An unexpected fluorescent probe for G-quadruplex DNA based on a nitro-substituted ruthenium (II) complex

The detection of G-quadruplex is of major interest. Nitro-substituted ruthenium (II) complexes have attracted much attention due to fluorescent sensitivity to environment change. We report here a new nitro-substituted ruthenium (II) complex, [Ru (phen) 2 (hnoip)] 2+ ( 1) (hnoip = 2-(2-hydroxyl-5-nitrophenyl)imidazo[4,5- f ][1,10-phenanthroline]), which displays distinct fluorescent properties in aqueous solution and non-aqueous solvents. This complex exhibits large fluorescence enhancement after binding with G-quadruplex DNA, and displays good fluorescent selectivity over other DNAs. The limit of detection is 6 n m for 22AG in Na + and 43 n m for 22AG in K + , respectively. The results demonstrated that nitro-substituted ruthenium (II) complexes can be utilized to design as G-quadruplex fluorescent probes by protection of the nitro group on the complex from water.