Pyrenyl benzimidazole-isoquinolinones: Aggregation-induced emission enhancement property and application as TNT fluorescent sensor

Three new pyrene-substituted benzimidazole-isoquinolinones (2-4) which are different in the positions and numbers of the pyrene groups are designed and synthesized via imidation-condensation reaction and Suzuki coupling. The structural elucidations are performed using standard spectroscopic techniques and computational calculations. These compounds exhibit interesting aggregation-induced emission enhancement (AIEE) in highly aqueous THF media and selective fluorescent quenching toward trinitrotoluene (TNT). The compound with two pyrene units (4) has the best selectivity toward TNT and has a quenching efficiencies (Ksv) of 6.0 × 104 M−1, which leads to the estimation of the detection limit of 0.25 ppm TNT. The paper-based sensors prepared from 4 can readily detect TNT in aqueous media by naked-eye observation at the concentration as low as 50 μM. It can also detect TNT vapor in closed chamber within 5 min of exposure at room temperature.