Structural investigation of the photoinduced spin transition in the three states molecular system [Fe(2-pic)3]Cl2EtOH

We present the detailed results of the investigation by X-ray diffraction of the photoinduced phase transition in the Tris(α-picolylamine)iron(II) Chloride-Ethanol complex. This system undergoes a two-steps spin transition between a high spin state at room temperature and a low spin state at low temperature. The intermediate phase consists of stripes of high spin and low spin molecules. The X-ray diffraction data evidence the structural rearrangement at the molecular scale accompanying the photoinduced change of electronic state between the low-spin phase and the photo-steady high-spin one, which is similar to the stable one in the high temperature phase. The dynamical mechanism of the transformation is discussed with the observation of a domain nucleation process, associated with the coexistence of the stable and photoinduced phases.