The design of new molecular "light switches" for DNA

Two novel ruthenium(II) complexes, [Ru(pztp)(2)(phen)] (ClO4)(2) and [Ru(pz tp)(2)(bpy)] (ClO4)(2), have been synthesized and characterized by UV/Vis a nd H-1 NMR spectroscopies and mass spectrometry. The MeCN solutions of both complexes display fluorescence that was found to be highly sensitive to th e presence and concentration of water. The complexes behave like a "light s witch" for DNA in that they do not luminesce in water but were "turned on" in the presence of DNA and show emission enhancement with the increase of D NA concentration. Their DNA binding behavior was also studied by absorption spectroscopy and viscosity measurements, which suggest that the DNA-comple x interaction involves intercalation of the metal-bound pztp ligand into th e base pairs of duplex DNA.