Electrogenerated chemiluminescence . 41 . Electrogenerated chemiluminescence and chemiluminescence of the Ru ( 2 , 2 1 - bpy ) 32 + - S 2 O 82 - system in acetonitrile - water solutions

The electrogenerated chemiluminescence (ecl) produced in acetonitrile-water solutions (1: 1 by volume) by the reaction of electrogenerated Ru(bpy),+ with the strongly oxidizing intermediate, SO4--, generated during reduction of S208” is described. The orange luminescence (A, = 625 nm) corresponds to emission from R~(bpy) ,~+*. The relative ecl intensity is a function of S20s2concentration, and for a 1 mM R~(bpy)~’+ solution the maximum ecl intensity was obtained at 15-20 mM S20s2-. Slightly higher concentrations (>30 mM S2OS2-) effectively quench light emission because of the R ~ ( b p y ) , ~ + * S ~ 0 ~ ~ reaction. The ecl efficiency (photons produced/electrons consumed) was -5% and was insensitive to dissolved Oz. A chemiluminescence based on reduction with Mg metal is also described. A large number of reactions have been discovered in which excited states are generated by energetic electron transfers.’ These usually involve the reaction of strong reductants (A;) and strong oxidants (D’.) generated (usually electrochemically) in an aprotic solvent such as acetonitrile (MeCN). These reactions usually