Persistent, highly localized, and tunable [4]helicene radicals

Shaikh, Aslam C.; Moutet, Jean‐Claude; Veleta, José M; Hossain, Md Mubarak; Bloch, Jan; Astashkin, Andrei V.; Gianetti, Thomas L.

doi:10.1039/d0sc04850j

Cited by 30 publications

(28 citation statements)

References 52 publications

(80 reference statements)

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“…We also reduced 9‐mesityl‐10‐methylacridinium ([ 2 ] + ), known as Fukuzumi's photoredox catalyst, [2a] to generate 2 . , a radical whose stability is reminiscent of that recently described for related dimethoxyquinacridinyl radicals [13] . This radical, the structure of which was confirmed by X‐ray analysis, [14] features an EPR spectrum analogous to that of 1 .…”

Section: Figuresupporting

confidence: 53%

Conformational Switching through the One‐Electron Reduction of an Acridinium‐based, γ‐Cationic Phosphine Gold Complex

Liu

Kim

Gabbaı̈

2021

Chemistry A European J

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Our efforts in the chemistry of gold complexes featuring ambiphilic phosphine‐carbenium L/Z‐type ligand have led us to consider the reduction of the carbenium moiety as a means to modulate the gold–carbenium interaction present in these complexes. Here, it was shown that the one‐electron reduction of [(o‐Ph2P(C6H4)Acr)AuCl]+ (Acr=9‐N‐methylacridinium) produces a neutral stable radical, the structure of which showed a marked increase in the Au–Acr distance. Related structural changes were observed for the phosphine oxide analogue [(o‐Ph2P(O)(C6H4)Acr]+, the reduction of which interfered with the P=O→carbenium interaction. These structural effects, driven by a reduction‐induced change in the electronic and electrostatic characteristics of the compounds, showed that the charge and accepting properties of the carbenium unit can be modulated. These results highlight the redox‐noninnocence of carbenium Z‐type ligand, a feature that can be exploited to induce specific conformational changes.

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Section: Figuresupporting

confidence: 53%

Conformational Switching through the One‐Electron Reduction of an Acridinium‐based, γ‐Cationic Phosphine Gold Complex

Liu

Kim

Gabbaı̈

2021

Chemistry A European J

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“…24 Similarly, our group recently reported the chemical reduction of a series of these cations leading to the isolation and characterization of the corresponding neutral radical analog (DMQA • ). 25 We also demonstrated that the helicene [ n Pr-DMQA][BF 4 ] salt (C + , Figure 2a) is an efficient photocatalyst undergoing both chemical reduction and oxidation reactions via single-electron transfer. 26 Yet, the use of these redox-active compounds has never been reported in electrochemical and energy storage applications.…”

mentioning

confidence: 77%

Symmetric, Robust, and High-Voltage Organic Redox Flow Battery Model Based on a Helical Carbenium Ion Electrolyte

Moutet

Veleta

Gianetti

2020

ACS Appl. Energy Mater.

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Redox flow batteries (RFBs) represent a promising technology for grid-scale integration of renewable energy. However, crosscontamination problems, encountered with distinct catholyte and anolyte, limit the development of reliable organic RFBs. Herein, we report the first use of a helical carbocation with three oxidation states, for the development of symmetric cells. Essential kinetic properties of this molecule were assessed by cyclic voltammetry. Its stability was then evaluated by mono-and bielectronic cycling experiments, resulting in 550 and 80 cycles respectively, with high-capacity retention. This helical ion-based electrolyte achieved a proof-of-principle 2.12 V open circuit potential as an all-organic nonaqueous symmetric RFB.

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“…The one-electron process at E1/2 Red2 = -1.67 V is attributed to the NO2 C • / NO2 C ••transformation. 41,46 Upon scanning toward the cathodic region, a one-electron oxidation wave is observed at E1/2 Ox = 1.35 V, which is assigned to the NO2 C •++ / NO2 C + redox couple, and was 310 mV higher than the…”

Section: Electrochemical Studiesmentioning

confidence: 98%

Increased Performance of an all-Organic Redox Flow Battery model by Nitration of the [4]Helicenium Ion Electrolyte

Moutet

Mills

Hossain

et al. 2021

Preprint

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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 Symmetrical all-Organic Redox Flow Batteries (SORFBs) emerging, 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 ion core (DMQA + ) result in a significant enhancement of the electrochemical performance of DMQA as electrolyte for SORFBs. The physical and kinetic properties of NO2 C + were evaluated by cyclic voltammetry (CV) and UV-visible spectroscopy in acetonitrile and compared to those of its precursor H C + . The electrons storage ability of NO2 C + was investigated in three differents type of static H-cell experiments. In the first experiment, NO2 C + provided an open circuit voltage (OCV) of 2.24 V and 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 NO2 C + (OCV > 3 V) resulted in 80 cycles at a potential energy density above 12 Wh/L. During the last epxeriment, a bipolarization stress-test was performed during which NO2 C + demonstrated a remarkable durability of 90 cycles at 100% load with a perfect retention of capacity and coulombic efficiency. The electrochemical performance results of this enhanced redox material highlights that DMQA + ions are robust and versatile materials for the emergence of symmetrical all-Organic ORFB

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Persistent, highly localized, and tunable [4]helicene radicals

Abstract: We report a series of tunable and persistent [4]-helicene neutral radicals by chemical reduction of the [4]-helicenium cation analogue. EPR spectroscopy and DFT calculations indicate that the unpaired electron is localized at the central carbon atom.

Cited by 30 publications

References 52 publications

Conformational Switching through the One‐Electron Reduction of an Acridinium‐based, γ‐Cationic Phosphine Gold Complex

Conformational Switching through the One‐Electron Reduction of an Acridinium‐based, γ‐Cationic Phosphine Gold Complex

Symmetric, Robust, and High-Voltage Organic Redox Flow Battery Model Based on a Helical Carbenium Ion Electrolyte

Increased Performance of an all-Organic Redox Flow Battery model by Nitration of the [4]Helicenium Ion Electrolyte

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