Ionization potentials of some azoalkanes by photoelectron spectroscopy

Photoelectron spectra have been obtained for a set of azo compounds consisting of three pairs of cis, trans isomers, seven bridgehead substituted 2,3-diazabicyclo[2.2.2]oct-2-enes (DBO's), and one arylazoalkane. The lowest ionization potentials, which range from 7.83 to 9.21 eV, do not correlate with cis ground state energy or photolability of the DBO derivatives. Vibrational fine structure was observed in three DBO's, allowing verification that the lowest ionization takes place from the antibonding combination of nitrogen lone pairs.