Ionization energies and proton affinities of a series of medium-ring bicyclic amines and diamines with bridgehead nitrogens are reported. The photoelectron spectrum of out-bH-1 -azabicyclo[4.4.4]tetradecane (3) is similar to n-Bu3N and unlike that of l-azabicyclo[3.3.3]undecane (manxine) (2), suggesting that the nitrogen in 3 is pyramidal. However the proton affinity of 3 is 20 kcal mol'1 lower than that of n-Bu3N; it is proposed that 3 is inwardly pyramidalized and that (outside) protonation causes a large increase in strain energy in agreement with force-field calculations. The photoelectron spectra of diamines 6-9 show two bands due to lone-pair ionizations, the first ionization energy being exceptionally low (<7 eV). The interplay of flattening at nitrogen, and of through-space and through-bond coupling in these diamines, is discussed with the aid of force-field calculations. 1,]tetradecane ( 9) is a weaker base than l, 5-diazabicyclo[3.3.3]undecane, but it is stronger than 3. Z)(N+-H) bond dissociation energies give evidence of substantial stabilization (>11 kcal mol'1) of 6+• and 9+• by 3-electron a bonding.

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Die Titelverbindung (I) kann Protonen sowohl außen anlagern (Kationen (II) und (III)) als auch einschließen (Kation (IV)).