Palladium(II) complexes of 5-substituted isatin thiosemicarbazones: Synthesis, spectroscopic characterization, biological evaluation and in silico docking studies

Article abstract of DOI:10.1080/00397911.2018.1546400

Substituted heterocyclic (isatin) appended thiosemicarbazone ligands (L1–L3) are synthesized by condensation of substituted isatin molecule with N(4)-phenyl-3-thiosemicarbazide in good yields. The palladium(II) complexes are synthesized from ligands (L1–L

Full text of DOI:10.1080/00397911.2018.1546400

Synthetic Communications
An International Journal for Rapid Communication of Synthetic Organic
Chemistry
ISSN: 0039-7911 (Print) 1532-2432 (Online) Journal homepage: https://www.tandfonline.com/loi/lsyc20
Palladium(II) complexes of 5-substituted isatin
thiosemicarbazones: Synthesis, spectroscopic
characterization, biological evaluation and in silico
docking studies
Gandham Munikumari, Ramaiah Konakanchi, Venkata Bharat Nishtala,
Gondru Ramesh, Laxma Reddy Kotha, K. B. Chandrasekhar & Chennuru
Ramachandraiah
To cite this article: Gandham Munikumari, Ramaiah Konakanchi, Venkata Bharat Nishtala,
Gondru Ramesh, Laxma Reddy Kotha, K. B. Chandrasekhar & Chennuru Ramachandraiah (2019)
Palladium(II) complexes of 5-substituted isatin thiosemicarbazones: Synthesis, spectroscopic
characterization, biological evaluation and inꢀsilico docking studies, Synthetic Communications,
49:1, 146-158, DOI: 10.1080/00397911.2018.1546400
To link to this article: https://doi.org/10.1080/00397911.2018.1546400
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SYNTHETIC COMMUNICATIONSV
2019, VOL. 49, NO. 1, 146–158
https://doi.org/10.1080/00397911.2018.1546400
Palladium(II) complexes of 5-substituted isatin
thiosemicarbazones: Synthesis, spectroscopic characterization,
biological evaluation and in silico docking studies
a
b
b
ꢀ
ꢀ
Gandham Munikumari , Ramaiah Konakanchi , Venkata Bharat Nishtala ,
Gondru Rameshb, Laxma Reddy Kothab, K. B. Chandrasekharc, and Chennuru
Ramachandraiaha
aDepartment of Chemistry, Sreekalahasteeswara Institute of Technology (SKIT), Srikalahasti, AP, India;
c
bDepartment of Chemistry, National Institute of Technology, Warangal, TS, India; Department of
Chemistry, Jawaharlal Nehru Technological University, Ananthapur, AP, India
ABSTRACT
ARTICLE HISTORY
Received 10 July 2018
Substituted heterocyclic (isatin) appended thiosemicarbazone ligands
(L1–L3) are synthesized by condensation of substituted isatin molecule
with N(4)-phenyl-3-thiosemicarbazide in good yields. The palladium(II)
complexes are synthesized from ligands (L1–L3) and PdCl2, with a general
formula [PdCl(X-C15H10N4OS)] where X ¼ 5-chloro (1), 5-bromo (2), and 5-
nitro (3). Both analytical and spectroscopic methods have been used for
the analysis and characterization of the synthesized compounds. The anti-
microbial activity results observed that complexes, 1 and 2 have registered
potent antibacterial activity against B. subtilis and K. pneumoniae and also
complex 2 has shown good antifungal activity against the micro organ-
isms. The antioxidant activity analysis revealed that the complex 3 showed
significant activity with IC50 values 7.24 0.09 mM. Moreover, the in vitro
antiproliferative activity results suggested that complex 3 exhibited high
activity against HeLa cell line compared with the standard with the IC50
value 16.52 1.08 mM. The docking results correlate well.
KEYWORDS
Antimicrobial; antioxidant
activity; antiproliferative
activity; heterocyclic
thiosemicarbazones;
Pd(II) complexes
GRAPHICAL ABSTRACT
ꢀ
CONTACT Chennuru Ramachandraiah
Sreekalahasteeswara Institute of Technology (SKIT), Skit Road, Srikalahasti, AP 517640, India.
cramachandraiahchem@gmail.com
Department of Chemistry,
ꢀ
The authors have Equal contribution in this work.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lsyc.
Supplemental data for this article can be accessed on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

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Introduction
Cisplatin is one of the most potent antitumor drugs, accessible for the therapeutic
management of solid tumors, such as germ cell tumors, ovarian, lung, head, neck, and
bladder cancers.[1,2] Bioinorganic chemistry provides surplus opportunities for the
synthesis of pharmaceutical drugs that are not accessible to organic compounds.[3–6]
Cisplatin, stilboestro, fulvestrant, carboplatin, goserelin, and oxaliplatin are some of
the metal-based drugs which show significant antitumor activity and have been widely
used in clinics.[7] However, these drugs have some limitations like drug resistance
over a period of time and adverse side effects.[8–11] Since, the origin and development
of the cytotoxic activity of cisplatin, several metal complexes have been investigated
for therapeutic activity.[12,13] The chemistry of the transition metal complexes of thio-
semicarbazones has become an interesting research field owing to their extensive
pharmacological significance that provides an assorted array of compounds with vari-
ous activities.[14–22] Among the transition metal complexes, Pd(II) complexes are
extremely appealing applicants because of their similarity to Pt(II) complexes in
coordination geometry and complex-forming processes,[23] which makes them a good
alternative for metal-based drugs. Palladium complexes show about 104 to 105 times
greater reactivity, though their structural and equilibrium behaviors are extremely
comparable to those of Platinum(II) complexes.[24] The similar coordination nature of
Pt(II) and Pd(II) also seconds the fact that palladium complexes can also exhibit anti-
cancer properties.[25] Thiosemicarbazone derivatives of glucosyl and chitosan have sig-
nificant antioxidant and oxygen free-radical scavenging activities. Because the –NH
and C = S groups in the thiosemicarbazone react with free radicals, thereby increasing
the antioxidant activity of these compounds.[26,27] Isatin is an interesting compound
and its skeleton, present in the structure of natural compounds, has been inaccessible
from the aquatic organisms with the high antifouling activity against fouling bac-
teria.[28–31] A number of palladium(II) thiosemicarbazone complexes have been syn-
thesized and examined for their potential as antitumor agents.[32] Synthesis and
characterization of a Pd(II) complexes of phenanthrenequinone thiosemicarbazone
and its cytotoxic property in MCF-7 (breast cancer) and normal cells have been
reported.[33] In the recent past, Ashok N. P. et al. have reported the synthesis and
antimicrobial properties of Pd(II) complexes of thiosemicarbazones derived from 5-
bromo isatin.[34] Amna Qasem Ali et al. have reported synthesis, characterization and
in vitro anticancer, DNA binding and cleavage activity of Pd(II) complexes based on
isatin thiosemicarbazone derivatives which clearly revealed the anticancer potency of
the compounds against the human colorectal carcinoma cell line HCT116.[24]
Muralisankar et al. have synthesized SNO pincer type palladium(II) complexes with
N–substituted isatin thiosemicarbazone ligands and investigated their DNA cleavage,
protein binding and in vitro cytotoxic properties. They found that the complexes pos-
sess significant in vitro antiproliferative activity against MCF-7 and A549 cancer cell
lines.[35] All these reports prompted us to further investigate and improve the bio-
logical properties complexes with isatin based thiosemicarbazones containing Pd(II) as
its central metal ion.
In the present work, we have demonstrated the synthesis of substituted (5-chloro/
bromo/nitro) isatin thiosemicarbazones (L1–L3) and their respective palladium(II)

148
G. MUNIKUMARI ET AL.
HN
H
N
O
H
N
H
N
N
Ethanol, 70 oC
AcOH, 5 h
S
X
X
H2N
O
S
O
N
H
N
H
X = Cl (L1), Br (L2) or NO2 (L3)
Scheme 1. Synthetic route of isatin based thiosemicarbazones ligands
H
N
S
N
X
X
PdCl2, Stirring
Acetonitrile, 6 h
N
S
N
N
H
N
H
Pd
Cl
O
N
H
O
N
H
X = Cl (1), Br (2) or NO2 (3)
Scheme 2. Synthetic route of pincer palladium(II) complexes
complexes (1–3). Further, the compounds were also thoroughly evaluated for their anti-
microbial, antioxidant and in vitro antiproliferative activities.
Results and discussion
The isatin based thiosemicarbazone ligands (L1–L3) were synthesized by the condensa-
tion between substituted isatin and 4-phenyl thiosemicarbazide in the presence of acetic
acid under reflux condition (Scheme 1). The corresponding palladium(II) complexes
(1-3) were obtained in good yields from the reaction of Pd(II) chloride with appropri-
ate thiosemicarbazone ligands in acetonitrile with stirring for 6 h (Scheme 2) at room
temperature. The characterization of the ligands and complexes was achieved by the
aid of elemental analysis presented in Table 1 and various spectroscopic (UV-Visible,
1
FT-IR, H and 13C{1H} NMR) tools. The ligands and complexes were soluble in DMF
and DMSO and partially soluble in methanol, ethanol, chloroform, benzene, and
dichloromethane.
Spectral characterization
The UV-Visible spectra of the synthesized compounds (ligands and its complexes) are
shown in Figure S1 (Supplementary information) and were recorded from 800–200 nm
using DMF as solvent at room temperature. Two absorption bands with varying inten-
sities can be observed in the ligands. The absorption bands at 273–257 and 370–366 nm
[35]
ꢀ
ꢀ
assigned to p! p and n!p transitions, respectively.
In the spectra of Pd(II) com-
plexes showed three prominent bands. Low-intensity broad bands around 268–267 nm
ꢀ
and 370–366 nm which assigned to p!p and n!p transitions. In addition, the band
at 424–412 nm can be assigned to ligand-to-metal charge transfer (LMCT) transitions
from sulfur to palladium ion. The S!M (LMCT) bands are relatively common in

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Table 1. Analytical and physical properties of the ligands (L1–L3) and their complexes (1–3).
Elemental analyses Calculated (Found)
Molecular
formula
Formula
weight
Colour
(Yield %)
Melting
point (ꢂC)
C
N
H
S
C15H11N4OSCl
(L1)
C15H11N4OSBr
(L2)
C15H11N5O3S
(L3)
C15H10Cl2N4OP-
dS (1)
C15H10BrClN4O-
PdS (2)
C15H10N5O3ClP-
dS (3)
330.79
375.24
341.24
471.66
516.11
482.21
Yellow (90)
310-312
280-282
268-270
308-310
320-322
326-328
54.46 (54.53) 16.94 (16.83) 3.35 (3.25) 9.69 (9.56)
48.01 (48.11) 14.93 (14.83) 2.95 (2.85) 8.55 (8.50)
52.78 (52.68) 20.52 (20.42) 3.25 (3.20) 9.39 (9.30)
38.20 (38.28) 11.88 (11.80) 2.14 (2.10) 6.80 (6.75)
34.91 (34.81) 10.86 (10.80) 1.95 (1.90) 6.21 (6.18)
37.36 (37.30) 14.52 (14.48) 2.09 (2.15) 6.65 (6.60)
Yellow
orange (92)
Yellow (90)
Dark
brown (90)
Reddish
brown (92)
Brown (85)
Table 2. The important IR frequencies (in cm–1) of ligands (L1–L3) and their complexes (1–3).
Compound
V(N – H)
V(H – N–C ¼ S)
V(C ¼ N)
V(C ¼ O)
V(C ¼ S)
L1
L2
L3
1
2
3
3406, 3330
3440, 3243
3437, 3330
3405, 3374
3438, 3318
3431, 3307
3230
3170
3239
–
1537
1559
1564
1501
1505
1521
1700
1690
1692
1633
1648
1639
1154
1152
1218
1107
1114
1172
–
–
electronic spectra of complexes of thiosemicarbazones,[36–40] which clearly indicated the
formation of palladium(II) complexes. The important FT-IR spectra of the compounds
are presented in Table 2. The ligands (L1–L3) showed a broadband in the range
3440–3300 cmꢁ1, which was due to the isatin and terminal NH group stretching fre-
quency, respectively. In the spectra of the complexes (1–3), the NH band stretching was
unaltered. The thiocarbonyl attached NH stretching frequency band of the ligand was
exhibited at 3243–3230 cmꢁ1 and the stretching frequency of carbonyl (C = O), imine
(C = N), and thiocarbonyl (C = S) were observed in the region 1700–1690 cmꢁ1
,
1564–1537 cmꢁ1, and 1218–1152 cmꢁ1, respectively. After complexation, the thiocar-
bonyl attached NH band was disappeared while the carbonyl (C = O), imine (C = N)
and thiocarbonyl (C = S) bands were decreased (1648–1633 cmꢁ1, 1521–1501 cmꢁ1
,
and 1172–1107 cmꢁ1) which clearly suggested that the coordination of ligand through
carbonyl oxygen (neutral), imine nitrogen (neutral), and thiocarbonyl sulfur (anion)
donor atoms with Pd(II) ion.
1H NMR spectra of the ligands, the thiocarbonyl, isatin attached NH and terminal
N–H protons appeared in the regions 11.50–12.62 ppm, 11.36–11.87 ppm, and
10.91–11.11 ppm, respectively. In the Pd(II) complexes spectra, the thiocarbonyl
attached N–H proton signal disappeared, which clearly suggested the coordination of
the ligand in the monobasic fashion after enolization and other two NH (isatin and ter-
minal attached) protons observed at 11.33–11.87 ppm. The signal aromatic protons in
the ligands and complexes were observed around 6.96–8.72 ppm and 6.61–9.31 ppm,
respectively. 13C{1H} NMR spectrum of the ligands appeared resonances due to C = S,
C = O and C = N carbons in the regions 176.54–176.93 ppm, 162.95–163.68 ppm, and
147.50–149.66 ppm, whereas same carbon signals in the complexes spectra appeared

150
G. MUNIKUMARI ET AL.
Table 3. MIC values of antibacterial activity of synthesized ligands (L1–L3) and their corresponding complexes (1–3)
presented in (lg/mL).
Compound
B. subtilis
S. aureus
E. coli
K. pneumoniae
L1
L2
L3
1
2
3
>100
>100
50
>100
5.6785
50
>100
>100
>100
>100
25
25
12.5
>100
>100
>100
>100
50
>100
12.5
25
>100
>100
6.1745
9.3751
25
Streptomycin
2.128
2.128
around 174.30–180.12 ppm, 163.42–164.14 ppm, and 144.18–147.45 ppm, respectively.
The chemical shift of other protons and carbons was observed in the expected range.
Biological evaluation
Antibacterial activity
The antibacterial activity of the synthesized compounds was carried out against
selected bacterial strains such as two gram-positive (Bacillus subtilis and
Staphylococcus aureus) and two gram-negative (Escherichia coli, Klebsiella pneumoniae)
bacteria by the disc diffusion method.[41,42] Streptomycin was used as a positive con-
trol. Experiments for each condition were performed in triplicate. The results were
showed in terms of the minimum inhibitory concentration (MIC) and expressed in
lg/ml, and the average values were depicted in Table 3. The results revealed that the
complex 1 against K. pneumoniae (MIC: 6.1745 lg/mL) and complex 2 against B. sub-
tilis (MIC: 5.6785 lg/mL) have shown good inhibition, respectively against the strains
compared to the reference drug. And also complex 2 has shown moderate activity
against K. pneumoniae (MIC: 9.3751 lg/mL) remaining complexes showed poor activ-
ity against the microorganisms. In conclusion, the ligands exhibited poor activity
against all the four strains although good activity reported by complexes 1 and 2
because may be due to the presence of chloro and bromo substituted thiosemicarba-
zone ligands coordinated to palladium.
Antifungal activity
The antifungal activity of the free ligands (L1-L3) and their corresponding complexes
(1–3) was tested against the strains Pencillium notatum and Aspergillus niger. The anti-
fungal drug Ketoconazole was chosen as a reference drug. The results of the synthesized
compounds in MIC are shown in Table 4. From the results, the complex 2 has regis-
tered good activity against both the strains Pencillium notatum and Aspergillus niger
with MIC values of 10.46 lg/mL and 10.58 lg/mL, respectively. And also complex 3
exhibits good activity against Aspergillus niger with MIC value 11.87 lg/mL. Remaining
compounds showed moderate to poor activity against the fungal strains. In conclusion,
compared to the metal complexes, ligands have shown lesser activity against
the organisms.

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Table 4. MIC values of antifungal activity of synthesized ligands (L1–L3) and their corresponding complexes (1–3)
presented in (lg/mL).
Compound
Pencillium notatum
Asperegillus niger
L1
L2
L3
1
2
3
18.68
17.44
25
50
25
>100
>100
10.58
11.87
4.25
50
10.46
18.46
4.25
Ketoconazole
Table 5. IC50 (mM) values of DPPH scavenging activity of ligands (L1–L3) and their corresponding complexes (1–3).
Compound
IC50 (mM)
L1
L2
L3
1
2
3
30.58 0.35
24.46 1.04
31.47 0.73
17.29 0.22
23.08 0.58
7.24 0.09
3.25 0.68
Ascorbic acid
35
30
25
20
15
10
5
0
L1
L2
L3
1
2
3
Ascorbic
acid
Figure 1. Scavenging activity of the ligands and its complexes (1-3).
Antioxidant activity
The scavenging activity of the ligands and their palladium(II) complexes results are pre-
sented in Table 5 and Figure 1. The Figure shows the antioxidant potential of the syn-
thesized compounds in comparison with the standard Ascorbic acid. Among the free
ligands and their palladium complexes, the complex 3 is found to be a most potent
antioxidant with IC50 value of 7.24
0.09 mM compared to standard ascorbic acid.
Complex 1 has shown moderate activity with IC50 value of 17.29 0.22 mM. The mech-
anism of action of these complexes on neutralizing the free DPPH radical is yet to be
established. Based on the IC50 values the order of activity is 3 > 1 >2>L2>L1>L3.
In vitro antiproliferative activity
In order to understand the in vitro antiproliferative activity of the compounds, an MTT
assay (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)[43,44] was carried

152
G. MUNIKUMARI ET AL.
Figure 2. Survival curves of (a) COLO-205, (b) HeLa, and (c) MCF-7 of the compounds.
Table 6. IC50 (mM) values of in vitro antiproliferative activity of the compounds (lM/mL).
Compound
COLO-205
HeLa
MCF-7
HEK 293
L1
L2
L3
1
2
3
58.14 0.6
46.10 1.2
70.72 1.3
31.69 0.69
46.65 1.1
21.83 1.85
3.72 0.3
51.40 1.3
45.60 0.8
67.20 1.9
45.72 1.7
67.17 1.6
16.52 1.08
4.21 0.1
49.12 1.4
33.10 1.7
74.90 0.2
28.25 1.2
38.30 1.0
19.30 1.0
4.36 0.1
ND
31.45 1.6
ND
ND
56.82 0.32
33.20 1.7
ND
Cisplatin
ND: Not determined.
out by using cisplatin as a positive control. The relation between the surviving fraction
and drug concentration was plotted to obtain the survival curves for MCF-7, HeLa and
IMR-32 cancer cell lines as shown in Figure 2. The results of the synthesized com-
pounds are summarized in Table 6. From the Table, it was observed that the complex 3
is unmistakable influences on HeLa and MCF-7 cancer cell lines with the IC50 values of
16.52 1.08 lM and 19.30 1.0 lM, respectively. The complex 1 showed moderate
activity with IC50 values of 28.25 1.2 lM against MCF-7. The ligand L2 and complex
2 exhibits similar IC50 values [46.10 1.2 lM and 46.65 1.1 lM, respectively] against
COLO-205 cell line, whereas the L3 and 2 exhibits similar IC50 values [67.20 1.9 lM
and 67.17
1.6 lM, respectively] against HeLa cell line. The remaining compounds

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Table 7. Binding energy, bond length, hydrogen bonds, and residues involved in hydrogen bonding of ligands and
their corresponding Pd(II) complexes inhibitors against EGFR protein receptor.
Binding
energy (kcal/mol)
No. of hydrogen
bonds
Residues involved
in hydrogen bonding
Compound
Bond length (Å)
L1
ꢁ5.77
ꢁ6.60
3
ARG817
ASP813
ASN818
ARG817
ASN818
ASP813
LYS721
LYS721
ASP813
ASP831
ASP813
ARG817
1.64
1.95
2.41
1.97
2.05
2.12
2.61 3.03
1.86
2.72
3.33
2.89
2.08, 2.36
L2
L3
5
ꢁ5.16
3
1
3
ꢁ7.05
ꢁ8.08
1
2
exhibited poor activity with the IC50 values ranging from 31.69 0.69 mM to 74.90
0.2mM against the four cancer cell lines.
In silico molecular docking studies
The main aim of this work was to examine the plausible binding modes and
molecular interaction mechanism of ligands (L1–L3) and complexes (1–3) with tar-
get epidermal growth factor (EGFR) protein receptor through the molecular dock-
ing studies. The EGFR protein is an attractive target for various cancer inhibitors
because it plays a prominent role in the cancer disease. Mutations of EGFR leads to
several types of cancer disease like anal cancers, squamous-cell carcinoma of the
lung and epithelial tumors of the head and neck. The molecular docking studies
were carried out with ligands and metal complexes on the EGFR protein receptor.
The Crystal structure of EGFR protein (PDB ID: 4hjo) was retrieved from RSC pro-
tein data bank.
The ligands and their metal complexes strongly bind to epidermal growth factor
protein receptor, which was inferred by their least binding energies of ꢁ5.77,
ꢁ6.60, ꢁ5.16, ꢁ7.05 and ꢁ8.08 kcal/mol, respectively. The metal complexes exhib-
ited effective interactions with the protein receptor when compared to the corre-
sponding ligands. The docking results were well correlated with the in vitro
antiproliferative activity results as shown in Table 7. The assessment of molecular
docking studies of ligands and their corresponding complexes unveil that, several
hydrogen bond interactions and hydrophobic interactions existed in between the
target molecules and EGFR protein receptor. Figure 3 shows the best docking con-
formations of ligands and their corresponding metal complexes. Among all the
ligands, the ligand L2 exhibited strong interactions with the selected protein recep-
tor which was unambiguous from its minimum binding energy –6.60 kcal/mol and
five hydrogen bonds were observed with the amino acid residues ARG817, ASN818,
ASP813 and LYS721 having bond lengths 1.97 Å, 2.05 Å, 2.12 Å, 2.61 Å and 3.03 Å.
among the complexes, the complex 3 interacts strongly with the EGFR protein
which was inferred by its minimum binding energy –8.08 kcal/mol and formed two
hydrogen bonds with the amino acid residues ARG817 having bond lengths 2.08 Å,
2.36 Å.

154
G. MUNIKUMARI ET AL.
Figure 3. Docking interactions of (a) ligand L1, (b) L2, (c) L3, (d) complex 1, (e) complex 3 to the
binding sites of target protein EGFR (PDB ID: 4hjo).
Conclusion
In the present paper, the ligands and their corresponding Palladium complexes have
been synthesized and characterized. The compounds were also examined for their anti-
microbial, antioxidant, in vitro antiproliferative activities and in silico docking studies
against EGFR protein receptor. The molecular structures of the complexes were con-
firmed by using various spectroscopic (UV-Visible, FT-IR, and NMR) and analytical
techniques. Based on the spectral data the complexes (1–3) may be tentatively proposed
as square planar geometry around Pd. In the biological applications, the complex 2 has
shown good antimicrobial activity compared to Streptomycin and Ketoconazole stand-
ard drugs. The compounds were investigated to their antioxidant activity, the results
showed that the complex 3 displayed excellent antioxidant agent with the IC50 values of
7.24 0.09 mM, in comparison with the standard Ascorbic acid. The in vitro antiproli-
ferative activity results revealed that complex 3 exhibited potent activity against HeLa

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and MCF-7 with the IC50 values of 16.52 1.08 mM and 19.30 1.0 mM, respectively.
Moreover, the molecular docking studies results show that the complex 3 gets minimum
binding energies of ꢁ8.08 kcal molꢁ1 with EGFR target receptor. Importantly, com-
plexes having the lowest binding energies are also displaying the highest cytotoxicity
against the tested human cancer cell lines.
Experimental
Synthesis of isatin based thiosemicarbazone ligands (L1–L3)
The ligands (L1–L3) are prepared by using the standard procedure.[45] Equimolar
(0.001 mol) quantities of 4-phenyl-3-thiosemicarbazide with the appropriately substi-
tuted isatin in ethanol (20 mL) and 0.5 mL of acetic acid were added. The contents
were condensed for 5 h. The colored products were filtered, washed with cold ethanol
and dried in vacuo.
Synthesis of pincer Pd(II) complexes (1–3)
The acetonitrile solution of PdCl2 (0.001 mol) was added into an appropriately substi-
tuted isatin thiosemicarbazone ligands (0.001 mol) in acetonitrile. The reaction mixture
was stirred for 6 h at room temperature, and then the precipitate formed was filtered
and washed with acetonitrile and dried in vacuo.
Acknowledgments
One of the author GM thanks Dr. R. Karvembu and Dr. J. Haribabu, National Institute of
Technology, Tiruchirappalli for helping with the preparation of compounds, working place, con-
tinuous support, and encouragement. RK thanks the MHRD, Govt. of India for providing Senior
Research Fellowship.
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