Upon extending these calculations to larger acenes, we observe a discontinuity in the HOMO/LUMO gap computed using LRC-ωPBE, between n = 10 and n = 11 rings. The S 1 excitation energy and ω IE exhibit corresponding discontinuities as shown in Fig. . The discontinuity in ω IE is easily attributed to the abrupt change in the Kohn-Sham gap, yet there is no discontinuity in ω GDD (Fig. ). Nevertheless, there is a discontinuity in the S 1 excitation energy computed using TD-LRC-ω GDD PBE, which is similar to that obtained using TD-LRC-ω IE PBE (Fig. ). This behavior, along with extremely small (sometimes negative) excitation energies starting at n = 11 points to instabilities in the ground-state calculation. These TD-DFT calculations were performed using the Tamm-Dancoff approximation (TDA), 1 as full linear response exhibits imaginary eigenvalue problems for the larger acenes. All of this hints at the appearance of an open-shell biradicaloid singlet ground state for larger acenes. This has been discussed in the literature but lies beyond the scope of ω-tuning.