Testing Molecular Wires: A Photophysical and Quantum Chemical Assay

One of the major challenges in current chemistry is to ?nd molecules able to move charges rapidly and ef?ciently from, for example, one terminus to another one under the control of an external electrical, electrochemical or photochemical stimulus. Nature has provided impressive examples of how these goals are achieved. The photosynthetic reaction center protein, for instance, rapidly moves electrons with near unity quantum ef?ciency across a lipid bilayer membrane using several redox cofactors, and thus, serves as a model for developing biomimetic analogues for applications in ?elds such as photovoltaic devices, molecular electronics and photonic materials. In this context, p-conjugated oligomeric molecular assemblies are of particular interest because they provide ef?cient electronic couplings between electroactive units - donor and acceptor termini - and display wire-like behavior. In order to make a molecule able to behave as an ideal molecular wire different requirements need to be ful?lled: i) matching between the donor (acceptor) and bridge energy levels, ii) a good electronic coupling between the electron donor and acceptor units via the bridge orbitals, and iii) a small attenuation factor. Among the many different p-conjugated oligomers, oligo(p-phenylenevin- enes) (oPPV), have emerged as a particularly promising model system that helps to comprehend/rationalize the basic features of polymeric poly(p-phenyle- vinylenes) and also as a versatile building block for novel materials with che- cally tailored properties.