Density functional theory calculations demonstrate that the global minimum of the Cu7Sc potential energy surface is a seven-membered ring of copper atoms with scandium in its center, yielding a planar D7h, structure. Nucleus-independent chemical shifts [NICS(1)zz and NICS(2)zz] show that this cluster has aromatic character, which is consistent with the number of 4s electrons of copper and scandium plus the 3d electrons of scandium satisfying Hückel's rule. According to a canonical MO decomposition of NICS(1)zz and NICS(2)zz, the MOs consisting of the 4s atomic orbi tals are mainly responsible for the aromatic behavior of the cluster. The electron localizability indicator (ELI-D) and its canonical MO decomposition (partial ELI-D) suggest that a localized basin is formed in Cu7Sc by the copper atoms whereas the two circular localized domains are situated below and above the ring. The planar Cu 7Sc cluster can thus be considered as a σ-aromatic species. These findings agree with the phenomenological shell model.
- Cluster compounds
- Electron localizability indicator
- Electronic structure
- Seven-membered ring
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry