Various Sizes and Shapes of Mixed-Anion Fe(NH2trz)3(BF4)2-x(SiF6)x/2@SiO2 Nanohybrid Particles Undergoing Spin Crossover Just Above Room Temperature.

Spin crossover (SCO) iron (II) coordination compounds in the form of nanohybrid SCO@SiO2 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 SiF62- counter-anion and SiO2 to obtain Fe(NH2trz)3(BF4)2-x(SiF6)x/2@SiO2 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.