Valence tautomerism of singly protonated 9-aminoacridine and its implications for intercalative interactions with nucleic acids

Abstract

Electronic absorption and fluorescence spectroscopy were used to show that the singly protonated 9-aminoacridine cation exists as the vinylogous cyclic amidine valence tautomer, the 9-iminoacridan monocation, in ground and excited states when in aqueous solution at physiological pH. The evidence indicates that the 9-aminoacridine monocation may intercalate into double-helical DNA in an orientation different from that employed by other acridine derivatives.