A Photochromic Fluorescent Probe for Hg2+ Based on Dithienylethene-Rhodamine B Dyad and Its Application in Live Cells Imaging

A new photoswitchable fluorescent molecular probe based on photochromic dithienylethene-rhodamine B dyad was designed and synthesized successfully. The dithienylethene-rhodamine B dyad exhibited excellent photochromism with reversible color changes upon photo-irradiation. Upon addition of Hg2+, its color changed from colorless to red, and its fluorescence was remarkably enhanced; whereas, other ions including K+, Na+, Ag+, Ca2+, Mg2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Mn2+, Pb2+, Ni2+, Fe3+, Al3+, and Cr3+ induced basically no colorimetric and fluorescent color changes, which constituted a highly selective and sensitive fluorescent probe toward Hg2+. In addition, it exhibits unique fluorescent switching characteristics that can be controlled by Hg2+ and light stimuli. More importantly, by means of cells imaging experiments, it is demonstrated that this probe can enter living cells as a Hg2+ detector and respond to light stimuli, which shows its value for potential application in biological systems.