Getting a Leg Up

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Science  03 Aug 2007:
Vol. 317, Issue 5838, pp. 572
DOI: 10.1126/science.317.5838.572c

The reversible cis/trans isomerization of azobenzene and its derivatives, induced by alternating irradiation with ultraviolet and visible light, can be used for on-demand control of properties ranging from large-area hydrophobicity (by variation of surface-exposed groups) to the opening and closing of ion channels on the nanoscale. However, adsorption on metal surfaces tends to impede the isomerization process, in all likelihood through electronic effects or induced changes in the molecule's optical absorption spectrum. Comstock et al. show that if the phenyl rings in azobenzene are derivatized with four bulky tert-butyl groups, the molecule in the planar trans configuration is lifted far enough off a gold surface for irradiation with ultraviolet light to induce photoisomerization. The addition of only two tert-butyl “legs” proved insufficient. The reversible isomerization was monitored with scanning tunneling microscopy. — PDS

Phys. Rev. Lett. 99, 038301 (2007).

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