Csaba P. Keszthelyi

Electrogenerated Chemiluminescence XI . Electrochemistry and Electrogenerated Chemiluminescence in Scintillator Dye Melts

Melts of sc int i l la tor compounds which are solid at room tempera ture , such as 2 ,5-diphenyloxazole (PPO) and 2 ,5-diphenyloxadiazole (PPD) conta ining severa l qua te rna ry ammonium salts as suppor t ing electrolytes , were examined as solvents for e lec t rochemical and e lec t rogenera ted chemi luminescence (ECL) studies. Al though the resistance of these solutions was high, cyclic vo l t ammet ry of 9 ,10-diphenylanthracene and rubrene in PPO showed the product ion of s table radica l anions and cat ions for both compounds, and the ECL emission was essent ia l ly the same as the fluorescence emission of these compounds in PPO. ECL of rubrene was also observed in mol ten phenanthrene, PPD, th ianthrene , and p te rpheny l , as wel l as in mix tu res of PPO wi th 1or 2 -methy lnaphtha lene . There has been much interest in recent years in the appl icat ion of nonaqueous solvents in e lec t rochemis t ry (1). Many of these solvents have the advan tage of r a the r wide potent ia l l imits before the solvent i tself or the suppor t ing e lec t ro ly te undergoes reduct ion or oxidat ion at an iner t electrode; these solvents are also often less l ike ly to react wi th e lec t rogenera ted species. Most solvents employed are l iquid at room t empera tu re [e.g., N,N-d ime thy l fo rmamide (DMF), acetoni t r i le (ACN)] while severa l l iquefy at low tempera tu res (SO2, NH3). Only a few studies of organic systems have employed as solvents compounds which are solid at room tempera tu re ; these include d imethylsu l fone (rap 127~ (1,2) , mol ten e thy lammonium chloride (3), and the A1CI~-KC1 mol ten salt sys tem (4). Recent studies involving aprot ic solvents include e lec t rogene ra ted chemiluminescence (ECL) of aromat ic compounds, whe re e lec t rogenera ted radica l anions (R T)

Electrogenerated chemiluminescence. XV. On the formation of excimers and exciplexes in ECL

Abstract The emission resulting from the reaction of electrogenerated radical anions ((A - + ) and cations (D - + ) (ECL) for four systems which provide evidence for the intermediacy of excimers or exciplexes is described. The effect of solvent and supporting electrolyte concentration and the energetics of the radical ion reaction on the nature of the emission is discussed and the results are compared with previous chemiluminescence studies of Weller and Zachariasse. For one system involving trans -stilbene radical anion and tri- p -tolylamine radical cation, only radiation attributable to an exciplex formed in the initial cation-anion encounter, is observed.

Electrogenerated chemiluminescence. XIV. Effect of supporting electrolyte concentration and magnetic field effects in the 9,10-dimethylanthracene-tri-p-tolylamine system in the tetrahydrofuran

Abstract A comparison of the efficiency of photon production in the chemiluminescence studies of Weller and Zachariasse and in ECL for the system involving reaction of 9,10-dimethylanthracene (DMA) radical union and tri- p -tolylamine (TPTA) radical cation in tetrahydrofuran (THF) solutions was undertaken. The luminescence intensity increased and the magnitude of the magnetic field effect decreased when the supporting electrolyte (TBAP) concentration was decreased from 0.2 M to 10 mM. The ECL efficiency, extrapolated to low TBAP concentrations, was in good agreement with that of the chemiluminescence studies.

On The Efficiency of Electrogenerated Chemiluminescence

Electrogenerated chemiluminescence (ECL) occurs when redox reactions between oxidizing and reducing species generated electrochemically result in the production of light. Since the reactant species are frequently radical ions, this luminescence is sometimes called radical ion chemiluminescence, although a number of cases of ECL have now been described where at least one of the reacting partners is not a radical ion. Because a number of reviews (1-6) on ECL have appeared since the initial experiments described in 1964, only a brief outline of the methods and recent results will be presented here. A review of the experimental methods in ECL and an outline of the results of the as yet unreviewed research of 19701972 will appear shortly. (7)