Selected AB 4 2-/- (A = C, Si, Ge; B = Al, Ga, In) ions: A battle between covalency and aromaticity, and prediction of square planar Si in SiIn 4 2-/-

Anastassia N. Alexandrova, Michael J. Nayhouse, Mioy T. Huynh, Jonathan L. Kuo, Arek V. Melkonian, Gerardo Chavez, Nina M. Hernando, Matthew D. Kowal, Chi Ping Liu

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CAl 4 2-/- (D 4h, 1A 1g) is a cluster ion that has been established to be planar, aromatic, and contain a tetracoordinate planar C atom. Valence isoelectronic substitution of C with Si and Ge in this cluster leads to a radical change of structure toward distorted pentagonal species. We find that this structural change goes together with the cluster acquiring partial covalency of bonding between Si/Ge and Al 4, facilitated by hybridization of the atomic orbitals (AOs). Counter intuitively, for the AAl 4 2-/- (A = C, Si, Ge) clusters, hybridization in the dopant atom is strengthened from C, to Si, and to Ge, even though typically AOs are more likely to hybridize if they are closer in energy (i.e. in earlier elements in the Periodic Table). The trend is explained by the better overlap of the hybrids of the heavier dopants with the orbitals of Al 4. From the thus understood trend, it is inferred that covalency in such clusters can be switched off, by varying the relative sizes of the AOs of the main element and the dopant. Using this mechanism, we then successfully killed covalency in Si, and predicted a new aromatic cluster ion containing a tetracoordinate square planar Si, SiIn 4 2-/-. This journal is

Original languageEnglish (US)
Pages (from-to)14815-14821
Number of pages7
JournalPhysical Chemistry Chemical Physics
Issue number43
StatePublished - Nov 21 2012

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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