The Electronic Structure of 2-Azapentalenes. Photoelectron Spectroscopic Investigations

The He(I) photoelectron spectra of eight 2-azapentalenes, substituted in 1,3-position by electron releasing groups (dimethylamino, ethoxy, and tert-butyl) revealed that the first four ionization energies (6.4–9.3 eV) are due to ionziation from π MO's. This assignment is based on the comparison with the PE data of 1,3-bis(dimethylamino)pentalene (10) and the results of MNDO calculations. The comparison between experiment and calculations suggests that the first two bands are due to ionizations from π MO's mainly localized in the pentalene moiety