Pressure-induced high spin state in [Fe(btr)(2)(NCS)(2)]center dot H2O (btr=4,4 '-bis-1,2,4-triazole)

Application of hydrostatic pressure (less than or equal to 10.5 kbar) on th e two-dimensional spin transition compound [Fe(btr)(2)(NCS)(2)] . H2O (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 t rapped. After thermal relaxation of the metastable HS state obtained by the LIESST effect (light induced excited spin state trapping), a pure LS stare is obtained in contrast to the pressure experiments. This different behavi or supports a structural phase transition as the likely basis of the pressu re-induced HS state.