Radical anions of electron-deficient systems are widely used, but are easily reoxidized upon exposure to air. Therefore, the stabilization of radical anions under ambient conditions is of great significance, but still remains a scientific challenge. Herein, perylenediimide is employed to prepare a crystalline metal-organic framework for stabilizing radical anions without extensive chemical modification. The porous, three-dimensional framework of perylenediimide can trap electron donors such as amine vapors and produce radical anions in-situ through photo-induced electron transfer. The radical anions are protected against quenching by shielding effect in air and remain unobstructed in air for at least a month. Because of the high yield and stability of the radical anions, which are the basis for near-infrared photothermal conversion, the framework shows high near-infrared photothermal conversion efficiency (η = 52.3%). The work provides an efficient and simple method towards ambient stable radical anions and affords a promising material for photothermal therapy. Perylenediimide (PDI) radical anions show promise as photothermal agents for phototherapy, but are typically very unstable. Here the authors fabricate a PDI-based metal-organic framework where the PDI units become stable radical anions upon incorporation of amine vapors.

/pdf/stable-radical-anions-generated-from-a-porous-9n4pybtr11.pdf

Stable radical anions generated from a porous perylenediimide metal-organic framework for boosting near-infrared photothermal conversion.

With their versatile absorption, fluorescence, n-type semiconducting and (photo-)stability properties, perylene bisimides have evolved as the most investigated compounds among polycyclic aromatic hydrocarbons during the last decade. In this review we collect the results from about 200 original publications, reporting a plethora of new perylene bisimide derivatives whose properties widely enrich the possibility for the application of these dyes beyond traditional fields. While some applications are highlighted, different from other recent reviews, our focus here is on the advances in the synthetic methodologies that have afforded new bay functionalizations, recently addressed functionalizations at the ortho-positions to the carbonyl groups, and annulation of carbo- and heterocyclic units. An impressive number of perylene bisimide oligomers are highlighted as well which are connected by single bonds or spiro linkage or in a fused manner, leading to arrays with fascinating optical and electronic properties.

https://pubs.rsc.org/en/content/articlepdf/2019/qo/c8qo01368c

Progress in the synthesis of perylene bisimide dyes

Naphthalene and perylene diimides – better alternatives to fullerenes for organic electronics?

In the last few years, air-stable organic radicals and radical polymers have attracted tremendous attention due to their outstanding performance in flexible electronic devices, including transistors, batteries, light-emitting diodes, thermoelectric and photothermal conversion devices, and among many others. The main issue of radicals from laboratory studies to real-world applications is that the number of known air-stable radicals is very limited, and the radicals that have been used as materials are even less. Here, the known and newly developed air-stable organic radicals are summarized, generalizing the way of observing air-stable radicals. The special electric and photophysical properties of organic radicals and radical polymers are interpreted, which give radicals a wide scope for various of potential applications. Finally, the exciting applications of radicals that have been achieved in flexible electronic devices are summarized. The aim herein is to highlight the recent achievements in radicals in chemistry, materials science, and flexible electronics, and further bridge the gap between these three disciplines.

Air-Stable Organic Radicals: New-Generation Materials for Flexible Electronics?

In this review, we describe the developments in the field of naphthalene diimides (NDIs) from 2016 to the presentday. NDIs are shown to be an increasingly interesting class of molecules due to their electronic properties, large electron deficient aromatic cores and tendency to self-assemble into functional structures. Almost all NDIs possess high electron affinity, good charge carrier mobility, and excellent thermal and oxidative stability, making them promising candidates for applications in organic electronics, photovoltaic devices, and flexible displays. NDIs have also been extensively studied due to their potential real-world uses across a wide variety of applications including supramolecular chemistry, sensing, host–guest complexes for molecular switching devices, such as catenanes and rotaxanes, ion-channels, catalysis, and medicine and as non-fullerene accepters in solar cells. In recent years, NDI research with respect to supramolecular assemblies and mechanoluminescent properties has also gained considerable traction. Thus, this review will assist a wide range of readers and researchers including chemists, physicists, biologists, medicinal chemists and materials scientists in understanding the scope for development and applicability of NDI dyes in their respective fields through a discussion of the main properties of NDI derivatives and of the status of emerging applications.

Naphthalene diimides: perspectives and promise.

Arylenediimides are inherently electron deficient and provide enormous opportunities to conjugate electron withdrawing substituents in different regions of the π-scaffold. This review article highlights the gradual emergence of diverse molecular design principles to realize exceptionally electron deficient arylenediimide molecules. Interestingly, non-conventional electron withdrawing substituents allow the realization of some of the strongest electron acceptors known from this class of molecules. Thus, an enthralling and exceptionally close race to garner the top position within the electron deficient molecules unfolds, which has immense implications with regard to stability and potential applications.

Electron-poor arylenediimides

The review presents an overview of the organic radicals that have been designed and synthesized recently, and their magnetic properties are discussed. The π-conjugated organic radicals such as phenalenyl systems, functionalized nitronylnitroxides, benzotriazinyl, bisthiazolyl, aminyl-based radicals and polyradicals, and Tetrathiafulvalene (TTF)-based H-bonded radicals have been considered. The examples show that weak supramolecular interactions play a major role in modulating the ferromagnetic and antiferromagnetic properties. The new emerging direction of zethrenes, organic polyradicals, and macrocyclic polyradicals with their attractive and discrete architectures has been deliberated. The magnetic studies delineate the singlet-triplet transitions and their corresponding energies in these organic radicals. We have also made an attempt to collate the major organic neutral radicals, radical ions and radical zwitterions that have emerged over the last century.

Recent Advances in Organic Radicals and Their Magnetism

Reported herein is the first isolation of tetracyano-naphthalenediimide [NDI(CN)4 ] and its radical anion, and structural elucidation through spectroscopic and X-ray diffraction studies. The radical anion shows remarkable stability and was purified by chromatography, which is unique for planar radical anions. The stability results from multiple hydrogen bonds to the counter ion and through an array of intramolecular noncovalent interactions. The radical anion revealed one of the strongest NDI π-π interactions (3.268 A). Electrochemical studies of [NDI(CN)4 ] confirm its extraordinarily low-lying LUMO (-5.0 eV), rendering it one of the strongest electron-deficient planar π systems to be isolated. The manifold potential, which remained unknown to date, can now be explored for these open- and closed-shell planar π systems.

Yogendra Kumar

Papers

Electron-poor arylenediimides

Recent Advances in Organic Radicals and Their Magnetism

Isolation of Tetracyano-Naphthalenediimide and Its Stable Planar Radical Anion.

Synthesis of Octabromoperylene Dianhydride and Diimides: Evidence of Halogen Bonding and Semiconducting Properties

Synthesis and Isolation of a Stable Perylenediimide Radical Anion and Its Exceptionally Electron-Deficient Precursor