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'The photochelllical behavior of 4'-amino-, 4'-dimethylarnino-, 4'-diethylamino-, and 4'-di-n-propylamino-substit~~ted trans-2-styrylpyridine were studied. Ultraviolet irradiation of aqueous solutions of the bishydrochlorides and methiodide-hydrochlorides for moderate periods of time produced mixtures of the corresponding cis and trans isomers. Long irradiation times produced the corresponding dimers in all cases except that of trans-4'-di-n-propylamino-2-styrylpyridine. The cis isomers of the free bases and methiodides were isolated from the cis-trans mixtures. The trans-methiodides are not photochemically labile. The spectra of each pair of isomers were determined in water and in 50% methanol-water, with the exception of the 4'-di-n-propylamino derivative, which is not sufficiently water soluble. In addition, the spectra of the corresponding methiodides, hydrochlorides, bishydrochlorides, and methiodide-hydrochlorides were determined. T h e basic strengths of the nitrogens in the cis-trans isomer pairs of the free bases and methiodides have been determined spectroscopically in water and in 50% methanol-water.

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