Theoretical study of strong hydrogen bonds between neutral molecules: The case of amine oxides and phosphine oxides as hydrogen bond acceptors

A theoretical study of the ability of amine oxides and phosphine oxides as hydrogen bond (HB) accepters has been carried out using ammonium oxide, tri methylamine oxide, and phosphine oxide as model systems. The analysis of th e energetic results indicate that only small spatial preferences rue observ ed in the HE interaction. The value of the interaction energies are in seve ral cases within the range of strong PIE (>12 kcal/mol), and in complexes b etween amine oxides and strong acids in the gas phase, a spontaneous proton transfer is obtained. A logarithmic correlation between the electron densi ty at the HE critical points and the HB distance that is able to fit not on ly calculated data but also experimental ones has been obtained. Finally, a linear relationship has been found between the number of HBs and the P-31 NMR shielding in the H3PO ...(HF)(n) series, in good agreement with experim ental reports.