Three platinum complexes with both a chloride anion and a chelated carboxylate as leaving groups were synthesized and spectrally characterized. In vitro cytotoxicity of complexes 1-3 was evaluated against human A549, HCT-116, MCF-7, and HepG-2 tumor cell lines. The results showed that all the compounds exhibited effective cytotoxicity against the tested cell lines, nearly comparable to those of cisplatin and oxaliplatin. Notably, the activity of complex 2 was about 2-fold better than that of oxaliplatin against the HCT-116 cell line. Flow cytometry analysis indicated that these complexes produced death of tumor cells through an apoptotic pathway. The DNA-binding properties of the platinum-based compounds were also studied by agarose gel electrophoresis. The kinetics study showed that the chloride anion departs from the Pt atom quickly, whereas the five and/or six-membered ring formed by coordination of N,O-donors and the metal ion is opened a little more slowly by the rupture of a Pt-O bond, which helps us to further understand the mechanism of action of the newly synthesized complexes with biomolecules. Furthermore, the reaction rate constants of complexes 1-3 were roughly the same.