Chiral Recognition of Anions by Fluorescence Tetraamide-Based Receptors Bearing Hydroxy Groups from l-Serine and l-Threonine Residues

Abstract

Abstract Chiral recognition abilities of tetraamide-based receptors 1 and 2 bearing l-serine and l-threonine as recognition sites, respectively, and terminal pyrenyl groups as signaling units for enantiomers of biologically important N-acetyl amino acid tetrabutylammonium salts were studied in acetonitrile. The receptors showed ratiometric fluorescence changes upon the addition of chiral guest anions. The binding constants for amino acid derivatives were in the 104–105 mol−1 dm3 range. The chiral discrimination abilities (K11,D/K11,L) of 1 and 2 were significantly large, for instance K11,D/K11,L for Ac-Leu-O− were found to be 3.9 and 4.6, respectively. The complex structures were evaluated by 1H NMR titrations and DFT calculations implying that the effective hydrogen bond formations by six N-H and O-H groups and a CH-π interaction of the acetyl group of d-enantiomer with a terminal pyrenyl group of the receptor.