Running Off Together

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Science  28 Nov 2008:
Vol. 322, Issue 5906, pp. 1305
DOI: 10.1126/science.322.5906.1305b

Surface diffusion of large organic molecules on atomically flat metal surfaces can exhibit direction anisotropy. Eichberger et al. show how this process can be further influenced by the interactions that result between the molecules during collisions. They used fast scanning tunneling microscopy to study the diffusion of tetrapyridylporphyrin on a Cu(111) surface between 300 and 360 K, which occurs via one-dimensional random walks. They observed an unusual increase in the jump length of dimers formed when the molecules collide with the pyridyl groups aligned parallel to one another, and an increase of more than two orders of magnitude in the diffusion rate. They suggest that the dimers form through coordination to a thermally generated copper atom from the surface; the bonding of the pyridyl group in this manner would weaken the interaction of the subunits with the surface relative to the free monomers. — PDS

Nano Lett. 8, 10.1021/nl802995u (2008).

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