Synthesis, spectroscopic studies and computational modelling of anthracene-bis- <i>N</i> -acetylglyoxylic amide derivative for anion recognition

A new fluorescent anion receptor containing anthracene and amide moieties has been synthesized to selectively recognize anions <i>via</i> hydrogen bonding and electrostatic interactions. An anthracene-bis-<i>N</i>-acetylglyoxylic amide derivative, namely <i>N</i>,<i>N</i>'-(anthracene-9,10-diylbis(methylene))bis(2-(2-acetamidophenyl)-2-oxoacetamide), was successfully synthesized by reacting of 9,10-diaminomethyl anthracene with <i>N</i>-acetylisatin. An analysis of the anthracene-bis-<i>N</i>-acetylglyoxyl amide derivative's interaction with anions revealed that it recognized CN^-, F^-, and H₂PO₄ ^- more selectively than other anions studied, such as Cl^-, NO₂ ^-, HPO₄ ^2-, HSO₄ ^-, and ClO₄ ^-. As shown by ¹H NMR spectroscopy data, the addition of CN^- and F^- caused the receptor to deprotonate, and that intermolecular hydrogen bonding led to the complex formation between the receptor and H₂PO₄ ^-. Based on the UV-Vis spectroscopy data, the synthesized compound's binding site and the anthracene fluorophore did not show any noticeable ground-state interactions, after adding anions. The fluorescence data revealed that the CN^-, F^-, and H₂PO₄ ^- addition caused in an enhancement of fluorescence intensity, suggesting that the anion caused the anthracene-bis-<i>N</i>-acetylglyoxylic amide to become more rigid. Using DFT approximation, the positive surface of the molecules was identified as the most potential area for interaction with the F^- anion. Additionally, the more intense blue gradient of the non-covalent interaction spectra indicates a tendency for hydrogen bond-type interactions.