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.
Key indicators: single-crystal X-ray study; T = 295 K; mean (C-C) = 0.006 Å; R factor = 0.059; wR factor = 0.189; data-to-parameter ratio = 15.5.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 octahedral 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 octahedral geometry.
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ExperimentalCrystal data [Cu(C 14
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