In Fig. , we demonstrated that triply excited configurations contribute significantly and are necessary for accurately addressing ST inversion. Ab initio all-electron triple-CI methods are computationally expensive, making them impractical for the 3T triangulenes examined in this study. A perturbative treatment of triple excitations, as in ∆CCSD(T), can reduce computational costs. However, this method only modifies energies, leaving the wavefunction at the singles and doubles level. Results detailed in SI Section S5 demonstrate that ∆CCSD(T)/6-31G calculations produce smaller inverted ST gaps compared to those obtained using second-order ∆CCSD/6-31G. This underscores the crucial role of triple excitations when dealing with ST inversion. Including triple-CIs in systems as large as 3T