Synthesis, characterization and biological evaluation of dipicolylamine sulfonamide derivatized platinum complexes as potential anticancer agents

Three new Pt complexes, [PtCl(2)(N(SO(2)(2-nap))dpa)], [PtCl(2)(N(SO(2)(1-nap))dpa)] and [PtCl(2)(N(SO(2)pip)dpa)], containing a rare 8-membered ring were synthesized in good yield and high purity by utilizing the ligands N(SO(2)(2-nap))dpa, N(SO(2)(1-nap))dpa and N(SO(2)pip)dpa, which contain a dipicolylamine moiety. Structural studies of all three complexes confirmed that the ligands are bound in a bidentate mode via Pt–N((pyridyl)) bonds forming a rare 8-membered ring. The intense fluorescence displayed by the ligands is quenched upon coordination to Pt. According to time dependent density functional theory (TDDFT) calculations, the key excitations of N(SO(2)(2-nap))dpa and [PtCl(2)(N(SO(2)(1-nap))dpa)] involve the 2-nap-ligand-centered π → π* excitations. While all six compounds have shown antiproliferative activity against human breast cancer cells (MCF-7), the N(SO(2)pip)dpa and N(SO(2)(2-nap))dpa ligands and [PtCl(2)((NSO(2)pip)dpa)] complex have shown significantly high cytotoxicity, directing them to be further investigated as potential anti-cancer drug leads.