Automated Solid-Phase DNA Synthesis and Photophysical Properties of Oligonucleotides Labeled at the 5‘-Terminus with Ru(bpy)₃²⁺

Abstract

A facile procedure for the incorporation of Ru(bpy)32+ in an oligonucleotide is reported. A Ru(bpy)32+ phosphoramidite is synthesized, and then attached to the 5‘-terminus of DNA using a standard protocol on an automated DNA solid-phase synthesizer. Photophysical studies of the Ru(II) tris-diimine complex as well as the corresponding labeled oligonucleotides demonstrate that the excited-state electron is localized on one specific bipyridine with the dipole directed toward the linkage to DNA, and that the Ru(II) excited state is long-lived when attached to the DNA.