Phenylacetylene dendrimer

Methanofullerene 20 with phenylacetylene dendrimer addends has also been reported [45] (Fig. 10). The UV absorption of fullerodendrimer 20 is particularly strong and is mainly attributed to transitions located on the two dendritic branches of the molecule. The photophysical investigations revealed that the large poly(aryl)acetylene branches act as photon antennae [46]. 

Fig. 2. A poly(phenylacetylene) dendrimer with an energy gradient across the conjugation length of the acetylene units from the periphery to the focal point...

Convergent syntheses developed by Moore et al. provided access to rigid higher-generation phenylacetylene dendrimers (Fig. 4.14). Dendrons with peripheral p-tert-butylphenyl units used in initial work showed only limited solubility and were therefore unsuitable for assembly of higher generations. However, minimal modification of the periphery with 3,5-di-tert-butylphenyl groups improves the solubility so dramatically that it even proved possible to prepare a dendri-mer with 94 monomeric units [24]. 

Scheme 5.35. Sequence for the construction of site-specified phenylacetylene dendrimers.

Figure 5.11. Rigid phenylacetylene dendrimers have been employed as molecular antennas for the directional transduction of energy.

Martin et alJ106b have employed low-dose techniques to obtain selected area electron diffraction and high-resolution electron microscopy of these phenylacetylene dendrimer s. 

The chemistry used to prepare phenylacetylene dendrimers is also based on this methodology in view of the multiple conversions, a high-yielding and well-established procedure was required. The dendrimer was prepared in an elegant way by repeating the cross-coupling and deprotection using monomers such as those shown in Scheme 5-5 [58]. 

Figure 1.1. Building blocks of phenylacetylene dendrimers studied by Bardeen and co-workers [8].

Dendrimers consisting of phenylacetylene moieties exist as (i) compact or extended meta-conjugated phenylacetylene (PA) dendrimers [40-54], and (ii) unsymmetrical branched phenylacetylene dendrimers [55-58]. 

Scheme 12 Structures of unsymmetrical phenylacetylene dendrimers 26a-d by Peng and coworkers [55-58]...

Figure 12-4 Abbreviated structures for generations 1-4 of the phenylacetylene dendrimer series Z-Cas-cade benzene[3 -1,3.5] (5-ethynyl-l,3-phenylene)° 5-ethynyl-l,3-di(terr-butyl)benzene.

Effect of Varying Focal Point Functionality on the Convergent Synthesis of Phenylacetylene Dendrimers... 

Scheme 12-3 Method for the preparation of phenylacetylene dendrimers that combines a linear increase in monomer core size per generation with the convergent growth process (SYNDROME strategy). Adapted from [23].

Scheme 12-4 Double exponential growth scheme for phenylacetylene dendrimers. Aj Bp are protected versions of the functional groups A, B.

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