Highly Sensitive and Selective Difunctional Ruthenium(II) Complex-Based Chemosensor for Dihydrogen Phosphate Anion and Ferrous Cation

The anion-interaction properties of a Ru(II) complex of [Ru(bpy)(2)(Htppip)](ClO4)(2)center dot H2O center dot DMF (RuL) [bpy =2,2'-bipyridine and Htppip =2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} were thoroughly investigated in CH3CN and CH3CN/H2O (50:1, v/v) solutions by UV-visible absorption, emission, and NMR spectra. These analyses revealed that RuL acts as an efficient "turn on" emission sensor for H2PO4-, and a "turn off' sensor for F- and OAc-; in addition, RuL exhibited slightly disturbed emission spectra in the presence of the other anions studied (Cl-, Br-, I-, NO3-, and ClO4-). The cation-sensing properties of RuL were also studied in both neat CH3CN and aqueous 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid buffer (pH = 7.2)/CH3CN (71/1, v/v) solutions. RuL was found to exhibit a colorimetric sensing ability that was highly selective for Fe2+, as evidenced by an obvious color change from pale yellow to light red-purple to the naked eye over the other cations studied (Na+, Mg2+, Ba2+, Mn2+, Fe3+, Co2+; Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Ag2+). To obtain insights into the possible binding modes and the sensing mechanisms, 'H NMR spectral analysis, luminescence lifetime measurements, and density functional theoretical calculations were also performed.