Ruthenium(II) complexes of 1,12-diazaperyiene and their interactions with DNA

Four complexes of the ligand 1,12-diazaperylene (DAP) have been prepared, [Ru(bpy)(n)(DAP)(3-n)](2+) where n = 0-2 and [Ru(DAP)(3)](2+). The [Ru(DAP)(3)](2+) complex was characterized by X-ray analysis and was found to exhibit the expected propeller-like structure with significant intermolecular pi-stacking interactions. The three Ru(II) complexes showed self-consistent optoelectronic properties with similar ligand-centered pi-pi(*) absorptions in the range of 333-468 nm and MLCT bands associated with the DAP which increased in intensity and decreased in energy as the number of DAP ligands varied from 1 to 3. Hypochromicity and viscosity changes were observed that were consistent with DAP intercalation into DNA, and binding constants were measured in the range of 1.4-1.6 x 10(6) M-1 for the mixed ligand complexes. Furthermore, the complex [Ru(bpy)(2)(DAP)](2+) was found to photocleave plasmid DNA upon irradiation with visible light.