Reaction of cis-[PtCl2(DMSO)2] with the ligand 4-methyl-2-N-(2-pyridylmethylene)aminophenol (Hpyrimol, LH) in methanol at room temperature produces the complexes [PtCl2LH] or [PtClL], under acidic or basic conditions, respectively. The two platinum compounds exhibit distinct DNA-interacting properties, [PtCl2LH] showing a higher affinity for the biomolecules. Furthermore, [PtClL] is clearly more cytotoxic than [PtCl2LH] in three different cancer cell lines. Solution studies reveal the occurrence of intricate solvation processes generating different aquated/hydroxido species, whose nature depends on the starting metal complex and the pH of the medium.