Fig. 2: Design, synthesis, simulation, and spectroscopy of the nonacene variant.

A The design of our nonacene-like molecule, where the extended all-carbon nonacene core (black) results in a near-infrared absorbance, the fused peripheral aromatic rings (gray) enhance stability, the nitrogen heteroatoms (blue) introduce stimuli responsiveness, and the pendant alkyl-functionalized phenyl rings (green) improve solubility. B The synthetic route for the preparation of nonacene-like molecule 4, where the two key steps involve a Lewis acid-mediated aza-Diels-Alder reaction and a base-mediated cyclodehydrohalogenation reaction. C The HOMO (left) and LUMO (right) calculated for the unprotonated tetrabenzononacene TBN, 4. D The HOMO (left) and LUMO (right) calculated for PTBN, 4 + 2H⁺. E The theoretical UV–Vis–NIR absorption spectra calculated for TBN, 4 (blue dashed line) and PTBN, 4 + 2H⁺ (brown dashed line). The chemical structures of TBN and PTBN are inset. F The experimental UV–Vis–NIR absorption spectra measured for TBN, 4 (blue solid line) and PTBN, 4 + 2H⁺ (brown solid line). The pictures of the TBN and PTBN solutions in chloroform are inset. Note that the theoretical and experimental absorption spectra were normalized to unity for clarity.