Electrogenerated chemiluminescence. VI. Efficiency and mechanisms of 9,10-diphenylanthracene, rubrene, and pyrene systems at a rotating-ring-disk electrode

The actinometric calibration of the rotating-ring-disk electrode (rrde) system allowed the determination of the electrogenerated chemiluminescence (ecl) efficiency, 9,,, , for several systems of interest. The efficiency for 9,lO-diphenylanthracene (DPA) ecl in dimethylformamide solutions was below 0.1 %. Studies performed on the DPA-tetramethyl-p-phenylenediamine (TMPD) system showed that ecl occurs during reaction of DPA. with either TMPD. f or TMPD2+; the efficiency for this ecl is about an order of magnitude smaller than for DPA alone. TMPD was also shown to be an effective quencher of DPA ecl in these systems. Rrde studies of the rubrene (R) system demonstrated that 9eol was much smaller for it than for the DPA system and that reaction of R2+ with R . or R2with R + produced light at high rotation rates. A detailed study of the pyrene (P)-TMPD system was undertaken. The A study of the relative pyrene excimer to monomer emission in both ecl and fluorescence demonstrated the existence of a direct path to excimer in ecl, consistent with the triplet-triplet annihilation mechanism. Quenching of pyrene ecl by TMPD was also investigated. for the P-TMPD system was smaller than that for the DPA-TMPD system. t is of considerable interest in studies of electrogenI erated chemiluminescence (ecl) to determine the overall ecl efficiency, which represents the fracdirected. tion of radical ion encounters which ultimately result in the emission of a photon. Studies of ecl at the rotating-ring-disk electrode (rrde) are ideally suited for such efficiency measurements, since the radical ion precursers are generated continuously under steady-state (1) To whom correspondence and requests for reprints should be Journal of the American Chemical Society 1 93:23 / November 17, 1971