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Nouvelle publication de l’équipe Ciel : « On the magnetic coupling and spin crossover behavior in complexes containing the head-to-tail [FeII2(m-SCN)2] bridging unit: A magneto-structural experimental and theoretical study. »

Cle Donacier Mekuimemba,‡ Françoise Conan,‡ Antonio J. Mota,† Maria Angeles Palacios,† Enrique Colacio,†* Smail Triki‡*

Inorg. Chem. 2018, ASAP DOI: 10.1021/acs.inorgchem.7b03082

A new dinuclear complex [{Fe(tpc-Obn)(NCS)(μ-NCS)}2] (1) based on the tripodal tpc-Obn ligand (tpc-Obn = tris(2-pyridyl)benzyloxymethane), containing bridging m-kN:kS-SCN and terminal kN-SCN thiocyanate ligands, has been prepared and characterized by single crystal X-ray diffraction, magnetic studies and DF theoretical calculations. This complex represents the first example of dinuclear FeII complex with double m-kN:kS-SCN bridges in a head-to-tail configuration that exhibits ferromagnetic coupling between metal ions (JFeFe = + 1.08 cm-1). Experimental and theoretical magneto-structural studies on this kind of infrequent FeII dinuclear complexes containing a centrosymmetrically [Fe2(m-SCN)2] bridging fragment show that the magnitude and sign of the magnetic coupling parameter, JFeFe, depend to a large extent on Fe-N-C (a) angle, so that JFeFe decreases linearly when a decreases. The calculated crossover point below which the magnetic interactions change from ferromagnetic to antiferromagnetic is found at 162.3º. In addition, experimental results obtained in this work and those reported in the literature suggest that large Ntripodal-FeII distances and bent N-bound terminal kN-SCN ligands favour the high spin state of the FeII ions, while short Ntripodal-FeII distances and almost linear Fe-N-C angles favour a stronger ligand field, which enables the FeII ions to show spin crossover (SCO) behaviour.