Effect of DNA Scaffolding on Intramolecular Electron Transfer Quenching of a Photoexcited Ruthenium(II) Polypyridine Naphthalene Diimide.

Intramolecular emission quenching of a photoexcited ruthenium(II) polypyridine by a covalently linked naphthalene diimide (NDI) has been measured in aqueous buffer both without and with calf thymus DNA. The complex consists of a Ru(2,2'-bipyridine)(2)(2,2'-bipyridine-5-carboxamide)(2+) electron donor covalently attached by way of a -CH(2)CH(2)CH(2)- linker to a 1,4,5,8-naphthalene diimide acceptor (Ru-NDI, 1). The NDI portion of the complex intercalates in calf thymus DNA, as indicated by the hypochromism of its optical absorbance bands and observation of an induced circular dichroism spectrum in the same region.