Electron Paramagnetic Resonance Spectroscopy. Types of electronic transitions: Organics: Involving π, σ, n electrons Saturated compounds σ→σ∗ (<150 nm), n →σ∗ (<250 nm): deep UV Double bonds/unsaturated systems— • Net spin S = 0 • Some chemical species have UNPAIRED electrons • Atoms H, Na, transition metals • Recall Stern-Gerlach experiment (s = ±±±± ½) • Molecules: O 2, NO Introduction Electron spin resonance (ESR)1 has developed over the past several decades as a technique to provide information on the electronic structure of organic, inorganic, biological, solid state, and surface molecular species. 27.10: Electron-Spin Resonance (ESR) Spectroscopy of Organic Radicals Last updated; Save as PDF Page ID 22392; Contributors and Attributions; An important method of studying radicals is electron-spin resonance (ESR) spectroscopy.The principles of this form of spectroscopy are much the same as of NMR spectroscopy, but the language used by the practitioners of these two forms of … 2. Among them, a … electron spin angular momentum (half-integral spin angular momentum values are allowed; the electron has spin ½). ESR Spectroscopy • Electron Spin Resonance Spectroscopy • Also called EPR Spectroscopy –Electron Paramagnetic Resonance Spectroscopy • Non-destructive technique • Applications –Oxidation and reduction processes –Reaction kinetics –Examining the active sites of metalloproteins. These include organic free radicals,2 biradicals, Experiment #2B: Electron Spin Resonance Spectroscopy I. Energy: what wavelength or frequency Depends on the ligand field splitting parameter, oct or tet, and on the degree of inter-electron repulsion. Electron spin resonance spectroscopy (ESR) or electron paramagnetic resonance (EPR) is a technique for studying chemical species that have one or more unpaired electrons, such as organic and inorganic free radicals or inorganic complexes possessing a transition metal ion. Its application to organic radicals  under-went rapid expansion in the following three decades, with many monographs being published between 1965 and 1978 [2–15]. This depends on the electron configuration of the metal center. A gerade state is even with Several years ago, electron spin resonance (ESR) spectroscopy celebrated the 50th anniversary of its discovery in 1944. Electron Spin Resonance (ESR) or Electron paramagnetic resonance Spectroscopy (EPR): powerful non-destructive magnetic resonance spectroscopic technique Used to analyse substance with one or more unpaired electrons and radicals Invented by Zavoiskii in 1944 Similar to … Intensity This depends on the "allowedness" of the transitions, which is described by two “selection rules.” There may be additional complexities (due to additional symmetries), e.g., the O2 ground state is 3, g where g stands for gerade (German for even, as opposed to ungerade). Its application to organic radicals  under-went rapid expansion in the following three decades, with many monographs being published between 1965 and 1978 [2–15]. Electronic Spectroscopy • Using light absorption to change charge distribution of electrons about molecule • This is a lot of energy − often can break bonds. Following excitation by microwave absorption, the spin … 3. Electron Paramagnetic Resonance Spectroscopy) • Electrons: spinning, charged particles • ‘stable’ atoms, molecules: all e-are spin-paired. 2S + 1 is the multiplicity. 3 Electron Spin Resonance Spectroscopy Electron Spin Resonance (ESR) spectroscopy, also referred to as Electron Paramagnetic Resonance (EPR) spectroscopy, is a versatile, nondestructive analytical technique based on the absorption of microwave radiation in presence of an applied field by paramagnetic species. 4 E. B M. z. Ng kT (3.7) N = N + + N is the total number of spins in the sample. Several years ago, electron spin resonance (ESR) spectroscopy celebrated the 50th anniversary of its discovery in 1944. 22 eo. 1 Chem 325 Electron Spin Resonance Spectroscopy (a.k.a. Among them, a … 3.