Spin crossover behavior in a homologous series of iron(II) complexes based on functionalized bipyridyl ligands
(2018) Inorganic Chemistry — Vol. 57, n° 16, p. 9880-9891 (2018)
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- Authors
Rotaru, Aurelian 
- Abstract
- A series of bulky substituted bipyridine-related iron(II) complexes [Fe(H2Bpz2)2(L)] (pz = pyrazolyl) were prepared, where L = 5,5′-dimethyl-2,2′-bipyridine (bipy-CH3, 1), L = dimethyl-2,2′-bipyridyl-5,5′-dicarboxylate (MeObpydc, 2), L = diethyl-2,2′-bipyridyl-5,5′-dicarboxylate (EtObpydc, 3), or L = diisopropyl-2,2′-bipyridine-5,5′-dicarboxylate (i-PrObpydc, 4). The crystal structures of five new iron(II) complexes were determined by X-ray diffraction: those of 1, 3, and 4 and two modifications of 3 (3B) and 4 (4B). Complexes 1 and 3B display incomplete spin crossover (SCO) behavior because of a freezing-in effect, whereas 3 and 4B undergo gradual and incomplete SCO behaviors. Complexes 2 and 4 show a completely gradual and steep SCO, respectively. Such different SCO behaviors can be attributed to an electronic substituent effect in the bipyridyl ligand conformation and a crystal packing effect. Importantly, the electronic substituent effect of the isopropyl acetate group and C-H···O supramolecular interactions in 4 contribute to a highly cooperative behavior, which leads to an abrupt thermally induced spin transition.
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Xue, S., Guo, Y., Rotaru, A., Müller-Bunz, H., Morgan, G. G., Trzop, E., Collet, E., Oláh, J., & Garcia, Y. (2018). Spin crossover behavior in a homologous series of iron(II) complexes based on functionalized bipyridyl ligands. Inorganic Chemistry, 57(16), 9880-9891. https://doi.org/10.1021/acs.inorgchem.8b00850 (Original work published 2018)