When you introduce a substituent to an aromatic system in organic chemistry you are mostly interested in the effect on the aromatic. The reason for this is that substituents are often attached in specific positions to steer the outcome of a following reaction.
In this study we examined the interplay between indole and a methoxy substituent. Depending on its position at the ring system, the methoxy group alters the energetic position of the excited states of indole by about 2500 cm-1. Interestingly, there is also a position-dependent influence of indole on the substituent. We observe that the relative energies of the conformers and their barriers for interconversion depend strongly on where the methoxy group is located at the chromophore. With this we can explain why for 4- and 5-methoxyindole only one conformation is observed in jet-experiments, while both conformers are present for 6-methoxyindole. More information can be found here.