Synthesis, electronic spectra, and photoisomerization of naphthyl-pyridylethylenes

Abstract

The synthesis and spectral characterization of the isomeric naphthylpyridylethylenes (NPEs) are reported. It can be deduced from the u.v. spectra that the 2-pyridyl compounds display a smaller deviation from planarity than the other isomers. trans-NPEs have higher photoreactivity and give a lower yield of radiative deactivation than the parent hydrocarbons. The differences are particularly remarkable for the 2- and 4-pyridyl isomers. These differences are tentatively explained on the basis of variable involvement of n,π* states in the deactivation pathways of excited NPEs.