Photo-induced phase transitions probed by X-ray absorption spectroscopy: Fe(II) spin crossover complex Original Research Article

Photo-induced phase transitions in spin-crossover complex [Fe(II)(2-pic)3]Cl2EtOH were investigated by X-ray absorption spectroscopy (XAS) technique. In situ XAS results showed that the metal-ligand (Fe–N) bond distance expands by ca. 0.20 Å upon photo-induced (S=0→S=2) spin conversion. We find that nearly octahedral (Oh) symmetry of FeN6 coordination remains in the photo-induced high spin state. The next-nearest neighbor Fe–C radial distribution shows a subtle change due to local distortions of ligand molecules. Inhomogeneous distribution of strains may disturb cooperative photo-induced phase transitions removing centers of inversion symmetry.