Fe(Me2-bpy)2(NCSe)2 spin-crossover micro- and nanoparticles showing spin-state switching above 250 KElectronic supplementary information (ESI) available: Crystal data and molecular geometry of [Fe(Me2-bpy)3](NCSe)2·3(H2O) (Tables ST1 and ST2), optical microscope (Fig. S1) images, Raman data (Table ST3), powder X-ray analysis data (Fig. S2), IR and Raman spectra (Fig. S3 and S6) of Fe(Me2-bpy)x(NCSe)2 complexes (x = 2, 3), TEM images (Fig. S4) and VT Raman spectra (Fig. S7) of nanoparticles; Fig.

• Main Authors: Nguyen, Luong Lam, Guillot, Régis, Laisney, Jérôme, Rechignat, Lionel, Bedoui, Salma, Molnár, Gabor, Rivière, Eric, Boillot, Marie-Laure
• Format: Journal Article
• Language: English
• Published: 02.03.2015
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/c4nj01257g

We present the study of nano- and microparticles of the Fe(Me 2 -bpy) 2 (NCSe) 2 spin-crossover complex prepared from the diamagnetic precursor [Fe(Me 2 -bpy) 3 ](NCSe) 2 ·S. Two solvates of the latter were characterized by single-crystal X-ray structures at 100 K (S = 2MeOH or 3H 2 O). The extraction of one Me 2 -bpy per metal ion in [Fe(Me 2 -bpy) 3 ](NCSe) 2 ·S was achieved either by thermolysis at temperature higher than 150 °C or by precipitation in an anti-solvent, leading to a polycrystalline or particulate powder of Fe(Me 2 -bpy) 2 (NCSe) 2 . This chemical conversion was investigated by TGA, powder X-ray diffraction, IR, Raman and magnetic measurements. The S = 0 ↔ S = 2 spin-crossover of Fe(Me 2 -bpy) 2 (NCSe) 2 centered at ca. 340 K is almost complete at low temperature (HS residue ≤ 5% below 250 K) while at 370 K, the HS fraction can be estimated at ∼0.7. These features are essentially preserved whatever be the size of particles (56, 460 and 1200 nm) as a consequence of the weak cooperativity of the process occurring at high temperature, the crystallinity and the molecular nature of particles. This approach leading to dispersion of small particles in a polymer is suitable for the preparation of materials of optical quality, via the stabilization and processing of nanoparticles in convenient matrices to form thin films. Nano- and microparticles or polycrystalline powders of the Fe(Me 2 -bpy) 2 (NCSe) 2 spin-crossover complex were easily elaborated from the diamagnetic precursor [Fe(Me 2 -bpy) 3 ](NCSe) 2 ·S by precipitation in an anti-solvent or by solid-state thermolysis.