LAUSR

A novel p-azacrown[N,S,O]-styryl-modified boron-phenylpyrrin compound synchronously possessing a diethylamino receptor (C-BPP-A) has been designed and synthesized. Systematic optical studies show that C-BPP-A displays a distinct two-step fluorescence response to the increasing quantity of Cu2+ along with the sequential transition from free ligand (L) to 1:1 (ML) and 2:1 (M2L) complexes: Cu2+ ions added (0-1 equiv.) are first coordinated with the p-azacrown[N,S,O] moiety of C-BPP-A, forming the 1:1 Cu2+-C-BPP-A complex and leading to the significant enhancement in fluorescence emission at 621 nm. Subsequently, the N atom of the diethylamino group from the Cu2+-C-BPP-A complex coordinates with the Cu2+ added (1-2 equiv.), forming a M2L type of complex, which induces the fluorescence quenching of the 1:1 Cu2+-C-BPP-A complex at 621 nm. Meanwhile, successive increase in Cu2+ added from 0 to 1 and 1 to 2 equiv. also induces the increase in the two absorption band ratio I530/I603 in a gradual and then fast trend, respectively, accompanied by an obvious change in the solution colour from blue to violet and then to purple. These results endow C-BPP-A the first highly sensitive colorimetric, fluorescent OFF-ON-OFF, and absorption-ratiometric sensor for quantitative Cu2+-detection.