Zn-Templated synthesis of substituted (2,6-diimine)pyridine proligands and evaluation of their iron complexes as anolytes for flow battery applications

Pseudo-octahedral iron complexes supported by tridentate N ^ N ^ N -binding, redox 'non-innocent' diiminepyridine (DIP) ligands exhibit multiple reversible ligand-based reductions that suggest the potential application of these complexes as anolytes in redox flow batteries (RFBs). When bea...

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Bibliographic Details
Published in:Dalton transactions : an international journal of inorganic chemistry 2020-11, Vol.49 (45), p.16175-16183
Main Authors: Braun, Jason D, Gray, Paul A, Sidhu, Baldeep K, Nemez, Dion B, Herbert, David E
Format: Article
Language:English
Subjects:
Aniline
Anolytes
Aromatic compounds
Coordination compounds
Crystallography
Electrochemical analysis
Iron
Ligands
Rechargeable batteries
Substitutes
Synthesis
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Summary:Pseudo-octahedral iron complexes supported by tridentate N ^ N ^ N -binding, redox 'non-innocent' diiminepyridine (DIP) ligands exhibit multiple reversible ligand-based reductions that suggest the potential application of these complexes as anolytes in redox flow batteries (RFBs). When bearing aryl groups at the imine nitrogens, substitution at the 4-position can be used to tune these redox potentials and impact other properties relevant to RFB applications, such as solubility and stability over extended cycling. DIP ligands bearing electron-withdrawing groups (EWGs) in this position, however, can be challenging to isolate via typical condensation routes involving para -substituted anilines and 2,6-diacetylpyridine. In this work, we demonstrate a high-yielding Zn-templated synthesis of DIP ligands bearing strong EWGs. The synthesis and electrochemical characterization of iron( ii ) complexes of these ligands is also described, along with properties relevant to their potential application as RFB anolytes. Zn 2+ templating enables synthesis of redox 'non-innocent' diimine pyridine ligands with strong electron-withdrawing groups, allowing construction of iron complexes with multiple ligand-based reductions for application in redox flow batteries.
ISSN:1477-9226
1477-9234
DOI:10.1039/d0dt00543f