Each porphyrin unit in a c-PN nanobelt contributes 10 electrons to the Hückel count, so we expect even-numbered belts to sustain a paratropic ring current associated with anti-aromaticity (positive NICS inside the ring; red in Figure ) and the odd-numbered ones to display a diatropic current consistent with aromaticity (negative NICS inside the ring; blue in Figure ). Using OX-B3LYP we find that this is indeed the case, and predict that c-P22 (circumference of 18.6 nm) as the largest nanobelt to show a ring-current-induced shift at the center of the ring larger than 1 ppm (NICS(0)zz of ±3 ppm corresponds to an isotropic shift of ±1 ppm, which is roughly the accuracy of DFT ; Figure ). We also note that the best performing DFA with a constant proportion of EE (BLYP25) provides a very similar estimate (see Figure ).