A Mechanochromic Rotaxane that Releases Azetidine-Trityl-Maleimide, a Versatile Fluorescent Probe

Force sensing at the molecular level has enabled the study of materials failure and it offers great promises for the investigation of mechanobiological processes. Traditional force probes rely on the reversible or irreversible activation of mechanochromic precursors to assess transient or permanent changes in polymer networks. A promising approach involves force-controlled release of sensing molecules, as the accumulation of chromic molecules at specific sites would enable the recording of deformation histories. However, many fluorescent probes are limited by environmental sensitivity, specific release conditions, or low release efficiency. Maleimide-based dyes, especially amino maleimides, offer a robust alternative due to their small size, structural versatility, and tuneable fluorescence properties. Here, we present a mechanochromic rotaxane device that releases an azetidine-trityl-maleimide (ATM) fluorescent probe via a retro-[4+2] cycloaddition reaction. ATM is a rigidochromic, chemically stable, and environmentally insensitive probe, generated exclusively through rotaxane actuation, underscoring the unique mechanochemical properties of rotaxanes. This device holds potential for applications in material science and biology, such as the investigation of polymer networks and active tissues.