Excited Singlet States of "Hairpin" Polyenes

Article abstract of DOI:10.1021/ja00358a003

The synthesis and the UV-visible absorption, polarized fluorescence, and MCD spectra of six U-shaped "hairpin" polyenes (1-6) are reported.Qualitative arguments and results of ?-electron calculations permit the identification of four excited singlet states and their assignment to mixture of singly and doubly excited configurations.The hairpin polyenes represent a link between the all-trans polyenes on the one hand and the annulenes and acenes on the other hand: they possess the topology of the former and a geometry near that of the latter.The understanding of their electronic states offers a unified view of low-energy transitions in polyenes and aromatics, which accounts for their differences in a simple and intuitive manner.