1
46
M. Sirajuddin et al. / Inorganica Chimica Acta 439 (2016) 145–158
poisoning. Due to their ability to form thermodynamically stable
complexes, they are also used as chelating agents for the extraction
of trace metals. Metal complexes of dithiocarbamates present a
wide range of applications in agriculture, medicines, industry
and, in analytical and organic chemistry. The use of dithiocarba-
mate complexes in the rubber vulcanization process is an example
of their commercial importance [13].
Keeping in view the structural and biological diversity of organ-
otin(IV) compounds, here we present the synthesis, characteriza-
tion, in vitro biological activity and interaction with SS-DNA as
well as POM analyses of pyrrolidine-1-carbodithioate based organ-
otin(IV) complexes.
the desired sodium salt of the ligand. The chemical reaction is
shown in Scheme 1.
2.2.2. Procedure for the synthesis organotin(IV) complexes
Stoichiometric amount of sodium salt of pyrrolidine-1-carbod-
ithioate was suspended in dry toluene and to it calculated amount
of organotin(IV) chloride, [{for R
(for Complexes 1–4)}; {for R SnCl
Complexes 5–7)}; {for RSnCl : NaL = both 1:1 molar ratio (for
3
SnCl: NaL = 1:1 molar ratio
2
2
: NaL = 1:2 molar ratio (for
3
Complexes 8–9) and 1:2 molar ratio (for Complex 10)}], was added.
The mixture was stirred and refluxed for 3–4 h, and then it was
cooled and filtered to remove NaCl. The filtrate was rotary evapo-
rated to get the product which was recrystallized in chloroform.
The chemical reaction is shown in Scheme 1.
2
. Experimental
2
.2.3. DNA interaction study assay by UV–visible spectroscopy
SS-DNA (50 mg) was dissolved by overnight stirring in deion-
2.1. Materials and methods
ized water (pH = 7.0) and kept at 4 °C. Deionized water was used
to prepare buffer (20 mM Phosphate buffer (NaH PO -Na HPO ),
pH = 7.2). A solution of (SS-DNA) in the buffer gave a ratio of UV
absorbance at 260 and 280 nm (A260/A280) of 1.8, indicating that
the DNA was sufficiently free of protein [18–20]. The DNA concen-
tration was determined via absorption spectroscopy using the
Reagents Me
BuSnCl , PhSnCl
USA) and were used without further purification. All the solvents
purchased from E. Merck (Germany) were dried before use accord-
ing to literature procedures [14]. Dibenzyltin dichloride (Bz SnCl
and tribenzyltin chloride (Bz SnCl) were prepared according to the
3
SnCl, Et
, pyrrolidine and CS
3
SnCl, Cy
3
SnCl, Me
2 2 2 2
SnCl , t-Bu SnCl ,
2
4
2
4
3
3
2
were obtained from Aldrich
(
2
2
)
3
ꢀ1
ꢀ1
molar absorption coefficient of 6600 M cm
(260 nm) for
reported method [15]. Sodium salt of Salmon fish sperm DNA (SS-
DNA) (Arcos) was used as received. The melting points were deter-
mined in a capillary tube using a Gallenkamp (UK) electrothermal
ꢀ4
SS-DNA [21–23] and was found to be 1.8 ꢁ 10 M. The compound
was dissolved in DMSO at a concentration of 1 mM. The UV absorp-
tion titrations were performed by keeping the concentration of the
compound fixed while varying the SS-DNA concentration.
Equivalent solutions of SS-DNA were added to the complex and
reference solutions to eliminate the absorbance of DNA itself.
Compound-DNA solutions were allowed to incubate for about
ꢀ1
melting point apparatus. IR spectra in the range of 4000–100 cm
were obtained on a Thermo Nicolet-6700 FT-IR Spectrophotome-
ter. Elemental analysis was done using a CE-440 Elemental
Analyzer (Exeter Analytical, Inc). 1H, C and
13
119
Sn NMR were
recorded on a 400 MHz JEOL ECS instrument, using CDCl
3
as an
-d3)
Sn
Sn NMR
the measurement was recorded at a working frequency of
7.29 MHz and the chemical shift was referenced to Me Sn as an
1
0 min at room temperature before measurements were made.
1
13
internal reference [ H(CDCl
3
-d3) = 7.28 and
C(CDCl
3
Absorption spectra were recorded using cuvettes of 1 cm path
length at room temperature (25 ± 1 °C).
1
13
=
77 ppm]. Tetramethylsilane (for H and C NMR) and Me
4
1
19
119
(
for
Sn NMR) were used as external standards. For
2.2.4. Viscosity measurements
3
4
Viscosity measurements were carried out using Ubbelohde vis-
cometer at room temperature (25 ± 1 °C). Flow time was measured
with a digital stopwatch. Each sample was measured three times
and an average flow time was calculated. Data were presented as
external standard. Chemical shifts are given in ppm and coupling
constants (J) values are given in Hz. The multiplicities of signals
1
in H NMR are given with chemical shifts; (s = singlet, d = doublet,
t = triplet, q = quartet, m = multiplet). The absorption spectra were
measured on a Shimadzu 1800 UV–Visible Spectrophotometer.
Complexes 3, 6 and 7 were collected at room temperature on a
Bruker Apex II CCD diffractometer. Complex 9 was collected at
1/3
relative viscosity, (
where
is the viscosity of DNA alone. Viscosity values were calculated
from the observed flow time of DNA containing solution ( ),
= t ꢀ t [24].
g
/
g
o
)
, vs. binding ratio ([Compound]/[DNA])
g
is the viscosity of DNA in the presence of complex and
g
o
g
o
1
90 (2) K on Agilent Super Nova (Dual, Cu at zero, Eos) diffractome-
g
o
o
ter. All the non-hydrogen atoms were refined using anisotropic
atomic displacement parameters, and hydrogen atoms bonded to
carbon were inserted at calculated positions using a riding model.
Hydrogen atoms bonded to O or N were located from difference
maps and their coordinates refined. SHELXTL [16] was used to solve
and SHELX2012 [17] to refine the structures. Viscosity was measured
by Ubbelohde viscometer at room temperature.
2.2.5. Cytotoxicity
Cytotoxicity was studied by brine-shrimp lethality assay
method [25,26]. Brine-shrimp (Artemia salina) eggs were hatched
in artificial sea water (3.8 g sea salt/L) at room temperature
(
22–29 °C). After two days these shrimps were transferred to vials
containing 5 mL of artificial sea water (10 shrimps per vial) with
0, 100 and 1000 g/mL final concentrations of each compound
taken from their stock solutions of 12 mg/mL in DMSO. After
4 h number of surviving shrimps was counted. Data were ana-
1
l
2
2
.2. Synthesis
2
.2.1. Synthesis of pyrrolidine-1-carbodithioic acid (HL) and sodium
lyzed with a biostat 2009 computer program (Probit analysis) to
determine LD50 values.
pyrrolidine-1-carbodithioate (NaL)
The ligand (HL) was prepared by the reaction of stoichiometric
amounts of pyrrolidine and CS
2
in 50 mL of absolute methanol at
2.2.6. Petra/Osiris/Molinspiration (POM) analyses
room temperature. The solution was stirred at room temperature
for 4 h and precipitates appeared. The precipitates were filtered,
washed with diethyl ether and then air dried. Sodium salt of the
ligand (NaL) was prepared by the addition of an aqueous solution
of sodium hydrogen carbonate (NaHCO ) to a suspended solution
3
of HL in distilled water. The mixture was stirred at room tempera-
Petra/Osiris/Molinspiration analysis (POM) is one of the well-
known approach that has been used regularly to produce the two
dimensional models to identify and to indicate the type of pharma-
cophore site that affects biological activity with a change in the
chemical substitution. The advantages of POM are the ability to
predict the biological activities of the molecules and to represent
the relationships between steric/electrostatic property as well as
ture to get a clear solution which was then rotary evaporated to get