In molecular rings, a coherently delocalized electronic wavefunction causes the appearance of a global ring current under an externally applied magnetic field. This ring current produces magnetic shielding patterns that may be described using a particle-on-a-ring model. Hückel's rule states that systems with circuits of 4n+2 π-electrons (where n is an integer) sustain a diatropic current associated with aromaticity, while 4n π-systems sustain an anti-aromatic paratropic current. As ring size increases, ring currents tend to become weaker due to symmetry-breaking and structural flexibility, which interrupt electronic delocalization. NMR spectroscopy has revealed substantial global ring currents in butadiyne-(Figure ) and ethyne-linked porphyrin nanorings with circuits of up to 162 π-electrons (n = 40). These singly-linked nanorings only show global ring currents in their charged states, where Coulombic repulsion promotes a more uniform charge distribution. In contrast, here we show that large triply-linked c-PN nanobelts (Figure ,f) are expected to exhibit global ring currents even in the neutral state, due to the stronger coupling between the porphyrin subunits. This work is part of a wider experimental and computational project exploring the frontier between molecular rings and topdown fabricated non-molecular nanorings that also exhibit persistent ring currents. While the experimental identification of global ring currents using NMR spectroscopy is often unambiguous, theoretical modelling is more challenging, particularly when using density functional theory (DFT) and nucleus-independent chemical shift (NICS) calculations. 17 This is not surprising, as the extent of symmetry breaking and electronic delocalization in conjugated systems is sensitive to the choice of method, 18-20 as first noted by Longuet-Higgins and Salem in 1959. This is especially apparent in the case of hybrid DFT, which builds on pure Kohn-Sham DFT by including a proportion of exact exchange (EE) in the density functional. Adding EE reduces the self-interaction error, which is one of the main weaknesses of pure DFT, but adding too much EE causes too much localization by underestimating dynamic correlation, which pure DFT generally handles very well. The difficulty of striking the right balance between localization (too much EE) and delocalization (too little EE) can be illustrated by the case of the butadiyne-linked 6-porphyrin nanoring in its 6+ oxidation state (c-P6-b6 6+ , Figure ). For this system, B3LYP 23 (20% EE) overestimates the experimentally measured global ring current, M06-2X 24 (54%) underestimates it, 25 while BLYP35 (35%) reproduces the experimental results. All of these DFAs have a constant proportion of EE (red, light blue, and purple in Figure ), which results in an incorrect description of the Coulomb interaction in the longrange limit and a poor description of charge transfer. Rangeseparated DFAs (e.g. LC-ωPBE, 27 gray in Figure ), in which the proportion of EE is dependent on the interelectronic distance r12, remedy this issue, 28 but need three tunable parameters: EE0 and EE∞, which control the proportion of EE at the short-(r12 = 0) and long-range (r12 = ∞) limits, and ω (usually given in units of reciprocal Bohr radius, a0 -1 , with a0 ≈ 0.52 Å) , which controls the transition from EE0 to EE∞ (Figure ). In the case of the above-mentioned c-P6-b6 6+ , the range separated functionals CAM-B3LYP 29 (green in Figure ) and a modified flavor of LC-ωPBE (ω = 0.1 a0 -1 ) were both used to model its ring current, with good results. At this point, the skeptical reader may rightly ask: If choosing a suitable DFA for modelling ring currents in nanorings for which experimental data are available is so difficult, what hope do we have of accurately predicting ring currents in c-PN nanobelts, which have yet to be synthesized? To answer this question, we recall that the equilibrium geometry of a conjugated system will be the result of a balance between the (distortive) π-and the (restorative) σ-electrons. This balance will be highly dependent on the proportion of EE in hybrid DFT. Therefore, if we build a series of DFAs with different proportions of EE, the DFA providing the most accurate equilibrium geometry is likely to have the correct balance, and can be expected to give a reliable description of the electronic structure and ring current. We have recently shown that this hypothesis holds well in case of [18]annulene, an archetypal conjugated system. Using coupled clusters energies as reference (which are free from self-interaction error, but also include dynamic correlation), we identified BLYP45 (45% EE) as the optimal DFA and found that it reproduces chemical shifts in both [18]annulene and its anions with a <1 ppm accuracy over a >30 ppm range. Similar approaches have been used successfully to identify appropriate DFAs for modelling interconversions between Hückel and Möbius topologies, 34 fullerene-based memristors, 35 and pericyclic reactions. Here, we adopted the following general strategy (details in SI Section A):