Controlling the vectorial transport of energy and electrons in organized molecular assemblies has been of current interest due to the potential applications of these architectures in artificial photosynthesis, photovoltaic cells, materials for optical data storage, thin-film transistors, and electroluminescent materials. The required functional group organizations have been approached using linear arrays of porphyrins and diimides or other molecular assemblies such as liquid crystals, zeolites, polymers, peptides, and amphiphiles. The unique architecture of dendrimers provides a new dimension for the precise placement of charge-transport units in a single molecule. Since dendrimers are highly branched macromolecules, they offer control over the placement of functional groups in higher dimensions than that offered by linear arrays.

Dendrimers should also be advantageous for the funneling of charges from the core to the periphery, because the number of functional units doubles with each layer. Several photophysical studies based on dendriticarchitectures have been reported over the past few years. However, in most of these cases, the light harvesting functional groups are incorporated as the core unit or as the peripheral units, perhaps largely due to the high synthetic facility with which these arrays can be obtained. To exploit all the architectural features offered by dendrimers, it is advantageous to build them where these functional groups are incorporated as the repeating units.

The system that provides fast charge separation but slow charge recombination would be ideal for electron transfer materials. Recently, we have found that meta-conjuagated polyacetylene (PA) can meet these requirements. Based on time-resolved measurements, we have showed that para- and meta-conjugated PA have similar forward but very different backward electron transfer. The explanation for these differences could be originated from the fact that meta linkage blocks electronic communication in the ground state but acts like a wire in the excited state. As a result, the forward electron transfer in meta PA is comparable to that in para PA while the backward electron transfer undergo with much slower rate.

Currently, to construct novel efficient electron transfer compounds, we have been putting an effort to combine advantages provided by both dendrimers and meta-linked molecules. Dendrimers containing meta-conjugated PA are considered promising for efficient electron transfer and now under our interest.