Synthesis, spectroscopic studies and electrochemistry of palladium (II) macrocyclic complexes derived from a new tetraazahalogen substituted ligands by template method and their antimicrobial and pesticidal activities

Article abstract of DOI:10.1016/j.saa.2011.03.057

A new series of Pd(II) macrocyclic complexes have been synthesized by template condensation of bis(benzil)4-chloro 1,2-phenylenediamine (ML ¹) and bis(benzil)4-fluro 1,2-phenylenediamine (ML²) respectively, with appropriate diamine i.e. 1,2-phenylenediamine, 4-chloro 1,2-phenylenediamine and 4-fluro 1,2-phenylenediamine in the presence of PdCl₂ to form complexes of the type [Pd(C₄₀H ₂₆N₄ClF)]Cl₂, [Pd(C₄₀H ₂₇N₄X)]Cl₂ and [Pd(C₄₀H ₂₆N₄X₂)]Cl₂, where X = Cl, F. The complexes have been characterized with the help of elemental analysis, IR, ¹H NMR, electronic spectra, conductance measurement, magnetic susceptibility, cyclic voltammetry and X-ray powder diffraction studies. On the basis of these studies a square planar geometry has been proposed around the metal ion. The newly synthesized ligands and their complexes have been screened for antimicrobial and pesticidal activities. The results obtained from bioassays indicate that this class of compounds can be utilized for the design of new substance with pesticidal activity and promising antimicrobial activity.

Full text of DOI:10.1016/j.saa.2011.03.057

Spectrochimica Acta Part A 79 (2011) 940–947
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and
Biomolecular Spectroscopy
journal homepage: www.elsevier.com/locate/saa
Synthesis, spectroscopic studies and electrochemistry of palladium (II)
macrocyclic complexes derived from a new tetraazahalogen substituted ligands
by template method and their antimicrobial and pesticidal activities
Iffat Masih, Nighat Fahmi∗
Department of Chemistry, University of Rajasthan, Jaipur 302004, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 31 July 2010
Received in revised form 18 February 2011
Accepted 9 March 2011
A new series of Pd(II) macrocyclic complexes have been synthesized by template condensation of
bis(benzil)4-chloro 1,2-phenylenediamine (ML1) and bis(benzil)4-fluro 1,2-phenylenediamine (ML2)
respectively, with appropriate diamine i.e. 1,2-phenylenediamine, 4-chloro 1,2-phenylenediamine and 4-
fluro 1,2-phenylenediamine in the presence of PdCl2 to form complexes of the type [Pd(C40H26N4ClF)]Cl2,
[Pd(C40H27N4X)]Cl2 and [Pd(C40H26N4X2)]Cl2, where X = Cl, F. The complexes have been characterized
with the help of elemental analysis, IR, 1H NMR, electronic spectra, conductance measurement, magnetic
susceptibility, cyclic voltammetry and X-ray powder diffraction studies. On the basis of these studies a
square planar geometry has been proposed around the metal ion. The newly synthesized ligands and
their complexes have been screened for antimicrobial and pesticidal activities. The results obtained from
bioassays indicate that this class of compounds can be utilized for the design of new substance with
pesticidal activity and promising antimicrobial activity.
Keywords:
Pd(II) macrocyclic complexes
Spectral studies
Electrochemistry
Antimicrobial activity
Pesticidal activity
Minimum inhibitory concentration
© 2011 Elsevier B.V. All rights reserved.
1. Introduction
compounds depends upon the stereochemical requirements and
coordinating features of metal ion [11]. The coordination chem-
The design and study of well arranged metal containing macro-
cycles is an interesting field of chemistry and has attracted the
interest of both inorganic and bioinorganic chemists in recent years
[1]. The field of macrocyclic chemistry of metals is developing
very rapidly because of its importance in the area of coordina-
tion chemistry [2]. The transition metal coordination chemistry
of macrocyclic ligands has been developed extensively in the past
decades [3–5]. This enormous growth is due to the synthesis of
great number and variety of synthetic macrocycles which behave
as coordinating agents for metal ions. For various applications
tetraazamacrocyclic ligands are of special interest, and coordinat-
ing side chains may increase the stability of the metal complexes
and tune the selectivity between various metal ions [6]. An intrigu-
ing feature of these systems is that the size of the ligands can be
changed with relative ease by synthetic means [7–9]. Template con-
densation lies at the heart of macrocyclic chemistry and is one of
the most highlighted methods. Metal template condensation often
provides selective route towards the products that are not obtain-
able in absence of metal ion [10]. Finally design of the macrocyclic
istry of square planar metal complexes involving nitrogen donor
ligands has excited great interest among chemists in recent years
due to the applications of these in catalysis and their relevance to
bioinorganic systems [12]. Biologically potent square planar macro-
cyclic complexes of Pd(II) and Pt (II) have been reported [13]. Singh
et al. [14] have reported the antifertility and antimicrobial activities
of tetraazamacrocyclic complexes of lead, palladium and platinum.
Electrochemical behaviour of these complexes has also been stud-
ied [7]. Macrocyclic complexes have been used as drugs and are
reported to possess a wide variety of biological activity against
bacteria, fungi and certain type of tumors and they are also useful
models for biological process [15,16]. Complexes of Pd(II) are new
reagents for selective hydrolytic cleavage of peptide and proteins
[17]. The cytotoxic and antiproliferative studies show that the com-
plexes of Pd(II) exhibit good cytotoxic activity against different cell
lines [18]. In view of the above applications, in the present paper
template synthesis of tetraaza macrocyclic complexes of Pd(II) is
reported. These complexes have been characterized with the help
of various physicochemical techniques. The electron transfer mech-
anism of the metal is investigated by the aid of cyclic voltammetry.
Further antibacterial and antifungal activities of the ligands and
their metal complexes have been determined by screening of the
compounds against various bacterial and fungal strains. The results
obtained, were compared with antibacterial and antifungal activ-
ities shown by standard bactericide Streptomycin and fungicide
∗
Corresponding author. Tel.: +91 141 2704677(O)/2763337(R);
fax: +91 141 2708621.
E-mail addresses: iffatmasih@gmail.com (I. Masih), nighat.fahmi@gmail.com
(N. Fahmi).
1386-1425/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.saa.2011.03.057

I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
941
Table 1
The physico-chemical properties and analytical data of the ligands and their complexes.
S.N.
Compound
M.W.
Colour
M.P. (0 ◦C)
Yield
Elemental analysis found (calculated)%
Pd
C
H
N
Cl
1
2
3
4
5
6
7
C34H23N2O2Cl
C34H23N2O2F
524.13 (527.02)
508.17 (510.56)
784.04 (794.44)
772.32 (776.45)
801.19 (810.90)
751.26 (760.00)
769.25 (777.99)
Black
85 ◦
74 ◦
C
C
70%
75%
75%
65%
65%
67%
73%
77.15 (77.48)
79.03 (79.98)
60.11 (60.47)
61.44 (61.87)
59.10 (59.24)
63.10 (63.21)
61.75 (61.75)
4.24 (4.39)
4.49 (4.54)
3.21 (3.29)
3.44 (3.50)
3.11 (3.23)
3.39 (3.58)
3.19 (3.36)
5.19 (5.31)
5.32 (5.48)
6.99 (7.05)
7.11 (7.21)
6.37 (6.90)
7.20 (7.37)
7.01 (7.20)
6.02 (6.73)
–
13.10 (13.38)
13.21 (13.69)
17.05 (17.48)
9.25 (9.32)
Light brown
Dark gray
Dark gray
Black
Light green
Brown
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
280 ◦
290 ◦
292 ◦
275 ◦
285 ◦
C
C
C
C
C
13.12 (13.39)
13.48 (13.70)
13.01 (13.12)
13.99 (14.00)
13.46 (13.67)
8.99 (9.11)
Bavistin. These complexes were also evaluated for their pesticidal
activity and the results are quite encouraging.
trode, and an Ag/Ag+ reference electrode. Glassy carbon electrode
surfaces were polished with alumina, rinsed in water, and air-
dried immediately before use. The DMSO solution (containing
tetra n-butylammonium iodide, as supporting electrolyte, 10−3
molar concentration of the complexes) was placed in a single-
compartment electrochemical cell and degassed by bubbling with
N2(g) saturated with DMSO. A N2 atmosphere was continuously
maintained above the solution while the experiments were in
progress.
2. Experimental
2.1. Materials
All the chemical used were of AnalaR grade. Palladium chloride
(PdCl2) and various diamines were purchased from Sigma–Aldrich.
Solvents of analytical grade were distilled from appropriate drying
agents immediately prior to use.
2.3. Synthesis of ligands (ML1 and ML2)
2.2. Analytical and physical measurements
The ligands (ML1 and ML2) were prepared by dissolving benzil
(20 mmol, 4.20 g) in 40 mL of ethanol then calculated amount of
diamine i.e. 4-chloro 1,2-phenylenediamine (10 mmol, 1.42 g) or
4-fluro 1,2-phenylenediamine (10 mmol, 1.26 g) was added in 2:1
molar ratio. The reaction mixture was heated under reflux for 4–6 h
on a ratio head. It was then concentrated to half of the volume. The
solution was cooled and the excess solvent was removed by slow
evaporation by keeping it in a desiccator overnight. The coloured
crystalline products so obtained were purified by recrystallization
in the same solvent and dried in vacuo. The analysis and physical
properties of these ligands are given in Table 1.
Elemental analysis of C and H were performed at CDRI Lucknow.
The nitrogen and chlorine contents of the complexes were esti-
mated by the Kjeldahl’s and Volhard’s method, respectively [19].
Palladium was estimated gravimetrically [20]. Molecular weights
were determined by Rast Camphor method. Melting point was
determined by using capillaries in electrical melting point appara-
tus. The electronic spectra were recorded on an Ultraviolet visible
spectrophotometer 752/752N, infrared spectra of the ligands and
their complexes were recorded with the help of Nicolet Megna
FTIR-550 spectrophotometer on KBr pellets. 1H NMR spectra were
recorded on a JEOL-AL-300 FT NMR spectrometer in DMSO-d6 using
TMS as the internal standard, XRD were measured on Panalytical
make Xpert Pro 3040 and magnetic susceptibility were measured
on a model 155 vibrating sample magnetometer at RSIC, IIT Chen-
nai. The conductivity values measured on 10−3 mol dm−3 solution
in DMF at room temperature on century digital conductivity meter
model CC601.
The synthetic route of the ligands has been shown in Fig. 1 and
the structure of bis(benzil)4-chloro 1,2-phenylenediamine (ML1) is
given in Fig. 2.
2.4. Synthesis of the Pd(II) macrocyclic complexes
The complexes were synthesized by the template con-
densation of ligands bis(benzil)4-chloro 1,2-phenylenediamine
(ML1) or bis(benzil)4-fluro 1,2-phenylenediamine (ML2) with
various diamine such as 1,2-phenylenediamine, 4-chloro 1,2-
phenylenediamine and 4-fluro 1,2-phenylenediamine in the
The cyclic voltammetric experiments were carried out with
a three electrode apparatus using a CH instrument 1200A elec-
trochemical analyzer. Cyclic voltammetric data were recorded
using a glassy carbon working electrode, a platinum counter elec-
Fig. 1. Synthetic route of the ligands.

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I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
cyclic complexes [Pd(C40H26N4ClF)]Cl2, [Pd(C40H27N4X)]Cl2 and
[Pd(C40H26N4X2)]Cl2 of the type where X = Cl, F. The resulting
macrocyclic complexes are coloured, solids, stable at room tem-
perature and non hygroscopic. They are soluble in DMF and DMSO.
Molecular weight determination showed that they are monomeric
in nature. The molar conductance measurements of 10−3 M solu-
tion in DMF indicate that the complexes are 1:2 electrolytes. The
molar conductance of the Pd(II) macrocyclic complexes are given
in Table 2.
3.2. Magnetic susceptibility measurement and electronic spectra
The magnetic susceptibility measurements show that all the
palladium (II) macrocyclic complexes are diamagnetic, as expected
of square planar d8 complexes. The values lie in the range
(0.3–0.8 × 10−6) c.g.s. units.
Fig. 2. Structure of bis(benzil)4-chloro 1,2-phenylenediamine (ML1).
presence of PdCl2.
The electronic spectra of the ligands and their complexes were
recorded in distilled DMSO. The spectra of both the ligands ML1and
ML2 show a broad band at 400 nm which can be assigned to the
n–␲* transitions of the azomethine group which undergoes a blue
shift in the complexes due to the polarization within the ꢀC N chro-
mophore caused by the metal–ligand electron interaction during
the chelation. The shift of this band in the spectra of the complexes
suggests the coordination of nitrogen to metal atom. The spectra of
the complexes show three bands due to three d–d spin allowed
transitions. These are corresponding to the transitions from the
2.4.1. Synthesis of [Pd(C40H26N4ClF)]Cl2 complex
A weighed amount of methanolic solution of ligand ML1
(10 mmol, 5.27 g) was taken into a 100 mL round bottom flask. The
solution of ligand was mixed with the methanolic solution of 4-
fluro 1,2-phenylenediamine (10 mmol, 1.26 g) and PdCl2 (10 mmol,
1.77 g). After addition of all the reagents, the contents were boiled
under reflux for about 7–8 h on a ratio head; the reaction mixture
was concentrated to half of its volume and kept in a desiccator at
room temperature. The complexes obtained as solids, were washed
with methanol and dried under vacuo.
three lower lying d orbitals to the empty dx
orbital. The ground
2
2
−y
state is 1A1g and the excited states corresponding to the above tran-
2.4.2. Synthesis of [Pd(C40H27N4X)]Cl2 complexes (X = Cl, F)
To obtain this type of complexes the methanolic solution of lig-
and ML1 ((10 mmol, 5.27 g) or ML2 (10 mmol, 5.10 g) was mixed
with the methanolic solution of 1,2-phenylenediamine (10 mmol,
1.08 g) in the presence of PdCl2 (10 mmol, 1.77 g). After addition
was completed, the contents were refluxed for 7–8 h on a ratio head.
It was then concentrated to half of the volume by removing the sol-
vent and kept in a desiccator at room temperature. The complexes
obtained as solids, were washed with methanol and dried under
vacuo.
sitions are 1A2g 1B1g and 1E1g in the order of increasing energy. The
,
three orbital parameters (ꢀ1, ꢀ2, and ꢀ3) were calculated using
a value of F2 = 10F4 = 600 cm−1 for Slater Condon interelectronic
repulsion [21] which are given in Table 2. The v2/v1 was also cal-
culated and is in close agreement with the data reported by others
for square planar complexes [21,22].
3.3. IR-spectra
The tentative absorption frequencies of the ligands and their
Pd(II) complexes along with their assignment are listed in Table 3.
The bands due to vas(NH2) at 3380 cm−1, vs(NH2) at 3250 cm−1 and
v(C O)in the region1670–1680 cm−1 werepresentin the spectraof
diamines and ligands respectively but were absent in the infrared
spectra of all the complexes. The disappearance of the vas(NH2),
vs(NH2) and v(C O) bands and appearance of absorption band near
at 1610–1615 cm−1 indicates the formation of macrocyclic frame-
work, as these bands may be assigned to v(C N) [23] The value of
absorption band due to v(C N) is lower than that usually occur for
azomethine group which supports the coordination of this group to
the metal atom [12] and formation of macrocyclic complexes. This
lower value of v(C N) stretching may be explained on the basis of a
drift of lone pair density of azomethine nitrogen towards the metal
atom. The phenyl ring absorption appears in the 1465–1495 and
1355–1390 cm−1 region are assigned to vasymC6H5 and vsymC6H5,
respectively. The mode of coordination is further supported by the
presence of the new bands at 360–390 cm−1 due to v(Pd ← N).
2.4.3. Synthesis of [Pd(C40H26N4X2)]Cl2 complex (X = Cl)
This type of complex was prepared by mixing a methano-
lic solution of ML1 (10 mmol, 5.27 g) with methanolic solution
of 4-chloro 1,2-phenylenediamine (10 mmol, 1.42 g) and PdCl2
(10 mmol, 1.77 g). The reaction mixture was heated under reflux for
7–8 h. The reaction mixture was concentrated to half of its volume.
After cooling, the solution was kept overnight in a desiccator at
room temperature. The complexes obtained as solids, were washed
with methanol and dried under vacuo.
2.4.4. Synthesis of [Pd(C40H26N4X2)]Cl2 complex (X = F)
This complex was prepared by following the above procedure,
using the ligand ML2 and 4-fluro 1,2-phenylenediamine in the pres-
ence of PdCl2 in 1:1:1 molar ratio.
All the complexes were recrystallized from 1:1 molar solution of
methanol and benzene. The purity of the complexes was checked by
thin layer chromatography (TLC). The analysis and physical prop-
erties of these complexes are given in Table 1.
3.4. 1H NMR spectra
The template synthesis of the complexes may be represented by
the following scheme in Fig. 3
Further evidence for the coordinating mode of the ligands was
obtained from 1H NMR spectra which were recorded in DMSO-
d6. The spectra of the ligands and their complexes do not show
any signal assignable to primary amino protons. This is strong
evidence that proposed macrocyclic complexes are formed by tem-
plate reaction. These complexes exhibit multiplet in the region ı
7.26–8.18 ppm, which is assigned to aromatic protons.
3. Result and discussion
3.1. Chemistry
The elemental analysis and spectral data suggested the
formation of the ligands (ML1and ML2) and their macro-

I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
943
Fig. 3. Synthetic route of the Pd(II) macrocyclic complexes.
Table 2
Molar conductance and electronic spectral data (cm−1) of palladium (II) complexes.
Complexes
Spectral bands (cm−1
)
Transitions
ꢀ1
ꢀ2
ꢀ3
v2/v1
Molar conductance
[Pd(C40H26N4ClF)]Cl2
17391
20833
25316
17241
21053
25000
17153
20408
24390
16949
20704
24510
17094
20202
24390
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
1A1g
→
→
→
→
→
→
→
→
→
→
→
→
→
→
→
1A2g(v1)
1B1g(v2)
1E1g(v3)
1A2g(v1)
1B1g(v2)
1E1g(v3)
1A2g(v1)
1B1g(v2)
1E1g(v3)
1A2g(v1)
1B1g(v2)
1E1g(v3)
1A2g(v1)
1B1g(v2)
1E1g(v3)
19490
5643
3183
1.19
159
161
169
167
170
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
19341
19253
19049
19194
5012
4455
4955
4308
3647
3682
3506
3888
1.22
1.18
1.22
1.18
Table 3
IR (cm−1) and 1H NMR (ı, ppm) spectral data of the ligands and their corresponding complexes.
S.N.
Compound
IR spectral data (cm−1
)
1H NMR spectral data
(ı ppm)
v(C O)
v(C N)
v(Pd ← N)
Aromatic protons (m)
1
2
3
4
5
6
7
C34H23N2O2Cl
C34H23N2O2F
1680
1670
1610
1620
1600
1598
1595
1600
1590
–
–
7.69–8.18
7.79–8.13
7.36–8.10
7.26–8.18
7.31–8.18
7.32–8.16
7.38–8.16
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
–
–
–
–
–
360
362
390
370
382
m = multiplet.
On the basis of analytical and spectral data the structures of the
complexes have been proposed. Fig. 4 represents 3D structure of
[Pd(C40H27N4Cl)]Cl2 macrocyclic complex.
deviation of 2-Theta = 0.10 and Alpha = 90, Beta = 90, Gamma = 90 at
the wavelength = 1.540598. Table 4 shows XRD measurement data
of [Pd(C40H26N4ClF)]Cl2.
3.5. X-ray powder diffraction studies
3.6. Electrochemical studies
The possible lattice dynamics of the finely powdered prod-
uct, [Pd(C40H26N4ClF)]Cl2 has been deduced on the basis of X-ray
powder diffraction studies and Fig. 5 shows the XRD pattern of
The electrochemical behaviour of Pd compound was studied by
cyclic voltammetric techniques on glassy carbon electrode (GCE).
Pd compound gave one well defined reduction peaks at −0.76 V
peak potential (Fig. 6) in the non-aqueous solution DMSO which is
attributed to the reduction of Pd(II) at glassy carbon electrode and
tetrabutylammonium iodide (TBI) react as a supporting electrolyte.
The reduction peak can be explained with the help of two electron
transfer during reduction of Pd(II) to Pd(0) [24]. No peak could be
observed in anodic direction of the reverse scans suggesting the
[Pd(C40H26N4ClF)]Cl2 compound. The observed interplanar spac-
˚
ing values (‘d’ in A) have been measured from the diffractogram of
the compound and the Miller indices h, k and l have been assigned
to each d value and 2-Theta angles are reported. The results show
that the compound belongs to ‘orthorhombic’ crystal system hav-
ing unit cell parameters as a = 25.75, b = 17.5, c = 10.20, maximum

944
I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
Table 4
XRD measurement data of [Pd(C40H26N4ClF)]Cl2.
h
k
l
2Theta (Exp.)
2Theta (Calc.)
2Theta (Diff.)
d (Exp.)
d (Calc.)
Intensity (Exp.)
3
3
9
8
3
7
4
5
0
3
3
6
1
0
1
2
4
2
24.380
27.512
32.481
36.404
39.945
43.334
24.427
27.499
32.475
36.394
39.958
43.350
−0.047
0.013
0.006
3.648
3.239
2.754
2.465
2.255
2.086
3.641
3.240
2.754
2.466
2.254
2.54
53.43
24.28
24.25
9.35
11.27
27.58
0.010
−0.013
−0.016
Fig. 7. Cyclic voltammogram of complex at different scan rates 50,100, 150 and
200 mV s−1
.
Fig. 4. 3D Structure of [Pd(C40H27N4Cl)]Cl2 macrocyclic complex.
Fig. 8. Plot of peak current vs scan rate for reduction peak of complex.
Fig. 5. XRD graph of [Pd(C40H26N4ClF)]Cl2.
irreversible nature of the electrode process. The peak potential
shifted towards more negative values with increase in scan rate,
(Fig. 7) confirming the irreversible nature of the reduction process.
The effect of scan rate (ꢁ1/2) on stripping peak current (ip) was
examined under the above experimental conditions (Fig. 8). As the
sweep rate is increased from 50 to 200 mV/s at a fixed concentration
10−3 M of the compound.
(i) The peak potential shifted cathodically.
(ii) The peak current increased steadily.
A straight line is obtained when ip is plotted against ꢁ1/2, which
may be expressed by the equation.
For reduction peak:
Y(ip) = 0.091ꢁ1/2 (mV/s) + 0.251 (␮A), r2 = 0.9994
Fig. 6. Cyclic voltammogram of complex at scan rate 100 mV s−1
.
All these facts pointed towards the diffusion-controlled nature
of the electrode process.

I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
945
Table 5
Comparison of properties of the synthesized Pd(II) macrocyclic complexes with related complexes.
Complex
Electronic transition (cm−1
)
IR bands v(C N)
Molar conductance (cm2
159
ꢂ
−1 mol−1
)
Geometry
Refs.
[Pd(C40H26N4ClF)]Cl2
17391 (v1)
1600
Square planar
This work
This work
This work
This work
This work
a
20833 (v2)
25316 (v3)
17241 (v1)
21053 (v2)
25000 (v3)
17153 (v1)
20408 (v2)
24390 (v3)
16949 (v1)
20704 (v2)
24510 (v3)
17094 (v1)
20202 (v2)
24390 (v3)
18348–18018 (v1)
21141–20618 (v2)
24509–24096 (v3)
18939–18656 (v1)
21505–20833 (v2)
28011–27027 (v3)
21276 (v1)
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
[Pd(C39H27N5)]Cl2
[Pd(C35H27N5)]Cl2
1598
161
Square planar
Square planar
Square planar
Square planar
Square planar
Square planar
1595
169
1600
167
1590
170
1625–1595
1615–1598
205–225
206–218
b
Pd[(TAAP)]I2
1602–1610
1610–1620
145.3
206
Square planar
Square planar
c
23809 (v2)
20747 (v1)
[Pd(C40H28N4)]Cl2
d
27933 (v2)
36764 (v3)
a, b, c, d taken from Refs. [14,7,8,9], respectively. (TAAP) tetrapyrazolo [1,5,9,13] tetraazacyclohexadecine.
v1
1A1g 1A2g, v2 1A1g 1B1g, v3 1A1g 1E1g
=
→
=
→
=
→
.
The structural data of Pd(II) macrocyclic complexes have been
compared with related derivatives described in the literature and
the data have been included in Table 5.
whereas media with Streptomycin were used as positive control.
The experiments were performed in triplicates.
4.3. In vitro antifungal activity
4. Biological assay
The newly prepared complexes were also screened for their
antifungal activity against Fusarium oxysporum (ATCC7808) and
Rhizopus nigricans (ATCC6227b) in DMSO by agar diffusion method
[26,27]. Sabourand’s agar media was prepared by dissolving pep-
tone (10 g), d-glucose (40 g) and agar (20 g) in distilled water
(1000 mL) and adjusting pH to 5.7. Normal saline water was used to
make suspension spore of fungal strain lawning. A loopful of partic-
ular fungal strain was transferred to 3 mL saline to get suspension
of corresponding species. Twenty milliliters of agar media were
poured into each petri dish. Excess of suspension was decanted and
plates were dried by placing in an incubator at 37 ◦C for 1 h using an
agar punch, wells were made and each well was labelled. A control
was also prepared in triplicate and maintained at 37 ◦C for 96 h. The
fungal activity of each compound was compared with Bavistin as
standard drug. The medium with DMSO as solvent was used as a
negative control whereas media with Bavistin were used as pos-
itive control. The experiments were performed in triplicates. The
cultures were incubated for 96 h at 35 ◦C and the growth was mon-
itored and the percentage of inhibition was calculated by equation:
4.1. Test microorganism
All the compounds were evaluated for their antimicrobial prop-
erties. MIC was recorded as minimum concentration which inhibits
the growth of microorganism. The results obtained were compared
with those of the standard drug Streptomycin for bacteria and Bav-
istin for fungi. The microorganisms used were E. coli (ATCC25922),
B. subtilis (ATCC6633), F. oxysporum (ATCC7808) and R. nigricans
(ATCC6227b). The synthesized macrocyclic complexes were also
tested for the pesticidal activity against fifth instar larva of Corcyra
cephalonica.
4.2. In vitro antibacterial activity
The newly prepared compounds were screened for their
antibacterial activity against Escherichia coli (ATCC25922) and Bacil-
lus subtilis (ATCC6633) by paper disc plate method [25]. Each
compound was dissolved in DMSO and solutions of the concentra-
tions (500 and 1000 ppm) were prepared separately. Paper discs of
Whatman filter paper (No. 42) of uniform diameter (5 mm) were cut
and sterilized in an autoclave. The paper discs soaked in the desired
concentration of the complex solutions were placed aseptically in
the petri dishes containing nutrient agar media (agar 20 g + beef
extract 3 g + peptone 5 g) seeded with E. coli (ATCC25922) and B.
subtilis (ATCC6633) bacteria strains separately. The petri dishes
were incubated at 37 ◦C and the inhibition zones were recorded
after 24 h of incubation. The antibacterial activity of common stan-
dard antibiotic Streptomycin was also recorded using the same
procedure as above at the same concentrations and solvent. The
medium with DMSO as solvent was used as a negative control
C − T
% of inhibition =
× 100
C
where C and T are the diameters of the fungal colony in the control
and the test plates, respectively.
4.4. Determination of minimum inhibitory concentration (MIC)
Minimum inhibitory concentration, MIC, is the lowest concen-
tration of test agent that inhibited visible growth of bacteria after
18 h incubation at 37 ◦C. The determination of the MIC involves a
semi quantitative test procedure, which gives an approximation
to the least concentration of an antimicrobial needed to pre-

946
I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
Table 6
Antibacterial screening data for the ligands and their complexes.
Compound
Diameter (mm) of inhibition zone after 24 h (conc. in ppm)
Bacillus subtilis
Escherichia coli
500
1000
7.2 0.05
500
1000
C34H23N2O2Cl
C34H23N2O2F
7
6
8
0.06
0.05
0.08
6.8 0.05
6.0 0.05
7.2 0.08
8.0 0.15
11 0.15
10 0.11
9
6
8
9
0.08
0.08
0.14
0.12
7
0.08
8.2 0.11
0.08
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
Streptomycin
8.5 0.03
11 0.08
9
8
9
11.2 0.08
10 0.08
12 0.34
11 0.11
10 0.20
20 0.18
0.05
0.05
9
0.03
9
0.08
16 0.01
18 0.11
17 0.18
Table 7
Antifungal screening data for the ligands and their complexes.
Compound
(%) Inhibition after 96 h (conc. in ppm)
Fusarium oxysporum
Rhizopus nigricans
50
100
200
50
100
200
C34H23N2O2Cl
C34H23N2O2F
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
42 0.75
35 0.69
48 0.70
46 0.55
49 0.50
37 0.45
39 0.57
61 0.10
53 0.60
39 0.55
58 0.51
55 0.55
57 0.55
43 0.69
45 0.32
90 0.80
65 0.34
50 0.52
67 0.55
64 0.71
67 0.49
52 0.55
54 0.57
100 0.10
28 0.53
29 0.54
35 0.22
33 0.55
37 0.59
31 0.52
35 0.39
55 0.10
47 0.39
35 0.40
50 0.50
48 0.62
52 0.66
49 0.50
52 0.55
88 0.10
61 0.77
53 0.89
66 0.36
63 0.53
68 0.42
57 0.50
59 0.60
99 0.30
[Pd(C40
H26N4F2)]Cl2
Bavistin
Table 8
Minimum inhibitory concentration (␮g/mL) of the ligands and their complexes.
Compound
Bacillus subtilis
Escherichia coli
Fusarium oxysporum
Rhizopus nigricans
C34H23N2O2Cl
C34H23N2O2F
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
50
50
50
25
25
50
50
50
50
50
25
25
50
50
6.25
12.5
3.125
3.125
3.125
6.25
12.5
12.5
6.25
6.25
6.25
6.25
6.25
[Pd(C40
H26N4F2)]Cl2
6.25
weighed and dissolved in methanol to prepare 1000 mg L−1 stock
solution. Further concentrations viz., 900, 800, 700, 600, 500, 400,
300, 200, 100 mg L−1 were prepared by serial dilution. 20 larvas
were released in each petri plate then 1 mL of each concentration
of various compounds was directly poured in each petri plate with
the help of a brush. Petri plates with test solution were rotated
vigorously and were kept at 27 1 ◦C and 70% relative humidity.
Mortality was observed after 96 h larva was considered dead if they
failed to respond to stimulus by touch. Control mortality was cor-
rected by using Abbott’s formula [31] and data was subjected for
probit analysis according to Finney [32].
vent microbial growth. The minimum inhibitory concentration was
determined by microbroth dilution method [28]. Stock solution
(100 ␮g/mL) of Pd(II) complexes were prepared in DMSO. Further
concentrations were prepared by serial dilution. Inoculum of the
overnight culture was prepared. In a series of tubes, 1 mL each of
Pd(II) complex solution with different concentrations was taken
and 0.4 mL of the inoculum was added to each tube. Further 3.5 mL
of the sterile water was added to each of the test tubes. These test
tubes were incubated for 18 h and observed for the presence of
turbidity. The absorbance of the suspension of the inoculum was
observed with spectrophotometer at 555 nm. The end result of the
test was the minimum concentration of antimicrobial agent (test
materials) which gave a clear solution, i.e., no visual growth [29,30].
Corrected % mortality
% mortality observed − % mortality in control × 100
=
100 − % mortality in control
4.5. Pesticidal activity
Fifth instar larva of Corcyra cephalonica were obtained from
stock culture maintained at the storage section of Division of Ento-
mology, Durgapura Agricultural Research Institute, Jaipur. Insects
were reared on wheat grain at 27 1 ◦C and 70% relative humid-
ity. Glass jars containing 500 g of wheat cereals were labelled to
indicate the date of introduction of adults and new emergence. At
alternate day larva were shifted to fresh jars so that successive rear-
ing jars can be maintained and insects of known age can be obtained
regularly. Pesticidal activity of the synthesized compounds was
tested by Immersion method. All the synthetic compounds were
5. Biological results and discussion
In the present study, the ligands and their palladium (II) macro-
cyclic complexes were evaluated for their antimicrobial activity
against two bacteria, Escherichia coli (ATCC25922) and Bacillus sub-
tilis (ATCC6633) and two fungi, Fusarium oxysporum (ATCC7808)
and Rhizopus nigricans (ATCC6227b). The results are summarized
in Tables 6 and 7. The results were compared with those of the
standard drug Streptomycin for bacteria and Bavistin for fungi. All

I. Masih, N. Fahmi / Spectrochimica Acta Part A 79 (2011) 940–947
947
Table 9
complexes showed promising antibacterial and antifungal activi-
ties but compound [Pd(C40H27N4Cl)]Cl2 and [Pd(C40H26N4Cl2)]Cl2
showed highest activity against bacterial strain E. coli ATCC25922,
B. subtilis ATCC6633 (MIC = 25 ␮g/mL) and fungal strain F. oxyspo-
rum ATCC7808 (MIC = 3.125 ␮g/mL). The enhanced activity of the
macrocyclic complexes than the parent ligands has been explained
on the basis of chelation theory. The newly synthesized complexes
exhibited considerable pesticidal activity however, compound
[Pd(C40H26N4Cl2)]Cl2] was found to be highly effective as a pes-
ticide with LC50 160 mg L−1 against Corcyra cephalonica.
Pesticidal activity of the ligands and their complexes.
Compound
LC50
ꢃ2
Corrected mortality (%)
C34H23N2O2Cl
C34H23N2O2F
[Pd(C40H26N4ClF)]Cl2
[Pd(C40H27N4Cl)]Cl2
[Pd(C40H26N4Cl2)]Cl2
[Pd(C40H27N4F)]Cl2
[Pd(C40H26N4F2)]Cl2
Control
410
840
200
190
160
405
170
–
0.274
0.431
0.537
0.694
0.160
0.48
55.55
50
61.11
66.66
77.77
66.66
72.22
–
0.282
1.142
lc = lethal concentration.
2 = chi square.
Acknowledgement
ꢃ
The authors are grateful to UGC, New Delhi for financial assis-
tance through grant no: 36-1/2008 (RAJ) (SR).
the ligands and their respective Pd(II) complexes were found to be
sensitive against all the fungal and bacterial strains. The antimi-
crobial screening data indicate that the metal complexes are more
potent antimicrobial agents than the free ligands.
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We describe the synthesis, characterization and biological activ-
ity of Pd(II) macrocyclic complexes. The structural properties of
Pd(II) macrocyclic complexes have been compared with several
related complexes in Table 5. On the basis of magnetic, analytical
and spectral data a square planar geometry has been proposed for
the Pd(II) macrocyclic complexes. The electrochemical properties
of metal complexes revealed the irreversible two electron transfer
redox process. The antimicrobial activity results indicated that the