Investigating the thermally- and light-induced interconversion of bisdithiazolyl radicals and dimers with high-field EPR

Materials with magnetic properties that can be modulated via optical excitation offer enticing opportunities for the development of next generation technologies. An exciting new class of photomagnetic materials based on bisdithiazolyl radicals has recently been developed. The dimorphic system in this study crystallizes in two phases, one composed of diamagnetic dimers and the other of paramagnetic radicals. Here we report on the use of high-field electron paramagnetic resonance spectroscopy to characterize both the thermally- and light-induced transitions in the dimer phase. During the course of this study we show that signals originating from residual radical defects in the dimer phase can be differentiated from those arising from the radical phase.