C50Cl10, a planar aromatic fullerene. Computational study of 13C-NMR chemical shift anisotropy patterns and aromatic properties

The isolated-pentagon-rule (IPR) is a prime determinant of fullerene stabilization accounting for the difficult isolation of hollow Cn (n < 60) species. In this connection, the isolation and structural characterization of D5h-C50Cl10 as an IPR-violating fullerene are of interest owing to the study of factors providing further stability. Herein, we use DFT calculations to explore its aromatic behavior. In this connection the C50Cl10 structure is considered as a fullerene displaying a planar-aromatic character provided by the face-to-face disposition of two IPR structural motifs, mediated by ten exobonded sp3-carbons. In addition, the D5h-C50Br10 counterpart appears to be another promising structure as the target for explorative synthesis. Owing to the curvature of its IPR motif, an interesting variation in the 13C-NMR patterns relative to corannulene is described, where the relation between CI and CII signals is useful to evaluate the degree of the curvature of the π-surface. The charge distribution of C50Cl10 reveals a more electron-deficient IPR dome in comparison to C60, envisaging an enhanced chemistry related to bare fullerenes. In addition, the –Cl and –Br exobonded atoms provide effective σ-holes, suggesting such oblate fullerenes as interesting two-dimensional five-fold symmetric synthons useful for the formation of supramolecular species. Hence, an interesting chemistry and supramolecular array derivatives are potential applications to be further explored towards the development of novel nano-devices.