Julie Jung

Magnetic Poles Determinations and Robustness of Memory Effect upon Solubilization in a DyIII-Based Single Ion Magnet

The [Dy(tta)3(L)] complex behaves as a single ion magnet both in its crystalline phase and in solution. Experimental and theoretical magnetic anisotropy axes perfectly match and lie along the most electro-negative atoms of the coordination sphere. Both VSM and MCD measurements highlight the robustness of the complex, with persistence of the memory effect even in solution up to 4 K.

Elucidating the Magnetic Anisotropy and Relaxation Dynamics of Low-Coordinate Lanthanide Compounds

The magnetic relaxation and anisotropy of 3- and 4-coordinate lanthanide complexes were systematically investigated, and the change of SMM behavior originating from the equatorially coordinating ligand field was successfully elucidated through combined experimental and theoretical studies. Remarkably, a novel approach taking into account the different contributions of atomic charges, dipole moments, and quadrupole moments was used to map the electrostatic potential around the metal center in the Dy(III) derivatives, revealing the key role played by the ligands as a whole and not just by the coordinating donor atoms as often considered.

Unraveling the Crystal Structure of Lanthanide-Murexide Complexes: Use of an Ancient Complexometry Indicator as a Near-Infrared-Emitting Single-Ion Magnet

Herein, we provide some structural evidence of the complexation color-change of murexide solutions in presence of lanthanide, which has been used for decades in complexometric studies. For Ln = Sm to Lu and Y, the compounds crystallize as monomeric [Ln(Murex)3]⋅11 H2O with an N3O6 tricapped square-antiprism environment, which are stable up to 250 °C. Single-ion magnet (SIM) behavior is then observed on the Yb(III) derivative in an original nine-coordinated environment. In-field slow relaxation (Δ = (15.6±1) K; τ0 = 2.73×10(-6) s) is observed with a very narrow distribution of the relaxation time (αmax = 0.09). Magnetic and photophysical properties can be correlated. On one hand the analysis of NIR emission spectrum permits to have access to crystal field parameters and to compare them with those extracted from dc measurements. On the other hand, magnetic measurements permit to identify the nature of the MJ states involved in the (2)F5/2 → (2)F7/2 luminescence spectrum. The gap between the low-lying states is in agreement with the energy barrier obtained from magnetic slow-relaxation measurement.

Magnetic and photo-physical investigations into DyIII and YbIII complexes involving tetrathiafulvalene ligand

Three lanthanide-based complexes involving a tetrathiafulvalene derivative (L) in which the lanthanide ion has a pseudo-D4d symmetry have been reported. One is a dinuclear compound of formula [Dy(hfac)3(L)]2 (1) while the two others are isostructural and described as mononuclear complexes of formulae [Ln(tta)3(L)]·xCH2Cl2 (LnIII = Dy and x = 1.41 (2); Yb and x = 2 (3)). The nuclearity of the species is driven by the nature of the ancillary ligands. Magnetic properties revealed that 1 and 3 behave as single molecule magnets, while 2 does not. The crystal field splitting of the ground multiplet state has been theoretically determined as well as the orientation of the easy axis of the ground MJ state. The results of ab initio calculations are in agreement with the experimental determinations of the anisotropy axis. Irradiation of the lowest-energy charge transfer bands of 3 led to an intense and resolved Yb-centred emission which can be correlated to the magnetic data. Thus 3 can be described as a redox-active luminescent field-induced single-molecule magnet.

Analysis of the Magnetic Exchange Interactions in Yttrium(III) Complexes Containing Nitronyl Nitroxide Radicals

We report a combined theoretical and experimental investigation of the exchange interactions governing the magnetic behavior of a series of nitronyl nitroxide (NIT)-based Y(III) complexes, i.e., Y(hfac)3(NIT-R)2 with R = PhOPh (1), PhOEt (2), and PhOMe (3a, 3b). Even though some of these complexes or their Dy(III) parents were previously described in the literature [ Zhao et al. Transition Met. Chem. 2006 , 31 , 593 ; Bernot et al. J. Am. Chem. Soc. 2009 , 131 , 5573 ], their synthesis procedure as well as their structural and magnetic properties were completely reconsidered. Depending on the nature of R and the crystallization conditions, Y(hfac)3(NIT-R)2 units can be organized as supramolecular dimers or linear or orthogonal chains. Such structural diversity within the series induces extremely different magnetic behaviors. The observed behaviors are rationalized by state-of-the-art wave function-based quantum-chemical approaches (CASSCF/DDCI) that demonstrate the existence of not only effective intramolecular interactions between the NIT-R radical ligands of an isolated Y(hfac)3(NIT-R)2 molecule but also intermolecular interactions between NIT-R moieties belonging to different Y(hfac)3(NIT-R)2 units. These results are supported by the use of spin Hamiltonian models going beyond the basic Bleaney-Bowers formalism to properly fit the experimental magnetic data. Finally, the microscopic mechanisms behind the evidenced intramolecular exchange interactions are elucidated through the inspection of the calculated wave functions. In particular, whereas the role of Y orbitals was already proposed, we herein demonstrate the contribution of the hfac- ancillary ligands in mediating the magnetic interactions between the NIT radicals.