Y. Kuriyama et al., SOLVENT EFFECTS ON THE OXYGEN ORGANIC-MOLECULE CHARGE-TRANSFER ABSORPTION, Journal of physical chemistry, 98(46), 1994, pp. 11918-11923
Molecular oxygen and 1-methylnaphthalene form a ground-state ''contact
complex'', which can absorb light to populate a charge-transfer (CT)
state. The effect of solvent on this transition has been examined. The
onset of this cooperative absorption Linearly shifts to a longer wave
length with an increase in the parameter (n(2) - 1)/(2n(2) + 1), where
n is the solvent refractive index at optical frequencies. The data do
not correlate with functions in which the static dielectric constant
of the solvent is used. These results are consistent with (a) a ground
-state complex that does not have substantial charge separation, and (
b) a solute-solvent interaction in the Franck-Condon CT state that is
most likely dominated by dipolar coupling terms. Recent studies indica
te that the CT state lifetime is approximately the same as the time re
quired for solvent orientational relaxation. As a consequence, envisio
ning the CT state principally as a Franck-Condon state is likely to be
accurate for many common organic solvents. From this perspective, the
spectroscopic data reported herein should be useful in attempts to es
timate the relative energy of the CT state in a given solvent.