Synthesis, DNA-binding and spectral properties of novel complexes [RuL2(idpq)]2+ (L = bpy, phen) with embedded CO

A novel ligand idpq with embedded CO and its two complexes, [Ru(bpy)2(idpq)]2+ 1 and [Ru(phen)2(idpq)]2+ 2 (bpy = 2,2′-bipyridine; phen = 1,10-phenanthroline; idpq = indeno[1,2-b]dipyrido [3,2-f:2′,3′-h]-quinoxaline-6-one), have been synthesized and characterized by elemental analysis, ES-MS, 1H NMR, UV–vis and CV. The DNA-binding behaviors of both complexes were studied by spectroscopic methods and viscosity measurements. The results indicate that the two complexes can all bind to CT-DNA in an intercalative mode, and they have rather high DNA-binding constants, which are (1.7 ± 0.4) × 106 M−1 and (4.0 ± 0.6) × 106 M−1, respectively. The results also show that these two Ru(II) complexes can promote photocleavage of pBR322 DNA. Their DNA-binding and electronic absorption-spectral properties were further studied by the DFT/TDDFT methods. The DNA-binding behaviors and difference of these complexes were reasonably explained, and the simulated absorption spectra were in good agreement with the experimental ones.