The calix [4] tube family of ionophores has been extended to encompass the
slightly larger thiacalix [4] tube. H-1 NMR and crystallographic studies sh
ow the ligand to adopt a flexible C-2v flattened cone arrangement. However,
in contrast to the parent calix [4] tube, preliminary binding studies show
no selectivity for potassium, in agreement with the absence of a template
effect in tube formation and molecular modelling studies.