title: Photoresponsive SAMs on gold fabricated from azobenzene-functionalised asparagusic acid derivatives.
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.
authors.affiliation: Institute of Chemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel, Germany. siemeling@uni-kassel.de
authors.forename: Ulrich
authors.initials: U
authors.lastname: Siemeling
authors.forename: Clemens
authors.initials: C
authors.lastname: Bruhn
authors.forename: Frauke
authors.initials: F
authors.lastname: Bretthauer
authors.forename: Marta
authors.initials: M
authors.lastname: Borg
authors.forename: Frank
authors.initials: F
authors.lastname: Träger
authors.forename: Florian
authors.initials: F
authors.lastname: Vogel
authors.forename: Waleed
authors.initials: W
authors.lastname: Azzam
authors.forename: Mihaela
authors.initials: M
authors.lastname: Badin
authors.forename: Thomas
authors.initials: T
authors.lastname: Strunskus
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
mesh_terms: D001391:Azo Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006046:Gold / Q000737:chemistry*; D008567:Membranes, Artificial; D008958:Models, Molecular; D015394:Molecular Structure; D010777:Photochemistry; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D008567:Membranes, Artificial; D013876:Thiophenes; C010035:1,2-dithiolane-4-carboxylic acid; D006046:Gold; C009850:azobenzene