Structuring of molecules of water and hydroxonium ion in the cucurbit[7]uril portal. Theoretical study of structure, electronic properties and energy

Abstract

Detailed DFT calculations of supramolecular complexes of water and hydroxonium ion molecules with cucurbit[7]uril (CB[7]) were performed. The hybrid Becke-Lee-Young-Parr method (B3LYP) on basis 6-31G* was used. The DFT calculations were supplemented with calculations taking into account the van der Waals interactions (DFT-D3).The structure of the “guest” – “ host” complexes with the introduction from 1 to 10 water molecules has been established. The structure and energy of protonated forms of these complexes are studied. It is shown that the maximum number of water molecules in the CB[7] portal can reach 8 molecules, and during protonation the number of water molecules can increase to 11. The change in enthalpy and Gibbs free energy during the sequential attachment of water molecules to CB[7] and its protonated form is studied. The enthalpy and Gibbs free energy during the sequential attachment of water molecules to CB[7] have two minima when the number of water molecules equals 4 and 8. For protonated CB[7], the enthalpy has a minimum at the number of water molecules n = 7 and 10.