Porphyrin-based molecular wire

Figure 11. 32 A fully conjugated porphyrin-based molecular wire.48...

Finally, a DEER study on models for molecular wires made from butadiyne-linked zinc porphyrin oligomers, end-labeled with nitroxide radicals, was performed by Lovett, Anderson, and coworkers [107]. Unlike in [104—106], one can control the conformations of these metalloporphyrin-based strucmres by self-assembly with multidentate amine ligands, which bend the rigid oligomeric structure. The experimentally found end-to-end distances in these complexes match the predictions from molecular dynamics calculations. This study thus presents a proof-of-principle that DEER spectroscopy is also well suited for understanding more complex supramolecular stmctures. 

The construction of intramolecular molecular system whose photo active molecule linked with conducting molecular wire is an important subject in realization of. molecular electronic or photonic devices. For such objectives, systematization of donor-photosensitizer-acceptor triad molecules into large molecular systems is one of the feasible approaches because the exquisite incorporation of the photosensitizer and a suitable electron donor and/or acceptor into a conducting polymeric chain is useful for various molecular systems based on the photoinduced electron transfer. With this in mind, we synthesized symmetrical donor-acceptor-donor triad molecules which can be polymerized by the normal electrochemical oxidation. By the polymerization, one-dimensional donor-acceptor polymers with porphyrin moieties separated by ordered oligothienyl molecular wire which is considered as a proto-type molecular device was obtained. 

For the attainment of marvelous electron transfer processes in the natural sequential potential fields, many noncovalentaly-bound donor-acceptor (DA) systems and covalently-bound DA systems " " have been previously reported. Most of them are artificial models of the photosynthesis comprising simple assemblies of the dyad (DA) or triad [donor-spacer-acceptor (DSA)] functional molecules with a chromophore such as a porphyrin. The quantum efficiency of such systems is lower (<25%) compared with the biological systems (=100%), and thus more efforts for constructing more efficient systems are necessary. Some of the covalen-taly-bound DA systems have been designed for the fabrication of molecule-scale devices based on a molecular electron-transport wire and/or highly ordered molecular arrays on the surface. " Most of such studies employed the DA nonconju-gated molecules. 

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