Electrical conduction through molecules depends critically on the delocalization of the molecular electronic orbitals and their connection to the metallic contacts. Thiolated (- SH) conjugated organic molecules are therefore considered good candidates for molecular conductors: in such molecules, the orbitals are delocalized throughout the molecular backbone, with substantial weight on the sulphur-metal bonds. However, their relatively small size, typically approximately 1 nm, calls for innovative approaches to realize a functioning single-molecule device. Here we report an approach for contacting a single molecule, and use it to study the effect of localizing groups within a conjugated molecule on the electrical conduction. Our method is based on synthesizing a dimer structure, consisting of two colloidal gold particles connected by a dithiolated short organic molecule, and electrostatically trapping it between two metal electrodes. We study the electrical conduction through three short organic molecules: 4,4'-biphenyldithiol (BPD), a fully conjugated molecule; bis-(4-mercaptophenyl)-ether (BPE), in which the conjugation is broken at the centre by an oxygen atom; and 1,4-benzenedimethanethiol (BDMT), in which the conjugation is broken near the contacts by a methylene group. We find that the oxygen in BPE and the methylene groups in BDMT both suppress the electrical conduction relative to that in BPD.

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Nature 413, 716-718 (2001) In this Letter, there was a mistake in the presentation of the synthesis conditions of the reported samples. The actual range of the temperatures of synthesis for the four rhombohedral samples was 975-1,025 K. One of the five reported samples was wrongly characterized in relation to the polymerization type: the sample was actually prepared at 2.5 GPa (synthesis temperature, 1,125 K), representing a mixture of the rhombohedral and tetragonal phases with some hard carbon. The error in characterization of this sample weakens our attribution of the ferromagnetism to defects in the rhombohedral phase (Rh-C 60 ) but does not influence our main conclusion concerning the observation of magnetism in a carbon solid based on polymerized fullerenes, although its origin and the actual magnitude remain an open question. Also, we were unaware of earlier work on magnetism in polymerized fullerenes 1 , that should have been cited. T.L.M. takes full responsibility for the misidentification of the sample preparation conditions. We thank A. V. Talyzin for alerting us to this mistake. 432, 610-614 (2004) The description of the method used for the calculation of the fraction attributable risk (FAR) shown in Fig. 4b is incorrect. The corresponding sentence in the Methods section should read "For the red curve, the response to anthropogenic forcing is also included, and a normal distribution is used to estimate the chance of exceeding the 1.6 K threshold." 677-680 (2005) In Fig. 4a of this Letter, in which the spectra of two BPD dimmers are compared, the scaling on the two y axes should have been shifted relative to one another in order to illustrate the point made in the text. The corrected Fig. 4a is shown here.