Metal ion induced FRET On-Off in naphthyl-pyrenyl pendent tetrahomodioxacalix[4]arene

A novel tetrahomodioxacalix[4]arene (7) bearing both naphthyl- and pyrenyl-amide pendants was synthesized as FRET-based fluorometric sensor for Cu2+ ion. Intramolecular FRET from the naphthalene emission to the pyrene absorption affords Cu2+ ion selectivity over other metal ions. Upon addition of Cu2+ ion, the complex solution of 7 gave a significantly decreased pyrene acceptor emission along with an enhancement of naphthalene donor emission via FRET On-Off event.