Light-induced
blinking, an inherent feature of many forms of super-resolution
microscopy, has been linked to transient reduction of the fluorescent
cyanine dye used as an imaging agent. There is, however, only scant
literature information related to one-electron reduced cyanine dyes,
especially in an aqueous environment. Here, we examine a small series
of cyanine dyes, possessing disparate π-conjugation lengths,
under selective reducing or oxidizing conditions. The experiment allows
recording of both differential absorption spectra and decay kinetics
of the resultant one-electron reduced or oxidized transient species
in water. Relative to the ground state, absorption transitions for
the various radicals are weak and somewhat broadened but do allow
correlation with the π-conjugation length. In all cases, absorption
maxima lie to the blue of the main ground-state transition. Under
anaerobic conditions, the transient species decay on the microsecond
to millisecond time scale, with the mean lifetime depending on molecular
structure, radiation dose, and dye concentration. The experimental
absorption spectra recorded for the one-electron reduced radicals
and the presumed dimer cation radical compare well to spectra obtained
from time-dependent density functional theory calculations. The results
allow conclusions to be drawn regarding the plausibility of the reduced
species being responsible for light-induced blinking in direct stochastic
optical reconstruction microscopy.