Formation of Molecular Complexes with Calixarenes as Detected by Induced Circular Dichroism

Article abstract of DOI:10.1246/bcsj.64.1896

Calixarenes (n=4 and 6) bearing (S)-5-oxo-2-pyrrolidinylcarbonyloxyl groups on the lower rim were synthesized.In chloroform, the hexamer bearing six (S)-5-oxo-2-pyrrolidinylcarbonyloxyl groups could "bind" ferrocenecarboxylic acid through hydrogen-bonding interactions, the complexation being conveniently detected by induced circular dichroism (ICD) spectroscopy (λ_max 445 nm).On the basis of the examination of acyclic reference compounds, the appearance of the ICD band was explained as such that one pyrrolidone unit acts as a binding site and the chiral center in the neighboring pyrrolidone unit affects the transition moments in the ferrocene ?-system.The association constant for the 1:1 complex was estimated to be 680 M^-1.This is a new, convenient method for detecting the formation of molecular complexes with calixarenes in organic media.