PROBING THE CHARGE DELOCALIZATION MODE IN METHYL-BRIDGED, DIMETHYL-BRIDGED AND METHYLENE-BRIDGED PHENANTHRENIUM IONS - NMR-STUDIES OF PERSISTENT MONO-AND DI-CATIONS AND AM1 CALCULATIONS

Superacid protonation studies are reported on 2-methyl-(1), 3-methyl-( 2), 3,6-dimethyl-phenanthrene (3) and 4H-cyclopenta[def]phenanthrene ( 4). In FSO3H-SO2CIF persistent monocations 1H(+)-4H(+) are generated, 3 gives a symmetrical dication by protonation with FSO3H . SbF5(4:1)-S O2CIF or with 'magic acid'-SO2ClF. 1 and 2 are partially diprotonated in 'magic acid'-SO2ClF. The observed mono-and di-cations are in most c ases those predicted by AM1 to be the most stable, Correlation between the magnitude of Delta delta(13C), and AM1 calculated changes in carb on changes [Delta q = q(c)(ion) - q(c)(neutral)] is also examined. The charge alternation paths in the mono-and di-cations are compared and discussed, A parallel is drawn between stable ion and AM1 studies of m ethylphenanthrenes and the solvolytic studies of K-region and non-K-re gion phenanthrene oxides.