Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
Supplementary information for:
Rapid cleavage of naphthylmethyl-oxygen bond in the higher triplet
excited states
Xichen Cai, Masanori Sakamoto, Michihiro Hara, Sachiko Tojo, Mamoru Fujitsuka,
Akihiko Ouchi, and Tetsuro Majima*
The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Mihogaoka 8-1, Ibaraki,
Osaka 567-0047, Japan. E-mail: majima@sanken.osaka-u.ac.jp
National Institute of Advanced Industrial Science and Technology, 1-1-1, Higashi, Tsukuba, Ibaraki 3058565, Japan
I, 1-Np(T1)CH2-OBP and 2-Np(T1)CH2-OBP
Very similar transient absorptions to those of naphthalene(Np)(T1) and 1methylnaphthalene(T1) of 1-Np(T1)CH2-OBP and 2-Np(T1)CH2-OBP at 395 and 420 nm
were obtained when benzophenone(BP) was selected as the triplet sensitizer with 355-nm
laser irradiation in Ar-saturated acetonitrile at room temperature. The peaks of 1Np(T1)CH2-OBP and 2-Np(T1)CH2-OBP at 395 and 420 nm can be quenched by O2, and
the peak intensity was almost same to that of Np(T1) at the same concentrations of Np
and 1-NpCH2-OBP and 2-NpCH2-OBP. Therefore, it is reasonable to assume that the
extinction coefficients () of 1-Np(T1)CH2-OBP and 2-Np(T1)CH2-OBP in cyclohexane
are similar to that of Np(T1) in nonpolar solvents. We selected the value of 13200 M-1cm1
of 420 for 1-Np(T1)CH2-OBP and 2-Np(T1)CH2-OBP.1
II, The C-O bond cleavage of 2-NpCH2-OBP(Tn)
Similar experimental results to those of 1-NpCH2-OBP(Tn) were obtained for 2NpCH2-OBP(Tn). The bleaching of the transient absorption of 2-Np(T1)CH2-OBP at 420
nm and the formation of 2-NpCH2 radical at 380 nm were observed during the twocolour two-laser flash photolysis of 2-NpCH2-OBP (1.0  10-3 M) in Ar-saturated
cyclohexane, Figs. S1-S3.
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Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
O.D.
0.10
O.D.
0.01
a
0.00
2-NpCH2
2-NpCH2
0.05
b
-0.01
350 360 370 380 390 400
 (nm)
0.00
350
400
450
500
550
 (nm)
Fig. S1 Transient absorption spectra of 2-NpCH2-OBP obtained at 1 μs after the second
430-nm laser irradiation during the two-colour two-laser flash photolysis in Ar-saturated
cyclohexane at room temperature, 355-nm laser only (a) (broken line), 355 and 430-nm
lasers together (b) (solid line). The delay time between the first 355-nm laser and the
second 430-nm laser irradiation was 100 ns. The inset shows spectrum obtained by (b)(a) in the region of 350 - 400 nm.
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Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
O.D.420
0.15
O.D.420
0
5
0.10
10
0.05
0.00
0
200
400
600
t (ns)
800
1000
Fig. S2 Kinetic traces illustrating the time profiles of O.D.420 during the two-colour twolaser flash photolysis of 2-NpCH2-OBP in Ar-saturated cyclohexane at room
temperature.2 The delay time between the first 355-nm laser and the second 430-nm laser
irradiation was 100 ns, the second 430-nm laser power was 0 (black), 5 (red), and 10
(blue lines) mJ pulse-1.
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Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
O.D.380
O.D.380
10
0.02
0
0.00
0
200
400
600
t (ns)
800
1000
Fig. S3 Kinetic traces illustrating the time profiles of O.D.365 during the two-colour twolaser flash photolysis of 2-NpCH2-OBP in Ar-saturated cyclohexane at room temperature.
The dotted line shows the corrected O.D.380 for 2-NpCH2. The delay time between
the first 355-nm laser and the second 430-nm laser irradiation was 100 ns, the second
430-nm laser power was 0 and 10 mJ pulse-1.
The rapid formation of the transient absorption at 420 and 380 nm after the first 355-nm
laser irradiation corresponds to the formation of 2-Np(T1)CH2-OBP. The change of the
transient absorption at 380 nm by the second 430-nm laser irradiation involves the effects
of both the bleaching of 2-Np(T1)CH2-OBP and the formation of 2-NpCH2.
The concentration of 2-NpCH2 was calculated to be 1.9  10-6 M from |O.D.420|,
|O.D.380|, 420 of 13200 M-1cm-1 for 2-Np(T1)CH2-OBP,1 and 380 of 5000  300 M1
cm-1 for 2-NpCH2.3 This indicates that 2-Np(T1)CH2-OBP disappeared was converted
stoichiometrically to 2-NpCH2 through the cleavage of the C-O bond of 2-NpCH2OBP(Tn). Plotting |O.D.420| vs 430-nm laser power, the linear line was obtained as
shown in Fig. S4. Therefore, the quantum yield of 2-NpCH2 () was calculated to be
0.020  0.002 from the slope of the line and  of 13200 M-1cm-1.1
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Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
|O.D.420|
0.03
0.02
0.01
0.00
0
2
4
6
8
-1
 (mJpulse )
10
12
Fig. S4 Plots of |O.D.420| vs the 430-nm laser power (I).
The mechanism of the C-O bond cleavage of 2-NpCH2-OBP is shown in Scheme S1
2-Np-CH2-O-BP
h
2-Np-CH2-O-BP
S1
2-Np-CH2-O-BP
T1
2-Np-CH2-O-BP
Tn
< 5 ns
EM
< 5 ns
~2%
2-Np-CH2-O-BP
T1
2-Np-CH2 +
< 100 ps
ISC
h
~98%
O-BP
Scheme S1 Two-colour two-laser flash photolysis of 2-NpCH2-OBP in Ar-saturated
cyclohexane at room temperature. The dotted squares show the predominat energy
location. ISC: Intersystem crossing. EM: Energy migration.
Notes and references
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Supplementary material (ESI) for Chemical Communications
This journal is © The Royal Society of Chemistry 2003
(1)
(2)
(3)
S. L. Murov; I. Carmichael; G. L. Hug Handbook of Photochemistry; Marcel Dekker, Inc.:
New York, 1993.
In order to show the time profiles clearly, 20 times average data of the original one were
given here. Therefore, the time ranges of bleaching of the transient absorption at 420 nm
and formation at 365 nm or 380 nm were appeared to be longer than 5 ns. In fact the
bleaching and formation of the transient absorption occurred within laser duration (5 ns).
This average has no effect on the calculation of the quantum yield of 1-NpCH2and 2NpCH2. radicals.
S. Watanabe; M. Nagano; T. Suzuki; T. Ichimura. J. Photochem. Photobiol., A 2000, 137,
125.
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