Closed shell oxygen-oxygen bonding interaction based on electron density analysis

Electron density analysis within the framework of Quantum Theory of Atoms in Molecules (QTAIM) indicates bond paths between oxygen atoms in open conformers of enol forms of cis-β-diketones. The calculation of atomic energies shows that such a OO interaction in 1,8-naphthalenediol rather than denoting the presence of “non-bonded steric repulsion” can impart as much as 11 kcal/mol (in B3LYP) and 16 kcal/mol (in MP2) of local stabilization to the total energy of the molecule. In addition, QTAIM is also used to characterize these OO interactions. In the studied cases, QTAIM parameters at the BCP of OO bond, including electron density, the Laplacian of the electron density, the energy density and the ellipticity, exhibit the characteristics of closed shell interactions. Delocalization indices between oxygen atoms indicate very little sharing between oxygen atomic basins, which can be interpreted as small OO bond orders.