N-acetylglyoxylic amide bearing a nitrophenyl group as anion receptors: NMR and X-ray investigations on anion binding and selectivity

摘要

N-Nitrophenylglyoxylic amides 1 and 2 in presence of tetrabutylammonium cation (TBA) act as receptors for anions HSO4-, Cl-, Br- and NO3- as investigated by NMR studies. The receptors formed 1:1 host-guest complexes in solution. X-ray structure of 1 along with TBA that bind a chloride anion is reported. Molecule I showed the highest selectivity for HSO4- anion over others measured. X-ray structure of the bound Cl- revealed a pocket containing the anion making strong (N-H center dot center dot center dot Cl) and weak hydrogen bonds (C-H center dot center dot center dot CI) that contribute to the recognition of the chloride anion. N-H and C-H hydrogen bonds resulted in a relatively strong binding for chloride ions. (C) 2017 Elsevier B.V. All rights reserved.