Various Sizes and Shapes of Mixed-Anion Fe(NH 2 trz) 3 (BF 4 ) 2-x (SiF 6 ) x/2 @SiO 2 Nanohybrid Particles Undergoing Spin Crossover Just Above Room Temperature.

Spin crossover (SCO) iron (II) coordination compounds in the form of nanohybrid SCO@SiO ₂ particles were prepared using a reverse micelles technique based on the TritonX-100/cyclohexane/water ternary system. Tetraethyl orthosilicate (TEOS) acts as precursor of both the SiF ₆ ^2- counter-anion and SiO ₂ to obtain Fe(NH ₂ trz) ₃ (BF ₄ ) _2-x (SiF ₆ ) _x/2 @SiO ₂ nanoparticles with different sizes and morphologies while modifying the TEOS concentration and reaction time. The adjustable mixed-anion strategy leads to a range of quite scarce abrupt spin crossover behaviors with hysteresis just above room temperature (ca. 293 K), which is very promising for the integration of these materials into functional devices.