11.1 Introduction
Chiroptical materials with circularly polarized luminescence (CPL) activity have
been drawing extensive attentions owing to their potential applications in the
fields of photoelectric devices [1–3], 3D displays [4], security systems [5], chiral
sensing [6–8], asymmetric catalysis [9–13], and so on. In order to get the CPL, it
is generally necessary that both the chirality and luminescent chromophore are
integrated in one molecule. Thus, various molecules possessing such elements
are developed and some typical molecules exhibiting CPL are shown in Fig. 11.1.
It is seen that organic molecules with different kinds of molecular chirality,
i.e., point chirality, axial chirality, and planar and helical chirality, can be designed
as CPL-active molecules [14–17]. So far, a large number of the organic molecules
have been reported to show CPL. In those molecules, the dissymmetry factor
defined as g lum ¼ 2 Â (I L À I R )/(I L + I R ), where I L and I R are the intensity of lefthanded and right-handed circularly polarized light, respectively, is in the range of
10
À5 to 10
À3 . Since most of these molecules have been discussed in other chapters,
we will not discuss them in detail here.
Among various organic molecules, low-molecular-weight gelator (LMWG) or
simply gelator is a unique kind of molecules. The gelator molecules can selfassemble into nanostructures via noncovalent bonds and immobilize certain organic
solvents (organogels) or water (hydrogels), as shown in Fig. 11.2. Interestingly,
many of the gelator molecules are chiral and some of them show CPL. These gelator
molecules have two states, i.e., an isolated molecular state in dilute solution and an
assembly state in gels. Interestingly, many of the assembly states showed more
intense CPL than that of their isolated molecular state. One of the important
directions of CPL research is for materials. Since many materials are in solid or
gel state, the research on the CPL of aggregation molecules cannot be avoided.
Herein, recent progress in the CPL of the gelator molecules, from isolated molecules
to their assembly state, will be discussed.
Fig. 11.1 Some typical CPL emitters integrated the chirality and luminescence chromophores.
In the case of point chirality, one of the substituent groups is fluorophore
250
T. Zhao et al.
Chiroptical materials with circularly polarized luminescence (CPL) activity have
been drawing extensive attentions owing to their potential applications in the
fields of photoelectric devices [1–3], 3D displays [4], security systems [5], chiral
sensing [6–8], asymmetric catalysis [9–13], and so on. In order to get the CPL, it
is generally necessary that both the chirality and luminescent chromophore are
integrated in one molecule. Thus, various molecules possessing such elements
are developed and some typical molecules exhibiting CPL are shown in Fig. 11.1.
It is seen that organic molecules with different kinds of molecular chirality,
i.e., point chirality, axial chirality, and planar and helical chirality, can be designed
as CPL-active molecules [14–17]. So far, a large number of the organic molecules
have been reported to show CPL. In those molecules, the dissymmetry factor
defined as g lum ¼ 2 Â (I L À I R )/(I L + I R ), where I L and I R are the intensity of lefthanded and right-handed circularly polarized light, respectively, is in the range of
10
À5 to 10
À3 . Since most of these molecules have been discussed in other chapters,
we will not discuss them in detail here.
Among various organic molecules, low-molecular-weight gelator (LMWG) or
simply gelator is a unique kind of molecules. The gelator molecules can selfassemble into nanostructures via noncovalent bonds and immobilize certain organic
solvents (organogels) or water (hydrogels), as shown in Fig. 11.2. Interestingly,
many of the gelator molecules are chiral and some of them show CPL. These gelator
molecules have two states, i.e., an isolated molecular state in dilute solution and an
assembly state in gels. Interestingly, many of the assembly states showed more
intense CPL than that of their isolated molecular state. One of the important
directions of CPL research is for materials. Since many materials are in solid or
gel state, the research on the CPL of aggregation molecules cannot be avoided.
Herein, recent progress in the CPL of the gelator molecules, from isolated molecules
to their assembly state, will be discussed.
Fig. 11.1 Some typical CPL emitters integrated the chirality and luminescence chromophores.
In the case of point chirality, one of the substituent groups is fluorophore
250
T. Zhao et al.