Figure 9.
Ground- and excited-state geometries of the peridinin model compounds in methanol (see text). Arrows indicate bond-order reversal, and bonds that are strengthened (shortened) in the ICT state are marked with the arrows. The total length of the chromophore is represented by RAB, and increases by ∼0.01 Å upon population of the ICT state relative to the Franck-Condon (ground-state) geometry. Both ground- and excited-state geometries are planar (except for hydrogen atoms), and dihedral distortions along the polyene chain were tested and found to be energetically unfavorable.