Effect of aromaticity and ring strain on proton affinity of aziridine and amidine skeletons: a DFT study

Based on density functional theory (DFT) calculations, aziridine derivatives bearing vinylcyclopropane, vinylcycloheptatriene, amidine and guanidine substituents offer suitable skeletons for engineering of organosuperbases. Protonation of the aziridine led to ring opening and complete relief of the internal strain. The positive charge placed in the cyclic π -electron networks resulted in the aromaticity and delocalization of the charge. The calculated proton affinities of the proposed organosuperbases were in the range of 958–1227 kJ mol −1 . Isomerization process for some aziridine derivatives and their protonated forms was also investigated by DFT calculations.