Tris(Bipyridine) Ruthenium(II): An Efficient Detector of Excited Species Generated by Chemiluminescent Processes*

In systems that are known to generate electronically excited species, the tris(bipyridine) ruthenium(II) cation, Ru(bpy)32+, ion is found to be an efficient, chemically stable, emissive energy acceptor for probing excited state formation. The chemiexcitation system employed was the thermolysis of tetramethyldioxetane. The system employed for enzymatic generation of excited species was the horseradish peroxidase-catalyzed oxidation of appropriate substrates such as isobutyraldehyde, phenylacetal-dehyde and indoleacetic acid. The versatility of the Ru(bpy)32+ ion is exemplified by its capacity to detect excited state formation in both chemical and enzymatic systems and in homogeneous and microheterogeneous media. The long wavelength emission and chemical stability of Ru(bpy)32+ facilitate quantitative studies of the sensi-tization process. Possible routes leading to excitation of the Ru(bpy)32+ ion by the chemi- or enzyme-generated excited species include electronic energy transfer and electron transfer-induced luminescence.