Behavior of Metacrownophanes at Alkali Metal Cation Transport

Abstract

Metacrownophanes (2) (with two methoxyl groups on the aromatic nuclei) and (3) were conveniently prepared by means of intramolecular [2+2] photocycloaddition of styrene derivatives in acetonitrile. It was suggested from the examination of ¹H-NMR spectra that the syn-conformation of the simple metacrownophane ( 3) became predominant in the presence of alkali metal salts in contrast to ( 2 ) that had anti-conformation (Table 1). When they were used as carriers for alkali metal cations with dodecanoic acid in chloroform membrane systems, crownophane ( 3 ) showed higher efficiency (especially toward Li⁺ ion) than that of (2) (Table 2), indicating its smooth conformational change between syn- and anti-form.