D-π-A azine based AIEgen with solvent dependent response towards a nerve agent

We developed a D-pi-A based unsymmetrical azine molecule 4-((E)-((E)-(4-(dipropylamino)benzylidene)hydrazono)methyl)benzonitrile [DPBN] and studied its optical and aggregation induced emission properties. TheDPBNmolecule shows good aggregation induced emission (AIE) behaviour with 1157-fold fluorescence enhancement in the aggregated state. In addition to that, both colorimetric as well as fluorometric sensing studies revealed thatDPBNselectively detects diethylchlorophosphate (DCP), a potent nerve agent. Interestingly,DPBNshows solvent dependent optical output in the presence ofDCPviatwo different mechanisms. In the monomer state, it shows red shifted fluorescence enhancement along with color change from colorless to orange colorviathe formation of a new intramolecular charge transfer state in pure tetrahydrofuran (THF). In the aggregated state,DPBNshows blue shifted emission with fluorescence enhancement in THF-water mixture by protonation at the amine nitrogen centre. Thus,DPBNcan be used as a diagnostic measure to selectively detect nerve agents likeDCP. This study also paves the way for further development of molecular probes for nerve agents that would represent immense implications in various fields of chemistry and biology.