To further validate the DFT results, single-point CCSD/def2-SVP computations were performed on the ω-B97XD/def2-TZVP-optimized geometries, as ω-B97XD has been demonstrated to be reliable for modeling strained molecules. Vertical singlet-triplet gaps were calculated at both singlet and triplet geometries. At the singlet geometries, all olefins exhibited high-energy triplet states. However, at the triplet geometries, several olefins with low singlettriplet gaps were found to have more stable triplet states. Nonetheless, for compounds 1aF, 2a, and 3a, the singlet state was consistently more stable at the CCSD level, regardless of the geometry used, Table .