High-frequency electrochemiluminescent investigation of the reaction pathway between tris(2,2 '-bipyridyl)ruthenium(II) and tripropylamine using carbon fiber microelectrodes
Em. Gross et al., High-frequency electrochemiluminescent investigation of the reaction pathway between tris(2,2 '-bipyridyl)ruthenium(II) and tripropylamine using carbon fiber microelectrodes, J PHYS CH B, 105(37), 2001, pp. 8732-8738
The electrochemiluminescent (ECL) reaction mechanism between tris(2,2 ' -bi
pyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) and tripropylamine (TPrA) in aqueous
solution at pH 7.4 was examined using fast potential pulses at carbon fibe
r microelectrodes. High-stability ECL emission was found with 0.5 ms pulses
and a 25% duty cycle. In addition, stability was increased with negative r
est potentials. Direct evidence for the strongly reducing free radical inte
rmediate was obtained when the light was quenched upon addition of nitroben
zene derivatives. The formation of this free radical becomes rate-limiting
at high concentrations of Ru(bpy))(3)(2+) and TPrA, as its production can b
e limited when there is an insufficient supply of one or both of its precur
sors (TPrA and TPrA(.+)) relative to Ru(bpy)(3)(2+) When TPrA is insufficie
nt excess of Ru(bpy)(3)(2+), the ECL efficiency (photons emitted/Ru(bpy)(3)
(3+) generated) was determined to be very high (similar to 90%) by comparis
on to a Ru(bpy)(3)(2+)/Ru(bpy)(3)(+) standard in acetonitrile. Rapid potent
ial pulses also generated ECL from Ru(bpy)(3)(2+) when other tertiary amine
s, trimethylamine, diisopropylethylamine, and histamine, were used as co-re
actants. The secondary amine epinephrine also produced light, but not norep
inephrine, a primary amine.