Monofunctional platinum(II) dithiocarbamate complexes: synthesis, characterization and anticancer activity

Heteroleptic platinum(II) dithiocarbamates, of general formula [Pt(DTC)LCl], where DTC = 4-(4-methoxyphenyl) piperazine-1-carbodithioate (1 and 2) and 4-(furan-2-carbonyl) piperazine-1-carbodithioate (3) and L = tri(4-flourophenylphosphine) (1 and 3) and tri(4-chlorophenylphosphine) (2) have been synthesized and characterized by different analytical techniques. These complexes are square planar with picoplatin or phenanthriplatin type steric hindrance from aromatic C-H groups of the phosphine ligand as shown by single-crystal analysis. In 1, the Pt square plane is hindered by two axially oriented hydrogens, whereas by only one in 2 and 3. DNA-binding studies by UV/visible spectroscopy revealed a stronger electrostatic interaction of 1 compared to 2 and 3, and the results are further supported by viscometry and cyclic voltammetric measurements. Their in vitro anticancer activity against five different cancer cell lines using a MTT assay revealed high potency of the complexes. The higher activity of 1 than both 2 and 3 is consistent with DNA binding strength and we speculate that it may be due to the relatively inert nature of platinum towards off-target biomolecules ensured by the hindrance caused by the two axially oriented hydrogens.