Interaction between naphthyl-indolyl-ethenes and aliphatic amines: Effects on fluorescence and trans→ cis photoisomerization

The fluorescence of two trans naphthyl-indolyl-ethenes in solvents of different polarity and H-bonding ability is quenched by aliphatic amines. The H-bonded complexes formed both in the ground- and in the first excited singlet state are responsible for the quenching in non-hydroxylated media. In methanol the interaction, which occurs only in the excited state, leads to the deprotonation of the indolyl-moiety. The consequences of the quenching on the trans→ cis photoisomerization yield are reported.