Hindered fluorescence quenching in an insulated molecular wire

Abstract

A [3]rotaxane 2⊂1₂ consisting of an anionic phenylene ethynylene dumbbell 2⁴⁻ threaded through two cationic cyclophanes 1²⁺ has been prepared using aqueous Glaser coupling. Stern–Volmer analysis of the fluorescence quenching using three different electron-acceptors (methyl viologen 13²⁺, dipropyl-4,4′-bipyridinium disulfonate 14 and anthraquinone-2,6-disulfonate 15²⁻) shows that the threaded cyclophanes inhibit electron-transfer from the excited state of the dumbbell by steric shielding, and by electrostatic shielding in the case of methyl viologen.