Spin crossover and cooperativity in nanocrystalline [Fe(pyrazine)Pt(CN)4] thin films deposited by matrix-assisted laser evaporation

Abstract Thin film structures with controlled functionalities are critical to exploit the exceptional application capacity of spin crossover complexes. Here, we report spin crossover (SCO) in thin films of [Fe(pyrazine)Pt(CN)4] nanocrystalline particles (NPs) deposited on monocrystalline Si by laser-mediated evaporation of a cryogenically frozen suspension of the title compound. Both X-ray diffraction and microscopic imaging of the films (thickness ∼120 nm) confirm resembled structure of pristine nanocrystals. However, their spin crossover behavior is dramatically altered going from the cooperative and sharp transition within temperature hysteresis (16 K) around the room temperature region for reference NPs to a gradual transition type shifted downwards to 170 K for the thin films. The decrease in cooperativity within the film is due to side effect of laser-induced desorption that results in rearrangement of the pyrazine-pillared 3D framework into stacked 2D Fe[Pt(CN)4] sheets in the laser affected NP regions. The observed effects have significant implications for future study on the cooperative spin transition in laser-engineered nanocrystalline films.