A multifunctional bishydroxycoumarin conjugate exhibiting AIE characteristics and tandem Co2+/ATP detection with logic gate operations, on-site sensing and bioimaging applications.

An efficient coumarin-based fluorescent probe, HCPD, was synthesized via condensation of 7-diethylamino-4-hydroxycoumarin aldehyde with o-phenylenediamine. The structure of the probe was confirmed by FT-IR, NMR and HRMS studies. The probe, HCPD exhibited aggregation-induced emission (AIE) characteristics in a THF-water mixture, showing enhanced emission at 80% water fraction. The probe functions as a molecular switch for the sensitive detection of the environmentally and biologically significant metal ion Co2+ at the nanomolar level. HCPD emits green emission at 500 nm which selectively detects Co2+ ions in a DMF/Tris-HCl buffer system (9 : 1, v/v) through an emission "turn-off" response, attributed to paramagnetic quenching. In addition, Job's plot and HRMS analysis established a 1 : 1 binding stoichiometry between HCPD and Co2+ ions. The probe demonstrated remarkable sensitivity with a low detection limit of 11.7 nM and a binding constant of 3.6798 × 104 M-1. Notably, the emission of the HCPD-Co2+ ensemble was restored upon the addition of ATP over various competing anions, enabling reversible sensing behavior not previously reported in the reversibility of Co2+ ions. The regeneration capability of the probe facilitated practical on-site applications, including paper strips, cotton swabs and the construction of an IMPLICATION logic gate circuit. Furthermore, HCPD was also successfully applied in bio-imaging studies of MDA-MB-231 breast cancer cell lines, highlighting its biological relevance. Overall, HCPD represents a highly sensitive and reversible dual-responsive fluorescent probe for Co2+ and ATP detection with significant environmental and biological applications.