We examine the pressure dependence of the spin-crossover transition in [Fe(pap-5NO2)2] that occurs near room temperature. We employ a combination of high-pressure calorimetry and powder X-ray diffraction measurements, conducted both under variable-pressure and variable temperature conditions. Both methods indicate that the spin-crossover transition shifts linearly to higher temperatures with increasing pressure, while simultaneously exhibiting an increase in the width of the thermal hysteresis. We report a giant barocaloric effect, revealing isothermal entropy changes in the 70.2-79.1 J kg-1 K-1 range and adiabatic temperature changes between 19.6 and 25.9 K for a pressure change of 2 kbar. Although the effect diminishes under reversible conditions, it remains substantial, with values of 70.2 J kg-1 K-1 and 13.5 K, respectively., Peer reviewed

We examine the pressure dependence of the spin-crossover transition in [Fe(pap-5NO2)2] that occurs near room temperature. We employ a combination of high-pressure calorimetry and powder X-ray diffraction measurements, conducted both under variable-pressure and variable-temperature conditions. Both methods indicate that the spin-crossover transition shifts linearly to higher temperatures with increasing pressure, while simultaneously exhibiting an increase in the width of the thermal hysteresis. We report a giant barocaloric effect, revealing isothermal entropy changes in the 70–79 J kg−1 K−1 range and adiabatic temperature changes between 20 and 26 K for a pressure change of 2.0 kbar. Although the effect diminishes under reversible conditions, it remains substantial, with values of 70 J kg−1 K−1 and 14 K, respectively., This work was funded by MICIU/AEI/10.13039/501100011033 and ERDF/UE (PID2021-124734OB-C21, CEX2023-001286-S), Gobierno de Aragón (E11-23R, E12-23R) and Fundación IberCaja and Universidad de Zaragoza (JIUZ2023-CIE-05). D. G. acknowledges financial support from the Gobierno de Aragón through a doctoral fellowship., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2023-001286-S)., Peer reviewed

We examine the pressure dependence of the spin-crossover transition in [Fe(pap-5NO2)2] that occurs near room temperature. We employ a combination of high-pressure calorimetry and powder X-ray diffraction measurements, conducted both under variable-pressure and variable-temperature conditions. Both methods indicate that the spin-crossover transition shifts linearly to higher temperatures with increasing pressure, while simultaneously exhibiting an increase in the width of the thermal hysteresis. We report a giant barocaloric effect, revealing isothermal entropy changes in the 70–79 J kg−1 K−1 range and adiabatic temperature changes between 20 and 26 K for a pressure change of 2.0 kbar. Although the effect diminishes under reversible conditions, it remains substantial, with values of 70 J kg−1 K−1 and 14 K, respectively.