Dissertation

|3.2 Bisphenanthroline: A Suitable Molecular Bridge?|
1000
single photon counts
100
10
1
60
30
0
-30
-60
0 200 400 600 800 1000
time / ns
Figure 71: Fitted emission decay plots of Ru(phenphen): (● ● ●), Ru(phenphen)Ru: (● ● ●),
Ru(phenphen)Pt: (● ● ●) in oxygen saturated acetonitrile (top) and residue (bottom).
into a spatial profile on the detector to obtain the two dimensional spectra.
The false color plot in figure 72 shows exemplarily the two-dimensional spectra of the binuclear
complex Ru(phenphen)Ru in oxygen saturated and oxygen free acetonitrile. Laser excitation
at t = 0 (blue spot at λ = 355 nm) results in the formation of an 3 MLCT-excited species which
possesses a different absorption spectrum. The color code indicates the observed change of the
optical density of the sample during the experiment. The ground state bleach in the region
between 400 and 500 nm is the result of the decreased concentration of not excited ground state
Ru(phenphen)Ru upon transition of a fraction of Ru(phenphen)Ru-molecules into the excited
state (blue and green areas). Furthermore new absorption bands of the excited species between 300
and 400 nm and between 500 and 700 nm become prominent (red and orange areas). After few
microseconds the excited molecules relax to the ground state and the initial differential spectrum
with no change in optical density (baseline) results.
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