Dioxo derivatives of benzenoid hydrocarbons: Part IV - Dioxo-bisanthrenes

Depending on the position of the two oxo groups, isomeric dioxo derivatives of benzenoid hydrocarbons drastically differ in the extent and mode of pi- electron conjugation. We report here the results of AMI studies of the 14 K ekulean dioxo derivatives of bisanthrene (phenanthro-[1,10,9,8-o,p,q,r,a]pe rylene). Our calculations indicate that in this case also the relative stab ilities and the geometries of the dioxo derivatives are predominantly deter mined by pi-electron conjugation and to a lesser extent by steric repulsion of the oxo groups in positions 3,4,10 and/or 11, and by electrostatic repu lsion of near-lying oxo groups.