Covalent Attachment of a Platinum(II) Complex inside DNA Duplexes

An organometallic phosphorescent Pt II complex is introduced into DNA duplexes via oxidative addition to a tailor‐made artificial nucleobase, acting as an N^N^C donor ligand. Its covalent attachment to the nucleic acid backbone localizes the metal ion in the center of the duplex. The platination exerts a stabilizing effect of up to 6.4 °C on the duplex, with the degree of stabilization depending on the identity of the nucleobase in the complementary position. No interstrand crosslink is formed, as indicated by mass‐spectrometry and corroborated by almost identical photoluminescence lifetimes ( τ ) in Ar‐purged solution. In air‐equilibrated solution, τ shows moderate dependence on the complementary nucleobase, suggesting that the latter influences oxygen accessibility to the luminophore. When two Pt II complexes are incorporated in neighboring positions, a redshifted luminescence from aggregates is observed in addition to monomer emission, indicating Pt···Pt interactions along the helical axis. The approach presented here allows the site‐specific incorporation of highly stable Pt II complexes as phosphorescent tags into nucleic acids.