Molecule S-T gap q(C1) q(Cb) If the substituent on the carbocation is a weakly electron donating one, and more charge is accumulated on the carbocation, the singlet-triplet energy gap decreases notably. This shows that strong localized positive charge prefers an even distribution of electrons on the branching carbon and the one-carbon bridges. Interestingly, the presence of methyl groups on the ortho position of phenyl substituents does not increase the singlet-triplet gap. Looking at the atomic charges shows that although cations are slightly more delocalized via electron donating effect of the ortho-methyl, the proximity of methyl to the anionic carbon puts electrostatic pressure on the anion and lowers the singlet-triplet gaps. This is reflected in the energy levels of HOMOs. For example the HOMO of 1bF is 0.05 eV higher in energy than that of 1aF that lacks the ortho-methyl group on the phenyl substituent. In structure 1, the electronic effect of fluorine atoms, two bonds away from the anionic center, still influence the charges and hence the singlet-triplet energy gaps. Therefore, with norbornane's σ-framework, 1, 1aF, with eight fluorine substituents and a para-dimethyl aminophenyl substituent on the cationic carbon has the largest singlet-triplet gap and is most likely to be synthetically achievable in a polar solvent medium.