Probing the binding of tetraplatinum(pyridyl)porphyrin complexes to DNA by means of surface plasmon resonance

Tetrapyridylporphyrins containing four chloro(2,2′-bipyridine)platinum(II) complexes attached at the meta (3-H2TPtPyP) and para (4-H2TPtPyP) positions of the peripheral pyridine ligands were synthesized and their interaction with DNA investigated. The compounds were isolated in the solid state and characterized by means of spectroscopic and analytical techniques. According to molecular simulations, the two isomers exhibit contrasting structural characteristics, consistent with a saddle shape configuration for 3-H2TPtPyP and a planar geometry for 4-H2TPtPyP. Surface plasmon resonance studies were carried out on the interaction of the complexes with calf thymus DNA, revealing a preferential binding of 3-H2TPtPyP, presumably at the DNA major grooves.