A selective turn-on fluorescent sensor for Cu(II) and its application in imaging in living cells

A novel fluorescent sensor 4-((E)-(N-(rhodamine-6G)lactam-ethylenediamineimino)methyl)benzene-1,3-diol (1), which has a unique spirolactam ring formation, show a reversible, selective, and sensitive fluorescence enhancement response to Cu(II) at biological pH value for practical use. Also, the selectivity of this system for Cu(II) over other metal ions is remarkably high, and its sensitivity is below 2 ppb in methanol solutions. Furthermore, its high cell permeability grants the access to employ 1 as Cu(II) detector in living cells.