Selective colorimetric sensing of fluoride ion and its use for insitu cyclization of the sensor

• A colorimetric and naked-eye selective F− ion sensor.
• Sensor’s crystal structure shows the existence of keto form rather than enol.
• The crystal lattice of the sensor shows π…π stacking interactions.
• Insitu cyclisation of sensor to a benzimidazole derivative by fluoride.

Sensor 1 (a Schiff base) obtained by the condensation of 4-nitro-o-phenyldiamine and 2-hydroxy-1-naphthaldehyde can detect fluoride ion selectively through visual color change. Moreover, insitu cyclisation of sensor 1 to benzimidazole derivative 2 takes place by the help of fluoride ion as evidenced by X-ray crystal structure. The crystal structures of the sensor 1 and benzimidazole derivative 2 show that several types of weak C–H…X (X = O, N), C–H…π and π…π interactions play a crucial role along with intra/inter molecular H-bonding interactions for the stabilization of crystal lattice.

The sensor 1 can detect fluoride ion selectively through visual color change. Moreover, insitu cyclization of sensor 1 to benzimidazole derivative 2 takes place by fluoride ion as evidenced by X-ray crystal structure.Figure optionsDownload as PowerPoint slide