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Two bis crown ether receptors were synthesized and tested as host molecules for protonated forms of alkyl amines and amino acid esters. Molecular recognition studies were conducted in CH2Cl2:MeOH (92:8) by spectrophotometric UV/Vis titrations and by spectrometric 1 H NMR titrations in CDCl3. The calculated binding constants are in the range 10 2 -10 5 M -1 . A high affinity for L-amino acid methyl ester derivatives was found. A theoretical study at the DFT level of the synthesized receptor and some analog ligands with three different ammonium ions helps to rationalize the experimentally found trends.

Crown Ether Ditopic Receptors for Ammonium Salts with High Affinity for Amino Acid Ester Salts