Temperature dependence of the electrogenerated chemiluminescence efficiency of Ru(bpz)/sub 3//sup 2 +/ in acetonitrile. A mechanism interpretation

Journal Article · Thu Apr 21 00:00:00 EDT 1988 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100319a024· OSTI ID:7256091

Gonzalez-Velasco, J

The temperature dependence of the electrogenerated chemiluminescence (ECL) efficiency (eta/sub ECL/) and the quantum yield (phi/sub p/) of Ru(bpz)/sub 3//sup 2 +/ has been measured. Also the temperature dependence of the luminescence quantum yield (phi/sub p/) of the lowest Ru(bpz)/sub 3//sup 2 +/ d-..pi..* metal-to-ligand charge-transfer (MLCT) excited state was determined. In the low-temperature range (between 5 and 35/sup 0/C), eta/sub ECL/ and phi/sub p/ increase with decreasing temperature, while the ratio eta/sub ECL/A phi/sub p/ remains nearly constant. At higher temperatures (between 35 and 75/sup 0/C), a sharp decline in the eta/sub ECL/A phi/sub p/ ratio is attributed to the disappearance of the Ru(bpz)/sub 3//sup 3/ ECL precursor, by reaction with the solvent. Evidence that this reaction takes place is demonstrated by the ECL dependence on pulsing frequency and pulsing limit, as well as by the ECL variation with temperature. Changes in the anodic and cathodic waves recorded in voltammograms as well as an alteration in the absorption spectrum of the original solution induced by the repetitive pulsing and by a temperature increase support this supposition. The similarity in the eta/sub ECL/ and phi/sub p/ values in the low-temperature range is attributed to the efficient formation of the excited state by an electron-transfer reaction between Ru(bpz)/sub 3//sup 3 +/ and Ru(bpz)/sub 3//sup +/ formed during the anodic and cathodic potential pulses, respectively. Unlike for the Ru(bpy)/sub 3//sup 2 +/ case the ECL efficiency is limited only by the luminescence quantum yield at low temperatures, whereas at higher temperatures eta/sub ECL/ is limited mainly by a decomposition reaction of the 3+ precursor formed during the anodic pulse and by quenching of the excited state by reaction products or solvent.

• Research Organization: Universidad Autonoma de Madrid (Spain)
• OSTI ID: 7256091
• Journal Information: J. Phys. Chem.; (United States), Vol. 92:8
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
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PHYSICAL AND ANALYTICAL CHEMISTRY
42 ENGINEERING
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ACETONITRILE
CATIONS
CHEMILUMINESCENCE
ELECTRON TRANSFER
EXPERIMENTAL DATA
QUANTUM EFFICIENCY
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EFFICIENCY
HETEROCYCLIC COMPOUNDS
INFORMATION
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LUMINESCENCE
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