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60
60
P, P
PP
20
0
-20
M,M
-60
270
320
370
420
470
520
λ
/ nm
Figure 6.21 CD (top) and part of CPL (bottom) spectra of
P,P
- and
M,M
-[EuCr(L25)
3
]
6þ
1mM
in acetonitrile at room temperature.
Redrawn with permission from [119]. Copyright 2004
American Chemical Society.
Scheme 6.8 Pinene-derivatized chiral ligands.
Dissymmetry factors for the Eu(
þ
)andTb(
þ
) species have been determined for several
0.088 for
5
D
0
!
7
F
1
and
0.081 for
5
D
4
!
7
F
5
.
transitions; for instance,
g
lum
¼
6.5 Extended Helical Structures
Numerous examples of lanthanoid [124-128] or lanthanoid-transition metal [129-131]
coordination polymers featuring helical one-, two- or three-dimensional chains and/or
channels [132] have been engineered with the aim of getting unusual luminescent or mag-
netic properties [38]. Their description is beyond the scope of the present chapter, so we
shall only mention one example in which a dinuclear helicate has been assembled into a
one-dimensional coordination polymer. When ligand H
2
L2b (Scheme 6.1) is reacted with
Ln
III
ions in the presence of a monodentate ancillary ligand such as water, dimethylforma-
mide or triphenylphosphine oxide, molecular helicates are obtained. However, when
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