Since the discovery of the first single molecule magnet (SMM), researchers have sought to control the slow reversal of the magnetization in molecular compounds. Early forays into this field involved maximizing the total spin, S, of the electronic ground state in large, polynuclear metal complexes. Increasing S proved to be a less than fruitful strategy, however, and researchers turned their attention to controlling the magnetic anisotropy of smaller complexes. In an effort to meet the challenge of improving the properties of molecular magnets for future device applications, our lab is investigating the use of molybdenum and tungsten complexes as building blocks for SMMs. While the inclusion of large spin-orbit coupling parameters complicates the description of SMM behavior, recent theories predict that the properties of such complexes could be significant improvements over 3d metal SMMs.1 Specifically, we are exploring the relationship between spin-orbit coupling and anisotropic coupling in heavy metal complexes. We are currently working on incorporating [MoIII(CN)7]4- into polynuclear structures, as well as synthesizing a heavier analogue, [WIII(CN)7]4-. Experimental evidence shows that anisotropic coupling can be obtained with 3d metals that are attached to the axial CN- ligands of [MoIII(CN)7]4-.2 Theoretical work reveals that the anisotropic coupling is directly related to the spin-orbit coupling of the orbitally degenerate ground state of [MoIII(CN)7]4-. We anticipate an analogous, orbitally degenerate ground state in [WIII(CN)7]4-, but with stronger spin-orbit coupling. We are also exploring MoIV and WIV trigonal bipyramidal complexes via tris-anionic ligands, which were previously investigated for catalysis purposes.3 This geometry is ideal for strong coupling through cyanide with another metal. By using theory as a guide, we aim to uncover new exciting strategies for improving SMM behavior and to expand upon the current understanding of magnetic anisotropy in metal complexes. 1 Mironov, V. S.; Chibotaru, L. F.; Ceulemans, A. J. Am. Chem. Soc. 2003, 125, 9750-9760. 2 Qian, K.; Huang, X.-C.; Zhou, C.; You, X.-Z.; Wang, X.-Y.; Dunbar, K. R. J. Am. Chem. Soc. 2013, 135, 13302-13305. 3 Kol, M.; Schrock, R. R.; Kempe, R.; Davis, W. M. J. Am. Chem. Soc. 1994, 116, 4382-4390.

Heavy element molecular magnetism: Exploiting spin-orbit effects and anisotropic coupling

251st National Meeting (2016)

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