A two-photon excited luminescence of water-soluble rhodamine-platinum(II) complex: fluorescent probe specific for Hg2+ detection in live cell

The first example of cyclometalated platinum(II)-containing rhodamine probe (1) with two-photon induced luminescent properties was synthesized and investigated for mercury detection. A highly selective color change of 1, from light yellow to pink, is observed only in the presence of Hg²⁺ due to the formation of 1,3,4-oxadiazole ring in 2. This selectivity of Hg²⁺ with color changes can be observed easily by the naked-eye. Meanwhile, a remarkable turn-on and selective 20-fold fluorescent enhancement of 1 upon binding with Hg²⁺ over the other tested metal ions was observed. The water-soluble probe 1 was successfully applied in the visualizing of the site of Hg²⁺ accumulation as well as estimating of trace amounts of mercury ions in live HeLa cells by two-photon microscopy.