DNA Binding Studies and Cytotoxicity of a Dinuclear PtII Diazapyrenium-Based Metallo-supramolecular Rectangular Box

The interaction with native DNA of a 2,7-diazapyrenium-based ligand 1 and its PtII rectangular metallacycle 2 is explored through circular and linear dichroism and fluorescence spectroscopies. The metal-free ligand 1 binds through intercalation, with a binding constant of approximately 5×105 M−1, whereas the metallacycle 2 binds and bends the DNA with a binding constant of 7×106 M−1. PCR assays show that metallo-supramolecular box 2 interferes with DNA transactions in vitro whereas the intercalator 1 does not. The metallacycle is active against four human cancer cell lines, with IC50 values ranging between 3.1 and 19.2 μM and shows similar levels of efficacy, but a different spectrum of activity, to cisplatin.