Theoretical (DFT, GIAO–NMR, NICS) study of carbocations (M+H) + , dications (M 2+ ) and dianions (M 2− ) from dihydro-dicyclopenta[ef,kl]heptalene (dihydro-azupyrene), dihydro-dicyclohepta[ed,gh]pentalene, and related bridged [14]annulenes