Cavity shaped host-guest interaction of distally dialkylated calix[4]arenes with 1-chloro-4(trifluoromethyl)benzene

The conformation of the conic molecular cavity in the `hostʹ properties of 1,3 dialkylated calixarenes were examined by spectrofluorometric and quantum-chemical methods. The size of the `hostʹ molecular cavity was influenced by the nature of substituents in distal position. As model guest molecule, 1-chloro-4-(trifluoromethyl)benzene (BTF) from the pesticide related organic series was chosen. The dependence of the interaction between the neutral molecule and the calixarene on the extent of distorsion in the conformation of `hostʹ cavity was obtained. The `pinched coneʹ conformer of 1,3-substituted calix[4]arenes seems to form a complex with electron-deficient neutral aromatics by predominant pi-pi type in-teraction.