Inhibition of Ru Complex Electrochemiluminescence by Phenols and Anilines

The effect of 30 phenols and anilines on typical Ru complex electrochemiluminescence (ECL) was systematically investigated under different conditions. It was found that all the tested compounds showed an ECL inhibiting signal. The magnitude of ECL inhibition was related to the position of the substituting group in the benzene ring and decreased in the following order: meta‐>ortho‐>para‐. The oxidation potential of the tested compounds, the ECL spectra and UV‐visible absorption spectra of Ru(bpy)$\rm{ {_{3}^{2+}}}$/tripropylamine (TPrA) in the presence of phenols and anilines, and the direct ECL between Ru(bpy)$\rm{ {_{3}^{2+}}}$ and phenols/aniline were studied. The mechanism of ECL inhibition has been proposed due to energy transfer from the excited state Ru(bpy)$\rm{ {_{3}^{2+}}}$$\rm{{^\cdot}}$ to a quinone or ketone or their polymer formed by electro‐oxidation of phenols and anilines. The potential of analytical application was explored by use of the inhibited ECL. The results demonstrate that numerous compounds are detectable with the detection limits in the range of 10⁻⁸–10⁻⁹ mol/L for Ru(bpy)$\rm{ {_{3}^{2+}}}$/TPrA system and in the range of 10⁻⁶–10⁻⁷ mol/L for Ru(bpy)$\rm{ {_{3}^{2+}}}$/C₂O$\rm{ {_{4}^{2}}}$ system, respectively.