SEPARATION OF ENVIRONMENTAL FROM CHROMOPHORE-SPECIFIC INFORMATION CONTAINED IN ULTRAVIOLET SOLUTION SPECTRA
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Date
1966
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Ohio State University
Abstract
Ultraviolet spectra of chromophores in solution contain information about the solvent-chromophore interaction as well as information pertinent to the chromophore while low pressure vapor spectra contain only the latter type of information. If it can be assumed that environmental effects on the spacing and relative intensities of the vibrational levels are negligible compared to effects on the electronic transition, then a solution spectrum can be expressed by $\begin{equation}S(\nu) = \int_{-}K^{\infty}_{\infty}(\nu-\nu')V(\nu')d \nu'\end{equation}$ where $S(\nu)$ is the solution spectrum, $V(\nu')$ is the vapor spectrum and $K (\nu-\nu')$ is a distribution function characteristic of the solvent-chromophore interactions. We have obtained spectral data in the $240-300 m\mu$ region for phenol, anisole, benzene, and toluene in the vapor state and in solution in a variety of solvents in the temperature range $0-90^{\circ} C$. $K(\nu-\nu')$ was assumed (on the basis of early work) to be a gaussian and equation (1) was solved for the appropriate parameters using a non-linear least-squares computer program. The fit of the anisole and phenol data to equation (1) was quite good, but the weakly absorbing benzene and toluene yielded poor fits, presumably because of complications such as the appearance of Ham bands. The gaussian parameters and their temperature dependence for all chromophores in water differ strikingly from those obtained for organic solvents and suggest that this analysis may serve as a useful probe for the structure of liquid water. This work was supported by grant GM10831 from the National Institutes of Health, United States Public Health Service.
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Author Institution: Chemistry Department, Purdue University