Ambivalent intercalators for DNA: L-shaped platinum(II) complexes

Novel platinum(II) square planar coordination complexes, in which two heteroaromatic ligands are held by the
metal in an unusual L-shaped geometry orthogonal to each other, have been synthesized, and their interaction
with DNA was investigated with absorption and linear dichroism spectroscopy. As a rule, the ligand that is coplanar
with the coordination square of Pt is found to be oriented perpendicular relative to the DNA helix axis when bound,
suggestive of its intercalation between the base pairs of DNA. However, when this coplanar ligand is replaced by
two pyridines, the opposite ligand, orthogonal to the coordination square, is instead preferentially intercalated. This
behavior shows that these new complexes do indeed show some properties of true ambintercalators, i.e., compounds
that can bind by intercalation of either of two distinct aromatic moieties.