Pseudo-cyclic Face-to-face Rigid Structure Caused by the Intramolecular Ion Pair Effect

Abstract

Six 3-methylpyridine zwitterions and six quinoline zwitterions were synthesized through the reaction of 4-hydroxycoumarins, p-benzoquinone and the corresponding N-aromatics. The novel pseudo-cyclic face-to-face rigid structure of the zwitterion was elucidated by 1H-NMR at different temperatures, and assumed to be caused by both the intramolecular ion pair attraction and the steric interaction.

Keywords

• 4-Hydroxycoumarins
• Zwitterion
• Molecular structure