Fe(Me₂-bpy)₂(NCSe)₂spin-crossover micro- and nanoparticles showing spin-state switching above 250 K

Abstract

Nano- and microparticles or polycrystalline powders of the Fe(Me2-bpy)2(NCSe)2spin-crossover complex were easily elaborated from the diamagnetic precursor [Fe(Me2-bpy)3](NCSe)2·S by precipitation in an anti-solvent or by solid-state thermolysis.

Nanocrystals of Fe(phen)2(NCS)2 and the size-dependent spin-crossover characteristics

“…13 The diffractograms of 2 show very sharp Bragg reflections and thus confirm the sample crystallinity as underlined in the case of Fe(Me 2 -bpy) 2 (NCSe) 2 . 11 Moreover, this unambiguously proves the formation of polymorph II of Fe II ( phen) 2 (NCS) 2 . 19 Concerning nanochemistry, the issue to address first is the possibility to control the precipitation of the neutral species by stabilizing the ionic precursor in solution.…”

“…The balance between the formation of ionic and neutral particles is primarily directed by the solubility of the reactant/ product and then, by the kinetics of ligand extraction and nucleation/growth of the particles, the latter being partly controlled through the selection of experimental conditions. According to the recent studies of spin-crossover nanoparticles based on molecular species, 8,9,11,31 the formation of shaped particles, with a variation of size between a few μm and a few tens of nm, is a common feature associated with solventassisted precipitation. Moreover, an enlarged size distribution is a consequence of the chemical equilibrium involving the compound to be precipitated.…”

“…However, we have observed with the Fe(Me 2bpy) 2 (NCSe) 2 spin-crossover compound that the simple addition of the ionic Fe(II) tris-bipyridine precursor in an anti-solvent may lead to the ligand extraction combined with the precipitation of the spin-crossover particles. 11 This suggests that for nanoparticle synthesis, advantage can be taken from the chemical equilibrium occurring between the soluble and diamagnetic reactant and the neutral spin-crossover species, and its shift by extraction of the ligand (solvent-induced or thermal process).…”

Unraveling the Environment Influence in Bistable Spin-Crossover Particles Using Magnetometric and Calorimetric First-Order Reverse Curves

“…Accordingly, the changes in their FORC distributions can be assigned to the differences in the microparticle−matrix interactions as pointed above and thus to the elastic stability characteristics of the two solidified matrices. 48 Another striking observation is the lack of the mirror symmetry in Figures 7−9, in opposition to the model bulk case where FORC distributions obtained in the heating and cooling modes are rather similar (as shown in Figure 6). This confirms first the effect of variable interactions between the microparticles and the matrix (as here they replace the classical interdomain interactions).…”

Kinetics and Thermodynamics of Constitutional Dynamic Coordination Systems Based on FeII, CoII, NiII, CuII, and ZnII

“…Two different ligands were in addition chosen: 5,5′‐ and 4,4′‐substituted 2,2′‐bipyridines, expected to display relatively minor structural differences of the different complexes compared to the 3,3′‐ or 6,6′‐substituted counterparts . Crystal structures have been reported for some of the homoleptic complexes . For detection purposes, 5,5′‐dimethyl‐2,2′‐bipyridine L1 and stable, isotope‐labeled ligand [D 6 ]‐4,4′‐dimethyl‐2,2′‐bipyridine L2 , prepared using microwave‐assisted deuteration, were thus used to construct the complexes (Figure ).…”