Room temperature bistability with wide thermal hysteresis in a spin crossover silica nanocomposite

Nanocomposites have been processed following a wet-impregnation approach, by confined growth of nanoparticles of the spin crossover complex [Fe(Htrz)(2)(trz)](BF4) within pre-formed transparent mesoporous silica monoliths of well controlled porosity. The obtained materials were studied using numerous characterisation techniques to define the interplay between the porosity of the host matrix, the structure and morphology of the in situ elaborated nanoparticles, and the spin crossover properties of the composite. Transmission electron micrographs show monodisperse spherical nanoparticles of mean diameter 3.2(5) nm, homogeneously distributed within the pores of the silica monolith. Magnetic measurements, temperature dependent infrared, Raman, and Mossbauer spectroscopy confirm the spin transition behaviour of the nanocomposite, with a room temperature bistability and 65 K wide hysteresis.