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Electronic Structure and Magnetic Properties of Dioxo-Bridged Diuranium Complexes with Diamond-Core Structural Motifs: A Relativistic DFT Study

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journal contribution
posted on 01.03.2016, 19:53 by Billel Teyar, Lotfi Belkhiri, Karine Costuas, Abdou Boucekkine, Karsten Meyer
Electronic structures and magnetic properties of the binuclear bis­(μ-oxo) UIV/UIV K2[{((nP,MeArO)3tacn)­UIV}2(μ-O)2] and UV/UV [{((nP,MeArO)3tacn)­UV}2(μ-O)2] (tacn = triazacyclononane, nP = neopentyl) complexes, exhibiting [U­(μ-O)2U] diamond-core structural motifs, have been investigated computationally using scalar relativistic Density Functional Theory (DFT) combined with the Broken Symmetry (BS) approach for their magnetic properties. Using the B3LYP hybrid functional, the BS ground state of the pentavalent [UV(μ-O)2UV] 5f1–5f1 complex has been found of lower energy than the high spin (HS) triplet state, thus confirming the antiferromagnetic character in agreement with experimental magnetic susceptibility measurements. The nonmagnetic character observed for the tetravalent K2[UIV(μ-O)2UIV] 5f2–5f2 species is also predicted by our DFT calculations, which led practically to the same energy for the HS and BS states. As reported for related dioxo diuranium­(V) systems, superexchange is likely to be responsible for the antiferromagnetic coupling through the π-network orbital pathway within the (μ-O)2 bridge, the dissymmetrical structure of the U2O2 core playing a determining role. In the case of the UIV species, our computations indicate that the K+ counterions are likely to play a role for the observed magnetic property. Finally, the MO analysis, in conjunction with NPA and QTAIM analyses, clarify the electronic structures of the studied complexes. In particular, the fact that the experimentally attempted chemical oxidation of the UV species does not lead straightforwardly to binuclear complexes UVI is clarified by the MO analysis.