Synthesis of platinum(II) complexes of isatin thiosemicarbazones derivatives: In vitro anti-cancer and deoxyribose nucleic acid binding activities

Six new platinum(II) complexes of a thiosemicarbazone Schiff base with isatin moiety [PtL1 to Pt(L6)2] were synthesized by the reaction of platinum(II) with the following: (Z)-2-(2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide [L1H], (Z)-2-(5-methyl-2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide [L2H], (Z)-2-(5-fluoro-2-oxoindolin-3-ylidene)-N-phenylhydrazinecarbothioamide [L3H], (Z)-N-methyl-2-(5-nitro-2-oxoindolin-3-ylidene)hydrazinecarbothioamide [L4H], (Z)-N-methyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide [L5H], and (Z)-N-ethyl-2-(5-methyl-2-oxoindolin-3-ylidene)hydrazinecarbothioamide [L6H]. The structures of these complexes were characterized by elemental analysis, IR, UV–Vis, 1H NMR, and mass spectrometry analyses. The structure of Pt(L6)2 was further characterized by single-crystal XRD. The interaction of these complexes with calf thymus (CT) DNA exhibited a high intrinsic binding constant (Kb = 3.5 × 104 to 3.29 × 106 M−1), which reflected the intercalative activity of these complexes toward CT DNA. This result was also confirmed by viscosity data. Data obtained from the in vitro anti-proliferative study clearly established the anticancer potency of PtL1, PtL2, PtL3, PtL5, and Pt(L6)2 against the human colorectal carcinoma cell line HCT 116.