Enhanced Electrogenerated Chemiluminescence in the Presence of Fluorinated Alcohols

摘要

The electrochemistry, UV-vis absorption, photoluminescence(PL), and coreactant electrogenerated chemiluminescence (ECL) of Ru(bpy)_(3~(2+)) (where bpy velence 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+))/H_(2)O 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 ((phi)_(ec1) velence number of photons per redox event) was observed. However, dramatic increases in (phi)_(ec1) ranging from 6- to 270-fold were seen in mixed alcohol/water solutions.