Exploring lithium bonding interactions between noble-gas hydrides HXeY and LiX molecules (Y = H, CN, NC and X = H, CN, NC, OH, NH2, CH3): A theoretical study

Abstract

Quantum chemical calculations were performed to analyze the existence of intermolecular lithium bond interactions in HXeY (Y=H, CN, NC) complexes with LiX, where X=H, CN, NC, OH, NH2, and CH3. The geometry optimizations between HXeY and LiX were performed with the MP2 and M06–2X methods using aug-cc-pVTZ basis set. One can see that, the H–Xe stretching mode of HXeY molecules shifts upon complexation higher in energy, i.e. exhibits a blue shift. The blue shifts of the H−Xe stretching mode are attributed to the enhancement of the (HXe)+Y− ion-pair character upon complexation. The global minimum for the HXeY⋯LiX complexes was found on the potential energy surface for the structure I, i.e. the structure of a linear Xe–Y⋯Li interaction. It is seen that the lithium bond interaction energies span over a range from −9.5 to −31kcal/mol at the CCSD(T)/aug-cc-pVTZ level of theory. For the all HXeY⋯LiX complexes studied, the dominant attractive contributions mostly originate from the electrostatic energy Eelst. According to quantum theory of atoms in molecules (QTAIM), all lithium bond interactions studied here display the characters of closed-shell and noncovalent interactions. The redistribution of the electron density at H–Xe critical points upon complex formation is also noticeable, which is in accord with the computed H−Xe frequency shifts in HXeY⋯LiX complexes.