B-N Coordination-Triggered LE-State Enhancement: A Blue-Shifted Ratiometric Fluorescent Probe for Reversible...

Methamphetamine (MA), a highly potent synthetic illicit drug, poses grave threats to the global public health and societal stability. However, on-site fluorescence detection to MA (particularly those operating in the visible range─remain scarce). In this work, a boron-based ratiometric fluorescent probe, BA-FO-BA, synthesized by covalently conjugating a triarylborane derivative with fluorene is presented. Upon exposure to methylphenethylamine (MPEA, an MA simulant), the probe exhibits a 70 nm blue shift, significant fluorescence enhancement, and rapid and reversible response, accompanied by a distinct visible emission color change from blue to deep purple. This response is also validated using confiscated MA samples. Moreover, a sensing mechanism driven by B-N coordination-induced enhancement of the intramolecular locally excited (LE) state is proposed and substantiated. Therefore, this study not only introduces a novel molecular design strategy for amine detection characterized by a rare blue-shift response but also provides a new pathway for developing the ratiometric fluorescent probe featured LE properties.