Bis-(para)-pseudo-ortho-4,7,12,15-tetrasubstituted
[2.2]paracyclophanes
(Fig. 3.7) were applied in the chemoselective Sonogashira-Hagihara coupling to
afford the corresponding diyne, which could be employed as a chiral building block
[36]. Different π-conjugated substituents could be introduced at the 4,12- and 7,15positions. As shown in Fig. 3.19, one-handed double helical structure was
constructed; for example, boomerang-shaped π-electron systems were stacked at
the second and fourth phenylene rings to form a left-handed helix from the (R p )isomer. The double helical compounds (R p , R p )- and (S p , S p )-17 were highly
emissive with excellent chiroptical properties in the ground state and, in particular,
in the excited state (|g lum | ¼ 1.6 Â 10
–3 ); that is to say, they were also excellent
organic CPL emitters [36].
Optically active V-shaped molecule 18 (Fig. 3.20) could be prepared from
MeO-substituted
bis-(para)-pseudo-ortho-4,7,12,15-tetrasubstituted
[2.2]
paracyclophane (Fig. 3.7) [37]. π-Electron systems were stacked at the terminal
benzene rings. The properties were compared with the corresponding X-shaped
molecule 16, in which the π-electron systems were stacked at the central benzene
rings. The CPL signs of the V- and X-shaped molecules were positive and negative,
respectively. Positive and negative CPL signs appeared from V-shaped molecule
(R p )-18 and X-shaped molecule (R p )-16, respectively. The stacking positions of the
two π-electron systems leads to the different CPL signs despite the same absolute
configuration.
The electronic transition dipole moments and magnetic transition dipole moments
from S1 to S0 of molecules 18 and 16 were simulated (Fig. 3.21); the simulation was
carried out for (S p )-isomers. The g lum value is defined by 4|μ||m|cosθ/(|μ|
2 +|m|
2 ),
where μ and m represent electric and magnetic transition dipole moments, respectively, and the θ represents the angle between the μ and m [54–56]. The sign of a g lum
value is decided by this angle. The angle θ between μ and m of (S p )-18 was estimated
to be 144
, while that of (S p )-16 was estimated to be 87
. Theoretical results
(R p )-13
solution
abs,max = 403 nm
= 0.36 x 10 5 M –1 cm –1
PL,max = 494 nm
PL = 0.58
|g lum | = –7.3 x 10 –4
aggregates
PL,max = 503 nm
PL = 0.24
|g lum | = –9.0 x 10 –4
solution
abs,max = 395 nm
x 10 5 M –1 cm –1
PL,max = 455 nm
PL = 0.78
|g lum | = 3.5 x 10 –3
aggregates
PL,max = 470 nm
PL = 0.03
|g lum | = 4.3 x 10 –3
(R p )-12
= 0.61
λ
λ
Φ
λ
λ
Φ
λ
Φ
λ
Φ
Fig. 3.16 Structures and optical data of X-shaped molecules 12 and 13
3 Circularly Polarized Luminescence from Planar Chiral Compounds Based on. . .
45
[2.2]paracyclophanes
(Fig. 3.7) were applied in the chemoselective Sonogashira-Hagihara coupling to
afford the corresponding diyne, which could be employed as a chiral building block
[36]. Different π-conjugated substituents could be introduced at the 4,12- and 7,15positions. As shown in Fig. 3.19, one-handed double helical structure was
constructed; for example, boomerang-shaped π-electron systems were stacked at
the second and fourth phenylene rings to form a left-handed helix from the (R p )isomer. The double helical compounds (R p , R p )- and (S p , S p )-17 were highly
emissive with excellent chiroptical properties in the ground state and, in particular,
in the excited state (|g lum | ¼ 1.6 Â 10
–3 ); that is to say, they were also excellent
organic CPL emitters [36].
Optically active V-shaped molecule 18 (Fig. 3.20) could be prepared from
MeO-substituted
bis-(para)-pseudo-ortho-4,7,12,15-tetrasubstituted
[2.2]
paracyclophane (Fig. 3.7) [37]. π-Electron systems were stacked at the terminal
benzene rings. The properties were compared with the corresponding X-shaped
molecule 16, in which the π-electron systems were stacked at the central benzene
rings. The CPL signs of the V- and X-shaped molecules were positive and negative,
respectively. Positive and negative CPL signs appeared from V-shaped molecule
(R p )-18 and X-shaped molecule (R p )-16, respectively. The stacking positions of the
two π-electron systems leads to the different CPL signs despite the same absolute
configuration.
The electronic transition dipole moments and magnetic transition dipole moments
from S1 to S0 of molecules 18 and 16 were simulated (Fig. 3.21); the simulation was
carried out for (S p )-isomers. The g lum value is defined by 4|μ||m|cosθ/(|μ|
2 +|m|
2 ),
where μ and m represent electric and magnetic transition dipole moments, respectively, and the θ represents the angle between the μ and m [54–56]. The sign of a g lum
value is decided by this angle. The angle θ between μ and m of (S p )-18 was estimated
to be 144
, while that of (S p )-16 was estimated to be 87
. Theoretical results
(R p )-13
solution
abs,max = 403 nm
= 0.36 x 10 5 M –1 cm –1
PL,max = 494 nm
PL = 0.58
|g lum | = –7.3 x 10 –4
aggregates
PL,max = 503 nm
PL = 0.24
|g lum | = –9.0 x 10 –4
solution
abs,max = 395 nm
x 10 5 M –1 cm –1
PL,max = 455 nm
PL = 0.78
|g lum | = 3.5 x 10 –3
aggregates
PL,max = 470 nm
PL = 0.03
|g lum | = 4.3 x 10 –3
(R p )-12
= 0.61
λ
λ
Φ
λ
λ
Φ
λ
Φ
λ
Φ
Fig. 3.16 Structures and optical data of X-shaped molecules 12 and 13
3 Circularly Polarized Luminescence from Planar Chiral Compounds Based on. . .
45