Modulation of Lanthanide Luminescence with the Mechanical Bond: Antenna‐Emitter Confinement in a Compact [2]Rotaxane

Abstract

Abstract Luminescent emitters based on lanthanide ions are of ubiquitous importance in the biological sciences, but typically need sensitization from a covalently attached adjacent chromophore – an “antenna” – to have suitable emission intensities. Here we show that the mechanical bond can be used to connect the antenna to the emitter, providing dynamic features and stimuli‐responsiveness to the resulting assemblies. We outline a strategy to synthesize [2]rotaxanes capped with strong chelating groups, and establish that post‐functionalization of the interlocked scaffold by lanthanide ion insertion is modular, high‐yielding and straightforward. Photophysical studies revealed effective antenna‐emitter energy transfer within the [2]rotaxane, and the sensitization mechanism as well as ring‐thread dynamics were studied with spectroscopic and computational methods. The rotaxane was shown to have high selectivity toward Cu(II) ions, acting as an efficient turn‐off sensor. This study validates the mechanical bond as a conjugation method between antennas and emitters, yielding otherwise hard‐to‐access and beneficial features to the resulting molecular systems.