Hydride reduction of the tetracyclic isoindolium salt derivatives 2a - c yields the neutral isoindole derivatives 9-chloro-1,2,3,4,6,6a,7,12b-octahydrobenzo[ƒ]pyrido[2,1-a]isoindole (3a), 4,4a,5,7,8,9,10,10a-octahydropyrido[2,1-a]thieno[3,2-f]isoindole (3b), and 10-chloro- 2,3,4,5,7,7a,8,13b-octahydro-1H-azepino[ƒ]pyrido[2,1-a]isoindole (3c). Oxidation of 3a with selenium dioxide is accompanied by a ring transformation and yields 8-chloro-5,5a,6,12-tetrahydrobenzo[g]pyrrolo[1,2-b]isoquinolin-12-one (4). Deprotonation of isoindolium salt derivatives 2a,c,d yields cyclic enamines which undergo ring expansion with dimethyl acetylenedicarboxylate resulting in compounds with the 4,5,6,8,8a,9-hexahydroazocino[2,1-a]benzo[ƒ]isoindole (6a), 4,6,7,9,9a,10-hexahydro-5H-azonino[2,1-a]benzo[ƒ]isoindole (6c) and 4a,5,7,8,9,10-hexahydro- 4H-azonino[2,1-a]thieno[3,2- ƒ]isoindole (6d) skeleton. Interactions of 2 with double-stranded nucleic acids are characterized by relatively large NMR upfield shifts (0.25 ppm) and signal broadening (by about 45 Hz) of aromatic ligand signals, indicating at least partial stacking with nucleobases. Rather small effects are observed, however, in melting point and viscosity increase with double strands; this is tentatively ascribed to competitive interactions with unfolded polymer parts.