  High spin (S=3/2) organic triradicals may offer enhanced properties with
respect to several emerging technologies, but those synthesized to date
typically exhibit small doublet quartet energy gaps and/or possess limited
thermal stability and processability. We report a quartet ground state
triradical 3, synthesized by a Pd(0)-catalyzed radical-radical cross-coupling
reaction, which possesses two doublet-quartet energy gaps, DeltaEDQ ~ 0.2-0.3
kcal mol-1 and DealtaEDQ2 ~ 1.2-1.8 kcal mol-1. The triradical has a 70+%
population of the quartet ground state at room temperature, and good thermal
stability with onset of decomposition at > 160 {\deg}C under inert atmosphere.
Magnetic properties of 3 are characterized by SQUID magnetometry in polystyrene
glass and by quantitative EPR spectroscopy. Triradical 3 is evaporated under
ultra-high vacuum to form thin films of intact triradicals on silicon
substrate, as confirmed by high resolution X-ray photoelectron spectroscopy.
AFM and SEM images of the around 1 nm thick films indicate that the triradical
molecules form islands on the substrate. The films are stable under ultra-high
vacuum for at least 17 h but show onset of decomposition after 4 h at ambient
conditions. The drop-cast films are less prone to degradation in air and have
longer lifetime.
