Probing molecular wires:: Synthesis, structural, and electronic study of donor-acceptor assemblies exhibiting long-range electron transfer

被引:99
作者
Giacalone, F
Segura, JL
Martín, N
Ramey, J
Guldi, DM
机构
[1] Univ Complutense Madrid, Fac Ciencias Quim, Dept Quim Organ, E-28040 Madrid, Spain
[2] Univ Erlangen Nurnberg, Inst Phys & Theoret Chem, D-91058 Erlangen, Germany
关键词
donor-acceptor systems; electron transfer; fullerenes; nanostructures; oligo(phenylenevinylene);
D O I
10.1002/chem.200500073
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
A series of donor-acceptor arrays (C-60-oligo-PPV-exTTF; 16-20) incorporating pi-conjugated oligo(phenylenevinylene) wires (oligo-PPV) of different length between pi-extended tetrathiafulvalene (exTTF) as electron donor and C-60 as electron acceptor has been prepared by multistep convergent synthetic approaches. The electronic interactions between the three electroactive species present in 16-20 were investigated by UV-visible spectroscopy and cyclic voltammetry (CV). Our studies clearly show that, although the C-60 units are connected to the exTTF donors through a pi-conjugated oligo-PPV framework, no significant electronic interactions are observed in the ground state. Interestingly, photoinduced electron-transfer processes over distances of up to 50 A afford highly stabilized radical ion pairs. The measured lifetimes for the photogenerated charge-separated states are in the range of hundreds of nanoseconds (similar to 500 ns) in benzonitrile, regardless of the oligomer length (i.e., from the monomer to the pentamer). A different lifetime (4.35 Vs) is observed for the heptamer-containing array. This difference in lifetime has been accounted for by the loss of planarity of the oPPV moiety that increases with the wire length, as established by semi-empirical (PM3) theoretical calculations carried out with 19 and 20. The charge recombination dynamics reveal a very low attenuation factor (beta = 0.01 +/- 0.005 angstrom(-1)). This value, as well as the strong electron coupling (V similar to 5.5cm(-1)) between the donor and the acceptor units, clearly reveals a nanowire behavior for the pi-conjugated oligomer, which paves the way for applications in nanotechnology.
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页码:4819 / 4834
页数:16
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