Coordination modes of a Schiff base pentadentate derivative of 4-aminoantipyrine with cobalt(II), nickel(II) and copper(II) metal ions: Synthesis, spectroscopic and antimicrobial studies

Article abstract of DOI:10.3390/molecules14010174

Transition metal complexes of Co(II), Ni(II) and Cu(II) metal ions with general stoichiometry [M(L)X]X and [M(L)SO₄], where M = Co(II), Ni(II) and Cu(II), L = 3,3′-thiodipropionic acid bis(4-amino-5-ethylimino- 2,3-dimethyl-1-phenyl-3-pyrazolin

Full text of DOI:10.3390/molecules14010174

Molecules 2009, 14, 174-190; doi:10.3390/molecules14010174
OPEN ACCESS
molecules
ISSN 1420-3049
www.mdpi.com/journal/molecules
Article
Coordination Modes of a Schiff Base Pentadentate Derivative of
4-Aminoantipyrine with Cobalt(II), Nickel(II) and Copper(II)
Metal Ions: Synthesis, Spectroscopic and Antimicrobial Studies
Sulekh Chandra 1,*, Deepali Jain 2, Amit Kumar Sharma 1 and Pratibha Sharma 3
1
Department of Chemistry, Zakir Husain College (University of Delhi), J.L. Nehru Marg, New
Delhi 110002, India
2
Department of Chemistry, D.N. College, Meerut, India. E-mail: deepali101@yahoo.com (D. J.)
3
Division of Plant Pathology, IARI, Pusa, New Delhi, India. E-mail: psharma032003@yahoo.co.in
(P. S.)
* Author to whom correspondence should be addressed; E-mail: schandra_00@yahoo.com or
sharmaamitk@yahoo.co.in.
Received: 30 September 2008; in revised form: 21 November 2008 / Accepted: 2 December 2008 /
Published: 1 January 2009
Abstract: Transition metal complexes of Co(II), Ni(II) and Cu(II) metal ions with general
stoichiometry [M(L)X]X and [M(L)SO4], where M = Co(II), Ni(II) and Cu(II), L = 3,3’-
thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-pyrazoline) and X
−
= NO3 , Cl− and OAc−, have been synthesized and structurally characterized by elemental
analyses, molar conductance measurements, magnetic susceptibility measurements and
spectral techniques like IR, UV and EPR. The nickel(II) complexes were found to have
octahedral geometry, whereas cobalt(II) and copper(II) complexes were of tetragonal
geometry. The covalency factor (β) and orbital reduction factor (k) suggest the covalent
nature of the complexes. The ligand and its complexes have been screened for their
antifungal and antibacterial activities against three fungi, i.e. Alternaria brassicae,
Aspergillus niger and Fusarium oxysporum and two bacteria, i.e. Xanthomonas compestris
and Pseudomonas aeruginosa.
Keywords: 4-Aminoantipyrine derivative; Metal complexes; Biological activities.

Molecules 2009, 14
175
Introduction
The transition metal complexes of 4-aminoantipyrine and its derivatives have been extensively
examined due to their wide applications in various fields like biological, analytical and therapeutical
[1−4]. Further, they have been investigated due to their diverse biological properties as antifungal,
antibacterial, analgesic, sedative, antipyretic and anti-inflammatory agents [5-7]. In recent years, a
number of research articles have been published on transition metal complexes derived from 4-amino-
antipyrine derivatives with aza or aza-oxo donor atoms [8−11]. We were interested in examining the
biological activities of NS-donor Schiff’s bases and their transition metal complexes, thus, in this
article, we report the antifungal and antibacterial activities of the pentadentate (NNSNN-donor)
Schiff’s base ligand 3,3’-thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-
pyrazoline) and its complexes with Co(II), Ni(II) and Cu(II) metal ions. The ligand and its complexes
were characterized by physicochemical and spectral studies.
Scheme 1. Synthesis of ligand.
H2N
CH3
N
CH3
O
N
S(CH2CH2COOH)2
+
o
CH3CN
12h, 90 C
O
O
C
S
C
HN
NH
H3C
CH3
H3C
N
N
CH3
O
O
N
N
L'
o
C
CH3CN, anhydrous K2CO3
C2H5NH2, 10h, 85
O
C
O
C
S
HN
NH
Me
Me
Me
N
Me
N
N
N
N
N
Et
Et
L

Molecules 2009, 14
176
Results and Discussion
The synthesized novel Schiff’s base ligand, 3,3’-thiodipropionic acid bis(4-amino-5-ethylimino-
2,3-dimethyl-1-phenyl-3-pyrazoline) (Scheme 1) forms stable complexes with Co(II), Ni(II) and
Cu(II) metal ions. The analytical data of the complexes, together with their physical properties are
given in Table 1. The analytical data of the complexes correspond to the general stoichiometry M(L)X2
and M(L)SO4 of the complexes, where M = Co(II), Ni(II) and Cu(II), L = ligand (C32H42N8SO2) and
−
X = NO3 , Cl− and OAc−. The value of molar conductance of complexes in DMSO indicates that the
[M(L)SO4] complexes are non-electrolytes and [M(L)X]X are 1:1 electrolytes [12]. Magnetic moments
lie in the range 5.01–5.08 B.M., 2.82–2.93 B.M. and 1.82–1.91 B.M. for Co(II), Ni(II) and Cu(II)
complexes, respectively.
Table 1. Analytical data and physical properties of complexes.
S.No. Complex
Color m.p.
Molar
Yield Elemental analyses data (%) calculated (found)
(°C) conductance,
(Ω−1cm2mol−1)
(%)
54
59
58
49
61
63
60
68
61
55
62
58
M
C
H
N
S
Cl
1
2
[Co(L)NO3]NO3
Grey
272
112
104
98
7.50
48.92
5.35
17.84
4.08
-
(7.45) (48.86) (5.30) (17.79) (4.03)
8.05 52.47 5.74 15.30 4.37
CoC32H42N10SO8
[Co(L)Cl]Cl
Green 232
Brown 238
Green 222
Green 280
9.70
(8.00) (52.41) (5.70) (15.25) (4.31) (9.64)
CoC32H42N8SO2Cl2
[Co(L)OAc]OAc
CoC36H48N8SO6
[Co(L)SO4]
3
7.56
(7.51) (55.41) (6.10) (14.33) (4.06)
7.78 50.73 5.55 14.80 8.46
(14.75) (8.40)
55.46
6.16
14.38
4.11
-
4
15
-
-
CoC32H42N10S2O6
[Ni(L)NO3]NO3
NiC32H42N10SO8
[Ni(L)Cl]Cl
(7.74) (50.66) (5.51)
7.48 48.94 5.35 17.84 4.08
(7.43) (48.84) (5.30) (17.78) (4.04)
8.02 52.48 5.74 15.31 4.37
5
88
6
Light
268
276
96
9.70
Green
(7.96) (52.41) (5.67) (15.26) (4.33) (9.66)
NiC32H42N8SO2Cl2
[Ni(L)OAc]OAc
NiC36H48N8SO6
[Ni(L)SO4]
7
Light
106
17
7.54
55.48
6.16
14.38
4.11
-
Green
(7.47) (55.42) (6.10) (14.33) (4.04)
8
Green 242
Green 190*
Green 217
7.76
50.75
5.55
14.80
8.46
-
-
(8.38)
NiC32H42N10S2O6
[Cu(L)NO3]NO3
CuC32H42N10SO8
[Cu(L)Cl]Cl
(7.71) (50.68) (5.50) (14.76)
9
116
93
8.04
(7.98)
8.62
48.64
5.32
(5.27) (17.67)
5.70 19.01
17.73
4.05
(48.58)
(3.98)
10
11
12
52.14
4.35
9.64
(4.28) (9.59)
CuC32H42N8SO2Cl2
[Cu(L)OAc]OAc
CuC36H48N8SO6
[Cu(L)SO4]
(8.55) (52.08) (5.64) (18.96)
8.10 55.14 6.13 14.29
(8.04) (55.06) (6.06) (14.23)
8.34 50.43 (5.51) 14.71
(8.28) (50.36) (5.46) (14.65)
*decomposition temperature
Parrot 204*
Green
87
4.08
-
-
(4.02)
Dark
266
15
8.41
Green
(8.36)
CuC32H42N10S2O6

Molecules 2009, 14
177
Mass spectra
Mass spectra provide a vital clue for elucidating the structure of compounds. The ESI mass
spectrum of ligand L is given in Figure 1. The spectrum shows the molecular ion peak at m/z = 602
and the isotopic peak at m/z = 603 (M++1) due to 13C and 15N isotopes. The base peak at m/z = 214 is
due to the ethylimino-2,3-dimethyl-1-phenyl-3-pyrozoline (C13H16N3)+ ion. Another intense peak at
m/z = 589 is due to a (C31H39N8SO2+2H)+ ion. The different competitive fragmentation pathways of
ligand give the peaks at different mass numbers at 28, 29, 43, 60, 77, 88, 108, 131, 174, 282, 388, 390,
467, 544 and 573. The intensity of these peaks reflects the stability and abundance of the ions [13].
Figure 1. Mass spectrum of the ligand L.
Figure 2. 1H-NMR spectrum of the ligand L.

Molecules 2009, 14
178
NMR spectra
1
NMR data of the ligand are given in Table 2. Its H-NMR spectrum (Figure 2) displays a triplet at
ca. δ 1.136-1.171 ppm (s, 6H, 2H3C-C), due to the six protons of two methyl groups attached to the
CH2 groups, two singlets at ca. δ 1.601 ppm (s, 6H, 2H3C-C) and ca. δ 1.714 ppm (s, 6H, 2H3C-N) due
to protons of methyl groups attached to the pyrazoline rings, two multiplets at ca. δ 5.7−5.9 ppm (m,
12H, 6CH2) due to the protons of six methylene groups and at ca. δ 7.1−7.9 ppm (m, 10H, aromatic)
due to the protons of two phenyl rings and a broad signal at ca. δ 9.6 ppm (s, br, 2H, 2NH),
corresponding to the two protons of two NH groups [14].
The 13C-NMR spectrum (Figure 3) displays the signals corresponding to the different non-equivalent
carbon atoms at different values of δ as follows: at ca. δ 10.07 ppm (H3C-C), 15.87 ppm (H3C-H2C)
and 18.97 ppm (H3C-N) corresponding to carbon atoms of methyl groups; at ca. δ 25.87 ppm (H2C-S),
27.55 ppm (H2C-N) and 97.13 ppm (MeH2C-N) due to methylene carbon atoms; at ca. δ 117.73,
119.92, 121.07 and 125.81 ppm due to the aromatic carbon atoms; at ca. δ 143.23 and 151.07 ppm
(H3C-C and H3C-N) due to carbon atoms of pyrazoline rings; at ca. δ 153.97 ppm (C=N) due to
carbon atoms azomethine groups and at ca. δ 165.15 ppm (C=O) due to carbon atom of carbonyl
groups [15, 16].
Figure 3. 13C-NMR spectrum of the ligand L.
IR spectra
Selected IR bands of the ligand and its complexes are listed in Table 3. The IR spectrum of the
ligand displays bands at 1647, 1621 and 1532 cm−1, which may be assigned to the ν(C=O) amide I,
ν(C=N) (azomethine linkage) stretching vibration and δNH (NH in-plane-bending) (amide III)

Molecules 2009, 14
179
vibrations. The band appearing at 768 cm-1 in the spectrum corresponds to the C-S stretching vibration.
The C-S group is less polar in comparison to a C=O group and has a considerably weaker bond, so
consequently the corresponding band appeared at a lower frequency. The bands corresponding to the
C=N stretching, NH in-plane-bending and C-S stretching vibrations show the downward shift upon
coordination which indicates that the nitrogen atoms of azomethine and NH groups and sulfur atom of
C-S group are coordinated to the metal atom. However, the band corresponding to the C=O group
(amide I) remains almost unchanged on complexation, which indicates that the carbonyl group oxygen
atom is not involved in coordination. This discussion suggests that the ligand coordinates to metal
atom in quinquedentate fashion (NNSNN) [17-21].
Table 2. The NMR data of the Schiff’s base ligand.
1H-NMR
13C-NMR
δ (ppm)
1.136-1.171
1.601
Assignment
t, 6H, 2H3C-H2C
s, 6H, 2H3C-C
s, 6H, 2H3C-N
m, 12H, 6CH2
m, 10H, Ar
δ (ppm)
10.07
Assignment
C(7), C(20)
C(11), C(24)
C(5), C(21)
C(13), C(16)
C(14), C(15)
C(10), C(23)
15.87
1.714
18.97
5.793-5.949
7.158-7.953
9.687
25.87
27.55
br, 2H, 2NH
97.13
117.73
119.92
121.07
125.81
143.23
151.07
153.97
165.15
C(2, 2’), C(27, 27’)
C(3, 3’), C(26, 26’)
C(1), C(28)
16
15
13
14
O
O
C
S
17
C
12
20
H3C
7
CH3
H
N
NH
8
18
6
19
5
CH3
21
H3C
22
9
C(4), C(25)
N
N
N
N
11
N
N
24
CH2CH3
C(6), C(19)
25
4
CH
10
H3C
2
23
26'
27'
26
27
3
3'
C(8), C(18)
2'
2
C(9), C(22)
28
1
C(12), C(17)
The coordination behavior of the ligand is also verified by the appearance of new IR bands in the
spectra of complexes in the 384-501 and 313-351 cm−1 range (Table 3). These bands may be assigned
to ν(M−N) and ν(M−S) stretching vibrations, respectively. In addition, the IR spectra of complexes
also display the bands due to anions. The nitrato complexes show the IR bands in the range 1397−1407

Molecules 2009, 14
180
−
(ν5), 1304−1313 (ν1) and 1058−1075 cm−1 (ν2) due to NO stretching vibration of the NO3 ion. The Δν
−
i.e. ν5-ν1 (93−95 cm−1) indicates the unidentate coordination of NO3 ion. The chloro complexes show
the bands in the region 307−321 cm−1 to the ν(M−Cl). The acetato complexes give the IR bands in the
region 1401−1412 cm−1 and 1207−1214 cm−1 due to νas(OAc) and νs(OAc) stretching vibrations,
respectively. The Δν i.e. 187−204 cm−1 suggests the unidentate coordination of OAc− ion. In the
sulphato complexes, the two medium intensity bands in the range 951−964 cm−1 (ν1) and 439−448
cm−1 (ν2) and a strong band 1037−1137 cm−1 (ν3) are appeared. The splitting of ν3 band in to two
bands suggests the coordination of SO4−2 ion in unidentate manner [22].
Table 3. Selected IR bands of Schiff’s base ligand and its complexes.
Compound
ν(C=N)
ν(C=O)
δ(NH)
ν(C−S)
ν(M−N)
ν(M−S)
Anion bands
amide I
amide
III
Ligand
1621s
1570s
1647vs
1648s
1646s
1645s
1748s
1651s
1640m
1648ms
1647s
1643s
1647s
1650s
1648s
1532s
1494mw
1489m
1488m
1501m
1493m
1405m
1406m
1507m
1517s
768ms
761mw
740sh
717mw
722m
_
_
_
[Co(L)NO3]NO3
[Co(L)Cl]Cl
425w
464m
403m
436m
479m
384sh
475mw
479m
422mw
501w
477m
458m
335w
339m
347sh
339mw
326m
343sh
329m
313s
1405mw, 1310m, 1058m
307sh
1601sh
1593m
1576m
1571ms
1570m
1591m
1596m
1576vs
1564w
1570vs
1568s
[Co(L)OAc]OAc
[Co(L)SO4]
1412s, 1208m
1087m, 1074m, 951m, 439mw
1407m, 1313m, 1075mw
318sh
[Ni(L)NO3]NO3
[Ni(L)Cl]Cl
652br
673br
651br
668m
[Ni(L)OAc]OAc
[Ni(L)SO4]
1406s, 1207s
1048s, 1037s, 964m, 448m
1397s, 1304s, 1064m
321sh
[Cu(L)NO3]NO3
[Cu(L)Cl]Cl
669ms
699m
342m
351m
326m
318sh
1490m
1492ms
1490s
[Cu(L)OAc]OAc
[Cu(L)SO4]
684ms
684m
1401m, 1214m
1137m, 1103m, 959m, 440mw
Abbreviations: vs = very strong, s = strong, ms = medium strong, m = medium, mw = medium weak, w =
weak, br = broad, sh = sharp
Electronic spectra
The electronic spectra of the complexes were recorded in DMSO solutions. The electronic spectral
data of the complexes are given in Table 4. All the complexes show the high energy absorption band in
the region 34,511–38,910 cm−1. This transition may be attributed to the charge transfer band.
The electronic spectra of cobalt(II) complexes display the d–d transition bands in the region 9,746–
4
10,471, 15,247–19,493 and 18,621–22,371 cm−1. These transitions may be assigned to the T1g (F) →

Molecules 2009, 14
181
4T2g (F) ν1, 4T1g (F) → 4A2g (F) ν2 and 4T1g (F) → 4T1g (P) ν3, respectively. The transitions correspond
to the tetragonal geometry of the complexes.
The absorption spectra of nickel(II) complexes display three d-d transition bands in the range
11,135 −12,108, 18,621−19,416 and 21,413−27,322 cm−1. The transitions correspond to the 3A2g (F) →
3T2g (F) ν1, 3A2g (F) → 3T1g (F) ν2 and 3A2g (F) → 3T1g (P) ν3, respectively. These transitions reveal that
the nickel complexes possess an octahedral geometry and D4h symmetry.
Electronic spectra of copper(II) complexes show the d-d transition bands in the range
12,188−15,479, 18,621−19,132 and 24,402−27,322 cm−1. These bands correspond to B1g ← A1g
2
2
2
2
2
2
(
) ν1, B1g ← B (
) ν2 and B1g ← E (
) ν3 transitions,
dx2 −y2 ← dz2
dx2 −y2 ← dxy
dx
← dxz ,dyz
2g
g
2 −y2
respectively. The spectra are typical of Cu(II) complexes with an elongated tetragonal. The spectra of
all the complexes have been vibronically assigned to D4h symmetry with a dx2 −y2 ground state. The
most active vibration in this point group appears to be b1u symmetry and its efficiency may arise from
its being the only out-of-the-xy-plane vibration. The complexes are with one electron sequence i.e.
dx2 −y2
>
d > d > d , d [23, 24].
xy
xz
yz
z2
Table 4. Magnetic moment values, electronic spectral and ligand field parameters data of complexes.
μeff
(B.M.)
Dq
(cm−1)
LFSE
(kJmol−1)
Complex
λ
max (cm−1)
B(cm−1)
β
[Co(L)NO3]NO3
[Co(L)Cl]Cl
5.02
5.08
5.06
5.01
2.84
2.87
2.93
2.82
1.82
1.91
1.86
1.85
10384, 16326,18621, 36101
9746, 19493, 22371, 37878
10471, 16702, 21188, 36363
9856, 15247, 19555, 37724
11248, 18621, 21413, 36101
11185, 18688, 27322, 38022
11135, 18621, 25510, 36900
12108, 19416, 26131, 37028
13042, 19066, 24402, 34511
15479, 18621, 27322, 38910
12188, 19132, 25382, 35610
14022, 18651, 26052, 36020
984.2
1186.9
1177.1
1069.9
1124.8
1118.5
1113.5
1210.8
−
532.03
913.10
784.74
737.92
419.33
830.33
715.07
614.86
−
0.48
0.81
0.70
0.66
0.40
0.79
0.69
0.59
−
94.07
113.44
112.50
102.27
161.26
160.36
159.64
173.59
−
[Co(L)OAc]OAc
[Co(L)SO4]
[Ni(L)NO3]NO3
[Ni(L)Cl]Cl
[Ni(L)OAc]OAc
[Ni(L)SO4]
[Cu(L)NO3]NO3
[Cu(L)Cl]Cl
−
−
−
−
[Cu(L)OAc]OAc
[Cu(L)SO4]
−
−
−
−
−
−
−
−

Molecules 2009, 14
182
The ligand field parameters like Racah inter-electronic repulsion parameter B, ligand field splitting
stabilization energy 10 Dq, covalency factor β and ligand field stabilization energy (LFSE) have been
calculated for the Co(II) and Ni(II) complexes. The values of B and Dq of Co(II) complexes were
calculated from the transition energy ratio diagram using ν3/ν1 ratio. The value of β for the complexes
under study accounts for the covalent nature of the complexes. The evaluated parameters are listed in
Table 4.
EPR spectra
The X−band EPR spectra of the Co(II) complexes were recorded at liquid nitrogen temperature in
polycrystalline form. The line shaped EPR spectra of Co(II) complexes with giso = 2.10−2.14 (Table 5)
correspond to the tetragonal symmetry around the Co(II) atoms.
As a consequence of the fast spin-relaxation time of high-spin cobalt(II) ion, the signals are
observed only at low temperature. The polycrystalline powder EPR signals for the Co(II) complexes
are broad. The spectra are consistent with an S = 3/2 spin state. No hyperfine splitting of the transitions
is detected since it is difficult to resolve this splitting in nonmagnetically diluted Co(II) complexes.
The line shapes are mostly dominated by the unresolved hyperfine interactions and by a distribution of
E/D, where E and D describe the axial and rhombic Zero field splitting (ZFS) constants, respectively.
The spread of E/D results in a spread of g-values (g-strain). The dominant broadening effect is realized
when the g-strain is converted in <B-strain> with the relation ΔB = -(hν/β)(Δg/g2), where the
parameters have their usual definitions. Thus, the largest and smallest g-values of the S = 3/2 spectrum
have field widths that differ by an order of magnitude, rationalizing why the high field features of the
spectra are so broad [25, 26].
Table 5. EPR parameters and orbital reduction parameters of Co(II) and Cu(II) complexes.
2
Complex
g⊥
g||
giso
G
−
k⊥
−
k||2
−
k
−
[Co(L)NO3]NO3
[Co(L)Cl]Cl
2.0006
2.0034
2.0018
2.0021
2.0311
2.0319
2.0216
2.0294
2.3694
2.4128
2.3917
2.2916
2.2402
2.2421
2.1839
2.2112
2.12
2.14
2.13
2.10
2.10
2.10
2.08
2.09
−
−
−
−
[Co(L)OAc]OAc
[Co(L)SO4]
−
−
−
−
−
−
−
−
[Cu(L)NO3]NO3
[Cu(L)Cl]Cl
8.26
8.10
9.41
7.71
0.42
0.49
0.30
0.43
0.69
0.67
0.53
0.59
0.74
0.71
0.61
0.69
[Cu(L)OAc]OAc
[Cu(L)SO4]

Molecules 2009, 14
183
Figure 4. EPR spectrum of the [Cu(L)Cl]Cl complex.
The X−band EPR spectra of copper(II) complexes were recorded at room temperature in
polycrystalline form. The spectra show only one broad signal at giso = 2.08 – 2.10 (Figure 4). The
spectral studies reveal that the Cu(II) ion in the present complexes is in tetragonal field and shows the
D4h symmetry. The calculated values of g|| and g⊥ for the complexes show the order as g|| > g⊥ > 2.0023
(Table 5), which is consistent with the dx2 −y2 ground state [27, 28]. The odd electron is located in the
B1g antibonding orbital.
The geometric parameter G i.e. the measurement of exchange interaction between the copper
centres in the polycrystalline compounds, is calculated by using the expression:
(g|| − 2.0023) 4k|2| .ΔExz
G =
=
(g⊥ − 2.0023)
k2⊥ΔExy
The complexes in the present study show the G values greater than 4 (Table 5), which suggest that
the interaction between metal centres is negligible [24].
For the copper(II) complexes, the EPR parameters and the d-d transition energies are used to
2
evaluate, the orbital reduction factor k by using the expression: k2 = k||2 + 2k⊥ /3, where k|| and k⊥ are
the parallel and perpendicular components of the orbital reduction factor. The low values of k (0.61-
0.74) indicate the covalent nature of the complexes (Table 5). On the basis of above discussion, the
structures of complexes are given in Figure 5.

Molecules 2009, 14
184
Figure 5. Structure of complexes (a) [M(L)X]X, (b) [M(L)SO4], where M =Co(II), Ni(II)
−
and Cu(II), L = ligand and X = NO3 , Cl− and OAc−.
O
O
C
S
M
X
C
HN
NH
Me
Me
Me
N
Me
N
X
N
N
N
N
Et
Et
(a)
O
O
C
HN
S
C
NH
Me
Me
M
Me
N
Me
N
N
N
N
N
OSO3
Et
Et
(b)
Antimicrobial activities
The data of the antifungal and antibacterial activities of ligand and complexes are given in Tables 6
and 7. The data reveal that the complexes have higher activities than the free ligand (Figure 6). This
enhancement of the activity of ligand on complexation can be explained by Overtone’s Concept and
Chelation Theory [29]. The theory states that chelation reduces the polarity of the metal atom by the
partial sharing of its positive charge with donor groups and possible π–electron delocalization over the
whole ring. This results with increasing of the lipophilic character of the complex and favor the
permeation of the complex through the lipid layer of cell membrane. The complex blocks the metal
binding sites in the enzymes of microorganisms. Consequently, the complex disturbs the metabolism
pathways in cell and as a result microorganisms die.

Molecules 2009, 14
185
Table 6. Antifungal activity data of the compounds.
Fungal inhibition (%) (conc. in μg·mL−1)
Compound
A. brassicae
A. niger
F. oxysporum
100
200
300
100
200
300
100
200
300
Ligand (L)
40
52
50
50
48
58
58
55
57
60
58
60
60
70
52
61
60
60
59
70
68
65
68
72
70
71
72
80
62
70
68
70
68
78
75
76
76
80
81
80
80
100
35
50
48
50
50
65
62
64
63
64
65
65
65
75
50
60
61
59
60
74
75
70
72
75
71
70
74
90
58
68
65
66
66
80
82
80
80
84
85
82
85
100
42
52
50
49
50
60
58
60
59
60
59
60
60
65
60
70
68
70
70
74
75
72
74
74
74
72
72
75
66
77
76
78
76
85
86
85
84
90
88
90
88
100
[Co(L)NO3]NO3
[Co(L)Cl]Cl
[Co(L)OAc]OAc
[Co(L)SO4]
[Ni(L)NO3]NO3
[Ni(L)Cl]Cl
[Ni(L)OAc]OAc
[Ni(L)SO4]
[Cu(L)NO3]NO3
[Cu(L)Cl]Cl
[Cu(L)OAc]OAc
[Cu(L)SO4]
Standard (Captan)
Table 7. Antibacterial activity data of compounds.
Bacterial inhibition zone (mm) (conc. in μg·mL−1)
Xanthomonas compestris Pseudomonas aeruginosa
Compound
250
500
1000
250
500
1000
Ligand (L)
10
14
14
14
14
16
15
15
16
16
16
17
17
12
16
16
17
16
20
21
20
20
21
22
22
22
15
21
20
19
20
25
24
24
24
26
25
26
25
8
12
18
18
17
18
22
20
20
21
22
23
21
22
14
[Co(L)NO3]NO3
[Co(L)Cl]Cl
15
14
14
15
17
16
16
16
18
18
17
18
20
20
20
19
25
25
24
25
28
27
27
26
[Co(L)OAc]OAc
[Co(L)SO4]
[Ni(L)NO3]NO3
[Ni(L)Cl]Cl
[Ni(L)OAc]OAc
[Ni(L)SO4]
[Cu(L)NO3]NO3
[Cu(L)Cl]Cl
[Cu(L)OAc]OAc
[Cu(L)SO4]

Molecules 2009, 14
186
Figure 6. Antifungal activity against Fusarium oxysporum of: (A) ligand; (B) [Ni(L)NO3]NO3;
(C) [Co(L)Cl]Cl and (D) [Cu(L)NO3]NO3.
Conclusions
The ligand 3,3’-thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-
pyrazoline, characterized on the basis of elemental analysis, IR, Mass, 1H-NMR and 13C-NMR spectral
studies, coordinates to Co(II), Ni(II) and Cu(II metal ions in a pentadentate (NNSNN) manner. The
value covalency factor (β) and orbital reduction factor (k) suggest the covalent nature of the
complexes. The screening of biological activities of ligand and its complexes against the fungi
Alternaria brassicae, Aspergillus niger and Fusarium oxysporum and the pathogenic bacteria
Xanthomonas compestris and Pseudomonas aeruginosa indicates that the complexes show the
enhanced activity in comparison to free ligand.
Experimental
General
3,3’-Thiodipropionic acid, 4-aminoantipyrine and ethylamine were obtained from Sigma-Aldrich
and were of AR grade. Metal salts (E. Merck), other different chemicals (Fluka and Thomas Baker),
sterile discs (Himedia) and solvents (S.D. Fine) were commercial products and were used as received.

Molecules 2009, 14
187
The stoichiometric analyses were carried out on a Carlo-Erba 1106 analyzer. Metal contents were
estimated on an AA-640-13 Shimadzu flame atomic absorption spectrophotometer in solution prepared
1
by decomposition of the complex in hot concentrated HNO3. The H-NMR spectrum was recorded
with a model Bruker Advance DPX-300 spectrometer operating at 300 MHz using EtOD as a solvent
and TMS as an internal standard. IR spectra were recorded as KBr pellets and CsI pellets (for chloro
complexes) in the region 4,000−200 cm−1 on a FT-IR spectrum BX-II spectrophotometer. Electron
spray ionization mass spectrum was recorded on a model Q Star XL LCMS−MS system at source
temperature 300°C and voltage with +ve mode 5,500 V and –ve mode 4,500 V. The electronic spectra
were recorded on Shimadzu UV mini-1240 spectrophotometer using DMSO as a solvent. EPR spectra
were recorded for solids on an E4-EPR spectrometer at room temperature and liquid nitrogen
temperature operating at X-band region with 100 KHz modulation frequency, 5 mw microwave power
and 1 G modulation amplitude using DPPH as standard. The molar conductance of complexes was
measured in DMSO at room temperature on an ELICO (CM 82T) conductivity bridge. The magnetic
susceptibility was measured at room temperature on a Gouy balance using CuSO4.5H2O as callibrant.
Synthesis of the Schiff’s base ligand, 3,3’-thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-
1-phenyl-3-pyrazoline)(L)
The Schiff’s base ligand was synthesized in two steps:
1. 3,3’-Thiodipropionic acid bis(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) (L’): A hot
solution of 3,3’-thiodipropionic acid (0.02 mol, 3.5642 g) in acetonitrile (15 mL) was slowly added
dropwise to a hot solution of 4-aminoantipyrine (0.04 mol, 8.13 g) in acetonitrile (30 mL). The
resulting solution was refluxed for 12 h at 90°C, then allowed to cool and solvent was removed under
reduced pressure. A light brown precipitate was obtained, which was separated out by absolute
ethanol. The product was filtered, washed with cold ethanol and dried under vacuum over P4O10. Yield
54%, m.p. 210°C. Anal. calcd. for C28H32N6SO4: C, 61.31; H, 5.84; N, 15.33; S, 5.84. Found: C,
61.26; H, 5.81; N, 15.29; S, 5.79(%).
2. 3,3’-Thiodipropionic acid bis(4-amino-5-ethylimino-2,3-dimethyl-1-phenyl-3-pyrazoline) (L): To the hot
solution of 3,3’-thiodipropionic acid bis(4-amino-2,3-dimethyl-1-phenyl-3-pyrazolin-5-one) (0.01 mol,
5.48 g) in actonitrile (30 mL), a hot solution of ethylamine (0.02 mol, 1.11 mL) in acetonitrile (10 mL)
was slowly added dropwise with constant stirring. The mixture was refluxed for 10 h at 85°C, allowed
to cool at room temperature and the solvent was removed under reduced pressure. The resulting cream
colored product was dissolved in absolute ethanol, filtered, washed with cold ethanol and dried under
vacuum over P4O10. Yield 60%, m.p. 200°C. Anal. calcd. for C32H42N8SO2: C, 63.79; H, 6.98; N,
18.61; S, 5.32. Found: C, 63.73; H, 6.94; N, 18.56; S, 5.28(%).
Synthesis of the complexes
To a hot solution of Schiff’s base ligand (1 mmol) in acetonitrile (15 mL), a hot solution of
corresponding metal salt like nitrate, chloride, acetate or sulphate (1 mmol) in acetonitrile (10 mL) was
added slowly with constant stirring. The resulting mixture was refluxed for 8−10 h at 70−80°C. On

Molecules 2009, 14
188
cooling the mixture overnight at 0°C, the colored product which separated out was filtered, washed
with acetonitrile and dried under vacuum over P4O10.
Biological activities
The Disc Diffusion Method and Food Poison Technique [30, 31] were employed for screening the
antibacterial and antifungal activities, respectively, of the ligand and its complexes. The compounds
were screened for their antifungal and antibacterial properties using three fungi – Alternaria brassicae,
Aspergillus niger and Fusarium oxysporum – and two bacteria – Xanthomonas compestris and
Pseudomonas aeruginosa.
The antibacterial activity was determine with the Disc Diffusion Method. Stock solutions were
prepared by dissolving the compounds in DMSO and serial dilutions of the compounds were prepared
in sterile distilled water to determine the Minimum Inhibition Concentration (MIC). The nutrient agar
medium was poured into Petri plates. A suspension of the tested microorganism (0.5 mL) was spread
over the solid nutrient agar plates with the help of a spreader. Fifty μL of the stock solutions was
applied on the 10 mm diameter sterile disc. After evaporating the solvent, the discs were placed on the
inoculated plates. The Petri plates were sealed with Parafilm® and first placed at low temperature for
two hours to allow the diffusion of a chemical and then incubated at a suitable optimum temperature
(29 ± 2°C) for 30-36 hours. The diameter of the inhibition zones was measured in millimeters. DMSO
was used as control and streptomycin as a standard drug.
The Food Poison Technique was used to determine the antifungal activity of the compounds. The
stock solution of the compound was directly mixed into the PDA (Potato Dextrose Agar) medium at
the tested concentration. A disc of 5 mm of test fungal culture of a specific age growing on solid
medium was then cut with a sterile cork borer and was placed at the center of the solid PDA plate with
the help of inoculums’ needle. The plates were sealed with Parafilm® and incubated at 29 ± 2°C for 7
days. DMSO was used as a control and Captan as a standard fungicide. The inhibition of the fungal
growth expressed in percentage terms was determined from the growth in the test plate relative to the
respective control plate as given below:
Inhibition (%) = (C-T) 100 / C
where C = diameter of fungal growth in the control plate and T = diameter of fungal growth in the test
plate.
Acknowledgements
The authors are highly thankful to the Principal, Zakir Husain College, University of Delhi, for
providing laboratory facilities and UGC, New Delhi for financial assistance.
References and Notes
1.
Cunha, S.; Oliveira, S.M.; Rodrigues, Jr M.T.; Bastos, R.M.; Ferrari, J.; de Oliveira, C.M.A.;
Kato, L.; Napolitano, H.B.; Vencato, I.; Lariucci, C. Structural Studies of 4-Aminoantipyrine
Derivatives. J. Mol. Struct. 2005, 752, 32-39.

Molecules 2009, 14
189
2.
Collen, S.A.J.; Everaerts, F.M.; Huf, F.A. Characterization of 60Co γ-Radiation Induced Radical
Products of Antipyrine by Means of High-Performance Liquid Chromatography, Mass
Spectrometry, Capillary Zone Electrophoresis, Micellar Electrokinetic Capillary
Chromatography and Nuclear Magnetic Resonance Spectrometry. J. Chromatogr. A 1997, 788,
95-103.
3.
4.
Wolff, M.E. Burger’s Medicinal Chemistry, 3rd Ed.; Wiley: New York, USA, 1970; Vol.1.
Gilman, A.G.; Goodman, L.S.; Gilman, A. The Pharmacological Basis of Therapeutics;
Macmillan Publishing Co: New York, USA, 1980.
5.
Rosu, T.; Pasculescu, S.; Lazar, V.; Chifiriuc, C.; Cernat, R. Copper(II) Complexes with Ligands
Derived from 4-Amino-2,3-dimethyl-1-phenyl-3-pyrazoline-5-one. Molecules 2006, 11, 904-
914.
6.
7.
Filho, V.C.; Corréa, R.; Vez, Z.; Calixto, J.B.; Nunes, R.J.; Pinheiro, T.R.; Andricopulo, A.D.;
Yunes, R.A. Further Studies on Analgesic Activity of Cyclic Imides. Farmaco 1998, 53, 55-57.
Turhan-Zitouni, G.; Sivaci, M.; Kilic, F.S.; Erol, K. Synthesis of Some Triazolyl-antipyrine
Derivatives and Investigation of Analgesic Activity. Eur. J. Med. Chem. 2001, 36, 685-689 and
references within.
8.
9.
Deepa, K.; Madhu, N.T.; Radhakrishnan, P.K. Cadmium(II) Somplexes of 1,2-Di(imino-4’-
antipyrinyl)ethane. Synth. React. Inorg. Met.-Org. Nano-Met. Chem. 2005, 35, 883-888.
Radhakrishnan, T.; Joseph, P.T.; Prabhakaran, C.P. Copper(II) Complexes of Salicylal-4-amino
antipyrine and 2-Hydroxy naphthal-4-amino antipyrine. J. Inorg. Nucl. Chem. 1976, 38, 22117-
2220.
10. Ismail, K.Z. Synthesis, Spectroscopic, Magnetic and Biological Activity Studies of Copper(II)
Complexes of an Antipyrine Schiff Base. Trans. Met. Chem. 2000, 25, 522-528.
11. Agrawal. R.K.; Prakash, B. Studies on the Effect of Various Anions and Diphenylsulphoxide on
the Stereochemistry of Lanthanide(III) Coordination Compounds of 4[N-(2’-hydroxy-1’-
naphthalidene)amino] Antipyrine semicarbazone. Trans. Met. Chem. 2005, 30, 696-705.
12. Geary, W.G. The Use of Conductivity Measurements in Organic Solvents for the
Characterisation of Coordination Compounds. Coord. Chem. Rev. 1971, 7, 81-122.
13. Hamming, M.; Foster, N. Interpretation of Mass Spectra of Organic Compounds; Academic
Press: New York, USA, 1972.
14. Silverstein, R.M.; Webster, F.X. Spectrometric Identification of Organic Compounds; Wiley: New
Delhi, India, 2007
15. Singh, G.S.; Pheko, T. Spectroscopic Characterization of the 1-Substituted 3,3’-Diphenyl-4-(2’-
1
hydroxyphenyl)azetidine-2-ones: Application of 13C NMR, H-13C COSY NMR and Mass
Spectroscopy. Spectrochim. Acta, Part A. 2008, 70, 595-600.
16. Wehrli, F.W.; Marchand, A.P.; Wehrli, S. Interpretation of Carbon-13 NMR Spectra; Wiley:
New York, USA, 1988.
17. Swamy, S.J.; Pola, S. Spectroscopic Studies on Co(II), Ni(II) Cu(II) and Zn(II) Complexes with
a N4-Macrocyclic Ligands. Spectrochim. Acta, Part A 2008, 70, 929-933.
18. Swamy, S.J.; Veerapratap, B.; Nagaraju, D.; Suresh, K.; Someshwar, P. Non-template Synthesis
of ‘N4’ Di- and Tetra-amide Macrocyclic Ligands with Variable Ring Sizes. Tetrahedron 2003,
59, 10093-10096.

Molecules 2009, 14
190
19. Goeta, A.E.; Howard, J.A.K.; Maffeo, D.; Puschmann, H.; Williams, J.A.G.; Yufit, D.S. Copper(II)
Complexes of the Isomeric Tetraazamacrocyclic Ligands 1,11- and 1,8-Bis-(2-pyridylmethyl)-1,4,8,11-
tatraazacyclotetradecane and of the 1,4,8,11-Tetraazacyclotetradecane-5-12-dione Analogue at Neutral and
Basic pH. J. Chem. Soc. Dalton Trans. 2000, 1873-1880.
20. Chandra, S.; Gupta, L.K.; Agrawal, S. Modern Spectroscopic and Biological Approach in the
Characterization of a Novel 14-Membered [N4] Macrocyclic Ligand and its Transition Metal
Complexes. Trans. Met. Chem. 2007, 32, 240-245.
21. Rai, A.; Sengupta, S.K.; Pandey, O.P. Lanthanum(III) and Praseodymium(III) Complexes with
Isatin Thiosemicarbazones. Spectrochim Acta, Part A 2005, 61, 2761-2765.
22. Nakamoto, K. Infrared and Raman Spectra of Inorganic and Coordination Compounds; Wiley
Interscience: New York, USA, 1978.
23. Lever, A.B.P. Inorganic Electronic Spectroscopy; Elsevier: Amsterdam, The Netherland, 1968.
24. Hathaway, B.J.; Billing, D.E. The Electronic Properties and Stereochemistry of Mono-nuclear
Complexes of the Copper(II) Ion. Coord. Chem. Rev. 1970, 5, 143-207.
25. Plakatouras, J.C.; Perlepes, S.P.; Mentzafos, D.; Terzis, A.; Bakas, T.; Papaefthymiou, V.
Coordination Chemistry of Corrosion Inhibitors of the Benzotriazole Type: Preparation and
Characterization of Cobalt(II) Complexes with 1-Methylbenzotriazole (Mebta) and the Crystal
Stucutures of [CoCl2(Mebta)2], Trans-[Co(NCS)2(Mebta)4], Trans-[Co(NCS)2(MeOH)2(Mebta)2] and Cis-
[Co(NO3)2(Mebta)2]. Polyhedron 1992, 11, 2657-2672.
26. Assour, J.M. Electron Spin Resonance of Tetraphenylporphine Chelates. J. Chem. Phys. 1965,
43, 2477-2489.
27. Chandra, S.; Jain, D.; Sharma, A.K. EPR, Mass, Electronic, IR Spectroscopic and Thermal
Studies of Bimetallic Copper(II) Complexes with Tetradentate Ligand, 1,4-Diformylpiperazine
bis(carbohydrazone). Spectrochim. Acta, Part A 2009, 71, 1712-1719.
28. Kivelson, D.; Neiman, R. ESR Studies on the Bonding in Copper Complexes. J. Chem. Phys.
1961, 35, 149-155.
29. Belaid, S.; Landreau, A.; Djebbar, S.; Benali-Baitich, O.; Bouet, G.; Bouchara, J.-P. Synthesis,
Characterization and Antifungal Activity of a Series of Manganese(II) and Copper(II)
Complexes with Ligands Derived from Reduced N,N’-O-Phenylenebis(salicylideneimine). J.
Inorg. Biochem. 2008, 102, 63-69.
30. Drouhet, E.; Dupont, B; Improvisi, L.; Vivani, M.A.; Tortorando, A.M. In Vitro and in Vivo
Evaluation of Antifungal Agents; Elsevier: Amsterdam, The Netherland, 1986.
31. Hanna, W.G.; Moawad, M.M. Synthesis, Characterization and Antimicrobial Activity of
Cobalt(II), Nickel(II) and Copper(II) Complexes with New Asymmetrical Schiff Base Ligands
Derived from 7-Formyanil-substituted Diamine-sulphoxine and Acetylacetone. Trans. Met.
Chem. 2001, 26, 644-651.
Sample Availability: Samples of the compounds are available from the authors (S. Chandra and A. K.
Sharma).
© 2009 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland.
This article is an open-access article distributed under the terms and conditions of the Creative
Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).