Specifically, ADC(2) estimates show significant uncertainties in π → π * transition energies, with errors of about 0.22 eV for low-lying singlet states and approximately 0.12 eV for lowlying triplet states, resulting in an error in ∆E ST that is comparable to the calculated gap. Acceptable errors are achieved with third-order techniques, such as CC3, which has a mean absolute error of 0.02 eV for π → π * transitions. However, these methods are prohibitively expensive for systems as large as the 3T triangulenes discussed in this work.