4.2.6 Helicene Imide Derivatives
Aromatic diimides are known to display bright emission properties. In 2016,
Hasobe and coworkers reported [5]carbohelicene derivatives 21a,b fused with an
electron-withdrawing maleimide and substituted with electron-donating methoxy
NH
R 1
R 1
R 1
R 1
R 1 = C C Si(iPr) 3
(P)-18
O
R 1
R 1
R 1
R 1
(P)-19
R 2
R 2
(P)-21a: R 2 = H
(P)-21b: R 2 = OMe
N
O
O
(P)-22: R 3 = lone pair
(P)-22.H
+
: R 3 = H
+
N
O
N
R 3
NH
R 1
R 1
R 1
R 1
(P,P)-20
HN
R 1
R 1
R 1
R 1
(P)-23
Fig. 4.7 Chemical structures of pentahelicenes incorporating a carbazole (18) together with a
dimer (20) and a dibenzofurane analogue (19); pentahelicenes including imide functions (21a,b and
22, 22.H
+ ) together with pentacarbohelicene 23
Table 4.2 Photophysical data of helicenes fused with pyrroles or imide cycles
Compound
λ Abs
max a
(nm)
λ Em
(nm)
Φ F
(%)
Solvent
(CPL)
10
3
g abs
10
3
g lum
Ref.
(P)-(+)-18
503
560
36
CH 2 Cl 2
+1.4
b
+3
[24]
(P,P)-(+)-20 526
588
55
CH 2 Cl 2
À8.5
À8.5
[25]
(P)-(+)-21a
456
~480
37
THF
À4.8
À2.4
[26]
(P)-(+)-21b
475
~525
22
THF
À5.7
À2.3
[26]
(P)-(+)-22
450
575
6
CH 2 Cl 2
–
À9.45
[27]
(P)-(+)-22.
H
+
570
650
6
CH 2 Cl 2
–
À5.92
[27]
(P)-(À)-24a
366
445
12.8
THF
À1.55
À1.2
[28]
(P)-(À)-24b
366
457
19.2
THF
À1.33
À1.5
[28]
(P)-(À)-24c
371
482
64.8
THF
À1.35
À0.8
[28]
(P)-(À)-24d
387
556
40.3
THF
À1.31
À0.8
[28]
(P)-(À)-24e
415
617
7.4
THF
À3.53
À0.2
[28]
a Lowest-energy absorption band
b
Taken from [12]
4 Circularly Polarized Luminescence in Helicene and Helicenoid Derivatives
61