Highly Selective Fluorescent Signaling for Al3+in Bispyrenyl Polyether

A series of bispyrenyl-polyether have been synthesized and investigated as a fluorescent chemosensor for metal ions. The results showed that bispyrenyl-polyether system is selective towards Al 3+ ion over other ions tested. In free ligand, excited at 343 nm, it displays a strong excimer emission at around 475 nm with a weak monomer emission at 375 nm. A ratiometry of monomer (375 nm) increase and excimer (475 nm) quenching was shown only when Al 3+ ion is bound to ligand, because two facing pyrene groups form a less efficient overlap of π-π stacking compared with that of free ligand.