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Aminopolycarboxylate chelates are emerging as a promising class of electrolyte materials for aqueous redox flow batteries, offering tunable redox potentials, solubility, and pH stability through careful selection of ligands and transition metal ions. Despite their potential, the impact of molecular structure modifications on the electronic and electrochemical properties of these chelates remains underexplored. Here, we examine how introducing a hydroxyl group, often employed for its solubilizing properties, to the backbone of CrPDTA, a reference chelate material, significantly changes the thermodynamics and kinetics of the chelate's redox process. We correlate changes in molecular and electronic structures to different electrochemical responses resulting from the hydroxyl addition and show that the introduction of this functional group leads to a distortion in the octahedral coordination of chromium. Furthermore, increased anisotropic spin density and nonintegral oxidation state changes in the Cr metal center result in a larger barrier for electron transfer in CrPDTA‐OH. It is demonstrated that preserving a hexacoordinate chelate structure across a broad pH range is crucial for efficient flow battery application and it is emphasized that ligand modifications must avoid distorting the octahedral coordination of the transition metal. 

Photoinduced organocatalyzed atom-transfer radical polymerization (O-ATRP) is a controlled radical polymerization technique that can be driven using low-energy, visible light and makes use of organic photocatalysts. Limitations of O-ATRP have traditionally included the need for high catalyst loadings (1000 ppm) and the narrow scope of monomers that can be controllably polymerized. Recent advances have shown that N , N -diaryl dihydrophenazine (DHP) organic photoredox catalysts (PCs) are capable of controlling O-ATRP at PC loadings as low as 10 ppm, a significant advancement in the field. In this work we synthesized five new DHP PCs and examined their efficacy in controlling O-ATRP at low ppm catalyst loadings. We found that we were able to polymerize methyl methacrylate at PC loadings as low as 10 ppm (relative to monomer) while producing polymers with dispersities as low as Đ = 1.33 and achieving initiator efficiencies ( I* ) near unity (102%). In addition to applying these PCs in O-ATRP, we carried out a thorough investigation into the structure–property relationships of the new DHP PCs reported herein and report new photophysical characterization data for previously reported DHPs. The insight into the DHP structure–property relationships that we discuss herein will aid in the elucidation of their ability to catalyze O-ATRP at low catalyst loadings. Additionally, this work sheds light on how structural modifications affect certain PC properties with the goal of bolstering our understanding of how to tune PC structures to overcome current limitations in O-ATRP such as the controlled polymerization of challenging monomers.