,2-Phenylenebis(methylene)]oxime} (3)
The crystal structure of the (2E,2ꢁE)-butane-2,3-dione
cubated for 24 h at 37◦C and the inhibition zone around each 2,2ꢁ-{O2,O2ꢁ-[1,2-phenylenebis(methylene)]-oxime
(3),

1252
N. KARABOCEK ET AL.
SCH. 1. Preparation of ligands, (H2L).
C16H18N2O4, was determined by single-crystal x-ray diffraction about the C8–C9 and C13–C14 bonds; the N2-C8-C9-C10 and
technique. The compound (3) crystallized in the triclinic space N1-C13-C14-C15 torsion angles were 12.5(3)◦ and 6.1(3)◦,
¯
group P1 with the following unit-cell parameters: a = 8.589(7) respectively. The C—N and N—O bond lengths in the oxime
Å, b = 10.015(6) Å, c = 10.939(6) Å, α = 106.77(4)a˚, β = moities of (3) are in the normal ranges and compare well with
96.68(6)a˚, γ = 109.74(5)a˚, and V = 823.9(9) Å3, with crystal- the literature values for similar compounds.[24–26]
lographic data shown in Table 2. The molecular structure of (3),
Molecular system exhibited weak intramolecular in-
with the atom numbering scheme, is shown in Figure 1, and se- teractions, namely, C5–H5. . .O2, C11–H11A. . .O2, and
lected interatomic distances and angles are listed in Table 4. The C16–H16A. . .O1 and the details of them were shown in Table
compound (3) is not planar. The (C6/C7/O2/N2/C8/C11/C9) 4. These hydrogen bonds formed rings of graph-set motif
and (C1/C12/O1/N1/C13/C16/C14) moieties were oriented S(5).[26] The π–π contact between the phenyl rings, Cg1-Cg1i
with respect to the phenyl ring A (C1–C6) at dihedral angles of [symmetry code: (i) 1 – x, –y, –z, where Cg1 was centroid
19.66(10)◦ and 82.70(11)◦, respectively. The 2,3-butanedione of the ring (C1/C2/C3/C4/C5/C6)], might further stabilize the
monoxime fragment deviated from planarity because of a structure, with centroid–centroid distance of 4.015(3) Å. To
twist between the oxime and carbonyl C( = O)CH3 groups give an overall picture for just oxime, the Cambridge Structural
TABLE 3
1H-NMR data of dione (3) and ligand (H2L)
Compound
CH3–1
CH3–4
CH2–5
Ar-H
OH
(3)
H2L (4)
2.40 (s, 6H)
1.98 (s, 6H)
1.95 (s, 6H)
1.90 (s, 6H)
5.40 (s, 4H)
5.25 (s, 4H)
7.20–7.60 (m, 4H)
7.15–7.55 (m, 4H)
—
11.60 (s, 2H)

MONONUCLEAR Cu(II), Ni(II), AND Co(II) COMPLEXES
1253
ligand. The molecular ion peaks appeared (m/z, ESI) at 415.8
[M + 1]+, at 429.5 [M + 1]+, and at 430.49 [M + 1]+ for
the [Cu(HL)(H2O)], [Ni(HL)(H2O)2], and [Co(HL(H2O)2]+,
respectively. The mass spectra showed the formation of the
ligand and its metal complexes.
IR Spectra
Relevant IR bands were given in Table 5. In general, the
complexes exhibited very comparable IR features, suggesting
that they were of similar structure. The certain bands in the
generally complicated IR spectra were used to establish the na-
ture of the complexes. The strong band at 1640 cm−1 might
be assigned to ν(C = N) vibration.[29] In the IR spectrum of
ligand (H2L1) was observed a weak band for ν(O-H) at ∼3450
cm−1. The metal complexes show a triplet at ∼1000, ∼1100,
∼1140, and a singlet at ∼625 cm−1. The presence of these
bands shows that the perchlorate is uncoordinated in the com-
plexes.[29,30] The (O–H-O) bridge was characterized by broad
absorption for the bending vibration at ∼1700 cm−1 for the
copper(II), nickel(II), and cobalt(II) complexes.[29] In the com-
plexes, ν(C = N) and ν(O-H) were shifted to lower or higher fre-
quency, suggesting coordination of metal via nitrogen. Finally,
the peaks appearing between 445 and 575 cm−1 are attributed
to ν(M-N).[31] Bands at 520–530 cm−1 were strong evidence
for the participation of water molecule[32] in coordination. A
strong band at 1640 cm−1, which shifted by 40 cm−1 toward
lower frequency upon coordination, is assigned to ν(C = N).
The significant shifts in ν(C = N) upon complexation support
the concept of coordination of the ligand through the oxime
nitrogen (Figure 2).
FIG. 1. Ortep III diagram of the title compound (3) (color figure available
online).
Database gives the following summary of the N–O bond lengths
in a group of a multi-compound: mean = 1.400 Å, median =
1.404 Å, standard deviation = 0.028 Å. Intramolecular
hydrogen bonding is an important factor in crystalline oxime;
Berthelot and co-workers found it to be present in each of the
57 compounds that they investigated.[27] They identified three
types; the –NOH group can actually be involved in all three types
of interaction, with three other molecules. Much more common,
however, occuring in 35 of the 57 oximes, is for each –NOH
to take part in two hydrogen bonds, forming dimers within the
crystal. The N–O distances are typically 2.7–2.9 Å. Berthelot
and co-workers observed a rough relationship, with the N–O
bond tending to lengthen as the number of hydrogen bonds in
which the –NOH group is participating increases. On occasion, a
hydrogen bond may be to an acceptor other than an -NOH nitro-
gen or oxygen. This was observed by Berthelot and co-workers
in which the donor –OH interacts with the nitrogen that is linked
to the phenyl ring(which has a C-N-O angle of 120◦). This result
in the crystal containing chains of hydrogen bonded molecules.
The two -C-N-O-H dihedral angles were found to be 120.7 and
120.8◦.[28]
Magnetic Properties and Electronic Absorption Spectra
Electronic spectra of the complexes were recorded in DMSO
(ε in L mol−1 cm−1). Electronic spectra of the Cu(II) complex
show bands at 13,520 (737), 16,335 (615) and 25,650 (360)
2
cm−1 assignable to a 2Eg → T2g transition and charge transfer.
Electronic spectral data coupled with detected magnetic mo-
ment of 1.85 B.M. suggest octahedral geometry.[33] Ni(II) com-
plex displays bands at 12,555 (1075), 17,450 (680), and 25,650
3
3
(375) cm−1 assignable to 3A2g → T2g(F), 3A2g → T1g(F), and
3A2g → T1g(P), respectively. These electronic transitions along
3
with magnetic moment 2.90 B.M. suggest octahedral geometry
for Ni(II) complex.[34] The Co(II) complex shows three bands at
10,160 (986), 18,610 (545), and 25,585 (400) cm−1 assignable
4
4
4
to 4T1g(F) → T1g(P), 4T1g(F) → A2g, and 4T1g(F) → T1g(P)
transitions, respectively. These transitions and observed mag-
netic moment of 4.72 B.M. indicate a high-spin octahedral com-
plex.[35,36] The calculated values of ligand field splitting energy
(10 Dq), Racah interelectronic repulsion parameter (β), cova-
lent factor (β), ratio ν2/ν1, and ligand field stabilization energy
(LFSE), given in Table 6, support the proposed geometry for all
the complexes.
Mass Spectra
The mass spectra of all compounds were recorded in pyridine
solution. The mass spectra (ESI) exhibited the molecular ion
at m/z = 327 [M+Na]+ for dione (3) and m/z = 357 [M +
Na]+ for H2L, which indicated formation of the dione and

1254
N. KARABOCEK ET AL.
TABLE 4
Selected distances (Å) and angles (◦) for compound (3)
Bond lengths
O2–N2
O2–C7
N1–C13
N1–O1
N2–C8
O1–C12
C7–C6
C1–C12
1.391(2)
1.426(2)
1.277(2)
1.397(2)
1.279(2)
1.444(2)
1.502(3)
1.501(3)
C14–O4
C14–C15
C14–C13
C13–C16
C8–C11
C8–C9
1.212(2)
1.485(4)
1.490(3)
1.474(3)
1.493(3)
1.496(3)
1.209(3)
1.493(4)
C9–O3
C9–C10
Bond angles
N2–O2–C7
C13–N1–O1
C8–N2–O2
N1–O1–C12
O2–C7–C6
C2–C1–C12
C6–C1–C12
O1–C12–C1
O4–C14–C15
O4–C14–C13
109.17(14)
111.51(15)
110.48(15)
109.01(13)
108.44(15)
119.30(17)
121.63(15)
106.89(14)
121.6(2)
C15–C14–C13
N1–C13–C16
N1–C13–C14
C16–C13–C14
N2–C8–C11
N2–C8–C9
C11–C8–C9
O3–C9–C10
O3–C9–C8
119.51(19)
125.92(17)
115.05(17)
119.03(18)
125.86(17)
114.98(18)
119.15(18)
122.8(2)
118.1(2)
119.1(2)
118.9(2)
C10–C9–C8
Torsion angles
O1–N1–C13–C14
O4–C14–C13–N1
C15–C14–C13–C16
−179.56(13)
−173.91(17)
−174.3(2)
O2–N2–C8–C9
N2–C8–C9–O3
C11–C8–C9–C10
178.35(15)
−167.6(2)
−168.9(2)
Hydrogen bonds
D–H. . .A
C5–H5. . .O2
C11–H11A. . .O2
C16–H16A. . .O1
D–H
0.93
0.96
0.96
H. . .A
2.38
2.21
D. . .A
D–H. . .A
101
2.711(3)
2.642(4)
2.656(3)
106
107
2.22
antibacterial activity against both strains. The Cu(II), Ni(II),
and Co(II) complexes exhibit higher activity than dioxime
ligand under identical experimental conditions. Antimicrobial
inhibitions were compared with the activity of ciprofloxin as a
standard, and dioxime ligand (H2L) and its Cu(II), Ni(II), and
Co(II) complexes showed less activity than the standard. The
metal salts used for synthesis of complexes exhibit negligibly
Antimicrobial Activity
The dioxime ligand (H2L) and its Cu(II), Ni(II), and Co(II)
complexes were evaluated for antimicrobial activity against one
gram-positive bacterium (S. aureus), a gram-negative bacterium
(E. coli), and fungi A. niger and Trichoderma. The antimi-
crobial activities are presented in Table 1, showing that the
dioxime ligand and Cu(II), Ni(II), and Co(II) complexes exhibit
TABLE 5
Characteristic IR bands of the ligand and its metal complexes (in cm−1
)
Compound
υ(O−H) υ(C = O) υ(C = N) υ(C−O) δ(O-H) υ(M−N)
υ (ClO4)
O-H . . . O
3
H2L
—
3235
3258 (br)
3254 (br)
1694
—
—
—
—
1630
1640
1600
1603
1602
1233
1217
1190
1189
1188
—
1365
—
—
1350
—
—
450
445
473
—
—
[Cu(HL)(H2O)]ClO4
[Ni(HL)(H2O)2]ClO4
[Co(H2L)(H2O)2]ClO4 3255 (br)
1004, 1142, 625
1003, 1120, 1142–623
1006, 1115, 1140, 624
1690
1696
1695

MONONUCLEAR Cu(II), Ni(II), AND Co(II) COMPLEXES
1255
FIG. 2. Proposed structures for the metal complexes.
small antimicrobial activities.[37–39] Enhancement of activity with mechanistic pathways.[43] Stability constants, solubility,
of dioxime ligand after chelation can be explained on the particle size, size of metal ion, and magnetic moments may
basis of Overtones and Tweedy’s concepts.[40] Inhibition was also be responsible for the antimicrobial activity of the
found to increase with increasing concentration of Cu(II), complexes.[44, 45] Attempts to show a relationship between
Ni(II), and Co(II) complex. The results showed that the stability constants and antimicrobial activity of the complexes
Cu(II) complex exhibits higher activity against each class of proved futile. Investigation of antifungal activity of the ligand
organism. The activity is related to the nature and structure and its metal complexes revealed that all the metal chelates are
of the complexes.[41, 42] The higher activity of the Cu(II) more toxic than the ligand (Table 1). The antifungal activity
complex may be attributed to its higher stability constants. is enhanced several times on being coordinated with metal.
All the dioxime ligand (H2L) and its Cu(II), Ni(II), and Co(II) Antifungal activity of the Cu(II), Ni(II), and Co(II) complexes
complexes show more activity against gram-negative E. coli increases as the stability of the complex increases. The activities
than against gram-positive S. aureus. Antibacterial activity can of these complexes follow the order [Cu(HL)(H2O)]ClO4 >
be ordered as [Cu(HL)(H2O)]ClO4 > [Co(H2L)(H2O)2]ClO4 [Co(H2L)(H2O)2]ClO4 > [Ni(HL)(H2O)2]ClO4, which is
> [Ni(HL)(H2O)2]ClO4, similar to earlier observations.[42] exactly same as the order of stability constants of these
The Cu(II), Ni(II), and Co(II) complexes do not show strong complexes. Comparison of activities shows that the copper
concentration dependence of antimicrobial activity as compared complex is more active than the dioxime ligand against A. niger.
to the antifungal activities of the same complexes. The relation Activity of dioxime ligand against Trichoderma increases after
between chelation and toxicity is very complex, expected to be chelation; however, the extent of increase is less than that of
a function of steric, electronic, and pharmakinetic factors along A. niger.
TABLE 6
Ligand field parameter of the complexes
Ligand field splitting Racah interelectronic repulsion
Covalent
factor (β)
LFSE
Complex
energy (Dq cm−1
)
parameter (B cm−1
)
β (%) ν2/ν1 (kcal mol−1
)
[Cu(HL)(H2O)]ClO4
[Ni(HL)(H2O)2]ClO4
[Co(H2L)(H2O)2]ClO4
1352.5
940.3
1025.3
95.10
845.6
915.5
—
0.8115
0.9425
—
23.45
6.25
—
1.59
1.85
38.64
26.87
29.30

1256
N. KARABOCEK ET AL.
15. Serbest, K.; Colak, A.; Guner, S.; Karabo¨cek, S. Transition Metal Chem.
CONCLUSIONS
2001, 26, 625–629.
In the present study, we have demonstrated the preparation
of dioxime ligand providing N4 donor array moiety, and their
copper(II), nickel(II), and cobalt(II) complexes. The nickel(II)
complex (6) and the copper(II) and cobalt(II) complexes (5,
7) were paramagnetic. The metal ion was complexed with ni-
trogen atoms of ligands (H2L) in an octahedral geometry for
metal ions. All of the data obtained from spectral data sup-
ported the structural properties of ligands and its Cu(II), Ni(II),
and Co(II) metal complexes. The dioxime ligand (H2L) and
its Cu(II), Ni(II), and Co(II) complexes were evaluated for an-
timicrobial activity against one gram-positive bacterium (S. au-
reus), a gram-negative bacterium (E. coli), and fungi A. niger
and Trichoderma. The antimicrobial activities are presented in
Table 1, showing that the dioxime ligand and Cu(II), Ni(II),
and Co(II) complexes exhibit antibacterial activity against both
strains. Antimicrobial inhibitions were compared with the activ-
ity of ciprofloxin as a standard, and dioxime ligand (H2L) and its
Cu(II), Ni(II), and Co(II) complexes showed less activity than
the standard.
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