Stabilization of nitrogen-containing three-membered rings by proton and lithium ion association in the gas phase

Ab initio calculations have been performed for three-membered nitrogen-containing rings, including all saturated and unsaturated compounds and their protonated and lithiated species. Geometry optimizations were carried out at the HF/6-31G * level and, for some suitable examples, at the MP2/6-3 1G * level. Protonation energies and Li + binding energies were evaluated at the MP4/6-31+G(d,p) level including ZPVEcorrections. We have found that the intrinsic basicities of saturated nitrogen-containing three-membered rings decrease as the number of basic centers increases. However, the same trend is not observed in the series of unsaturated analogues, where triazirine is predicted to be much more basic than diazirine