63 but their CPL activities were smaller, with dissymmetry factors of 3.0 Â 10
À3
and 2.5 Â 10
À3
, respectively. These values are comparable to that of silole-fused
compound 51 (vide supra). In 2015, Hasobe and coworkers reported a highly yellow
fluorescent [7]carbohelicene fused by asymmetric 1,2-dialkyl-substituted quinoxaline
(65) [61]. It displayed a fluorescence quantum yield of 0.25 at 550 nm emission
wavelength which is more than 10 times larger than that of the pristine heptahelicene
(Φ F ¼ 0.02). Such a large enhancement of fluorescence in 65 also provided good
CPL activity, with g lum values of Æ4.0 Â 10
À3
. A negative CPL signal for the (P)-(+)
isomer, i.e., an S-type one (vide supra and [20, 22]), corresponding to the small
negative ECD signal at 435 nm with a g abs of À1.3 Â 10
À3
. Note also that this
compound was successfully used as an emitter in OLEDs but the authors did not
report any CPL emission of the OLED.
Table 4.11 Photophysical data of heptahelicenic derivatives
Compound λ Abs
max a (nm) λ Em (nm) Φ (%) Solvent (CPL) 10
3 g abs 10
3 g lum Ref.
(M )-(À)-62 388
428
32
CHCl 3
À2.5
b
À30
[59]
(M )-(À)-63 400
449
29.6
CHCl 3
À2.9
b
À32
[59]
(P)-(+)-64a 400
417
39
CH 2 Cl 2
1.3
b
3
[ 60]
(P)-(+)-64b 408
421
40
CH 2 Cl 2
–
2.5
[60]
(P)-(+)-65
435
550
25
THF
À1.3
À4
[ 61]
a Lowest energy UV-vis band
b
Taken from [12]
2
0
–2
6
4
2
0
250
300
350
400
Wavelength, nm
10 –4
e, M –1
cm –1
10 –5
q, deg cm 2
dmol –1
l
L –l
R , a.u.
Intensity, a.u.
450
500
550
3
1
0
–1
2
1
0
PL
UV
ECD
a
b
CPL
Fig. 4.25 (a) ECD/CPL
spectra of heptahelicenic
fluorene 63 in CH 2 Cl 2 . Blue
lines in ECD and CPL
spectra: (P)-isomer. Red
lines: (M )-isomer and
(b) UV-vis/fluorescence
spectra. Reproduced with
permission [59]. Copyright
2012, American Chemical
Society
82
J. Crassous
À3
and 2.5 Â 10
À3
, respectively. These values are comparable to that of silole-fused
compound 51 (vide supra). In 2015, Hasobe and coworkers reported a highly yellow
fluorescent [7]carbohelicene fused by asymmetric 1,2-dialkyl-substituted quinoxaline
(65) [61]. It displayed a fluorescence quantum yield of 0.25 at 550 nm emission
wavelength which is more than 10 times larger than that of the pristine heptahelicene
(Φ F ¼ 0.02). Such a large enhancement of fluorescence in 65 also provided good
CPL activity, with g lum values of Æ4.0 Â 10
À3
. A negative CPL signal for the (P)-(+)
isomer, i.e., an S-type one (vide supra and [20, 22]), corresponding to the small
negative ECD signal at 435 nm with a g abs of À1.3 Â 10
À3
. Note also that this
compound was successfully used as an emitter in OLEDs but the authors did not
report any CPL emission of the OLED.
Table 4.11 Photophysical data of heptahelicenic derivatives
Compound λ Abs
max a (nm) λ Em (nm) Φ (%) Solvent (CPL) 10
3 g abs 10
3 g lum Ref.
(M )-(À)-62 388
428
32
CHCl 3
À2.5
b
À30
[59]
(M )-(À)-63 400
449
29.6
CHCl 3
À2.9
b
À32
[59]
(P)-(+)-64a 400
417
39
CH 2 Cl 2
1.3
b
3
[ 60]
(P)-(+)-64b 408
421
40
CH 2 Cl 2
–
2.5
[60]
(P)-(+)-65
435
550
25
THF
À1.3
À4
[ 61]
a Lowest energy UV-vis band
b
Taken from [12]
2
0
–2
6
4
2
0
250
300
350
400
Wavelength, nm
10 –4
e, M –1
cm –1
10 –5
q, deg cm 2
dmol –1
l
L –l
R , a.u.
Intensity, a.u.
450
500
550
3
1
0
–1
2
1
0
PL
UV
ECD
a
b
CPL
Fig. 4.25 (a) ECD/CPL
spectra of heptahelicenic
fluorene 63 in CH 2 Cl 2 . Blue
lines in ECD and CPL
spectra: (P)-isomer. Red
lines: (M )-isomer and
(b) UV-vis/fluorescence
spectra. Reproduced with
permission [59]. Copyright
2012, American Chemical
Society
82
J. Crassous