A new ditopic ratiometric receptor for detecting zinc and fluoride ions in living cells.

The synthesis, characterization and ion binding properties of a new ditopic ratiometric receptor (1), based on 2-(4,5-dihydro-1H-imidazol-2-yl)phenol and crown ether moieties, have been described. The ditopic ratiometric receptor has been studied in sensing both F− and Zn2+ ions, exhibiting different fluorescent colour changes from cyan green to blue/black observable by the naked eye under UV-light. The addition of Zn2+ to the solution of 1 induced the formation of a 2 : 2 ligand–metal complex 1–Zn2+, which displays a remarkable blue shift of the emission maxima of 1 from 455 nm to 400 nm due to the inhibition of excited-state intramolecular proton transfer (ESIPT) mechanism. The sensing processes were monitored by fluorescence/absorption titrations, and further confirmed by Job's plot and 1H NMR titrations. The crystal structure of 1–Zn2+ reveals that 1 binds Zn2+ in four-coordinated modes. Furthermore, 1 is cell permeable and may be applied to detect trace Zn2+ and F− during the development of a living organism. [ABSTRACT FROM AUTHOR]