The complex 3 was prepared by the procedure as used for (1) with
3-methoxysalicylaldehyde-4(N)-ethylthiosemicarbazone [H2-Msal-etsc] (0.106 g; 0.420
mmol), NiCl2.6H2O (0.100 g; 0.420 mmol) and 1,1ꢁ-bis(diphenylphosphino)methane (0.080
g, 0.210 mmol).Yield: 57%. M.p: 173 °C. Anal. Calcd for C47H48N6O4S2Ni2P2: C, 56.22; H,
4.81; N, 8.37; S, 6.38. Found: C, 56.18; H, 4.78; N, 8.33; S, 6.34%. FT-IR (cm−1) in KBr:
1611 (ꢂC=N), 1326 (ꢂC–O), 738 (ꢂC–S); UV-Vis (DMSO), ꢅmax: 266 (89502) nm
(dm3mol−1cm−1) (intra-ligand transition); 318 (61779) nm (dm3mol−1cm−1) (LMCT s ꢃꢌꢍꢎꢏꢌ
1
418 (18500) nm (dm3mol−1cm−1) forbidden (dꢃd) transition; H NMR (CDCl3, ꢄ ppm, J
Hz): ꢄ 6.540- 6.559 (d, (J= 7.6), C4-H), ꢄ 6.396- 6.435 (t, (JH4H5= 7.6), (JH5H6= 8), C5-H),
ꢄ 6.670- 6.690 (d, (J= 8), C6-H), ꢄ 4.450 (s, terminal –NH), ꢄ 3.599 (s, –OCH3), ꢄ 3.286-
3.335 (m, –CH2), ꢄ 1.143-1.179 (t, (J= 7.2), –CH3), ꢄ 4.095-4.169 (t, (–CH2–)), ꢄ 7.171-
7.261 & ꢄ 7.892-7.969 (m, dppm protons and –CH=N protons).
4.1.4. Preparation of [Ni2(Msal-ptsc)2(µ-dppm)] (4)
The complex 4 was prepared by the procedure as used for (1) with
3-methoxysalicylaldehyde-4(N)-phenylthiosemicarbazone [H2-Msal-ptsc] (0.106 g; 0.420
mmol), NiCl2.6H2O (0.100 g; 0.420 mmol) and 1,1ꢁ-bis(diphenylphosphino)methane (0.080
g, 0.210 mmol).Yield: 63% . M.p: 226 °C. Anal. Calcd for C55H48N6O4S2Ni2P2: C, 60.05; H,
4.40; N, 7.64; S, 5.83. Found: C, 60.01; H, 4.35; N, 7.59; S, 5.78 %. FT-IR (cm−1) in KBr:
1592 (ꢂC=N), 1315 (ꢂC–O), 732 (ꢂC–S); UV-Vis (DMSO), ꢅmax: 268 (51668) nm
(dm3mol−1cm−1) (intra-ligand transition); 327 (34652) &371 (25668) nm (dm3mol−1cm−1)
3
−1
−1
1
ꢃd)
(LMCT s ꢃ d); 429 (13729) nm (dm mol cm ) forbidden (d
transition; H NMR
(CDCl3, ꢄ ppm, J Hz): ꢄ 8.122- 8.144 (d, (J=8.8), CH=N), ꢄ 6.589- 6.605 (d, (J= 6.4), C4-H),
ꢄ 6.449- 6.488 (t, (JH4H5= 7.6), (JH5H6= 8), C5-H), ꢄ 6.743- 6.763 (d, (J= 8), C6-H), ꢄ
7.495-7.518 (d, (J= 9.2), C2’-H & C6’-H), ꢄ 7.941-7.986 (t, (J (H6’H5’) =8.4, J(H2’H3’)
=9.6), C3’-H & C5’-H), ꢄ 6.944-6.995 (m, ( C4’-H), ꢄ 5.29 (s, terminal –NH), ꢄ 3.631 (s, –
OCH3), ꢄ 4.159-4.232 (t, (–CH2–)), ꢄ 7.192-7.473 (m, dppm protons).
4.2. DNA binding study
All of the experiments involving the binding of the compounds with CT DNA were
carried out in deionised water with tris(hydroxymethyl)-aminomethane (Tris, 5 mM) and
sodium chloride (50 mM) and adjusted to pH 7.2 with hydrochloric acid at room temperature.
The concentration of CT-DNA was determined by absorption spectroscopy, using the molar
absorption coefficient (6600 M-1cm-1) at 260 nm. A stock solution of CT-DNA was stored at