molar absorption coefficient (ε) of 130,000M
À1 cm
À1 indicates that this molecule
emits bright PL. In addition, optically active propeller-shaped molecules 6 [45] and
7 [46] were prepared (Fig. 3.13). Both the compounds exhibited high molar absorption coefficients, good Φ PL , and large CPL g lum values.
Simple X-shaped molecules have been synthesized from 4,7,12,15-tetraethynyl
[2.2]paracyclophane [47], and the structures and other data are briefly shown in
Fig. 3.15. The phenyl- and naphthyl-containing molecules, 8 and 9, emitted intense
CPL, while a weak CPL signal was observed from the anthracene-containing
molecule 10. In particular, the naphthyl-containing molecule 9 was an excellent
CPL emitter, with a large g lum in the order of 10
–3 , large ε of 0.79 Â 10
5 cm
–1 M
–1 ,
and good Φ lum of 0.78.
Figure 3.15 shows an optically active X-shaped molecule (R p )-11 that emits
intense CPL, with a Φ PL of 0.87 in a dilute solution and the g lum value of
À1.2 Â 10
À3 [48]. The g lum value of the spin-coated film was positive with
g lum ¼ +2.1 Â 10
À2 , which was larger by an order of magnitude. Furthermore, the
g lum value of the annealed thin film was negative and in the order of 10
–1 (À0.25).
The g lum value of the thin film obtained by the casting method was negative and still
larger by an order of magnitude (À3.0 Â 10
À2 ). When it was annealed, the sign was
reversed, and the same g lum value (À0.25) was observed. An optically active higherordered structure was formed in the thin film because of the van der Waals force of
the long alkyl chains and π-π interactions. Thus, a thermodynamically stable higherordered structure was formed by annealing.
Not only arylene-ethynylenes but also arylene-vinylenes were chosen as
π-electron systems. Figure 3.16 shows the optically active X-shaped molecules
consisting of arylene-vinylenes prepared from 4,7,12,15-tetraethynyl[2.2]
paracyclophane [49]. Molecule 12 [40, 49] exhibited aggregation-caused quenching
of PL (Φ PL ¼ 0.03) because of the high planarity of the stacked π-electron system,
while 13 exhibited moderate PL properties both in the dilute solution (Φ PL ¼ 0.58)
and in the aggregated state (Φ PL ¼ 0.24). In the dilute solution, 12 showed good CPL
properties (Φ PL ¼ 0.78 and |g lum | ¼ 3.7 Â 10
À3 ), and in the aggregated state, 13
showed good CPL properties (Φ PL of 0.24 and |g lum | ¼ +0.90 Â 10
À3 ) which were
observed.
Fig. 3.12 Plausible conformations of linear trimer 2 and cyclic trimer 4
3 Circularly Polarized Luminescence from Planar Chiral Compounds Based on. . .
41
À1 cm
À1 indicates that this molecule
emits bright PL. In addition, optically active propeller-shaped molecules 6 [45] and
7 [46] were prepared (Fig. 3.13). Both the compounds exhibited high molar absorption coefficients, good Φ PL , and large CPL g lum values.
Simple X-shaped molecules have been synthesized from 4,7,12,15-tetraethynyl
[2.2]paracyclophane [47], and the structures and other data are briefly shown in
Fig. 3.15. The phenyl- and naphthyl-containing molecules, 8 and 9, emitted intense
CPL, while a weak CPL signal was observed from the anthracene-containing
molecule 10. In particular, the naphthyl-containing molecule 9 was an excellent
CPL emitter, with a large g lum in the order of 10
–3 , large ε of 0.79 Â 10
5 cm
–1 M
–1 ,
and good Φ lum of 0.78.
Figure 3.15 shows an optically active X-shaped molecule (R p )-11 that emits
intense CPL, with a Φ PL of 0.87 in a dilute solution and the g lum value of
À1.2 Â 10
À3 [48]. The g lum value of the spin-coated film was positive with
g lum ¼ +2.1 Â 10
À2 , which was larger by an order of magnitude. Furthermore, the
g lum value of the annealed thin film was negative and in the order of 10
–1 (À0.25).
The g lum value of the thin film obtained by the casting method was negative and still
larger by an order of magnitude (À3.0 Â 10
À2 ). When it was annealed, the sign was
reversed, and the same g lum value (À0.25) was observed. An optically active higherordered structure was formed in the thin film because of the van der Waals force of
the long alkyl chains and π-π interactions. Thus, a thermodynamically stable higherordered structure was formed by annealing.
Not only arylene-ethynylenes but also arylene-vinylenes were chosen as
π-electron systems. Figure 3.16 shows the optically active X-shaped molecules
consisting of arylene-vinylenes prepared from 4,7,12,15-tetraethynyl[2.2]
paracyclophane [49]. Molecule 12 [40, 49] exhibited aggregation-caused quenching
of PL (Φ PL ¼ 0.03) because of the high planarity of the stacked π-electron system,
while 13 exhibited moderate PL properties both in the dilute solution (Φ PL ¼ 0.58)
and in the aggregated state (Φ PL ¼ 0.24). In the dilute solution, 12 showed good CPL
properties (Φ PL ¼ 0.78 and |g lum | ¼ 3.7 Â 10
À3 ), and in the aggregated state, 13
showed good CPL properties (Φ PL of 0.24 and |g lum | ¼ +0.90 Â 10
À3 ) which were
observed.
Fig. 3.12 Plausible conformations of linear trimer 2 and cyclic trimer 4
3 Circularly Polarized Luminescence from Planar Chiral Compounds Based on. . .
41