Unusually High Selectivity of Guest Exchange in <i>tert</i>-Butylthiacalix[4]arene Clathrate Producing More Thermostable Inclusion and Memory of Guest

New properties, earlier unknown for calixarenes, were found for <i>tert</i>-butylthiacalix­[4]­arene (<b>1</b>) clathrate with 1,2-dichloroethane (DCE). Guest exchange in <b>1</b>·1.90DCE for vapors of some organic compounds gives clathrates, which are more thermostable at 34–59 °C than those prepared by direct saturation of guest-free <b>1</b> with pure guests. Besides, guest exchange may produce clathrates that cannot be formed by direct saturation in binary host–guest systems. Some compounds, like water, toluene, and trichloroethylene, expel DCE from its clathrate with <b>1</b> but are not included above the trace level. Residual contents of DCE in clathrate may be controlled by variation of water and <b>1</b>·1.90DCE ratio in the studied system. Host <b>1</b> can remember methanol after its elimination from the guest exchange product. This memory can be read as an exoeffect by differential scanning calorimetry. Only methanol and only after guest exchange is remembered giving an example of a genuine molecular recognition