DFT calculations. Ground-state geometries of isolated molecules were optimized at the DFT level using the ωB97X-D functional and def2TZVPP basis set. IR and Raman frequencies were calculated at the same level of theory. For the quinoidal form, the original molecule was used, however for the aromatic form, the cyano-groups were cleaved. This allowed for fully relaxed structures to be used in both simulations while capturing the correct bond length alternation observed in each conjugated core. The UV-Vis absorption spectra were likewise calculated at the same level of theory, using the 10 lowest singlet and triplet states in the TD-DFT calculation. All calculations were performed using Gaussian16 Rev. B. Side chains were removed for computational efficiency. In this case, the quinoidal geometry optimization was allowed to relax fully, while for the aromatic geometry the carbon atoms along the backbone were fixed to enforce the proper aromatic single-double bond alternation pattern (i.e., that opposite the quinoidal bonding pattern) and the result of the structure was allowed to relax.