Control over charge transfer through molecular wires by temperature and chemical structure modifications

M. Wielopolski, C. Van der Pol, L. Brinkhaus, G. De Miguel, G. Katsukis, M. Bryce, Tim Clark, D. Guldi

Research output: Contribution to journalArticlepeer-review


A series of electron donor−acceptor arrays containing π-conjugated oligofluorenes (oFL) of variable length between a zinc porphyrin (ZnP) as electron donor and fullerene (C60) as electron acceptor have been prepared by following a convergent synthesis. The electronic interactions between the electroactive species were determined by cyclic voltammetry, UV−visible, fluorescence, and femto/nanosecond transient absorption spectroscopy. Our studies clearly confirm that, although the C60 units are connected to the ZnP donor through π-conjugated oFL frameworks, no significant electronic interactions prevail in the ground state. Theoretical calculations predict that a long-range electron transfer occurs primarily due to a maximized π-conjugated pathway from the donor to the acceptor. Photoexcitation of ZnP-oFLn-C60 results in transient absorption maxima at 715 and 1010 nm, which are unambiguously attributed to the photolytically generated radical ion pair state, [ZnP•+-oFLn-C60•−], with lifetimes in the microsecond time regime. Temperature-dependent photophysical experiments have shown that the charge-transfer mechanism is controllable by temperature. Both charge separation and charge recombination processes give rise to a molecular wire behavior of the oFL moiety with an attenuation factor (β) of 0.097 Å−1. The correlation β to the connection pattern between the ZnP donor and the oFL linker revealed that even small alterations of the linker π-electron system break the homogeneous π-conjugation pattern, leading to higher values of β.
Original languageEnglish
Pages (from-to)6449-6462
Number of pages14
JournalACS Nano
Issue number11
Publication statusPublished - 2010


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