Abstract Several novel important heterocyclic N‐2‐hydroxypropyl and N‐2‐hydroxy‐3‐chloropropyl quaternary salts were prepared by reaction of propylene oxide and epichlorohydrin with the appropriate heterocyclic bases in the presence of perchloric or hydrobromic acid, giving pure compounds without colored by‐products. The reaction products have an activated methyl group in 2‐ or 4‐position and are typical
towards GC-DNA base pairs over AT-DNA, which included both binding affinity and a strong fluorescence response. CD titrations showed aggregation along the polynucleotide with well-defined supramolecular chirality. The single dipyridinium-bridged dimer showed intercalation at low dye-DNA/RNA ratios. All new cyaninedyes showed potent micromolar antiproliferative activity against cancer cell lines, making