Pulse Radiolysis Study of Solvated Electron Pairing with Alkaline Earth Metals in Tetrahydrofuran. 3. Splitting of p-Like Excited States of Solvated Electron Perturbed by Metal Cations

Abstract

The formation and decay rate constants of the pairs (M II, e - s ) involving solvated electron and alkaline earth metal cations (M II = Sr II, Ca II ) are determined by pulse radiolysis measurements in tetrahydrofuran (THF). The pairs present a strong reducing character and can reduce biphenyl to biphenylide radical anion. The observed absorption spectra of the pairs are broad and intense, similar to that of (Mg II, e - s ). Compared to the absorption spectrum of solvated electron which is a single band located around 2250 nm, these absorption spectra are shifted to the blue and present two bands. The structure of the pairs is investigated by ab initio calculations, and their absorption bands are studied with an asymptotical method. The observation of two absorption bands for the pairs (M II, e s - ) is rationalized as a perturbation of the solvated electron by neighboring solutes which stabilize differently its s and p states and split the p states. The absorption spectra are compared with those obtained for the pair of solvated electron and alkali metal cations.