title: Photoinduced Electron Transfer and Hole Migration in Nanosized Helical Aromatic Oligoamide Foldamers.
abstract: A series of photoactive triads have been synthesized and investigated in order to elucidate photoinduced electron transfer and hole migration mechanism across nanosized, rigid helical foldamers. The triads are comprised of a central helical oligoamide foldamer bridge with 9, 14, 18, 19, or 34 8-amino-2-quinolinecarboxylic acid repeat units, and of two chromophores, an N-terminal oligo(para-phenylenevinylene) electron donor and a C-terminal perylene bis-imide electron acceptor. Time-resolved fluorescence and transient absorption spectroscopic studies showed that, following photoexcitation of the electron acceptor, fast electron transfer occurs initially from the oligoquinoline bridge to the acceptor chromophore on the picosecond time scale. The oligo(para-phenylenevinylene) electron donor is oxidized after a time delay during which the hole migrates across the foldamer from the acceptor to the donor. The charge separated state that is finally generated was found to be remarkably long-lived (>80 μs). While the initial charge injection rate is largely invariant for all foldamer lengths (ca. 60 ps), the subsequent hole transfer to the donor varies from 1 × 109s-1for the longest sequence to 17 × 109s-1for the shortest. In all cases, charge transfer is very fast considering the foldamer length. Detailed analysis of the process in different media and at varying temperatures is consistent with a hopping mechanism of hole transport through the foldamer helix, with individual hops occurring on the subpicosecond time scale (kET= 2.5 × 1012s-1in CH2Cl2). This work demonstrates the possibility of fast long-range hole transfer over 300 Å (through bonds) across a synthetic modular bridge, an achievement that had been previously observed principally with DNA structures.
authors.affiliation: Univ. de Bordeaux , CBMN (UMR 5248), Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.|CNRS, CBMN (UMR 5248) , Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.
authors.forename: Xuesong
authors.initials: X
authors.lastname: Li
authors.affiliation: Univ. de Bordeaux , CBMN (UMR 5248), Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.|CNRS, CBMN (UMR 5248) , Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.
authors.forename: Nagula
authors.initials: N
authors.lastname: Markandeya
authors.affiliation: Univ. de Bordeaux , Laboratoire Ondes et Matières d'Aquitaine (UMR5798), 351 cours de la Libération, 33405 Talence cedex, France.
authors.forename: Gediminas
authors.initials: G
authors.lastname: Jonusauskas
authors.affiliation: Univ. de Bordeaux , Institut des Sciences Moléculaires (UMR5255), 351 cours de la Libération, 33405 Talence cedex, France.
authors.forename: Nathan D
authors.initials: ND
authors.lastname: McClenaghan
authors.affiliation: CNRS, CBMN (UMR 5248) , Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.
authors.forename: Victor
authors.initials: V
authors.lastname: Maurizot
authors.affiliation: Univ. de Bordeaux , Institut des Sciences Moléculaires (UMR5255), 351 cours de la Libération, 33405 Talence cedex, France.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Denisov
authors.affiliation: CNRS, CBMN (UMR 5248) , Institut Européen de Chimie et Biologie, 2 rue Robert Escarpit, 33600 Pessac, France.
authors.forename: Ivan
authors.initials: I
authors.lastname: Huc