272
S. Kobatake
(Antiparallel)
(Parallel)
Open-ring isomer
S
N
N
S
S
CH 3
H 3 C
Vis.
S
N
N
S
S
CH 3
H 3 C
S
N
N
S
S
Me
Me
H
Closed-ring isomer
UV
Fig. 7.10 Diarylethene showing photocyclization quantum yield of approximately unity
(a) π-conjugation length
(b) Polarity of substituent at the reactive position
(c) Oxidation of thiophene ring
c→o = 0.075
F2
F2
F2
S
S
CH3
H3C
NC
CN
CH3
H3C
c→o = 1.3 10 −3
F2
F2
F2
S
S
CH3
H3C
CH3
H3C
S
S
NC
CN
c→o = 1.3 10 −4
F2
F2
F2
S
S
CH3
H3C
CH3
H3C
S
S
S
S
CN
NC
F2
F2
F2
S
S
CH3
H3C
F2
F2
F2
S
S
CN
NC
F2
F2
F2
S
S
OCH3
H3CO
c→o = 0.41
c→o = 1.3 10 −2
c→o = 1.7 10 −5
F2
F2
F2
S
S
CH3
H3C
F2
F2
F2
S
O2
S
CH3
H3C
F2
F2
F2
S
O2
S
O2
CH3
H3C
F2
F2
F2
S
S
CH3
H3C
F2
F2
F2
S
O2
S
CH3
H3C
c→o = 1.3 10 −2
c→o = 2.7 10 −4
c→o = 0.28
c→o = 0.074
c→o = 0.061
Φ
Φ
Φ
Φ
Φ
Φ
Φ
Φ
Φ
Φ
Φ
Fig. 7.11 Factors affecting photocycloreversion quantum yield of diarylethenes