1. Department of Chemistry and
2. Department of Physics, University of California at Berkeley and
3. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
4. Present address: Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, USA.

Correspondence to: Paul L. McEuen^2,3 Correspondence and requests for materials should be addressed to P.M. (e-mail: Email: mceuen@socrates.berkeley.edu).

The motion of electrons through quantum dots is strongly modified by single-electron charging and the quantization of energy levels^{1, 2}. Much effort has been directed towards extending studies of electron transport to chemical nanostructures, including molecules^{3, 4, 5, 6, 7, 8}, nanocrystals^{9, 10, 11, 12, 13} and nanotubes^{14, 15, 16, 17}. Here we report the fabrication of single-molecule transistors based on individual C₆₀ molecules connected to gold electrodes. We perform transport measurements that provide evidence for a coupling between the centre-of-mass motion of the C₆₀ molecules and single-electron hopping¹⁸—a conduction mechanism that has not been observed previously in quantum dot studies. The coupling is manifest as quantized nano-mechanical oscillations of the C₆₀ molecule against the gold surface, with a frequency of about 1.2 THz. This value is in good agreement with a simple theoretical estimate based on van der Waals and electrostatic interactions between C ₆₀ molecules and gold electrodes.