Western CEDAR

Enticing anion reduction with Lewis acids in the secondary coordination sphere of iron (II) pyridinediimine complexes

Electron-transfer reactions by redox-active transition metals often function by participating with redox-inactive metals, facilitating reactivity. A notable example in biological system being the Ca²⁺ ion in the oxygen evolving complex of PSII. Inclusion of these redox-inactive Lewis acids has been shown to enhance electron-transfer rates and tune reduction potentials in synthetic systems. We set out to design this feature into the redox non-innocent pyridinediimine (PDI) scaffold by synthesizing a family of Iron (II) pyridinediimine complexes with a 15-crown-5 ether moiety located in the secondary coordination sphere, leading to redox active metal-ligand complexes with Lewis acids in the secondary sphere. Here we report the synthesis and characterization of these complexes, as well as kinetic studies which demonstrate the modest enhancement in reaction kinetics by luring in reactive anion species.