| Electrides are a class of compounds in which an alkali metal cation is encapsulated by a complexant, usually a crown ether or a cryptand, and the unpaired electron occupies the anionic site in a well defined structural arrangement. The nature of the sites in which these electrons are located is important to their physical and magnetic properties. Electron paramagnetic resonance (scEPR) is a good tool for studying these trapping sites. However, since the electrons are so close together, rapid electron exchange often occurs to yield a single exchange narrowed scEPR signal. A closely related compound to electrides, alkalides, differs in that an alkali metal now acts as the anion. Trapped electrons are much more isolated than the electrons in electrides, thus they are present in small concentrations which avoids the problems of exchange-narrowing of the scEPR spectrum. Often there are weak, superhyperfine couplings between the paramagnetic center and the nearby magnetically-coupled nuclei that are unresolved in the cw- scEPR spectrum due to inhomogeneous broadening of the resonance lineshape, which can mask the hyperfine structure in the scEPR spectrum. Spin-echo experiments can reverse this observation.;Cavity-trapped electrons in the electride Li... |
