THEORETICAL-STUDY ABOUT THE RADICALS AND ANIONS OF [8]ANNULENES

The structure and electronic properties of the radical anions and dian ions of sym-dibenzo-1,5-cyclooctadiene-3,7-diyne, dibenzo[a,e]-cyclooc tene and sym-dibenzo-1,3,5-cyclooctadiene-7-yne are studied from a the oretical point of view. The geometries obtained by the theoretical rou tes, MP2/3-21G, show that all radical anions and dianions are planar c onjugated in agreement with experimental results. The calculated exalt ation indicates that the radical anions can show some degree of aromat icity or antiaromaticity and that all dianions are aromatic. (C) 1997 Elsevier Science B.V.