CsF, 16, 17a or 17b via [1] via [1] P(OPh) The structures and properties of the newly synthesized compounds were also computational studied. Optical gaps were calculated by TDDFT using the B3LYP and O3LYP functionals with the 6-311++G (d,p) basis set (see Table ). While the B3LYP calculated gaps resulted, as expected, slightly overestimated, the use of the O3LYP functional, which is similar to the B3LYP but with a smaller percentage of exact HF, predicts smaller energy gaps that are in excellent agreement with the experimental values (within 0.2 eV for all compounds analyzed, see Tables and). Next, we studied the local and global aromaticity/antiaromaticity for the newly synthesized CBD-PCHs by NICS-XY scan calculations, 32 using the s-only method 33 at the GIAO-B3LYP/6-311+G* level of theory (see SI for details). In all compounds, positive NICS values were observed for the fourmembered rings, indicating their antiaromatic character. The paratropicity of the cyclobutadiene rings is more pronounced for compound 22 (NICS = 6 ppm), with single benzene rings fused to the CBD at the PCH termini, and for the angularly-fused systems 12 and 13 (NICS ≈ 5.5 ppm), while the bis(naphthocyclobuta)anthracene ring system 28, previously studied by Xia and coworkers, 8c presents peak NICS values of 3.9 ppm (for 28a). On the other hand, the aromatic character of the different benzenoid rings in each PCH structure is affected by the presence of the antiaromatic cyclobutadienoids and the associated bond localization. To illustrate this feature, Figure shows the NICS-XY scans of the 9-ring polycyclic systems of 12, 13 and 28, showing the terminal benzenoid rings as the less affected (more aromatic character), the rings directly attached to the CBDs as the less aromatic, and a significant difference in the aromatic character of the central ring of the polycyclic systems, being that of the linearly-fused CBD-oligoacene 28 the most aromatic. Finally, to visualize the local diatropic and paratropic ring currents induced by local aromaticity and antiaromaticity, we computed the anisotropy of the induced current density (ACID). 34 As a representative example, Figure shows the ACID plot of 28a; where clockwise current density vectors indicate aromaticity (black arrows) and anti-clockwise ones describe anti-aromaticity (red arrows). As expected, benzene units show clockwise ring currents, while anti-clockwise ring currents are observed in the cyclobutadiene rings. However, taking a closer look at the latter in Figure , one can see the presence of clockwise current density vectors on the peripheral bonds of the four-membered rings, suggesting a global diatropic current loop that rounds the whole system. Figure shows that these clockwise vectors come from the contributions of the σ system. The other studied compounds present similar features, and their ACID plots can be consulted in Figure (SI).