Photoresponsive SAMs on gold fabricated from azobenzene-functionalised asparagusic acid derivatives

Dalton Trans. 2009 Oct 28:(40):8593-604. doi: 10.1039/b905025f. Epub 2009 Aug 18.

Abstract

We have prepared a range of azobenzene derivatives equipped with an asparagusic acid-based 1,2-dithiolane headgroup suitable for chemisorption on solid gold substrates. The formation of self-assembled monolayers (SAMs) of the amide cyclo-S2C3H5-4-C(O)NH-p-C6H4-N=N-Ph (1) and the ester cyclo-S2C3H5-4-C(O)O-p-C6H4-N=N-Ph (2) on gold was monitored in situ and in real time by optical second harmonic generation (SHG). The structure and composition of these SAMs was investigated by a range of ex situ methods, viz. ellipsometry, X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and Fourier transform infrared reflection absorption spectroscopy (FTIRRAS). Reversible, but moderate, photoswitchability was observed for these one-component SAMs by ellipsometry and dynamic contact angle measurements. Use of a second 1,2-dithiolane component for lateral dilution of the photoactive terminal groups resulted in a much more pronounced photoresponse.

MeSH terms

  • Azo Compounds / chemical synthesis
  • Azo Compounds / chemistry*
  • Crystallography, X-Ray
  • Gold / chemistry*
  • Membranes, Artificial*
  • Models, Molecular
  • Molecular Structure
  • Photochemistry
  • Thiophenes / chemistry*

Substances

  • Azo Compounds
  • Membranes, Artificial
  • Thiophenes
  • 1,2-dithiolane-4-carboxylic acid
  • Gold
  • azobenzene