Seven‐Component Domino Synthesis of Quinolino[7,8‐j][1,7]phenanthrolines: Fluorescent Sensors for Selective Picric Acid Detection and Live‐Cell Imaging

Abstract

AbstractIn this study, a novel seven‐component, higher‐order reaction has been developed to synthesize quinolino[7,8‐j][1,7]phenanthrolines via a one‐pot, solvent‐free domino process. The reaction, involving acridine‐1,8‐dione, 2 equiv. each of aromatic aldehydes, malononitrile, and ammonium acetate, proceeded efficiently under microwave irradiation at 110 °C for just 3 min. This transformation forms eight new bonds in a single step, offering a high atom economy and excellent yields. The resulting quinolino[7,8‐j][1,7]phenanthroline derivatives NAD, CAD, MAD, and OAD exhibited strong fluorescence under UV light in solution. Notably, all four compounds demonstrated high selectivity and sensitivity as picric acid (PA) sensors, with detection limits in the nanomolar range (NAD: 79 nM, CAD: 98 nM, MAD: 63 nM, OAD: 59 nM). These probes were also successfully integrated into test strips for potential on‐site PA detection. Cytotoxicity studies revealed significant activity of NAD against A549 lung cancer cells and N9 microglial cells, with IC₅₀ values of 70.71 and 99.62 µg/mL, respectively. Furthermore, bioimaging experiments confirmed that NAD effectively detects PA within A549 and N9 cells, highlighting its potential for biomedical sensing applications.