Irradiation in the solid state of the hypervalent 4c-6e S center dot center dot center dot S-S center dot center dot center dot S bridged sigma-dimer of a bisdithiazolyl radical leads to its photodissociation into a pair of pi-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.