to exhibit CPL with the luminescence of the metal center [1]. In the same manner,
chiral organic dyes such as helicenes also exhibit CPL [3]. In the field of polymers,
chiral polymers are reported as CPL-active materials [5–7]. The alternative
way to achieve CPL-active organic compounds is the chiral arrangement of
achiral luminophores. If two or more luminophores take a chiral orientation,
the luminophores chirally interact each other. Then, the electronic state of the
luminophore is chirally perturbed. Thus, the emission of the luminophore gets
circularly polarized despite the luminophore being achiral. Such chiral orientation
can be constructed through a covalently linked chiral spacer. Another way to achieve
chiral orientation of achiral luminophores is the use of a chiral supramolecular
assembly. In this chapter, CPL properties of small organic compounds and their
supramolecular assemblies are described (Fig. 9.1).
9.2 CPL of Chiral Organic Luminophores
The early CPL of organic compounds was produced by fluorescence based on
the πÃ!n transition of the carbonyl group of chiral ketones (Fig. 9.2) [4, 8–11].
However, the πà ! n transition of the carbonyl group is weak and limited at short
Fig. 9.1 CPL-active organic compounds: (a) chiral luminophore, (b) chirally arranged achiral
luminophore, and (c) supramolecular helical assembly
H
H
O
O
O
O
O
O
O
O
Fig. 9.2 CPL-active chiral ketones
198
T. Ikeda and T. Haino
chiral organic dyes such as helicenes also exhibit CPL [3]. In the field of polymers,
chiral polymers are reported as CPL-active materials [5–7]. The alternative
way to achieve CPL-active organic compounds is the chiral arrangement of
achiral luminophores. If two or more luminophores take a chiral orientation,
the luminophores chirally interact each other. Then, the electronic state of the
luminophore is chirally perturbed. Thus, the emission of the luminophore gets
circularly polarized despite the luminophore being achiral. Such chiral orientation
can be constructed through a covalently linked chiral spacer. Another way to achieve
chiral orientation of achiral luminophores is the use of a chiral supramolecular
assembly. In this chapter, CPL properties of small organic compounds and their
supramolecular assemblies are described (Fig. 9.1).
9.2 CPL of Chiral Organic Luminophores
The early CPL of organic compounds was produced by fluorescence based on
the πÃ!n transition of the carbonyl group of chiral ketones (Fig. 9.2) [4, 8–11].
However, the πà ! n transition of the carbonyl group is weak and limited at short
Fig. 9.1 CPL-active organic compounds: (a) chiral luminophore, (b) chirally arranged achiral
luminophore, and (c) supramolecular helical assembly
H
H
O
O
O
O
O
O
O
O
Fig. 9.2 CPL-active chiral ketones
198
T. Ikeda and T. Haino