Chemistry Reference
In-Depth Information
(a)
T
growth
= 1435(53) ns
T
decay
= 238(12) ns
0
1000
2000
3000
4000
5000
6000
Time delay (ns)
(b)
T
growth
= 926(40) ns
T
decay
= 179(4) ns
0
1000
2000
3000
4000
5000
6000
Time delay (ns)
FIGURE 7.15.
Plots of the integrated areas for the diagnostic Raman features for the
4-biphenyl nitrenium ion (1619 cm
1
) and the 4,4
0
-azobisbiphenyl (1440 cm
1
) species
seen in the TR
3
spectra of Figures 4.1 and 1S of Ref. 47 as a function of time-delay are presented.
(a) From Figure 7.14, 1mM of precursor was utilized; open circles: 4,4
0
-azobisbiphenyl, open
triangles: 4-biphenyl nitrenium ion. (b) From Figure 1S of Ref. 47, 2 mM of precursor was utilized;
closed circles: 4,4
0
-azobisbiphenyl, closed triangles: 4-biphenyl nitrenium ion. The time constants
for the best-fit exponential kinetics are given next to the relevant curves and the bracketed numbers
are the fitted uncertainties.
Source
: Reprinted with permission from Ref. 47. Copyright (2008)
American Chemical Society.
4-biphenyl nitrenium ion will not readily convert to its conjugate base, the singlet
nitrene that can then form a triplet nitrene by intersystem crossing (ISC).
The direct detection of the intermediate in the TR
3
spectra shows that the reaction
of the 4-bipenyl nitrenium ion with 4-biphenyl azide to form the 4,4
0
-azobisbiphenyl
product occurs in a stepwise way and DFT computations were done to help identify
the intermediate and to investigate the reaction mechanism. Two competing reaction
