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

Optical sensing of F−, Cl−, Br−, I−, OAc−, H2PO4-, NO3-, and ClO4- 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 H2PO4- 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/I0 (φ/φ0), 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−, NO3- and ClO4- 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.

Graphical abstractN3 and N719 have been demonstrated to act as sensitive luminescence turn-on type anion sensors via a deprotonation mechanism. Large luminescent intensity (quantum yield) enhancement factors of 40 (86) for N3, and 38 (58) for N719 have been observed.Figure optionsDownload full-size imageDownload as PowerPoint slide