Ab initio study of conformers of p-tert-butylcalix[4]crown-6-ether complexed with alkyl ammonium cations

Abstract

The structures and energies of p-tert-butylcalix[4]crown-6-ether (1) in various conformers and their alkyl ammonium complexes have been calculated by ab initio HF/6-31G quantum mechanics method. We have tried to obtain the relative affinity of partial-cone and 1,3-alternate conformers of 1 for alkyl ammonium guests by comparison with its cone-shaped analogue. We have also calculated the relative complexation efficiency of these host-guest complexes focusing on the binding sites of crown-6-ether moiety or benzene-rings pocket of the host molecule 1. These calculations revealed that the crown moiety has better complexation efficiency than upper rim part of calix[4]arene that is in similar trend to the cone-shaped complexes.