Azino-fused benzimidazolium salts as DNA intercalating agents .2.

The synthesis of new pyrido[1,2-a]- and pyridazino[1,6-a]benzimidazolium salts by basic condensation of 1,3-disubstituted 2-alkylbenzimidazolium salts and 1,2-diketones and subsequent chemical transformations is described. The DNA-binding properties were examined by UV-vis spectroscopy, viscosimetric determinations, and molecular modeling techniques. The presence of a flat polycyclic hydrocarbon moiety such as a naphthalene-1,8-diyl or a biphenyl-o,o'-diyl, fused to the cationic heterocycle, appears to enhance the interaction with DNA. Variation of the substituents on the indole-like N will allow us to build up a new series of his-salts with bis-intercalating properties.