p-Phenyleneethynylene molecular wires: influence of structure on photoinduced electron-transfer properties.
A series of donor-acceptor arrays (exTTF-oPPE-C60) containing pi-conjugated oligo(phenyleneethynylene) wires (oPPE) of different length between pi-extended tetrathiafulvalene (exTTF) as electron donor and fullerene (C60) as electron acceptor has been prepared by following a convergent synthesis. The key reaction in these approaches is the bromo-iodo selectivity of the Hagihara-Sonogashira reaction and the deprotecting of acetylenes with different silyl groups to afford the corresponding donor-acceptor conjugates in moderate yields. The electronic interactions between the three electroactive species were determined by using UV-visible spectroscopy and cyclic voltammetry. Our studies clearly confirm that, although the C60 units are connected to the exTTF donor through pi-conjugated oPPE frameworks, no significant electronic interactions are observed in the ground state. Theoretical calculations predict how a simple exchange from C=C double bonds (i.e., oligo(p-phenylenevinylene) to C triple chemical bond C triple bonds (i.e., oPPE) in the electron donor-acceptor conjugates considerably alters long-range electron transfer. Photoexcitation of exTTF-oPPE-C60 leads to the following features: a transient photoproduct with maxima at 660 and 1000 nm, which are unambiguously attributed to the photolytically generated radical-ion-pair state, [exTTF*+-oPPE-C60*]. Both charge-separation and charge-recombination processes give rise to a molecular-wire behaviour of the oPPE moiety with an attenuation factor (beta) of (0.2+/-0.05) A(-1).
Department of Chemistry and Pharmacy, Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse 3, Erlangen, Germany.
Mateusz
M
Wielopolski
Carmen
C
Atienza
Timothy
T
Clark
Dirk M
DM
Guldi
Nazario
N
Martín
D000042:Absorption; D000480:Alkynes / Q000737:chemistry*; D001555:Benzene Derivatives / Q000737:chemistry*; D002384:Catalysis; D004563:Electrochemistry; D004579:Electron Transport; D004583:Electrons; D037741:Fullerenes / Q000737:chemistry; D053770:Nanowires / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D010777:Photochemistry; D011789:Quantum Theory; D013050:Spectrometry, Fluorescence
D000480:Alkynes; D001555:Benzene Derivatives; D037741:Fullerenes; D010165:Palladium; C069837:fullerene C60