In contrast, the C-centered derivative is the least planar of the three, with both angles of 20°. As expected, the frontier orbitals are in any case strongly located at the conjugated DPP core featuring similar HOMO-LUMO gaps of around 2.51 (±0.02) eV, which agrees with the optical energy band gaps calculated from the absorption spectra in chloroform for the three derivatives. Nevertheless, the optical band gaps are narrower for the H-bonded derivatives in self-assembling promoting solvents, such as chlorobenzene and toluene, ranging from 2-1.66 eV for HDPPBA-C and of 1.98-1.61 eV for HDPPBA-N, depending on the concentration (1-0.03 mg/ml). The morphology of HDPPBA-C, HDPPBA-N and HDPPH was studied using TEM in different solvents (Figure ). Clear differences were found when comparing the H-bonded derivatives to the control molecule. While HDPPBA-C and HDPPBA-N self-assemble into high aspect-ratio structures, HDPPH forms short tape-like crystallites of approximately 2 m in length overlapping with each other in all the solvents tested (Figure -n) except for cyclohexane, where the tape-like structures are narrower and longer (Figure ). In the case of HDPPBA-C, a great disparity of fibers with different width and length were observed in toluene, ethyl acetate and cyclohexane (Figure ). In toluene, the fibers are wavy, intertwined in bundles of rectangular size, and their length can exceed 15 m (Figure ). The structures in chlorobenzene are slightly different, finding elongated fibers as well, but narrower, less twisted than in the other solvents and with sharper edges (Figure ). In chloroform, there are much smaller fibers that are straight and flat. These are the usual structures observed for the other DPP derivatives we have studied so far in chloroform and it seems to be in part due to drying effects (Figure ). The structures found in ethyl acetate and cyclohexane are very similar (Figure