9:00 AM - *EQ07.03.02
Radical Approach to Lanthanide-Based Single-Molecule Magnets
Jani Moilanen1,Juho Toivola1,Maykon Lemes2,Niki Mavragani3,Paul Richardson3,Jaclyn Brusso3,Muralee Murugesu3
University of Jyväskylä1,Universidade Federal de Goiás2,University of Ottawa3
Lanthanide-based single-molecule magnets (Ln-SMM) represent a class of molecular compounds that have an energy barrier for the slow relaxation of magnetization due to their strong magnetic anisotropies.1 Ln-SMMs can also retain their induced magnetization long enough to show magnetic hysteresis below a certain blocking temperature (Tb), which would be an approximate upper limit for the operating temperature of any SMM-based memory device. One of the most successful strategies to increase Tb in Ln-SMMs has been to maximize the magnetic anisotropy of Ln ion by optimizing the interaction between the single-ion electron density of Ln ion and the crystal (ligand) field, like in the family of lanthanide metallocenes that have the highest reported Tb, up to 80 K, to date.2–5 An alternative strategy is the so-called radical approach. In this approach the exchange interaction between the spin of a bridging radical ligand and unpaired electrons of Ln centers is utilized to enhance the magnetic properties of Ln-SMMs.6 Although radical-based Ln-SMMs show lower Tb than lanthanide metallocenes, their measured coercive fields (Hc) have been among the largest ever reported to any molecule or coordination solid.7,8
Most of the reported radical-based Ln-SMMs have only utilized strong exchange interaction between the spins of radical ligand and metal centers.6 Moreover, there is only a handful of compounds in which the stacked radicals not only act as bridging radical units between Ln centers, but they also interact with each other through the antiferromagnetic exchange interaction.9–11 In this presentation, I will talk about our recent results obtained for the dinuclear [Dy2(μ-(bpytz)2)(THMD)4] complex 1 (bpytz = 3,6-bis(3,5-dimethyl-pyrazolyl)-1,2,4,5-tetrazine; TMHD = 2,2,6,6-tetramethyl-3,5-heptanedionate) in which two radical ligands function as the single bridging π-dimer between two Dy3+ centers.11 Our findings demonstrate how the nature of the exchange interaction between radical ligands influences the magnetic properties of the investigated system through experimental and computational data. We also show with the help of model systems and quantum chemical calculations how the antiferromagnetic interaction between the stacked radical ligands can be changed to the ferromagnetic that further promotes the ferromagnetic interaction between radicals and metal centers.
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