Synthesis, spectroscopic and antimicrobial studies on copper(II), Cobalt(II), Nickel(II) and Manganese(II) Complexes of N-(2-Ethylphenyl) N'-Picolinoyl Hydrazine

Article abstract of DOI:10.14233/ajchem.2013.13160

Novel ligand N-(2-ethylphenyl)N'-picolinoyl hydrazine (L) has been synthesized from pyridine-2-acetyl chloride and N-(2-ethylphenyl) hydrazine by condensation in ethanol. The ligand and its Cu(II), Co(II), Ni(II) and Mn(II) complexes have been characteriz

Full text of DOI:10.14233/ajchem.2013.13160

Asian Journal of Chemistry; Vol. 25, No. 1 (2013), 455-458
http://dx.doi.org/10.14233/ajchem.2013.13160
Synthesis, Spectroscopic and Antimicrobial Studies on Copper(II), Cobalt(II),
Nickel(II) and Manganese(II) Complexes of N-(2-Ethylphenyl) N'-Picolinoyl Hydrazine
*
NETRA PAL SINGH , ANU and JAGVIR SINGH
Department of Chemistry, Meerut College, Meerut-250 001, India
*Corresponding author: E-mail: npsmcm.in@gmail.com
(Received: 3 December 2011;
Accepted: 30 July 2012)
AJC-11899
Novel ligand N-(2-ethylphenyl)N'-picolinoyl hydrazine (L) has been synthesized from pyridine-2-acetyl chloride and N-(2-ethylphenyl)
hydrazine by condensation in ethanol. The ligand and its Cu(II), Co(II), Ni(II) and Mn(II) complexes have been characterized by
microanalysis, magnetic susceptibility, FT-IR, 1H and 13C NMR, mass spectrum and UV-visible spectroscopy techniques. It is suggested
that two ligands coordinate to the metal ion by hydrazine nitrogen atoms and pyridine nitrogen atoms to form square-planar geometry of
[Cu(L)2]Cl2 but the complexes of cobalt(II), nickel(II) and manganese(II) have octahedral geometry. Newly synthesized ligand and its
metal complexes have been screened against S. aureus (ATCC 25923), S. aureus (ATCC 3160) bacterial species and C. albicans (227) and
S. cereviscae (361) fungal species.
Key Words: Hydrazine ligand, Metal(II) complexes, Spectral and biological studies.
INTRODUCTION
EXPERIMENTAL
Coordination chemistry is the most active research area
in inorganic chemistry. Several thousands of coordination
complexes1-3 have been synthesized and investigated during
the past few decades. Ever since the importance of coordination
phenomenon in biological processes4-7 was realized, a number
of metal containing macromolecules have been synthesized
and studied to understand the mechanism of complex in
biological reactions. This has resulted in the emergence of an
important branch of inorganic chemistry viz. bioinorganic
chemistry. Similarly the importance of coordination of
substrate molecules on metal ions in catalysis was understood
and a lot of research work8-10 is being carried out on this aspect.
Keeping in view the medicinal and biological importance
of hydrazones and of pyridine and its derivatives, they thought
it is worthwhile to synthesize and characterize pyridine
hydrazides11 and their transition metal complexes. Preparation
and characterization of some 3d metal complexes with
pyridine-3-benzhydrazide and pyridine-3-(2-hydroxybenz
hydrazide) were reported12.
All the chemicals used in the present investigation were
of the analytical reagent grade (AR). Pyridine-2-acetyl chloride
(Fisher Scientific), N-(2-ethylphenyl) hydrazine (Sigma,
Germany), all metal salts and solvents (Qualigens Fine
Chemicals, India) were purchased and used as received. The
elemental analysis (C, H, N) done at the Regional Sophisticated
Instrumentation Centre, Central Drug Research Institute,
Lucknow. 1H NMR and 13C NMR spectra of the samples were
measured in DMSO-d6 at IIT Delhi, India. The IR spectra were
recorded as KBr pellets using a Perkin-Elmer 783 spectro-
photometer in the range 4000-400 cm-1. UV-visible spectra
of the complexes were recorded on a Shimadzu UV-1601
spectrophotometer.
Synthesis of ligand N-(2-ethylphenyl) N'-Picolinoyl
hydrazine: This ligand was prepared by the coupling of
pyridine-2-acetyl chloride with the N-(2-ethylphenyl)hydrazine.
In a round bottom flask (100 mL), N-(2-ethylphenyl)hydrazine
(0.01 mol, 1.15 g) in distilled hot water (10.0 mL) and pyridine-
2-acetyl chloride (0.01 mol, 1.38 mL) in ethanol (95 %, 10 mL)
were taken and this solution was brought to 5 ºC by cooling in
an ice bath, stirred for 2-3 h. Temperature should be main-
tained at 5 ºC by keeping in ice bath. The product obtained
was filtered, washed with water, the organic layers were
In this article, we synthesized hydrazine derivative ligand
and their metal complexes and were characterized by IR, NMR,
molar conductance and magnetic moments, elemental analysis,
mass spectrum and UV-visible spectroscopy.

456 Singh et al.
Asian J. Chem.
collected and then evaporate the solvent under reduced
pressure to afford the product; a yellow crystalline solid was
obtained (Scheme-I). The product was well characterized by
FT-IR, 1H NMR, 13C NMR and mass spectrometry and physico-
chemical techniques.
collected, then crude products was taken in chloroform and
washed with water and then with brine solution (3 × 20 mL)
(thrice) and then evaporate the solvent under reduced pressure
to afford the product; a dirty brownish crystalline solid was
obtained (Scheme-III).
Analytical data of ligand (L):Yield: 60 %; m.p. 240 ºC,
m.w. 241, colour: yellow; analytical data for C14H15N3O found
(calc.): C, 69.70 (68.99); H, 6.22 (5.91); N, 17.42 (16.97). IR
(KBr, νmax, cm-1): 1637 ν(C-NH), 1690 ν(C=O), 1298 ν(NH-
Yield: 28 %; m.p.: 285 ºC; m.w. 789; colour: dirty brownish;
analytical data for [Co(C28H30N6O2)Cl2] found (calcd.): C,
42.58 (42.15); H, 3. 80 (3.55); N, 10.64 (10.47); IR (KBr,
ν
max, cm-1) 3412 ν(NH), 1690 ν(C=O), 3015 ν(C-H), 2220
1
1
NH). ESI-MS, m/z data found (calcd.): 241 (240), H NMR
ν(C-N), 419 ν(M-N), 380 ν(M-Cl); H NMR (DMSO-d6) δ
ppm: 7.3 (m, 16H, HC-Ar), 3.2 (s, 4H, NH-NH). 13C NMR
(DMSO-d6) δ ppm: 117.53-121.07 (16C, CH-Ar.), 140.20 (4C,
C-N), 153.21 (4C, C=O).
(DMSO-d6) δ ppm: 7.1 (m, 8H, HC-Ar), 3.8 (s, 2H, NH-NH).
13C NMR (DMSO-d6) δ ppm: 117.53-121.07 (10C, CH-Ar.),
143.23 (1C, C-N), 153.88 (2C, C=O).
Synthesis of nickel complex [Ni(L)2Cl2]: In the round
bottom flask (100 mL), N-(2-ethylphenyl)-N'-picolinoyl
hydrazine (0.01 mmol, 3.21 g) in an aqueous ethanolic solution
(15 mL) and a solution of nickel chloride (0.001 mmol, 0.238 g)
in the methanolic solution (10 mL) were mixed dropwise with
constant stirring and the reaction mixture was refluxed on
heating mental at 60 ºC for 14 h. The resulting solution was
cooled at 4 ºC, after the completion of this reaction; the reaction
mixture was monitored by thin layer chromatography
(Scheme-III). After this, the reaction mixture was taken in
methanol and washed with water and then with brine solution
(3 × 20 mL) (thrice). The organic layers were collected and
then evaporate the solvent under reduced pressure to afford
the product; a dark greenish crystalline solid was obtained.
Yield: 32 %; m.p.: 290 ºC, m.w. 790; colour: dark greenish;
analytical data for [Ni(C28H30N6O2)Cl2] found (calcd.): C, 42.53
(41.27); H, 3.79 (3.61); N, 10.63 (10.35). IR (KBr, νmax, cm-1)
3411 ν(NH), 1690 ν(C=O), 3015 ν(C-H), 2223 ν(C-N), 415
ν(M-N), 391 ν(M-Cl). 1H NMR (DMSO-d6) δ ppm: 7.4 (m,
16H, HC-Ar), 3.2 (s, 4H, NH-NH). 13C NMR (DMSO-d6) δ
ppm: 117.53-121.07 (16C, CH-Ar.), 140.20 (4C, C-N), 150.08
(4C, C=O).
MeOH
C2H5
+
C2H5
Stirred ~2-3 h
NH
N
N
COCl
NH NH2
NH
O
Scheme-I: Synthesis of the N-(2-ethylphenyl)-N'-picolinoyl hydrazine
Synthesis of copper(II) complex [Cu(L)2]Cl2: N-(2-
ethylphenyl)-N'-picolinoyl hydrazine (0.002 mmol, 0.482 g)
was dissolved in absolute ethanol and treated with an ethanolic
solution of potassium hydroxide till pH about 8 added drop
wise to a 0.001 mmol solution of copper chloride (0.170 g)]
in methanol solution with continuous stirring and refluxed at
75 ºC for 18 h (Scheme-II). After the completion of this
reaction; the reaction mixture was monitored by thin layer
chromatography. The organic layers were collected, then crude
products was taken in chloroform and washed with water and
then with brine solution (3 × 20 mL) (thrice) and then evaporate
the solvent under reduced pressure to afford the product; a
dark bluish crystalline solid was obtained.
Yield: 38 %; m.p.: 260 ºC; m.w. 720; colour: dark bluish;
analytical data for [Cu(C28H30N6O2)]Cl2 found (calcd.): C,
C2H5
NH
C2H5
46.66 (46.15), H, 4.16 (4.11), N, 11.66 (11.47). IR (KBr, νmax
,
O
N
Cl
M
Cl
HN
N
cm-1) 3402 ν(NH), 1690 ν(C=O), 3015 ν(C-H), 2210 ν(C-N),
NH
N
MeOH/ EtOH
NH
MCl2. nH2O
NH
O
+
1
Stirred & refluxed
N
H
411 ν(M-N), H NMR (DMSO-d6) δ ppm: 7.1 (m, 16H,
HC-Ar), 3.8 (s, 4H, NH-NH). 13C NMR (DMSO-d6) δ ppm:
117.53-121.07 (16C, CH-Ar.), 143.23 (4C, C-N), 153.88 (4C,
C=O).
C2H5
O
where M = Ni(II), Co(II) and Mn(II), n = 2-6
Scheme-III: Synthesis of the metal complexes
C2H5
C2H5
NH
O
Synthesis of manganese complex [Mn(L)2Cl2]: An
ethanolic solution of N-(2-ethylphenyl)-N'-picolinoyl hydra-
zine (0.002 mmol, 0.482 g) was added drop wise to a solution
of manganese chloride (0.001 mmol, 0.197 g) in methanol
and refluxed at 70 ºC for 10 h. After the completion of this
reaction the reaction mixture was monitored by thin layer
chromatography. The organic layers were collected, then crude
products was taken in chloroform and washed with water and
then with brine solution (3 × 20 mL) (thrice) and then evaporate
the solvent under reduced pressure to afford the product; a
brownish crystalline solid was obtained (Scheme-III).
N
MeOH
HN
N
NH
N
CuCl2. 2H2O
+
NH
NH
Cu
Stirred ~18 h
N
H
. Cl2
C2H5
O
O
Scheme-II: Synthesis of Copper Complex
Synthesis of cobalt complex [Co(L)2Cl2]: An ethanolic
solution of N-(2-ethylphenyl)-N'-picolinoyl hydrazine (0.002
mmol, 0.482 g) was added dropwise to a solution of cobalt
chloride ( 0.001 mmol, 0.237 g)] in methanol solution with
continuous stirring and refluxed at 70 ºC for 12 h. After the
completion of this reaction, the reaction mixture was monitored
by thin layer chromatography. The organic layers were
Yield: 63 %; m.p.: 265 ºC, m. w. 749; colour: dirty brownish;
analytical data for [Mn(C28H30N6O2)Cl2] found (calcd.): C,

Vol. 25, No. 1 (2013)
Studies on Cu(II), Co(II), Ni(II) and Mn(II) Complexes of N-(2-Ethylphenyl) N'-Picolinoyl Hydrazine 457
44.85 (44.21); H, 4.11 (4.01); N, 11.21 (11.07). IR (KBr, νmax
,
would be due to a 4T1g → 4A2g electronic transition, indicating
an octahedral configuration around Co(II) ions. In all the
reflectance spectra of the complexes, four absorption bands
appeared at 240, 311, 325 and 348 nm due to the ligand
absorptions, which are shifted from those of the parent ligand
due to complex formation. The magnetic moment values of
Ni(II) complexes are of great help in ascertaining the geometry.
The spin only value for octahedral Ni(II) with two unpaired
electrons is 2.83 BM. However, octahedral Ni(II) complexes,
the magnetic moment value observed is between 2.8-3.3 BM
due to spin orbit coupling and higher state mixing with the
ground state 3A2g. The spectrum of the present Ni(II) complex
also shows the ligands band at 350 nm and a charge transfer
band at 460 nm. In addition to these bands a d-d band was
observed at 550 nm. The electronic transitions expected for
octahedral Ni(II) are 3A2g → 3T2g(F); 3A2g → 3T1g(F) and 3A2g
→ 3T1g(P). These transitions occur at approximately 1000, 600
cm-1) 3411 ν(NH), 1690 ν(C=O), 3015 ν(C-H), 2222 ν(C-N),
415 ν(M-N), 351 ν(M-Cl). 1H NMR (DMSO-d6) δ ppm: 7.4
(m, 16H, HC-Ar), 3.2 (s, 4H, NH-NH). 13C NMR (DMSO-d6)
δ ppm: 117.53-121.07 (16C, CH-Ar.), 140.20 (4C, C-N),
150.08 (4C, C=O).
RESULTS AND DISCUSSION
The IR spectrum of the ligand shows a broad band around
3420 cm-1 assignable to stretching of -NH groups, which is
shifted to the lower frequencies in the spectra of metal
complexes. The bands in the region 3100-2900 cm-1 can be
assigned to -CH stretching vibration of ethyl group. The band
at 1690 cm-1 is due to free C=O group. The IR spectral bands
are in agreement with the proposed structure. The ligand
coordination to the metal centre is substantiated by two bands
appearing at 425-410 cm-1 and 385-350 cm-1 for the complexes
respectively which are mainly attributed to ν(M-N) and
ν(M-Cl) respectively13. The low energy pyridine ring in plane
and out of plane vibrations observed in the spectrum of the
ligand at 625 cm-1 whereas the corresponding bands for the
complexes are shifted to lower frequencies in region 714-631
cm-1 for all complexes, which is a good indication of the
coordination of the heterocyclic nitrogen14.
The 1H NMR and 13C NMR spectra of the title compounds
have been recorded in DMSO-d6 with TMS as internal refer-
ence. The present data on comparison support the conclusions
derived from the reported similar/substituted pyridine comp-
ounds. All these compounds exhibit two peaks in the 1H NMR
spectra at δ-3.5 ppm (s) assigned to proton signals of ethylene
substituted to benzyl ring system of pyridine moiety. Further-
more, two peaks were found at δ-4.5 ppm (singlet) and δ-4.8
ppm (singlet) assigned to substituted benzyl rings of pyridine.
Aromatic proton signals appeared at 7.1-7.8 ppm as multiplet.
Similarly, 13C NMR exhibited signals at δ-52.5 due to ethylene
carbon and at δ-69.8, 70.4 and 84.3 ppm assigned to benzyl
carbons. Aromatic carbon signals were also found to appear
at δ-125.7, 130.2, 135.6 and 144.2 ppm values. The electron
spray mass spectrum of N-substituted pyridine hydrazide
ligand was examined to see the fragmentation pattern of the
ligand. Mass spectra provide a vital clue for elucidating the
structure of compounds. The spectrum shows the molecular
ion peak at m/z = 241 (C14H15N3O, calculated atomic mass
240 amu due to 13C and 15N isotopes). The different competitive
fragmentation pathways of ligand give the peaks at different
mass numbers at 241. The intensity of these peaks reflects the
stability and abundance of the ions. The presence of fragments
at m/z values 121, 23, 67 and 320 shows that the fragmentation
has taken place at NH-NH-. The mass spectrum clearly suggests
existence of ligand in the hydrazones form. The electronic
spectra of Mn(II) complex show three bands in the regions
485-491, 529-530 and 710-721 nm, which may be assigned
to 6A1g →4T1g, 6A1g →4T2g(G) and 6A1g → 4T1g (D) transitions
respectively suggesting octahedral environment around the
Mn(II) ion14,15. The magnetic moment 4.88 is an additional
evidence for an octahedral structure. The µeff value measured
for the Co(II) complex is 5.32 B.M, indicating octahedral
geometry of the Co(II) ion in the complex. The former band
3
3
and 400 nm respectively. The transition A2g → T1g(P) was
probably marked by the charge transfer band. The magnetic
data also support such a structure. The spectrum of Cu(II)
complex showed absorption band at 665 nm, which could be
2
2
attributed to the A1g(F) → B1g(P) transitions characterized
Cu(II) ion in a square-planar geometry. The square-planar
geometry of Cu(II) ion in the complex is confirmed by the
measured magnetic moments values, 1.75 B.M. The square-
planar geometry is achieved by the coordination of two mole-
cules of ligand, acting as bidentate ligand, to the copper(II)
ion.
Microbial activities: For the antibacterial and antifungal
assays, the compounds were dissolved in dimethylformamide.
Further dilutions of the compounds and standard drugs in the
test medium were prepared at the required quantities of 500
and 1000 ppm concentrations with dextrose broth. The minimum
inhibitory concentrations (MIC) were determined using the
two fold serial dilution technique. A control test was also
performed containing inoculated broth supplemented at the
same dilutions used in our experiments and found inactive in
the culture medium. All the compounds were tested for their
in vitro growth inhibitory activity against different bacteria
and the fungus. Origins of bacterial strains are S. aureus (ATCC
25923), S. aureus (ATCC 3160), as Gram-positive. Gentamycin
and Amphotericin B were used as control drugs. The data on
the antimicrobial activity of the compounds and the control
drugs as minimum inhibitory concentrations values are given
in Table-1.
The cultures were obtained from SRL broth for all the
bacterial strains after 24 h of incubation at 37 ºC. C. albicans
were maintained in dextrose broth after incubation at 25 ºC
for 24 h, testing was carried out in dextrose broth at pH 7.4
and the two fold serial dilution technique was applied. A set
of tubes containing only inoculated broth was used as controls.
For the antibacterial assay after incubation at 37 ºC for 24 h
and after incubation for 48 h at 25 ºC for the antifungal assay,
the last tube with no growth of microorganism and/or yeast
was recorded to represent the minimum inhibitory concentra-
tions expressed in ppm. Every experiment in the antibacterial
and antifungal assays was replicated twice and the data is given
in Table-2.

458 Singh et al.
Asian J. Chem.
TABLE-1
ANTIBACTERIAL ACTIVITY OF TRANSITION METAL COMPLEXES AGAINST S. aureus 25923 AND S. aureus 3160
S. aureus (ATCC 25923)
S. aureus (ATCC 3160)
Compounds
Time (h)
500 ppm Inhibition zone 1000 ppm Inhibition zone
500 ppm Inhibition zone
1000 ppm Inhibition zone
I
24
48
24
48
24
48
24
48
24
48
24
48
18.6
18.3
18.8
18.5
18.9
18.5
18.1
18.5
22.4
22.4
21.1
21.1
20.7
20.3
20.7
20.1
20.9
20.4
20.3
20.4
22.2
22.2
21.2
21.2
13.8
13.5
13.9
13.5
13.5
13.1
-
17.7
17.1
17.9
17.4
17.6
17.2
-
II
III
IV
-
-
DMSO
21.1
21.1
22.1
22.1
21.2
21.2
22.2
22.2
Gentamycin
(100 ppm)
TABLE-2
ANTIFUNGAL ACTIVITIES OF NEWLY SYNTHESIZED TRANSITION METAL
COMPLEXES AGAINST S. cereviscae 227 AND C albicans 361
C. albicans (MTT 227)
S. cereviscae (MTT 361)
Time
(h)
Compounds
500 ppm Inhibition zone 1000 ppm Inhibition zone 500 ppm Inhibition zone
1000 ppm Inhibition zone
I
24
48
24
48
24
48
24
48
24
48
4.7
4.7
4.2
4.6
4.3
4.5
4.2
4.5
15.5
15.5
7.8
7.9
6.3
6.5
6.4
6.6
6.2
6.5
-
7.4
7.6
7.6
7.7
7.4
7.5
-
II
7.7
7.8
III
7.3
7.5
IV
7.6
Amphotericin-B
In DMSO
7.8
-
-
23.4
23.4
14.2
14.2
22.2
22.2
100 ppm
4. K.P. Latha, V.P. Vaidya and Keshavayya, Synth. React. Inorg. Met. Org.
Chem., 34, 667 (2004).
Conclusion
In the present investigations, all the complexes are found
to be mononuclear obtained for Cu(II), Mn(II), Co(II) and
Ni(II), ions in presence of ligand.An octahedral geometry was
suggested for all the complexes, except the Cu(II) ones. All
the investigated compounds showed less to good activity
against S. aureus.
5. B. Tang, T.X. Yue, M. Du,Y. Wang, Z.Z. Chen and H.J. Wang, Polish J.
Chem., 76, 1527 (2002).
6. A.A.H. Al-Amiery, A. Saif, M. Rawa and A. Maysaa, J. Chem. Pharm.
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ACKNOWLEDGEMENTS
10. A.A. Jarrahpour, M. Motamedifar, K. Pakshir and M. Zarei, Molecules,
9, 815 (2004).
The authors are thankful to SAIF, CDRI, Lucknow and
ACBR, New Delhi, India, for providing the spectral, analytical
facilities and biological activity, respectively.
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