Fluorescence-On Response via CB7 Binding to Viologen–Dye Pseudorotaxanes

Fluorescence-on sensors typically rely on disrupting photoinduced electron transfer quenching of the excited state through binding the electron donor. To provide a more general fluorescence-on signaling unit, a quencher–fluorophore dyad has been developed in which quenching by electron transfer to a tethered viologen acceptor can be disrupted through complexation of the viologen by cucurbit[7]uril (CB7). Dyads of benzyl viologen–rhodamine B or a BODIPY fluorophore gave upon CB7 complexation 14- and 30-fold fluorescence enhancement, respectively.