Calculation of 1H chemical shifts of conjugated alternant hydrocarbons with (4m) rings

The 1H chemical shifts of the polycyclic alternant hydrocarbons bicyclo[6.2.0]decapentaene, cycloocta[def]biphenylene, dicycloocta[1,2,3,4‐def: 1′,2′,3′,4′‐jkl]biphenylene and cycloocta[1,2,3,4‐def]benzo[3,4]cyclobuta[6,7]biphenylene, which contain an 8‐membered ring, are calculated by means of a semi‐empirical approach. The agreement between experimental and calculated shifts is good if geometries are determined by a self‐consistent resonance integral, or even better by a π‐SCF force field procedure. Predictions are made for the as yet unknown dianions of these hydrocarbons