Evolution of the Optical Gap in the Acene Series: Undecacene

Undecacene, the largest member of the acene family, was photogenerated in a polymer matrix under cryogenic conditions from a precursor with two α-diketone bridges. The electronic absorption of undecacene extends into the NIR region, but the spectrum is dominated by two strong absorptions in the UV/Vis range. The HOMO-LUMO transition is continuously shifted to lower energies as the number of rings of the acene increases (E vs. 1/N, N=number of rings), which is in line with the strong electron correlation calculated by DFT/MRCI.