Cyclic Dipeptide-Guided Aggregation-Induced Emission of Naphthalimide and Its Application for the Detection of Phenolic Drugs

The development of novel aggregation-induced emission-based fluorophoric systems (AIEgens) has gained prominent importance in recent years, owing to their wide range of applications. Herein, we demonstrate the design, syntheses, and molecular architectonics of cyclic dipeptide tethered naphthalimides (CDP-NIs) to evaluate their AIEgenic properties and applications. CDPs are versatile molecular auxiliaries that form robust intermolecular hydrogen bonding and are tethered to naphthalic anhydride with the ACQ (aggregation-caused quenching) feature. The introduction of a CDP auxiliary was anticipated to promote the molecular assembly of the resulting naphthalimide product to form AIE-active aggregates through intermolecular hydrogen bonding in aqueous media. The systematic photophysical studies of CDP-naphthalimide (CDP-NI) conjugates led to the identification of two AIEgenic fluorophores. The AIEgenic property of the lead candidate 4a was employed for the detection of phenolic drugs in aqueous media. In particular, modulation of the AIEgenic property of 4a offered the sensitive detection of drugs such as doxorubicin and rifampicin (LOD = 18 nM/9.7 ppb and 202 nM/164 ppb, respectively).