Spectroscopic studies of ions in condensed media.

In Part I the electron spin resonance spectra at X- and in some instances Q-band frequencies of liquid and frozen solutions of the tetracyanoethylene anion, the 1,1-diphenyl-2-picrylhydrazyl radical, and the species formed by the photolysis of ethereal solutions of substituted nitrobenzenes are reported. Theoretical implications of the extra structural information so obtained are discussed. Linewidth variations in the electron spin resonance spectra of these radicals are explained using a new and simple pictorial model for asymmetric linewidth variation. Details of the electron spin resonance spectrum of the p-dinitrobenzene anion in various solvent mixtures are discussed and it is shown that the linewidth alternation occurring is consistent with the formation of ion pairs in solvents having low polarity. A simple model for this type of linewidth effect is also given. In Part II the ultraviolet absorption spectra of solvated halide ions are reviewed and the various consequences of the proposed models discussed. The ultraviolet spectrum of solutions of the hydrosulphide anion is reported and the existence of the free sulphide anion in aqueous solution is confirmed. It is concluded that both anions absorb light by the charge transfer to solvent mechanism.