Electron-Spin Resonance Studies of Short-Lived Organic Radicals

Abstract

Electron-spin resonance (e.s.r.) spectroscopy is a technique for the study of species containing one or more unpaired electrons. The scope of the method includes the detection and characterization of some transition-metal ions, simple molecules and ions and organic radicals, including biradicals and triplet states. This chapter discusses the role of electron-spin resonance (e.s.r.) in the characterization of short-lived organic radicals in solution, with particular reference to the information obtainable about these radicals and the mechanisms of the reactions in which they take part. The advantages of electron-spin resonance (e.s.r.) over other magnetic methods for studying free radicals are discussed. The general principles of electron-spin resonance (e.s.r.) are also discussed and the use of the method in the examination of organic radicals both in solution and trapped in solids is reviewed. Later, the study of radicals trapped in single crystal is reviewed and the results obtained for aromatic radical-ions and their relevance to valence theory is presented.