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Issue 29, 2009
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Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy

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Abstract

Sum-frequency generation (SFG) vibrational spectroscopy is employed to investigate the reversible, photoinduced trans/cis isomerization of an azobenzene-functionalized self-assembled monolayer (SAM) on a gold substrate. A C[triple bond, length as m-dash]N marker group at the outer phenyl ring is used as a direct measure of the switching state. The azobenzene unit is connected to the surface by a tripodal linker system with an adamantane core, which results in both a sufficient decoupling of the functional azobenzene unit from the metallic substrate and a free volume to prevent steric hindrance, thus allowing the isomerization process. Optical excitation at 405 nm induces the transcis isomerization, whereas light exposure at 470 nm leads to the back reaction. The effective cross sections for the reactions are σeff(cis) = 4 ± 1 × 10−18 cm2 at 405 nm (transcis) and σeff(trans) = 2.5 ± 0.9 × 10−19 cm2 at 470 nm (cistrans). We propose that the photoisomerization is driven by a direct (intramolecular) electronic excitation of the azobenzene conjugate, analogous to the free molecules in solution.

Graphical abstract: Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy

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Publication details

The article was received on 06 Jan 2009, accepted on 08 Apr 2009 and first published on 20 May 2009


Article type: Paper
DOI: 10.1039/B823330F
Citation: Phys. Chem. Chem. Phys., 2009,11, 6242-6248

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    Reversible photoisomerization of an azobenzene-functionalized self-assembled monolayer probed by sum-frequency generation vibrational spectroscopy

    S. Wagner, F. Leyssner, C. Kördel, S. Zarwell, R. Schmidt, M. Weinelt, K. Rück-Braun, M. Wolf and P. Tegeder, Phys. Chem. Chem. Phys., 2009, 11, 6242
    DOI: 10.1039/B823330F

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