Ruthenium(II) complexes: structure, DNA-binding, photocleavage, antioxidant activity, and theoretical studies

Abstract

Two triazine-containing ruthenium(II) complexes, [Ru(dmb)₂(pdpt)](ClO₄)₂ (dmb = 4,4′-dimethyl-2,2′-bipyridine, pdpt = 3-(pyridine-2-yl)-5,6-diphenyl-as-triazine) (1) and [Ru(dmb)₂(pdtp)](ClO₄)₂ (pdtp = 3-(pyridine-2-yl)-as-triazino[5,6-f]phenanthrene) (2), were synthesized and characterized by elemental analysis, ES-MS, ¹H NMR, UV-Vis spectra, and cyclic voltammetry; the crystal structure of 2 was determined by X-ray diffraction. DNA-binding behaviors of both complexes were studied by absorption titration, thermal denaturation, and viscosity measurements. The photoactivated DNA cleavage of plasmid pBR322 in the presence of 1 and 2 was explored through gel electrophoresis. Antioxidant activities of the two complexes against hydroxyl radical (^•OH) were also investigated. The results indicate that the DNA-binding affinity of 2 is much greater than that of 1, and that 2 binds to calf thymus DNA by intercalation, but 1 binds in partial intercalation, with π–π stacking on the DNA surface. Experimental findings made through analysis of the CV, absorption spectra, X-ray crystal structure, and the DNA-binding properties were compared with those of theoretical studies using density functional calculations.

Keywords:

• Ruthenium complex
• DNA-binding
• DNA-photocleavage
• Antioxidant activity

Acknowledgments

We are grateful to Shaoguan University for the financial support. We are indebted to Prof. K.C. Zheng (Sun Yat-sen University) for the good works on the DFT calculation, and we are grateful to Prof. Chao Hui (Sun Yat-Sen University) for his specific directions.