Pyridine-Hydrazone-Controlled Cyanide Detection in Aqueous Media and Solid-State: Tuning the Excited-State Intramolecular Proton Transfer (ESIPT) Fluorescence Modulated by Intramolecular NH…Br Hydrogen Bonding
A new efficient pyrdine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique excited-state intramolecular proton transfer (ESIPT) mechanism. The addition of Br group to the fluorophore skeleton at the ortho-position of hydrazone, generates reference compounds (4b-E, 4c-Z). Interestingly, the potential intramolecular NH…Br hydrogen bonding might compete with the anion-induced intermolecular NH…A– hydrogen bonding, resulting in dramatic ESIPT suppression. High emission of the four fluorophores in the solid-state is also investigated. Moreover, probe 4a-E preloaded on test papers, upon cynaide treatment shows obvious changes in color and demonstrates 4a-E as a writable platform. More importantly, it exhibits great potential application for cyanides detection of cyanide-containing food materials and excellent performance in real-word water samples.