ANOMALOUS SOLUTION SPECTRA OF DIPYRRYL METHINE SALTS
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Date
1979
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Ohio State University
Abstract
We have found the hydrobromide and hydrochloride salts of substituted dipyrryl methines to behave non-ideally in some solvents. In acetonitrile, for example, their spectra sharpened as the concentration increased with a concurrent increase in the extinctin coefficient at the peak wavelength. Maximum absorption shifted towards longer wavelength as the concentration increased. The largest changes were observed for the tetramethyl hydrobromide derivitive, where an eight-fold increase in the extinction coefficient accompanied a twenty-fold increase in concentration. These results are similar to those reported for cyanine $dyes^{1}$. In this preliminary report we shall stress the observations and present the variation in extinction coefficients and peak wavelength in several solvents, ranging in polarity from benzene to dimethyl sulfoxide. Qualitative and semi-quantitative results will be given. We will discuss some of the implications of this work to the photochemical studies of these compounds, which can serve as models for the porphyrins. Some comments will also be made on the stability of these solutions with reference to their spectra.
Description
$^{1}$ W. West in Neblette’s Handbook of Photography and Reprography, Seventh Edition (J. M. Sturge Edition, Van Nostrand Reinhold Company, 1977) Chapter 4, 87-9.
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