We have systematically investigated the chiroptical behaviors of chiral molecules
of various categories, including point, axial [9–13], planar [14–17], and helical
chirality [18–22]. Recently, more sophisticated Möbius chirality of expanded porphyrins [23] and bowl-shaped chirality of corannulenes [24], as well as supramolecular chirality of host-guest systems [25, 26], nanotubes [27], and nanorings [28],
have been studied (Fig. 7.2). Small chiral molecules with structural rigidity are rather
straightforward in preparation and subsequent property analyses, but they generally
lack the conformational flexibility or dynamism as well as the handle or functionality
for manipulating their chiroptical properties. In contrast, flexible chiral molecules are
furnished with the dynamic chiroptical responses manipulatable through adequate
㻾 㻾 㼛 㼠㼍 㼠㼕㼛 㼚 㻌 㻵㼚 㼢 㼑㼞 㼠㼑㼐
㻱㼚 㼍 㼚 㼠㼕㼛 㼙 㼑㼞 㼕㼏 㻿 㼠㼞 㼡 㼏㼠㼡 㼞 㼑
Fig. 7.1 Schematic illustrations of the thrust direction changes by inverting the rotating direction
(the left pair) or by using the enantiomeric propeller (the right pair)
R
R
R
R
R
R
N
N
P N
N
H
N
NH
O
Ar
Ar
Ar
Ar
Ar
Ar'
Cl
Cl
Cl
Cl
Cl
Cl
Cl
OMe
MeO
NC
CN
axial chirality
planar
chirality
helical chirality
propeller chirality
Möbius chirality
chiral nanotube
supramolecular chirality
Fig. 7.2 Exemplars of common and less common categories of (supra)molecular chirality
152
T. Mori