Macromolecular semiconductors designed based on the higher-order structure and intramolecular potential gradient

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Dendrimers having a zinc porphyrin core and naphthalenediimide termini were examined. The charge-recombination reaction attenuated from 3.1×10^6(s^<-1>) to 0.45×10^6(s^<-1>) with the generation number increase from 1 to 4. In contrast, the charge-separation reaction unexpectedly increased from 0.2×10^9 (s^<-1>) to 0.45×10^9 (s^<-1>). These results are explained as the result of mediated electron transfer through the π-bonds with a potential down gradient.To determine the effect of the potential gradient, phenylenevinylene dendrimers with no gradient were also studied. A DFT (B3LYP/6-31G) calculation showed an electron gradient only induced in the phenylazomethine dendrimer, which has heteroatoms (nitrogen) and rigid-π-conjugating backbones. The phenylazomethine dendrimer showed an asymmetric character of the electro transfer, In contrast, the phenylenevinylene dendrimer did not show such character in their electron transfer reactions.