Using Proximal Cations to Install Internal Electric Fields in Transition Metal
Non-redox active Lewis acidic metal cations play a key role in a diverse set of biological and synthetic transition metal complexes that mediate redox activity. One of their proposed roles in promoting reactivity is by tuning the redox potential of the reaction site. We investigated whether non-redox active cations engender this change through an inductive effect, which would change the electronic structure of the redox active cation, or through an electrostatic effect, which would uniformly shift the molecular orbitals on the redox active metal due to the electric field potential of the proximal cation. Our study, which utilized a Schiff base ligand with an appended crown-like functionality that incorporates a variety of alkali and alkaline earth metals, indicates an electrostatic effect is likely dominant. The effect of the electric field on reactivity and thermochemical properties will be discussed.
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