Ruthenium(II) dipyridoquinoxaline-norbornene: synthesis, properties, crystal structure, and use as a ROMP monomer

The synthesis, X-ray structure, and electrochemical and photophysical characterization of [Ru(phen)(2)dpq-n][PF(6)](2) (phen = phenanthroline, dpq-n = dipyridoquinoxaline-norbornene) are described. This complex contains a Ru(phen)(3)(2+) moiety in close conjugation with a norbornene unit and is the first example of a Ru(II) diimine complex capable of undergoing ring-opening metathesis polymerization. Luminescence studies of this complex showed an increase in quantum efficiency in polar solvents and in water. Preliminary ring-opening metathesis polymerization studies, carried out at low monomer-to-initiator ratio, showed the formation of an oligomeric mixture composed mainly of the dimer of this complex. This dimer exhibits photophysical and redox properties similar to those of the monomer, indicating that the Ru(phen)(3)(2+) moiety remains intact during the polymerization.