Unexpectedly strong Xe binding by host-guest interaction.

A unique noncovalent interaction between XeO3 and 18-crown-6 has been studied by density functional theory. The calculated results show that there exists an extremely strong binding force between both species, reaching 36.44 kcal mol-1, which is comparable to the strong cation-π interaction. Detailed analyses on relaxed force constants, electrostatic potentials and the independent gradient model, etc. suggest that both quite strong aerogen bondings (XeO) and relatively weak unconventional H-bondings (C-HO) coexist, and the complex is a typical heterodimer with multiple binding sites. Further studies found that XeO3 takes a quick rotary motion relative to 18-crown-6 in the complex due to low rotary barrier. Another two guest molecules, KrO3 and ArO3, are also discussed.