Oxo-spirocyclic structure bridged ditopic Schiff base: A turn-on fluorescent probe for selective recognition of Zn(II) and its application in biosensing

A novel oxo-spirocyclic structure bridged ditopic Schiff base fluorescent probe L has been successfully synthesized and characterized. Interestingly, probe L exhibits a specific turn-on response to zinc(II) ion in fluorescence with a high selectivity and sensitivity. Further study show that probe L could be applied in imaging of live cells for sensing zinc(II) ion. By contrast, those compounds (L1, L2, and L3) with very similar structure to L lack this properties. The fluorescence intensity of L increases with Zn2+, which is less affected by other metal ions. The binding property of L with Zn2+ was studied by a combination of technologies, such as Job's plot, H-1 NMR, ESI-MS, and DFT calculations. Moreover, we have successfully applied the probe L to detect Zn2+ in cancer cell. We are anticipating that this new oxo-spirocyclic structure bridged ditopic Schiff base may provide a new idea for the design of fluorescent probe.