Figure 5.

(a) Schematic illustration of through-space orbital interactions within the HOMO and the LUMO in o-1, o-1a, and o-1b at positions 13 and 14. (b) Thermal equilibrium between the singlet ground state and the triplet excited state of o-1 (R = H) and o-1b (R = Me). Distances between the fjord carbon atoms (dashed lines) obtained from optimized geometries (BS/U-B3LYP/6-31G(d)) are shown. (c) Relaxed potential energy surface (PES) scans of o-1 (top) and o-1b (bottom) in their singlet ground (blue) and triplet excited (red) states, performed to estimate the relative contributions of the geometric (“twist”) and electronic (“Me”) effects of the methyl substituents on the ST gap.