Photoisomerization of naphthylquinolylethylenes in neutral and protonated forms

The quantum yield of the trans-cis photoisomerization of 1-(1-naphthyl)-2-(2-quinolyl)ethylene and 1-(2-naphthyl)-2-(2-quinolyl)ethylene is close to the theoretical limit (0.5) for diabatic photoisomerization and does not change on passing from the neutral to the protonated form. The data obtained indicate the absence of the α-effect for the test compounds, which consists in an increase in the trans-cis photoisomerization quantum yield to values of >0.5 upon protonation of some azadiarylethylenes with the nitrogen atom in the α-position to the ethylene group.