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

Abstract

A new fluorescent anion receptor containing anthracene and amide moieties has been synthesized to selectively recognize anions via hydrogen bonding and electrostatic interactions. An anthracene-bis-N-acetylglyoxylic amide derivative, namely N,N′-(anthracene-9,10-diylbis(methylene))bis(2-(2-acetamidophenyl)-2-oxoacetamide), was successfully synthesized by reacting of 9,10-diaminomethyl anthracene with N-acetylisatin. An analysis of the anthracene-bis-N-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⁻, HPO₄²⁻, 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-N-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.