∆J AP = J true AP -J exp is the difference between the J value calculated using the true LS and HS energies with the AP scheme and the experimentally measured J. For the cases studied here, the magnitude of ∆J AP is similar to, or much smaller than, the magnitude of the experimental J value. The same observation holds for ∆J N P = J true NP -J exp . If one assumes these two parameters are given by the same small value ∆J AP/N P ≈ 100 cm -1 (0.286 kcal/mol), σ is 1 kcal/mol, and S 1 and S 2 are 0.5 (as is the case for most singlet-triplet splittings) we have that