Rational design and synthesis of Y-shaped fluorophores with multifarious emission properties and their application in the sensitive detection of PA

Four new Y-shaped D-pi-A compounds3a-3dwith an aryl acetylene moiety bearing two benzothiazole branches were concisely synthesized in two steps. Their photophysical properties in solution and powder states have been investigated and further confirmedviatheoretical calculations. All compounds3a-3dshow strong solid-state fluorescence, aggregation induced emission and near-infrared fluorescence. And, as anticipated, the modulation of the substituent on the aryl acetylene unit can largely affect the charge density of molecules as well as their fluorescence properties. Noteworthily, compound3bwith methoxy as an electron-donating group presents significant solvatochromism because of its obvious intramolecular charge transfer effect. In addition, compounds3a-3din the aggregated state (H2O/THF, v/v, 9/1) can be developed as a near-infrared fluorescent probe for picric acid (PA). Their limits of detection have been found to be 3.1 x 10(-7), 6.1 x 10(-8), 3.3 x 10(-7)and 4.6 x 10(-7)M, respectively. Among them,3bis the best design. Based on the results of(1)H NMR, SEM, DLS, lifetime and DFT calculations, aggregation caused quenching and photoinduced electron transfer have been revealed to be responsible for the quenching mechanism of detecting PA. Importantly, probe3bhas also been successfully used to detect PA not only in real water samples with interferences, but also on3b-coated Whatman filter paper strips.