Accurate 19F NMR Chemical Shifts in Fe(II) Complexes with the LH20t Local Hybrid Functional

Abstract

For a series of fluorinated Fe(II) complexes, both previously reported and newly synthesised, we present a first benchmarking study for ¹⁹F NMR shifts using global and local hybrid density functionals. Our results demonstrate that the use of the local hybrid functional LH20t in combination with a moderately sized pcSseg-2 basis set provides highly accurate results at a moderate computational cost. Compared to the global hybrid density functionals PBE0, TPSSh, and B3LYP, the local hybrid density functional LH20t offers significantly improved agreement with experiment. In some cases, structural flexibility leads to significant uncertainties, which can be addressed with conformer-rotamer sampling as demonstrated for an Fe(II) porphyrin complex. In rigid systems, LH20t is able to unravel ¹⁹F positions in crowded spectral regions, as is exemplified by the correct assignment of facial and meridional isomers of an iron bipyridine complex.