A HIGH-LEVEL AB-INITIO AND DENSITY-FUNCTIONAL INVESTIGATION OF CYCLOPROPENYL ANION AND ITS MONOSUBSTITUTED, DISUBSTITUTED, AND TRISUBSTITUTED DERIVATIVES

High-level ab initio and density functional theory calculations were c arried out on cyclopropenyl anion (1) and related species. The parent c-C3H3- ion is predicted to be unstable with respect to electron loss whereas its cyano-substituted derivatives are attractive synthetic tar gets. MCSCF structures for singlet and triplet cyclopropenyl anion are reported and contrasted to the results obtained from more modest comp utations. Energetic quantities for 1 were computed including its proto n affinity; destabilization energy, singlet-triplet gap, electron bind ing energy, and ring-opening isomerization energy. The allylic C-H bon d strength for cyclopropene also is given. Mono-, di-, and tricyanocyc lopropenyl anions were investigated too, and their conjugate acids hav e lower pK(a)'s than cyclopropene by up to 70.4 kcal/mol or 52 pK(a) u nits.