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International audience; This chapter presents different aspects of the modeling of magnetic properties in monomeric open-shell actinide complexes. Those properties are closely related to their electronic structure, which is difficult to achieve since none of crystal-field effects, electron-electron repulsion nor spin-orbit interaction is predominant. The electronic structure should be analyzed within the intermediate coupling scheme, between on one hand the Russell-Saunders coupling scheme where the inter-eletronic repulsion is considered before spin-orbit, and, on the other hand, the j-j coupling scheme where one-electron wave-functions including spin-orbit are used to build the many-electron wave-function. Ab initio calculations on these complexes are challenging, and SO-CAS based methods are still the quantum chemistry tool of choice since they include a balanced description of the three effects. It is only by a close interplay between experimental data which are sparse for transuranide complexes due to radioactivity, numerical methods, and model Hamiltonians that one succeeds to unravel the electronic structure and magnetic properties of these complexes.

output files for article "Analysis of the magnetic couplingin a {Mn(II)-U(V)-Mn(II)} Single Molecule Magnet"

Two relaxation processes of the magnetization in an antiferromagnetically coupled Dy2 metallacrown-based complex., We report here the synthesis and the investigation of the magnetic properties of a series of binuclear lanthanide complexes belonging to the metallacrown family. The isostructural complexes have a core structure with the general formula [Ga4Ln2(shi3–)4(Hshi2–)2(H2shi–)2(C5H5N)4(CH3OH)x(H2O)x]·xC5H5N·xCH3OH·xH2O (where H3shi = salicylhydroxamic acid and Ln = GdIII1; TbIII2; DyIII3; ErIII4; YIII5; YIII0.9DyIII0.16). Apart from the Er-containing complex, all complexes exhibit an antiferromagnetic exchange coupling leading to a diamagnetic ground state. Magnetic studies, below 2 K, on a single crystal of 3 using a micro-squid array reveal an opening of the magnetic hysteresis cycle at zero field. The dynamic susceptibility studies of 3 and of the diluted DyY 6 complexes reveal the presence of two relaxation processes for 3 that are due to the excited ferromagnetic state and to the uncoupled DyIII ions. The antiferromagnetic coupling in 3 was shown to be mainly due to an exchange mechanism, which accounts for about 2/3 of the energy gap between the antiferro- and the ferromagnetic states. The overlap integrals between the Natural Spin Orbitals (NSOs) of the mononuclear fragments, which are related to the magnitude of the antiferromagnetic exchange, are one order of magnitude larger for the Dy2 than for the Er2 complex.

International audience; La spectroscopie de résonnance magnétique nucléaire (RMN) est capable de fournir des informations structurales sur des complexes en solution. Elle s’applique en chimie organique, en biologie mais aussi en radiochimie grâce à la nucléarisation des spectromètres. La présence d’un cation paramagnétique en solution génère une modification du spectre RMN : un élargissement et/ou une variation du déplacement chimique des pics, caractéristique du paramagnétisme du cation.