A ratiometric and exclusively selective CuII fluorescent probe based on internal charge transfer (ICT)

A new ratiometric and exclusively selective fluorescent probe N-butyl-4,5-di[N-(phenyl)-2-(amino)-acetamino]-1,8-naphthalimide (1) was designed and synthesized on the basis of the mechanism of internal charge transfer (ICT). The probe 1 showed exclusively selectivity for CuII in the presence of a variety of other metal ions in aqueous ethanol solutions and the binding mode of probe 1 with CuII was 1:1 metal–ligand complex. Fluorescent emission spectra of probe 1 in the presence of CuII showed a 50 nm blue shift, which is from 521 nm to 471 nm. Furthermore, probe 1 shows the same fluorescent change with the CuII in living cells.