On the triplet states of polynucleotide–acridine complexes. I. Triplet energy delocalization in the 9‐aminoacridine–DNA complex

Abstract

Abstract Phosphorescence and fluorescence from the dye in complexes of DNA with 9‐amino‐acridine and acridine orange in a glycerol‐H 2 O glass have been measured at 77°K. The dependence of the p / f ratio for 9‐aminoacridine on the exciting wavelength demonstrates triplet–triplet energy transfer from DNA to dye. The result provides evidence for π electron overlap between the dye and the bases of native DNA. The observation that the magnitude of the enhancement in ultraviolet‐excited dye phosphorescence increases with the base to dye ratio indicates triplet delocalization in the polymer. Preliminary flash experiments provide evidence that this delocalization is not limited by slow diffusion of the triplet exciton. The inability to detect transfer on denaturation of the DNA illustrates the sensitivity of triplet–triplet energy transfer to the conformation of the macromolecular complex.