Presentation Title

Iron (II) Pyridinediimine Complexes with Lewis Acids in the Secondary Coordination Sphere

Presentation Type

Poster

Abstract

In many biological and synthetic systems, electron-transfer reactions by redox-active transition metals often function by participating with redox-inactive metals to facilitate reactivity, such as the potassium-promoted iron surfaces used in the Haber-Bosch process, or the Ca2+ ion in the oxygen evolving complex of photosystem II. Inclusion of these redox-inactive Lewis acids have been shown to enhance electron-transfer rates and tune reduction potentials in synthetic chemical systems, as well as facilitate H-H, N-N and O-O bond cleavage.

In this work, 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. This lead to a redox active metal-ligand complex with a Lewis acid in secondary sphere, as these pockets are perfectly sized to house metal ions such as Na+. We report here the synthesis and characterization of these complexes, including NMR analysis of the effect of binding Na+ in the pocket as well as electrochemical studies, which have demonstrated that these complexes exhibit modest shifts in the reduction potential of the metal-ligand scaffold upon encapsulation.

Start Date

6-5-2017 12:15 PM

End Date

6-5-2017 2:00 PM

Location

Miller Hall

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May 6th, 12:15 PM May 6th, 2:00 PM

Iron (II) Pyridinediimine Complexes with Lewis Acids in the Secondary Coordination Sphere

Miller Hall

In many biological and synthetic systems, electron-transfer reactions by redox-active transition metals often function by participating with redox-inactive metals to facilitate reactivity, such as the potassium-promoted iron surfaces used in the Haber-Bosch process, or the Ca2+ ion in the oxygen evolving complex of photosystem II. Inclusion of these redox-inactive Lewis acids have been shown to enhance electron-transfer rates and tune reduction potentials in synthetic chemical systems, as well as facilitate H-H, N-N and O-O bond cleavage.

In this work, 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. This lead to a redox active metal-ligand complex with a Lewis acid in secondary sphere, as these pockets are perfectly sized to house metal ions such as Na+. We report here the synthesis and characterization of these complexes, including NMR analysis of the effect of binding Na+ in the pocket as well as electrochemical studies, which have demonstrated that these complexes exhibit modest shifts in the reduction potential of the metal-ligand scaffold upon encapsulation.