Pulse radiolysis studies. XXI. Optical absorption spectrum of the solvated electron in ethers and in binary solutions of these ethers

Abstract

The optical absorption spectrum of the solvated electron has been determined by pulse radiolysis in the pure liquid ethers: tetrahydrofuran, methyltetrahydrofuran, diethyl ether, dimethoxyethane, diglyme, triglyme, and tetraglyme. The absorption maxima are at 4720, 4650, 4350, 4880, 5220, 5440, and 5580 cm−1, respectively. The half-widths of the bands have also been measured. The oscillator strength, determined for the first four ethers is approximately unity. The absorption bands have been determined in binary solutions with ethylenediamine and for tetrahydrofuran-water over the entire concentration range. Calculations using a recent form of a cavity-continuum model have been compared with the experimental results. The model shows agreement with the experimental values for the transition energy for an effective cavity radius of about 4 Å and a coordination number of 6 or 8. Kinetics for the attachment of solvated electrons to pyrene and for the reaction of the solvated electron with the solvent counterion have been investigated in several ethers and absolute rate constants determined.

Flash photolysis of alkali metal anions in tetrahydrofuran and dimethoxyethane

“…The reported optical spectra (13)(14)(15)(16) show good agreement in the position of the band maxima but often significant differences in band width and intensity, particularly on the high energy side of the spectrum. Utilizing the most reliable data (free of Na' contamination) (15, 16) in comparison with our own initial spectra, the overall band envelope for each M -species was established by a Gaussian-Lorenztian (G-L) shape function analogous to the method used for e,- (17)(18)(19). Since sodium is insoluble in T H F (and DME) our Naspectra were obtained either by the addition of dicyclohexano-18-crown-6 (16) or from Na/Cs solutions in which the final equilibrium spectrum is due to Na-.…”

“…Taking E,,-, E(,+, ,%-,, and E(,-,+,,,-) = 8.2 f 0.3, 2.9 +_ 0.2, and 2.5 f 0.2 x lo4 L mol-' cm-', respectively (10,24), the absolute values for E, -and E,-~-can be determined experimentally. Furthermore, the oscillator strength, f, for a Gaussian-Lorenztian absorption band is given by [3] (18).…”

Degradation of an Ethylene Carbonate/Diethyl Carbonate Mixture by Using Ionizing Radiation

“…Our observation is in agreement with the factt hat the absorption band of the solvated electron in ah omogeneousm ixture usually ranges between the two maximao ft he absorption band of each solvent, as already observed for aT HF/H 2 Om ixture, which also contains aw eakly polar and as trongly polar compound. [22,23] In this case, and for am olar fraction of THF lower than 0.49, the presence of THF only slightly changed the spectrum of the solvated electron, which was similar to the spectrum of the solvated electron in water,b ut at ah igher temperature. [23] In our case, the transients pectrum we measured (for am olar fraction of DEC equal to 0.43) is similart ot hat obtained in EC, butr edshifted ( Figure 2).…”

Ionic aggregation of the solvated electron with lithium cation in tetrahydrofuran solution

“…To account for these observations, we propose the reaction sequence: + (Li ,es) + 02 -74 Li 02 (9) Li + Li *2 (Li )202 The rate constant for the first-order decay of biphenylide ion, obsurved at 630 nm, was found to be (1.4 f 0.3) x 105 .sec-1. This is an over.all rate constant for the decay which cannot, with the present data, be identified with a specific reaction in the sequence (9) where the concentrations of the two transient species in equation (12) are determined at t=0 after the pulse. 0& represents the biphenylide ion in either state of aggregation with Li .…”