Abstract: Intermolecular interactions between ethylamine or ethylenediamine and H2O or HF were studied theoretically using density functional theory (DFT) at the PBE0/6-31+G(d, p) level. Natural bond orbital (NBO) analyses were employed to elucidate the hydrogen bond characteristics in these complexes. Energy decomposition analysis (EDA) method was applied to complexes of II-1, II-2, III-1, and III-2 at the PBE/TZP level. From this study, four important conclusions were drawn as follows: (1) Both HF and H2O can be stabilized by amines through N…H—F(O), F(O)…H—N or F(O)…H—C hydrogen bonds; (2) Amines have the priority to stabilize HF, because the high electronegativies of florine atom results in the intense N—H…F hydrogen bonds; (3) Stability of the ethylenediamine-associated complexes is higher than that of ethylamine-associated complexes; (4) The most stable complexes, formed by amines with HF or H2O, include F(O)—H…N and F(O)…H—C hydrogen bonds.

Key words: Amine, Intermolecular interaction, PBE0, NBO, EDA