Table 5.1
Summarized photophysical parameters of [7]carbohelicene derivatives (reprinted with permission from Ref. [21]. Copyright 2015 American
Chemical Society)
Helicene
τ FL
a
(ns)
Φ FL
b
Φ ISC
c
Φ IC
k
FL
 10
À7
(s
À1
)
k
ISC
 10
À7
(s
À1
)
k
IC
 10
À7
(s
À1
)
S
1
–S 0
(eV)
T
1
–S 0
(eV)
S
1
–T 1
(eV)
ε 0–0 (M
À1
cm
À1
)
[7]Hl-Qx
1.66
0.05 0.96
0.00 3.01
57.8
–
2.62
1.93
0.69
14,500
[7]HlNAIQx
4.00
0.25 0.62
0.13 6.25
15.5
3.25
2.42
1.56
0.86
4700
[7]Hl
13.8
d
0.02
d
(~0.9)
e
–
0.145
d
(~6.5)
f
–
2.79
g
2.12
h
0.67
h
474
i
τ FL
fluorescence lifetime,
Φ FL
fluorescence quantum yield,
Φ ISC quantum yield of intersystem crossing,
Φ IC quantum yield of internal conversion, k
FL
fluorescence rate constant, k
ISC rate constant of intersystem crossing, k
IC rate constant of internal conversion. S
1
–S 0 : determined by steady-state absorption and
fluorescence spectra. T
1
–S 0 : determined by phosphorescence spectra at 77 K.
ε 0–0 : molar absorption coefficients of 0–0 absorption bands.
Φ IC
¼ 1–Φ
FL
–Φ ISC ,
k
FL
¼ Φ FL
• τ FL
À1
, k
ISC
¼ Φ ISC
• τ FL
À1
, k
IC
¼ Φ IC
• τ FL
À1
a
Excitation wavelength: 404 nm
b
Excited at 330 nm
c
Excited at 450 nm
d
Reported values in 1,4-dioxane [29–31]
e
The value was estimated using the reported results such as pristine [6]carbohelicene (Φ
ISC
¼ 0.91) [30], pristine [8]carbohelicene (Φ
ISC
¼ 0.92) [30] and
pristine [9]carbohelicene (Φ
ISC
¼ 0.91) [30]
f
Estimated value from
Φ ISC of [7]Hl: 0.9
g
Reported data [29]
h
Reported data [30]
i
Reported data [9]
5 Structural Control of Fluorescent Helicates for Improved Circularly Polarized. . .
103