dipole–dipole interaction between the isoxazole rings. On the other hand, the assembly of 29 formed in toluene displayed completely different characteristics compared to
that in chloroform. The assembly formed in toluene was CD active, and mirror-image
CD signals were observed upon the assembly of (S)- and (R)-29. Thus, helical
assemblies are formed, and the helical senses were directed by the chiral side-chains.
The assembly in toluene exhibited aggregation-induced emission enhancement
(AIEE); the emission is strongly enhanced in the assembled form compared to that
of the monomeric species. The molecular motion, presumably the rotation of the triple
bond, is prevented through the formation of the assembly to reduce the nonradiative
decay of the excited state, which results in the increase in the emission. The monomeric 29 did not display any CD and CPL even in toluene, but the assembly formed in
toluene exhibited CPL with a g lum of 1.0 Â 10
À2
.
Spano, Meskers, and coworkers have developed the self-assembly and chiroptical
properties of oligo-p-phenylene-vinylene derivative 30 (Fig. 9.15) [46]. 30
dimerized through the complementary quadruple hydrogen bond of the triazine
group, and then, the dimer assembled to form a helical stacked assembly via π–π
stacking. The helical assembly exhibited CPL on its fluorescence with a g lum on
the order of 10
À3 . Wong, Tang, and coworkers have developed the CPL of
tetraphenylsilole derivatives. Tetraphenylsiloles are known as good aggregationinduced emission (AIE) active luminophores; the luminophore is not emissive in
its monomeric form, but the aggregate of the luminophore is highly emissive.
For example, 31, a tetraphenylsilole derivative possessing chiral sugar pendants,
formed a helical assembly displaying CPL in its suspension and solid state
(Fig. 9.15) [47]. The g lum values of 31 depend on the state of the assembly. In
a heterogeneous suspension, a neat static cast film, and 10 wt.% Poly(methyl
methacrylate) (PMMA) matrix, the g lum values were ca. À0.12, À0.08, and À0.17,
respectively. Interestingly, the fabricated pattern obtained by the evaporation of a
dichloromethane/toluene solution of 31 in Teflon-based microfluidic channels
N
N
Pt
N O
N
O
OR
RO
(S)-29: R =
(R)-29: R =
non-helical assembly
helical assembly
in c h lo ro fo rm
in to lu e n e
CPL
Fig. 9.14 CPL-active helical assembly of 29, a Pt(II)phenylbipyridine complex possessing
phenylisoxazoles. Adapted with permission from Schippers et al. [10]. Copyright 2015 The
Royal Society of Chemistry
9 Circularly Polarized Luminescence of Chirally Arranged Achiral Organic. . .
211
that in chloroform. The assembly formed in toluene was CD active, and mirror-image
CD signals were observed upon the assembly of (S)- and (R)-29. Thus, helical
assemblies are formed, and the helical senses were directed by the chiral side-chains.
The assembly in toluene exhibited aggregation-induced emission enhancement
(AIEE); the emission is strongly enhanced in the assembled form compared to that
of the monomeric species. The molecular motion, presumably the rotation of the triple
bond, is prevented through the formation of the assembly to reduce the nonradiative
decay of the excited state, which results in the increase in the emission. The monomeric 29 did not display any CD and CPL even in toluene, but the assembly formed in
toluene exhibited CPL with a g lum of 1.0 Â 10
À2
.
Spano, Meskers, and coworkers have developed the self-assembly and chiroptical
properties of oligo-p-phenylene-vinylene derivative 30 (Fig. 9.15) [46]. 30
dimerized through the complementary quadruple hydrogen bond of the triazine
group, and then, the dimer assembled to form a helical stacked assembly via π–π
stacking. The helical assembly exhibited CPL on its fluorescence with a g lum on
the order of 10
À3 . Wong, Tang, and coworkers have developed the CPL of
tetraphenylsilole derivatives. Tetraphenylsiloles are known as good aggregationinduced emission (AIE) active luminophores; the luminophore is not emissive in
its monomeric form, but the aggregate of the luminophore is highly emissive.
For example, 31, a tetraphenylsilole derivative possessing chiral sugar pendants,
formed a helical assembly displaying CPL in its suspension and solid state
(Fig. 9.15) [47]. The g lum values of 31 depend on the state of the assembly. In
a heterogeneous suspension, a neat static cast film, and 10 wt.% Poly(methyl
methacrylate) (PMMA) matrix, the g lum values were ca. À0.12, À0.08, and À0.17,
respectively. Interestingly, the fabricated pattern obtained by the evaporation of a
dichloromethane/toluene solution of 31 in Teflon-based microfluidic channels
N
N
Pt
N O
N
O
OR
RO
(S)-29: R =
(R)-29: R =
non-helical assembly
helical assembly
in c h lo ro fo rm
in to lu e n e
CPL
Fig. 9.14 CPL-active helical assembly of 29, a Pt(II)phenylbipyridine complex possessing
phenylisoxazoles. Adapted with permission from Schippers et al. [10]. Copyright 2015 The
Royal Society of Chemistry
9 Circularly Polarized Luminescence of Chirally Arranged Achiral Organic. . .
211