Figure 9.

Schematic illustration of the PES of 9,10‐bis(N,N‐dimethylamino)anthracene obtained from DFT/TD‐DFT calculations at the B3LYP/6‐31+G(d) level of theory. The ground state adopts two stable conformations (S0MIN) that are interconverted through the inversion of its NR₃ tetrahedra. After photoexcitation, each Franck–Condon (FC) state relaxes through planarization of one NR₃, leading to the conformation shown as S1MIN1. This “umbrella motion” occurs also at the other NR₃ tetrahedron under concomitant tilting of these planar trigonal planes, which gives another stable conformation (S1MIN2). These structural relaxations decrease the S₀–S₁ transition energy to the extent comparable with the experimental Stokes shifts. Any MECI was not sampled in this calculation and is hence not shown here.