An Air-Stable Alkene-Derived Organic Radical Cation

Abstract

Alkenes are known to undergo oxidation to radical cations and dications. The radical cations are often highly reactive and not stable under air. Herein, we report the synthesis, isolation, characterization, and molecular structure of an alkene-derived radical cation A, which is stable in air both in the solid state and in solution. The access to this compound was facilitated from E-diamino tri-substituted alkene B as a synthon for the synthesis of A through one-electron oxidation. The E-diamino tri-substituted alkene B was synthesized by the two-electron reduction of N,N′-1,2-propylene-bridged bis-2-phenyl-pyrrolinium cation C. Under two-electron oxidation, alkene B transforms back to cation C involving a double carbocation rearrangement.

A bis-NHC–CAAC dimer derived dicationic diradical

“…Multi-reference theoretical methods are known to precisely describe the energies of singlet and triplet states. Indeed the multi-reference CASSCF(2,2)/NEVPT2/def2-TZVP approach 22 verified the singlet ground states and provided a much more accurate adiabatic Δ E ST of −0.037 kJ mol −1 .…”

Highly Stable Self‐Regenerating Organic Multi‐Redox Systems derived from Bicyclic (Alkyl)(amino)carbenes (BICAACs)

“…Carbenes such as N‐heterocyclic carbenes (NHCs) and cyclic(alkyl)(amino) carbenes (CAACs) have recently emerged as powerful tools to stabilize organic radicals [24–27] . The field of isolated air‐stable carbon‐centered radicals stabilized by NHCs and CAACs was pioneered by Bertrand, Martin, Roesky, Lee, Han and others [28–43] . However, very few carbene‐derived air‐ and moisture‐stable radicals with multiple redox states across a redox range of <1.2 V are known, which severely limits their applicability as electrolytes for continuous H‐cell cycling and leads to only a few charge/discharge cycles [40,44–45] .…”

“…[24][25][26][27] The field of isolated air-stable carbon-centered radicals stabilized by NHCs and CAACs was pioneered by Bertrand, Martin, Roesky, Lee, Han and others. [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] However, very few carbene-derived air-and moisture-stable radicals with multiple redox states across a redox range of < 1.2 V are known, which severely limits their applicability as electrolytes for continuous H-cell cycling and leads to only a few charge/discharge cycles. [40,[44][45] So, there is always an urge to synthesize such multi-redox systems with notably wide redox ranges (> 1.5 V) and which not only offer stability but also will be effective for stable H-cell 2e À charge/ discharge process for longer cycles.…”

A Long-Lived Water-Soluble Phenazine Radical Cation

“…Since the pioneering discovery of the triphenylmethyl radical by Gomberg, extensive efforts have been put forward to develop stable radicals centered on oxygen, nitrogen, carbon, and π-conjugation systems. − Among them, nitroxyl radicals are notable examples of the few radicals studied and applied under an aqueous environment, ,− but they are prone to degrade from dimerization or disproportionation to hydroxylamines and oxoammonium cations . More structurally diverse radicals, other than nitroxyl species, with good stability in water are highly desired.…”