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Monoaza-analogs of Trimethylenemethane. Isoelectronic Similarities and Differences

Li, J.; Worthington, S. E.; Cramer, C. J.
J. Chem. Soc., Perkin Trans. 2 1998, 1045.

Calculations employing multireference second-order perturbation theory and density functional theory have been carried out for a series of monoaza-analogs of trimethylenemethane (TMM). Trimeethyleneammonium is predicted to have multiplet splittings very similar to TMM. Iminoallyl, also isoelectronic with TMM but with heteroatomic perturbation at a terminal position, is a ground-state triplet like TMM but its corresponding closed-shell singlet state is stabilized relative to the triplet by about 7 kcal/mol. Protonation of iminoallyl generates iminiumdimethylenemethane and the latter system has a singlet ground state in violation of Ovchinnikov's rule. Aqueous medium effects on the singlet and triplet states of iminiumdimethylenemethane are calculated to reduce the singlet-triplet splitting by 1.6 kcal/mol using Solvation Model 5.4/AM1.

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