Cationic clusters NICS values

Figure 14.9 clearly shows that the cation cluster has the expected lS lPj IP configuration, whereas the IPj, level is unoccupied. The CMO-NICS values demonstrate that the IS level has an aromatic contribution, but the IP and IP, levels induce an antiaromatic character. In general, the shell orbitals are nonaromatic, and the global aromaticity is due to the orbitals bearing high contributions from the d AOs (Figure 14.9). As these orbitals have a similar shape to that of the P shell orbitals, these are labeled by IP/ and IP/, respectively. They provide some support for an aromatic behavior.

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