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

Abstract

Optical sensing of F −, Cl −, Br −, I −, OAc −, H 2 PO 4 - , NO 3 - , and ClO 4 - 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 H 2 PO 4 - 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 −, NO 3 - and ClO 4 - in DMSO solutions. Luminescent F − sensing in DMSO/H 2O (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.