Diazonia- and tetraazoniapolycyclic cations as motif for quadruplex-DNA ligandsElectronic supplementary information (ESI) available: Experimental details, synthesis of compound 2, calculated structures of 1a–quadruplex complex and 2; complete data on the DNA-binding properties of the ligands 1–3. See DOI: 10.1039/b812891j

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 2exhibits 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. [ABSTRACT FROM AUTHOR]