An efficient sensor for relay recognition of Zn2+ and Cu2+ through fluorescence ‘off–on–off’ functionality

A new bis(8-carboxamidoquinoline) dangled binaphthol derivatized fluorescent sensor (L) was designed and synthesized. L behaves ratiometric response to Zn2+ with high selectivity accompanied by remarkable emission enhancement and red shift. The resultant L–Zn2+ complex can act as a Cu2+ sensing probe with fluorescence quenching behavior through direct Zn2+ ion replacement. Furthermore, the binding modes of Zn2+ and Cu2+ with L are elucidated by X-ray crystallographic analysis, respectively.