Abstract: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.

This review article highlights the emergence of eclectic molecular design principles to realize remarkably strong electron deficient arylenediimide molecules, aspects of their stability and associated applications.

Reported herein is the first isolation of tetracyanonaphthalenediimide [NDI(CN) 4 ]a nd its radical anion, and structural elucidation through spectroscopic and X-rayd iffraction studies.T he radical anion shows remarkable stability and was purified by chromatography,w hich is unique for planar radical anions.T he stability results from multiple hydrogen bonds to the counter ion and through an array of intramolecular noncovalent interactions.T he radical anion revealed one of the strongest NDI p-p interactions (3.268 ). Electrochemical studies of [NDI(CN) 4 ]c onfirm its extraordinarily low-lying LUMO (À5.0 eV), rendering it one of the strongest electron-deficient planar p systems to be isolated. The manifold potential, whichremained unknown to date,can now be explored for these open-and closed-shell planar p systems.Planar p-conjugated radical anions [1][2][3][4] and highly electron-Angewandte Chemie

The synthesis and isolation of an ambient stable perylenediimide radical anion is reported, and its precursor is established as one of the strongest electron acceptors. The radical anion shows absorption up to 1400 nm and is stable in mixed aqueous solution. Interestingly, the radical anion can organize two electron-deficient molecules over its surface to form a π-stacked array. Calculations revealed weak spin polarization via noncovalent interactions. Such interactions are of significance for magnetic exchange and catalysis.

Green synthetic routes to a library of twenty four diphosphonium substituted naphthalenediimide (NDI) radical ions [NDI(PR3)2]˙+ Br− (R = alkyl/aryl) with excellent yields and stability are reported.