Thermally induced valence tautomerism with hysteresis has been discovered by the CIMP team in lamellar compounds consisting of 2D manganese(II)-radical nitronyl nitroxide coordination polymer sheets separated by anions¹. This phenomenon occurs near room temperature and involves thermally triggered reversible electron transfer. On cooling the Mn(II) ions oxidize to Mn(III) and transfer their electrons to the radicals which are reduced. On heating the process is reversed with hysteresis². In our recent work which is the subject of this communication in ChemComm of the RSC, we have shown, in collaboration with a Canadian group from the University of Montreal and a Japanese group from Hiroshima University, that the conversion can be shifted to high temperatures by a small increase in pressure³. These results open a new approach towards switchable materials with hysteresis with prospects of investigation of intramolecular electron transfers in the solid state with potential applications in the field of temperature or pressure memory sensors.