AN EPR AND THEORETICAL INVESTIGATION OF AZOALKANE AND AZOBENZENE RADICAL CATIONS

Results for azoethane, 1,1'-azopropane, 2,2'-azopropane, 1,1'-azoadama ntane, 2,3-diazabicyclo-[2,2,2]oct-2-ene (DBO), 1,4-dimethyl-2,3-diaza bicyclo[2.2.2]oct-2-ene (Me2DBO) and cis and trans-azobenzene radical cations are presented, as formed in solid freon matrices at low temper atures. The azoalkane radical cations are all formed in sigma-states, corresponding to ionisation of the a(g) orbital (out-of-phase lone-pai r combination), while for the trans-azobenzene radical cation the assi gnment to the pi-state cannot be definitely excluded, although experim ental evidence would appear to suggest the sigma-state: the cis-azoben zene radical cation isomerises to the trans-isomer. Semi-empirical cal culations were also performed on selected examples of the above specie s, the conclusions from which are discussed.