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coupling. Finally, in most conjugated LH dendrimers, the conjugation length is
sensitive to the dendrimer scaffold. This allows easy tuning of the photophysical
property of the chromophore, but complicates the interpretation of the spectra, on the
other hand.
Below, we review the progress in this field of research with contributions from
several groups, including our own. We do not cover transition metal containing LH
dendrimers [81].
9.3.2 Examples of Shape-Persistent Conjugated Dendrimer as LH
Materials
In 1993, Xu andMoore reported the first shape-persistent conjugated dendrimer, using a
PA scaffold [17]. The synthetic protocol was based primarily on Sonogashira reaction
between aryl
22
(Figure 9.18), with a molecular weight of 14 kDa, represented the largest pure hydro-
carbon at that time. This paper represents the start of the preparation of large dendrimers
that are composed of stiff building blocks and have well-defined conformation.
iodide and terminal alkyne. The fourth-generation dendrimer
FIGURE 9.18
Chemical structure of the fourth-generation PA dendrimer (94 mer) [17].
