A novel molecular "light switch", [Ru(bpy)(2)(HNOIP)](21) (HNOIP = 2-(2-hyd
loxy-5-nitropllenyl)imidazo[4,5-f][1,10]phenanthroline), for DNA was develo
ped. In aqueous solution the suppressed luminescence carl be revived by the
presence of Poly[dA]. Poly[dT], Poly[dG]. Poly[dC] and calf thymus DNA.