Acridine-viologen dyads: Selective recognition of single-strand DNA through fluorescence enhancement

Tolylacridine-viologen dyads show distinct fluorescence emission changes in the presence of double-strand DNA (dsDNA) and single-strand DNA (ssDNA) depending on the position of the linkage. The para isomer shows fluorescence quenching in the presence of both dsDNA and ssDNA, while the ortho isomer interacts selectively with ssDNA with enhancement in fluorescence intensity.