Reaction-based colorimetric and ratiometric fluorescence sensor for detection of cyanide in aqueous media.

A stilbene-based compound (1) has been prepared and was highly selective for the detection of cyanide anion in aqueous media even in the presence of other anions, such as F(-), Cl(-), Br(-), I(-), ClO(4)(-), H(2)PO(4)(-), HSO(4)(-), NO(3)(-), and CH(3)CO(2)(-). A noticeable change in the color of the solution, along with a prominent fluorescence enhancement, was observed upon the addition of cyanide. The color change was observed upon the nucleophilic addition of the cyanide anion to the electron-deficient cyanoacrylate group of 1. The spectral changes induced by the reaction were analyzed by comparison with two model compounds, such as compound 2 with dimethyl substituents and compound 3 without a cyanoacrylate group. An intramolecular charge-transfer (ICT) mechanism played a key role in the sensing properties, and the mechanism was supported by DFT/TDDFT calculations.

{N'-[1-(2-Pyrid-yl)ethyl-idene-κN]benzo-hydrazidato-κN',O}{N'-[1-(2-pyrid-yl)ethyl-idene-κN]benzohydrazide-κN',O}copper(II) trichloro-acetate.

In the title complex, [Cu(C(14)H(13)N(3)O)(C(14)H(12)N(3)O)](CCl(3)COO), the central Cu(II) ion exhibits a distorted octa-hedral geometry with the two ligands coordinating in an meridional format. The N(4)O(2) ligand environment is defined by two benzoyl O atoms, two pyridyl N atoms and imino N atoms. As evidenced by the bond lengths, the two benzohydrazone ligands exist in distinctively different forms, one of them as a regular neutral ligand and the other as an anionic enolate arising from deprotonation. The much longer Cu-O bond and longer Cu-N bond lengths in the neutral benzohydrazone ligand imply weak ligation in comparison with the anionic enolate form. The acute angles of the five-membered rings cause a significant deviation from a regular octa-hedral geometry.