1,6,7,10-TETRAMETHYLFLUORANTHENE - SYNTHESIS AND STRUCTURE OF A TWISTED POLYNUCLEAR AROMATIC HYDROCARBON

The structure and synthesis of the overcrowded polynuclear aromatic 1,6,7,10-tetramethylfluoranthene, 1, is presented. The structures of 1 and 11 have been determined by X-ray diffraction to be twisted into conformations of approximately C2 symmetry due to the buttressing of the flanking methyl groups. Semi-empirical calculations (AM1) on 1 find two minima, twist and fold; the twist is of lower energy. The energy for enantiomerization of 1 is set at below 7.0 kcal/mol by variable temperature NMR. Computations predict a likely path to account for the ribbon twist.