On the Magnetic Coupling and Spin Crossover Behavior in Complexes Containing the Head-to-Tail [FeII 2(μ-SCN)2] Bridging Unit: A Magnetostructural Experimental and Theoretical Study

• Published in: Inorganic chemistry 2018-02, Vol.57 (4), p.2184-2192
• Main Authors: Mekuimemba, Cle Donacier, Conan, Françoise, Mota, Antonio J, Palacios, Maria A, Colacio, Enrique, Triki, Smail
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• 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 μ-κN:κS-SCN and terminal κN-SCN thiocyanate ligands, has been prepared and characterized by single crystal X-ray diffraction, magnetic studies, and DFT theoretical calculations. This complex represents the first example of dinuclear FeII complex with double μ-κN:κS-SCN bridges in a head-to-tail configuration that exhibits ferromagnetic coupling between metal ions (J FeFe = +1.08 cm–1). Experimental and theoretical magnetostructural studies on this kind of infrequent FeII dinuclear complex containing a centrosymmetrically [Fe2(μ-SCN)2] bridging fragment show that the magnitude and sign of the magnetic coupling parameter, J FeFe, depend to a large extent on the Fe–N–C (α) angle, so that J FeFe decreases linearly when α decreases. The calculated crossover point below which the magnetic interactions change from ferromagnetic to antiferromagnetic is found at 162.3°. 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 κN-SCN ligands favor the high spin state of the FeII ions, while short Ntripodal–FeII distances and almost linear Fe–N–C angles favor a stronger ligand field, which enables the FeII ions to show spin crossover (SCO) behavior.