Novel ruthenium (II) polypyridyl complexes containing carbazole with flexible substituents: Crystal structure, nonlinear optical properties and DNA-binding interaction

Abstract Five novel ruthenium (II) polypyridyl (N∧N∧N or N∧N∧C) complexes (1–5) containing carbazole with flexible substituents have been synthesized, and fully characterized. The crystal structure of complex 5 was determined by X-ray diffraction analysis. The photophysical properties of them were systematic studied. The complexes exhibited ligand-centered π–π∗ transition in the range of 290–350 nm and metal-to-ligand charge transition bands in the range of 450–650 nm. The third-order nonlinear optical response was measured by Z-scan technique for the complexes. The results revealed that cyclometalated (N∧N∧C) complexes 1 and 2 possess a stronger third-order nonlinear optical response than those of noncyclometalated (N∧N∧N) complexes 3, 4 and 5. The DNA binding behaviors of the complexes have been investigated by spectroscopic and viscosity measurements. It was found that the complexes can interact with DNA in different modes, including classical intercalation for complexes 1–3 and partial intercalation for complexes 4–5.