Energy transfer dynamics in wire-type dendrimers having oligophenylene peripheries

概要

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Energy transfer and shielding effect are studied in wire-type dendrimers (GnPPV: n-thgeneration dendrimer with poly(p-phenylenevinylene) backbone; n = 1, 2) havingoligophenylene light-harvesting (LH) antenna. Following the excitation of the LH-antennae,backbone-polymers in GnPPV give rise to intense photoluminescence (PL) bands. This isdue to the presence of highly efficient energy transfer from the LH-antennae to thebackbone-polymers. The intensity of backbone-PL increases faster than the decay of theantenna-PL. This result indicates that rapid energy-transfer from antenna to backbone takesplace utilizing the overlap of wavefunctions in the excited states. In G2PPV having largerLH-antenna, shielding effect against inter-backbone interactions is recognized moreeffectively than G1PPV. In solid films of GnPPV, red shifts of the backbone-PL bands areobserved. This is caused by inter-backbone interactions of the wire-type dendrimers due toaggregation. The extent of the red shift in G2PPV is smaller than that of G1PPV. Thisresult suggests that the larger LH-antenna in G2PPV substantially wraps itsbackbone-polymer and shields the inter-backbone interactions.