Towards in-plane delocalized 4N/7e radical cations and 4N/6e dications - One-/two-electron oxidation of proximate-parallel bis(N,N′-bicyclic)- bishydrazines

Abstract

In the pursuit of novel bishomoconjugated (σ-bishomoaromatic) 4N/7(6)e bonding motifs, (bisseco)pagodane/isopagodane and dodecahedrane-like, caged, proximate-parallel bishydrazines have been designed as suitable host skeletons. The derived radical cations and dications are characterized by calculations as cyclically in-plane delocalized (σ-bishomo-aromatic) species (4N/7(6)e). However, the synthetic approaches based on a pool of half-caged proximate-parallel bisdiazenes/bishydrazines and on strategies in part elaborated in the pagodane area have not led to the target structures. Half-caged, rather flexible bis(N,N′-bicyclic) bishydrazines (9,10) evolved as the structurally closest synthetically 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 (102+) as proximate, cyclically in-plane delocalized species, which, however, relaxed into a more stable, more distant triplet. In an Appendix, selected examples are presented for the synthetic utilization of proximate-parallel bisdiazenes (bishydrazines) in the area of more or less preorganized, semi- to fully caged tetra(hexa)azapolycyclic molecules. © Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.