Platforms for Stable Carbon‐Centered Radicals

Abstract

Organic radicals can potentially play important roles in functional materials owing to an unpaired electron, but they are usually highly reactive and difficult to use. Therefore, stabilization of organic radicals is important. Among organic radicals, carbon‐centered radicals are promising because of their trivalent nature, which enables structural diversity and elaborate designs, but they are also less stable because of the reactivities towards carbon–carbon bond formation and atmospheric oxygen. Recently, stable carbon‐centered radicals across diverse molecular platforms have been increasingly explored. This Minireview highlights these newly explored, stable carbon‐centered radicals, with a focus on porphyrinoid‐stabilized radicals because of their remarkable spin delocalization abilities.

2D Hexagonal Covalent Organic Radical Frameworks as Tunable Correlated Electron Systems

“…Recently, it was proposed that by replacing the PTM rs nodes in the PTM acetylenic structure with oxo‐bridged planar TAMs, one could increase the calculated AF coupling strength by approximately four times. [ 36 ] We note that oxo‐bridged planar TAMs are relatively unstable to reaction with oxygen, [ 46 ] unlike TAMs, which are kinetically stabilized by sterically hindering access to the central αC (e.g., PTMs and TPMs). As such, 2D hex‐CORFs based on oxo‐bridged planar TAMs are unlikely to be amenable to experimental synthesis.…”

Stable N,N’‐Diarylated Dihydrodiazaacene Radical Cations

“…Acene‐based radicals and radical ions [1] are open‐shell species with particular electronic, magnetic, and optical properties; they have potential applications in spintronics, [2] organic electronics, [3] organic superconductors, [4] and energy storage devices [5] . Prerequisite for their application is stability, since they are fairly reactive and easily form closed‐shell compounds by oxidation, dimerization, and/or disproportionation [6] . At present, only a limited number of stable acene‐based radicals are described [7]…”

Tuning the stability of organic radicals: from covalent approaches to non-covalent approaches

“…14,15 Many approaches depending on covalent modication are developed to modulate the stability of radicals. 16,17 Because most organic radicals are transient, previous studies were mostly focused on the stabilization of radicals. Through different strategies, various organic radicals, including neutral radicals, radical ions, diradicals and so on, can be air-stable, water-stable, isolatable and even thermodynamically stable.…”