An ab initio study of the structures and stabilities of the complexes of the bases N 2 O, CO 2 , and CO with the acids FH, H + , and Li +

The geometries of the complexes of the bases N 2 O, CO 2 , and CO with the acids FH, H + , and Li + have been optimized at second‐order Møller–Plesset perturbation theory with the 6–31+G(d, p) basis set. Interaction energies were computed at QCISD(T)/6–31+G(2d,2p). The complexes FH … ONN and FH … NNO have bent and linear geometries, respectively, in agreement with experimental data. The complex FH … OCO also has a bent equilibrium structure, although at room temperature a vibrationally averaged linear structure is observed. FH … CO and FH … OC have linear structures. N‐and O‐protonated N 2 O and protonated CO 2 have bent structures, whereas C‐ and O‐protonated CO are linear. The Li + complexes of all of these bases are also linear. Association of H + , Li + , and FH with N 2 O occurs preferentially at O, although interaction energies for association at N are similar. In contrast, association of these acids with CO is significantly stronger at C than at O. The most stable hydrogen bonded complexes FH … ONN, FH … OCO, and FH … CO have similar stabilization enthalpies at 298 K of −2.2–2.5 kcal/mol. The order of proton affinities of these bases is CO > N 2 O > CO 2 , while the order of lithium ion affinities is reversed.