AIEE Active Donor–Acceptor–Donor-Based Hexaphenylbenzene Probe for Recognition of Aliphatic and Aromatic Amines

In the present investigation, an intramolecular charge transfer (ICT) and aggregation induced emission enhancement (AIEE) active donor-acceptor-donor (D-A-D) system 5 having fumaronitrile as the acceptor and hexaphenylbenzene (HPB) as the donor moieties joined through rotatable phenyl rings has been designed and synthesized that is highly emissive in the solid state and exhibits stimuli-responsive reversible piezochromic behavior upon grinding and heating. Because of its AIEE characteristics, HPB derivative 5 undergoes aggregation to form fluorescent aggregates in mixed aqueous media that exhibit ratiometric fluorescence response toward aliphatic amines (primary/secondary/tertiary) and turn-off response toward aromatic amines and hence differentiates between them. Further, the solution-coated portable paper strips of derivative 5 showed pronounced and sensitive response toward aromatic and aliphatic amines with a detection limit in the range of picogram and nanogram level, respectively.