Temperature-triggered reversible ferroelastic phase transition in an 1:1 inclusion complex of 18-crown[6] with 4-ethylanilinium tetrafluoroborate

► One reversible phase transition ferroelastic compound is synthesized. ► DSC and structural analysis reveal the phase transition point of 180 K. ► The slight swing of the ethyl group is probably the driving force. ► Combined crystal-engineering strategy with Landau theory in ferroelastrics design.