Heat Capacity and Thermal Damping Properties of Spin-Crossover Molecules: A New Look at an Old Topic.

The thermally induced spin-crossover (SCO) phenomenon in transition metal complexes is an entropy-driven process, which has been extensively studied through calorimetric methods. Yet, the excess heat capacity associated with the molecular spin-state switching has never been explored for practical applications. Herein, the thermal damping effect of an SCO film is experimentally assessed by monitoring the transient heating response of SCO-coated metallic microwires, Joule-heated by current pulses. A damping of the wire temperature, up to 10%, is evidenced on a time scale of tens of microseconds due to the spin-state switching of the molecular film. Fast heat-charging dynamics and negligible fatigability are demonstrated, which, together with the solid-solid nature of the spin transition, appear as promising features for achieving thermal energy management applications in functional devices.