Spectroscopic and synthetic methods have been exploited
to deduce the mechanism for acidic potassium permanganate
chemiluminescence. We have employed electron
paramagnetic resonance (EPR) spectroscopy with a continuous
flow assembly to monitor the formation of radical
intermediates in real time generated from substrate
oxidation by manganese(VII). These transient species
react with manganese(III) in solution to produce the
previously characterized manganese(II)* emission source.
Using UV-vis, EPR, attenuated total reflection (ATR)-FTIR,
and chemiluminescence spectroscopies, we have
established that there are two distinct enhancement
mechanisms that in combination afford a 50-fold increase
in emission intensity when the reaction is conducted in
the presence of phosphate oligomers. In addition to
preventing disproportionation of the manganese(III) precursor,
the phosphate oligomers form protective “cagelike”
structures around the manganese(II)* emitter, thus
preventing nonradiative relaxation pathways.