Noncovalent Interaction-Based Probe Design for PET-Facilitated Fluorescence Sensing of Synthetic Cannabinoids

Due to the structural diversity and rapid iteration of synthetic cannabinoids (SCs), their detection presents a challenging issue. Here, based on the structure and physicochemical property analysis of a typical SC, MDMB-CHMICA, four fluorescent probes were designed by introducing the recognition groups and fluorescence regulation groups on carbazole. It is found that the electron-withdrawing and conjugation-extending effect of the nitro group reduced the LUMO energy level and thereby narrowed the HOMO-LUMO energy gap, resulting in a red-shift of the fluorescence emission. As a result, the intramolecular charge transfer mechanism of the probe helps to lead to stronger fluorescence with a greater charge transfer distance. Two probes with stronger fluorescence show multiple noncovalent interactions with MDMB-CHMICA and efficient fluorescence quenching sensing through photoinduced electron transfer. This study is expected to shed light on the exploration of fluorescent probes from the analytes' physicochemical nature and would be helpful for new psychoactive substance detection.