Diazonia- and tetraazoniapolycyclic cations as motif for quadruplex-DNA ligands

It is demonstrated that even unsubstituted cationic ligands, namely the known diazoniadibenzochrysenes (1a, 1b) and the so far unreported tetraazoniapentaphenopentaphene ( 2), stabilize quadruplex DNA upon association; the ligand 2 exhibits essentially the same affinity towards the quadruplex as does 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine, however, with a significantly higher selectivity for quadruplex relative to duplex DNA.