Functionalized Adenine-Based Receptors for Monocarboxylic Acids’ Recognition

: Three receptors 1-3, built on adenine, have been synthesized, structurally characterized, and successfully employed for the recognition of monocarboxylic acids. The adenine-based receptors 1-3 have been found to bind monocarboxylic acids via the Hoogsteen (HG) binding site or the Watson-Crick (WC) binding site and form 1:1 complexes in CHCl3. Detailed binding of the receptors 1-3, in the presence of the monocarboxylic acids, corroborates that there is a distinct propensity of the HG site for aromatic carboxylic acids, for example, (S)-mandelic acid and benzoic acid. Aliphatic acids, for example, propanoic acid and rac-lactic acid, on the other hand, prefer to bind at the WC site. The monocarboxylic acid bindings to 1-3 were examined by UV–Vis, fluorescence, and 1 H NMR spectroscopic methods, and DFT study.