Conformations privilegiees de dithieno[c,e]dihydro azepines,oxepinnes et thiepinnes: Etude par spectroscopie d'absorption electronique

The comparative study of the electronic absorption spectra (uv) of dithienoc,e]dihydro azepins, oxepins and thiepins and of the corresponding bithiophens shows that “twist” forms are privileged for the cyclic compounds. This conclusion is confirmed by a theoretical analysis (CNDO/S) and by a study of sterically hindered compounds.