Conformational isomerism in the solid-state structures of tetracaine and tamoxifen with para-sulphonato-calix[4]arene

The solid-state complexes between para-sulphonato-calix[4]arene and the drugs tamoxifen and tetracaine show an unusual 4:1 guest-host stoichiometry with formation of hydrophobic layer of drug molecules held between bilayers of para-sulphonato-calix[4]arene. In both structures each of the four independent drug molecules adopts different conformation due to the different mode of interaction with the anionic host, the neighbouring drug cations and water molecules. (C) 2009 Elsevier B.V. All rights reserved.