Specific optical signalling of anions via intramolecular charge transfer pathway based on acridinedione fluorophore

We present a simple but highly specific acridinedione fluorophore (ADD-1) that acts both as a fluorescent and colorimetric sensor for anions in acetonitrile. The specific optical signalling of ADD-1 is due to the formation of new distinct intramolecular charge transfer (ICT) emitting states in the presence of AcO− (490 nm), H2PO4− (440 nm), and F− (510 nm) over other anions. Presence of F− shows a colour change that is perceptible to the naked eye, from colourless to an intense fluorescent green due to the deprotonation of acridinedione ring amino hydrogen.