[2.2.2.2]Pagodane:  Synthesis and Oxidation of Nonclassical Valence-Isomeric 4C/3e and σ-Bishomoaromatic 4C/2e Ions

Hydrocarbon σ‐radical cations

“…The most stable form is E (by 10.3 kcal/mol than T , B3LYP/6–31G(d)); however, it was pointed out that ‘the minima could not be checked by a frequency analysis because of the size of the systems’. The ESR signals were attributed to a D 2h ‐structure of the [2.2.2.2]pagodane radical cation 127…”

Towards In‐Plane Delocalized 4N/7e Radical Cations and 4N/6e Dications – One‐/Two‐Electron Oxidation of Proximate‐Parallel Bis(N,N'‐bicyclic)‐bishydrazines

“…The unique, perfectly in-plane delocalized, four-center three-electron radical cations and σ-bishomoaromatic twoelectron dications A [4C/3(2)e] [1] owe their existence and, in part, impressive kinetic stability to their very special molecular architecture, polycyclic pagodane-/dodecahedranetype cages. [2][3][4][5] Thus, when the project centered on the inplane bishomoconjugated four-center five(six)-electron radical anions/dianions B [4N/5(6)e] [6] was extended to the 4N/ 7(6)e radical cations/dications C and D, [7] fully cagedtetraazapolycycles such as 1, 2, and 3 emerged as first choice host skeletons: [8] The C=C double bonds of the carbocyclic models 4-6 [1][2][3][4][5] are replaced by hydrazine units, which are held strictly parallel at relatively short transannular dis-accessible model compounds. Whilst CV (PE, ESR)measurements were not suggestive of significant through-space interaction in the respective radical cations and dications, DFT calculations (B3LYP/6-31G*) identified a singlet dication (10 2+ ) as proximate, cyclically in-plane delocalized species, which, however, relaxed into a more stable, more distant triplet.…”

CIDNP as a tool for rapid rearrangements: New insights into cyclobutanoid 4‐center/3‐electron radical cations

“…Thus, for the radical cations of 1 , 4 and 6 , where 1 H hfcs were already established and have been assigned in previous studies, only those attributed to the β positions (see formulas 1 , 2 , 3 , 4 , 5 , 6 above) are given. The only exception is 5 where, there is essentially no spin transfer onto the β protons neither in the “tight” nor in the “extended” isomer; however, the distinction for 5 can be made based on hfc values of the γ protons. Here, EPR revealed eight equivalent H γ hfcs of 0.58 mT, well reproduced by CIDNP (0.63 mT) and the calculated value of 0.63 mT for a “tight” isomer.…”

“…The discovery of the highly persistent (2 days at 20 °C) 4‐center‐3‐electron (4c/3e) radical cation observed upon (electro)chemical oxidation of [1.1.1.1]pagodane ( 1 ) has induced numerous studies of related cage skeletons . Significant changes with respect to stability, persistence and behavior of the corresponding radical cations could be established.…”