Highly sensitive ruthenium complex-based fluorescent probe for copper ion detection

Abstract A Ru(II) complex 1 ([Ru(bpy)2(L)](PF6)2 (L = 2-(1H-pyrazol-5-yl)-1H-imidazo-[4,5-f] [1,10] phenanthroline, bpy = 2,2′-bipyridine)), which included adjacent imidazole and pyrazole moieties as responsive bidentate ligand, has been designed and synthesized as a turn-off fluorescent probe for sensitively and selectively detecting Cu2+ in methanol and test strips. It displays easy synthesis, large stokes shift (178 nm) and long emission wavelength (633 nm). After addition of Cu2+, the probe 1 exhibits obvious fluorescence quenching (ca. 83%) and color change from red to dark. The detection limit of Cu2+ ions was as low as 1.78 × 10−8 M, which is far lower than the permissible level of copper ion (∼20 μM) in drinking water set by the EPA (Environmental Protection Agency). Moreover, the results of test strip experiments and real water sample detection experiments demonstrated the probe 1 possesses potential application of ions recognition in environment.