Synthesis, characterization, cytotoxicity and antimicrobial studies on bis(N-furfuryl-N-(2-phenylethyl)dithiocarbamato-S,S')zinc(II) and its nitrogen donor adducts

Article abstract of DOI:10.1016/j.ejmech.2012.12.047

[Zn(fpedtc)₂] (1), [Zn(fpedtc)₂(py)] (2), [Zn(fpedtc)₂(1,10-phen)] (3) and [Zn(fpedtc)₂(2,2′- bipy)] (4) (where fpedtc = N-furfuryl-N-(2-phenylethyl)dithiocarbamate, py = pyridine, 1,10-phen = 1,10-phenanthrolin

Full text of DOI:10.1016/j.ejmech.2012.12.047

European Journal of Medicinal Chemistry 62 (2013) 139e147
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European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, characterization, cytotoxicity and antimicrobial studies
on bis(N-furfuryl-N-(2-phenylethyl)dithiocarbamato-S,S0)zinc(II)
and its nitrogen donor adducts
*
Palanisamy Jamuna Rani, Subbiah Thirumaran
Department of Chemistry, Annamalai University, Annamalainagar 608 002, Tamil Nadu, India
a r t i c l e i n f o
a b s t r a c t
[Zn(fpedtc)2] (1), [Zn(fpedtc)2(py)] (2), [Zn(fpedtc)2(1,10-phen)] (3) and [Zn(fpedtc)2(2,20-bipy)] (4) (where
fpedtc ¼ N-furfuryl-N-(2-phenylethyl)dithiocarbamate, py ¼ pyridine, 1,10-phen ¼ 1,10-phenanthroline
and 2,20-bipy ¼ 2,20-bipyridine) were synthesized. Characterization of the complexes were achieved by
IR and NMR (1H and 13C) spectra and in addition, for 2 and 3, by X-ray crystallography. Single crystal X-ray
structural analysis of 2 and 3 showed that complex 2 is almost half way between trigonal bipyramidal and
square pyramidal and complex 3 has a distorted octahedral geometry. ZneN distances in 2 is shorter than
that found in a six coordinate complex 3 due to the change in coordination number. These complexes were
also screened for in vitro antibacterial and antifungal activities and significant activities have been found.
In vitro cytotoxic activity of all the synthesized complexes was evaluated on HeLa cell line. Complex 1 ex-
Article history:
Received 28 July 2012
Received in revised form
2 December 2012
Accepted 31 December 2012
Available online 7 January 2013
Keywords:
Dithiocarbamate
Nitrogen donor ligands
Zinc(II)
X-ray structure
HeLa cell line
hibits maximum inhibitory effect at a concentration of 40
Ó 2013 Elsevier Masson SAS. All rights reserved.
m
g mLꢀ1 on HeLa cell line.
Antimicrobial studies
1. Introduction
opening up new perspectives in anticancer research based on
metallopharmaceuticals [16]. Despite high nephrotoxicity, neuro-
toxicity and acquired drug resistance as major drawbacks, cisplatin
and its two analogs (carboplatin and oxaliplatin), are among the
most effective chemotherapeutic agents in clinical use to date [17].
Dithiocarbamates have been evaluated for their efficiency as in-
hibitors of cisplatin-induced nephrotoxicity [18]. In particular, di-
thiocarbamates selectively protects normal tissue without
inhibiting the antitumor effect [19,20]. The majority of the dithio-
carbamate [M(S2CNR1R2)n] complexes studied have simple R1 and
R2 groups such as methyl, ethyl and phenyl [21]. Only one structural
report has been made on furfuryl based dithiocarbamate complex
from our laboratory [22].
Dithiocarbamates have a wide range of applications in medicine,
industry and rubber vulcanization [1e4], and can serve as antiox-
idants for increasing the longevity and photo-stability of a variety of
polymers, oils and other materials [5]. Metal dithiocarbamate
complexes and their nitrogen donor adducts are useful precursors
for the synthesis metal sulfide nanoparticles [6,7].
Several dithiocarbamate salts and metal complexes of di-
thiocarbamates have been used as agrochemicals, mainly due to
their high efficiency in controlling plant fungal diseases and their
relatively low toxicity [8e13]. Cervical carcinoma significantly af-
fects women world wide, especially in developing countries [14].
Approximately, 500,000 cases of cervical cancer diagnosed per year
with nearly 40% of those resulting in death [15]. Although cancer
has existed as a disease since prehistoric time, it is still one of the
major causes of death in the world. To date, the most reliable way to
reduce or cure cancer is to remove and/or to block the fast pro-
liferating malignant tissues. The discovery of cisplatin
(cis-[Pt(NH3)2Cl2]), the first inorganic compound to block DNA
replication and cell division, has demonstrated that metal com-
plexes can play an important role in the treatment of cancer
To understand the influence of furfuryl based dithiocarbamate
and nitrogen donor ligands (py, 1,10-phen, 2,2-bipy) on biological
properties, we report results on cytotoxicity, antifungal and anti-
bacterial properties of complexes 1e4, as well as their IR and NMR
spectra. In addition, the crystal structures of 2 and 3 are described.
2. Results and discussion
2.1. Synthesis of complexes 1e4 and their characterization
Complexes 1e4 were prepared according to the synthetic pro-
cedure shown in Schemes 1 and 2. Furfuraldehyde was condensed
* Corresponding author. Tel.: þ91 9842897597.
E-mail address: sthirumaran@yahoo.com (S. Thirumaran).
0223-5234/$ e see front matter Ó 2013 Elsevier Masson SAS. All rights reserved.
http://dx.doi.org/10.1016/j.ejmech.2012.12.047

140
P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
reveals bands at 1600 and 1567 cmꢀ1. Other bands due to nitrogen
ligands are masked by those due to dithiocarbamate.
1H NMR spectrum of N-furfuryl-N-(2-phenylethyl)amine
shows a singlet at 3.68 ppm and two triplets at 2.72 and 2.79 ppm
due to methylene protons of furfuryl group and the ethylene unit
of 2-phenylethyl group, respectively; that shifted to lower field
being nitrogen bound. The signal of methylene protons (singlet) of
NeCH2 (furfuryl) appears in the region 4.95e5.12 ppm in all the
complexes 1e4. All the complexes showed two equal intensity
triplets in the aliphatic region 3.00e4.10 ppm associated with the
ethylene unit of 2-phenylethyl group; that shifted to lower field
being nitrogen bound. The nitrogen bound methylene proton
signals of complexes 1e4 are strongly deshielded compared to
those of free N-furfuryl-N-(2-phenylethyl)amine, which confirms
the formation of dithiocarbamate.
Scheme 1. Preparation of complex 1.
Complexes 1e4 show N13CS2 signals in the region 205.2e
207.1 ppm, indicating contribution of double bond character to
a formally single NeC bond in the dithiocarbamate. The N13CS2
chemical shift of dithiocarbamate is also affected by coordination of
nitrogen donor to metal. Additional coordination of nitrogen donors
to metal dithiocarbamates yields a decrease of nitrogenecarbon
partial double bond character and, as a result of that, the N13CS2
carbon of nitrogen donor adducts 2e4 are additionally deshielded
compared to parent complex 1.
with 2-phenylethylamine to form the imine. Sodium borohydride
reduction of imine in methanoledichloromethane afforded N-fur-
furyl-N-(2-phenylethyl)amine as yellow oil. Complex 1 was pre-
pared from amine in EtOH by reaction with carbon disulfide and
ZnSO4 in water. The reaction of complex 1 with nitrogen donor li-
gands (py, 1,10-phen, 2,20-bipy) yielded 2, 3 and 4. The complexes
are quite stable at ambient conditions. They are soluble in chloro-
form, dichloromethane and acetonitrile and insoluble in ethanol,
methanol and water.
IR spectroscopy has been used to understand the nature of co-
ordination mode (monodentate or bidentate) of dithiocarbamate
moiety. IR spectra of complexes 1 and 2 are given in Fig. 1. Based on
Bonati et al. criterion, the presence of only one characteristic band in
the region 1050e900 cmꢀ1, the nCeS mode, is due to bidentate co-
ordination of the dithiocarbamate group while a split band within
narrow range of 20 cmꢀ1 is indicative of the monodentate nature of
the dithiocarbamate group [23]. In the present study, the CeS
stretching vibrations are observed in the region 1017e1014 cmꢀ1
without any splitting, supporting the bidentate coordination of the
dithiocarbamate ligand. The dithiocarbamate compounds exhibit
another characteristic band in the region 1550e1450 cmꢀ1 assign-
able to the nCeN (thioureide) [24]. The infrared spectra of 1e4 show
nCeN (thioureide) bands in the region 1487e1462 cmꢀ1, indicating
the partial double bond character.
2.2. Structural studies on complexes 2 and 3
An ORTEP diagram of complex 2 is shown in Fig. 2. Complex 2
contains four discrete molecules per unit cell. The zinc atom in
complex 2 is five coordinated to four sulfur atoms from the di-
thiocarbamates and to one nitrogen atom from pyridine. The co-
ordination group around zinc is distorted trigonal bipyramid with
coplanar atoms Zn, N(pyridine), S(1) and S(1i) lying in the equa-
torial plane and S(2) and S(2i) occupying the axial positions. In
this complex, dithiocarbamate ligands are bound in a chelating
fashion that bridge equatorial and axial sites. The two dithio-
carbamate ligands in 2 coordinate in an anisobidentate fashion
ꢀ
[ZneS1 ¼ 2.3600(7) and ZneS2 ¼ 2.5621(6) A]. The CeS distances
are slightly asymmetric and the shorter ZneS1 bond is associated
with longer CeS distance. The structure of complex 2 is inter-
mediate between the tetragonal pyramid (TP) and trigonal
bipyramidal. For accurate description of the geometry, this com-
The thioureide nCeN bands of complexes follow the order
1 > 2 > 3 z 4. This indicates that the Ndþ/Cdꢀ double bond character
decreases with increasing coordination number [25]. The character-
istic band due to pyridine appears at 1604 cmꢀ1 in 2. The ring fre-
quencies associated with 1,10-phenanthroline and 2,20-bipyridine are
1600e1000 cmꢀ1 [26]. In this study 1,10-phenanthroline adduct 3
shows bands at 1584 and 1507 cmꢀ1 whereas 2,20-bipyridine adduct 4
plex is characterized by using the
tion suggested by Addison et al. [27]. From the
s
descriptor for five coordina-
values, the
s
coordination geometry is described as being 56% along the path-
way of distortion from square pyramid toward trigonal bipyramid.
ꢀ
The short thioureide CeN distance [1.339(3) A], indicates that the
p-electron density is delocalized over the S2CN moiety and this
bond has a significant double bond character. All the CeS bonds in
the present structure are of partial double bond character as
observed in other dithiocarbamate complexes [28].
The ORTEP diagram of complex 3 is shown in Fig. 3. Zinc is hex-
acoordinated by two nitrogen atoms from 1,10-phenanthroline and
four sulfur from the chelating dithiocarbamate groups. In this com-
plex, the zinc atom is situated at the center of a distorted tetragonal
bipyramidal arrangement with two sulfur atoms from
dithiocarbamate groups [S1, S3] and two nitrogen atoms from the
1,10-phenanthroline ligand [N3, N4] on the basal plane and the
two remaining sulfur atoms as vertices. The two bonds ZneS2 and
ZneS4 are relatively longer than others due to the steric influence
of the 1,10-phenanthroline ligand. The two SeZneS angles [S2eZne
S4 ¼ 170.54(2) and S1eZneS3 ¼ 101.93(2)ꢁ] correspond to trans and
cis octahedral values,ꢁrespectively. The N4eZneN3 angle observed in
ꢀ
the adduct is 75.18(7) . The short thioureide CeN distance [1.373(3) A]
Scheme 2. Preparation of complexes 2, 3 and 4.
indicates that the p-electron density is delocalized over the S2CN

P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
141
Fig. 1. IR spectra of complexes 1 and 2.
moiety and this bond has double bond character comparing well
2.3. Biological activity
with the adjacent typical single bonded NeC distance [C(16)e
ꢀ
N(3) ¼ 1.473(3) A]. The SeZneS bite angles in 3 are less compared
2.3.1. Antibacterial activity
to those observed in 2 due to the increased coordination around zinc.
Reduction in SeZneS bite angles has resulted in a change in ZneS
distances. No significant changes in CeS, NeC bond distances and
SeCeS angles are observed. The ZneN distance in 3 is longer than that
found in 2 due to the increased coordination number.
The disc diffusion assay was conducted to determine if the
tested compounds could inhibit the growth of bacteria. The anti-
bacterial activity of the complexes has been screened against
Escherichia coli, Salmonella typhi, Vibrio cholerae and Staphylococcus
aureus. The results are given in Table 1. Significant antibacterial

142
P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
Table 1
Antibacterial activity (diameter of inhibition zone (cm)) of complexes 1e4 against
four different bacterial pathogens.
Selected bacteria
Chloramphenicol Complex
Disc content
(mg/disc)
(100
m
g)
1
2
3
4
Escherichia coli
Salmonella typhi
Vibrio cholerae
1.9
0.9 1.0 0.5 0.9 100
1.0 1.5 1.0 1.5 400
0.8 0.8 0.7 0.9 100
1.2 1.3 1.1 1.5 400
0.8 1.2 0.5 1.7 100
1.4 1.4 0.8 1.9 400
2.0
2.0
Staphylococcus aureus 2.2
0.6 0.9
e
0.6 100
1.0 1.5 0.8 1.5 400
activity against M. gypseum and T. rubrum when compared with
other complexes. Complexes 2 and 4 also showed good activity
against T. rubrum. All the complexes revealed very less activity
against E. floccosum. Complex 4 exhibited more activity against
T. mentagrophyte.
Fig. 2. ORTEP diagram of 2 (hydrogen atoms have been omitted for clarity).
Complex 1 against M. gypseum and T. rubrum explored good
activities were observed when compared to a standard drug
Chloramphenicol. Complex 3 exhibits less activity against all the
tested bacteria. Complex 4 is more toxic for all the tested Gram
negative bacteria compared to other complexes 1e3. Data obtained
also indicate the increasing dosage level of complexes from 100 to
inhibitory activity (3.12 and 25
plexes did not show any inhibitory activity against E. floccosum even
at concentration of 50 g/mL. Complexes 3 and 4 revealed good
inhibitory effect against T. mentagrophyte with MIC value of
6.25 g/mL. The antifungal activity of dithiocarbamates may be
mg/mL, respectively). All the com-
m
m
400 mg/disc, the inhibitory effect slightly increased.
attributed to their ability to chelate with metal ions. When these
metal complexes penetrates lipid barriers in the fungal cell and
may be ultimate toxicant or alternatively, it may be converted into
free dithiocarbamate anions, which complexing with trace metals
and thus depriving the cell of the needed metal ion and therefore
causes death of fungal cell.
The minimum inhibitory concentrations are given in Table 2.
Complex 4 was found to be the most effective against the tested
Gram negative pathogenic strains of bacteria E. coli, S. typhi and
V. cholera with MIC values of 25, 25 and 3.12 mg/mL, respectively and
less active against the tested Gram positive pathogenic strain of
S. aureus. The antibacterial activity of 4 is more active than the other
complexes, suggesting 2,20-bipyridine assist the action of complex
against Gram negative bacteria possibly via enhanced membrane
transport into the cell or some other mode of action [29]. Complex 2
2.3.3. Cytotoxicity results
All the synthesized complexes 1e4 were examined for their
cytotoxic properties on HeLa cell line by means of MTT test that
allows us to evaluate the toxic effect of complexes on cellular
exhibited greater inhibitory action against S. aureus (25
mg/mL)
than other complexes.
mitochondrial metabolism. Cells were tested for 48
h with
increasing concentrations of tested compounds. Cytotoxicity re-
sults are given in Table 4. Microscopic images of control cancer cells
and apoptotic morphological changes in HeLa cell line treated with
complex 1e4 are shown in Fig. 4. The results clearly show con-
centration dependent inhibition of cancer cell by all the complexes.
Complex 1 exhibits a satisfactory inhibitory effect on cell prolifer-
ation. A maximum inhibitory effect of complex 1 is observed at
2.3.2. Antifungal activity
The antifungal activities of the complexes using Microsporum
gypseum, Trichophyton rubrum, Epidermophyton floccosum and Tri-
chophyton mentagrophyte were studied in vitro and results are
summarized in Table 3. The antifungal activity of the compounds as
compared with that of reference drug (Chloramphenicol) showed
significant activity. Complex 1 was found to exhibit maximum
a concentration of 40
m
g mLꢀ1. Complexes 2e4 showed lower
cytotoxic effect than complex 1. This is because the complex 1 exists
as four coordinated with distorted tetrahedral geometry which will
enhance the cytotoxic activity of complex 1. This is in consistent
with literature that species having the tetrahedral geometry are
more active [30].
3. Conclusion
New complexes 1e4 have been synthesized, and characterized
by elemental analysis and spectroscopic studies. Single crystal
X-ray structural analysis were carried out for 2 and 3. The ZneN
distance in 3 is longer than that found in 2 due to the increased
coordination around zinc. The antimicrobial activities of all com-
plexes were analyzed at the concentrations 100 and 400 m .
g mLꢀ1
All the complexes exhibit antibacterial activity against four bacte-
rial species. Complex 4 has greater activity than other tested
complexes and has almost equal activity against E. coli, S. typhi, V.
cholerae and S. aureus as compared with the Chloramphenicol.
These complexes were also screened for in vitro antifungal activity.
Complex 1 against M. gypseum and T. rubrum and complexes 1 and
Fig. 3. ORTEP diagram of 3 (hydrogen atoms have been omitted for clarity).

P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
143
Table 2
Antimicrobial activity (minimum inhibitory concentration (MIC) in
m
g/mL) of complexes 1e4.
Minimum inhibitory concentration (MIC) in g/mL
Bacterial strains
Complex
m
Fungal strains
E. coli
S. typhi
V. cholerae
S. aureus
M. gypseum
T. rubrum
E. floccosum
T. mentagrophyte
1
2
3
4
25
25
100
25
12.5
50
50
50
25
50
100
25
>200
100
3.12
3.12
25
>200
25
25
100
50
50
12.5
200
100
>200
200
6.25
50
12.5
100
3.12
6.25
12.5
6.25
6.25
3.12
Chloramphenicol
6.25
25
4 against T. mentagrophyte have been found to exhibit maximum
inhibitory effect. Complex 1 has potent in vitro cytotoxic against
HeLa cell line.
Evaporation of the organic layer gave N-furfuryl-N-(2-phenylethyl)
amine as a yellow oil.
1H NMR (400 MHz, CDCl3):
d
2.17 (b, 1H, NH), 2.72 (t, J ¼ 6.6 Hz,
2H, NeCH2eCH2), 2.79 (t, J ¼ 6.4 Hz, 2H, NeCH2eCH2), 3.68 (s, 2H,
NeCH2 (furfuryl)), 6.07e7.26 (aryleH, m, 5H (phenyl)). 13C NMR
4. Experimental
(100 MHz, CDCl3):
d 36.2 (NeCH2eCH2), 46.0 (NeCH2eCH2), 50.3
(NeCH2 (furfuryl)), 107.0, 110.2, 110.4, 126.3, 128.5, 128.8, 141.8,
142.0, 142.6, 153.8 (aryl carbon).
All reagents and solvents were commercially available high-
grade materials (Merck/sd Fine/Himedia) and used as received. IR
spectra were recorded on a Thermo Nicolet Avatar 330 FT-IR
spectrophotometer (range 400e4000 cmꢀ1) as KBr pellets. The
NMR spectra were recorded on Bruker 400/100 and 500/125 MHz
NMR spectrometers at room temperature in CDCl3, using TMS as
internal reference.
4.3. [Zn(fpedtc)2] (1)
N-Furfuryl-N-(2-phenylethyl)amine (0.87 g,
4 mmol) and
carbon disulfide (0.3 mL, 4 mmol) were dissolved in ethanol
(20 mL), and stirred for 30 min. ZnSO4$7H2O (0.58 g, 2 mmol) was
dissolved in 10 mL of water and added to the solution with constant
stirring. A white powder precipitated that was filtered and dried.
Yield: 80%. m.p. 140 ꢁC. IR (KBr, cmꢀ1): 1014 (nCeS), 1487 (nCeN),
2926 (nCeH(aliph.)), 3061 (nCeH(arom.)). 1H NMR (500 MHz, CDCl3):
4.1. X-ray crystallography
Diffraction data for 2 and 3 were recorded on an Bruker axs
kappa apex2CCD diffractometer using graphite monochromated
ꢀ
MoKa radiation (
l
¼ 0.71073 A) at ambient temperature. The
d
3.02 (t, J ¼ 8.0 Hz, 4H, NeCH2eCH2), 4.04 (t, J ¼ 8.0 Hz, 4H, Ne
structure was solved by SIR-92 [31] and refined by full matrix least
square with SHELXL-97 [32]. All the non-hydrogen atoms except
furyl ring in 2 were refined anisotropically and the hydrogen atoms
were refined isotropically. In 2, the furyl (C10eC13 and O1) ring was
disordered over two positions. Details of the crystal data and
structure refinement parameters for 2 and 3 are summarized in
Table 5. Selected bond lengths and angles are summarized in
Table 6.
CH2eCH2), 4.95 (s, 4H, NeCH2 (furfuryl)), 6.38 (dd, J ¼ 2.0, 3.5 Hz,
2H, H-4 (furyl)), 6.44 (d, J ¼ 3.0 Hz, 2H, H-3 (furyl)), 7.22e7.33 (m,
10H (phenyl)), 7.42 (d, J ¼ 2.0 Hz, 2H, H-5 (furyl)). 13C NMR
(125 MHz, CDCl3):
d 32.9 (NeCH2eCH2), 51.2 (NeCH2eCH2), 55.8
(NeCH2 (furfuryl)), 110.5, 110.8, 126.8, 128.8, 128.9, 137.9, 142.9,
148.2 (aryl carbon), 205.2 (CS2). Anal. Calc. for C28H28S4N2O2Zn (%):
C, 54.40; H, 4.56; N, 4.53. Found (%): C, 54.28; H, 4.48; N, 4.49.
4.4. [Zn(fpedtc)2(py)] (2)
4.2. Preparation of N-furfuryl-N-(2-phenylethyl)amine
The pyridine adduct was prepared by dissolving the complex 1
in warm pyridine. The yellow solution obtained was filtered and
kept for evaporation. After few days both powder and single
crystals separated out.
2-Phenylethylamine (0.6 mL, 4.6 mmol) and furfuraldehyde
(0.4 mL, 5.1 mmol) were dissolved in methanol (10 mL) and the
solution was stirred for 2 h at room temperature. The solvent was
removed by evaporation. The resulting yellow oil was dissolved in
methanoledichloromethane solvent mixture (1:1, 20 mL) and so-
dium borohydride (0.5 g, 13.8 mmol) was added slowly at 5 ꢁC. The
mixture was stirred at room temperature for 24 h. After evaporation
of the solvent, the resulting viscous liquid was washed with water
and dichloromethane was added in order to extract the product.
Yield: 60%. m.p. 110 ꢁC. IR (KBr, cmꢀ1): 1017 (nCeS), 1478 (nCeN),
1604 (py), 2936 (nCeH(aliph.)), 3074 (nCeH(arom.)). 1H NMR (500 MHz,
CDCl3):
d
3.02 (t, J ¼ 10.0 Hz, 4H, NeCH2eCH2), 4.07 (t, J ¼ 10.0 Hz,
4H, NeCH2eCH2), 5.06 (s, 4H, NeCH2 (furfuryl)), 6.36 (dd, J ¼ 2.5,
4.0 Hz, 2H, H-3 (furyl)), 6.43 (d, J ¼ 3.5 Hz, 2H, H-4 (furyl)), 7.40 (d,
J ¼ 3.5 Hz, 2H, H-5 (furyl)), 7.18e7.31 (m, 10H (phenyl)), 7.47 (t,
J ¼ 2.8 Hz, 2H, H-3 (py)), 7.88 (t, J ¼ 6.1 Hz, 1H, H-4 (py)), 9.01 (d,
J ¼ 6 Hz, 2H, H-2 (py)). 13C NMR (125 MHz, CDCl3):
d 32.8 (NeCH2e
Table 3
CH2), 51.2 (NeCH2eCH2), 55.8 (NeCH2 (furfuryl)), 110.0, 110.6,
Antifungal activity (diameter of inhibition zone (cm)) of complexes 1e4 against four
different fungal pathogens.
Selected fungi
Chloramphenicol Complex
Disc content
g/disc)
Table 4
(100
m
g)
(m
Anticancer effect of complexes 1e4 on HeLa cell line.
1
2
3
4
Microsporum gypseum
Trichophyton rubrum
1.6
1.5 0.5
e
1.0 100
Concentration of
complex (mg/mL)
Cell viability (%) of the complexes
1.9 0.8 1.2 1.2 400
0.8 0.5 0.7 0.6 100
1.2 1.2 0.8 1.2 400
1
2
3
4
1.9
2.0
10
20
30
40
50
13.3
13.3
13.3
6.7
91.6
85.4
81.2
75.0
66.6
95.8
93.7
85.4
79.1
66.6
91.6
89.5
85.4
75.0
70.8
Epidermophyton floccosum
0.4 0.5
e
0.4 100
0.8 0.9 0.6 0.6 400
0.7 0.8 0.4 1.5 100
1.3 1.3 1.3 1.6 400
Trichophyton mentagrophyte 2.2
6.7

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P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
Fig. 4. (a) Control cancer cells. Apoptotic morphological changes were observed in the cells treated with 50 mg/mL of complexes (b) 1 (c) 2 (d) 3 and (e) 4.
124.7, 126.5, 128.5, 128.8, 138.4, 142.5, 149.0, 149.4 (aryl carbon),
206.5 (CS2). Anal. Calc. for C33H33N3S4O2Zn (%): C, 56.84; H, 4.76; N,
6.02. Found (%): C, 56.69; H, 4.68; N, 5.96.
7.87 (b, 4H, H-3 (1,10-phen)), 7.94 (s, 2H, H-5 (1,10-phen)), 8.45 (d,
J ¼ 1.5 Hz, 2H, H-4 (1,10-phen)), 9.75 (d, J ¼ 4 Hz, 2H, H-2 (1,10-
phen)). 13C NMR (125 MHz, CDCl3):
d 32.8 (NeCH2eCH2), 51.3 (Ne
CH2eCH2), 55.7 (NeCH2 (furfuryl)), 109.4, 110.5, 124.7, 126.2, 126.6,
128.5,128.7,128.9,137.8,138.9,141.3,142.2,149.1,150.0 (aryl carbon),
207.1 (CS2). Anal. Calc. for C40H36N4S4O2Zn (%): C, 60.17; H, 4.54; N,
7.01. Found (%): C, 60.11; H, 4.47; N, 6.96.
4.5. [Zn(fpedtc)2(1,10-phen)] (3)
Adduct was prepared by adding
a hot solution of 1,10-
phenanthroline (2 mmol) in ethanol to a hot solution of complex
1 (1 mmol) in chloroform. The resulting solution was cooled and
then added with petroleum-ether (boiling range: 40e60 ꢁC).
Yellow precipitate of the adduct was separated out. Suitable sin-
gle crystals for X-ray structure analysis were obtained by repeated
crystallization from dichloromethaneebenzene solvent mixture.
Yield: 80%. m.p. 162 ꢁC. IR (KBr, cmꢀ1): 1014 (nCeS), 1462 (nCeN),
1507, 1584 (1,10-phen), 2928 (nCeH(aliph.)), 3063 (nCeH(arom.)). 1H
4.6. [Zn(fpedtc)2(2,20-bipy)] (4)
A method similar to that described for the synthesis of 3 was
adopted, however, 2,20-bipyridine (2 mmol) was used instead of
1,10-phenanthroline. Yellow precipitate of adduct was separated
out.
Yield: 70%. m.p. 158 ꢁC. IR (KBr, cmꢀ1): 1017 (nCeS), 1468 (nCeN),
1
NMR (500 MHz, CDCl3):
d
3.03 (t, J ¼ 8.0 Hz, 4H, NeCH2eCH2), 4.10 (t,
1567, 1600 (2,20-bipy), 2925 (nCeH(aliph.)), 3063 (nCeH(arom.)). H NMR
J ¼ 8.3 Hz, 4H, NeCH2eCH2), 5.12 (s, 4H, NeCH2 (furfuryl)), 6.33 (dd,
J ¼ 2.0, 3.5 Hz, 2H, H-4 (furyl)), 6.40 (d, J ¼ 3.0 Hz, 2H, H-3 (furyl)),
7.20e7.29 (m, 10H (phenyl)), 7.36 (d, J ¼ 2.0 Hz, 2H, H-5 (furfuryl)),
(400 MHz, CDCl3):
d
3.00 (t, J ¼ 8.0 Hz, 4H, NeCH2eCH2), 4.05 (t,
J ¼ 8.0 Hz, 4H, NeCH2eCH2), 5.01 (s, 4H, NeCH2 (furfuryl)), 6.35 (b, 2H,
H-4 (furyl)), 6.41 (d, J ¼ 2.8 Hz, 2H, H-3 (furyl)), 7.19e7.31 (m, 10H

P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
145
Table 5
Crystal data, data collection and refinement parameters for 2 and 3.
2
3
Empirical formula
FW
C33H33N3O2S4Zn
697.23
C40H36N4O2S4Zn
798.34
Temperature
Wavelength
Crystal system
Space group
Unit cell dimension
293(2) K
293(2) K
0.71073 A
Monoclinic
P21/n
ꢀ
ꢀ
0.71073 A
Monoclinic
C2
ꢀ
a (A)
32.6725(9)
8.4874(2)
6.0549(2)
15.5871(7)
14.2405(7)
17.0145(8)
97.1190(10)
0.919 mmꢀ1
1656
ꢀ
b (A)
ꢀ
c (A)
b
(ꢁ)
91.752(2)
Absorption coefficient
F(000)
1.014 mmꢀ1
724
Crystal size
q
0.25 ꢃ 0.20 ꢃ 0.15 mm
0.30 ꢃ 0.25 ꢃ 0.20 mm
Range (ꢁ)
1.25e27.50
1.87e29.52
Limiting indices
ꢀ42 ꢄ h ꢄ 42, ꢀ8 ꢄ k ꢄ 11, ꢀ7 ꢄ 1 ꢄ 7
9236/3253 [R(int) ¼ 0.0200]
Semi-empirical from equivalents
0.8627 and 0.7856
Full-matrix least-squares on F2
3253/39/210
ꢀ21 ꢄ h ꢄ 21, ꢀ19 ꢄ k ꢄ 19, ꢀ23 ꢄ 1 ꢄ 23
47,543/10,433 [R(int) ¼ 0.0393]
Semi-empirical from equivalents
0.8375 and 0.7700
Reflections collected/unique
Absorption correction
Max. and min. transmission
Refinement method
Full-matrix least-squares on F2
10,433/0/461
Data/restraints/parameters
Goodness-of-fit on F2
1.136
1.041
Final R indices [I > 2
R indices (all data)
Largest diff. peak and hole
s
(I)]
R1 ¼ 0.0275, wR2 ¼ 0.0771
R1 ¼ 0.0317, wR2 ¼ 0.0893
0.257 and ꢀ0.398 e Åꢀ3
R1 ¼ 0.0397, wR2 ¼ 0.0985
R1 ¼ 0.0790, wR2 ¼ 0.1249
0.424 and ꢀ0.301 e Åꢀ3
(phenyl)), 7.39 (b, 2H, H-5 (furyl)), 7.44 (t, J ¼ 1.8 Hz, 2H, H-4 (2,20-
bipy)), 7.91 (t, J ¼ 7.2 Hz, 2H, H-5 (2,20-bipy)), 8.29 (d, J ¼ 5.6 Hz, 2H, H-
6 (2,20-bipy)), 9.03 (b, 2H, H-3 (2,20-bipy)). 13C NMR (100 MHz, CDCl3):
method [33]. Seeded broth (broth containing microbial spores) was
prepared in NB from 24 h old bacterial cultures on nutrient agar
(Hi-media, India) at 37 ꢂ 1 ꢁC while fungal spores from 24 h to 7
days old Sabourauds agar slant cultures were suspended in SDB.
The bacterial suspension was adjusted with sterile saline to a con-
centration of 1 ꢃ104e105 CFU. The tested compounds and reference
drugs were prepared by two-fold serial dilution to obtain the
d
32.9 (NeCH2eCH2), 51.3 (NeCH2eCH2), 55.8 (NeCH2 (furfuryl)),
110.0, 110.7, 120.9, 124.6, 126.6, 128.6, 128.9, 137.9, 138.4, 142.6, 149.0,
149.3 (aryl carbon), 206.5 (CS2). Anal. Calc. for C38H36N4S4O2Zn (%): C,
58.9; H, 4.68; N, 7.23. Found (%): C, 58.72; H, 4.63; N, 7.19.
required concentrations of 200, 100, 50, 25, 12.5, 6.25 and 3.12 mg/
mL. The tubes were incubated in BOD incubators at 37 ꢂ 1 ꢁC for
bacteria and 28 ꢂ 1 ꢁC for fungi. The minimum inhibitory con-
centrations (MICs) were recorded by visual observations after 24 h
(for bacteria) and 72e96 h (for fungi) of incubation. Chlor-
amphenicol was used as standard drug.
4.7. Antimicrobial screening
The antimicrobial activity of the synthesized complexes was
tested against some Gram-positive and Gram-negative bacteria and
fungi. The activity of the compounds was compared with standard
reference drug. Minimum inhibitory concentration of the com-
plexes was tested in Sabourauds dextrose broth (SDB) for fungi and
in Nutrient broth (NB) for bacteria by the two-fold serial dilution
4.8. Antibacterial assay (disc diffusion method)
The disc diffusion assay was used to determine antibacterial
activity of the complexes using Gram-positive and Gram-negative
strains of bacteria viz., E. coli, S. typhi, V. cholerae and S. aureus. Base
plates were prepared by pouring 10 mL of autoclaved Muller-
Hinton agar into sterile petridishes (9 cm) and allowed them to
Table 6
ꢁ
ꢀ
Selected bond lengths (A) and bond angles ( ) of 2 and 3.
2
3
Bond length
Zn1eN2
Zn1eS1
Zn1eS2
C14eS1
C14eS2
C14eN1
settle. Sterile blank discs (6 mm) were impregnated with 15
known concentration of stock solution of tested complexes as to
obtain discs containing 100 and 400 g of each complexes.
mL of
2.025(4)
2.3600(7)
2.5621(6)
1.721(2)
1.702(3)
1.339(3)
Zn1eS1
Zn1eS2
Zn1eS3
Zn1eS4
Zn1eN3
Zn1eN4
C1eS1
2.4936(7)
2.5291(6)
2.4507(7)
2.6267(7)
2.1676(18)
2.2156(8)
1.711(2)
1.710(2)
1.347(3)
1.716(2)
1.711(2)
1.339(3)
m
Impregnated discs were air dried and cautiously placed on the
surface of Mueller-Hinton agar plates freshly inoculated with
microorganisms. After 10 min at room temperature the plated
culture incubated for 24 h at 37 ꢁC. Experiments were conducted
in quadruplicate (four discs with identical concentration of the
same compound) and commercial antibiotic Chloramphenicol
C1eS2
C1eN1
C15eS3
C15eS4
C15eN2
(100
mg) impregnated discs used as positive controls. Suscepti-
bility diameter zone was reported as the average value of replicate
measurements.
Bond angle
S2eZn1eS2i
S1eZn1eS1i
S1eZn1eS2
167.02(4)
133.07(4)
73.07(2)
S1eZn1eS2
S1eZn1eS4
S2eZn1eS4
S2eC1eS1
S3eZn1eS4
S4eC15eS3
N6eZn1eN5
71.60(2)
100.99(2)
170.54(2)
118.38(13)
70.77(2)
4.9. Antifungal screening (disc diffusion method)
118.39(13)
75.18(7)
A disc application technique was employed in vitro to evaluate
the antifungal activity of synthesized complexes. Antifungal

146
P.J. Rani, S. Thirumaran / European Journal of Medicinal Chemistry 62 (2013) 139e147
activity of the complexes were tested against M. gypseum, T.
rubrum, E. floccosum and T. mentagrophyte. Mature conidia of fungal
isolates were harvested from potato dextrose agar (PDA) plates and
suspended in ringer solution and spore suspensions standardized
with a haemocytometer (104 conidia mLꢀ1). Conidial suspension
(1 mL) representing each fungal isolate was then spread on a 9 cm
petridishes containing PDA (20 mL) with the excess of conidial
suspension decanted and allow to dry. The compounds were dis-
solved in dimethyl sulfoxide (DMSO). Sterile 6 mm diameter test
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