Design and application of a water-soluble phosphorescent Ru(ii) complex as turn-on sensing material for Hg²

A novel phosphorescent chemodosimeter material Ruphen-1 based on a Ru(ii) complex has been designed and developed by introducing Hg²⁺-promoted desulfurization and intramolecular cyclic guanylation of thiourea reaction into the luminophor. Ruphen-1 not only possessed a longer excitation wavelength, large Stokes shift and good water solubility, but also exhibited high selectivity and sensitivity only toward Hg²⁺ with a rapid turn-on phosphorescence response in an aqueous system over a wide range of pH (4.0-9.0). The detection limit for Hg²⁺ could reach 5.4 nM under physiological conditions (pH 7.2). The spectral response mechanism and structure changes of the chemodosimeter have been analyzed in detail through theoretical calculations and ESI-MS. Furthermore, by investigating the change in the phosphorescence lifetime of the chemodosimeter and employing the time-resolved emission spectra method, Ruphen-1 could effectively eliminate the interference of background fluorescence and further improve Hg²⁺ detection accuracy. Finally, Ruphen-1 showed low cytotoxicity toward living cells through the MTT assay, and exhibited potential applications in the detection and monitoring of the distribution of Hg²⁺ in living cells with notable phosphorescence enhancement by confocal luminescence imaging.