Photoinduced spin transition probed by x-ray diffraction

We report on a photocrystallography investigation of the photoinduced phase transition in the Tris({α}-picolylamine)iron(II) chloride-ethanol complex. X-ray diffraction data show the structural rearrangement at the atomic scale accompanying the photosteady change of electronic state between the low-spin phase and the high-spin phase. The dynamical mechanism of the transformation is discussed with the observation of a domain nucleation process, with the coexistence of stable and photoinduced phases.