Chemistry Reference
In-Depth Information
50 µs
8 µs
5.5 µs
4 µs
3 µs
2.6 µs
2 µs
10 ns
1300
1400
1500
1600
1700
1800
Raman shift (cm
-1
)
FIGURE 7.24.
Selected TR
3
spectra obtained by 368.9 nm probe after 309.1 nm photolysis of
0.3mM 2-fluorenyl azide in the presence of 0.9mM C8-bromoguansoine in a water-
acetonitrile (50:50) mixed solvent with a 0.002M Na
2
HPO
4
:0.002M NaH
2
PO
4
buffer are
shown. The time-delays between the pump (309.1 nm) and probe (368.9 nm) laser beams are
given to the right of each spectrum and the Raman shifts of selected bands are shown at the top
of the 50
m
s spectrum. See text for more details.
Source
: Reprinted with permission fromRef.
46. Copyright (2007) American Chemical Society.
(a)
(b)
(c)
The major species
T
growth
=840 ns
The major intermediate
T
growth
=835 ns
The major intermediate
T
growth
=1765 ns
Nitrenium ion
T
decay
=835 ns
Nitrenium ion
T
decay
=840 ns
Nitrenium ion
T
decay
=1765 ns
0
1000
2000
3000
4000
5000
6000
7000
8000
0
2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
0
2000
4000
6000
8000
Time delay (ns)
Time delay (ns)
Time delay (ns)
FIGURE 7.25.
Plots of the integrated areas for the characteristic Raman features for the
species seen in the TR
3
spectra of Figure 7.22 (a), Figure 7.23, (b), and Figure 7.24 (c). The
data for about 1630 cm
1
Raman band for the 2-fluorenyl nitrenium ion are given as open
squares and the data for the characteristic Raman feature for the respective major intermediate
Raman bands at about 1614 cm
1
are presented as open triangles as a function of time-delay
between the pump and probe laser pulses. The data were fit to simple exponential growth
and/or decay functions as indicated by the curves in the graphs. The time constants for the best-
fit exponential kinetics are indicated next to the appropriate curves for the 2-fluorenyl
nitrenium ion decay and the growth of the major intermediates.
Source
: Reprinted with
permission from Ref. 46. Copyright (2007) American Chemical Society.
