Solutions of potassium in amines and ethers.

Solutions of potassium in ethylamine, tetrahydrofuran, dlglyme and a series of solvent mixtures have been studied by electron spin resonance and optical spectroscopy. Optical spectra consisted of a single maximum at 14,000 cm-1 for solutions prepared in pyrex vessels, at 11,000 cm-1 for solutions prepared in quartz vessels. Electron spin resonance spectra, in pure solvents and solvent mixtures, consisted of an equally-spaced quartet, attributed to the "monomer", Ksolv.' and a central singlet, attributed to the solvated electron, e-solv. For some solvent systems, a marked dependence of hyperfine quartet line-widths upon nuclear magnetic quantum number, mI, was observed. The dependence of the optical spectrum upon vessel material and the magnitude of electron spin resonance line-widths have been discussed in terms of the steady-state composition of the solutions. On the basis of results obtained in pure solvents and solvent mixtures, it is proposed that the monomer, in amine and ether solvents, is best represented as a solvent-separated ion-pair whose structure is modified at higher temperatures.