Organic Polyradicals as Redox Mediators: Effect of Intramolecular Radical Interactions on Their Efficiency

Abstract

The spin−spin interactions between unpaired electrons in organic (poly)radicals, especially nitroxides, are largely investigated and are of crucial importance for their applications in areas such as organic magnetism, molecular charge transfer, or multiple spin labeling in structural biology. Recently, 2,2,6,6-tetramethylpiperidinyloxyl and polymers functionalized with nitroxides have been described as successful redox mediators in several electrochemical applications; however, the study of spin−spin interaction effect in such an area is absent. This communication reports the preparation of a novel family of discrete polynitroxide molecules, with the same number of radical units but different arrangements to study the effect of intramolecular spin−spin interactions on their electrochemical potential and their use as oxidation redox mediators in a Li−oxygen battery. We find that the intensity of interactions, as measured by the d 1 /d electron paramagnetic resonance parameter, progressively lowers the reduction potential. This allows us to tune the charging potential of the battery, optimizing its energy efficiency.

Total Synthesis of the Antimycobacterial Natural Product Chlorflavonin and Analogs via a Late-Stage Ruthenium(II)-Catalyzed ortho-C(sp2)-H-Hydroxylation

“…The structure of chlorflavonin was elucidated via 1 H-and 13 C-NMR, which agrees with the spectral data published and discussed by Rehberg et al [14]. according to the literature [39][40][41][42][43][44][45]. Analogs 17a-p were synthesized according to Scheme 3.…”

“…To analyze the importance of the 2 -hydroxy group, we replaced it with the bioisosteric difluoromethoxy group and a chlorine or fluorine substituent [36][37][38]. The salicylic aldehyde starting materials and several MOM-protected salicylic aldehydes were purchased or synthesized according to the literature [39][40][41][42][43][44][45]. Analogs 17a-p were synthesized according to Scheme 3.…”

Innovative Construction of the Cobalt Metal Complex Redox Electrolyte and Octahedron Structure of the Cobalt Metal Organic Framework Electrode in the Energy Storage and Energy Conversion System

“…24 TEMPO is an organic material, which acts as a highly effective redox mediator with the carbon electrode, and they have optimized electrochemical properties. 25 Here, in this work, we introduced our newly synthesized cobalt redox mediator incorporated along with the KOH electrolyte that increases fast ion transport toward the anode and cathode. This designed redox mediator material has been proven as a high electroactive material.…”

“…One of the other best redox mediators is the H 2 SO 4 + hydroquinone electrolyte with a carbon electrode capacitance of 901 F g –1 . TEMPO is an organic material, which acts as a highly effective redox mediator with the carbon electrode, and they have optimized electrochemical properties . Here, in this work, we introduced our newly synthesized cobalt redox mediator incorporated along with the KOH electrolyte that increases fast ion transport toward the anode and cathode.…”

Electronic and Magnetic Properties of a Three-Arm Nonconjugated Open-Shell Macromolecule

“…For instance, linear radical polymers are composed of a nonconjugated backbone with stable open-shell pendant groups, and they have shown great promise in electronic and electrochemical applications due to their tunable molecular design and relatively simple syntheses. , As a result, they have been widely used in several emerging applications (e.g., flexible batteries). − However, early work on the magnetic properties of these radical polymers showed weak magnetic interactions between the open-shell sites. − Unlike polyradicals, radical polymers have only a single unpaired electron per repeat unit and they are usually completely amorphous in the solid state, which can limit spin ordering. Additionally, while radical polymers contain a large number of open-shell sites as a whole, the distance between these sites is much larger than that in polyradicals.…”