A functionalized cobalt(III) mixed-polypyridyl complex as a newly designed DNA molecular light switch.

The ligand ODHIP (3,4-dihydroxyl-imidazo[4,5-f][1,10]phenanthroline) and its cobalt(III) complex [Co(bpy)(2)(ODHIP)](3+) were synthesized and characterized. Binding of this complex with calf thymus DNA has been investigated by spectroscopic methods and viscosity. The experimental results indicated that the complex bound to DNA by intercalation. In Tris buffer, the complex could emit relatively weak luminescence. After binding to DNA, the notable enhancement was observed. However, when the Cu(2+) was further added, the luminescence decreased gradually and disappeared after the equimolar concentrations of Cu(2+) was added, which exhibited the "off-on-off" properties of molecular light switch.