New dyes based on amino-substituted acridizinium salts - Synthesis and exceptional photochemical properties

The novel amino-substituted acridizinium salts 5a and 5b represent a new cl ass of cyanine dyes which exhibit intense color along with efficient fluore scence properties. These dyes show moderate solvatochromism in their absorp tion and emission spectra. The absorption and emission shifts of the two ch romophores display a reasonable correlation with solvent parameters such as donor and acceptor number, It was found that the dyes 5a and 5b interact w ith DNA, with quenching of the band intensies accompanied with a red shift of the absorption and emission bands. Moreover, irradiation of salts 5a and 5b in the presence of DNA results in DNA damage. Solution photolysis of ac ridizinium salt 5a gave the head-totail dimers as the major products (>95%) , whereas the acridizinium salt 5b afforded the anti-head-to-tail dimer alo ng with both head-to-head isomers. The latter are thermally labile and rapi dly revert to the monomer.