Pressure-Induced High Spin State in [Fe(btr)₂(NCS)₂]·H₂O (btr = 4,4‘-bis-1,2,4-triazole)

Application of hydrostatic pressure (≤ 10.5 kbar) on the two-dimensional spin transition compound [Fe(btr) 2 (NCS) 2 ]·H 2 O (btr = 4,4‘-bis-1,2,4-triazole) results in an unexpected stabilization of the HS state. On release of the pressure, the HS state is found to be partially trapped. After thermal relaxation of the metastable HS state obtained by the LIESST effect (light-induced excited spin state trapping), a pure LS state is obtained in contrast to the pressure experiments. This different behavior supports a structural phase transition as the likely basis of the pressure-induced HS state.