"Turn-on" fluorescent chemosensor for zinc(II) dipodal ratiometric receptor: application in live cell imaging.

A dipodal ligand 2,2'-((ethane-1,2-diylbis(azanediyl))bis(ethane-1,1-diyl))diphenol was synthesized through a condensation reaction and was characterized with IR, (1)H NMR, (13)C-NMR, and mass spectroscopy. The receptor 2 has shown marked enhancement in fluorescence intensity (emission signal at 341 nm) on binding with Zn(2+) as compared to other surveyed metal ions. The sensor has shown dramatic changes in dual channel fluorescence emission with λmax at 300 and 341 nm. The successive addition of Zn(2+) to the solution of the sensor led to a blue shift of the peak maxima and interestingly upon addition of higher equivalents of Zn(2+) quenched the fluorescence intensity of the sensor, and ultimately the original fluorescent profile of sensor was restored. The structures of 2 and 3 were optimized with B3LYP/LanL2DZ basis sets. The receptor 2 successfully detect the Zn(2+) ion in HeLa cells cultured in Zn(2+) enriched medium.