The ability to chemically tailor the magnetic properties of coordination compounds containing multiple spin carrying metals has long been a goal in molecular magnetism research. Of particular interest is the tunability of the zero field splitting parameters which, when properly tuned, can provide a barrier to the reversal of magnetization in single-molecule magnets (SMMs). A great deal of this work has focused on exchange-coupled clusters where the interaction between magnetic ions is mediated by a (usually) diamagnetic bridging group. While this superexchange interaction can generate a large ground state spin, the weak coupling results in a poorly isolated ground state, rendering the barrier only effective at relatively low temperatures. Recently, SMM behavior has been observed in a Fe6 cluster (JACS, 2015, 137, 13949-13956) where the Fe centers are linked via direct Fe-Fe bonds. Here we present the results of a high-frequency electron paramagnetic resonance (HFEPR) study of this novel cluster. We will then discuss a combined HFEPR and field- and temperature-dependent 57Fe nuclear gamma resonance (Mössbauer) spectroscopic investigation of a pair of bimetallic compounds featuring Fe-Fe bonds (Inorg. Chem., 2013, 52, 4802−4811). Our spectroscopic studies have allowed us to assess the electronic structure of these compounds via the determination of their zero field splitting and 57Fe hyperfine parameters. Finally, we report on our efforts to correlate structure with physical properties in metal-metal bonded systems using ligand field theory guided by quantum chemical calculations. Through the insight gained in the study of these diiron compounds, we propose a strategy for the design of SMMs based on polymetallic compounds linked via covalent bonds.

Magnetic resonance investigations of systems featuring metal-metal bonds: Insights into the design of single-molecule magnets

2019 Spring National Meeting

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