Insights into Molecular Magnetism in Metal-Metal Bonded Systems as Revealed by a Spectroscopic and Computational Analysis of Diiron Complexes

Abstract

A pair of bimetallic compounds featuring Fe-Fe bonds, [Fe(iPrNPPh2)3FeR] (R = PMe3, NtBu), have been investigated using High-Frequency Electron Paramagnetic Resonance (HFEPR) as well as field- A nd temperature-dependent 57Fe nuclear γresonance (Mössbauer) spectroscopy. To gain insight into the local site electronic structure, we have concurrently studied a compound containing a single Fe(II) in a geometry analogous to that of one of the dimer sites. Our spectroscopic studies have allowed for the assessment of the electronic structure via the determination of the zero-field splitting and 57Fe hyperfine parameters for the entire series. We also 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 this study, we discuss strategies for the design of single-molecule magnets based on polymetallic compounds linked via direct metal-metal bonds.