Electrochemiluminescence and chemiluminescence of a carboxylic acid derivative of ruthenium(II) tris-(2,2′-bipyridine) chelate synthesized for labeling purposes

Synthesis, purification and characterization of 4-ethoxycarbonyl-4′-carboxy-2,2′-bipyridine]bis(2,2′-bipyridine) ruthenium(II) hexafluorophosphate is described. This complex is shown to be electrochemiluminescent in aqueous solution during cathodic pulse polarization of thin insulating film-coated electrodes. Electrochemiluminescence (ECL) lifetime of the complex was observed to be ca. 40 μs at oxide-coated n-silicon electrodes; thus time-resolved detection is also possible. The ECL emission maximum of this carboxylate derivative is somewhat red-shifted when compared with an unmodified Ru(bpy)₃²⁺. Because the present complex can be easily covalently coupled with antibodies and oligonucleotides it is usable as an electrochemiluminescent label in various bioaffinity assays. The present chelates also produce strong chemiluminescence during dissolution of metallic magnesium in aqueous solution.