10 Circularly Polarized Luminescence (CPL) Based on Planar …
357
Fig. 10.15 Optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane
The chiral unit was easily removed by hydrolysis to afford the optically
active phenol 33 (Fig. 10.16). The treatment of 33 with trifluoromethanesulfonic anhydride afforded the optically active 4,7,12,15-tetrasubstituted [2.2]paracyclophane 35. Subsequent Sonogashira-Hagihara coupling between the optically
active cyclophane 35 with trimethylsilyl (TMS) acetylene proceeded smoothly
to afford triyne 36 with good yield. Interestingly, Pd 2 (dba) 3 /P
t Bu 3 /CuI catalyst
system (dba = dibenzylideneacetone and P
t Bu 3 = tri(t-butyl)phosphine) led to
chemoselective coupling with bromo groups. Then, the remaining trifluoromethylsulfonyl group could be reacted with TMS acetylene using a PdCl 2 (dppf) catalyst (dppf = 1,1
-bis(diphenylphosphino)ferrocene) to give the optically active
tetrayne 37. The TMS groups were removed to give the optically active 4,7,12,15tetraethynyl[2.2]paracyclophane 38.
Optically active cyclic molecules 39–41 were synthesized with 38 serving as a
chiral building block (Fig. 10.17), and their chiroptical properties were revealed.
The large chirality was induced in both the ground state and the excited state. For
example, the specific rotation of 39 was approximately 1,500, and the molar ellipticity
reached 3,000,000 deg cm
2 dmol
−1 . Cyclic molecule 39 exhibited excellent CPL
profiles (Fig. 10.18), and the |g lum | value at λ PL,max was on the order of 10
−2 with
Φ PL of 0.45. In addition to the planar chirality of the [2.2]paracyclophane skeleton,
the chiral second-ordered structure, namely, the chiral two blades propeller-shaped
structure contributed to the chiral induction in the excited state. The propeller-shaped
molecules 40 (Gon et al. 2015) and 41 (Gon et al. 2016) showed a large molar
absorption coefficient, good Φ PL , and large CPL g lum value. Especially, propellershaped molecule 40 was also an excellent CPL emitter with a large g lum value and
good Φ PL of 0.60.
Optically active X-shaped molecules 42–44 were synthesized from 4,7,12,15tetrasubstituted [2.2]paracyclophane 38 (Fig. 10.19) (Gon et al. 2015). Various
aromatic units such as benzene, naphthalene, and anthracene could be introduced to
357
Fig. 10.15 Optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane
The chiral unit was easily removed by hydrolysis to afford the optically
active phenol 33 (Fig. 10.16). The treatment of 33 with trifluoromethanesulfonic anhydride afforded the optically active 4,7,12,15-tetrasubstituted [2.2]paracyclophane 35. Subsequent Sonogashira-Hagihara coupling between the optically
active cyclophane 35 with trimethylsilyl (TMS) acetylene proceeded smoothly
to afford triyne 36 with good yield. Interestingly, Pd 2 (dba) 3 /P
t Bu 3 /CuI catalyst
system (dba = dibenzylideneacetone and P
t Bu 3 = tri(t-butyl)phosphine) led to
chemoselective coupling with bromo groups. Then, the remaining trifluoromethylsulfonyl group could be reacted with TMS acetylene using a PdCl 2 (dppf) catalyst (dppf = 1,1
-bis(diphenylphosphino)ferrocene) to give the optically active
tetrayne 37. The TMS groups were removed to give the optically active 4,7,12,15tetraethynyl[2.2]paracyclophane 38.
Optically active cyclic molecules 39–41 were synthesized with 38 serving as a
chiral building block (Fig. 10.17), and their chiroptical properties were revealed.
The large chirality was induced in both the ground state and the excited state. For
example, the specific rotation of 39 was approximately 1,500, and the molar ellipticity
reached 3,000,000 deg cm
2 dmol
−1 . Cyclic molecule 39 exhibited excellent CPL
profiles (Fig. 10.18), and the |g lum | value at λ PL,max was on the order of 10
−2 with
Φ PL of 0.45. In addition to the planar chirality of the [2.2]paracyclophane skeleton,
the chiral second-ordered structure, namely, the chiral two blades propeller-shaped
structure contributed to the chiral induction in the excited state. The propeller-shaped
molecules 40 (Gon et al. 2015) and 41 (Gon et al. 2016) showed a large molar
absorption coefficient, good Φ PL , and large CPL g lum value. Especially, propellershaped molecule 40 was also an excellent CPL emitter with a large g lum value and
good Φ PL of 0.60.
Optically active X-shaped molecules 42–44 were synthesized from 4,7,12,15tetrasubstituted [2.2]paracyclophane 38 (Fig. 10.19) (Gon et al. 2015). Various
aromatic units such as benzene, naphthalene, and anthracene could be introduced to