Exploring the sensing mechanism in a dual-mode fluorescent probe responding to tryptamine and fluoride ions

The detecting mechanism in a dual-mode fluorescent probe PYNA sensing to tryptamine and fluoride ions has been explored by theoretical methods. The excited state intra-molecular proton transfer (ESIPT) process was investigated through analyzing excited hydrogen bonding changes, potential energy curves, frontier molecular orbitals and the charge density redistribution. Meanwhile, the excited state behaviors of PYNA-F, which is the product of PYNA reacting with fluoride ions, are analyzed to demonstrate the fluorescence detecting mechanism of PYNA for fluoride ions. The experimental new absorption peak of 480 nm has been assigned to the absorption of the anion form of PYNA.