The incorporation of charged cationic functionalities at transition metal complexes is an emerging strategy for introducing electrostatic interactions that can tune reduction potentials, pKa, and spin state. These effects may be attributed to the generation of local electric fields. We report a series of Fe and Mn salen complexes functionalized with a crown ether unit containing a non-redox active cation, Mn+. This talk will describe efforts toward reactivity control using electrostatic effects. For the manganese complexes, investigations on hydrogen atom transfer (HAT) reactions and breaking thermodynamic scaling relationships will be discussed. For the iron complexes, their spin-crossover behavior was explored. Incorporation of cation Mn+ to the ligand framework results in an inversion of the predicted spin populations as observed by electron paramagnetic resonance (EPR) studies. These results demonstrate the utility of proximal charged functionalities at metal salen complexes and the influence of internal electric fields toward HAT reactions and spin-state configurations.

Leveraging electric field effects to control reactivity at manganese and iron salen complexes

ACS Fall 2021

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