Molecular modelling study of a dissymmetric calix[4]arene and its methyl ethers

Abstract

A dissymmetric calix[4]arene consisting of four 3,4-dimethylphenol units 1 and its methyl ethers 2–6 have been investigated by applying various force fields as well as by the PM3 semiempirical molecular orbital method. The exploration of the conformational space by random conformational searching has led to numerous local energy minima which differ in the torsion angles around the aryl–methylene bonds. By adjustment of some parameters of the TRIPOS force field a good correspondence could be obtained with experimental data whereas the MM2P force field was not reliable in this respect. Furthermore, a method is proposed for the characterization of calix[4]arenes by a single parameter derived from the torsion angles of the aryl–methylene bonds.