An isoquinoline as cation assisted ON–OFF–ON fluorescence switch with methionine and fluoride ion

Basic Al2O3–Cu(OTf)2 acts as an efficient heterogeneous catalyst for the one step synthesis of 1-amino-3-aryl isoquinoline (IQ) from tricyanomesitylene. This IQ shows fluorescence ON–OFF–ON molecular switch to fluoride ion, Brønsted–Lowry bases (amines) in the presence of H+, and also selective to methionine with Hg2+ in an analogous manner.