Mechanical Interlocking of 144 Symmetrical 19F and Tetraphenylethylene for Magnetic Resonance-Fluorescence Dual Imaging

Single-molecule dual 19F magnetic resonance imaging (19F MRI) and fluorescence imaging (FLI) agents are valuable tools in biomedical research. However, integrating millimolar-sensitivity 19F MRI and micromolar-sensitivity FLI into a single molecule remains challenging. Here, we report the use of mechanically interlocked [5]rotaxanes to efficiently incorporate 144 symmetrical fluorines (19F) for sensitive 19F MRI and to control the motion of tetraphenylethylene (TPE) for responsive FLI at the molecular level, yielding a dual imaging agent with micromolar sensitivity. The sensitivity gap between 19F MRI and FLI is bridged by generating an intense singlet 19F peak from 144 symmetrical 19F and modulating their motion through mechanical interlocking. Spectroscopic and imaging studies, in conjunction with molecular dynamics simulations, highlight the critical role of [5]rotaxane formation, wheel “stationing-shuttling”, and the introduction of fluorous bulky perfluoro-tert-butoxymethyl (PFBM) groups as effective strategies to improve 19F MRI sensitivity and enable responsive FLI. This work not only advances the development of high-performance dual imaging agents but also provides valuable insights into the structure, dynamics, and potential applications of [5]rotaxanes in materials science.