Increased performance of an all-organic redox flow battery model: Via nitration of the [4]helicenium DMQA ion electrolyte

Redox flow batteries (RFBs), through their scalable design and virtually unlimited capacity, are promising candidates for large-scale energy storage. While recent advances in the development of redox-active bipolar organic molecules satisfy the prerequisites for the pioneering emergence of symmetrical all-organic redox flow batteries (SORFBs), problems of low durability or low energy density remain a bottleneck for their wide-spread application. The present work reports that nitration of the [4]helicenium dimethoxyquinacridinium (DMQA+) ion core (NO2C+) results in a significantly enhanced electrochemical performance of DMQA+ as the electrolyte for SORFBs. The physical and kinetic properties of NO2C+ were evaluated by cyclic voltammetry (CV) and UV-visible spectroscopy in acetonitrile and compared to those of its precursor (HC+). The ability for electron storage of NO2C+ was investigated in three different types of static H-cell experiments. In the first experiment, NO2C+ provided an open circuit voltage (OCV) of 2.24 V resulting in demonstrated good stability, as well as high coulombic (>98%) efficiencies, over more than 200 charge/discharge cycles. In the second experiment, a charge-discharge cycling over the entire redox window of NO2C+ (OCV > 3 V) resulted in 80 cycles at a potential energy density above 12 W h L-1. During the last experiment, a bipolarization stress-test was performed in which NO2C+ demonstrated a remarkable durability of 90 cycles at 100% load with a perfect retention of capacity and coulombic efficiency. The enhanced electrochemical performance of this redox material highlights that DMQA+ ions are robust and versatile materials for the emergence of SORFBs. © 2021 The Royal Society of Chemistry.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Low-valent iron mono-diazadiene compounds: electronic structure and catalytic application

A series of monodiazadiene diolefin iron compounds, [Fe(trop(2)dad)(L)] (4; L = neutral ligand), has been prepared by one-electron oxidation of the Fe-I species [NaFe-(trop(2)dad)(thf)(3)] (dad = diazadiene; trop = 5H-dibenzo[a,d]-cyclohepten-5-yl). The electronic structures of compounds 4 were investigated by NMR and Mossbauer spectroscopy, single-crystal X-ray diffraction, solid- and liquid-phase magnetic susceptibility measurements, and DFT calculations. Compounds of type 4 with labile ligands L were found to be active (pre)catalysts for the dehydrogenative coupling of (alkyl)amine-boranes. Remarkably high activities were observed, especially for the homogeneous dehydrogenative polymerization of methylamine-borane