Challenges in Controlled Thermal Deposition of Organic Diradicals

We demonstrate that it is possible to evaporate diradicals in a controlled environment obtaining thin films in which the diradical character is preserved. However, evaporation represents a challenge. The presence of two radical sites makes the molecules more reactive also in the case of very stable single radicals. We have explored the parameters that play a role in this phenomenon. We found that the higher the formation energies of the crystal, the more difficult is the evaporation of intact radicals. Large delocalization of the unpaired electrons helps the diradical to stand evaporation. We have also investigated the lifetime of the films when exposed to X-rays or air. The onset of thermal degradation plays a role in the film lifetime. In fact, the lower the evaporation temperature with respect to the onset temperature, the longer is the film lifetime. The evaporation of different diradicals can be successfully addressed considering our findings.