Two birds with one stone: multifunctional and highly selective fluorescent probe for distinguishing Zn2+ from Cd2+ and selective recognition of sulfide anion.

A coumarin-based multifunctional fluorescent sensor containing a di-2-picolylamine (DPA) moiety (1) was presented. Interestingly, this probe could similarly act as ON-OFF type fluorescent sensor for Co(2+) and Cu(2+), then in situ generated 1-Co(II) and 1-Cu(II) ensembles could further serve as OFF-ON type fluorescent sensors to achieve the discrimination of Zn(2+) from Cd(2+) and selective recognition of sulfide anion in aqueous solution via displacement approach, respectively. Specially, 1-Cu(II) could permeate the cell membrane and could be used in fluorescence imaging of S(2-) in living biological samples. These ON-OFF-ON type fluorescent sensors exhibited high selectivity and sensitivity towards the targets.