The effects of linear assembly of two carbazole groups on acid–base and DNA-binding properties of a ruthenium(II) complex

• A Ru complex containing two carbazoles is synthesized.
• The complex acts as a pH-induced off–on–off luminescence switch.
• The complex binds to DNA in a partially intercalative mode.
• DNA binding constant is of 105 order of magnitude.

A novel Ru(II) complex of [Ru(bpy)2(Hbcpip)](ClO4)2 {where bpy = 2,2-bipyridine, Hbcpip = 2-(4-(9H-3,9′-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} is synthesized and characterized. Calf-thymus DNA-binding properties of the complex were studied by UV–vis absorption and luminescence titrations, steady-state emission quenching by [Fe(CN)6]4−, DNA competitive binding with ethidium bromide, thermal denaturation and DNA viscosity measurements. The results indicate that the complex partially intercalated into the DNA with a binding constant of (5.5 ± 1.4) × 105 M−1 in buffered 50 mM NaCl. The acid–base properties of the complex were also studied by UV–visible and luminescence spectrophotometric pH titrations, and ground- and excited-state acidity ionization constant values were derived.

A novel Ru(II) complex carrying two linearly assembled carbazoles, act as a DNA partial intercalation and a pH-induced luminescence off–on–off switch.Figure optionsDownload as PowerPoint slide