Photoinduced Solid State Conversion of a Radical σ‑Dimer to a π‑Radical Pair

Irradiation in the solid state of
the hypervalent 4c-6e S···S–S···S
bridged σ-dimer of a bisdithiazolyl radical leads to its photodissociation
into a pair of π-radicals. The transformation has been monitored
by optical spectroscopy, single crystal X-ray diffraction, and magnetic
susceptibility measurements. As a result of the large electronic reorganization
involved in the dimer-to-radical interconversion, the photogenerated S = 1/2 radical state is remarkably thermally stable, persisting
to 242 K before reverting to the S = 0 dimer.