Synthesis, spectral characterization, molecular modeling, thermal study and biological evaluation of transition metal complexes of a bidentate Schiff base ligand

Article abstract of DOI:10.1016/j.saa.2013.04.114

(Figure Presented) Complexes of copper(II) and nickel(II) of general composition M(L)₂X₂, have been synthesized [where L = 3-Bromoacetophenone thiosemicarbazone and X = CH₃COO^-, Cl^- and NO^-₃ ]. All the complexes were characterized by elemental analysis, magnetic moments, IR, electronic and EPR spectral studies. The ligand behaved as bidentate and coordinated through sulfur of -C=S group and nitrogen atoms of -C=N group. The copper(II) and nickel(II) complexes were found to have magnetic moments 1.94-2.02 BM, 2.96-3.02 BM respectively which was corresponding to one and two unpaired electrons respectively. The molar conductance of the complexes in solution of DMSO lies in the range of 10-20 X Ω^-1 cm² mol^-1 indicating their non-electrolytic behavior. On the basis of EPR, electronic and infrared spectral studies, tetragonal geometry has been assigned for copper(II) complexes and an octahedral geometry for nickel(II) complexes. The values of Nephelauxetic parameter β lie in the range 0.19-0.37 which indicated the covalent character in metal ligand 'σ' bond. Synthesized ligand and its copper(II) and nickel(II) complexes have also been screened against different bacterial and fungal species which suggested that complexes are more active than the ligands in antimicrobial activities.

Full text of DOI:10.1016/j.saa.2013.04.114

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
Contents lists available at SciVerse ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectral characterization, molecular modeling, thermal study
and biological evaluation of transition metal complexes of a bidentate
Schiff base ligand
b
Sulekh Chandra a, , Savita Bargujar , Rita Nirwal a,1, Kushal Qanungo c, Saroj K. Sharma c
⇑
a Department of Chemistry, Zakir Husain Delhi College (Delhi University), JLN Marg, New Delhi 110 002, India
b Department of Chemistry, Ramjas College, University of Delhi, North, Delhi 110 007, India
c Department of Applied Science and Humanities, FET, Mody Institute of Technology and Science, Lakshmangarh 332 311, Rajasthan, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
ꢀ
ꢀ
Ligand and Cu(II) and Ni(II)
complexes were synthesized.
Characterized the ligand and
complexes by IR, Mass, NMR, UV, EPR,
TGA/DTA, etc.
ꢀ
ꢀ
Molecular modeling and thermal
analysis have been provided in
support of the structures.
A distorted octahedral geometry has
been assigned for Ni(II) and
tetragonal geometry for Cu(II)
complexes.
ꢀ
Synthesized compounds have been
screened against bacterial and fungal
species in in vitro conditions.
a r t i c l e i n f o
a b s t r a c t
Article history:
Complexes of copper(II) and nickel(II) of general composition M(L)2X2, have been synthesized [where
L = 3-Bromoacetophenone thiosemicarbazone and X = CH3COOꢁ, Clꢁ and NO3ꢁ]. All the complexes were
characterized by elemental analysis, magnetic moments, IR, electronic and EPR spectral studies. The
ligand behaved as bidentate and coordinated through sulfur of AC@S group and nitrogen atoms of AC@N
group. The copper(II) and nickel(II) complexes were found to have magnetic moments 1.94–2.02 BM,
2.96–3.02 BM respectively which was corresponding to one and two unpaired electrons respectively.
Received 14 January 2013
Received in revised form 16 April 2013
Accepted 24 April 2013
Available online 7 May 2013
Keywords:
The molar conductance of the complexes in solution of DMSO lies in the range of 10–20
X
ꢁ1 cm2 molꢁ1
Thiosemicarbazone
Copper(II) and nickel(II) complexes
In vitro screening
Antibacterial activity
Antifungal activities
indicating their non-electrolytic behavior. On the basis of EPR, electronic and infrared spectral studies,
tetragonal geometry has been assigned for copper(II) complexes and an octahedral geometry for nickel(II)
complexes. The values of Nephelauxetic parameter b lie in the range 0.19–0.37 which indicated the cova-
lent character in metal ligand ‘r’ bond. Synthesized ligand and its copper(II) and nickel(II) complexes
have also been screened against different bacterial and fungal species which suggested that complexes
are more active than the ligands in antimicrobial activities.
Ó 2013 Elsevier B.V. All rights reserved.
Introduction
The past few decades have witnessed a great deal of interest in
the chemistry of transition metal Schiff base chelates specially
thiosemicarbazones as they are found lots of applications in spec-
trophotometry [1], as corrosion inhibitors [2], pulse polarography
⇑
Corresponding author. Tel.: +91 1122911267; fax: +91 1123215906.
E-mail address: schandra_00@yahoo.com (S. Chandra).
Tel.: +91 1122911267; fax: +91 1123215906.
1
1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.saa.2013.04.114

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
165
[3], as gravimetric reagents [4], in potentiometric studies [5,6], as
Analysis
visual indicators [7]. Great work is done on the biological activities
of metal complexes of thiosemicarbazones [8–21]. Antitumoral
activity is one of the main findings for thiosemicarbazones and
their metal complexes [22]. In comparison to the 4d- or 5d-metal
analogs, complexes of first row transition elements find better
applications at the cellular level [23]. In view of above applications
it is highly desirable to synthesize and characterize 3d transition
metal complexes with thiosemicarbazone ligands. In the present
paper we report the synthesis, characterization and biological eval-
uation of Cu(II) and Ni(II) complexes with thiosemicarbazone (L)
derived from 3-Bromoacetophenone.
The C, H and N were analyzed on Carlo-Erba 1106 elemental
analyzer. Molar conductance was measured on the ELICO
(CM82T) conductivity bridge. Magnetic moments were measured
at room temperature on a Gouy balance using CuSO4ꢂ5H2O as cal-
ibrant. Electronic impact mass spectrum was recorded on JEOL, JMS
– DX-303 mass spectrometer. 1H NMR (300 MHz) spectra were re-
corded on a Bruker Advanced DPX-300 spectrometer using DMSO
as a solvent. Chemical shifts are given in ppm relative to tetra-
methylsilane. IR spectra were recorded on Perkin Elmer-137
instrument as KBr pellets. The electronic spectra were recorded
in DMSO on Shimadzu UV mini-1240 spectrophotometer. EPR
spectra of the Cu(II) complexes were recorded as polycrystalline
sample at room temperature on E4-EPR spectrometer using the
DPPH as the g-marker at SAIF, IIT (Bombay). The complexes were
modeled by MOPAC 2007 program in gas phase using level of the-
ory at department of Applied Science and Humanities, FET, Mody
Institute of Technology and Science Lakshmangarh Rajasthan.
Thermal gravimetric analysis was carried out on model DTG60
thermal gravimetric analyzer.
Experimental
Materials and methods
All the chemicals used were of A R grade and procured from Sig-
ma Aldrich, Bangalore, India. Metal salts were purchased from E.
Merck, India and were used as received.
In vitro screening of compounds for antibacterial activity
Synthesis of ligand (L)
The antibacterial activity of the ligand and its metal complexes
were tested by using paper disc diffusion method [24] against Xan-
thomonas campestries pv. Campestris and Ralstonia solanacearum.
Cultures of these bacteria were obtained from ‘Indian Agricultural
Research Institute’, New Delhi. Filter paper disc treated with DMSO
served as control and with streptomycin used as a standard antibi-
otic. All determination was made in duplicate for each of the com-
pounds. An average of two independent readings for each
compound was recorded. The zone of inhibition was calculated in
millimeters carefully.
Hot ethanolic solution of thiosemicarbazide (0.91 g, 0.01 mol)
and ethanolic solution of 3-Bromoacetophenone (1.99 mL,
0.01 mol) were mixed. This mixture was refluxed at 60–70 °C for
6 h. On cooling the reaction mixture, cream-colored crystals were
precipitated out. They were filtered, washed with cold EtOH, and
dried under vacuum over P4O10, (yield 76%, mp 183 °C). Element
chemical analysis data are shown in Table 1. The purity of the com-
pounds was checked by elemental analysis and Infra Red (IR)
Spectroscopy.
Synthesis of the complexes
In vitro screening for antifungal property of compounds
A filtered solution of the appropriate metal salt (0.005 mol) in
EtOH was mixed with an ethanolic solution (50 mL) of the 3-Bro-
moacetophenone thiosemicarbazone (0.010 mol). The resulting
mixture was stirred under reflux for 2–30 (h), 14 h for [Cu(L)(CH3-
COO)2], 10 h for [Cu(L)(Cl)2] complex, 30 h for [Cu(L)(NO3)2] com-
plex, 3 h for [Ni(L)(CH3COO)2] complex, 4 h for [Ni(L)(Cl)2]
complex, 28 h for [Ni(L)(NO3)2] complex. On cooling the reaction
mixture, colored crystals were precipitated out. These crystals
were removed by filtration, washed thoroughly with 50% EtOH
The preliminary fungitoxicity screening of the compounds at
different concentrations was performed in vitro against the test
fungi, Botrytis cinerea, Macrophomina phaseolina and Phoma glomer-
ata by the food poison technique [25]. Fungal culture of B. cinerea
were obtained from Indian Type Culture Collection, Indian Agricul-
tural Research Institute, New Delhi (ITCC No. 6192) and P. glomer-
ata was isolated from seeds of Impatiens glandulifera received from
UK in the Plant Quarantine Division of National Bureau of Plant
Genetic Resources, New Delhi for by incubation on blotter. The
mycelial growth of fungi (mm) in each Petri plate was measured
and dried under vacuum over P4O10
.
Table 1
Analytical data for the ligand and its Cu(II) and Ni(II) complexes.
Compounds
Empirical formulae
Color
M.p.
(°C)
183
Yield
(%)
Metal
–
Elemental analysis data (%) found (calculated)
leff (BM)
C
H
N
Ligand (L)
C9H10N3SBr
Cream
76
39.38
3.52
15.39
(39.85)
36.05
(36.49)
32.05
(32.15)
29.50
(29.61)
36.62
(36.73)
32.01
(32.06)
29.73
(3.69)
3.26
(3.59)
2.87
(2.98)
2.62
(2.74)
3.51
(3.62)
2.91
(2.97)
2.64
(15.50)
11.28
(11.61)
12.38
(12.50)
15.21
(15.35)
11.55
(11.69)
12.35
(12.47)
15.32
[Cu(L)2(CH3COO)2]
[Cu(L)2Cl2]
CuC18H20N6S3O4
CuC18H20N6Br2S2Cl2
CuC18H20N8O6Br2S2
NiC22H26N6S2Br2
NiC18H20N6O2Br2S2Cl2
NiC18H20N8O6Br2S2
Dark
Green
Dark
Green
Green
>260
>260
>260
>260
>260
>260
56
57
57
62
58
53
8.37
(8.78)
8.58
(8.77)
8.59
(8.70)
8.09
(8.17)
8.64
(8.71)
8.02
2.02
1.96
1.94
2.96
2.98
3.02
[Cu(L)2(NO3)2]
[ Ni(L)2(CH3COO)2]
[Ni(L)2Cl2]
Brown
Green
Green
[Ni(L)2(NO3)2]
(8.10)
(29.81)
(2.76)
(15.45)

166
S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
diametrically and growth inhibition (I) was calculated using the
formula: I (%) = (C ꢁ T)/C ꢃ 100, where I = % inhibition, C = radial
diameters of the colony in control, T = radial diameter of the colony
in test compound.
(2H, H2NA), d 1.650 ppm (s) (3H, ACH3) d 7.266–7.860 ppm (m)
(4H, APhA).
Magnetic moments
Molecular modeling
The observed magnetic moments of Cu(II) and Ni(II) complexes
are given in Table 1. The observed values of magnetic moment for
complexes are generally diagnostic of the coordination geometry
around the metal ion. Room temperature magnetic moment of
the Cu(II) complexes lies in the range of 1.94–2.02 BM, correspond-
ing to one unpaired electron. The magnetic moment observed for
the Ni(II) complexes lies in the range of 2.96–3.02 BM correspond-
ing to two unpaired electrons [28].
The ligands and the complexes were modeled by MOPAC 2007
[26] program in gas phase using PM6 level of theory [27]. Selected
parts of the complexes not containing the metal ion were preop-
timized using molecular mechanics methods. Several cycles of en-
ergy minimization had to be carried for each of the molecules.
Geometry was optimized using Eigen Vector following. The Root
Mean Square Gradient for the molecules were all less than one. Self
Consistent Field was achieved in each case. Vibrational analysis
was done to check the absence of imaginary frequencies.
Infrared spectra
Results and discussion
The assignments of the significant IR spectral bands of ligand
and its Cu(II), Ni(II) complexes are presented in Table 2. In princi-
ple, the ligand can exhibit thione-thiol tautomerism since it con-
The complexes were synthesized by reacting ligand with the
metal ions in 2:1 M ratio in ethanolic medium. The ligand behaves
as bidentate and coordinated through sulfur of AC@S group and
nitrogen atoms of AC@N group. The analytical data, magnetic mo-
ments and spectral analysis agree well with the proposed compo-
sition of formed complexes. All the complexes have shown good
solubility in DMSO. The molar conductance of the complexes in
tains a thioamide ANHAC@S functional group. The
at 2565 cmꢁ1 is absent in the IR spectrum of ligand but
band at ca. 3209 cmꢁ1 is present, indicating that in the solid state,
m(SAH) band
m
(NAH)
the ligand remains as the thione tautomer. The position of m(C@N)
band of the thiosemicarbazone appeared at 1585 cmꢁ1 is shifted
towards lower wave number in the complexes indicating coordina-
tion via the azomethine nitrogen [29,30]. This is also confirmed by
the appearance of band in complexes in the range of 455–
fresh solution of DMSO lies in the range of 10–20
X
ꢁ1 cm2 molꢁ1
indicating their non-electrolytic behavior. Thus, the complexes
may be formulated as [M(L2)X2] (where M = Cu(II), Ni(II); L = 3-Bro-
moacetophenone thiosemicarbazone, X = CH3COOꢁ, Clꢁ, NO3ꢁ).
468 cmꢁ1, which has been assigned to the
m
(MAN) [31]. A medium
band found at 1103 cmꢁ1 is due to the
m
(NAN) group of the thio-
semicarbazone. The position of this band is shifted towards higher
wave number in the spectra of complexes. It is due to the increase
in the bond strength, which again confirms the coordination via
the azomethine nitrogen. The band appearing at ca. 783 cmꢁ1 cor-
Mass spectrum
The peak obtained at 271 corresponding to molecular ion peak
(M)+ (Supplementary material). Atomic mass of molecule is calcu-
lated as 271 amu for molecular formula (C9H10N3SBr). An isotopic
peak because of Br is also obtained at 273 (M + 2)+. Large number
of peaks of varying intensity present in the spectrum correspond
the 155, 171, 181, 196, 211, 254 and 256 fragments (Supplemen-
tary material) getting generated during the analysis. Other peaks
at 73, 113 might be the isotopic peaks because of bromine group.
responding to m(C@S) in the IR spectrum of ligand is shifted to-
wards lower wave number. It indicates that thione sulfur
coordinates to the metal ion [32]. Thus, it may be concluded that
the ligand behaves as bidentate chelating agent coordinating
through azomethine nitrogen and thiolate sulfur [33].
Anions
M
þ ꢁ CH3 ¼ 256; Mþ ꢁ NH3 ¼ 254; Mþ ꢁ CH2NS
¼ 211; Mþ ꢁ NH2CNSH ¼ 196; Mþ ꢁ CH3NHCSNH2
¼ 181; Mþ ꢁ Br ¼ 192; Mþ ꢁ C6H4Br ¼ 171:
The IR spectra of Cu(II) and Ni(II) acetato complexes showed the
medium intensity bands at 1471–1490 and 1327–1340 cmꢁ1, as-
signed to ma(CAO) and ms(CAO), respectively. The difference be-
tween these two frequencies is ꢄ144–150 cmꢁ1, which strongly
supported that both acetate ions are coordinated to the metal ion
in a unidentate fashion [32] (Fig. 1). The infrared spectrum of the
1H NMR spectrum of ligand
1H NMR spectrum of ligand (Supplementary material) (L = 3-
Bromoacetophenone thiosemicarbazone) (in d6 – DMSO) exhibits
following signals: d 8.760 ppm (s) (1H, HNACS), d 6.461 ppm (s)
Cu(II) and Ni(II) nitrato complexes showed
1 = 1279–1320, 2 = 1073–1023 and
indicating monodentate nature of nitrate group [34].
m
5 = 1384–1410,
m
m
D
(m5
ꢁ
m
1) = 105–90 cmꢁ1
Table 2
Important infrared spectral bands (cmꢁ1) and their assignments.
Compounds
Assignments
(NAH) (C@O)
[Cu(L)2(CH3COO)2] 3165
Bands due to anions
m
m
m
(C@N)
m
(C@S)
m(MAN)
1491
782
440
m
as(OAc) = 1471,
m
s(OAc) = 1327,
D
m
= 144 cmꢁ1 indicating monodentate nature of acetate
group [29]
[Cu(L)2Cl2]
[Cu(L)2(NO3)2]
3147
3169
1557
1592
781
783
439
460
m
5 = 1384,
nitrate group [29]
as(OAc) = 1490,
group
m
1 = 1279,
m
2 = 1073 and
D
(
m5
ꢁ
m
1) = 105 cmꢁ1 indicating monodentate nature of
[Ni(L)(CH3COO)2]
3286
1658
1545
482
m
m
s(OAc) = 1340,
D
m
= 150 cmꢁ1 indicating monodentate nature of acetate
[Ni(L)Cl2]
[Ni(L)(NO3)2]
3195
3194
1686
1676
1570
1567
437
454
m
5 = 1410,
m1 = 1320, m2 = 1021and D(m5 ꢁ m
1) = 90 cmꢁ1 indicating monodentate nature of
nitrate group

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
167
Fig. 1. IR spectra of [Cu(L)2(CH3COO)2] complex.
Electronic spectra
parameter b was readily obtained by using the relation b = B (com-
plex)/B (free ion), where B (free ion) for Ni(II) is 1041 cmꢁ1 [41].
The values of b lie in the range 0.19–0.37. These values indicated
The electronic spectra of the Cu(II) complexes showed three
bands in range of 9728–10,560, 16,271–18,622 and 27,322–
the covalent character in metal ligand ‘
r’ bond.
35,211 cmꢁ1 which can be assigned to 2B1g ? 2A1g 2B1g ? 2B2g
,
and 2B1g ? 2Eg transitions respectively, corresponding to tetrago-
nal geometry [35]. Electronic spectra of Ni(II) complexes showed
bands in the region of 9488–9653, 10,787–11,121 and 20,576–
21,459 cmꢁ1. An examination of these bands indicates that the
complexes have an octahedral geometry and might possess D4h
symmetry [36]. The ground state of Ni(II) in an octahedral coordi-
nation is 3A2g. Thus, these bands may be assigned to the three spin
allowed transitions [37,38] and the fourth one may be considered
Electronic paramagnetic resonance spectra
EPR spectra of Cu(II) complexes were recorded at room temper-
ature as polycrystalline sample, on X band at frequency of 9.1 GHz
under the magnetic-field strength of 3000G. The analysis of spectra
of Cu(II) complexes (Supplementary material) gives gk = 2.098–
2.298, g\ = 2.08–2.234 and G = 1.27–2.62 (Table 4). The trend
gk > g\ > 2.0023 observed for the complex indicates that unpaired
electron is localized in dx2 ꢁ y2 orbital of the Cu(II) ion and the
spectral features are a characteristic of axial symmetry. Thus, a
tetragonal geometry is confirmed for the aforesaid complex [42].
G = (gk ꢁ 2)/(g\ ꢁ 2), which measures the exchange interaction
between the metal centers in a polycrystalline solid, has been cal-
culated. According to Hathaway, if G > 4, the exchange interaction
is negligible, but G < 4 indicates considerable exchange interaction
in the solid complexes. The ‘‘G’’ value for Cu(II) complexes reported
in this paper, is <4 indicating the exchange interaction in solid
complexes [43].
as a charge transfer band, 3A2g (F) ? 3T2g (F) (
m
1), 3A2g (F) ? 3T1g (F)
3
(m
2) and A2g (F) ? 3T1g (P) (
m
3) transitions, respectively corre-
sponding to an octahedral geometry of Ni(II) complexes.
Ligand field parameters
Various ligand field parameters were calculated and listed in
Table 3. The values of Dq have been calculated from transition en-
ergy ratio diagram [39]. Our results are in agreement with the
same type of complexes reported earlier [40]. The Nephelauxetic
Table 3
Electronic spectral bands (cmꢁ1) and ligand field parameters of the complexes.
Complexes
cmax (cmꢁ1
)
e
(L molꢁ1 cmꢁ1
)
m2
/m1
Dq (cmꢁ1
)
B (cmꢁ1
)
b
LFSE (KJ molꢁ1
)
[Cu(L)2 (CH3COO)2
[Cu(L)2Cl2]
[Cu(L)2(NO3)2]
[ Ni(L)2(CH3COO)2
[Ni(L)2Cl2]
10,040, 18,622, 27,322
10,560, 18,653,
9728, 10,787, 35,211
9653, 11,123, 21,459
9506, 11,050, 20,576
9488, 10,787, 23,474
52, 90, 150
57, 94, 134
38, 82, 126
31, 54, 121
28, 46, 137
47, 89, 148
1.85
1.76
1.11
1.15
1.16
1.13
965
951
949
242
207
387
0.23
0.19
0.37
138.553
136.446
136.187
[Ni(L)(NO3)2]
Table 4
EPR Spectral data and bonding coefficient parameters of Cu(II) complexes.
Complexes
gII
g\
giso
kII
k\
a
b
G
[Cu(L2)2(CH3COO)2]
[Cu(L2)2Cl2]
[Cu(L2)2(NO3)2]
2.298
2.21
2.098
2.234
2.08
2.051
2.255
2.123
2.067
0.914
0.951
0.396
0.956
0.975
0.63
0.914
0.951
0.396
1.046
1.026
1.588
1.27
2.625
1.922

168
S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
Molecular modeling
In case of ligand (L) it is noticed that the HOMO orbitals
(ꢁ8.68466 eV) are located on the substituent of the phenyl group
while the LUMO orbitals (ꢁ0.72565 eV) on the phenyl group. Com-
puted dipole moment is 5.356 Debye. NAN bond lengths are
1.37 A, NAC 1.39, 1.36 A, C@S 1.68 A, C@N 1.31 A and CABr
1.91 A (Supplementary material).
In the Cu(II) complexes with ligand the two sulfa amido ligands
occupying the equatorial position and the Clꢁ/nitrate are in the
apical position bound trans fashion in a distorted octahedral geom-
etry (Supplementary material). The bond lengths and angles are
close to those reported in literature [44]. The copper atom lies on
the mean plane of the two chelating nitrogen and two chelating
oxygen atom. The two phenyl groups on the ligands are exactly
parallel to each other. The chelating part of the ligand adopts a dis-
torted pentagonal arrangement with the metal centre as one of the
apices. The important bond distances and angles are summarized
in Tables 5 and 6 for the copper complexes. Attempts to optimize
the [Cu(L)2(CH3COO)2] and Ni(II) complexes were not successful.
Br
CH3
C
N
X
NH2
S
C
HN
N
M
X
NH
C
S
N
C
H2
H3
C
Br
(Where X = Cl-, NO3 , CH3COO- and M=Cu2+, Ni2+)
-
Fig. 2. Proposed structures of Cu(II) and Ni(II) complexes.
Antibacterial activity
Thermal analysis
The data presented in Table 7 indicated that some of the com-
plexes showed better activities against Xanthomonas campestris
pv. campestris (Xc) as well as R. solanacearum (Rs) than the parent
ligand. Ligand did not show any activity against these two bacterial
pathogens. The complex [Cu(L)2(CH3COO)2] was found to be most
active against both the bacterial pathogens at all concentrations
The thermal stability of Cu(II) complex is studied by controlling
heating rates 10 °C per minute under nitrogen atmosphere. Ther-
mogram of Cu(II) complex is stable up to 250 °C, indicated the ab-
sence of lattice water as well as coordinated water. Generally in TG
lattice water loses at low temperature region between 60–120 °C,
where as coordinated water requires 120–250 °C. Absence of water
molecule in Cu(II) complex is supported by the DTA curve, which
represents weight loss by endothermic bands. The DTA of copper
complex has no endothermic band in the range of 60–250 °C.
Endothermic bands present at high temperature in DTA of Cu(II)
complex is due to loss of organic molecules and finally metal
may converts into its oxide [45,46]. In addition to endothermic
bands, the DTA curves of the complex also show exothermic bands.
These bands appear at high temperature and represent phase tran-
sition, oxidation and/or decomposition of the complex.
i.e. 250, 500 and 1000 l
g mlꢁ1 but Streptomycin (standard)
showed better activities than the complexes at all concentrations.
Complex [Ni(L)2(CH3COO)2] and [Ni(L)2(NO3)2] showed activity
only at highest concentrations against X. campestris. Other testing
compounds did not show the activities against pathogen X.
campestris.
The results also indicated that the complex [Cu(L)2(CH3COO)2]
showed best activities against bacteria R. solanacearum.
With bacteria R. solanacearum the order of activity was found in
order:
Streptomycin (standard) > [Cu(L)2(CH3COO)2] > [Cu(L)2(Cl)2] >
[Ni(L)2(CH3COO)2] > [Ni(L)2(NO3)2] > [Cu(L)2(NO3)2] > [Ni(L)2(Cl)2].
On the basis of above discussion following structures (Fig. 2)
can be proposed for the synthesized complexes.
In vitro screening for antifungal property of compounds
From Table 8, it is evident that the activity of the ligand in-
creased with increased concentration for the fungus B. cinerea
(Supplementary material). The activity order for fungus B. cinerea
was found to be:
[Cu(L)2(CH3COO)2] > [Cu(L)2(NO3)2] > [Cu(L)2(Cl)2] > [Ni(L)2(Cl)2] >
[Ni(L)2(NO3)2] > [Ni(L)2(CH3COO)2] > Ligand > Bavistin i.e. Cu(II) com-
plexes > Ni(II) complexes > Ligand > Bavistin.
Antimicrobial studies
The antimicrobial screening data show that the compounds ex-
hibit antimicrobial properties and it is also important to note that
some of the metal chelates exhibit more inhibitory effects than the
parent ligands. The increased activity of the metal chelates can be
explained on the basis of chelation theory [47].
For fungus Macrophomina phaseolena the activity order was:
Table 5
Selected bond lengths (A°).
Ligand
CuAN(lig)
CuAS(lig)
CuAO(nitrate)
CuACl
CuA(SNSN mean plane distance)
[Cu(L)2Cl2]
[Cu(L)2(NO3)2]
1.95, 1.95
1.94, 1.94
2.07, 2.07
2.03, 2.03
–
2.65, 2.65
–
0
0
2.06, 2.06
Table 6
Selected bond angles (°).
Ligand
N(lig)ACuAN(lig0)
S(lig)ACuAS(lig0)
O(nit)ACuAO(nit0)
ClACuACl0
N(lig)ACuAS(lig)
N(lig)ACuAS(lig0)
[Cu(L)2Cl2]
[Cu(L)2(NO3)2]
180.0
180
179.9
180
–
179.9
–
84.2, 84.2
84.1, 84.1
95.9, 95.9
95.9, 95.9
179.3

S. Chandra et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 113 (2013) 164–170
169
Table 7
Antibacterial screening data of the ligand and its Cu(II) and Ni(II) complexes.
Compounds
Diameter of inhibition zone (mm) (conc. in lgmlꢁ1)
Xanthomonas campestris pv. Campestris
Ralstonia solanacearum
250
500
1000
250
500
1000
Ligand (L)
0
0
0
0
0
0
[Cu(L)2 (CH3COO)2]
[Cu(L)2(Cl)2]
[Cu(L)2(NO3)2]
[Ni(L)2(CH3COO)2]
[Ni(L)2(Cl)2]
19.05
0
0
0
20
0
0
0
0
26.8
0
0
14.1
0
16.5
11
0
0
0
21.5
11
0
14
0
25.3
15.1
12
11
11
0
[Ni(L)2(NO3)2]
Streptomycin (standard)
Solvent (DMSO)
0
19
0
0
22
0
12
26
0
0
26
0
12
30
0
14
Not tested
0
Table 8
Antifungal screening data of the ligands and its Cu(II) and Ni(II) complexes.
Compounds
Fungal inhibition (%) (conc. in l )
g mlꢁ1
Botrytis cinerea
Macrophomina phaseolina
Phoma glomerata
500
800
1000
1500
500
800
1000
1500
500
800
1000
1500
Ligand (L)
[Cu(L)2 (CH3COO)2]
[Cu(L)2(Cl)2]
[Cu(L)2(NO3)2]
[Ni(L)2(CH3COO)2]
[Ni(L)2(Cl)2]
[Ni(L)2(NO3)2]
Bavistin (standard)
45.83
54
72
58
64
48
42
55
0
61
71.4
66
78
69
76
69
0
75
100
100
100
100
100
100
0
ꢁ5.4
74.7
48.3
–
52.4
65.7
62.8
53.2
78.7
–
59.6
0.5
68.8
73.5
79.5
72.0
98
70
39.04
–
–
Not tested
–
–
–
48
62
61
63
66.2
55
69
96
80
–
–
–
–
–
–
87.3
80.1
78.4
90.36
100
100
100
–
–
–
–
72
64
67
100
78
78
94
100
100
100
100
100
–
ꢁ25
58.44
76.19
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Bavistin > [Ni(L)2(Cl)2] > [Ni(L)2(NO3)2] > [Cu(L)2(CH3COO)2] >
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With the fungus P. glomerata the order of activity was Bavistin
(standard) > [Ni(L)2(CH3COO)2] > [Ni(L)2(NO3)2] > [Ni(L)2(Cl)2] >
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Authors are thankful to the Sophisticated Analytical Instrument
Facility of IIT Bombay for recording EPR spectra and USIC, Univer-
sity of Delhi, for recording IR, Mass and NMR spectra. We also
acknowledge the financial assistance of UGC and DRDO Delhi.
We are also thankful to Prof. Usha Dev, IARI Pusa, New Delhi, for
providing the laboratory facilities for biological studies.
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Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.saa.2013.04.114.
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