contribute to the emission quenching [57, 58]. Furthermore, the secondary aggregation might also increase the probability of intermolecular energy transfer.
The reversible modulation of CPL intensity upon photo-irradiations was
performed (Fig. 8.17c). Along with the emission quenching, the CPL signal also
diminished. As demonstrated in the emission quenching study, the CPL signal
intensity basically responds to the conversion ratio between 2o and 2c in a linear
fashion in chloroform. However, the appreciable emission quenching did not need a
high conversion ratio in the aggregate state (Fig. 8.17b), proposing the more efficient
and high-contrast CPL photo-switching system. The CPL intensity (I L À I R ) was
reversibly switched between ON and OFF states for 8 cycles with consecutive
UV-visible light irradiations.
8.6 Summary and Outlook
In this chapter, we introduced a design concept and several examples of CPL photoswitches which modulate CPL activity in response to light irradiation. Photoresponsive units are combined with fluorophore units in a chiral molecular system.
The CPL intensity can be controlled by means of energy transfer quenching by the
formation of a quencher unit upon photochromic reaction. The CPL activity is also
controlled in terms of the exciton coupling modulation in response to the chiral
geometrical change induced by the stereo-specific photo-reaction. The photoswitching effect could be enhanced in the chiral supramolecular systems.
Highly pure CPL could be generated by the use of selective reflection in a
cholesteric liquid crystalline phase [59, 60]. Helical pitch, handedness, and arrangement of mesogens in such chiral liquid crystalline system can be modulated by the
photo-reaction of chiral photochromic dopants [61–64]. High speed and dynamic
modulation of highly pure CPL could find applications for 3D displays, energysaving organic light-emitting diode (OLED) devices, switchable lasers, and optical
memory devices [65].
References
1. Maeda H, Bando Y, Shimomura K, Yamada I, Naito M, Nobusawa K, Tsumatori H, Kawai T
(2011) Chemical-stimuli-controllable circularly polarized luminescence from anion-responsive
π-conjugated molecules. J Am Chem Soc 133:9266–9269
2. Saleh N, Moore B, Srebro M, Vanthuyne N, Toupet L, Williams JA, Roussel C, Deol KK,
Muller G, Autschbach J, Crassous J (2015) Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes.
Chem Eur J 21:1673–1681
3. Amako T, Nakabayashi K, Mori T, Inoue Y, Fujiki M, Imai Y (2014) Sign inversion of
circularly polarized luminescence by geometry manipulation of four naphthalene units introduced into a tartaric acid scaffold. Chem Commun 50:12836–12839
192
T. Nakashima and T. Kawai
The reversible modulation of CPL intensity upon photo-irradiations was
performed (Fig. 8.17c). Along with the emission quenching, the CPL signal also
diminished. As demonstrated in the emission quenching study, the CPL signal
intensity basically responds to the conversion ratio between 2o and 2c in a linear
fashion in chloroform. However, the appreciable emission quenching did not need a
high conversion ratio in the aggregate state (Fig. 8.17b), proposing the more efficient
and high-contrast CPL photo-switching system. The CPL intensity (I L À I R ) was
reversibly switched between ON and OFF states for 8 cycles with consecutive
UV-visible light irradiations.
8.6 Summary and Outlook
In this chapter, we introduced a design concept and several examples of CPL photoswitches which modulate CPL activity in response to light irradiation. Photoresponsive units are combined with fluorophore units in a chiral molecular system.
The CPL intensity can be controlled by means of energy transfer quenching by the
formation of a quencher unit upon photochromic reaction. The CPL activity is also
controlled in terms of the exciton coupling modulation in response to the chiral
geometrical change induced by the stereo-specific photo-reaction. The photoswitching effect could be enhanced in the chiral supramolecular systems.
Highly pure CPL could be generated by the use of selective reflection in a
cholesteric liquid crystalline phase [59, 60]. Helical pitch, handedness, and arrangement of mesogens in such chiral liquid crystalline system can be modulated by the
photo-reaction of chiral photochromic dopants [61–64]. High speed and dynamic
modulation of highly pure CPL could find applications for 3D displays, energysaving organic light-emitting diode (OLED) devices, switchable lasers, and optical
memory devices [65].
References
1. Maeda H, Bando Y, Shimomura K, Yamada I, Naito M, Nobusawa K, Tsumatori H, Kawai T
(2011) Chemical-stimuli-controllable circularly polarized luminescence from anion-responsive
π-conjugated molecules. J Am Chem Soc 133:9266–9269
2. Saleh N, Moore B, Srebro M, Vanthuyne N, Toupet L, Williams JA, Roussel C, Deol KK,
Muller G, Autschbach J, Crassous J (2015) Acid/base-triggered switching of circularly polarized luminescence and electronic circular dichroism in organic and organometallic helicenes.
Chem Eur J 21:1673–1681
3. Amako T, Nakabayashi K, Mori T, Inoue Y, Fujiki M, Imai Y (2014) Sign inversion of
circularly polarized luminescence by geometry manipulation of four naphthalene units introduced into a tartaric acid scaffold. Chem Commun 50:12836–12839
192
T. Nakashima and T. Kawai