A novel switchable [2]rotaxane driven by light energy with Rhodamine B as a stopper

Over the past few decades, bistable [2]rotaxanes have been extensively studied because of their applications in molecular switches. In this paper, a rotaxane molecule containing a dibenzo-24-crown-8 ring and Rhodamine B units was synthesized and characterized by 1 H NMR and HRMS. The Rhodamine B component allows the fluorophore fluorescence to be manipulated in alternate modes by varying the pH of the solution under irradiation. Because of the easy regulation and high sensitivity of the changes in fluorophore fluorescence, Rhodamine B [2]rotaxane can be used as a molecular switch, with different pH values as the input and changes in the fluorescence intensity as the output signals.