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

Single-molecule dual 19 F magnetic resonance imaging ( 19 F MRI) and fluorescence imaging (FLI) agents are valuable tools in biomedical research. However, integrating millimolar-sensitivity 19 F 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 ( 19 F) for sensitive 19 F 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 19 F MRI and FLI is bridged by generating an intense singlet 19 F peak from 144 symmetrical 19 F 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 19 F 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.