Making Oxidation Potentials Predictable: Coordination of Additives Applied to the Electronic Fine Tuning of an Iron(II) Complex

This
work examines the impact of axially coordinating additives on the
electronic structure of a bioinspired octahedral low-spin iron­(II)
N-heterocyclic carbene (Fe-NHC) complex. Bearing two labile trans-acetonitrile ligands, the Fe-NHC complex, which is
also an excellent oxidation catalyst, is prone to axial ligand exchange.
Phosphine- and pyridine-based additives are used for substitution
of the acetonitrile ligands. On the basis of the resulting defined
complexes, predictability of the oxidation potentials is demonstrated,
based on a correlation between cyclic voltammetry experiments and
density functional theory calculated molecular orbital energies. Fundamental
insights into changes of the electronic properties upon axial ligand
exchange and the impact on related attributes will finally lead to
target-oriented manipulation of the electronic properties and consequently
to the effective tuning of the reactivity of bioinspired systems.