Remarkably, the cyclopentene-fused derivative 26c resulted soluble enough to successfully obtain its 1 H NMR spectrum in 1,1,2,2-tetrachloroethane-d2. With regard to the other newly synthesized CBDoligoacenes, although the lack of solubility precluded their characterization by NMR, their identity was confirmed by high resolution mass spectrometry and analysis of their UV-vis spectra. In particular, compounds such as 26a-c or 28a-b displayed similar spectra that those reported for previously described alkynyl or aryl-substituted analogues. Selected experimental data provided by the UV-vis and fluorescence spectra of the newly synthesized cyclobutadiene-containing PCHs are summarized in Table , together with the results of the computational estimation of the energy gaps (see SI for full details).