Spin-state transitions in an iron spin-crossover complex observed with X-ray emission and X-ray absorption

The thermal- and photon-induced phase transitions of [Fe(2-pic) ₃]Cl₂EtOH from a high-spin (HS) state (S=2) to a low-spin (LS) state (S=0) were observed by X-ray Emission Spectroscopy (XES) and X-ray Absorption Spectroscopy (XAS). The spin state was observed with Fe 3p-1s XES from the HS and photon-induced (PI) phase took S = 2 and LS state took S = 0. Each spectrum of the decay process from the PI phase to the LS state could be described with the superposition of those of the HS and LS states, In XAS, a different spectrum was also observed in the HS and LS states, and likewise by XES; the difference in the pre-edge structure between the HS and LS states was explained based on the difference of Fe unoccupied 3d partial density of state calculated by the DV-Xα method.