O
P
•
+
•+
O•
O•
O
DCA•–
1DCA*
DCA•–
1a•+
1a
+
3a
O
O
P
O
3a•+
O
Scheme 2
(a)
Footnotes
0
.15
.10
.05
.00
† E-mail: nakamura@esci.eng.himeji-tech.ac.jp
Since the Stern–Volmer constants, k t, in the fluorescence quenching of
‡
q
1
21
DCA* by 1 and 2 were found to be 270–320 m for 1 and 2, k
q
= (1.6–
was calculated to be approximately equal to the
diffusion-controlled rate constant from the lifetime of DCA*, t = 14.9 ns
using the literature value (ref. 5). The oxidation potentials, E 1/2, of 1 and
were measured by cyclic voltammetry at a platinum electrode in dry
MeCN with 0.1 m Et NClO as a supporting electrolyte. The free energy
10
21 21
2
.1) 3 10
m
s
0
0
0
1
ox
2
4
4
changes, DGet, were calculated by using the Rehm–Weller equation (refs. 5
and 8).
§
Laser flash photolyses of the sample solutions were performed at room
2
1
temperature by a flash at 355 nm (5 ns, 20 mJ pulse ) obtained by the third-
harmonic oscillation from a Nd:YAG laser (ref. 9).
400
500
600
l / nm
700
800
¶ g-Radiolyses of the samples in degassed butyl chloride at 77 K were
60
23
22
performed by a Co g source; concentration of substrate, 10 to 10
m
(
b)
(c)
(ref. 10).
4
00 nm
520 nm
∑
Pulse radiolyses of the sample solutions were performed at room
temperature using an electron pulse (8 ns, 28 MeV) obtained from a linear
accelerator at Osaka University (ref. 11).
1
0 µs
10 µs
References
t
t
1
(a) G. W. Sluggett, P. F. McGarry, I. V. Koptyug and N. J. Turro, J. Am.
Chem. Soc., 1996, 118, 7367; (b) M. Nakamura, Y. Okamoto and
S. Takamuku, Chem. Commun., 1996, 209; (c) M. Nakamura,
K. Sawasaki, Y. Okamoto and S. Takamuku, Bull. Chem. Soc. Jpn.,
Fig. 2 (a) Transient absorption spectral changes during pulse radiolysis of
a in argon-saturated 1,2-dichloroethane: (2) immediately after the pulse,
5) 5 ms after the pulse, and (D) 20 ms after the pulse. Kinetic traces
illustrating the time profiles of (b) DOD400 and (c) DOD520
1
(
.
1
995, 68, 3189; (d) S. Ganapathy, K. P. Dockery, A. E. Sopchik and
W. G. Bentrude, J. Am. Chem. Soc., 1993, 115, 8863.
2
T. Furuta, H. Torigai, M. Sugimoto and M. Iwamura, J. Org. Chem.,
immediately after an 8 ns pulse, and decayed with formation of
1
995, 60, 3953; M. C. Pirrung and S. W. Shuey, J. Org. Chem., 1994,
.
+
new bands at 480 and 520 nm assigned to 3a at the first-order
59, 3890; R. S. Givens and L. W. Kuepper, III, Chem. Rev., 1993, 93,
55.
4
21
rate constant of k = 8.9 3 10 s
.
.
+
On the other hand, the spectrum of 1c showed sharp bands
at 390 and 440 nm and a broad band at 550–700 nm, was
slightly different in the shape and peak wavelength from that for
3 S. Yasui, K. Shioji, A. Ohno and M. Yoshihara, J. Org. Chem., 1995, 60,
099.
4
2
Photoinduced Electron Transfer, ed. M. A. Fox and M. Chanon,
Elsevier, Amsterdam, The Netherlands, 1988; S. L. Mattes and S. Farid,
in Organic Photochemistry, ed. A. Padwa, Marcel Deckker, New York,
.
+
1
a , and decayed without formation of any new bands. It is well
.
+
known that naphthalene dimerises with a neutral naphthalene
1
983; vol. 6, pp. 233–326; U. C. Yoon and P. S. Mariano, Acc. Chem.
to form a p-dimer radical cation with a 580 nm band at the
Res., 1992, 25, 233; V. D. Parker, Acc. Chem. Res., 1984, 17, 243;
L. Eberson, Adv. Phys. Org. Chem., 1982, 18, 79; J. Mattay, Top. Curr.
Chem., 1990, 156, 219; G. J. Kavarnos and N. J. Turro, Chem. Rev.,
1986, 86, 401.
2
1
6
equilibrium constant of K = 520 m in PhCN, and that 1,3-di-
.
+
1
-naphthylpropane forms a stable intramolecular dimer radi-
cal cation. Phosphate 1a in the singlet excited state forms
7
intramolecularly a face-to-face excimer between two naphthyl
5 I. G. Gould, D. Ege, J. E. Moser and S. Farid, J. Am. Chem. Soc., 1990,
112, 4290.
6 A. Kira, S. Arai and M. Imamura, J. Phys. Chem., 1972, 76, 1119.
7 Y. Tsujii, A. Tsuchida, S. Ito and M. Yamamoto, Macromolecules,
groups.1c Therefore, a face-to-face structure between two
.
+
naphthyl groups is suggested to be present in 1a , decomposing
.
+
into 3a .
Consequently, electron transfer from 1a to DCA* occurs to
give 1a and DCA , 1a with the face-to-face structure
between two naphthyl groups decomposes to 3a and the
residue, and 3a is finally formed as the stable product from the
1
991, 24, 4061.
1
8
9
D. Rehm and A. Weller, Isr. J. Chem., 1970, 8, 259; A. Weller, Z. Phys.
Chem. (Munich), 1982, 133, 93.
T. Majima, S. Tojo, A. Ishida and S. Takamuku, J. Org. Chem., 1996,
61, 7793.
.
+
.
2
.
+
.
+
.
+
.
2
reduction of 3a with DCA (Scheme 2).
10 S. Tojo, K. Morishima, A. Ishida, T. Majima and S. Takamuku, Bull.
Chem. Soc. Jpn., 1995, 68, 958.
We thank Professor Setsuo Takamuku and Professor Yoshiki
Okamoto for helpful discussions, Dr Akito Ishida, Mrs Sachiko
Tojo and Miss Tomoko Hashikawa for their help with the
experiments, and the members of the Radiation Laboratory of
ISIR, Osaka University, for running the linear accelerator. This
work was partly supported by the Saneyoshi Scholarship
Foundation (M. N.) and a Grant-in-Aid (No. 08240229) from
the Ministry of Education, Science, Sport and Culture of Japan
1
1 A. Ishida, M. Fukui, H. Ogawa, S. Tojo, T. Majima and S. Takamuku,
J. Phys. Chem., 1995, 99, 10808; T. Majima, M. Fukui, A. Ishida and
S. Takamuku, J. Phys. Chem., 1996, 100, 8913; T. Majima, S. Tojo,
A. Ishida and S. Takamuku, J. Phys. Chem., 1996, 100, 13615;
T. Majima, S. Tojo, A. Ishida and S. Takamuku, J. Phys. Chem. A, 1997,
1
01, 1048.
(T. M.).
Received in Cambridge, UK, 2nd April 1997; Com. 7/02230A
1292
Chem. Commun., 1997