Indole-7-carbaldehyde thiosemicarbazone as a flexidentate ligand toward ZnII, CdII, PdII and PtII ions: cytotoxic and apoptosis-inducing properties of the PtII complexElectronic supplementary information (ESI) available: X-ray crystallographic files in CIF format, tables for the selected geometrical parameters for the crystal structures, tables for crystal data and refinement parameters, 1H, 13C NMR, HSQC and HMBC spectra of selected compounds. CCDC 939908-939913 for ZnBr2(LH2)2·2MeOH, CdCl2(LH2

A new thiosemicarbazone (LH 2 ) derived from indole-7-carbaldehyde was synthesized and reacted with Zn II , Cd II , Pd II and Pt II salts. The reactions with zinc and cadmium salts in 2 : 1 (ligand-metal) molar ratio afforded complexes of the type MX 2 (LH 2 ) 2 , (X = Cl, Br or OAc), in which the thiosemicarbazone acts as a neutral S -monodentate ligand. In the presence of potassium hydroxide, the reaction of LH 2 with ZnBr 2 resulted in deprotonation of the thiosemicarbazone at the hydrazine and indole nitrogens to form Zn(L)(CH 3 OH). The reaction of LH 2 with K 2 PdCl 4 in the presence of triethylamine, afforded Pd(L)(LH 2 ) which contains two thiosemicarbazone ligands: one being dianionic N , N , S -tridentate while the other one is neutral S -monodentate. When PdCl 2 (PPh 3 ) 2 was used as the Pd II ion source, Pd(L)(PPh 3 ) was obtained. In a similar manner, the analogous platinum complex, Pt(L)(PPh 3 ), was synthesized. The thiosemicarbazone in the latter two complexes behaves in a dianionic N , N , S -tridentate fashion. The platinum complex was found to have significant cytotoxicity toward four cancer cells lines, namely MDA-MB-231, MCF-7, HT-29, and HCT-116 but not toward the normal liver WRL-68 cell line. The apoptosis-inducing properties of the Pt complex was explored through fluorescence microscopy visualization, DNA fragmentation analysis and propidium iodide flow cytometry. The Pt( ii ) complex of a new series of thiosemicarbazone complexes exhibits cancer-selective cytotoxicity.