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Science  22 Sep 2006:
Vol. 313, Issue 5794, pp. 1704
DOI: 10.1126/science.313.5794.1704c

The miniaturization of electronic devices to the nanometer scale requires the fabrication of extremely narrow wires. One approach has focused on the synthesis of conducting metal or carbon nanotubes. A second approach is the self-assembly of small molecular components into conduits held together by noncovalent interactions. Stacked aromatic molecules such as tetrathiafulvalene (TTF) could potentially achieve this function. However, when adsorbed on graphite, the highly conjugated TTF molecule interacts strongly with the substrate and lies flat, which minimizes interactions between molecules; hence, the stack motif is unstable. Puigmartí-Luis et al. have derivatized TTF by capping two of the terminal sulfur atoms with amide groups, which are in turn bonded to long alkyl chains. The intermolecular hydrogen-bonding interactions between the amides allow the TTF moieties to form long one-dimensional chains in which the π electron-rich cores are tilted at a high angle to the surface. Scanning tunneling microscopy revealed that parallel wires are formed, spaced ∼5 nm apart, which is consistent with distances predicted by molecular modeling. Both quantum mechanical calculations and scanning tunneling spectroscopy suggest that the nanowires should be highly conducting. Furthermore, rectifying behavior was observed in the -1- to 1-V range, with a 10-fold increase in current at negative versus positive substrate bias. — PDS

J. Am. Chem. Soc. 128, 10.1021/ja0640288 (2006).

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