New applications of ruthenium solar cell sensitizers N3 and N719 as luminescence turn-on anion sensors

Optical sensing of F−, Cl−, Br−, I−, OAc−, View the MathML sourceH2PO4-, View the MathML sourceNO3-, and View the MathML sourceClO4- by cis -dithiocyanatobis(2,2′-bipyridyl-4,4′-dicarboxylic acid)ruthenium(II) (N3) and bis(tetrabutylammonium) cis -dithiocyanatobis(2,2′-bipyridine-4-COOH,4′-COO−)ruthenium(II) (N719) have been investigated in dimethyl sulfoxide (DMSO), by means of UV–Vis absorption and emission spectrophotometric titrations. Additions of F−, OAc−, and View the MathML sourceH2PO4- in DMSO solution caused obvious UV–Vis spectral changes with appearance of several isosbestic points, and remarkable emission enhancements along with large blue shifts in emission bands. The values of F−-induced emission intensity enhancement factor (emission quantum yield enhancement factor), I /I 0 (φ /φ 0), were found to be 40 (86) and 38 (58) for N3 and N719, respectively. No obvious spectral changes were observed upon addition of Cl−, Br−, I−, View the MathML sourceNO3- and View the MathML sourceClO4- in DMSO solutions. Luminescent F− sensing in DMSO/H2O (4:1, v/v) has also been demonstrated to be operative with a luminescence enhancement factor of 12, indicating that N3 is very potential for practical application as fluorescent anion sensor in aqueous solution. An interaction mechanism of anion-induced deprotonation of N3 and N719 was confirmed, and the deprotonation reaction equilibrium constants of N3 and N719 were derived as well.