A Ferrocene-Functionalized [2]Rotaxane with Two Fluorophores as Stoppers

In the past few decades, bistable [2]rotaxanes have been extensively studied because of their applications in the fields of functional molecules and molecular machines. In this paper, a di-ferrocene-functionalized [2]rotaxane with two fluorophores as stoppers was designed, prepared, and studied. In this bistable [2]rotaxane, a dibenzo-24-crown-8 macrocycle functionalized with two ferrocene moieties as electron donors can reversibly shuttle between two distinct stations, namely, a dialkylammonium recognition site and a N-methyltriazolium recognition site, by external acid-base stimuli, which has been demonstrated using (1)H NMR spectroscopy. It has been shown that, by introducing two ferrocene units into the macrocycle component, the fluorescence of two fluorescent stoppers, namely, the anthracene fluorophore and the 4-morpholin-naphthalimide fluorophore, can be changed in an alternate mode by an adjustable, distance-dependent photoinduced electron transfer process that occurs between the ferrocene electron donors and each of the two fluorophores.