Metal complexes of N′-[2-hydroxy-5-(phenyldiazenyl)-benzylidene] isonicotinohydrazide. Synthesis, spectroscopic characterization and antimicrobial activity

Article abstract of DOI:10.2298/JSC110307062E

A new series of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II), VO(II), UO₂(II), Fe(III) and Ru(III) complexes of N′-[2-hydroxy-5-(phenyldiazenyl) benzylidene]isonicotinohydrazide (H ₂L) was synthesized and characterized by elemental analysis, ¹H-NMR, IR, UV-Vis and ESR spectroscopy, magnetic and thermogravimetric (TG) analyses, and conductivity measurements. The spectral data showed that the ligand behaved as a neutral bidentate (complexes 2, 4-6 and 14), monobasic bidentate (complexes 7 and 9), monobasic tridentate (complexes 3, 8, 10, 11 and 16) or dibasic tridentate (complexes 12, 13 and 15) and was bonded to the metal ions via the carbonyl oxygen atom in the ketonic or enolic form, the azomethine nitrogen atom and/or the deprotonated phenolic hydroxyl oxygen. The ESR spectrum of the solid vanadyl(II) complex 2 showed an axially anisotropic spectrum with eight lines in the low field region and with g _⊥ > g_∥ and A_∥ ? A _⊥ relationships, which are characteristics of a distorted octahedral structure with a d_xy ground state. However, the copper(II) complexes 4-6, and the manganese(II) complex 10 showed an isotropic type symmetry, while the copper(II) complexes 3 and 7 showed an axial symmetry type with g_∥ > g_⊥ > g_e, indicating a covalent bond character. The antibacterial and antifungal activities of the ligand and its metal complexes showed low activity compared with the standard drugs (tetracycline for the bacteria and amphotricene B for the fungi).

Full text of DOI:10.2298/JSC110307062E

J. Serb. Chem. Soc. 78 (1) 39–55 (2013)
JSCS–4394
UDC 546.562’742’732’712’472’481’492’722’
963+547.298.61+542.913:543.42:615.28+88
Original scientific paper
Metal complexes of N'-[2-hydroxy-5-(phenyldiazenyl)-
benzylidene]isonicotinohydrazide. Synthesis, spectroscopic
characterization and antimicrobial activity
1
2,3
*
ABDOU S. EL-TABL , MOHAMAD M. E. SHAKDOFA
and ADEL M. E. SHAKDOFA1
1Department of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom,
Egypt, 2Inorganic Chemistry Department, National Research Center, P. O. Box 12622,
Dokki, Cairo, Egypt and 3Department of Chemistry, Faculty of Sciences and Arts,
King Abdulaziz University, Khulais, Saudi Arabia
(Received 7 March 2011, revised 12 June 2012)
Abstract: A new series of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II),
VO(II), UO2(II), Fe(III) and Ru(III) complexes of N′-[2-hydroxy-5-(phenyl-
diazenyl)benzylidene]isonicotinohydrazide (H2L) was synthesized and charac-
1
terized by elemental analysis, H-NMR, IR, UV–Vis and ESR spectroscopy,
magnetic and thermogravimetric (TG) analyses, and conductivity measure-
ments. The spectral data showed that the ligand behaved as a neutral bidentate
(complexes 2, 4–6 and 14), monobasic bidentate (complexes 7 and 9), mono-
basic tridentate (complexes 3, 8, 10, 11 and 16) or dibasic tridentate (com-
plexes 12, 13 and 15) and was bonded to the metal ions via the carbonyl oxy-
gen atom in the ketonic or enolic form, the azomethine nitrogen atom and/or
the deprotonated phenolic hydroxyl oxygen. The ESR spectrum of the solid
vanadyl(II) complex 2 showed an axially anisotropic spectrum with eight lines
in the low field region and with g⊥ > g|| and A|| >> A⊥ relationships, which are
characteristics of a distorted octahedral structure with a dxy ground state.
However, the copper(II) complexes 4–6, and the manganese(II) complex 10
showed an isotropic type symmetry, while the copper(II) complexes 3 and 7
showed an axial symmetry type with g|| > g⊥ > ge, indicating a covalent bond
character. The antibacterial and antifungal activities of the ligand and its metal
complexes showed low activity compared with the standard drugs (tetracycline
for the bacteria and amphotricene B for the fungi).
Keywords: metal complexes; syntheses; spectral; isonicotinohydrazide; biolo-
gical activities.
*Corresponding author. E-mail: asaeltabl@yahoo.com
doi: 10.2298/JSC110307062E
39
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40
El-TABL, SHAKDOFA and SHAKDOFA
INTRODUCTION
There has been growing interest in studying hydrazones and their metal com-
1–3
7
1–4
8
5
9
plexes due to their application as antifungal,
antibacterial,
anticonvulsant,
3
6
anti-inflammatory, antimalarial, analgesic, antiplatelets, antituberculosis,
10
anticancer activities, and their use in the treatment of leprosy and mental dis-
order diseases. Hydrazones act as herbicides, insecticides, nematocides, roden-
11
ticides and plant growth regulators, plasticizers and stabilizers for polymers, and
polymerization initiators and antioxidants. In analytical chemistry, hydrazones
are used in the detection, determination and isolation of compounds containing a
carbonyl group. More recently, they have been extensively used for the detection
12
and determination of several metals. Metal complexes of 2-acetylpyridine ben-
13
zoylhydrazone were synthesized and crystallographically characterized. The
Mn(II), Fe(III), Ni(II), Co(II) and Zn(II) complexes of 2,6-diformyl-4-methyl-
phenol bis(benzoylhydrazone) were prepared and characterized by elemental and
14
spectroscopic measurements. The Co(II), Mn(II), Cu(II) complexes of 2-acetyl-
pyridine salicyloylhydrazone and 2-benzoylpyridine salicyloylhydrazone were also
15
synthesized and characterized. Moreover, zinc(II) complexes of 2-benzoylpy-
ridinephenylhydrazone, 2-benzoylpyridinepara-chlorophenylhydrazone and 2-ben-
zoylpyridinepara-nitrophenylhydrazone were prepared and characterized by ele-
16
mental, spectral and single-crystal X-ray diffraction analyses. Much work on
metal complexes of hydrazones with different functional groups has been re-
17
ported. However, little research has been devoted to metal complexes of azo-
hydrazone ligands; hence, the synthesis, characterization and antimicrobial acti-
vities of copper(II), nickel(II), cobalt(II), manganese(II), zinc(II), cadmium(II), mer-
cury(II), vanadyl(II), uranyl(II), iron(III) and ruthenium(III) complexes of N′-[2-
-hydroxy-5-(phenyldiazenyl)benzylidene]isonicotinohydrazide were undertaken
in the reported study.
EXPERIMENTAL
Materials and measurements
The starting chemicals were of analytical grade and provided by Merck. 2-Hydroxy-5-
(phenyldiazenyl)benzaldehyde was prepared by a published method.18 Elemental analyses
were determined by the Analytical Unit of the Cairo University of Egypt. Standard analytical
methods were used to determine the metal ion contents.19 All metal complexes were dried in
vacuum over anhydrous CaCl2. The IR spectra were measured as KBr discs using a JASCO
FT/IR 6100 spectrophotometer (400–4000 cm-1). The electronic spectra in dimethyl sul-
phoxide (DMSO) solutions (10-3 M) were recorded on a Perkin-Elmer 550 spectrophotometer.
The molar conductance of 10-3 M solutions of the complexes in DMSO was measured at 25
°C with a Bibby conductometer type MCl. The resistance measured in ohms and the molar
conductivities were calculated according to the equation: ΛM = VKg/MwRΩ, where: ΛM is the
molar conductivity (Ω-1 cm2 mol-1), V is the volume of the complex solution (mL), K is the
cell constant (0.92 cm-1), Mw is the molecular weight of the complex, g is the weight of the
complex (g), RΩ is the resistance (Ω). The 1H-NMR spectra were recorded in DMSO-d6-using
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
41
a JEOL EX-270 MHz FT-NMR spectrometer. The mass spectrum was recorded using a JEOL
JMS-AX-500 mass spectrometer provided with a data system. The thermal analysis (TG) was
performed under nitrogen on a Shimadzu DT-30 thermal analyzer from 23–800 °C at a
heating rate of 10 °C min-1. The magnetic moments (µB) were measured at room temperature
by the Gouy method μeff = 2.84(χm,corrT)1/2 using mercuric tetracyanatocobaltate(II) as the
magnetic susceptibility standard. Diamagnetic corrections were estimated from the Pascal
constant.20 ESR Measurements of the solid complexes at room temperature were realized
using a Varian E-109 spectrophotometer, with di(phenyl)-(2,4,6-trinitrophenyl)imino-
azanium (DPPH) as the standard material. Thin layer chromatography (TLC) was used to
confirm the purity of the compounds.
Preparation of ligand [H2L]
The ligand, N′-[2-hydroxy-5-(phenyldiazenyl)benzylidene]isonicotinohydrazide (H2L)
was prepared (Scheme 1) by adding equimolar amounts of isonicotinic hydrazide (1.37 g, 1.0
mmol, in 20 mL of absolute ethanol) to 2-hydroxy-5-(phenyldiazenyl)benzaldehyde (2.26 g,
1.0 mmol, in 20 mL of absolute ethanol). The mixture was refluxed under stirring for 1 h. The
solid product which formed was filtered off, washed with cold ethanol, followed by crystal-
lization from ethanol and finally dried under vacuum over anhydrous CaCl2.
O
N
OH
O
C
N
N
+
H2N
NH
C
H
HO
O
C
N
N
N
C
H
N
H
N
Scheme 1. Preparation of the ligand, N′-[2-hydroxy-5-(phenyldiazenyl)-
benzylidene]isonicotinohydrazide (H2L).
Preparation of the metal complexes 2–16
The metal complexes were prepared by mixing a hot ethanolic solution of the required
metal acetate: Cu(CH3COO)2·H2O, Ni(CH3COO)2·4H2O, Co(CH3COO)2·4H2O,
Mn(CH3COO)2·4H2O, Zn(CH3COO)2·2H2O, Cd(CH3COO)2·2H2O, Hg(CH3COO)2·H2O,
and UO2(CH3COO)2·H2O, metal chloride: CuCl2·2H2O, FeCl3·6H2O, RuCl3·3H2O or metal
sulphate: CuSO4·5H2O, VOSO4·H2O and Cu(NO3)2·2.5H2O with a suitable amount of a hot
ethanolic solution of the ligand to form 1:1 or 1:2, M:L (metal:ligand) complexes in the
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42
El-TABL, SHAKDOFA and SHAKDOFA
presence of 2 mL of triethylamine (TEA). The reaction mixture was then refluxed for a time
depending on the metal salt used (2–4 h). The formed precipitates were filtered off, washed
with ethanol, then with diethyl ether and dried under vacuum over anhydrous CaCl2.
In vitro antibacterial and antifungal activities
The biological activities of the newly synthesized hydrazone ligand, its metal complexes
and metal salts were performed in the Botany Department, Laboratory of Microbiology,
Faculty of Science, El-Menoufia University, Egypt. They were studied for their antibacterial
and antifungal activities by the disc diffusion method.21,22 The antimicrobial activities were
realized using the bacteria Escherichia coli and Bacillus subtilis, and the fungus Aspergillus
niger at 10 mg mL-1 concentrations in DMSO. The bacteria were subcultured in nutrient agar
medium which contained 5 g L-1 NaCl, 5 g L-1 peptone, 3 g L-1 beef extract and 20 g L-1 agar
in distilled water. The fungus was subcultured in Dox medium which contained (in distilled
water): 1 g L-1 yeast extract, 30 g L-1 sucrose, 3 mg L-1 NaNO3, 20 g L-1 agar, 0.5 g L-1 KCl,
1 g L-1 KH2PO4, 0.5 g L-1 MgSO4·7H2O (0.5 g) and a trace of FeCl3·6H2O in distilled water.
These mediums were then sterilized by autoclaving at 120 °C for 15 min. After cooling to
45 °C, the medium was poured into 90 mm diameter Petri dishes and incubated at 37 or 28 °C,
for the bacteria and the fungus, respectively. After a few hours, the Petri dishes were stored at
4 °C. The micro-organisms were spread over each dish using a sterile bent loop rod. The test
was performed by placing filter paper disks (3 mm diameter) with a known concentration of
the compounds on the surface of the agar plates inoculated with a test organism. DMSO was
used as the negative control. The standard antibacterial drug tetracycline, antifungal drug
amphotericin B and solution of metal salts were also screened under similar conditions for
comparison. The Petri dishes were incubated for 48 h at 37 or 28 °C for the bacteria and the
fungus, respectively. The zone of inhibition was carefully measured in millimetres. All
determinations were made in duplicate for each of the compounds. The average of the two
independent readings for each compound was recorded.
RESULTS AND DISSCUSSION
The ligand, N’-[2-hydroxy-5-(phenyldiazenyl)benzylidene]isonicotinohydra-
zide (H L) and its metal complexes 2–16 are stable at room temperature. They
2
are non-hygroscopic and insoluble in common organic solvents, such as ethanol,
methanol, chloroform and acetone, but completely soluble in DMF and DMSO.
The elemental analyses showed that the complexes 3–6, 8, 10, 11, 14 and 16
were formed in a 2L:1M molar ratio, while the complexes 2, 7, 9, 12, 13 and 15
1
were formed in a 1L:1M molar ratio. The H-NMR, IR and UV–Vis spectral data
were compatible with the suggested structures (Figs. 1–3). The physical, analyti-
cal and spectral data for the ligand and its metal complexes are given in the Sup-
plementary material to this paper, together with selected spectra of the ligand and
1
its complexes, i.e., the IR spectra of 1, 6 and 8 (Figs. S-1–S-3), the H-NMR
spectra of 1 and 13 (Figs. S-4 and S-5), the mass spectrum of 1 (Fig. S-6) and the
ESR spectra of 2, 3 and 6 (Figs. S-7–S-9).
Infrared spectra
–1
The spectrum of the ligand (H L) showed a strong band at 1658 cm due to
2
the carbonyl group of the hydrazide moiety, whereas the medium band at 3174
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
43
–1
23,24
cm may be assigned to the N–H group.
This observation indicates that the
25
ligand is present in the ketonic form in the solid state. The spectrum showed
two broad bands in the 3300–3550 cm and 2550–3000 cm ranges which may
be assigned to the stretching vibration of the phenolic hydroxyl groups associated
through intra- and intermolecular hydrogen bonding. The relatively strong and
medium bands located at 1605, 1468 and 1004 cm corresponded to the azome-
thine group, the azo group and ν(N–N), respectively. The band which ap-
peared at 1289 cm is due to the ν(C–OH) of the phenolic moiety.
–1
–1
23
–1
26
27
23
–1
25
Fig. 1. Structure of the vanadyl(II), copper(II) and cadmium(II)
complexes (2, 4–6 and 14, respectively).
By comparison of the spectra of the complexes with that of the free ligand,
the mode of bonding between the ligand and the metal ions could be established.
The spectra of complexes 7, 9, 12, 13, and 15 showed the disappearance of bands
that are characteristic to ν(C=O) and ν(N–H), indicating that the ligand bonded
to the metal ions in its enolate form through the enolic carbonyl oxygen atom.
This mode of bonding was supported by the appearance of new bands in the
–1
–1
1507–1546 cm and 1207–1258 cm ranges, corresponding to ν(N=C–O) and
28
ν(C–O), respectively. In the case of complexes 2–6, 8, 10, 11, 14 and 16, the
band characteristic of ν(N–H) was still present and the band of the carbonyl
group was shifted to lower frequencies by 43–52 cm indicating that, the ligand
–1
in these complexes coordinated to the metal ions in its ketonic form via the oxy-
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44
El-TABL, SHAKDOFA and SHAKDOFA
Fig. 2. Structure of the copper(II), nickel(II), manganese(II), iron(III) and mercury
complexes (3, 8, 10, 11 and 16, respectively).
Fig. 3. Structure of the copper(II), cobalt(II), ruthenium(III), zinc(II) and uranyl(II)
complexes (7, 9, 12, 13 and 15, respectively).
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
45
gen atom of the carbonyl group. In all complexes, the band characteristic of the
azomethine group was shifted to lower frequencies, appearing in the 1538–1603
–1
cm range. At the same time, the band due to ν(N–N) was shifted to a higher
frequency. The increasing in the frequency of this band ν(N–N) is a clear indica-
tion that an increase in the double bond character is compensating for the loss of
electron density via electron donation to the metal ions, which if further confir-
mation of the coordination of the ligand via the azomethine group. In complexes
3, 8, 10–13, 15 and 16, the small shifts in the band characteristic of the phenolic
oxygen atom indicate that the bonding occurred via the deprotonated phenolic
–1
–1
oxygen atom. The appearance of new bands in the 573–610 cm , 510–575 cm
–1
and 467–509 cm ranges for complexes 2–16 may be assigned to the ν(M–O),
ν(M←O) and ν(M←N), respectively. The appearance of these bands was taken
29
as confirmation that the bonding of the ligand with the metal ions occurred via
the carbonyl oxygen atom in the enolic or ketonic form, azomethine nitrogen
atom and/or the deprotonated phenolic hydroxyl oxygen atom. The IR spectrum
of the nitrate complex (5) showed bands at ν (1415), ν (1330) and ν (954),
5
1
2
indicating that the nitrate group coordinated to the metal ion. The difference
–1
between the two high bands (ν –ν ) was 85 cm indicating that the nitrate ion
5
1
30–32
bonded to the copper(II) ion in an unidentate manner.
complexes 2 and 6, new bands appeared at 1258, 1143, 1112 and 984 cm , and
at 1192, 1058 and 962 cm for the two complexes, respectively. The bands of
In the case of sulphate
–1
–1
the first complex 2 indicated that the sulphates were coordinated to the vana-
30,33
dyl(II) ion in a chelating bidentate fahion,
while the bands of complex 6 in-
dicated that the sulphates were coordinated to the copper(II) ion in a chelating
30,32
unidentate fahion.
In the acetate complexes, the acetates may be coordinated
to the metal ion in unidentate, bidentate or bridging bidentate manner. The
–
–
–1
ν (CO ) and ν (CO ) of the free acetate ion are at ca. 1560 and 1416 cm
as
2
s
2
respectively. In the unidentate acetate complexes, ν(C=O) was higher than
–
–
ν (CO ) and ν(C–O) was lower than ν (CO ). As a result, the separation
s
2
as
2
between the two ν(C–O) was much larger in the unidentate than in the free ion
but in the bidentate, the separation was lower than in the free ion while in the
30
bridging bidentate, the two ν(CO) were closer to the free ion. In the case of
complexes 7, 9 and 14 two new bands appeared in the 1546–1561 cm and
1358–1387 cm ranges, which were attributed to the symmetric and asymmetric
–1
–1
stretching vibration of the acetate group. The difference between these two bands
–1
are in the 159–194 cm range, which indicates that the acetates coordinate to the
30,34
metal ion in a unidentate manner.
The infrared spectra of the vanadyl and
–1
uranyl complexes 2 and 15 revealed a medium band at 997 and 910 cm , which
may be attributed to ν(V=O) and ν(O=U=O), respectively.
35
29
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El-TABL, SHAKDOFA and SHAKDOFA
1
H-NMR spectra
1
The H-NMR spectrum of the ligand (H L) shows the absence of the signal
2
of the amino group (NH ) characteristic of the starting material (hydrazide). The
2
spectrum shows three sets of peaks, the first one observed as singlet at 12.41 (s,
1H) and 11.65 (s, 1H) ppm which may be assigned to the hydroxyl (OH) and
23,24,36
(NH) protons, respectively.
These hydrogen resonances appear at high δ
values because of their attachment to highly electronegative atoms, oxygen and
nitrogen, respectively; hence, they are in a low electron density environment.
This assignment was confirmed by the deuterated spectra in which the intensity
of these bands was considerably decreased. The position of these peaks in the
downfield region indicates the possibility of extensive hydrogen bonding involv-
36
ing these groups. The second set appeared as a singlet at 8.60 (1H, s) ppm and
36
corresponded to the azomethine proton (H–C=N). The third group appeared as
multiplets in the 7.14–8.31 (12H, m) ppm range, which were attributed to aro-
1
matic protons. It is clear from the H-NMR spectrum of the ligand that it exists in
the keto form only with no evidence for the presence of the enol form. This result
was confirmed by the appearance of the signal of the (NH) and phenolic (OH)
only and the absence of the (OH) signal of the enolic form. The same conclusion
24,36
was reported by many authors.
1
Comparing the H-NMR spectra of the zinc(II) and uranyl(II) complexes, 13
and 15, respectively, with that of the free ligand, it could be noticed that the sig-
nals of the NH and OH groups had disappeared, indicating that the ligand bonded
to the zinc(II) and uranyl(II) ions as a dibasic ligand via the enolic carbonyl oxy-
gen and the deprotonated hydroxyl oxygen atoms. This observation was con-
firmed by the absence of the signal of the acetate proton. A significant downfield
shift of the azomethine proton signal in the complexes relative to the corres-
ponding signal of the free ligand confirmed the coordination of the azomethine
nitrogen atom.
Mass spectra
The mass spectrum of the ligand (H L) revealed a molecular ion peak at m/z
2
345, which is consistent with the formula weight (345.36) for this ligand. This
result confirmed the identity of the ligand structure.
Molar conductivity
–3
The molar conductivity of 1×10 M solution of the metal complexes in
–1
2
–1
DMSO at room temperature are in the 3.5–22.5 Ω cm mol range, except for
complex 11, indicating the non-electrolytic nature of these complexes. These re-
sults confirmed that the anion is coordinated to the metal ion. The considerably
high values of some complexes may be due to partial solvolysis by DMSO. How-
–1
2
–1
ever, complex 11 has a molar conductivity value of 80.5 Ω cm mol , indi-
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
47
37
cating the electrolytic nature of this complex. These data are in agreement with
38
–1
2
–1
the results of Greenwood et al. They suggested 50–70 Ω cm mol as the
range for a 1:1 electrolyte in DMSO.
Electronic absorption spectra
The structure of the ligand reveals that the two lone pairs of electrons of the
azo group are not the only interacting non-bonding electrons, since the hydrazone
part of the ligand also contains nitrogen and oxygen atoms, which may be extra
sources of lone pair of electrons. Thus, another n→π* transition is expected to
occur from these non-bonding orbitals to different π* molecular orbitals extend-
39
ing over such large molecules. The electronic absorption spectral bands of the
ligand and its metal complexes in DMSO in the 200–1100 nm range are reported
in the Supplementary material to this article. The data reveals that the spectrum
of the ligand comprises three sets of bands in the UV and visible regions. The
first set of shortest wavelength appeared at 270 and 320 nm and may be assigned
to the π→π* transition in the benzenoid and pyridine moieties and the intra
24,40
ligand π→π* transition.
The second set appears at 350 and 375 nm and may
24,40
be assigned to n→π* of the azomethine and carbonyl group.
The third set
located at 420 nm may correspond to π→π* transition involving the π-electrons
39,41
of the azo group.
The band located in the visible region at 455 nm can be as-
signed to π→π* transition involving the whole electronic system of the com-
pounds with a considerable charge transfer character arising mainly from the
39,41
phenolic moiety.
The spectrum of vanadyl(II) complex 2 in DMSO solution showed that there
are three bands at 700, 575 and 520 nm, which may be assigned to
2
2
2
2
2
B (d )→E(d ,d ), B (d )→ B (d
) and B (d )→ A (d ) transitions,
2 xy 1
z2
2
xy
xz zy
2
xy
1
x2–y2
indicating that the vanadyl(II) complex has a distorted octahedral structure (Fig.
1).
42–44
The spectra of copper(II) complexes 3–6 were nearly identical, showing
a broad band centered in the 630–675 nm range. The position and the broadness
of this band indicated that copper(II) ion has a tetragonally distorted octahedral
geometry (Figs. 1 and 2). This broad band may consist of three superimposed
2
2
2
2
2
2
42,45
transitions B → E , B → → A and B → B .
This could be due to
1g
g
1g
1g
1g
9
2g
the Jahn Teller effect that operates on the d electronic ground state of six-
coordinated system, elongating one trans pair of coordinate bonds and shortening
the remaining four. However, the electronic spectrum of the copper complex 7
showed a broad band with shoulders at 650 and 730 nm. This spectrum is similar
42,46
to that reported for square planar copper(II) complexes (Fig. 3).
The electro-
nic spectrum of the nickel(II) complex 8 exhibited three bands located at 850
3
3
(ν ), 660 (ν ) and 580 (ν ) nm, which may be assigned to A → T ,
1
2
3
2g
2g
3
3
3
3
A → T and A → T (p) spin-allowed transitions, respectively, which are
2g
1g
2g
1g
42,45–48
characteristic of the nickel(II) ion in an octahedral structure (Fig. 2).
The
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48
El-TABL, SHAKDOFA and SHAKDOFA
ν /ν ratio of 1.29 is lower than the usual range 1.50–1.75, indicating a distorted
2
1
48
nickel(II) complex. The electronic spectrum of the cobalt(II) complex 9 showed
two bands appearing at 650 and 505 nm. These bands may be assigned to
4
4
A (F)→ T (p) transitions, suggesting that a tetrahedral geometry around the
2
1g
42,49
cobalt(II) ion (Fig. 3).
µ , which is consistent with a tetrahedral structure. A weak band at 590 nm
may be due to spin–spin coupling. The electronic absorption spectrum of
This assignment is supported by the μ value 4.42
eff
49
B
49
manganese(II) complex 10 displayed weak absorption bands at 650, 600, 540 and
6
4
4
6
4
4
465 nm. These bands may corresponded to A → T ( G) (ν ), A → E ( G)
1g
4
1g
1
1g
g
6
4
4
6
4
(ν ), A → E ( D) (ν ) and A → → T ( p) (ν ) transitions, respectively.
These transitions are characteristic of a manganese(II) ion in an octahedral
geometry (Fig. 2). The electronic absorption spectrum of iron(III) complex 11
showed bands at 640 and 580 nm, which may be assigned to A → T (G) and
A (G)→ T (G) transitions, respectively. These bands are characteristic of an
octahedral iron(III) complex (Fig. 2). However, the electronic absorption
spectrum of ruthenium(III) complex 12 in DMSO solution displayed two bands,
at 560 and 650 nm. The first band is due to a ligand-to-metal charge-transfer
2
1g
g
3
1g
1g
4
50
6
4
1g
2g
6
4
1
1
51
2
2
(LMCT) transition and the second is assigned to a T → A transition. The
band positions are similar to those observed for other octahedral ruthenium(III)
complexes (Fig. 3). The electronic spectrum of the uranyl complex 15 exhibits
2g
2g
52
one band at 530 nm which may be assigned to ligand-to-uranium charge-transfer
53
transitions (Fig 3). The diamagnetic zinc(II), cadmium(II) and mercury(II) com-
10
plexes (13, 14 and 16) have a d system, so they do not show d–d transitions.
Magnetic moments
The magnetic moments of the complexes 2–16 at room temperature are pre-
sented in the Supplementary material to this article. The results showed that all
these complexes 2–12 are paramagnetic. The vanadyl complex 2 shows a mag-
28,32
netic value equal to 1.73 µ , which corresponds to one unpaired electron.
B
The copper(II) complexes 3–7 showed values in the 1.68–1.88 µ range, which
B
are consistent with a one-unpaired electron system in an octahedral or square
24
planar structure. The nickel(II) complex 8 showed a value of 3.01 µ , which is
B
consistent with a two-unpaired electron system of an octahedral nickel(II) com-
24
plex. The cobalt(II) complex 9 showed a value of 4.42 µ ; this value indicates
B
49
a high-spin tetrahedral cobalt(II) complex. The magnetic moment values of the
manganese(II) complex 10 and iron(III) complex 11 are 4.87 and 5.34 µ , res-
B
pectively. These values are compatible with high-spin manganese(II) and iron(III)
40
complexes, respectively. The magnetic moment value of ruthenium(III) com-
5
plex 12 is 1.65 µ , which is characteristic for a d low-spin ruthenium(III) com-
plex.
B
40
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
49
Electron spin resonance of the copper(II), nickel(II), cobalt(II), manganese(II)
and vanadyl(II) complexes
1 51
The ESR spectrum of the solid vanadyl(II) complex 2 (d , V, I = 7/2) is an
axially anisotropic eight-line spectrum with g > g and A >> A relationships,
⊥
||
||
⊥
which are characteristics of a distorted octahedral structure with a d ground
xy
54
state. The spectrum shows two types of resonance components, one set is due
to parallel features (g ) and the other set due to perpendicular features (g ), which
||
⊥
indicate axially symmetric anisotropy, characteristic of interaction between the
electron spin and vanadium nuclear spin. Ligand nitrogen superhyperfine split-
ting was not observed on vanadium line, indicating interaction occuring between
55–57
2+
the electron spin and the ligand.
torted octahedral complex.
These values are typical for VO in a dis-
58,59
2
2
The molecular orbital coefficients α and β were
also calculated for the complexes using the following equations.:
E(2.0023− g )
||
2
α =
(1)
(2)
2
8λβ
A
||
A
⊥
2
β = −1.17
+
+ g − 0.36g − 0.64g
|| ⊥ e
P
P
−4
−1
−1
where P = 128×10 cm , λ = 135 cm and E is the electronic transition energy
2
2
2
2
of B → E. The lower values for α compared to β indicate that in-plane σ
2
60
bonding is more covalent than in-plane π-bonding. The in-plane π-bonding pa-
2
rameter β observed are consistent with those observed by McGarvey and Kivel-
61
son for vanadyl complexes of acetylacetone.
The ESR spectra of the solid copper(II) complexes 4–6 at room temperature
exhibit high field signals, which are isotropic due to the tumbling motion of the
molecules. The g values of the complexes are 2.080, 2.055 and 2.104, respecti-
iso
32,62
vely.
The ESR spectra of the solid copper(II) complexes 3 and 7 at room
9
temperature are characteristic for a d configuration, having an axial symmetry
type of a d ground state, which is the most common state for copper(II)
(x2–y2)
63,64
complexes.
The g values of g = 2.235 and 2.198, g = 2.045 and 2.056 with
|| ⊥
g
iso
= 2.108 and 2.104, respectively, suggest an elongated tetragonal octahedral
geometry for 3 and square planar for 7. The trend of the g-values, i.e., g > g
confirmed the tetragonal distortion around the copper(II) ion in 3 and
the square planar geometry in 7, which correspond to elongation of the four-
fold symmetry axis z. In addition, exchange coupling interactions between the
65
||
⊥
> g
e(2.0023)
66
copper(II) ion are explained by the Hathaway Expression G = (g – 2)(g – 2). If
||
⊥
the value of G is < 4.0, a considerable exchange coupling is present in the solid
complex. If G is > 4.0, the exchange interactions are negligible, which is typical
as in the case of complexes 3 and 7 (G = 5.22 and 4.15, respectively). This con-
firmed the tetragonal octahedral and square planar structures in 3 and 7, respec-
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50
El-TABL, SHAKDOFA and SHAKDOFA
67,68
tively.
Kivelson and Neiman showed that for an ionic environment, g is ≥
||
2.3, but for a covalent environment g < 2.3. The g -values for complexes 3 and 7
are 2.235 and 2.225, respectively; consequentially, the environments are conside-
rably covalent.
||
||
67,68
The ESR spectra of the solid nickel(II) and cobalt(II) complexes 8 and 9 at
room temperature do not show any ESR signals as rapid spin lattice relaxation of
40
nickel(II) and cobalt(II) tends to broaden the lines at higher temperatures. The
ESR spectra of the solid manganese(II) complex 10 and ruthenium(III) complex
12 give isotropic signals centred at 1.997 and 2.150, respectively. The broaden-
40
ing of the spectra is due to spin relaxation. The spectrum of ruthenium(III)
complex shows an additional weak signal at 2.00, which may be due to the free
radical.
Thermal analysis of some of the complexes
The thermogravimetric (TG) analysis was realised in the temperature range
20–800 °C under nitrogen. The results (Table I) show good agreement between
the calculated and experimental weight losses. The results showed that the com-
plexes 2, 5–7 and 12 generally decomposed in several steps. The first step is the
elimination of water of hydration or solvent molecules, as in complexes 5–7 and
12, in the temperature range 30–117 °C. The second step is the loss of water of
coordination, as in complexes 2, 6, 7 and 12, in the 100–350 °C range. The obser-
ved loss of coordinated water at high temperatures may be due to hydrogen bond-
ing with the hydroxyl group. The third step is the loss of the anions (sulphate,
nitrate, chloride and acetate) in the temperature range 240–380 °C. The fourth
step is the complete decomposition of the complexes through degradation of the
ligand in temperature range 300–680 °C, leaving metal oxide as the residue.
TABLE I. The results of the thermogravimetric analysis of some of the complexes
Loss in weight
Found (Calcd.), %
3.6 (3.4)
Temp.
range, °C
Composition of the
residue
No.
Assignment
2
140–175
Loss of one molecule of
coordinated water
[VO (H2L)2(SO4)]
320–380
400–490
18.0 (18.2)
66.7 (65.6)
Loss of sulphate group
Decomposition of the complex
forming V2O5
[VO (HL)2]
V2O5
5
50–90
300–350
2.3 (2.0)
13.9 (13.8)
Dehydration process (H2O)
Loss of two nitrate groups
(2HNO3)
[Cu(H2L)2(NO3)2]
[Cu(HL)2]
Decomposition of the complex
forming CuO
360–680
72.2 (75.3)
CuO
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
51
TABLE I. Continued
Loss in weight
Found (Calcd.), %
Temp.
No.
Composition of the
residue
Dehydration process (H2O) [Cu(H2L)2(SO4)H2O]
Assignment
range, °C
6
50–117
3.8 (4.0)
2.0 (2.0)
130–260
Loss of one molecule of
coordinated water
[Cu(H2L)2(SO4)]
[Cu(HL)2]
CuO
270–350
370–650
10.8 (10.6)
57.0 (61.2)
Loss of one sulphate group
(H2SO4)
Decomposition of the complex
forming CuO
7
50–110
205–250
3.5 (3.6)
3.5 (3.6)
Dehydration process (H2O) [Cu(HL)(OAc)(H2O)]
Loss of one molecule of
coordinated water
[Cu(HL)(OAc)]
270–356
360–580
12.4 (11.3)
68.1 (58.6)
Loss of one acetate group
(HOAc)
Decomposition of the complex
forming CuO
[Cu(L)]
CuO
12
50–105
110–230
3.5 (3.4)
6.4 (6.7)
Dehydration process (H2O)
Loss of two molecule of
coordinated water
[Ru(L)Cl(H2O)2]
[Ru(L)Cl]
240–280
300–430
6.9 (6.6)
56.7 (59.2)
Loss of one chlorine (HCl)
Decomposition of the complex
forming Ru2O3
[Ru(L–H)]
Ru2O3
Antibacterial and antifungal screening
The results of screening of antimicrobial activities of the ligand and its metal
complexes are listed in Table II. The results show that all the metal complexes
exhibited inhibitory effects towards the gram-positive bacterium B. subtilis and
the gram-negative bacterium E. coli. Moreover, the complexes 4 and 13–16 exhi-
bited inhibitory effects towards the fungus A. niger. In comparison, the parent
organic ligand and the solutions of the metal salts had low activity against the
bacteria and were inactive against fungus under the experimental conditions. The
order of the activity of the compounds against B. subtilis was tetracycline > 3 > 2
= 4 > 14 = 16 > 8 > 12 > 6 = 7 = 10 = 13 = 15 > 1 = 5 = 9 > 11, Table II. The
order of the activity against E. coli was 2 > tetracycline > 4 > 14 > 15 > 11 > 7 >
6 > 1 = 8 = 13 = 16 > 12 > 3 > 5 > 9 = 10, Table II. However, the order of the
activity against the fungus A. niger was 16 > 4 > 14 > amphotericin B = 15 > 13,
Table II. The results show that the activity of complexes against the tested micro-
organisms was significantly enhanced on coordination. This enhancement in the
activity may be rationalized on the basis that their structures mainly possess an
additional C=N bond. The most interesting point of the biological measurements
is that the azohydrazone had a mild biological effect while other types of
69
hydrazones, such as N-phenylglycine 2-(1-methyl-3-oxobutylidene)hydrazide,
70
3-hydroxy-2-naphthalenecarboxylic acid, [1-(2-pyridinyl)ethylidene]hydrazide,
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52
El-TABL, SHAKDOFA and SHAKDOFA
2
4,71–73
p-aminoacetophenone isonicotinoylhydrazone and Schiff bases
are bio-
logically strongly active. In addition, their metal complexes showed higher bio-
logical activity than the azohydrazone complexes. Hence, it may be stated that
the lower activity of azohydrazone and its complexes against both bacteria and
fungi could be attributed to the presence of the azo group.
TABLE II. Biological activities of the ligand and its metal complexes against bacteria and a
fungus; inhibition zone, mm
Compound
A. niger
E. coli
B. subtitles
DMSO
Amphotericin B
Tetracycline
Ligand (1)
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0
17
–
0
0
0
20
0
0
0
0
–
0
–
35
15
42
13
32
12
17
18
15
11
11
19
14
15
25
20
15
40
15
24
28
24
15
17
17
21
15
17
11
20
17
22
17
22
0
0
0
0
0
12
18
17
40
CONCLUSIONS
The Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II), VO(II), UO (II),
2
Fe(III) and Ru(III) complexes of N′-[2-hydroxy-5-(phenyldiazenyl)benzylidene]-
1
isonicotinohydrazide (H L) were characterized by elemental analysis, H-NMR,
2
IR, UV–Vis and ESR spectroscopy, thermogravimetric analyses and magnetic
and conductivity measurements. The analyses revealed that the ligand bonded in
one of four modes, neutral bidentate, monobasic bidentate, monobasic tridentate
or dibasic tridentate with the different metal ions via the oxygen atom of the
carbonyl group in the ketonic or enolic form, the nitrogen atom of the azomethine
group or the deprotonated hydroxyl oxygen atom of the azo moiety. The anal-
ytical and spectral data showed the prepared complexes had either octahedral or
square planar geometry. Some of the metal complexes exhibited inhibitory effects
towards gram-positive (B. subtilis) and gram-negative (E. coli) bacteria and the
complexes 4, 13–16 exhibited inhibitory effects towards the fungus A. niger.
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METAL COMPLEXES OF ISONICOTINOHYDRAZIDE
53
SUPPLEMENTARY MATERIAL
Physical and spectral data of the synthesized compounds are available electronically
from http://www.shd.org.rs/JSCS/, or from the corresponding author on request.
И З В О Д
КОМЛЕКСИ МЕТАЛА СА N'-[2-ХИДРОКСИ-5-(ФЕНИЛДИАЗЕНИЛ)-БЕНЗИЛИДЕН]-
-ИЗОНИКОТИНОХИДРАЗИДОМ. СИНТЕЗА, СПЕКТРОСКОПСКА
КАРАКТЕРИЗАЦИЈА И АНТИМИКРОБНА АКТИВНОСТ
ABDOU S. EL-TABL1, MOHAMAD M. E. SHAKDOFA2,3 и ADEL M. E. SHAKDOFA1
1Department of Chemistry, Faculty of Science, El-Menoufia University, Shebin El-Kom, Egypt, 2Inorganic
Chemistry Department, National Research Center, P.O. Box 12622, Dokki, Cairo, Egypt and 3Department
of Chemistry, Faculty of Sciences and Arts, King Abdulaziz University, Khulais, Saudi Arabia
Синтетизована је нова серија Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II),
VO(II), UO2(II), Fe(III) и Ru(III) комплекса са N'-[2-хидрокси-5-(фенилдиазенил)-бен-
зилиден]-изоникотинохидразидом (H2L) као лигандом. За карaктеризацију комплекса
употребљени су елементална микроанализа, 1H-NMR, IR, UV–Vis, ESR, термограви-
метријска (TG) анализа, магнетна и кондуктометријска мерења. Спектроскопска мерења
су показала да се у случају комплекса 2, 4–6 и 14 H2L координује као неутрални биден-
татни лиганд код комплекса 7 и 9 као монобазни бидентатни лиганд, код комплекса 3, 8,
10, 11 и 16 као монобазни тридентатни лиганд и код комплекса 12, 13 и 15 као двобазни
тридентатни лиганд. Координација лиганда за јон метала се одвија преко карбонилног
кисеониковог атома у енолноj или кето форми, азометинског атома азота, или депро-
тонованог фенолног атома кисоника. ESR мерења ванадил(II) комплекса у чврстом ста-
њу (2) показују аксијално-анизотропски облик спектра са осам линија у области ниже
енергије g⊥ > g|| и A|| >> A⊥, што одговара дисторгованој октаедарској структури ком-
плекса са dxy основним стањем. Међутим, ова мерења код комплекса бакра(II) (4–6), као
и код комплекса мангана(II) (10) показују изотропски облик ESR спектра, док у случају
комплекса бакра(II) (3 и 7) ови спектри показују аксијалну симетрију са g|| > g⊥ > ge, што
указује на присуство ковалентног карактера везе. Резултати испитивања антибактериј-
ске и антифунгалне активности за H2L лиганд и испитиване комплексе одговарају актив-
ности средње јачине у поређењу са стандардним агенсима.
(Примљенo 7. марта 2011, ревидирано 12. јуна 2012)
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