Spin-crossover nano- and micrometric rod-shaped particles synthesized in homogeneous acid media
Résumé
Acidic conditions were used for the elaboration of spin-crossover (SCO) nano- and microparticles of BF4 derivs. of a (triazole)iron complex. Modifying both the acid (HBF4) concn. and the synthetic method (reaction and evapn. rate), rods of various sizes ranging from 100 nm to ∼50 μm were obtained. The morphologies of the particles were probed by transmission electronic microscopy (TEM) and high-resoln. transmission electronic microscopy coupled quantified energy-dispersive x-ray spectroscopy (HRTEM-EDX), elemental anal., DSC, NMR spectroscopy, and TGA were used to det. the fine compns. of the different samples. All these characterizations revealed a correlation between the size of the rod-shape particles and their compn., the smaller rods corresponding to the [Fe(Htrz)2(trz)](BF4) complex (form A; Htrz = 1,2,4-triazole and trz = 1,2,4-triazolato), and the larger ones to the [Fe(Htrz)3](BF4)2·3H2O deriv. (form B). The SCO properties were investigated by optical, magnetic, and Mossbauer measurements.