2‐(2,2‐Bis‐benzylamino‐1‐cyano‐vinyl)‐benzonitrile: A Selective Turn‐off Fluorescent Cu 2+ Sensor

We report design and synthesis of three 2–(2,2–bis–(alkylamino)–1–cyano–vinyl)benzonitriles and studied their metal ion sensing property. The Cu 2+ ion selectively quenches the fluorescence of 2–(2,2–bis–benzylamino–1–cyano–vinyl)–benzonitrile 4 in acetonitrile. The effect of Cu 2+ ion on the electronic structure of 4 was studied by TD–DFT calculations. The theoretical calculations showed good agreement with the experimental results. The detection limit of Cu 2+ ion from copper nitrate for the 2–(2,2–bis–benzylamino–1–cyano–vinyl)–benzonitrile was upto 0.05 ppm (0.8 µM). The formation of copper complex of 4 was confirmed by HRMS.