2
76
K.W. Tan et al. / Polyhedron 38 (2012) 275–284
2
. Experimental
8.24 (d, 1H, NHCH3, J = 4 Hz), 7.68 (d, 1H, aromatic, J = 8 Hz), 6.26
(
s, 1H, aromatic), 6.24 (d, 1H, aromatic, J = 8 Hz), 2.95 (d, 3H,
1
3
2.1. Materials and solutions
3 6
NCH , J = 4 Hz). Characteristic C NMR signals (DMSO-d , TMS,
ppm): 177.61 (C@S), 160.87 (C–O), 158.40 (C–O), 140.54 (C@N),
The solvents were purchased from Merck and the reactants for
3
128.67, 112.45, 108.19, 102.80 (C-aromatic), 31.28 (N-CH ).
syntheses were from Sigma. The pBR322, gene ruler 1 kb DNA lad-
der, 6ꢀ loading buffer and Tris-(hydroxymethyl)aminomethane
2.3.3. Synthesis of 2,4-dihydroxybenzaldehyde
4-ethylthiosemicarbazone, H E (3)
3
(
Tris) were procured from BioSyn Tech (Fermentas). Analytical
grade agarose powder was obtained from Promega. Sodium chlo-
ride, human DNA topoisomerase I and ethidium bromide were pur-
chased from Sigma Chemical Co. (USA). The aqueous solutions for
DNA experiments were prepared with ultra-pure water from an
Elga PURELAB ULTRA Bioscience water purification system with a
UV light accessory. The Tris–NaCl (TN) buffer was prepared from
the combination of Tris base and NaCl dissolved in water and its
pH was adjusted with hydrochloric acid (HCl) solution to pH 7.5.
The Tris–NaCl buffer pH 7.5 contains Tris at 5 mM and NaCl at
Similar to the preparation of 1.
Yield: 2.05 g, 86%. Anal. Calc. for C10H N O S: C, 50.19; H, 5.48;
13 3 2
ꢁ
1
N, 17.56. Found: C, 50.32; H, 5.28; N, 17.78%. IR (KBr disc, cm ):
3382 m, 3295 m, 3163 s, 2979 w, 1626 s, 1579 m, 1551 s, 1499
s, 1401 m, 1302 s, 1241 s, 1166 s, 1126 m, 1099 m, 938 w, 867
w, 820 w, 801 w, 741 w, 642 w, 621 w, 522 m (s, strong; m, med-
ium; w, weak).
11.16 (s, 1H, NHCS), 9.76 (s, 2H, OH), 8.26 (s, 1H, CH@N), 8.31 (d,
1H, NHCH
aromatic), 6.30 (d, 1H, aromatic, J = 8 Hz), 3.57 (m, 2H, NCH
J = 4 Hz) 1.14 (d, 3H, NCH
CH3, J = 4 Hz). Characteristic 13C NMR
signals (DMSO-d TMS, ppm): 176.34 (C@S), 160.84 (C–O),
58.40 (C–O), 140.99 (C@N), 128.88, 112.34, 108.32, 102.81 (C-aro-
matic), 32.20 (N-CH –), 15.21 (NCH CH ).
2 ,
–
J = 4 Hz), 7.72 (d, 1H, aromatic, J = 8 Hz), 6.32 (s, 1H,
5
0 mM. All the test compounds in N,N-dimethylformamide
2
–,
(
DMF) were freshly prepared daily.
2
6
,
1
2.2. Physical measurements
2
2
3
IR spectra were recorded as KBr pellets by using a Perkin-Elmer
2
4
.3.4. Synthesis of 2,4-dihydroxybenzaldehyde
-phenylthiosemicarbazone, H P (4)
Similar to the preparation of 1.
Yield: 0.23 g, 80%. Anal. Calc. for C14
N, 14.62. Found: C, 58.38; H, 4.26; N, 14.29%. IR (KBr disc, cm ):
331 m, 3144 m, 2974 m, 1629 s, 1542 s, 1223 m, 1264 s, 1210
Spectrum RX-1 spectrophotometer. NMR spectra were recorded in
deuterated DMSO-d on a JEOL JNM-LA400 or ECA 400 MHz instru-
3
6
ment. Elemental analyses were performed on a Thermo Finnigan
Eager 300 CHNS elemental analyzer. UV–Vis spectroscopic mea-
13 3 2
H N O S: C, 58.52; H, 4.56;
ꢁ1
surements were carried out on
spectrophotometer.
a Perkin-Elmer Lambda 40
3
s, 1121 s, 978 m, 838 w, 743 w, 694 w (s, strong; m, medium; w,
weak).
2
2
.3. Syntheses
.3.1. Synthesis of 2,4-dihydroxybenzaldehyde thiosemicarbazone,
Characteristic 1H NMR signals (DMSO-d
6
, TMS, ppm): 11.54 (s,
H, NHCS), 9.93 (s, 1H, OH), 9.89 (s, 1H, OH), 8.72 (s, 1H, NHC ),
.34 (s, 1H, CH@N), 7.82 (d, 1H, aromatic, J = 8 Hz), 7.53 (d, 2H, aro-
1
8
6 5
H
H
3
T (1)
matic, J = 8), 7.33 (t, 2H, aromatic, J = 8), 7.16 (t, 1H, aromatic, J = 8),
.29 (s, 1H, aromatic), 6.27 (d, 1H, aromatic, J = 4 Hz). Characteris-
The ligand was synthesized by minor modification to the proce-
6
dure reported by Zhu et al. [6]. Thiosemicarbazide (0.09 g, 1 mmol)
and 2,4-dihydroxybenzaldehyde (0.14 g, 1 mmol) were heated in
an ethanol/water mixture (20/5 ml) for 3 h. Slow evaporation of
the solvent yielded yellow crystals. The crystals were filtered,
washed with cold methanol and ether, dried in air and kept in a
desiccator over silica gel.
13
tic C NMR signals (DMSO-d
6
, TMS, ppm): 175.57 (C@S), 161.21
C–O), 158.75 (C–O), 141.73 (C@N), 139.64, 129.25, 126.06,
(
1
25.66, 112.23, 108.38, 102.84 (C-aromatic).
2
.3.5. Synthesis of (4-hydroxy-2-oxidobenzaldehyde
0
thiosemicarbazonato)-(2,2 -bipyridine)zinc(II), [Zn(bipy)(HT)] (5)
Yield: 0.18 g, 85%. Anal. Calc. for C
N, 19.89. Found: C, 45.98; H, 3.94; N, 20.01%. IR (KBr disc, cm ):
478 m, 3342 m, 3174 s, 2997 w, 1625 s, 1555 s, 1507 s, 1379
H
8 9
N
3
O
2
S: C, 45.49; H, 4.29;
0
Zinc acetate dihydrate (0.22 g, 1 mmol) and 2,2 -bipyridine
ꢁ1
(
0.16 g, 1 mmol) were heated in ethanol (20 ml) for 1 h followed
by addition of 2,4-dihydroxybenzaldehyde thiosemicarbazone,
T (0.21 g, 1 mmol) in hot ethanol (20 ml) and the mixture was
3
m, 1317 m, 1287 m, 1239 s, 1165 s, 1122 s, 864 m, 810 m, 792
H
3
m, 482 m, 452 m (s, strong; m, medium; w, weak).
refluxed for another 3 h. The yellow complex that formed was fil-
tered, washed with cold methanol and ether, dried in air and kept
in a desiccator over silica gel. Yield: 0.28 g, 65%. Anal. Calc. for
C
3
3
1
1
Characteristic H NMR signals (DMSO-d
6
, TMS, ppm): 11.49 (s,
1
H, NHCS), 9.75 (s, 2H, OH), 8.20 (s, 1H, CH@N), 7.92 (s, 1H,
NH ), 7.71 (s, 1H, NH ), 7.64 (d, 1H, aromatic, J = 8 Hz), 6.26 (s,
H, aromatic), 6.21 (d, 1H, aromatic, J = 8 Hz). Characteristic
2
2
18
H
15
N
5
O
2
SZn: C, 50.18; H, 3.51; N, 16.26. Found: C, 50.43; H,
1
3
1
C
ꢁ1
.26; N, 16.54%. IR (KBr disc, cm ): 3428 w, 3316 m, 3142 w,
070 w, 3069 w, 1604 s, 1478 s, 1444 m, 1315 m, 1252 m,
219 s, 1175 s m, 1122 m, 842 w, 763 m, 553 w, 420 w (s, strong;
6
NMR signals (DMSO-d , TMS, ppm): 177.40 (C@S), 161.04 (C–O),
58.56 (C–O), 140.97 (C@N), 128.67, 112.11, 108.26, 102.80 (C-
aromatic).
1
m, medium; w, weak).
Characteristic 1H NMR signals (DMSO-d
, TMS, ppm): 9.47 (s,
6
2
4
.3.2. Synthesis of 2,4-dihydroxybenzaldehyde
-methylthiosemicarbazone, H M (2)
broad, 1H, OH), 8.62 (d, 2H, bipy, J = 4 Hz), 8.42 (d, 2H, bipy,
J = 8 Hz), 8.18 (s, 1H, CH@N), 7.98 (t, 2H, bipy, J = 8 Hz), 7.48 (d,
2H, bipy, J = 4 Hz), 6.92 (s, broad, 1H, aromatic), 6.30 (s, broad,
3
Similar to the preparation of 1.
Yield: 0.20 g, 89%. Anal. Calc. for C
H
9 11
N
3
O
2
S: C, 47.99; H, 4.92;
2
1H, aromatic), 6.02 (s, broad, 1H, aromatic + 2H, –NH ).
ꢁ1
N, 18.65. Found: C, 48.28; H, 5.21; N, 18.98%. IR (KBr disc, cm ):
342 m, 3249 m, 3127 w, 1625 s, 1573 s, 1521 m, 1459 w, 1331
3
2.3.6. Synthesis of (4-hydroxy-2-oxidobenzaldehyde
0
s, 1270 m, 1231 s, 1166 m, 1125 m, 1019 m, 967 w, 868 m, 817
m, 780 w, 670 m, 635 m, 586 w, 547 w, 497 w, 374 w (s, strong;
m, medium; w, weak).
4-methylthiosemicarbazonato)-(2,2 -bipyridine)zinc(II) trihydrate,
[Zn(bipy)(HM)]ꢂ3H
2
O (6)
Similar to the preparation of 5.
Characteristic 1H NMR signals (DMSO-d
, TMS, ppm): 11.18 (s,
H, NHCS), 9.88 (s, 1H, OH), 9.74 (s, 1H, OH), 8.20 (s, 1H, CH@N),
6
23 5 5
Yield: 0.40 g, 80%. Anal. Calc. for C19H N O SZn: C, 45.74; H,
4.65; N, 14.04. Found: C, 4.53; H, 4.21; N, 13.59%. IR (KBr disc,
1