Maintaining Chains

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Science  14 Jan 2005:
Vol. 307, Issue 5707, pp. 182
DOI: 10.1126/science.307.5707.182d

Coupling reactions of organic molecules on surfaces can proceed at modest temperatures. McCarty and Weiss have used low-temperature scanning tunneling microscopy (STM) to observe molecules aligning into chains before such reactions can proceed. At room temperature, diiodobenzene dissociates on the atomically flat Cu(111) surface to create mobile phenylene radicals that can be pinned at defect sites. Images taken at 77 kelvin show that the phenylene species align in noncovalently bonded chains—the STM tip could be used to pull a phenylene monomer out of the chain. At higher surface coverages, a second layer of chains can align on a surface already covered with phenylene chains. Parts of the upper-level chains could be nudged to new locations on the surface, where they would return to their original length by recruiting more monomer units. — PDS

J. Am. Chem. Soc. 126, 16672 (2004).

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