RADICAL CATIONS AND RADICAL-ANIONS OF 3 BRIDGEHEAD AZOPOLYCYCLOALKANES - A FLUID-SOLUTION ESR STUDY

The radical mono-ions of three azoalkanes in which the azo group is connected to the polycyclic alkane moieties at the bridgehead C-atoms, i.e. 1,1'-azonorbornane (1), 1,1'-azotwistane (2), and 1,1'-azobicyclo[3.2.1]octane (3), were studied in fluid solution by ESR spectroscopy. According to the ESR parameters and MO models, the radical cations of 1-3 should be considered as sigma radicals, whereas the corresponding radical anions are pi-radicals. INDO calculations point to a remarkable dependence of the N-14-coupling constants on the geometry at the N-atoms in the radical cations of aliphatic azo compounds.