Automated solid-phase DNA synthesis and photophysical properties of oligonucleotides labeled at the 5 '-terminus with Ru(bpy)(3)(2+)

A facile procedure for the incorporation of Ru(bpy)(3)(2+) in an oligonucle otide is reported. A Ru(bpy)(3)(2+) phosphoramidite is synthesized, and the n attached to the 5'-terminus of DNA using a standard protocol on an automa ted DNA solid-phase synthesizer. Photophysical studies of the Ru(II) tris-d iimine complex as well as the corresponding labeled oligonucleotides demons trate that the excited-state electron is localized on one specific bipyridi ne with the dipole directed toward the linkage to DNA, and that the Ru(II) excited state is long-lived when attached to the DNA.