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 nm for 22AG in Na+ and 43 nm 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. [ABSTRACT FROM AUTHOR]