Reverse micelle synthesis and downsizing effects in iron(iii) spin crossover materials

Abstract

We report the reverse micelle synthesis, structural characterisation and magnetic properties of iron(III) spin crossover (SCO) nanomaterials based on [Fe(qsal)₂]NO₃, [Fe(qsal-I)₂]OTf and [Fe(qsal-I)₂]NTf₂ using sodium dioctylsulfosuccinate (NaAOT) and hexane. The synthesis and characterization of a new complex, [Fe(qsal)₂]NO₃·EtOH is also reported. Systematic variation of micellar conditions including surfactant content in the polar and organic phases, reaction time, and solvent choice enabled the controlled formation of parallelogram, plate-like and rod-like shapes for [Fe(qsal)₂]NO₃, [Fe(qsal-I)₂]OTf and [Fe(qsal-I)₂]NTf₂, respectively, as confirmed by FESEM. Magnetic studies reveal abrupt spin crossover with a narrower hysteresis width compared to the bulk materials. Nanomaterials of [Fe(qsal-I)₂]OTf exhibit a 4 K hysteresis (T_1/2↑ = 231 K and T_1/2↓ = 227 K) while those of [Fe(qsal-I)₂]NTf₂ display a 27 K hysteresis (T_1/2↑ = 275 K and T_1/2↓ = 248 K) comparable to the bulk. The results demonstrate that reverse micelle methods can reliably produce iron(III) SCO nanomaterials, advancing their potential for integration into functional devices.