Host–guest exchange contribution to transition temperature downshift in nanocrystalline Fe(pyrazine)[Pt(CN)₄] thin films prepared by matrix-assisted pulsed laser evaporation

The influence of guest molecules affecting the spin transition characteristics of iron(II) complexes represents a widely discussed topic because it opens the possibility of using this type of materials in many fields of science, especially if the material properties could be tuned in a controlled way. We report an experimental observation of the spin transition in thin films of a 3D Hoffman framework nanocrystalline material Fe(pyrazine)[Pt(CN)₄] deposited by nanosecond laser ablation at λ = 1064 nm of its cryo-cooled colloidal suspension in water and water-free organic solvents. For vacuum deposited films (thickness 120 nm), the substantial downshift in temperature, gradual spin transition, and shrinkage of the temperature hysteresis compared to the starting material are ascribed to incomplete removal of water molecules from the porous network and partial destruction of the crystalline site caused by laser heating. The destructive effect of laser irradiation occurring in vacuum conditions was not observed for deposition conducted in N₂ at atmospheric pressure. In this case, thin films reproducing properties of the reference material with transition temperature near 276 K and 12 K wide hysteresis were obtained. In addition, the changes in the spin switching characteristics associated with the exchange of guest molecules in the SCO crystal lattice were observed using a water-free solvent as a matrix for the laser based thin film deposition. The observed laser induced host–guest exchange indicates on the possibility of selective modification of thin layers of SCO materials to obtain their desired characteristics.