Data relevant to the methods of synthesis of various verdazyl mono-,, bi-, tri-, and poly-radicals as well as their analogues (tetra-azapentenyl, tetrazolinyl, and phototetrazolinyl radicals) are discussed, and the reactions of verdazyls not involving the free valence are considered; data are presented on the structures, spectra, and physical and chemical properties of verdazyls. Attention has been concentrated on problems of the kinetics and mechanisms of chemical reactions involving verdazyls. Problems of the practical applications of verdazyls in chemical, physical, and biological research (inhibition of free-radical reactions, stabilisation of polymeric materials, spin labels, redox indicators, galvanic cells, etc.) as well as the prospects for the development of this new class of stable radicals are discussed. The bibliography includes 242 references. CONTENTS

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The unrestricted HF method in the INDO approximation with optimized geometry was used to describe the electronic structure of the hetero-ring of verdazyl and the derivatives of the latter. The results obtained are in good agreement with the experimental EPR spectra of triphenylverdazyl radical and its dipole moment. These data may be a basis for understanding and predicting the chemical properties and reactivity of verdazyl and its derivatives. The changes in spatial and electronic structure of the verdazyl radical and its ions are of great significance for understanding their reactivity in the reactions mentioned above.In this paper we cite the results of quantum investigations of a model heteroring of the verdazyl radical (VJ, its cation (V') and anion (V-) by the INDO method with total geometry optimization [S]. These results make it possible to interpret some specific features of the electronic structure of these compounds and approach well-founded prognoses related to their reactivity.

Die Benzothiadiazine (I) werden durch Dechlorierung mit Natriumpulver in die entsprechenden π‐Radikale (II) übergeführt, die in Benzol oder THF eine Lebensdauer von mehreren Tagen haben.