High-temperature photo-induced switching and pressure-induced transition in a cooperative molecular spin-crossover material

Abstract

The thermal and photo-induced switching properties of the recently published molecular spin crossover complex [Fe(H₄L)₂](ClO₄)₂·H₂O·2(CH₃)₂CO (1) have been investigated in detail through Raman spectroscopy. Magnetometric and single crystal X-ray diffraction kinetic studies within the hysteresis loop have proven its metastable character, which allowed establishing the shape of the true, quasi-static hysteresis loop. This is related to the proximity of the temperatures of the thermal high to low spin SCO (T_1/2↓) to those of the relaxation of the thermally or photo-generated metastable states (T(TIESST) and T(LIESST), respectively). Green light irradiation within the hysteresis loop results in a complete low to high spin photo-switch. In addition, the SCO of 1 at room temperature can be induced by applying pressure, as followed by Raman spectroscopy.