The Effects of Grafting of 2-Pyridyl to [Ru(bpy)2(Hpip)]2+on Acid-Base and DNA-Binding Properties: Experimental and DFT Studies
摘要:
A new Ru(II) complex of [Ru(bpy)(2)(Hppip)](2+) {bpy = 2,2'-bipyridine; Hppip = 2-(4-(pyridin-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} has been synthesized by grafting of 2-pyridyl to parent complex [Ru(bpy)(2)(Hpip)](2+) ( Hppip = 2-(4-phenyl)-1H-imidazo[4,5-f] [1,10]phenanthroline). The acid-base properties of [Ru(bpy)(2)(Hppip)](2+) studied by UV-visible and luminescence spectrophotometric pH titrations, revealed off-on-off luminescence switching of [Ru(bpy)(2)(Hppip)](2+) that was driven by the protonation/deprotonation of the imidazolyl and the pyridyl moieties. The complex was demonstrated lobe a DNA intercalator with an intrinsic DNA binding constant of (5.56 +/- 0.2) x 10(5) M-1 in buffered 50 mM NaCl, as evidenced by UV-visible and luminescence titrations, reverse salt effect. DNA competitive binding with ethidium bromide, steady-state emission quenching by [Fe(CN)(6)](4-), DNA melting experiments and viscosity measurements. The density functional theory method was also used to calculate geometric/electronic structures of the complex in an effort to understand the DNA binding properties. All the studies indicated that the introduction of 2-pyridyl onto Hpip ligand is more favorable for extension of conjugate plane of the main ligand than that of phenyl, and for greatly enhanced ct-DNA binding affinity accordingly.