Dendrimer effects on intermolecular energy-transfer of photoexcited triplet states of dendritic multiporphyrin arrays and electron transfer vs fullerene[60]

Hongxia Luo, Myung Seok Choi, Yasuyuki Araki, Osamu Ito, Takuzo Aida

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Photochemical and photophysical properties of the triplet excited states of dendritic multiporphyrins arrays (nPZn, n = 1, 3, and 7) have been investigated by measuring the nanosecond transient absorption spectra in the visible and near-IR regions with changing the generation number. Intermolecular triplet-triplet annihilation rates decrease with the dendrimer generation, which was interpreted on a proposed kinetic model assuming that the excited triplet energy almost localizes in one PZn unit in nPZn. In the presence of C60, intermolecular electron-transfer takes place via the excited triplet states of nPZn (3nPZn*), yielding the cation radical of nPZn (nPZn.+) and the anion radical of C60 (C60.-) in PhCN. Deceleration of the electron-transfer rate-constants from 1Pzn to 3PZn and the acceleration from 3PZn to 7PZn were observed, in which the latter tendency was interpreted by considering an increase in effective encounter radius for 37PZn*. The observed small change of the rate constants for back electron transfer between the oppositely charged species with the dendrimer generation was also reasonably interpreted by taking a smaller effective radius due to electrostatic attraction into consideration. Dendrimer generation effect was also observed for the intermolecular hole-transfer process.

Original languageEnglish
Pages (from-to)405-412
Number of pages8
JournalBulletin of the Chemical Society of Japan
Volume78
Issue number3
DOIs
Publication statusPublished - 2005 Mar 15

ASJC Scopus subject areas

  • Chemistry(all)

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