Photochemical behavior of cobalt complexes containing macrocyclic (N4) ligands. Oxidation-reduction chemistry of dihalogen radical anions

Photochemical Behavior of Cobalt ComplexesHowever, if it is assumed that the trap density of the present glass is approximately 10 ~2 M, as seems to be the case for 10 M NaOH glass,7,18 such tunneling must take place over distances of the order of 25 Á in order to explain a major fraction of the decay of es~.Hence, if the estimate of trap density is of the correct order of magnitude, this mechanism is probably not important here.(3) The stabilized electron may move as such.That is, the electron trap with the electron in it may be randomly moving by dielectric relaxation of the medium.This possibility is supported by the sharp rise in the decay rate of es-which is observed in the temperature region where the glass begins to soften.As already noted, it is of course possible that the diffusion of es~occurs by a combination of these mech- anisms.Thus, it is conceivable that diffusion over relatively large distances, say >10 A, occurs primarily by mechanism 3, and that the dominance of this mech- anism increases with temperature, while short-range displacements may take place by tunneling processes, primarily the tunneling from trap to scavenger, which should be relatively more important at low tempera- tures. 2223Such a combination of diffusion mechanisms may be one reason for the time-dependent reaction rate of ea- as shown in Figure 5. Thus, it seems possible that the relatively fast initial decay is associated mainly with tunneling of part of ea-directly into the scavenger molecule, i.e., that part of es" which is trapped suffi- ciently close to scavenger molecules, while the slower decay component is due to diffusion of ea~a s such, i.e., by mechanism 3 above.This hypothesis is indeed supported by the observation that the temperature de- pendence of these two decay components appears to be different.9A further study of the reaction kinetics of es-in glasses may possibly shed some light on the more gen- eral problem of the time dependence of the reaction of eaq-in its early stages (i.e., in very concentrated solutions) which so far seems to be based primarily on theoretical arguments.