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p ‐Phenyleneethynylene Molecular Wires: Influence of Structure on Photoinduced Electron‐Transfer Properties
Author(s) -
Wielopolski Mateusz,
Atienza Carmen,
Clark Timothy,
Guldi Dirk M.,
Martín Nazario
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200800159
Subject(s) - tetrathiafulvalene , photochemistry , chemistry , conjugated system , photoexcitation , acceptor , electron donor , electron transfer , fullerene , electron acceptor , molecule , excited state , organic chemistry , polymer , atomic physics , physics , catalysis , condensed matter physics
Abstract A series of donor–acceptor arrays (exTTF–oPPE–C 60 ) containing π‐conjugated oligo(phenyleneethynylene) wires (oPPE) of different length between π‐extended tetrathiafulvalene (exTTF) as electron donor and fullerene (C 60 ) 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 C 60 units are connected to the exTTF donor through π‐conjugated oPPE frameworks, no significant electronic interactions are observed in the ground state. Theoretical calculations predict how a simple exchange from CC double bonds (i.e., oligo( p ‐phenylenevinylene) to CC triple bonds (i.e., oPPE) in the electron donor–acceptor conjugates considerably alters long‐range electron transfer. Photoexcitation of exTTF–oPPE–C 60 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–C 60 .− ]. Both charge‐separation and charge‐recombination processes give rise to a molecular‐wire behaviour of the oPPE moiety with an attenuation factor ( β ) of (0.2±0.05) Å −1 .