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Abstract Aqueous organic redox flow batteries (AORFBs) are highly attractive for large‐scale energy storage because of their nonflammability, low cost, and sustainability. (2,2,6,6‐Tetramethylpiperidin‐1‐yl)oxyl (TEMPO) derivatives, a class of redox active molecules bearing air‐stable free nitroxyl radicals and high redox potential (>0.8 V vs NHE), has been identified as promising catholytes for AORFBs. However, reported TEMPO based molecules are either permeable through ion exchange membranes or not chemically stable enough for long‐term energy storage. Herein, a new TEMPO derivative functionalized with a dual‐ammonium dicationic group,N1, N1, N1, N3, N3, 2, 2, 6, 6‐nonamethyl‐N3‐(piperidinyloxy)propane‐1,3‐bis(ammonium) dichloride (N2‐TEMPO) as a stable, low permeable catholyte for AORFBs is reported. Ultraviolet–visible (UV–vis) and proton nuclear magnetic resonance (1H‐NMR) spectroscopic studies reveal its exceptional stability and ultra‐low permeability (1.49 × 10−12 cm2 s−1). Coupled with 1,1′‐bis[3‐(trimethylammonio)propyl]‐4,4′‐bipyridinium tetrachloride ((NPr)2V) as an anolyte, a 1.35 VN2‐TEMPO/(NPr)2V AORFB with 0.5 melectrolytes (9.05 Wh L−1) delivers a high power density of 114 mW cm−2and 100% capacity retention for 400 cycles at 60 mA cm−2. At 1.0 melectrolyte concentrations, theN2‐TEMPO/(NPr)2V AORFB achieves an energy density of 18.1 Wh L−1and capacity retention of 90% for 400 cycles at 60 mA cm−2.
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Redox‐Neutral TEMPO Catalysis: Direct Radical (Hetero)Aryl C−H Di‐ and Trifluoromethoxylation
Abstract Applications of TEMPO.catalysis for the development of redox‐neutral transformations are rare. Reported here is the first TEMPO.‐catalyzed, redox‐neutral C−H di‐ and trifluoromethoxylation of (hetero)arenes. The reaction exhibits a broad substrate scope, has high functional‐group tolerance, and can be employed for the late‐stage functionalization of complex druglike molecules. Kinetic measurements, isolation and resubjection of catalytic intermediates, UV/Vis studies, and DFT calculations support the proposed oxidative TEMPO./TEMPO+redox catalytic cycle. Mechanistic studies also suggest that Li2CO3plays an important role in preventing catalyst deactivation. These findings will provide new insights into the design and development of novel reactions through redox‐neutral TEMPO.catalysis.
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- PAR ID:
- 10236954
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 59
- Issue:
- 48
- ISSN:
- 1433-7851
- Format(s):
- Medium: X Size: p. 21475-21480
- Size(s):
- p. 21475-21480
- Sponsoring Org:
- National Science Foundation
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