M.A. Affan et al. / Inorganica Chimica Acta 387 (2012) 219–225
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C27H29N3SOSn: C, 57.67; H, 5.19; N, 7.47. Found: C, 57.61; H,
5.14; N, 7.43%.
2.8. Cytotoxicity
The substituted thiosemicarbazone ligand (1) and its organo-
tin(IV) complexes (2–5) were screened for toxicity using the pub-
lished method [27] with some modifications. A stock solution of
5000 ppm of the ligand [H2dact, (1)] and its organotin(IV) com-
plexes (2–5) were prepared in DMSO. Then, the stock solutions were
further diluted into seven different levels of dose and later topped
up to 5 mL; which were 1, 5, 10, 50, 100, 150 and 300 ppm. The
hatching process was carried out at ambient temperature for 24 h,
and a pinch of Artemia salina cysts was placed in a beaker with
100 mL treated sea water. During the hatching process, aeration
and light was provided at room temperature. After 24 h, the hatched
nauplii were attracted by the light source and tended to stay at the
surface of the sea water, while the shells and remaining cysts were
deposited at the bottom of the sea water. The shrimps were transfer
to fresh sea water in a Petri dish for ease of calculation. About 20 ac-
tive shrimps were added to 5 mL diluted test solution in each and
every plastic testing mug. After 24 h on incubation under direct
light at room temperature, the mortality of the shrimps in each
mug was counted. The mortality was computed and corrected for
the natural death observed in the negative control using Abbott’s
formula [27]. All results of the mortality were expressed in percent-
ages and plotted in an allosteric sigmoidal graph using a Graph pad
prism.
Scheme 2. The reaction scheme for the synthesis of organotin(IV) complexes (2–5).
1596 (m, C@NAN@C), 1268 (m, CAO), 1027 (w, NAN), 1325, 827
(m, CAS), 580 (w, SnAC), 538 (w, SnAO), 422 (w, SnAN). 1H NMR
(CDCl3) d: 8.77 (s, 1H, N2AH), 8.35 (s, 1H, CyC1AH), 7.43–7.25
(m, 4H, phenyl ring), 2.46 (s, 3H, N@CACH3), 2.07–1.79 (m, 10H,
CyCAH), 1.73–1.70 (t, 2H, SnACH2ACH2ACH2ACH3), 1.63–1.60
(m,
2H,
SnACH2ACH2ACH2ACH3),
1.44–1.39
(m,
2H,
2.9. Antibacterial test
SnACH2ACH2ACH2ACH3), 0.93–0.90 (t, 3H, SnACH2ACH2ACH2A
CH3). 13C NMR (CDCl3) d: 179.22 (N@CAS), 168.55 (C@N),
141.87–136.43 (aromatic ring), 47.99–32.60 (cyclohexyl ring),
32.88, 26.32, 24.88, 20.73 (SnACH2ACH2ACH2ACH3), 16.50 (CH3).
119Sn NMR (CDCl3) d: À183.05. Anal. Calc. for C19H28N3SOSnCl: C,
45.58; H, 5.63; N, 8.39. Found: C, 45.53; H, 5.59; N, 8.36%.
The antibacterial test of synthesized ligand (1) and its organo-
tin(IV) complexes (2–5) was carried out using the agar well
diffusion method [28]. Doxycycline was used as the standard drug.
The bacteria from stock culture were lightly inoculated into the
Mueller Hinton Broth (MHB) and allowed to grow overnight at
37 °C in an ambient air incubator. The culture was diluted with a
new MHB in order to achieve an absorbance value of 2.0 Â 106 col-
ony forming units (CFU/mL) or 0.168 at wavelength of 550 nm in
the spectrophotometer. Sterile cotton swab was dipped into the
broth culture and inoculated on the Mueller Hinton Agar (MHA).
Sterile paper discs with 6 mm diameter were placed on the agar
in equal distance. The recommended concentration of the test sam-
ple (2 mg/mL in DMSO) was introduced individually to each of the
discs. The agar plates were incubated immediately at 37 °C for
20 h. For each plate, DMSO mixture and reference antibacterial
drug such as doxycycline served as negative and positive controls,
respectively. The activity was determined by measuring the
diameter of zones showing complete inhibition (mm). Growth
inhibition was calculated with reference to the positive control.
2.6. Synthesis of [PhSnCl(dact)] (4)
Yield: 0.47 g, 79%: Mp.: 212–214 °C: molar conductance (DMF)
X
À1 cm2 molÀ1: 13.11: UV–Vis (CHCl3) kmax/nm: 265, 331, 386, 404;
FT-IR (KBr, cmÀ1
) mmax: 3104 (s, NH), 2924, 2851 (s, cyclohexyl),
1595 (m, C@NAN@C), 1261 (m, CAO), 1025 (w, NAN), 1328, 822
(m, CAS), 598 (w, SnAC), 531 (w, SnAO), 425 (w, SnAN). 1H NMR
(CDCl3) d: 8.74 (s, 1H, N2AH), 8.36 (s, 1H, CyC1AH), 7.43–7.27
(m, 9H, phenyl ring), 2.49 (s, 3H, N@CACH3), 2.07–1.42 (m, 10H,
CyCAH). 13C NMR (CDCl3) d: 180.77 (N@CAS), 174.45 (C@N),
140.11–138.23 (aromatic ring), 48.30–32.77 (cyclohexyl ring),
17.60 (CH3). 119Sn NMR (CDCl3) d: À188.92. Anal. Calc. for
C21H24N3SOSnCl: C, 48.44; H, 4.64; N, 8.07. Found: C, 48.40; H,
4.59; N, 8.02%.
3. Results and discussion
2.7. Synthesis of [Ph2Sn(dact)] (5)
The ligand 2-hydroxyacetophenone-N(4)-cyclohexylthiosemic-
arbazone (H2dact) was prepared by the condensation reaction of
2-hydroxyacetophenone and N(4)-cyclohexylthiosemicarbazide.
The ligand (1) acts as dinegative tridentate ONS donors in this
work. It has two tautomers within the structure, existing as either
a thione or a thiol tautomer (Scheme 1). Four new organotin(IV)
complexes (2–5) were obtained in good yields by the equimolar
reaction of organotin(IV) salts with H2dact (1) (Scheme 2). The
physical and analytical data of 1–5 are given in the experimental
section. All organotin(IV) compounds were stable in N2 atmo-
sphere and soluble in common organic solvents. The molar
conductivity of the organotin(IV) complexes (2–5) in DMF is
Yield: 0.48 g, 75%: Mp.: 258–260 °C: molar conductance (DMF)
X
À1 cm2 molÀ1: 8.17: UV–Vis (CHCl3) kmax/nm: 264, 350, 382, 408:
FT-IR (KBr, cmÀ1
) mmax: 3103 (s, NH), 2923, 2850 (s, cyclohexyl),
1598 (m, C@NAN@C), 1267 (m, CAO), 1021 (w, NAN), 1347, 822
(m, CAS), 600 (w, SnAC), 533 (w, SnAO), 447 (w, SnAN). 1H NMR
(CDCl3) d: 8.78 (s, 1H, N2AH), 8.39 (s, 1H, CyC1AH), 7.40–7.32
(m, 14H, phenyl ring), 2.51 (s, 3H, N@CACH3), 2.09–1.41 (m, 10H,
CyCAH). 13C NMR (CDCl3) d: 179.98 (N@CAS), 171.75 (C@N),
142.20–138.21 (aromatic ring), 50.48–32.83 (cyclohexyl ring),
15.88 (CH3). 119Sn NMR (CDCl3) d: À170.10. Anal. Calc. for