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Synthesis of Spin‐Crossover Nano‐ and Micro‐objects in Homogeneous Media
Author(s) -
Gural'skiy Il'ya A.,
Quintero Carlos M.,
Molnár Gábor,
Fritsky Igor O.,
Salmon Lionel,
Bousseksou Azzedine
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201201063
Subject(s) - nanorod , spin crossover , materials science , nanoparticle , nano , chemical engineering , polymer , morphology (biology) , dynamic light scattering , nanotechnology , crystallography , chemistry , biology , engineering , composite material , genetics
New methods are proposed for the synthesis of spin‐crossover nano‐ and micro‐objects. Several nano‐objects that are based upon the spin‐crossover complex [Fe(hptrz) 3 ](OTs) 2 (hptrz=4‐heptyl‐1,2,4‐triazole, Ts= para ‐toluenesulfonyl) were prepared in homogeneous media. The use of various reagents (Triton X‐100, PVP, TOPO, and PEGs of different molecular weights) as stabilizing agents yielded materials of different size (6 nm–2 μm) and morphology (nanorods, nanoplates, small spherical particles, and nano‐ and micro‐crystals). In particular, when Triton X‐100 was used, a variation in the morphology from nanorods to nanoplates was observed by changing the nature of the solvent. Interestingly, the preparation of the nanorods and nanoplates was always accompanied by the formation of small spherical particles. Alternatively, when PEG was used, 200–400 nm crystals of the complex were obtained. In addition, a very promising polymer‐free synthetic method is discussed that was based on the preparation of relatively stable Fe II –triazole oligomers in CHCl 3 . Their specific treatment led to micro‐crystals, small nanoparticles, or gels. The size and morphology of all of these objects were characterized by TEM and by dynamic light scattering (DLS) where possible. Their spin‐crossover behavior was studied by optical and magnetic measurements. The spin‐transition features for large particles (>100 nm) were very similar to that of the bulk material, that is, close to room temperature with a hysteresis width of up to 8 K. The effects of the matrix and/or size‐reduction led to modification of the transition temperature and an abruptness of the spin transition for oligomeric solutions and small nanoparticles of 6 nm in size.