Synthesis and Electrochemiluminescence of a Ru(bpy)_3^2+ -Labeled Coupling Adduct Produced on a Self-Assembled Monolayer

In this work a series of silicon chips containing sputtered gold electrodes, were first coated with a SAM of lipoic acid. The same electrodes were then functionalized by using a Ru(bpy)_3^2+ amine derivative, bis(2,2'-bipyridine)-[4-(4'-methyl-2,2'-bipyridin-4-yl)aminobutyl] ruthenium bis(hexafluorophosphate). Its synthesis and purification is reported in detail for the first time. A two-steps preparation of the emitting layer increased both the compactness of the SAM and the density of Ru emitting sites, as evidenced by ECL and XPS investigations. This approach enables the preparation of reproducible and compact ECL active mono-layers containing bulky molecules without the need of preliminary purification of the labelled surfactant. The occurrence of the coupling surface reaction was detected by monitoring the electrochemically induced luminescence from the modified electrode, in the presence of tripropylamine as oxidative co-reactant and was confirmed by ToF-SIMS and XPS measurements.