Photoswitching of the spin crossover polymeric material [Fe(Htrz)2(trz)](BF4) under continuous laser irradiation in a Raman scattering experiment

Photoswitching of the [Fe(Htrz)2(trz)](BF4) spin crossover polymeric material has been investigated by means of confocal Raman spectroscopy upon continuous laser irradiation outside and inside its thermal hysteresis loop. In both cases, the evolution of HS and LS Raman marker bands show that light excitation can trigger the LS to HS transition, but the long-lived HS state can be populated only within the hysteresis loop. Local sample heating can explain this light-induced effect leading to a narrowing of the thermal hysteresis loop for laser intensities higher than 0.02 mW/μm2, in strong accordance with previous time-resolved pump–probe experiments on similar materials.