Zinc binding-induced near-IR emission from excited-state intramolecular proton transfer of a bis(benzoxazole) derivative

A bis(benzoxazole) derivative with metal-chelating ligand (DPA), Zinhbo-1, exhibits a large fluorescence turn-on effect (up to 10-fold) upon zinc-binding. The metal chelation enables excited state intramolecular proton transfer (ESIPT), giving an additional emission band in the near-IR region (∼710 nm) with a large Stokes shift (ca. 230 nm).