Luminescent electrooxidation of methanol in aqueous alkaline media

First observation of luminescence from tris(2,2'-bipyridine)ruthenium(II) triggered by anodic oxidation of oligodeoxyribonucleotide

Anodic oxidation of oligodeoxyribonucleotide in an alkaline aqueous medium containing tris(2,2'-bipyridine)ruthenium(II) (Ru(bpy)3(2+)) was shown to cause luminescence around +1.3 V (vs. Ag/AgCl) with a maximal intensity at approximately 600 nm, possibly originating from Ru(bpy)3(2+) in the d-pi* triplet state. A pivotal initial stage in the light production path was postulated to be the anodic oxidation of 2-deoxyribose residue. This reaction seems to be available for the determination of sub-micromol dm(-3) levels of oligodeoxyribonucleotide.

Enhanced Electrogenerated Chemiluminescence in the Presence of Fluorinated Alcohols

The electrochemistry, UV-vis absorption, photoluminescence (PL), and coreactant electrogenerated chemiluminescence (ECL) of Ru(bpy)3(2+) (where bpy=2,2'-bipyridine) have been obtained in a series of hydroxylic solvents. The solvents included fluorinated and nonfluorinated alcohols and alcohol/water mixtures. Tri-n-propylamine was used as the oxidative-reductive ECL coreactant. Blue shifts of up to 30 nm in PL emission wavelength maximums are observed compared to a Ru(bpy)3(2+)/H2O standard due to interactions of the polar excited state (i.e., *Ru(bpy)3(2+)) with the solvent media. For example, Ru(bpy)3(2+) in water has an emission maximum of 599 nm while in the more polar hexafluoropropanol and trifluoroethanol it is 562 and 571 nm, respectively. ECL spectra are similar to PL spectra, indicating the same excited state is formed in both experiments. The difference between the electrochemically reversible oxidation (Ru(bpy)3(2+/3+)) and first reduction (Ru(bpy)2(2+/1+)) correlates well with the energy gap observed in the luminescence experiments. Although the ECL is linear in all solvents with [Ru(bpy)3(2+)] ranging from 100 to 0.1 nm, little correlation between the polarity of the solvent and the ECL efficiency (phiecl=number of photons per redox event) was observed. However, dramatic increases in phiecl ranging from 6- to 270-fold were seen in mixed alcohol/water solutions.