| Summary: | Bonding and aromaticity in the bowl-shaped <i>C</i><sub>5v</sub> and planar <i>D</i><sub>5h</sub> geometries of corannulene and the planar <i>D</i><sub>6h</sub> geometry of coronene are investigated using 3D isosurfaces and 2D contour plots of the isotropic magnetic shielding <i>σ</i><sub>iso</sub>(<b>r</b>) and, for planar geometries, of the out-of-plane component of the shielding tensor <i>σ<sub>zz</sub></i>(<b>r</b>). Corannulene and coronene both feature conjoined shielded “doughnuts” around a peripheral six-membered carbon ring, suggesting strong bonding interactions and aromatic stability; a deshielded region inside the hub ring of corannulene indicates that this ring is antiaromatic, more so in planar corannulene. The switch from the planar to the bowl-shaped geometry of corannulene is shown to enhance both bonding and the local aromaticities of the five- and six-membered rings; these factors, in addition to ring strain reduction, favour the bowl-shaped geometry. The most and least shielded bonds in both corannulene and coronene turn out to be the spoke and hub bonds, respectively. The higher π electron activity over spoke bonds in planar corannulene and coronene is supported by <i>σ<sub>zz</sub></i>(<b>r</b>) contour plots in planes 1 Å above the respective molecular planes; these findings about spoke bonds are somewhat unexpected, given that ring current studies indicate next to no currents over spoke bonds.
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