HE-I PHOTOELECTRON-SPECTRA AND PI-ELECTRONIC STRUCTURE OF 1,3,2,4-BENZODITHIADIAZINE AND 5,6,7,8-TETRAFLUORO-1,3,2,4-BENZODITHIADIAZINE, FORMALLY ANTIAROMATIC 12-PI-ELECTRON COMPOUNDS

The He I photoelectron spectra of formally antiaromatic 12pi-electron 1,3,2,4-benzodithiadiazine and 5,6,7,8-tetra-fluoro-1,3,2,4-benzodithiadiazine have been measured and interpreted using the perfluoro (pi-fluoro) effect as well as MNDO and PM 3 calculations. The molecules of both compounds have a united molecular pi-system but the hetero-atom-induced tendency of pi MOs to localize on separate molecular fragments reduces their potential antiaromaticity. Because of this the title compounds are closer to the conjugated nonaromatic rather than traditional antiaromatic substances.