(6fq) Radical-Bridged Dinuclear, Trinuclear and Metallacyclic Lanthanide Molecular Magnets

Single molecule magnets (SMMs) are compounds that exhibit slow relaxation of magnetization. These molecules are approximately 1 nm in size. This size is approximately 100 times smaller than current nanoparticle-sized permanent magnets and represent the next generation of magnetic data storage materials. The quality of an SMM can be measured by the thermal energy barrier to reversal of magnetization (U_eff) and the magnetic blocking temperature (T_B). In lanthanide compounds, the magnetic anisotropy of the Ln³⁺ ions gives rise to high thermal energy barriers. Despite recent advances in mononuclear lanthanide SMMs that have resulted in astonishing thermal barriers of > 1000 K, the highest blocking temperature recorded for SMMs has only reached 20 K. The lack of high blocking temperatures in SMMs primarily results from quantum tunneling of magnetization (QTM), which serves to circumvent the thermal barrier by providing alternative relaxation pathways. QTM can be mitigated by using ligands that promote strong magnetic coupling between metal centers in an SMM.In lanthanide complexes, the valence 4f-orbitals are contracted, making it difficult for them to achieve high coupling constants.

Utilization of open-shell ligands to bridge lanthanide ions has recently gained traction as a method for improving the magnetic properties SMMs. Polylanthanide complexes bridged by closed shell ligands (e.g. CN^-, CH₃COO^-, OH^-, O^2-) typically display very weak magnetic superexchange interactions between the lanthanide centers. As a result of this weak superexchange, the lanthanides in such complexes typically exhibit single-ion effects, rather than acting as a coupled unit. In contrast, open-shell bridging ligands engender direct exchange interactions with the lanthanide ions, leading to higher degrees of magnetic coupling and improved SMM behavior.

In this poster, I will describe my PhD research in the field of transition metal metal-metal bonded complexes as well as my postdoctoral research into the synthesis and magnetic characterization of the aforementioned radical-bridged SMMs. This postdoctoral research has led to a recent successful NSF proposal. I will also detail my plans to merge these two fields in my independent career through the synthesis of metal-metal bonded molecular magnets. Such compounds will leverage direct exchange coupling mechanisms to produce superior molecular magnets.

Teaching Interests:

In graduate school at UW-Madison, I had ample Teaching Assistant experience for four semesters. In my TAship, I led discussion sections twice a week in which I planned and taught lessons to the students to supplement what they learned in the corresponding lectures for the course. For two semesters, I was awarded an Honored Instructor recognition for my teaching.

In my postdoctoral research, I planned and delivered a short workshop detailing the problems encountered in the course of solving and refining small-molecule X-ray crystallographic structures.

Selected Publications:

1. Dolinar, B. S.; Alexandropoulos, D. I.; Vignesh, K. R.; James, T.; Dunbar, K. R., Lanthanide Triangles Supported by Radical Bridging Ligands. Am. Chem. Soc., 2018, 140, 908-911.
2. Dolinar, B. S.; Gómez-Coca, S.; Alexandropoulos, D. I.; Dunbar, K. R., An Air Stable Radical-Bridged Dysprosium Single Molecule Magnet and Its Neutral Counterpart: Redox Switching of Magnetic Relaxation Dynamics. Commun. 2017, 53, 2283-2286.
3. Dolinar, B. S.; Kozimor, S. A.; Berry, J. F., K₃[Mo₂(SNO5)₄Cl]₃[Mo₂(SNO5)₄]: The First Example of a Heterometallic Extended Metal Atom Node (HEMAN). Dalton Trans. 2016, 45, 17602-17605.
4. Dolinar, B. S.; Berry, J. F., Influence of Lewis acid charge and proximity in MoMo∙∙∙M linear chain compounds with M = Na⁺, Ca²⁺, Sr²⁺, and Y³⁺. Polyhedron, 2016, 103, 71-78.
5. Dolinar, B. S.; Berry, J. F., Electronic tuning of Mo₂(thioamidate)₄ complexes through π-system substituents and cis/trans Dalton Trans. 2014, 43, 6165-6176.
6. Dolinar, B. S.; Berry, J. F., Lewis Acid Enhanced Axial Ligation of [Mo₂]⁴⁺Inorg. Chem. 2013, 52, 4658-4667.